Moderate GLUT4 Overexpression Improves Insulin Sensitivity and Fasting Triglyceridemia in High-Fat Diet–Fed Transgenic Mice

Abstract

The GLUT4 facilitative glucose transporter mediates insulin-dependent glucose uptake. We tested the hypothesis that moderate overexpression of human GLUT4 in mice, under the regulation of the human GLUT4 promoter, can prevent the hyperinsulinemia that results from obesity. Transgenic mice engineered to express the human GLUT4 gene and promoter (hGLUT4 TG) and their nontransgenic counterparts (NT) were fed either a control diet (CD) or a high-fat diet (HFD) for up to 10 weeks. Homeostasis model assessment of insulin resistance scores revealed that hGLUT4 TG mice fed an HFD remained highly insulin sensitive. The presence of the GLUT4 transgene did not completely prevent the metabolic adaptations to HFD. For example, HFD resulted in loss of dynamic regulation of the expression of several metabolic genes in the livers of fasted and refed NT and hGLUT4 TG mice. The hGLUT4 TG mice fed a CD showed no feeding-dependent regulation of SREBP-1c and fatty acid synthase (FAS) mRNA expression in the transition from the fasted to the fed state. Similarly, HFD altered the response of SREBP-1c and FAS mRNA expression to feeding in both strains. These changes in hepatic gene expression were accompanied by increased nuclear phospho-CREB in refed mice. Taken together, a moderate increase in expression of GLUT4 is a good target for treatment of insulin resistance.