Incubation with sodium nitrite attenuates fatigue development in intact single mouse fibres at physiological PO2

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordDietary nitrate (NO3−) supplementation, which increases plasma nitrite (NO2−) concentration, has been reported to attenuate skeletal muscle fatigue development. Sarcoplasmic reticulum (SR) calcium (Ca2+) release is enhanced in isolated single skeletal muscle fibres following NO3− supplementation or NO2− incubation at a supra‐physiological PO2 but it is unclear whether NO2− incubation can alter Ca2+ handling and fatigue development at a near‐physiological PO2. We hypothesised that NO2− treatment would improve Ca2+ handling and delay fatigue at a physiological PO2 in intact single mouse skeletal muscle fibres. Each muscle fibre was perfused with Tyrode's solution pre‐equilibrated with either 20% (PO2∼150 Torr) or 2% O2 (PO2 = 15.6 Torr) in the absence and presence of 100 µM NaNO2. At supra‐physiological PO2 (i.e. 20% O2), time to fatigue was lowered by 34% with NaNO2 (control: 257 ± 94 vs. NaNO2: 159 ± 46 s, d = 1.63, P0.05) but [Ca2+]c accumulation between contractions was lower, concomitant with a greater SR Ca2+ pumping rate (P<0.05) compared to the control condition. These results demonstrate that increased exposure to NO2− blunts fatigue development at near‐physiological, but not at supra‐physiological, PO2 through enhancing SR Ca2+ pumping rate in single skeletal muscle fibres. These findings extend our understanding of the mechanisms by which increased NO2− exposure can mitigate skeletal muscle fatigue development.Ministry of Science, Technology and InnovationConselho Nacional de Desenvolvimento Científico e Tecnológico (National Council for Scientific and Technological Development)US Department of Health and Human Services (HHS)National Institutes of Health (NIH)National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS

Global proteome changes in the rat diaphragm induced by endurance exercise training

Mechanical ventilation (MV) is a life-saving intervention for many critically ill patients. Unfor- tunately, prolonged MV results in the rapid development of diaphragmatic atrophy and weakness. Importantly, endurance exercise training results in a diaphragmatic phenotype that is protected against ventilator-induced diaphragmatic atrophy and weakness. The mechanisms responsible for this exercise-induced protection against ventilator-induced dia- phragmatic atrophy remain unknown. Therefore, to investigate exercise-induced changes in diaphragm muscle proteins, we compared the diaphragmatic proteome from sedentary and exercise-trained rats. Specifically, using label-free liquid chromatography-mass spectrome- try, we performed a proteomics analysis of both soluble proteins and mitochondrial proteins isolated from diaphragm muscle. The total number of diaphragm proteins profiled in the sol- uble protein fraction and mitochondrial protein fraction were 813 and 732, respectively. Endurance exercise training significantly (P<0.05, FDR <10%) altered the abundance of 70 proteins in the soluble diaphragm proteome and 25 proteins of the mitochondrial proteome. In particular, key cytoprotective proteins that increased in relative abundance following exer- cise training included mitochondrial fission process 1 (Mtfp1; MTP18), 3-mercaptopyruvate sulfurtransferase (3MPST), microsomal glutathione S-transferase 3 (Mgst3; GST-III), and heat shock protein 70 kDa protein 1A/1B (HSP70). While these proteins are known to be cytoprotective in several cell types, the cyto-protective roles of these proteins have yet to be fully elucidated in diaphragm muscle fibers. Based upon these important findings, future experiments can now determine which of these diaphragmatic proteins are sufficient and/or required to promote exercise-induced protection against inactivity-induced muscle atrophy

Adequacies of skin puncture for evaluating biochemical and hematological blood parameters in athletes

Objective: The authors tested the effect of blood sampling (skin versus venous puncture) on some biochemical and hematological blood parameters in athletes to answer whether skin puncture could be used as a substitute for venous puncture. Design: Comparative study of 2 methods of blood samples collection. Setting: The blood was collected in the same athletes at 3 different moments of the preparatory training phase. Participants: Fourteen male indoor soccer players (22 +/- 1 years old) and 7 female handball players (18 +/- 1 years old) participated. Main Outcome Measurement: Blood was collected in heparin and K(3)EDTA by Vacutainer BD or Microvette Sarstedt system for biochemical and hematological analyses, respectively. Results: There were no significant statistical differences between the 2 methods for the values of creatine kinase, urea, creatinine, lymphocytes, and platelets. The other hematological analyzes and uric acid exhibited significant higher values in skin blood, although they were all within the normal expected range. A high degree of correlation was observed between the 2 techniques for all parameters. Conclusions: Skin puncture is a reliable, easy, accurate, and less invasive sampling method for assessing hematological and some biochemical parameters in athletes, respecting that blood samples should always be obtained from the same site, especially in follow-up studies.16541842

High-intensity ultraendurance promotes early release of muscle injury markers

Objective: To evaluate the impact of high-intensity ultraendurance (HIU) cycling, using it as a possible way to understand muscle injury kinetics and blood immune cells' release during high-intensity prolonged exercise Design: Male amateur triathletes enrolled during a cycling race of the International Bike Championship 800 km cycling relay (similar to 23 h). Each athlete alternately cycled 20-25 minutes until exhaustion and performed a total of approximately 200 km. Results: Creatine kinase levels in blood reached a 300% rise in a sigmoidal pattern, while lactate dehydrogenase levels increased by 30-40% following a hyperbolic pattern. Aspartate aminotransferase and alanine aminotransferase levels increased by up to 250% and 140%, respectively. Liver injury markers such as alkaline phosphatase and gamma-glutamyltransferase remained stable. Platelets increased by 20-30% from pre-exercise, and there was no change in haematocrit during the race. White blood cells rose by nearly 200%. Leucocytes rose 210% during the race, with a major component coming from neutrophils, which increased more than 300%. Triacylglycerol levels were decreased at the finish and total cholesterol levels remained unchanged. Urate increased (by up to 35%) during the first half of the race, and urea levels increased with a different pattern, increasing by 45% in the second half. Conclusions: This study showed the blood appearance kinetics of muscle injury markers and some metabolites. It is suggested that the increase in these enzymes came primarily from muscle damage, rather than liver damage, and that white blood cells are selectively mobilised independently of haemoconcentration. The early appearance of muscle injury markers in this kind of exercise was also shown.421188989