Effect of Acute Heat Stress on Muscle Glucose Metabolism
【Supercategory：7. DESCENTE SPORTS SCIENCE Subcategory：7.38 Vol.38】
ABSTRACT
Skeletal muscle is the major organ responsible for whole-body glucose metabolism and utilization. Heat stress (HS) has been implicated in the regulation of whole-body glucose homeostasis. Recently, we have demonstrated that short-term HS (for 10 and 30min) in vitro activates insulin-independent glucose transport, at least in part by stimulating 5'-AMP-activated protein kinase (AMPK) via decreased energy status in rat skeletal muscle. However, there have been no reports about the effect of acute HS (<30min) on glycogen and protein metabolism in skeletal muscle. The purpose of this study was to investigate the effect of short-term HS on glycogen and protein synthesis using rat skeletal muscle. Male Sprague-Dawley rats weighing 150g were killed by cervical dislocation without anesthesia, and epitrochlearis muscles were isolated. Muscle was then incubated in the absence or presence of HS (42℃, 30min) in alpha minimum essential medium containing 50μU/mL insulin. HS decreased glycogen content and activated glycogen synthesis with decreasing the phosphorylation of glycogen synthase kinase 3β, without affecting the phosphorylation of glycogen synthase. HS tended to decrease protein synthesis, and correspondingly, HS decreased the phosphorylation of p70 ribosomal protein S6 kinase and 4E-binding protein 1. On the other hand, HS did not affect the mRNA expression of muscle-specific ubiquitin ligases: muscle atrophy F-box/atrogin-1 and muscle ring finger 1, or protein expression of autophagy-related markers: microtubule-associated protein 1 light chain 3 and p62. In conclusion, short-term HS might be a physiologically relevant stimulus that promotes glucose transport/glycogen synthesis axis and inhibit protein synthesis in skeletal muscle. Although further study is warranted, HS has similar action to exercise by acutely activating glycogen synthesis and suppressing protein synthesis with a reduction of the glycogen content in skeletal muscle.
DESCENTE SPORTS SCIENCE Vol.38/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE
Skeletal muscle is the major organ responsible for whole-body glucose metabolism and utilization. Heat stress (HS) has been implicated in the regulation of whole-body glucose homeostasis. Recently, we have demonstrated that short-term HS (for 10 and 30min) in vitro activates insulin-independent glucose transport, at least in part by stimulating 5'-AMP-activated protein kinase (AMPK) via decreased energy status in rat skeletal muscle. However, there have been no reports about the effect of acute HS (<30min) on glycogen and protein metabolism in skeletal muscle. The purpose of this study was to investigate the effect of short-term HS on glycogen and protein synthesis using rat skeletal muscle. Male Sprague-Dawley rats weighing 150g were killed by cervical dislocation without anesthesia, and epitrochlearis muscles were isolated. Muscle was then incubated in the absence or presence of HS (42℃, 30min) in alpha minimum essential medium containing 50μU/mL insulin. HS decreased glycogen content and activated glycogen synthesis with decreasing the phosphorylation of glycogen synthase kinase 3β, without affecting the phosphorylation of glycogen synthase. HS tended to decrease protein synthesis, and correspondingly, HS decreased the phosphorylation of p70 ribosomal protein S6 kinase and 4E-binding protein 1. On the other hand, HS did not affect the mRNA expression of muscle-specific ubiquitin ligases: muscle atrophy F-box/atrogin-1 and muscle ring finger 1, or protein expression of autophagy-related markers: microtubule-associated protein 1 light chain 3 and p62. In conclusion, short-term HS might be a physiologically relevant stimulus that promotes glucose transport/glycogen synthesis axis and inhibit protein synthesis in skeletal muscle. Although further study is warranted, HS has similar action to exercise by acutely activating glycogen synthesis and suppressing protein synthesis with a reduction of the glycogen content in skeletal muscle.
DESCENTE SPORTS SCIENCE Vol.38/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE
| Researcher | Ayumi Goto*1, Tatsuro Egawa*2, Tatsuya Hayashi*2 |
|---|---|
| University or institution | *1 Graduate School of Human and Environmental Studies, Kyoto University Sportology Center, Graduate School of Medicine, Juntendo University, *2 Graduate School of Human and Environmental Studies, Kyoto University |
Keywords
skeletal muscle, heat stress, protein synthesis, glycogen synthesis, protein degradation