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The Effect Of Ischemic Preconditioning And Hypoxia On Neuromuscular Function During Intense Exercise

PURPOSE: The molecular regulation of peak fat oxidation (PFO) during exercise remains poorly characterized. The aim of this study was to examine the relationship between the content of key proteins involved in adipose tissue and skeletal muscle fat metabolism with PFO. METHODS: Thirty-six healthy men and women adults [15 females; mean (SD) age 40 (11) years; V O2peak 42.5 (9.5) mL·kg BM ·min; body fat %: 21.8 (8.2) %] completed two incremental exercise tests (separated by 7-28 days) to determine PFO via indirect calorimetry. A DEXA scan and adipose tissue and/or skeletal muscle biopsies were obtained 2-7 days after the second exercise test to determine the protein content of PLIN1, CGI-58, ATGL, HSL, ACSL1, and oestrogen receptor α (ERα) in adipose tissue, and FABPpm, ATGL, ACSL1, CTP1b and ERα in skeletal muscle. Sex comparisons were performed on sub-groups of males and females matched for aerobic capacity relative to fat free mass and classifications of the physical activity level index and fat mass index (n = 14 and 12 for adipose tissue and skeletal muscle comparison sub-groups, respectively). RESULTS: Moderate strength correlations were found between PFO (mg·kg FFM·min) and the protein content of ATGL [r = 0.41 (0.05 0.68), p < 0.05] and CPT1b [r = 0.41 (0.05 0.68), p < 0.05] in skeletal muscle. No other statistically significant bivariate correlations were found between PFO and the content of proteins in adipose tissue or skeletal muscle. Females had a greater PFO compared to males when expressed relative to fat-free mass [mean (SD): 7.1 (1.9) and 7.3 (1.7) vs 4.5 (1.3) and 4.8 (1.2) mg·kg FFM·min in the adipose tissue and skeletal muscle-sub-groups, respectively, p < 0.05]. No statistically significant sex differences were found in the content of any of the measured proteins involved in lipid metabolism in adipose tissue or skeletal muscle. CONCLUSIONS: The molecular regulation of PFO may primarily lie within skeletal muscle rather than adipose tissue, involving processes relating to intramyocellular triglyceride hydrolysis (ATGL) and mitochondrial fatty acid transport (CPT1b). Future studies should explore alternative molecular mechanisms that may account for sexual dimorphism in exercise fuel metabolism.