Journal
PHYSIOLOGICAL REPORTS
Volume 6, Issue 19, Pages -Publisher
WILEY
DOI: 10.14814/phy2.13884
Keywords
Exercise physiology; fasting; fatty acid; glucose; liver; metabolism; skeletal muscle
Categories
Funding
- Japan Society for the Promotion of Science [24390194, 16H05294, 26461123, 17K09568]
- Japan Cardiovascular Foundation
- Gunma University Initiative for Advanced Research [140908272400]
- Japan Agency for Medical Research and Development [10030-14120]
- MSD Life Science Foundation [141602441000]
- Grants-in-Aid for Scientific Research [24390194, 16H05294, 17K09568, 26461123] Funding Source: KAKEN
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During fasting, most tissues including skeletal muscle heavily rely on utilization of fatty acids (FA) and minimize glucose use. In contrast, skeletal muscle prefers carbohydrate use as exercise intensity increases. In mice deficient for CD36 (CD36(-/-) mice), FA uptake is markedly reduced with a compensatory increase in glucose uptake in skeletal muscle even during fasting. In this study, we questioned how exercise endurance is affected during prolonged fasting in CD36(-/-) mice where glucose utilization is constantly increased. With or without a 24-h fast, a single bout of treadmill exercise was started at the speed of 10m/min, and the speed was progressively increased up to 30m/min until mice were exhausted. Running distance of wild type (WT) and CD36(-/-) mice was comparable in the fed state whereas that of CD36(-/-) mice was significantly reduced after a 24-h fast. Glycogen levels in liver and skeletal muscle were depleted both in WT and CD36(-/-) mice after a 24-h fast. In CD36(-/-) mice, FA uptake by skeletal muscle continued to be reduced during fasting. Glucose utilization also continued to be enhanced in the heart and oxidative skeletal muscle and glucose supply relative to its demand was diminished, resulting in accelerated hypoglycemia. Consequently, available energy substrates from serum and in muscle for exercise performance were very limited in CD36(-/-) mice during prolonged fasting, which could cause a remarkable reduction in exercise endurance. In conclusion, our study underscores the importance of CD36 for nutrient homeostasis to maintain exercise performance of skeletal muscle when nutrient supply is limited.
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