The effect of a bout of resistance exercise on skeletal muscle protein metabolism after severe fasting

Resistance exercise (RE) activates the mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway and increases muscle protein synthesis. Severe fasting induces 5′ adenosine monophosphate‐activated protein kinase (AMPK), which attenuates mTORC1 activation. However, the effect of RE on the response of mTORC1 signaling proteins after a period of severe fasting is unclear. We investigated the effect of RE on rat skeletal muscle protein metabolism after a period of severe fasting. We hypothesized that RE‐induced activation of mTORC1 signaling protein attenuates protein breakdown by autophagy. Male Sprague‐Dawley rats were divided into ordinary‐fed (C) and 72‐h fasting (F) groups. A bout of RE was replicated by percutaneous electrical stimulation in the right gastrocnemius muscle. The tuberous sclerosis complex 2 (TSC2) Ser1387 and autophagy marker of microtubule‐associated protein 1A/1B‐light chain 3‐II (LC3B‐II) expression of the F group increased twice that of the C group in sedentary state (P < 0.05). RE activated the mTORC1 signaling pathway in both groups (P < 0.05); however, in the F group, the magnitude of p70S6K (Thr389) phosphorylation was lower by 40% of that of the C group (P < 0.05). Protein synthesis after RE was increased by 50% from the level at sedentary state in the C group (P < 0.05), but not in the F. In the F group, the expression of LC3B‐II at 3 h after RE was decreased by almost 25% from the level at sedentary state (P < 0.05). Our results suggest that RE suppressed fasting‐induced autophagy but did not increase protein synthesis during severe fasting in rat skeletal muscle.