Increased FXYD1 and PGC-1 mRNA after blood flow-restricted running is related to fibre type-specific AMPK signalling and oxidative stress in human muscle

AimThis study explored the effects of blood flow restriction (BFR) on mRNA responses of PGC-1 (total, 11, and 14) and Na+,K+-ATPase isoforms (NKA; (1-3), (1-3), and FXYD1) to an interval running session and determined whether these effects were related to increased oxidative stress, hypoxia, and fibre type-specific AMPK and CaMKII signalling, in human skeletal muscle. MethodsIn a randomized, crossover fashion, 8 healthy men (265year and 57.46.3mLkg(-1)min(-1)) completed 3 exercise sessions: without (CON) or with blood flow restriction (BFR), or in systemic hypoxia (HYP, 3250m). A muscle sample was collected before (Pre) and after exercise (+0hour, +3hours) to quantify mRNA, indicators of oxidative stress (HSP27 protein in type I and II fibres, and catalase and HSP70 mRNA), metabolites, and -AMPK Thr(172)/-AMPK, ACC Ser(221)/ACC, CaMKII Thr(287)/CaMKII, and PLBSer(16)/PLB ratios in type I and II fibres. ResultsMuscle hypoxia (assessed by near-infrared spectroscopy) was matched between BFR and HYP, which was higher than CON (90% vs 70%; P<.05). The mRNA levels of FXYD1 and PGC-1 isoforms (11 and 14) increased in BFR only (P<.05) and were associated with increases in indicators of oxidative stress and type I fibre ACC Ser(221)/ACC ratio, but dissociated from muscle hypoxia, lactate, and CaMKII signalling. ConclusionBlood flow restriction augmented exercise-induced increases in muscle FXYD1 and PGC-1 mRNA in men. This effect was related to increased oxidative stress and fibre type-dependent AMPK signalling, but unrelated to the severity of muscle hypoxia, lactate accumulation, and modulation of fibre type-specific CaMKII signalling.