Exercise Biochemistry Review

PL-001 Home-Based High-Intensity Interval Training Improves Muscle Capillarisation and eNOS/NAD(P)Hoxidase Protein Ratio in Obese Individuals with Elevated Cardiovascular Disease Risk

2021-03-02T16:35:17+00:00

Objective Obesity and inactivity lead to structural and functional muscle microvascular impairments associated with development of chronic disease. This study is the first to investigate the effect of a novel home-based high-intensity interval training (HIT) (Home-HT) intervention in obese individuals with elevated cardiovascular disease (CVD) risk on capillarisation and muscle microvascular eNOS/NAD(P)Hoxidase ratio. Comparisons were made with home-based moderate-intensity continuous training (Home-MICT) and supervised laboratory-based low-volume HIT (Lab-HIT) as control groups.

Methods Thirty-two sedentary obese adults (age 36±2 years; BMI 34.3±0.8 kg∙m^-2; O_2peak24.6±1.0 ml∙kg^-1∙min^-1) were allocated to 12 weeks of Home-HIT (n=9), Home-MICT (n=13) or Lab-HIT (n=10). Muscle biopsies were taken pre- and post-training to assess specifically in the endothelial layer of muscle arterioles and capillaries the protein content of eNOS, serine¹¹⁷⁷phosphorylated eNOS, NOX2 and p47^phox, and various capillarisation measures using quantitative immunofluorescence microscopy.

Results All interventions induced comparable increases in total eNOS content in terminal arterioles and capillaries (P<0.001). There was no change in ser¹¹⁷⁷phosphorylated eNOS (arterioles P=0.802; capillaries P=0.311), but eNOS ser¹¹⁷⁷/eNOS ratio significantly decreased following training in arterioles and capillaries (P<0.001). Training decreased NOX2 content (arterioles P<0.001; capillaries P<0.001), but there was no change in p47^phoxcontent (arterioles P=0.101; capillaries P=0.345). All measures of capillarisation increased (P<0.05). These adaptations occurred alongside increased O_2peak(P<0.001) and whole-body insulin sensitivity (P=0.033). There were no significant differences between training programmes.

Conclusions The training effects of Home-HIT on skeletal muscle microvascular adaptations are comparable to those of traditional training methods, with the advantage that Home-HIT reduces barriers to exercise in obese individuals with elevated CVD risk.

PL-002 AGTR1 polymorphism is associated with elite endurance athletes: A functional study

2021-03-02T16:34:47+00:00

Objective To explore the association between the polymorphism of angiotensin II receptor type 1 gene(AGTR1) and elite endurance athlete performance and the mechanism of how the polymorphism works.

Methods (1) Polymorphism of AGTR1 rs5182 between 122 elite Chinese endurance athletes and 222 controls were analyzed by MALDI-TOF-MS. (2) Aerobic capacity of 79 elite Chinese endurance athletes such as VC/FEV1/MVV/ VO2AT/ HRAT/ VAT/ VO₂max/ HRmax/ VVO₂max were measured and association between rs5182 polymorphism and the performance was analyzed. (3) PcDNA3.1-AGTR1 -T and pcDNA3.1-AGTR1-C plasmid were build and the plasmids was transfected into mammalian 293T cells. mRNA levels were detected after 48 hours. Statistical analysis was performed using SPSS software version 15.0. Values of P < 0.05 were considered statistically significant. Continuous data were expressed as mean ± SD, while categorical data were expressed as frequencies. Genotype distribution and allele frequencies between athletes and control subjects were compared using χ2 tests. Aerobic performance data was analyzed with One-Way ANOVA if it conformed to normal distribution and homogeneity of variance otherwise Non-parametric test of independent sample was used.

Results (1) Genotype frequencies of AGTR1 rs5182 are significant differences between the athletes and control subjects (p = 0.040), the Word-Class athletes and control subjects (p = 0.018), 5km athletes and control subjects (p =0.015), 10km athletes and control subjects (p = 0.026), male athletes and male controls(p=0.045). (2) Association is found between Genotype distribution and MV(L/min) though others not (Genotype: MV; CC: 122.514±6.767; CT:117.187±17.961; TT:119.688±20.226, p=0.047). (3) Transiently transfectedpcDNA3.1-AGTR1-T and pcDNA3.1-AGTR1-C plasmids into 293T cells successfully. The differences of mRNA levels between the groups were not significant (p = 0.991).

Conclusions AGTR1 gene rs5182 could be a candidate genetic mark of selection elite endurance athletes in Han Population from Northern China, but this polymorphism does not affect AT1R protein function through changing its mRNA level.

PL-003 BMSCs transplantation aggravate inflammation, oxidative stress, fibrosis and impair skeletal muscle regeneration

2021-02-28T16:54:00+00:00

Objective Skeletal muscle contusion is one of the most common muscle injury in sports medicine and traumatology. Bone marrow mesenchymal stem cells (BMSCs) transplantation is a promising strategy for muscle regeneration. However, the roles of BMSCs, especially the mechanisms involved, in the regeneration of contused skeletal muscle are still not fully recognized. The aim of the study is to evaluate the potential of BMSCs transplantation for muscle regeneration and mechanisms involved after contusion.

Methods Ninety-nine C57BL/6J mice were divided into three groups: control group (n=11), muscle contusion and BMSCs treated group (n=44), muscle contusion and sham treated group (n=44). BMSCs were immediately transplanted into gastrocnemius muscles (GMs) following direct contusion. At different time points (3, 6, 12 and 24 days) post-injury, the animals were killed and then GMs were harvested. Morphological and gene expression analyses were used to elevate the effect of BMSCs transplantation and mechanisms involved.

Results The results indicate that BMSCs transplantation impairs muscle regeneration, as well as more fibrotic scar formation after skeletal muscle contusion. Furthermore, macrophages, inflammatory cytokines, chemokines, matrix metalloproteinases and oxidative stress related enzymes were significantly increased after BMSCs transplantation. These results suggest that BMSCs transplantation impairs skeletal muscle regeneration and that macrophages, inflammatory cytokines, chemokines, matrix metalloproteinases and oxidative stress related enzymes may be involved in the process.

Conclusions BMSCs transplantation aggravates inflammation, oxidative stress and fibrosis, and impairs skeletal muscle regeneration, which shed new light on the role of BMSCs in regenerative medicine and cautions the application of BMSCs for muscle injury.

PL-004 Research on monitoring power endurance training effect of synchronized swimmers

2021-02-28T16:53:29+00:00

Objective To explore the usage of heart rate and derivative index, such as quick recovery index (QRI) and training impulse (TRIMP), to monitor and evaluate load level at physical training course. With simplified load evaluation program, we can accurately feedback load stress and recovery conditions of the athletes, so as to timely adjust training load and avoid sports fatigue.

Methods Maximum oxygen uptake is tested to determine maximum heart rate of the athletes, which can be used as the basis for monitoring assessment of physical training load. During training phase, monitoring the variation of the relative index of HR and sleeping conditions of 10 athletes by Firstbeat. The test means was High-intensity interval endurance of climbing machine in 7*20s-20s before and after stage training. The main indexes include of QRI/TRIMP/EPOC/BLa\climbing height.

Results It’s shown through monitoring that maximum heart rate of the athletes in the physical training course is up to 200BPM, which prompts high load level during training. Such athletic ability is promoted to satisfy the demands for complex choreography. Characteristics of energy supply for power endurance with high intensity closely agree with physical fitness demand during synchronized swimming competition, which is general performance of strength, speed and endurance. Through comparison of data on testing power endurance of climbing machine in 7*20s-20S before and after training, average climbing height of the athletes is increased from 60.1m/20s to 62.4m/20s with increased range up to 3.8% and blood lactate level is decreased from 10.7mmol/L to 10.5mmol/L in 2 minutes after exercise, which can be regarded as slightly improvement of ability of the athletes for lactate decomposition and fatigue relief, and aerobic capacity of the athletes are improved to a certain degree. After training, heart rate QRI and TRIMP of the athletes are improved slightly. Among them, QRI is significantly improved from 19.6% to 21.6% after stage training, which shows slightly improvement of training quality and recovery capability of the athletes, i.e. adaptive capacity to training load; After physical training, research on monitoring QRI of the athletes during arrangement and relaxation shows that maximum heart rate level without voice guidance is 75.1bpm,which is higher than those with voice guidance 72.9bmp after 5-min quick recovery; QRI of the athletes is 31.9% when voice is used to guide relaxation, which is significantly higher than those without relaxation under voice guidance (QRI is 27.0%); night pressure monitoring unit (BodyGuard2) of Firstbeat is used to monitor sleeping conditions of the athletes. In the initial stage of heavy load training cycle, training load enables athletes to produce a strong stress response, which causes relatively poor sleeping and recovery conditions; with gradual adaptation of the athletes to the training load, in the middle and later stages of the cycle, stress response of the athletes during sleeping almost disappears, and their sleeping quality and recovery conditions are improved significantly.

Conclusions Through Power endurance training, lactate elimination capacity of the athletes, i.e. anti-fatigue capacity and quick recovery capability are improved; during quick recovery of the athletes, voice guidance can be used to effectively promote quick recovery of the athletes. Exercise heart rate, TRIMP and QRI can be used to perceptually and rapidly monitor completion of physical training load in a real-time way, Objective to evaluate recovery and sleeping conditions of the athletes, and effectively evaluate high-intensity interval physical training load and training effect.

PL-008 Adaptation of skeletal muscle to aerobic exercise: specific transcriptome response to acute exercise and training

2021-02-28T16:53:01+00:00

Objective Variety of processes including circadian rhythm and systemic factors affect expression of many genes in skeletal muscle during a day. Therefore, post-exercise gene expression depends on many factors: contractile activity per seas well as circadian rhythm, nerve activity, concentration of different substances in blood, feeding and fasting. In our study, we investigated specific for contractile activity changes in the transcriptome in untrained and trained (after an aerobic training programme) human skeletal muscle. The second goal was to examine effect of aerobic training on gene expression in muscle in basal state.

Methods Seven untrained males performed the one-legged knee extension exercise (for 60 min) with the same relative intensity before and after a 2 month aerobic training programme (1 h/day, 5/week). Biopsy samples were taken at rest (basal state, 48 h after the previous exercise), 1 and 4 h after one-legged exercise from m. vastus lateralisof either leg. This approach allowed us to evaluate specific changes in the transcriptome associated with contractile activity. RNAsequencing (84 samples in total; ~42 million reads/sample) was performed by HiSeq 2500 (Illumina).

Results Two months aerobic training increased the aerobic capacity of the knee-extensor muscles (power at anaerobic threshold in incremental one-legged and cycling tests), the maximum rate of ADP-stimulated mitochondrial respiration in permeabilized muscle fibres and amounts of oxidative phosphorylation proteins. After one-legged exercise, expression of many genes was changed in exercised muscle (~1500) as well as in non-exercised muscle (~400). Pronounced changes in gene expression in non-exercised muscle may be associated with many factors, including circadian rhythm (result of GO analysis).

To examine transcriptome changes specific for contractile activity, the difference in gene expression between legs was examined. In untrained muscle, one-legged exercise changed expression of ~1200 genes specific for contractile activity at each time point. Despite the same relative intensity of one-legged exercise, transcriptomic response in trained muscle was markedly lower (~300 genes) compare to untrained.

We observed a strong overlap between transcriptomic responses (~250 genes) and particularly between enriched transcription factor binding sites in promoters of these genes in untrained and trained muscles. These sets of genes and transcription factors play the key role in adaptation of muscle to contractile activity independently on the level of muscular fitness.

Surprisingly, 2 months aerobic training changed the expression of more than 1500 genes in basal state. Noteworthy, these genes demonstrated a small overlap (~200 genes) with genes related to specific response to acute exercise. Moreover, these genes were associated with significantly different biological processes than genes related to specific response to acute exercise.

Conclusions Specific for contractile activity changes in the transcriptome in untrained and trained human skeletal muscle were revealed for the first time. After 2 month aerobic training, the specific transcriptome response to acute exercise become much less pronounced. A computational approach reveals common transcription factors important for adaptation of both untrained and trained muscle. We found out that adaptation of muscle to aerobic training associates not only with the transitory changes in gene expression after each exercise, but also with the marked changes in transcriptome in basal state.

This work was supported by the Russian Science Foundation (141500768).

PL-009 Not just a one HIIT wonder: two popular HIIT protocols elicit similar health benefits in a controlled but real world environment

2021-02-28T16:52:32+00:00

Objective Currently 40% of the UK do not meet the physical activity guidelines with a ‘lack of time’ the most commonly cited barrier to sufficient physical activity. In laboratory based training interventions, high intensity interval training (HIT) offers a time-efficient alternative to moderate intensity continuous training (MICT) but its success requires expensive specialised cycle ergometers and vigorous encouragement from the researchers. To investigate whether two popular HIT protocols, performed using readily available cycle ergometers and without encouragement, can improve aerobic exercise capacity, arterial stiffness and body composition.

Methods Eighty-two sedentary males (n=26) and females (n=56) aged 18-65 participated in the study (28±1 y, BMI 25±0.4 kg.m^-2). In a randomised cross-over design, participants completed either 6 weeks of 30HIT (4-8x30s sprint with 120s active recovery) or 60HIT (6-10x60s sprint with 60s active recovery). Training sessions were completed on a Wattbike, 3 times per week. VO_2peak, body composition (DXA scan), blood glucose (oral glucose tolerance test (OGTT)) and arterial stiffness (pulse wave velocity (PWV)) were assessed pre and post each 6-week training phase, with 4-6 weeks washout period between interventions.

Results VO_2peakincreased post intervention in 30HIT (36±1 to 39±1 ml.min^-1.kg^-1) and 60HIT (36±1 to 39±1 ml.min^-1.kg^-1) (P<0.001), with no difference between intervention group (P=0.208). Body fat percentage decreased pre to post training in both conditions (P=0.001). PWV decreased in 30HIT (2%) and 60HIT (4%) (P<0.005). During the OGTT, there was a trend towards decreasing area under the curve pre to post (P=0.083). When normalized to Watt _maxthe participants producing a higher mean power output improved their VO_2peakmore than those producing a low MPO (P<0.05). Following further analysis this was only true in 60HIT (P<0.05).

Conclusions Both 30HIT and 60HIT could be effective real world strategies to improve aerobic capacity, body composition, arterial stiffness and insulin sensitivity. Improvements were seen even though the time spent sprinting was less in 30HIT (4mins compared to 10mins in 60HIT). In addition, how the 30HIT protocol is executed does not seem to have an effect on physiological outcomes. This suggests 30HIT may be a more applicable training intervention in the real world.

PL-010 Chronic mild stress improves glucose homeostasis via myonectin-mediated suppression of sympathetic activity in high-fat diet-fed mice

2021-02-28T16:52:03+00:00

Objective Recent studies suggest that chronic stress exposure can ameliorate the progression of diet-induced prediabetic disease, by inhibiting an increase in weight gain, caloric intake and efficiency and insulin resistance. To determine the underlying mechanism by which chronic stress improves the progression of type 2 diabetes, we developed a model of chronic mild stress in high-fat diet(HFD)-fed mice which are resistant to obesity and exhibit a healthy-like metabolic phenotype.

Methods High-fat diet (HFD): 45% kcal derived from fat (Research Diets, Inc.).Mice experienced one stressor during the day and a different stressor during the night. Stressors were randomly chosen from the following list : cage tilt on a 45° angle for 1 to 16 h; food deprivation for 12 to 16 h; white noise for 1 to 16 h; strobe light illumination for 1 to 16 h; crowded housing; light cycle (continuous illumination) for 24 to 36 h; dark cycle (continuous darkness) for 24 to 36 h; water deprivation for 12 to 16 h; damp bedding (200 ml water poured into sawdust bedding) for 12 to 16 h.Recombinant adeno-associated virus (AAV): AAV9 vectors encoding myonectin under the control of the ubiquitous CMV promoter (AAV9-CMV-Vip) or an equal dose of the AAV9-CMV-null vector were delivered to C57BL/6 mice by the tail vein. Mice were deprived of food for 16 h and then subjected to test 7 days after AAV injection.

Results Chronic stress improved glucose intolerance and sympathetic overactivity in HFD-fed mice. Chronic stress attenuated epinephrine(EPI)-stimulated glycerol release into blood in vivo and accelerated glycerol release from white adipose tissue followed by in vitro incubation with EPI. Chronic stress reduced plasma triglyceride but increased the levels of plasma insulin and myonectin. We further found that adeno-associated virus 9 (AAV9)-mediated myonectin overexpression improved glucose homeostasis and reduced epinephrine sensitivity. Myonectin overexpression reduced plasma norepinephrine, EPI and leptin levels, and increased insulin sensitivity in brown and white adipose tissue. Intense sympathetic activity with high-intensity running inhibited myonectin expression in skeletal muscle, whereas medium and low-intensity exercise running increased myonectin expression.

Conclusions These findings suggest that chronic mild stress can improve glucose homeostasis via myonectin-mediated suppression of sympathetic activity in high-fat diet-fed mice.

PL-011 Astaxanthin Reduces High Intensity Training Induced Myocardial Cell Apoptosis Via Activating Nrf2 in Rats

2021-02-28T16:51:34+00:00

Objective Long-term intensive training may led to ischemia oxygen reaction and increase the ROS. Astaxanthin, as the super antioxidant, was investigated to against anti-oxidative stress. By supplementing the astaxanthin, we wanted to observe if it can mediated Nrf2 reduces myocardial cell oxidative injury in rats after high intensity training of 6 weeks.

Methods 7-week SD male rats were divided into 3 groups randomly: control group ( C group，n =10)，high intensity training group ( HT group，n = 15)，astaxanthin and high intensity training group (HTA group，n = 15) . The rats in HTA group were given with astaxanthin 20 mg /kg·d and in HT group were given with oil during the training day．The serum cTnI，myocardial apoptosis index, the expression of myocardial BAX, Bcl2, Nrf2, HO-1, myocardial MDA，SOD and T- AOC activity were measured 24 hours after the last training．

Results After 6-week tranning of high intensity, compared with group C, the serum cTNI, myocardial apoptosis index, the expression of BAX and myocardial MDA were significantly higher in group HT(P<0.01).The Bcl2/Bax, the expression of HO-1, SOD and T-AOC activity were significantly declined (P<0.01). After the intervention of 6-week astaxanthin, compared with group HT, the serum cTNI, myocardial MDA, the myocardial apoptosis index, the expression of BAX were significantly lower in HTA group (cTNI(ng/ml): 1.16±0.27 VS 2.47±0.39, P<0.05; myocardial apoptosis index: 164.27±3.98 VS 196.20±9.65, P<0.01; BAX: 58.40±5.95 VS 78.03±3.80, P<0.01 ). Finally, Bcl2/Bax, SOD, T-AOC activity, the expression of Nrf2 and HO-1 were significantly higher (Bcl2/Bax : 1.92±0.10 VS 1.19±0.18, P<0.01; SOD(U/mg): 52.38±6.15 VS 38.32±3.36, P<0.01; T-AOC(U/mg): 30.22±4.07 VS 23.76±3.20, P<0.01; Nrf2: 93.61±8.53 VS 74.26±6.69, P<0.01; HO-1: 84.99±13.78 VS 64.22±11.39, P<0.05).

Conclusions The supplement of astaxanthin can mediate Nrf2 signaling pathway, and elevate the expression of Nrf2 and HO-1. Then it can increase the activity of SOD and T-AOC and reduce the myocardial oxidative level and myocardial apoptosis in rats caused by 6-week high intensity training. Finally, the structure and function of heart tissue are back to normal.

PL-012 Effect of hypoxic resistance training on the regulation of muscle mass and phenotype

2021-02-28T16:51:05+00:00

Objective Hypoxia is a state of lowered oxygen tension in tissue that can be created by environmental or pathological conditions. Whatever the origin of hypoxia, different tissues will adapt acutely and/or chronically to deal with this reduction in oxygen availability. Hypoxia has recently emerged as a particularly efficient stimulus to stimulate muscle cell proliferation and accretion of muscle mass and hypoxic resistance training has become popular amongst athletes as it is thought to favor muscle accretion. However, the molecular mechanisms are largely unknown.

Methods To determine those molecular mechanisms, 19 volunteers participated to 12 sessions of resistance training spread over 4 weeks whether in normoxia (n=9) or in hypoxia (n=10, FiO₂13.5% corresponding to 3500m altitude). Each session consisted in 6 sets of 10 repetitions of a one-leg extension exercise at 80% of one repetition maximum (1-RM). Blood and muscle samples in each leg were taken before and after the 4-week training period. Fiber types were determined by immunohistochemistry based on myosin heavy chain isotypes. Blood saturation (SpO₂, pulsoximetry) and tissue saturation index (TSI, near-infrared spectroscopy) were monitored during the exercise sessions.

Results Muscle thickness determined by ultrasound was increased by 7% in normoxia only (p=0.04). The 1-RM was increased in both groups but the increase was higher in hypoxia (+34%) than in normoxia (+24%) (p=0.02). In average, SpO₂stayed around 98-99% in normoxia and around 93-94% in hypoxia during each set of contractions. No difference in TSI between normoxia and hypoxia was measured, which averaged 60% before starting muscle contractions and 40% during muscle contractions. A trend towards a shift in fiber type from type I to type IIa was observed in normoxia (p<0.09) but not in hypoxia. Fiber area was not modified by any condition.

Conclusions In summary, 4 weeks of hypoxic resistance training induced a larger increase in 1-RM compared to normoxic resistance training, independently of muscle hypertrophy or any change in fiber type. Further investigation should determine whether metabolic or molecular changes may explain this potentiation of maximal muscle force by hypoxia.

PL-014 The gaseous metabolism characteristics of overweight adult women during exercise stress test

2021-02-28T16:50:36+00:00

Objective Overweight was a global public health problem. In recent years, the number of overweight people in China had been increasing. Being overweight had a serious impact on health. 31.1% of overweight people had aggregation of risk factors for cardiovascular metabolic diseases. And overweight people were more likely to suffer from some diseases, such as hypertension, diabetes, dyslipidemia and arthritis. This study compared the gas metabolism index differences between overweight and normal weight women when they did exercise under different load, and summarized gas metabolism characteristics of overweight women, in order to lay the foundation for instructing overweight women to do exercise scientifically, reduce the risk factors of chronic diseases such as cardiovascular disease, and enhance and improve physical fitness and health.

Methods Adult women between 20 and 30 years were taken as subjects. After measuring their height and weight, they were divided into normal weight group (BMI=18~23.9kg/m²) and overweight group (BMI＞24kg/m²) according to body mass index (BMI). There were 15 participants in each group. After the baseline test, using modified Bruce treadmill protocol, the air metabolism indexes of two groups were determined by Cortex MetaMax 3B portable gas metabolic analyzer, including oxygen uptake(VO₂), minute ventilation(MV), breathing frequency(BF), expiratory end-tidal CO₂concentration(ETCO₂), expiratory end-tidal O₂concentration (ETO₂), arterial blood carbon dioxide partial pressure (PaCO₂), carbon dioxide output(VCO₂), oxygen pulse and maximal voluntary ventilation(MMV), etc. The differences of gas metabolism indexes among resting, exercise, and recovery stages were compared and analyzed.

Results (1) Most of indexes such as VO₂, VCO₂, and MV rose gradually with the load increase during exercise stress test except for ETO₂and PaCO₂. VO₂, PaCO₂, VCO₂and ETCO₂of overweight group were significantly lower than normal weight group during the same load. PaCO₂of overweight group at grade 4 was significant lower than normal weight group by 5.6 mmHg (P<0.05). VCO₂of overweight group at grade 5 was significant lower than normal weight group by 0.6L/min (P<0.05). ETCO₂of overweight group at grade 3 and 4 were significant lower than normal weight group about 0.5% and 0.6% respectively (P<0.05). (2) During recovery stage, most of indexes decreased gradually, such as MV and BF, while ETO₂presented a rising trend. At a certain time during the recovery stage, ETCO₂of overweight group was significantly lower than normal weight group (5.3% vs 5.8%), while MMV, MV and oxygen pulse were significantly higher than normal weight group (P<0.05). MMV of overweight group at 2, 3 and 4 minutes were significant lower than normal weight group by1L/min, 1L/min and 0.9L/min, at the same time, MV of overweight group were significant lower than normal weight group by17.8L/min, 20.1L/min and 16.9L/min. The oxygen pulse of overweight group during whole 5 minutes recovery period were significantly higher than normal weight group by 2.7L/min, 3.9L/min, 3.9L/min, 2.9L/min and 2.0L/min. (3) The gaseous metabolism between two groups was significantly different when they did 7.1 and 10.2 METs exercise.

Conclusions Although there was no difference in gas metabolism between overweight and normal weight adult women in resting state, the respiratory function of overweight women was weaker than normal weight women during exercise, especially at the intensities of 7.1 and 10.2 METs. During the recovery period after exercise stress test, the recovery rate of gas metabolism in overweight adult women was slower than that of normal weight women.

PL-015 Aerobic exercise increases BKCa channel expression to enhance tracheal smooth muscle relaxation in a murine asthma model

2021-03-02T16:35:46+00:00

Objective Increasing evidence has shown that moderate-intensity aerobic exercise training reduces airway hyperresponsiveness (AHR) in patients with asthma. However, the mechanisms underlying exercise-induced improvements in smooth muscle contractility have not been fully elucidated. Large-conductance Ca²⁺-activated K⁺ channels (BK_Ca) are expressed broadly on smooth muscle cells and play an important role in the regulation of smooth muscle contraction. We tested the hypothesis that exercise training increases the contribution of BK_Ca channel to tracheal smooth muscle relaxation in in ovalbumin (OVA)-challenged asthmatic rats.

Methods Rats were sensitized/challenged with OVA or saline and exercised at a moderate intensity 5 times/week for 4 weeks. Tracheal smooth muscle contractility was tested. Membrane potential of primary cultured tracheal smooth muscle cells was measured. In addition, western immunoblotting was performed to study the expression levels of BK_Ca channel protein.

Results The contraction of rat airway smooth muscle induced by carbachol was significantly increased with asthma and exercise training reversed this alteration. Application of BK_Ca channel agonist, NS1619, induced tracheal smooth muscle relaxation. NS1619-induced relaxation was decreased in asthmatic rats, however exercise training significantly increased NS1619-induced relaxation. In primary cultured smooth muscle cells, NS1619-induced membrane potential was reduced with asthma and this alteration was diminished after exercise training. Additionally, western blotting revealed that the protein expression of BK_Ca was reduced in asthmatic group and aerobic exercise significantly improved BK_Ca expression.

Conclusions The present study reveals that aerobic exercise training increases BK_Ca expression on tracheal smooth muscle, which partly underlies the beneficial effect of exercise on improving airway smooth muscle relaxation in asthma.

PL-016 Endurance training, muscle fibre type composition and the maximal capacity for fat oxidation

2021-02-28T16:50:07+00:00

Objective A greater capacity for fat oxidation in endurance trained athletes is linked to greater utilisation of intramuscular lipid (IMCL). IMCL breakdown occurs only in type I muscle fibres yet little is known about the fibre type specific abundance of lipid regulatory proteins. We explored the impact of endurance training on the maximal rate fat oxidation, muscle fibre type and muscle fibre type specific abundance of proteins regulating IMCL metabolism.

Methods Endurance trained (n=7, 28 ± 3 years, VO_2max62.6 ± 1.6 ml·min^-1·kg^-1) and untrained (n=8, 25 ± 1 years, VO_2max44.9 ± 1.9 ml·min^-1·kg^-1) males performed an incremental exercise test to determine maximal fat oxidation rate. Muscle fibre type composition and fibre type-specific IMCL content was assessed with immunofluorescence microscopy and protein abundance was analysed with immunoblotting on pooled single muscle fibres and whole muscle.

Results Endurance trained individuals displayed a higher peak fat oxidation rate (0.49 ± 0.05 vs. 0.20 ± 0.03 g·min^-1, P<0.05), which correlated with type I fibre percentage (R = 0.83, P < 0.01) and VO_2max(R = 0.78, P < 0.01). Type I muscle fibres from endurance trained individuals had a greater abundance of ATGL. In whole muscle, the endurance trained group had greater abundance of PLIN2, PLIN5 and ATGL compared to the untrained group (P < 0.05). Furthermore, autophagy flux measured as LC3-II/I ratio was higher in type I muscle fibres and LC3-II/I, lysosomal markers (LAMP2) and chaperone-mediated autophagy markers (LAMP2A) were all higher in whole muscle of endurance trained individuals (P < 0.05).

Conclusions These results demonstrate that the maximal rate of fat oxidation is related to the proportion of type I muscle fibres. Furthermore, IMCL storage and the abundance of key proteins regulating lipid metabolism is fibre type specific and greater in endurance trained individuals. Muscle fibre type composition should be considered when investigating the regulation of IMCL utilisation and markers of autophagy.

PL-017 High-fat overfeeding increases intramuscular triglyceride content and perilipin protein expression in human skeletal muscle

2021-02-28T16:49:37+00:00

Objective High-fat high-calorie diets can induce whole body insulin resistance (IR) whilst increasing stores of intramuscular triglyceride (IMTG) contained within lipid droplets (LD). Perilipin (PLIN) proteins assist in IMTG storage. Synaptosomal-associated protein (SNAP23) may support LD growth and also direct IMTG-derived fatty acids (FA) to mitochondria for β-oxidation. The objectives of this study were: 1) to test the hypothesis that 7 days of high-fat overfeeding increases IMTG content to prevent lipid induced muscle IR and 2) identify changes in PLINs, SNAP23 and mitochondria content and colocalisation of PLINs with LD, and SNAP23 with LD and mitochondria.

Methods Muscle biopsies were obtained from thevastus lateralisof thirteen healthy individuals (age: 23±1years, BMI: 24.4±0.7kg.m^-2) before (0min) and during (30min) an oral glucose tolerance test (OGTT), pre and post 7-days consuming a high-fat (65% energy) high-calorie (+50% kcal) diet. IMTG, PLIN2, PLIN3, PLIN5, SNAP23 and mitochondria content were measured using (semi)-quantitative confocal immunofluorescence microscopy. PLIN2, PLIN3 and PLIN5 colocalisation to LD was measured using object-based colocalisation analyses. Pearson’s correlation coefficient quantified colocalisation between SNAP23 and plasma membrane (PM), mitochondria and LD. Phosphorylation of intermediates of the muscle insulin-signalling cascade (Akt and AS160) were measured at 0 and 30 min of the OGTT before and after the dietary intervention.

Results Following overfeeding phosphorylation of Akt and AS160 in muscle was not impaired during the OGTT, however Matsuda index of whole-body insulin sensitivity decreased (-23%; P < 0.01). IMTG content increased in type I fibres (+100%; P < 0.001) due to both an increase in LD number (+43%; P < 0.001) and size (+44%; P< 0.001). Of the PLINs investigated, only PLIN3 content increased (+50%;P < 0.01) exclusively in type I fibres. PLIN2-associated LD increased (+80%; P < 0.01) in type I fibres only, whereas PLIN3 and PLIN5-associated LD were unaltered. SNAP23 and mitochondria content did not change, nor did the colocalisation of SNAP23 with the PM, mitochondria or LD.

Conclusions Our data confirm the hypothesis that following high-fat overfeeding IMTG stores increased whilst activation of key muscle insulin signalling components were maintained. The increase in IMTG stores is likely supported by the concurrent increase in total PLIN3 content and a redistribution of existing stores of PLIN2 to the expanded LD pool in type I fibres. To confirm if increased IMTG storage protects muscle from IR future research should determine whether meal-derived FAs are directed to IMTG rather than ceramides and diacylglycerol.

PL-018 Effects and safety of exercise combined with medication and diet in treatment of diabetes and comorbidity

2021-02-28T16:49:09+00:00

Objective The role of exercise in the prevention and treatment of chronic diseases is widely accepted and regular physical exercise may play an irreplaceable role beyond traditional medicine and drug treatments. However, current guidelines do not provide details on the characteristics of exercise programs which are aimed to be carried out concomitantly to drug treatments. Moroever, the safety of combined exercise and drug treatments has rarely been considered.

The future of exercise is medicine research will likely need to focus on questions such as how to build customized exercise programs for different patients in the context of individual physiological responses to exercise? When combining drug and concomitant exercise treatment, what is the optimal exercise prescription in terms of timing, intensity and duration? Does exercise only have an additive effect or may exercise actually reverse or even cancel out some of the expected effects induced by the drug treatment? What is the role of diet in exercise interventions? Does a given exercise program affect the lipid and glucose metabolism to the same extent?

In this report, we will present different randomized clinical trials conducted in our research group to tackle some of the abovementioned questions. This particularly includes patients with comorbidity conditions (prediabetes and non-alcohol fatty liver disease,NAFLD), as well as patients with type 2 diabetes (T2D).

Methods Two different randomized trials are included, both of which were conducted in China (ChiCTR-IOR-16008469 and ISRCTN 42622771). The ChiCTR-IOR-16008469 study was a randomized crossover trial. The aim of this study was to assess whether the duration between metformin administration and high-intensity cycling (HIIT) affects the glucose metabolism. T2D patients performed a single session of HIIT (~25 minutes) at 30 (EX30), 60 (EX60), and 90 (EX90) minutes following breakfast and metformin administration in a randomized order. Subjects’ diurnal glucose metabolism was assessed between 8:00 a.m. and 4:00 p.m. (Metf) of each exercise day as well as on a control day. Furthermore, insulin was assessed both before and immediately after each exercise bout.

The ISRCTN42622771 trial was a four arm randomized trial. Six-hundred and three patients from seven clinics were recruited, out of which 115 individuals aged 50-65-year fulfilled the inclusion criteria (impaired fasting glucose (IFG) or impaired glucose tolerance (IGT) and NAFLD) and were randomly assigned (1:1:1:1) to either of the four groups: aerobic exercise (AEx, n = 29), diet intervention (Diet, n = 28), aerobic exercise plus diet intervention (AED = 29), or no intervention (NI = 29). The study spanned over anaverage period of 8.6 months (7-11 months). Progressive supervised aerobic exercise training (60-75% intensity) was carried out 2-3 times/week in 30-60 min/sessions, and the diet intervention consisted of a lunch with 38% carbohydrate and diet fibre of 12g per day, while the remaining meals were freely chosen but with supervised nutrition intakes. The hepatic fat content (HFC) assessed by 1H MRS, glycated haemoglobin (HbA1c) and insulin sensitivity were assessed by conventional methods.

Results In study 1, we found that in diabetes patient glucose levels significantly decreased in all exercise settings, irrespective of the timing. However, whenHIIT was performed at 30 minutes post-metformin administration, the peak glucose was lowered, thereby further stabilizing the postprandial glucose fluctuation. The risk for hypoglycemia at different times to exercise after metformin administration was highest in EX90 (22.2%) compared to EX30 (3.7%) and EX60 (7.4%). While the lactate level was 19% higher in EX60 and 8% higher in EX90 compared to EX30. Compared with Metformin, the decrease in insulin was larger in EX30 and EX60 (both p < 0 001). These results indicate that timing of exercise is an important factor to consider when prescribing exercise as adjuvant to metformin therapy for T2DM patients.

In study 2, we showed that in patients with morbidity (prediabetes with NAFLD), HFC was significantly reduced in the AEx (–24.4%), diet (–23.2%), and AED (–47.9%) groups, as opposed to the 20.9% increase in the NI group (p=0.006, p=0.002, and P<0.0001, respectively).Importantly, HFC decreased to normal levels (<5.6%) in ten (44%) out of 23 participants in the exercise plus diet group and nine (41%) out of 22 participants in the diet group, while the in the exercise group it decreased only in three (14%) out of 29 participants. Further, all intervention groups showed improvements ininsulin sensitivity (AEx 33%, p=0.023, Diet 37%, p=0.012, and AED 34%, p=0.029) but only the AED group significantly decreased HbA1c (-4.4%, p=0.01) compared with the NI group (1.9% and -0.6%). However, after controlling for the change of body weight as well as for the duration of the intervention and baseline values, the significant differences in HbA1cand insulin sensitivity between the groups disappeared. Furthermore, based on HbA1c IFG or IGT, no significant remission and progression from prediabetes to diabetes were observed between the intervention and NI.

Conclusions The results derived from these two trials imply that: 1) the combined effects of exercise and metformin therapy on T2D should take into account that both exercise and metformin are likely to affect the lactic metabolism because T2D is considered as a redox disease. For the acute effect of exercise combined with metformin therapy, exercising at 30 minutes post-metformin administration appeared to be optimal for reducing glucose fluctuation. To avoid the risk for hypoglycemia and lactases with the combined treatment, selecting optimal timing may be the first and easiest step towards personalized exercise medicine. Thus, when exercise is recommended to diabetic patients, the timing of exercise may be an important consideration so that the therapeutic effects of metformin are not compromised. However, further studies are warranted to elucidate the long-term effects of combining metformin and exercise on glycemic control and lactic metabolism as well as the underlying mechanisms. 2) Aerobic exercise training combined with a fibre-enriched diet can aid reduce HFC more effectively than either exercise or increased fibre intake alone in pre-diabetic patients with NAFLD. However, the effect on glycaemic control and insulin sensitivity is not substantial. Therefore, it remains to be addressed why the same intervention protocol did not show the similar effect on the HFC and glycaemic control/insulin sensitivity in the same subjects. When these questions being uncovered, the combined intervention could be considered as an integral part of lifestyle interventions for patients with a cordiality condition for an increased risk of developing T2D.

PL-019 Effect of early exercise on autophagy of liver tumor in mice

2021-02-28T16:48:39+00:00

Objective To investigate whether the liver autophagy level can be altered by pre exercise training in mice liver tumors.

Methods 40 Male C57BL/6J mice aged 7 months were randomly divided into 2 groups: control group (YC) and exercise group (YE). YE were exercised on a treadmill for 12 weeks (12m/min). After12 weeks each group was randomly divided into two groups. The tumor model was constructed by injection of HEPA1- 6 mouse hepatoma cell into liver tissue.Then the groups were control group (YC), exercise group (YE), tumor group (YCT), exercise tumor group (YET).The experimental samples were prepared on the 13 day after the tumor model was constructed. the hematoxylin and eosin stain of the liver was observed.The expression of autophagy related protein BECLIN1, LC3-II and ATG5 in liver tissues of mice was detected by Western blot.

Results Compared with YCT group,the boundary of inflammatory cells and tumor cells in YET group was clear with normal cells.Compared with YCT group, the expression levels of BECLIN1, LC3-II and ATG5 in liver tissue of YET group were significantly higher (p < 0.01, P < 0.01, P < 0.05).

Conclusions Early exercise can help the 7 month old mice to resist the occurrence and development of the liver tumor. It's probably associated with increased level of autophagy in the liver by early exercise training.

PL-020 Establishment of skeletal muscle-specific PGC-1α overexpression model via in vivo local transfection

2021-02-28T16:48:08+00:00

Objective To establish a skeletal muscle-specific PGC-1α overexpression mouse model via in vivo local transfection.

Methods For the PGC-1α in vivo transfection study, the Male FVB/N mice were randomly divided into 2 groups: subject to green fluorescent protein (GFP) transfection (Con-GFP), and subject to PGC-1α in vivo transfection (Con-PGC-1α). Plasmid DNA solution (2.5 mg/ml GFP or 2.7 mg/ml Flag-PGC-1α) were injected into the proximal (6 ml) and distal (6 ml) ends of the muscle belly. Following the injections, electric pulses were applied through 2 stainless steel pin electrodes laid on top of the proximal and distal myotendinous junctions. Then skeletal muscle and myocardium were isolated, and PGC-1α, mtTFA, NF-κB, MnSOD, FNDC5 protein expression were measured with Western blot.

Results n skeletal muscle, compared with con-GFP group, the expression of PGC-1α (+125%, p<0.01), mtTFA (+210%, p<0.01), and FNDC5 (+47%, p<0.05) were significantly increased in con-PGC-1α group. However, NF-κB and MnSOD protein level had no change in con-PGC-1α group. In myocardium, compared with con-GFP group, the expression of mtTFA (+130%, p<0.01) and FNDC5 (+55%, p<0.05) were significantly increased in con-PGC-1α group.

Conclusions Skeletal muscle-specific PGC-1α overexpression model via in vivo local transfection was established, which was supported by elevated expression of PGC-1α and its downstream FNDC5 and mtTFA. Furthermore, skeletal muscle-specific PGC-1α overexpression induced increase in myocardial mitochondrial biogenesis, while relative mechanism remains to be determined.

PL - 021 The research of High temperature exercise under different humidity environment effect on the body of water and salt metabolism

2021-02-28T16:47:11+00:00

Objective Objective: This study was to investigate the body under high temperature (33 ℃) with different relative humidity (80%, 50%, 20%) combination of environment, respectively for 20 min 60% VO2max individual strength of quiet before and after the exposure of movement and under the same conditions, by measuring the participants within the body weight, serum sex hormone of blood, blood Na+、K+, Na+、K+ concentration in the urine of change, to explore in the sports stress and thermal stress of two kinds of stimulating the body water and salt metabolism characteristics, and to explore the effects of environmental humidity on the body's homeostasis.

Methods Methods: This study selected 12 students of sports training major from Beijing sports university as subjects, with themselves as the control. The experiment is divided into six categories, respectively: high temperature 33℃ and 20% RH exposure group, the high temperature 33℃ and 20% RH campaign group, high temperature 33℃and 50% RH exposure group, the high temperature 33℃ and 50% RH campaign group, high temperature 33℃ and 80% RH exposure group and high temperature 33℃ and 80% RH. In this study all the environmental temperature are set up to 33℃, exercise intensity level of 60% VO2max selection for individual participants. Before every experiment, all participants were asked to quiet sit for 20 min and then measure the subjects' body weight, charge the subjects' vein blood and urine, take the same operation immediately after the experiment. Blood samples were stored at room temperature for 1 h, and 3000r/min was centrifuged for 20min. Serums were gathered through centrifugation, The urine and Serums were partial shipments in tube to be indicators of measurement. Serum Renin、ANGII、ALD、ADH、ANP、Na+、K+ concentration of serum and urine were tested

Results Results: (1)The subjects' weight loss percentage of exercise group was obviously higher than that of quiet exposure group, the difference is statistically significant (P < 0.01); In 80% RH environment weight loss percentage is significantly higher than that of 50% RH and 20% RH values (P < 0.01).There is no difference between 20%RH and 50%RH. (2) The exercise group of Renin, ANGII, ALD, ADH, concentration is significantly higher than the value of exposed group (P < 0.01), but the ANP concentrations were significantly lower than pure quiet exposure levels (P < 0.01).

Conclusions Conclusions: (1) The body sweat more after exercise than just quiet exposed in high temperature, weight loss phenomenon more obvious; And with the increase of relative humidity environment, dehydration will more serious. (2) Exercise factors can significantly promote the release of blood Renin, ANGII, ALD, ADH and inhibit the release of ANP in the blood. By the way of strengthening the absorption process of water and ions, it can maintain the body's balance of water and ions.

PL - 022 Effects of exercise-induced fatigue on autonomic activity and dopamine metabolism in rats after D2DR modulation

2021-02-28T16:46:43+00:00

Objective Objective: After injection of D2DR antagonist and agonist, the autonomic activity and striatal neurons electrical activity of rats with exercise-induced fatigue were recorded to explore the role of DA receptors in the central mechanism of exercise-induced fatigue.

Methods Methods: Used male Wistar rats, randomly divided into 7 groups: control group (CG), one-time exhaustive exercise group (1FG), 3D repetitive exhaust group (3FG), and 7D repetitive exhaustion group (7FG), 7D repeated exhaustive 24h recovery group (24RG) and 7D repeated exhaustive 48h recovery group (48RG). After 1 week adaptive training in rats, rats attend 7D exhaustive treadmill exercise. Subsequently, the autonomic activity changes of each group with D2DR antagonists and agonists were observed in open filed. Used glass microelectrode extracellular recording technique to observe the dorsolateral striatum neurons change of the rats injected with D2DR antagonist spiperone. Real-time PCR (RT-PCR) molecular biology methods were used to measure the expression of D1DR and D2DR in the striatum after exercise-induced fatigue. To investigate the role of DA neurotransmitter and receptor on central mechanism of exercise-induced fatigue.

Results Results: (1) With the increase of treadmill exercise load, the total distance of each group became shorter, and the recovery phase gradually recovered to a quiet level. The maximum exercise speed of rats in 7FG was significantly higher than 1FG (P<0.05).The average exercise speed of rats in each group was significantly lower than CG (P<0.05).The average speed of 7FG and 24RG were significantly lower than 1FG(P<0.05). the average movement speed of the 48RG was higher than 7FG;(2) After D2DR antagonist injection, the exhaustive time of rats was significantly lower than CG(P<0.01), while the exhaustive time of D2DR agonist intervention was significantly increased (P<0.01).The active areas of the rats in the open field were concentrated in the corners and margins. The distance of normal rats in 60 min was about 159 m. The activity of rats decreased after D2DR antagonist intervention, the movement distance of rats in CG、1FG and 48RG were significant reduced;(3) After injection of D2DR antagonist, The excitability of dorsolateral striatum neurons were affected by 56.10%, 9.76% (4/41) increased excitability, and 46.34% (19/41) decreased, the inhibitory effect of D2DR agonist was higher than excitatory effects (P<0.05);(4) RT-PCR data showed that there was no significant change in the expression of D1DR in the striatum after exercise-induced fatigue, and D2DR was significantly higher than the CG (P<0.01).

Conclusions Conclusion:(1) With the increase of fatigue in rats, the total distance of exercise in each group gradually decreased;(2) Exercise-induced fatigue affects the expression of DA receptors in the striatum;(3) D2DR antagonists and agonists can affect the locomotor ability of rats;(4) D2DR antagonist can inhibit striatal neurons in rats with exercise-induced fatigue, suggesting that D2DR may be one of the drug intervention targets of exercise-induced fatigue.(NSFC: 31401018, SKXJX: 2014014).

PL - 024 The characteristics for the primary school students’ physical activity

2021-02-28T16:46:13+00:00

Objective This thesis provides a theoretical basis for improving children’s physical activity levels and promoting the healthy development of primary school children.

Methods Measuring the height, shape index of children which are in 3-5 grades of primary school in Nanjing and taking the BMI cut-off point of the Cole as the object of this study BMI evaluation criteria. Applying the ActiGraph GT3X accelerometer to measure the physical activity of children in seven consecutive days which includes five school days and two weekend days. By counting the physical activity in a 60s interval, children’s physical activity can be evaluated. Besides, using 100cm as the cut-off point, the number of students’ sedentary breaks can be calculated. And the relationship between the results and students’ BMI characteristics can be discussed.

Results (1) For the male students, the average sedentary breaks, LPA and MVPA time is 849.47min, 297.01min and 37.99 min respectively. And for the female students, the sedentary breaks, LPA and MVPA time is 874.12min, 272.33min, and 32.55min respectively. The male students’ MVPA time is significant higher than the female students (P<0.05), but for both of them, the MVPA time cannot achieve the international children’s physical activity daily recommended amount which is 60min. Besides, there is no difference between different grades(P>0.05). (2) Students’ daily MVPA time was significantly higher than the weekend MVPA time (P <0.05). Male students’ MVPA time in the school days is higher than the MVPA time in the weekend(P<0.01). For the children in different body shape, the MVPA time in the school days is higher than that in the weekend(P<0.05). In the school days, the male students’ MVPA time is significant higher than that of female. (P<0.05). In the weekend, the normal group’s MVPA time is much higher than that of overweight and obese groups(P<0.05).(3) The sedentary breaks of normal group is less than that of overweight and obese groups(P<0.05). There is no significant difference between different gender, grades and BMI(P>0.05).

Conclusions （1）Male students’ MVPA time is higher than the female students.（2）The MVPA time in the school days is much higher than in the weekend. In terms of the sedentary breaks, there is no difference between different gender, grade and body shape.（3）Students with more sedentary breaks get lower BMI,and the change of LPA will be the primary cause of MVPA changing.

PL - 025 THE EFFECT OF SELECTED PARAMETERS ON HAND GRIP STRENGTH AMONG CRICKET PLAYERS IN PRISON DEPARTMENT

2021-02-28T16:45:44+00:00

Objective Handgrip strength is a marker of upper body strength. The purpose of this study is to examine the relationship between the dominant handgrip strength and twelve selected parameters of cricket players in Sri Lanka Prison Department. The twelve selected variables are as follows; age, height, weight, arms subcutaneous fat percentage, skeletal muscle mass percentage, upper arm length, fore arm length, hand width, hand length, hand span, hand circumference and free testosterone hormone level.

Methods The study is conducted on a population of 35 cricket male players. Sample and population are the same. This population mainly consist of players, who practice and play regular matches for the club and exclude players who are suffering from any acute or chronic upper limb injuries and players, who under performed in the recent matches. Dominant handgrip strength and other selected parameters are measured via standard techniques. Blood samples were collected to determine free testosterone level of players, for better result this study collected blood samples were at 7.30 a.m. to 8.00 a.m after a better sleep at previous night. Ordinary electric centrifuge use to centrifuge the sample tubes. Once centrifugation is completed the serum is separated from the centrifuged blood sample used by pipette. This study used High-performance liquid chromatography (HPLC) method to analyze free testosterone hormone level of the samples. Handgrip strength tests were performed the same morning of blood sample collected. The purpose of this test in this study is to measure the maximum isometric strength of the hand and forearm muscles of players. This study used “camry eh101” electronic hand dynamometer to measure hand grip strength and strength was measured in kilograms. This study used “Karada scan” bioelectrical impedance analysis to estimate percentage of body fat and fat free muscle mass of cricket players. Anthropometric data was measured as follows; stands erect, looking straight ahead, heels together, weight distributed equally on both feet, and with his arms hanging naturally at his sides. All measurements were made on the dominant hand of the body using steel tape and the circumferences of body parts were measured with the help of flexible steel tape. Statistical analysis is carried out utilizing SPSS and Minitab software.

Results Pearson correlation of dominant handgrip strength (kg) and age = -0.521 at p-value = 0.001. Pearson correlation of dominant handgrip strength (kg) and height (cm) =0.394 at p-value = 0.019. Pearson correlation of dominant handgrip strength (kg) and weight (kg) = 0.100 at p-value = 0.568. Pearson correlation of free testosterone level (pg/mL) and dominant handgrip strength (kg) = 0.496 at p-value = 0.002. Pearson correlation of dominant handgrip strength (kg) and arms subcutaneous fat percentage (%) = -0.424 at p-value = 0.011. Pearson correlation of dominant handgrip strength (kg) and arms skeletal muscle mass percentage (%) = 0.436 at p-value = 0.009. Pearson correlation of dominant handgrip strength (kg) and fore arm length (cm) = 0.591 at p-value = 0.000. Pearson correlation of dominant handgrip strength (kg) and upper arm length (cm) = 0.240 at p-value = 0.165. Pearson correlation of dominant handgrip strength (kg) and Hand width (cm) = 0.319 at p-value = 0.062. Pearson correlation of dominant handgrip strength (kg) and hand length (cm) = 0.608 at p-value = 0.000. Pearson correlation of dominant handgrip strength (kg) and Hand span (cm) = 0.407 at p-value = 0.015. Pearson correlation of dominant handgrip strength (kg) and hand circumference (cm) = 0.232 at p-value = 0.180. Correlation of age and free testosterone hormone level (pg/mL) = -0.359 at p-value = 0.034. Correlation of age and arms subcutaneous fat percentage = 0.462 at p-value = 0.005. Correlation of age and arms skeletal muscle mass percentage = -0.619 at p-value = 0.000. Pearson correlation of weight (kg) and arms subcutaneous fat (%) = 0.596, P-value = 0.000. Correlation of weight (kg) and arms skeletal muscle mass (%) = -0.793 at p-value = 0.000. Pearson correlation of free testosterone hormone level (pg/mL) and arms skeletal muscle mass percentage (%) = 0.375 at p-value = 0.026. Standing height, correspondingly indicate significant a relationship with fore arm length, upper arm length, hand length, hand span and hand circumference. This indicates the when body height increase, it will subsequently lead to increment of the forearm length, upper arm length, hand length, hand span and hand circumference. Regression equation for dominant handgrip strength is (kg) = - 0.578 age + 3.79 hand length (cm). Observed test statistic (4.309) > at critical value 5 %( 2.3205). It can be concluded with 95% confidence that at least one of the two variable significantly contribute for dependent variable of regression model. β_1 P value (0.019) < 0.05, β_2 P value (0.001) < 0.05. Therefore, predictor variables age and hand length are significant in this regression equation. Both age and hand length show a VIF value of 1.16 and which indicate that there is strong multicollinearity between the variables. Adjusted R-squared = 0.438 and it can be concluded that the fitted model is captured 43.8% of observed variability.

Conclusions Pearson correlation of dominant handgrip strength and height, free testosterone level, fore arm length, hand length, hand span, arms subcutaneous fat and arms skeletal muscle mass percentage have a statistically significant relationship. The direction of the relationship is positive. Meaning that these variables tend to increase together. Pearson correlation of dominant handgrip strength and age, arms subcutaneous fat have a statistically significant relationship. The direction of the relationship is negative meaning that these variables move in inverse, or opposite, directions. Pearson correlation of dominant handgrip strength and hand circumference, weight, upper arm length and hand width have no statistically significant relationship. Age and Free testosterone hormone level, arms skeletal muscle mass percentage have a statistically significant linear relationship. The direction of the relationship is negative. In other words, as Age increases, the free testosterone hormone level and arms skeletal muscle mass percentage decreases. Pearson correlation of Age and Arms Subcutaneous fat percentage have a statistically significant linear relationship. The direction of the relationship is positive. Weight and Arms Skeletal muscle mass percentage have a statistically significant linear relationship. The direction of the relationship is Negative. Pearson correlation of Weight and Arms Subcutaneous fat percentage have a statistically significant linear relationship. The direction of the relationship is positive. Pearson correlation of Free Testosterone hormone level and Arms Skeletal muscle mass percentage have a statistically significant linear relationship. The direction of the relationship is positive. 43.8% of handgrip strength depends on the variables age and hand length.

Coaches should periodically assess the free testosterone level and percentage of lean body mass of the players to maintain optimal level. Cricket coaches and team selectors can use age, height, fore arm length, hand length, hand span, free testosterone hormone level, arms subcutaneous fat and arms skeletal muscle mass percentage as talent predictors to select ideal players for cricket teams or to identify potential children/players. Cricket Brain Centers can use this research to analysis player performance and predict their future performance

PL - 026 Mismatch between skeletal muscle glucose delivery, interstitial concentration and membrane permeability may limit insulin sensitivity after exercise

2021-02-28T16:45:14+00:00

Objective The relationship between skeletal muscle perfusion, interstitial glucose concentration and sarcolemmal permeability to glucose in exercise-induced increases in muscle insulin sensitivity is not well established. A single bout of exercise increases skeletal muscle insulin sensitivity through coordinated increases in insulin-stimulated microvascular perfusion and insulin signalling Reducing leg and muscle microvascular blood flow with local nitric oxide synthase (NOS) inhibition during a hyperinsulinaemic euglycaemic clamp reduces leg glucose uptake in a previously exercised, but not in a contralateral non-exercised leg, without affecting insulin signalling in either leg (Sjoberg et al. 2017). Therefore, it is possible that the reduction in muscle perfusion decreases muscle interstitial glucose concentration to a point that limits skeletal muscle insulin-stimulated glucose uptake following exercise. We examined this using microdialysis of vastus lateralis muscle.

Methods Ten healthy males (Age: 27±1 yr., Weight: 77.7±2.3 kg, BMI 23.9±0.5, VO₂ peak: 50.7±1.5 ml·kg^-1·min^-1) performed 60 min of 1-legged knee extensor exercise at 80% of 1-legged peak work load with three 5 min intervals at 100% 1-legged peak work load. Participants then rested for 4 hours and catheters were inserted into the femoral artery and vein of both legs for subsequent measurement of leg glucose uptake and for femoral artery infusion of the NOS inhibitor NG-monomethyl L-arginine acetate (L-NMMA) and the vasodilator ATP. Catheters were also placed in antecubital veins for infusion of insulin and glucose. Three microdialysis catheters, with a semi-permeable membrane the length of 30 mm and a molecular cut-off at 20,000 dalton, were inserted into the vastus lateral muscle of both legs. Glucose and D-[6-³H(N)]glucose were added to the perfusate. Four hours after discontinuing the exercise a 225 minute euglycaemic hyperinsulinaemic clamp was initiated (insulin infusion 1.4 mU^-1kg^-1min). Ninety min into the clamp L-NMMA was infused at a constant rate (0.4 mg·kg^-1 leg mass·min^-1) into both femoral arteries for 45 min. The insulin infusion was maintained for another 90 min and during the last 45 min ATP (0.3 μmol∙ml^-1) was infused locally into both femoral arteries at a rate of 200-350 μl∙min^-1 to obtain a leg blood flow that was double the blood flow during insulin only infusion. A second control protocol was undertaken that was identical in regards to exercise and recovery but no insulin, L-NMMA or ATP was infused.

Results During the clamp leg glucose uptake and leg blood flow were higher (P<0.05) in the previously exercised than the control leg whereas the interstitial glucose concentration decreased to lower (P<0.05) values in the exercised (~3.1mM) than the control (~4.8mM) leg. Estimated sarcolemmal glucose permeability was twice as high (P<0.05) in the exercised compared with the rested leg. The NOS inhibitor L-NMMA decreased LBF in both legs and interstitial glucose concentration dropped to ~2.3 mM in the exercised but only to ~3.7 mM in non-exercised muscle. This abrogated the augmented effect of insulin on LGU in the exercised leg while apparent sarcolemmal permeability to glucose remained unchanged with L-NMMA in both legs. Doubling leg blood flow by local infusion of ATP increased leg glucose uptake in both legs without any major change in interstitial glucose concentration or sarcolemmal permeability to glucose.

Conclusions These findings suggest that during flow restriction due to L-NMMA, the interstitial glucose concentration becomes limiting for leg glucose uptake in exercised but not in non-exercised muscle. Therefore, the vasodilatory effect of insulin is an important component of the increased insulin sensitivity to stimulate glucose uptake following exercise by limiting the drop in the interstitial glucose concentration that occurs due to the increased sarcolemmal permeability to glucose.

Reference

Sjoberg, K. A., C. Frosig, R. Kjobsted, L. Sylow, M. Kleinert, A. C. Betik, C. S. Shaw, B. Kiens, J. F. P. Wojtaszewski, S. Rattigan, E. A. Richter, and G. K. McConell. Exercise Increases Human Skeletal Muscle Insulin Sensitivity via Coordinated Increases in Microvascular Perfusion and Molecular Signaling. Diabetes 66: 1501-10, 2017.

PL - 027 Up-regulation of NRG1 improves cardiac repair in zebra fish and involved in the cardioprotective effects of exercise training in rats of myocardial infarction

2021-02-28T16:44:45+00:00

Objective Myocardial infarction (MI) remains a leading cause of morbidity and mortality worldwide. Exercise training could improve cardiac function following MI. However, the mechanisms are still not well-known. Neuregulin 1 (NRG1)plays an important role in heart development and regeneration.In this study, we investigated the effect of NRG1 on cardiac regeneration in a zebrafish model, detected whether exercise could improve cardiac function through regulating NRG1 expression in infarcted heart and explore the possible role of up-regulation of NRG1 in skeletal muscle play in the cardioprotective effects in rats with MI.

Methods Transgenic zebrafish line, cmlc2:CreERandβ-act2:BSNrg1,wereusedto study the effect of NRG1 on heart growth and regeneration after injury. PCNA was detected by immunofluorescence staining andmRNAexpression of gata4, nkx2.5, tbx5, smyd1b, hsp90α and murf were tested by RT-PCR.Sprague-Dawley rats were used to establish MI model and underwent fourweeks of exercise training (ET) or pAAV-{dMCK promoter}rNRG1-eGFP intervention.AG1478 was used asan inhibitor of NRG1/ErbBs signaling pathway. Cardiac function and structure,cardiomyocyte proliferation and NRG1 expression were detected in the heart or skeletal.

Results Cardiac-specific overexpression of NRG1 induced cardiac hypertrophy and cardiomyocyte proliferation, regulated the mRNA expression of gata4, nkx2.5, tbx5, smyd1b, hsp90α andmurf in uninjuriedzebrafish, and promote cardiac repair and regeneration after injury in the zebrafish.Exercise activated NRG1/ErbBs signaling pathway, improved cardiac remodeling and heart function, enhanced cardiomyocyte proliferation, reduced cardiomyocyte apoptosis, ROS level and MuRF1 protein expression in rats with MI. BlockingErbB signaling attenuated the ET-induced cardioprotection effects in rat with MI.up-regulation of NRG1 expression in skeletal muscle could increase the protein level of NRG1 in serum and infarcted heart, improve cardiomyocyte proliferation and reduce the level of cardiac fibrosis, finally promote cardiac function.

Conclusions Up-regulation of NRG1 expression in the heart or skeletal musclemay be one of the underlying mechanisms of thebeneficial effects of exercise training following MI.

PL - 028 Aerobic exercise inhibits tau hyperphosphorylation through activation of the PI3K/Akt pathway in the hippocampus of APP/PS1 mice

2021-02-28T16:44:16+00:00

Objective Many studies suggest that regular physical exercise can reduce the risk of Alzheimer’s disease and slow its onset and progression. However, the exact mechanism is still unclear. Clinically, Alzheimer’s disease is characterized by the presence of extracellular amyloid plaques and intraneuronal neurofibrillary tangles, which are associated with amyloid-β and tau hyperphosphorylation respectively. The PI3K/Akt signaling pathway regulates tau phosphorylation and plays a pivotal role in the development of pathology in Alzheimer’s disease. Here we investigated the effects of aerobic exercise on tau phosphorylation and examined whether these effects were mediated by the PI3K/Akt pathway in the hippocampus of APP/PS1 transgenic mice.

Methods 40 male APP/PS1 transgenic mice were randomly divided into four groups: sedentary group (T-SE; n=10), exercise group (T-EX; n=10), sedentary with GNE-317 treatment group (T-SEG; n=10) and exercise with GNE-317 treatment group (T-EXG; n=10). GNE-317 is a potent and selective PI3K/Akt pathway inhibitor that can cross the blood-brain barrier and show effective suppression of Akt phosphorylation in the mice brain. The mice in the T-EX and T-EXG groups were given exercise training on a treadmill for 5 days/week for 8 weeks with 0% grade, and progressively ran from 30 min/day at 12 m/min, up to 60 min/day at 15 m/min. The mice in the T-SE and T-SEG groups were placed individually on another treadmill at 0 m/min for the same duration. 48 hours after the last exercise bout, all mice were intraperitoneally injected an anesthetic for inducing anesthesia, and the hippocampus were rapidly extracted. The protein and phosphorylation levels of tau, PI3K, Akt and GSK3β were assayed by Western blot and immunohistochemistry. The cognitive function were tested by morris water maze.

Results We found out that 8 weeks of aerobic exercise reduced tau phosphorylation at multiple sites including Ser202, Thr231 and Ser396, and increased phosphorylation of Akt at Thr308 and Ser473 and of GSK3β at Ser9. Furthermore, in the morris water maze test, the exercise group showed a reduced escape time and distance compared with those of the sedentary group, suggesting that aerobic exercise improved learning and cognitive ability. While the above-mentioned results were attenuated in the PI3K/Akt inhibitor GNE-317 treatment groups.

Conclusions Our study demonstrated that aerobic exercise could inhibit tau hyperphosphorylation and improve cognitive funtion through activation of the PI3K/Akt pathway in the hippocampus of APP/PS1 mice.

PL - 029 Responses of Urine and Blood Biochemical Markers to Exercise-induced Body Fluid Losses in Elite Chinese Road Cyclists

2021-02-28T16:43:47+00:00

Objective To examine biochemistry parameters regarding exercise induced fatigue, e.g. Sweat Loss (SL), Creatine Kinase (CK), Lactate Dehydrogenase (LDH), Blood Urinary Nitrogen (BUN), etc.

Methods This study examined Sweat Loss and blood biochemistry biomarkers regarding fatigue and muscle injury among elite cyclists under a training mode of 120 min moderate workload at 50 - 70% VO2max, then, 10 min relaxation, and then, followed up with a 20 min of spinning session over 85% VO2max. 12 healthy elite Chinese male cyclists (22.6 ± 2.9 years old, 78.3 ± 5.7 kg in weight, 184.6 ± 4.3 cm in height) were recruited. They performed four exercise performance tests throughout this study with 15 days washout period in between. Blood serum tests and urine tests were taken both pre- and post-exercise tests, and dynamic cardio-respiratory hardware (MetaMax 3B, Cortex Biophysik, Germany) was applied during each of their test. There were 2 different sport beverages available. The fluid replacement plan was a double blind crossover design. The volume of fluid intake was in accordance with ACSM recommendation for fluid replacement. Those who were assigned with sport beverage A (6% carbohydrate with 1% peptide) for the first and second performance tests, will be re-assigned to sport beverage B (6% carbohydrate without peptide) for the third and fourth performance tests, vice versa. Notes were taken for the volume of fluid intake to calculate the estimated Sweat Loss.

Results We found 91.7% trials have increased LDH, 88.9% trials have increased CK, and 100% trials have been observed increased BUN right after exercise performance test. Even with sufficient water supply, athletes hydration status were getting worse after exercise performance test, their urine USG results were 1.024 ± 0.006 and 1.027 ± 0.006 for pre- and post-exercise performance test respectively. Their dehydration status quantified by the percentage change in body mass (%BM) was 1.86% ± 1.03% with a 95% confidence interval ranging from 1.57% to 2.15%.

Conclusions Though, with sufficient water supply, athletes hydration status were getting worse after exercise performance test considering Sweat Loss and blood biochemistry indicators regarding fatigue and muscle injury.

PL - 030 The effects of ACE gene polymorphisms on ACE content before and after High-Intensity Interval Exercise

2021-02-28T16:43:14+00:00

Objective Angiotensin Converting Enzyme (ACE) is expressed in human skeletal muscle. The ACE I/D polymorphism (rs4341) has been associated with athletic performance in some studies. Studies suggested that the ACE I/D gene polymorphism is associated with ACE enzyme content in serum, however, the effect of ACE I/D on ACE protein content in human skeletal muscle in unclear. Angiotensin-converting enzyme 2 (ACE2) is a new component of the renin-angiotensin system (RAS), which is counter-regulatory to the ACE enzyme. The polymorphisms in the ACE2 gene (rs1978124 and rs2285666) have been reported to be associated with hypertension, however, their effects on ACE content in the blood and in skeletal muscle have yet to be explored. Utilising the Gene SMART cohort (n=81), we investigated whether the ACE I/D gene polymorphism (rs4341) and two ACE2 gene polymorphisms (rs1978124 and rs2285666) were associated with ACE enzyme content in the blood and skeletal muscle at baseline, and following a single session of High-Intensity Interval Exercise (HIIE).

Methods ACE and ACE2 gene polymorphisms were determined using the TaqMan SNP assay (Applied Biosystems, Foster City, California, United States) by Mastercycler® ep realplex2 (Eppendorf, Hamburg, Germany), and QuantStudio™ 7 Flex Real-Time PCR System (Applied Biosystems, Foster City, California, United States). For quantitation of ACE content in the plasma, Abcam Human ELISA Kit (ab119577 –ACE (CD143)) was used (Abcam, Cambridge, United Kingdom). Western blots were used to measure ACE content in skeletal muscle. We used robust linear models adjusted for age to test the effect of the ACE I/D polymorphism on outcomes at baseline, using the MASS package in the R statistical software. p-values were adjusted for multiple comparisons using the Benjamini and Hochberg method, and all reported p-values are adjusted p-values. An adjusted p value < 0.005 was considered significant.

Results We found that the ACE I/D gene polymorphism was associated with ACE content in the blood (p<0.005) at baseline, but not the ACE protein content in skeletal muscle at baseline. The ACE2 polymorphisms (rs1978124 and rs2285666) were not associated with ACE enzyme content in the blood or in skeletal muscle at baseline. A single session of HIIE tended (0.005 < p < 0.05) to increase blood ACE content immediately post exercise, while skeletal muscle ACE protein content was lower 3 hours post a single session of HIIE (p<0.005). However, those changes were not related to ACE I/D or ACE2 polymorphisms.

Conclusions The ACE I/D gene polymorphism influences ACE enzyme content in the blood but not the ACE protein content of human skeletal muscle. ACE I/D gene polymorphism does not influence the changes of ACE content after a single session of HIIE. ACE2 gene polymorphisms seem to have no effect on ACE content in the blood and skeletal muscle, before or after a session of HIIE.

PL - 031 Skeletal muscle blood flow determination using gold standard invasive arterial input function and non-invasive image-based input function by positron emission tomography (PET)

2021-02-28T16:42:46+00:00

Objective Skeletal muscle is unique among organs in that its blood flow, thus oxygen supply that is critical for muscular function, can change over a remarkably large range. Compared to the rest, muscle blood flow can increase over 20-fold during intense exercise. Positron emission tomography (PET) and [15O]-H2O tracer provide a unique tool for the direct measurement of muscle blood flow in specific muscle regions. Quantification of PET blood flow requires knowledge of the arterial input function, which is usually provided by arterial blood sampling. However, arterial sampling is an invasive approach requiring arterial cannulation. In the current study, we aimed to explore the analysis and error estimation based on non-invasive, PET image-based input function for skeletal muscle blood flow in PET [15O]-labeled radiowater study.

Methods Thirty healthy untrained men volunteered to participate in this study. [15O]-labeled radio water PET perfusion scans were performed at rest and right after cycling exercise. GE Discovery PET-CT scanner was used for image acquisition. The 15O isotope was produced with a Cyclone 3 cyclotron (IBA Molecular, Belgium). After 455 MBq of 15O-H2O was injected intravenously and after 20 seconds, dynamic scanning images were performed in following frames: 6x5 seconds, 12x10 seconds, 7x30 seconds and 12x10 seconds. Arterial blood was sampled continuously from radial artery during imaging for radioactivity with a detector during PET scanning. All the data analysis was performed using all in-house developed programs. Arterial input function was preprocessed with delay correction. Image-based input function was defined based on sum image of dynamic images. Blood flow was calculated using the 1-tissue compartment model, k1 is considered as blood flow without any further correction. All data analysis was performed by Carimas software (http://www.turkupetcentre.fi/carimas).

Data analysis was performed in five parts: 1) Modelling data using input function from artery. 2) By defining femoral artery Volume Of Interest (VOI) on PET images. 3) Modelling data using image-based input function. 4) Calculating the correlation for blood flow between artery (blood) input function and image-based input function. 5) Predicted true blood flow was calculated based on correlation based on the initial linear relationship between blood and image-based input functions.

Results Skeletal muscle blood flow had a good linear relationship calculated by femoral artery VOI and by arterial (blood) input function (y = 2,9587x - 0,096, R² = 0,8852, p<0.0001).

Further, by using the prediction equation obtained by the linear relationship between VOI-determined (femoral) artery blood flow and direct gold standard (radial) artery input function determined blood flow, image-based input function determined blood flow was well predicted using this non-invasive approach (y = 1,1812x + 0,1219, R² = 0,9259, p<0.0001).

Conclusions It is concluded that there is a strong linear correlation between gold standard invasive approach and non-invasive image-based approach to measure skeletal muscle blood flow by PET, but if no further corrections are made, image-based approach overestimates correct blood flow. However, this can be corrected by linear prediction equation, suggesting that invasive arterial input function may not always be needed in the future when measuring skeletal muscle blood flow by PET. This will be of benefit particularly for exercise studies.

PL - 032 Physiological triggers involved in reduced slow myosin expression in disused postural muscle

2021-02-28T16:42:17+00:00

Objective It is well known, that the reduced contractile activity of the postural soleus muscle under bedrest, immobilization or a space flight leads to decrease of slow myosin heavy chain (MyHC) expression rate and increase of the fast myosin isoforms expression [Pette, 2003; Stevens, 1999, 2000 et al]. The significant decline of the slow myosin mRNA content was found as early as after 24 hours of rat hindlimb unloading [Giger et al., 2009]. However, in the meantime, the mechanisms of this process had been substantially unexplored. At the same time, the main pathways involved in the control of transcription of Myh7 gene (MyHCIβ) are well known. These mechanisms are based upon traffic of messenger molecules (NFATc1 and Class IIA histone deacetylases) transducing positive and negative signals for Myh7 gene expression in muscle fiber nuclei. This traffic is known to be triggered by myoplasmic calcium content. Almost nothing is known about the roles of other physiological regulators (nitric oxide and high-energy phosphates) in Myh7 transcription control [Martins et al., 2012; Putman et al., 2015].

Our study was aimed to disclose the physiological triggers involved in the decline of Myh7 expression in postural muscle at the early stages of disuse state. We supposed that at the early stage of unloading (24 hours) it was the shift of the ATP/ADP/AMP balance (ATP accumulation due to muscle inactivation) to drive the Myh7 gene expression decline via AMP-activated protein kinase (AMPK) dephosphorylation and HDAC4 myonuclear import. Then we supposed that the mechanisms involved in the reduction of Myh7 expression during the first week of disuse are implemented via the decrease of NO muscle content [Lomonosova et al., 2011] and subsequent NFATc1 nuclear export in the GSK3β-dependent manner [Lomonosova et al, 2017].

Methods Three experimental series were performed in order to testify the hypotheses. Unloading of the hindlimbs was induced by using a standard rodent hindlimb suspension/unloading (HU) model (Morey-Holton & Globus, 2002). During the first series, using the selective AMPK activator AICAR we evaluated the roles of the AMPK dephosphorylation during the first days of unloading which we found earlier [Vilchinskaya et al., 2015; Mirzoev et al, 2016]. Animals were daily treated with AICAR (400 mg kg⁻¹) or saline for 6 days before HU as well as during 24 h of HU.

The second series was designed to investigate the impact of high-energy phosphates ratio changes on AMPK activity and slow-type MyHC isoform expression in rat soleus muscle at the early stages of unloading. It is known that administration of β-guanidin-propionic acid (βGPA) allows shifting ATP/ADP/AMP balance to the enhanced ATP breakdown. We used administration of β-guanidinopropionic acid (βGPA), before (6 day) and during 24-h HU.

The third series was aimed to identify the functional relationship between the decrease of the nitric oxide (NO) content, the GSK-3β phosphorylation (leading to the GSK-3β activation), the NFATc1 amount in the muscle nuclei, and the MyHC I(β) isoform expression in the rat soleus muscle under gravitational unloading. Male Wistar rats were divided into five groups: the vivarium control group; the group of animals with a 7-day hind limb suspension receiving placebo; the group of HU animals receiving a NO donor (L-arginine); the group of HU animals receiving a NO donor and a NO-synthase inhi bitor (L-NAME) and the group of HU animals receiving a GSK-3β inhibitor.

Results In the 1^st experimental series we discovered that AICAR treatment prevented a decrease in content of phospho-AMPK and pre-mRNA and mRNA expression of MyHC I as well as MyHC IIa mRNA expression. Twenty-four hours of HU resulted in HDAC4 accumulation in the nuclei of rat soleus but AICAR pretreatment prevented this accumulation. The results of the study indicate that AMPK dephosphorylation after 24 h of HU had a significant impact on the MyHC I and MyHC IIa mRNA expression in rat soleus. AMPK dephosphorylation also contributed to HDAC4 translocation to the nuclei of soleus muscle fibers, suggesting an important role of HDAC4 as an epigenetic regulator in the process of myosin phenotype transformation.

In the 2^nd experimental series after 24-h HS we observed a decrease (p<0.05) in phospho-AMPK content vs. control group, but in HS+ βGPA group didn’t differ from the control. After 24-h unloading we found a significant increase in the content of nuclear HDAC4 in the HS group, but in the HS+ βGPA group the content of nuclear HDAC4 didn’t differ from the control group. 24-h unloading resulted in a decrease in MyHCI(β) pre-mRNA and mRNA expression vs. the control group. The expression level of MyHCI(β) pre-mRNA and mRNA in HS+ βGPA group didn’t differ from the control. Thus, βGPA administration prevents a decline in AMPK phosphorylation. Therefore, we can conclude that at the early stage of gravitational unloading an accumulation of high-energy phosphates (ATP, ADP and creatine phosphate) may lead to reduced AMPK activity and a slow to fast myosin fiber type transition.

The third experimental series dealt with the fate of the nuclear NFATc1 transcription factor which triggers the myh7 expression but can be easily exported from myonuclei being phosphorylated. It is supposed that it is NO-dependent GSK3β that phosphorylates NFATc1 and promotes its nuclear export. We have shown that a 7-day unloading leads to a NO content decrease in the soleus muscle, and this effect is prevented by L-arginine administration. In addition, administration of L-arginine blocks the GSK-3β phosphorylation decrease, NFATc1 export from the muscle nuclei, and MyHC I(β) expression decrease caused by unloading. The NO-synthase inhibitor can block the L-arginine effect in each case. Administration of the GSK-3β inhibitor prevents the unloading-induced NFATc1 export from the muscle nuclei and a decrease of the MyHC I(β) expression.

Conclusions The data obtained in the described experimental series give evidence for the novel view on the well-known phenomenon of slow-to-fast fiber type transition during unloading/disuse. It is obvious that the signaling pathways involved in the slow myosin gene expression control during unloading are time-dependent and consecutive in the course of the exposure to unloading. The earliest triggering factor is supposedly the shift of the balance of high-energy mononucleotide phosphates leading to decrease of AMP and accumulation of ATP content. This signal is accepted by the AMPK as a universal energy sensor and transduced to the transcription level by the altered HDAC4 traffic. It seems possible that at the next stages of the exposure to unloading the alteration of the calcineurin/NFATc1 signaling pathway takes place due to the activated calcineurin inhibitors [Lomonosova et al, 2017] and enhanced NFATc1 phosphorylation and myonuclear export. We obtained the novel evidence that at these stages the decline of Myh7 expression might be provided by the GSK3β activation and NFATc1 phosphorylation due to the decrease of NO content in the soleus muscle.

The study was supported by Russian Science Foundation grant # 18-15-00107.

PL - 033 A translational model of muscle protein synthetic bioactivity in vitro, ex vivo and in vivo

2021-02-28T16:47:39+00:00

Objective The aim of this research was the development and validation of a translational model for the evaluation of exercise and nutrient stimulated muscle protein synthesis (MPS). To achieve this overall aim, three primary objectives had to be realised: (i) Development of an in vitro skeletal muscle cell bioassay to measure muscle growth and MPS; (ii) Development of an ex vivo model to evaluate the humoral effect on MPS in response to nutrient feeding and exercise; (iii) Use of a stable isotope technique to evaluate MPS in response to nutrient feeding and exercise in vivo.

Methods To develop a novel in vitro skeletal muscle cell bioassay to measure muscle growth and MPS, C2C12 myoblasts were proliferated and subsequently differentiated to myotubes over 8 days in DMEM (2% HS). Changes in cell behavior and adhesion properties were monitored by measuring impedance via interdigitated microelectrodes using the xCELLigence system. MPS was measured by puromycin incorporation using the SUnSET technique, intracellular signalling measured by western blot, and myotube thickness by microscopy. To demonstrate the capability to monitor nutrient regulation of muscle growth, media was conditioned with a known potent regulator of MPS (leucine) in a dose response experiment (0.20 - 2.0 mM). To establish the ability of the bioassay to measure the humoral effect of MPS in response to feeding and exercise, media was conditioned by ex vivo human serum from fasted, rested, fed (protein and isonitrogenous non-essential amino acid (NEAA) control) and post-exercise conditions. To evaluate MPS in response to nutrient feeding and exercise in vivo, acute MPS (5 h) was assessed by measuring stable isotope deuterium oxide (D₂O) incorporation into m. vastus lateralis skeletal muscle following consumption of either a Whey Protein (WP) or an isonitrogenous NEAA control combined with resistance exercise in resistance trained males.

Results In vitro experiments observed a dose-response effect with a 32 % increase in cell index and a 27 % increase in cell thickness after 2 h in the presence of 2.0 mM leucine when compared with control myotubes. Ex vivo serum following ingestion of NEAA had no effect on protein signalling or MPS whereas WP fed serum significantly increased mTOR, P70S6K and 4E-BP1 phosphorylation (p<0.01, p<0.05) compared to fasted serum. Furthermore, the effect of WP fed serum on protein signalling and MPS was significantly increased (p<0.01, p<0.05) compared to NEAA fed serum. Ex vivo human serum following resistance exercise was also increased MPS (29 %) and phosphorylation of mTOR (6 %), p70S6K (12 %) and 4EBP1 (7 %), compared with resting serum. These ex vivo/in vitro findings translated to the in vivo model as myofibrillar fractional synthetic rates (myoFSR) (Basal 0.068±0.002%h^-1 vs. WP 0.084±0.006 %h^-1, p=0.033) and absolute synthetic rates (ASR) (Basal 10.34±1.01 vs. WP 13.18±0.71 g.day^-1, p=0.026) were increased from basal levels only when resistance exercise was combined with WP ingestion and not the NEAA control (NEAA MPS 0.072±0.004%h^-1, NEAA ASR 10.23±0.80 g.day^-1). Thus, ingestion of WP in combination with resistance training augments acute MPS responses in resistance trained young men.

Conclusions We have developed a translational model of muscle protein synthetic bioactivity using in vitro, ex vivo and in vivo methodologies. We have shown that we can impact MPS in vitro using ex vivo human serum to condition media, that MPS in vitro is differentially regulated by ex vivo serum containing bioactive WP compared to a non-bioactive NEAA control, and that this tranlates for resistance exercise combined with WP in humans when MyoFSR is measured using stable isotope technology. These experiments demonstrate that ex vivo/in vitro experiments translate to the in vivo model and these methods can be used to inform both exercise and nutrient human interventions.

PL - 034 Impact of PM2.5 Exposures and Pre-exercise on Pulmonary Function and Leukocyte Count in Aged Rats

2021-02-28T16:41:48+00:00

Objective Exposure of PM2.5 has been associated with adverse respiratory and the risk of inflammation. While regular physical activity (PA) reduces the risk of many adverse health effects. This study aimed to examine the protection of pre-exercise on adverse health effects of Pulmonary Function and inflammatory induced by PM2.5 exposures in aged rats.

Methods 24 male wistar rats, aged 16 months, were randomly divided into 4 groups: Sedentary (S), Exercise (E), Sedentary+ PM2.5 exposures (S+PM), and Exercise+ PM2.5 exposures (E+PM). The rats in all E-related groups went through an aerobic treadmill exercise protocol (15m/min, 30 min) at every other day. The PM-related groups of aged rats were exposed to concentrated ambient particles of less than 2.5 μm (PM2.5) or filtered air (FA) in Beijing, for 4 hours per day, 7 days per week for a total of 2 weeks. After 2-week PM Exposure, blood was taken to measure the count of white blood cell (WC), neutrophil (NE), lymphocytes (LY), monocyte (MO), eosinophils (EO) and basophil (BA), and pulmonary function examined by whole body plethysmography.

Results After 2-week PM exposure, compared with E group, S+PM group’ s percentage of NE decreased significantly (p＜0.05), while the decline of NE% in E+PM group was small. Meanwhile, the obviously rise of BA% occurred in S+PM and E+PM group compared with sedentary group (p＜0.05). 2) Compared with E group, the Index of constriction (Penh and PAU) were increased evidently in S+PM group after PM exposure (p＜0.05), while the value of Penh were significantly improved in E+PM group (p＜0.05). 3) Compared with E group, the rejection index (RinX) (p＜0.01) and duration of pause before inspiration (TP) (p＜0.05) were appeared a clearly inclined in S+PM group, as well as several up-regulated of RinX and TP showed in E+PM group.

Conclusions 2-week PM2.5 exposures led to an increased susceptibility of infections, index of constriction and susceptibility of pulmonary function in aged rats. Moderate pre-exercise has beneficial effects on pulmonary function and immune function.

PL - 036 Interactive effects of exercise and metformin on lactic metabolism in type 2 diabetes

2020-09-07T15:43:45+00:00

Objective Lactic acidosis is typically caused by an imbalance in lactic metabolism. This may be attributed to several reasons and is usually a result of complex interactions. There may be an increased risk for lactic acidosis in type 2 diabetes mellitus (T2D) patients when metformin treatment and physical exercise are combined since both metformin and exercise acutely affect lactic metabolism. As timing of exercise following metformin ingestion may determine the magnitude of long-term metabolic adaptations, this study aimed to test the acute effects of exercise performed at different times following metformin ingestion on lactic metabolism in T2D patients with a randomized crossover time series study design.

Methods Participants were recruited from two clinical health-care centers in China using a two-step screening procedure. First, approximately 2 523 patients with T2D were screened from the local diabetes database and clinical outpatient registration with inclusion criteria being men and women (30–65 years old) diagnosed with T2D no more than 5 years ago and treated with metformin (maximal daily dose of 2000 mg). Out of 100 potential participants who met the inclusion criteria, 56 were interested and invited to a laboratory visit. Finally, 34 patients participated in the study and of those, 26 patients (14 women and 12 men, mean age = 53.8 ± 8.6 years) completed all testing procedures.

All patients visited the laboratory on 4 occasions, each separated by at least 48 hours. Initially a control visit was performed and consisted of metformin administration only (Metf) and a maximal incremental cycle ergometer test in the afternoon. Thereafter, all participants performed a high-intensity interval training session (HIIT, 3 minutes at 40% followed by 1 minute of 85% of maximum power output) 30 minutes (EX30), 60 minutes (EX60), and 90 minutes (EX90) post breakfast and metformin administration, respectively, in a randomized order.

Serum lactate and glucose concentrations were assessed enzymatically, while insulin was assessed by an electrochemiluminescence immunoassay and superoxide dismutase (SOD) activity was determined by spectrophotometry. Measurements were performed before breakfast as well as both before and immediately after each exercise bout. In addition, capillary blood glucose concentrations were measured immediately after sampling using Omron AS1 glucose test strips (HGM-114) and lactate concentrations were assessed by ARKRAY Lactate Pro 2 test strips throughout each measurement day. Dietary intake was standardized on the evening prior to each laboratory day as well as between 8:00 a.m. and 4:00 p.m. during each testing day. This trial is registered with ChiCTR-IOR-16008469 on 13^th of May 2016.

Results During all three-exercise sessions, the capillary lactate concentrations were signiﬁcantly increased to a similar extent. However, sixty minutes following metformin administration, serum lactate levels began to accumulate to the highest level, where 30% of patients showed lactate concentrations above resting values (≥2 mmol·L^-1). The increased lactate concentrations were statistically associated with increased glucose when exercise was performed 60 minutes post metformin administration (r=0.384, p=0.048). Furthermore, in EX60 and EX90 lactate concentrations were 19% and 8% higher, respectively, compared to EX30. In addition, we found that after exercise but not before exercise, the lactate level was positively correlated with SOD (EX30 r=0.478 and p=0.012, EX60 r=0.562 and p=0.002, EX90 r=0.562 and p=0.003, respectively).

Conclusions We found that the changes of lactate concentrations were related to the timing of exercise post meal and after metformin ingestion. Thus, timing of exercise appears to be an important factor to be considered when prescribing exercise for T2D patients treated with metformin. In the present study, the optimal timing of HIIT exercise was 30 minutes after metformin administration, which was indicated by a minimized fluctuation of both glucose and lactate levels in T2D patients. Our results also suggest that lactic metabolism and oxidative stress could be among the main underlying molecular mechanisms that elucidate the combinational therapy of exercise and metformin treatment on T2D. Since both acute exercise and metformin may induce opposite effects on ATP production and reactive oxygen species formation, it is important to conduct further studies in an attempt to define the “safe time” for exercise after metformin administration.

PL - 037 Effect of HiHiLo on autonomic nervous system and body functional status of excellent female rowers

2020-09-07T15:43:16+00:00

Objective 12 female rowing athletes of Shanghai as research object of this study. 7 weeks of hypoxic experiment will be carried out on the study subjects. Monitoring of HRV and functional indexes of athletes during this period. To explore the effect of 3 weeks of Living High Training High Training Low（HiHiLo） training of female rowers ANS and functional status, and discussion on the relationship between ANS and functional status of athletes in HiHiLo.

Methods 12 Shanghai elite female rowers for 3 weeks HiHiLo training. Simulated altitude from 2500m to 3200m, A total of seven weeks of HRV and biochemical function indexes were tested before and after hypoxia training. In addition, the HRV test of the athletes in a hypoxic exposure. According to the change characteristics of each index, analysis of the change of the athletes ANS in acute hypoxic exposure, and the evaluation of the effects of HiHiLo on ANS and functional status.

Results 1. The results of HRV test showed that there was no significant difference in time domain and frequency domain between normal condition and low oxygen environment, But SDNN in hypoxia environment in higher than normal environment, RMSSD slightly lower than the normal environment, indicate that hypoxic environment for athletes of cardiovascular ANS regulation will change and PSNS tension decreased; TP decreased and LF/HF increased, but the change was not significant. 2. The detection of the three stages of the athletes found that there were no significant changes in the indicators of HRV. However, the SDNN、RMSSD and PNN50 indexes showed a certain change trend, that settled low oxygen, time domain index increased, and in hypoxia exposure within three weeks are maintained at high levels and hypoxia after the end of each indicator of the level of decline, as well as the domain indexes, the frequency domain indexes HF、LF and LF/HF also showed obvious change tendency. 3. After the beginning of the experiment, Hb、RBC continued to rise, and after three weeks of hypoxia reached the highest value, compared with before the experiment was increased by 7.7%, 5%, RBC and the experiment was significantly different (p<0.05), Hct increased 5.3% after 3 weeks of hypoxia. Hypoxia after the end of the experiment, RBC, Hb and Hct showed a downward trend, at the end of experiment were decreased by 5%, 3.4%, 3.5%(p>0.05); In this experiment, the BU, CK of the Shanghai women`s rowing athletes at each stage in the normal range, there was no significant difference, but there is a clear trend of change; There was no significant difference in the T of the athletes in the seven week test, but the change trend is obvious. The C was significantly decreased (p<0.05) in the second week after hypoxia exposure, and the follow-up period was significantly lower than that before the experiment(p<0.05) at second weeks. T/C value was significantly increased in the second week of hypoxia (p<0.05), the trend of change is roughly the same as T. The correlation analysis between biochemical function index and HRV was found that the correlation coefficient between PNN50 and T/C was 0.672(p<0.05), before hypoxia, LF/HF and T/C were negatively correlated with -0.825(p<0.01), LF/HF and T correlation coefficient -0.789(p<0.01); During the 3 week HiHiLo training, CK was significantly correlated with SDNN, HF and LF, respectively, and the correlation coefficients were -0.425(p<0.05), -0.43(p<0.05), -0.496(p<0.01), LF/HF and T were negatively correlated with -0.42(p<0.05); The tracking period athletes T were significantly positively correlated with SDNN, RMSSD, PNN50, HF in HRV index, correlation coefficients were 0.378(p<0.05), 0.443(p<0.01), 0.341(p<0.05), 0.371(p<0.05). In addition, the correlation coefficient between PNN50 and C was 0.411(p<0.05).

Conclusions 1. The ANS of Shanghai female rowers will change in acute hypoxic exposure, SNS would be enhanced. 2. Three weeks of longer periods of hypoxia training will enable the athletes to enhance the PSNS activity of the ANS, and may make the ability of the regulating equilibrium state from SNS and PSNS, the changes of the ANS regulation of the athletes to the PSNS activity were enhanced, this may be the result of long time hypoxia stimulation and training, to a certain extent, it shows that the level of athletes` performance has been enhanced. 3. Functional status index of Shanghai women`s rowing athletes was well in 3 week HiHiLo training, Part of the improvement of the functional status indicators shows that the effect of the hypoxic training is obvious, The functional status of athletes showed a rising trend. 4. In the different stages of the experiment, there was a significant correlation between the HRV partial indexes and some biochemical indexes. This shows that there is a certain relationship between the ANS and functional status in the hypoxic training. Detection and evaluation of autonomic nervous function in hypoxic training can reflect the functional level of the body to a certain extent. This suggests that it is necessary to strengthen the research and application of ANS function evaluation in hypoxic training.

PL - 038 Habitual swimming exercise induced partial resistance to rat Alzheimer's disease

2020-09-07T15:42:47+00:00

Objective In MSSE, we have divided male 2.5-month-old Sprague-Dawley rats into the following 4 groups: control (C), habitual swimming (SW), Alzheimer’s disease (AD) induction without swimming (AD), and habitual swimming and then AD induction (SA), and found the perfect resistance of habitual swimming to AD induction by using the P value statistics of the 5 behavior parameters of rats and the 23 physiological and biochemical parameters of their hippocampus. The topological difference of four groups were further calculated in this paper by using quantitative difference (QD) and self-similar approach.

Methods 1. The logarithm to base golden section τ (lt) is called golden logarithm. It was found that σ=ltσ ≈ 0.710439287156503. 2. For a process from x₁ to x₂, l_x(1,2)=lt(x₂/x₁) and its absolute vale are called the process logarithm and its QD, QD_x(1,2). There are QD threshold values (α_x,β_x,γ_x) of function x which can be calculated in terms of σ. The function x is kept to be constant if QD_x(1,2) < α_x. A function in/far from its function-specific homeostasis is called a normal/dysfunctional function. A normal function can resist a disturbance under its threshold so that QD_x(1,2) < β_x. A dysfunctional function is defined as the QD is significant if β_x ≦QD_x(1,2) < γ_xand extraordinarily significant if QD_x(1,2) ≧ γ_x. 3. Self-similarity was studied in the fractal literature: a pattern is self-similar if it does not vary with spatial or temporal scale. First-order self-similarity condition leads to the power law between two data sets A = {x_i} and B = {y_i}_; y_i = a_i x_i if the QD_i of a_iand the average of {a_i} is smaller than β_min=min{β_i} and the average QD of {QD_i} is smaller than α_min=min{α_i}. 4. The σ algorithm for integrative biology was established based on high-order self-similarity. Those parameters that contribute to the topological difference were the biomarkers.

Results The 28 dimension data set consisted of all the 28 parameters. The first-order self-similarity held true for the 28 dimension data sets between groups C and SW. The topological algorithm of other groups suggested three AD biomarkers, protein carbonyl, granules density of presynaptic synaptophysin in the hippocampal CA1 and malondialdehyde intensity. The first two biomarkers were completely reversed by exercise pretreatment, but the third biomarker was partially reversed.

Conclusions Exercise pretraining exerts partial benefits on AD that support its use as a promising new therapeutic option for prevention of neurodegeneration in the elderly and/or AD population.

PL - 039 Heat Shock Proteins in human single skeletal muscle fibres resist age associated alterations and differentially respond to high-intensity exercise training

2020-07-26T15:33:40+00:00

Objective Heat shock proteins (HSPs) are ubiquitously expressed proteins that help preserve cellular homeostasis. Within mammalian skeletal muscle three of the better characterised HSPs are HSP72, HSP27 and αB-crystallin. Among other roles, these three HSPs are involved in regulation of muscle mass and function and may be of importance in ageing. HSP’s are fibre-type dependent in rat skeletal muscle and thus examining these proteins in humans should be completed on the single fibre level, particularly in ageing where maladaptations primarily occur in Type II fibres. High-Intensity Training (HIT) is a commonly used method to improve muscle health and function in the elderly, but HSP adaptability to training has not yet been investigated.

Methods This study examined isolated single muscle fibre segments collected from freeze-dried vastus lateralis muscle samples from young (25 /- 3 year old) and older (70 /- 4 year old) healthy individuals. A further sample was collected from the older individuals following 12 weeks of HIT, where they performed 4 x 4 min @ ~90-95% of peak heart rate (HR), with 4 min active recovery at 50-60% peak HR

Results Basal expression of HSP’s in skeletal muscle: HSP70 tended to be higher in Type I fibres compared to Type II in young adults (p=0.08) and was higher in Type I compared to Type II fibres of older adults (p=0.03). HSP27 abundance was higher in Type I fibres compared to Type II in young adults (p=0.01) and tended to be higher in Type I compared to Type II fibres in older adults (p=0.07). The abundance of αβ-crystallin was more abundant in Type I fibres compared to Type II in both young and older adults (p<0.05). Preliminary data revealed that the abundance of pABCser59 and pHSP2782 displayed no fibre-type specific abundances in either young or older adults.

Age effects on HSP’s: There was no difference in the abundance of HSP70, HSP27, ABC or pHSP2782 between young and older adults in either Type I or Type II fibres. There was an increase in the abundance of pABCser59 in Type I fibres in older adults compared to Type I fibres of young adults (p=0.03), with no difference in Type II fibres.

Effects of HIT on HSP’s: HIT in the older individuals increased the abundance of HSP70 in Type I fibres (p<0.01) but not Type II. HIT tended to decrease the abundance of HSP27 in Type I fibres (0.92±0.66, p=0.06) and tended to increase the abundance of αβ-crystallin in Type I fibres (1.03±1.51 p=0.07).

Conclusions These results revealed that in healthy, older individuals, the basal levels of HSP27, ABC or pHSP2782 are not different to those in young adults in either Type I or Type II fibres. This could indicate that the muscle from the older individuals was not compromised. Interestingly, in response to HIT there were varying changes between these HSP’s, and of note these occurred only in Type I fibres. Given that during HIT Type II fibres would be activated to a greater extent, it appears that the recovery phases of the HIT were most responsive to HSPs.

PL - 040 A Metabonomic Study on the Urine of Rowing Athletes

2020-07-26T15:33:11+00:00

Objective To extract information that affect sport performance, the technique of urine metabolism and quantitative difference（QD）analysis were combined in search of the characteristic metabolites of the rowing athletes.

Methods Morning urine were collected in three consecutive weeks, main peaks of the ¹H NMR spectrum which have significant difference between the medalists and non-medalists were selected from thousands of one dimensional NMR hydrogen spectrum of urine. Pattern recognition method based on metabonomics combined with QD so that the metabolites which could reflect the competitive level of the elite athletes could be selected from the main components.

Results 1.The optimal principal component of rowing athletes were principal component 1 and 5（PC1&PC5）. 2. Results of 7-fold cross validation showed that the PLS-DA model were stable, reliable and has good prediction ability. Results of the repeatability experiment showed that sample test accuracy were above 85%. 3. N-methylnicotinamide was obtained by multi-criteria assessment methods as the characteristic metabolite. 4. Substance concentration related to aerobic and anaerobic metabolism were different in urine of the rowing athletes.

Conclusions The athletes' urine contains the information of sport performance. Metabonomics combined with QD analysis could be widely applied in the evaluation of rowing athletes' competitive ability. The role of nicotinic acid in regulating energy metabolism and protecting human body might be a necessary condition with which athletes could tolerance high strength training and competition.

PL - 041 Effects of power resistance exercise and feeding on the expression of putative mechanosensing proteins in skeletal muscle of resistance-trained men

2020-07-26T15:32:42+00:00

Objective Power resistance exercise involves high intensity (load and velocity) dynamic muscular contractions and is frequently performed by athletes to enhance performance via improved muscle function. To investigate the remodelling processes that contribute to improved muscle function, we investigated the expression of putative mechanosensing genes implicated in this process (Kojic et al., 2011): titin-linked Muscle Ankyrin Repeat Protein (MARPs) family CARP, Ankrd 2 and DARP, and the Z-disc associated muscle-LIM protein (MLP) in healthy, resistance-trained men (n = 7) following 90 min of rest (Rest) or power resistance exercise, with (Ex + Meal) or without (Ex only) feeding during recovery.

Methods Percutaneous needle biopsy samples were obtained from the vastus lateralis of resistance-trained males using local anesthetic (2% Xylocaine), 3 h after performing each of the three experimental trials on separate days.

Previously, we presented results from this study showing that the mRNA levels of CARP (~15-fold) and MLP (~2.5-fold) were upregulated in human skeletal muscle 3 h post power resistance exercise (Wette et al., 2012). Based on these results, we performed protein analyses on the same muscle samples to determine the protein levels of all MARPs and MLP in whole muscle homogenates after Rest, Ex only and Ex + Meal. To assess whether the exercise elicited a stress response in these resistance-trained individuals, the level of phosphorylated heat shock protein 27 at serine 15 (pHSP27-Ser15) was measured at Rest and 3 h after Ex only and Ex + Meal. The levels of pHSP27-Ser15 are typically upregulated 3 h after eccentric exercise in human skeletal muscle (Frankenberg et al., 2014).

Results The 90 min exercise session consisted of 180 intermittent muscular contractions at high intensity (70-96% maximal strength). Compared to Rest, there were ~5.8- and 12.6-fold increases in pHSP27-Ser15 levels at 3 h post Ex only and Ex + Meal (both P = 0.049, one-way ANOVA) respectively. CARP protein levels were elevated ~2.7-fold after Ex only (P = 0.049, one-way ANOVA) and ~7.6-fold after Ex + Meal (P = 0.326), due to markedly higher levels (6-40-fold) in three of the seven participants. Pearson correlation analysis revealed a significant positive correlation between the levels of pHSP27-Ser-15 and CARP protein (r = 0.56, P = 0.008). Ankrd 2, DARP and MLP protein levels were unchanged (all P > 0.05) following Ex only and Ex + Meal.

Conclusions These findings indicate that CARP is highly responsive to increased mechanical loading because the protein levels in skeletal muscle can be substantially increased as early as 3 h after stressful resistance exercise. This suggests a specialised role for CARP protein during the early phases of muscle remodelling that occur as a consequence of performing high intensity resistance exercise.