Abstract
In this study we compared fatty acid (FA) metabolism in myotubes established from athletic and sedentary young subjects. Six healthy sedentary (maximal oxygen uptake (VO2max) ≤ 46 ml/kg/min) and six healthy athletic (VO2max > 60 ml/kg/min) young men were included. Myoblasts were cultured and differentiated to myotubes from satellite cells isolated from biopsy of musculus vastus lateralis. FA metabolism was studied in myotubes using [14C]oleic acid. Lipid distribution was assessed by thin layer chromatography, and FA accumulation, lipolysis and re-esterification were measured by scintillation proximity assay. Gene and protein expressions were studied. Myotubes from athletic subjects showed lower FA accumulation, lower incorporation of FA into total lipids, triacylglycerol (TAG), diacylglycerol and cholesteryl ester, higher TAG-related lipolysis and re-esterification, and higher complete oxidation and incomplete β-oxidation of FA compared to myotubes from sedentary subjects. mRNA expression of the mitochondrial electron transport chain complex III gene UQCRB was higher in cells from athletic compared to sedentary. Myotubes established from athletic subjects have higher lipid turnover and oxidation compared to myotubes from sedentary subjects. Our findings suggest that cultured myotubes retain some of the phenotypic traits of their donors.
Highlights
Skeletal muscle cells store glucose as glycogen and fatty acids (FAs) in triacylglycerol (TAG)-containing lipid droplets (LDs)[1,2,3,4,5,6]
Lipid distribution after the 24 h showed that myotubes from athletic subjects had reduced incorporation of [14C]oleic acid into DAG, TAG and cholesteryl ester (CE), as well as total cellular lipids compared to myotubes from sedentary subjects (Fig. 1b)
In this study we showed that myotubes established from young athletic subjects accumulated less oleic acid compared to myotubes from sedentary subjects
Summary
Skeletal muscle cells store glucose as glycogen and fatty acids (FAs) in triacylglycerol (TAG)-containing lipid droplets (LDs)[1,2,3,4,5,6]. It has been hypothesized that there is a better interaction between LDs and mitochondria in endurance-trained subjects than sedentary untrained[10]. An earlier report showed that with increasing delivery of free fatty acids (FFAs) to muscle, plasma FFA uptake and oxidation increased in trained subjects during prolonged thigh exercise, whereas untrained reached a plateau[16]. We have previously described, using cultured skeletal muscle cells from the same athletic (maximal oxygen uptake, VO2max > 60 ml/kg/min) and sedentary (VO2max ≤ 46 ml/kg/min) subjects as in the current work, that myotubes from athletic subjects showed higher deoxyglucose accumulation and fractional glucose oxidation.
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