Reduced carbohydrate availability does not modulate training-induced heat shock protein adaptations but does upregulate oxidative enzyme activity in human skeletal muscle

Mar 7, 2009Journal of applied physiology (Bethesda, Md. : 1985)

Lower carbohydrate levels do not change heat shock protein responses to training but increase energy enzyme activity in human muscles

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Abstract

Training under reduced carbohydrate availability resulted in significant increases in succinate dehydrogenase activity of skeletal muscle, with 76% and 70% increases in the gastrocnemius and vastus lateralis, respectively.

Training for 6 weeks improved maximal oxygen uptake (Vo(2max)) and performance on a specific endurance test in all groups, with no differences observed between carbohydrate conditions.
Significant increases in heat shock proteins HSP70, HSP60, and alphaB-crystallin were noted in both gastrocnemius and vastus lateralis muscles across all groups, with no differences based on carbohydrate availability.
Increased succinate dehydrogenase (SDH) activity was observed in the gastrocnemius and vastus lateralis muscles for all training conditions, with the highest increases seen in the Low + Pla group.
Reduced carbohydrate availability appears to enhance oxidative enzyme adaptations in skeletal muscle, although this did not lead to improved performance in high-intensity exercise.

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The primary aim of the present study was to test the hypothesis that training with reduced carbohydrate availability from both endogenous and exogenous sources provides an enhanced stimulus for training-induced heat shock protein (HSP) adaptations of skeletal muscle. A secondary aim was to investigate the influence of reduced carbohydrate availability on oxidative adaptations and exercise performance. Three groups of recreationally active men performed 6 wk of high-intensity intermittent running occurring four times per week. Group 1 (n = 8; Low + Glu) and 2 (n = 7; Low + Pla) trained twice per day, 2 days/wk, and consumed a 6.4% glucose or placebo solution, respectively, immediately before every second training session and at regular intervals throughout exercise. Group 3 (n = 8; Norm) trained once per day, 4 days/wk, and consumed no beverage throughout training. Training induced significant improvements in maximal oxygen uptake (Vo(2max)) (P = 0.001) and distance covered on Yo-Yo Intermittent Recovery Test 2 (P = 0.001) in all groups, with no difference between conditions. Similarly, training resulted in significant increases in HSP70, HSP60, and alphaB-crystallin in the gastrocnemius (P = 0.03, 0.02, and 0.01, respectively) and vastus lateralis (P = 0.01, 0.02, and 0.003, respectively) muscles in all groups, with no difference between conditions. In contrast, training resulted in significant increases in succinate dehydrogenase (SDH) activity of the gastrocnemeius (Low + Glu, Low + Pla, and Norm: 27, 76, and 53% increases, respectively; P = 0.001) and vastus lateralis muscles (Low + Glu, Low + Pla, and Norm: 17, 70, and 19% increases, respectively; P = 0.001) where the magnitude of increase in SDH activity was significantly larger for both muscles (P = 0.03 and 0.04 for gastrocnemius and vastus lateralis, respectively) for subjects training in the Low + Pla condition. Data provide the first evidence that in whole body exercise conditions, carbohydrate availability appears to have no modulating effect on training-induced increases of the HSP content of skeletal muscle. In contrast, training under conditions of reduced carbohydrate availability from both endogenous and exogenous sources provides an enhanced stimulus for inducing oxidative enzyme adaptations of skeletal muscle although this does not translate to improved performance during high-intensity exercise.

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Reduced carbohydrate availability does not modulate training-induced heat shock protein adaptations but does upregulate oxidative enzyme activity in human skeletal muscle

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