Skeletal muscle is an insulin sensitive tissue and accounts for approximately 80% of post-prandial glucose disposal. This study describes the effects of insulin, delivered for 72 h, to skeletal muscle myoblasts during differentiation or to skeletal muscle myotubes. After chronic treatment, cultures were acutely stimulated with insulin and analyzed for total and phosphorylated Akt (Ser473 ), mRNA expression of metabolic and myogenic markers and insulin-stimulated glucose uptake. Skeletal muscle cells differentiated in the presence of insulin chronically, reduced acute insulin stimulated phosphorylation of Akt Ser473 . In addition, there was a reduction in mRNA expression of Hexokinase II (HKII), GLUT4 and PGC-1α. Insulin-stimulated glucose uptake was attenuated when cells were differentiated in the presence of insulin. In contrast, myotubes exposed to chronic insulin showed no alterations in phosphorylation of Akt Ser473 . Both HKII and GLUT4 mRNA expression were reduced by chronic exposure to insulin; while PGC-1α was not different between culture conditions and was increased by acute insulin stimulation. These data suggest that there are differential responses in insulin signalling, transcription, and glucose uptake of skeletal muscle cells when cultured in either the presence of insulin during differentiation or in myotube cultures.
Keywords: differentiation; glucose uptake; hyperinsulineamia; insulin signalling.
© 2018 Wiley Periodicals, Inc.