Several studies showed an increased risk for diabetes with statin treatment. PGC-1α is an important regulator of muscle energy metabolism and mitochondrial biogenesis. Since statins impair skeletal muscle PGC-1α expression and reduced PGC-1α expression has been observed in diabetic patients, we investigated the possibility that skeletal muscle PGC1α expression influences the effect of simvastatin on muscle glucose metabolism. Mice with muscle PGC-1α knockout (KO) or PGC-1α overexpression (OE), and wild-type (WT) mice were investigated. Mice were treated orally for 3 weeks with simvastatin (5 mg/kg/day) and investigated by intraperitoneal glucose tolerance (iGTT), in vivo skeletal muscle glucose uptake, muscle glycogen content, and Glut4 and hexokinase mRNA and protein expression. Simvastatin impaired glucose metabolism in WT mice, as manifested by increased glucose blood concentrations during the iGTT, decreased skeletal muscle glucose uptake and glycogen stores. KO mice showed impaired glucose homeostasis with increased blood glucose concentrations during the iGTT already without simvastatin treatment and simvastatin induced a decrease in skeletal muscle glucose uptake. In OE mice, simvastatin treatment increased blood glucose and insulin concentrations during the iGTT, and increased skeletal muscle glucose uptake, glycogen stores, and Glut4 and hexokinase protein expression. In conclusion, simvastatin impaired skeletal muscle insulin sensitivity in WT mice, while KO mice exhibited impaired skeletal muscle insulin sensitivity already in the absence of simvastatin. In OE mice, simvastatin augmented muscular glucose uptake but impaired whole-body insulin sensitivity. Thus, simvastatin affected glucose homeostasis depending on PGC-1α expression.
Keywords: Glut4; PGC-1α; glucose uptake; iGTT; insulin; simvastatin.