Exercise training increases insulin-stimulated glucose disposal and GLUT4 (SLC2A4) protein content in patients with type 2 diabetes

Abstract

Exercise enhances insulin-stimulated glucose transport in skeletal muscle through changes in signal transduction and gene expression. The aim of this study was to assess the impact of acute and short-term exercise training on whole-body insulin-mediated glucose disposal and signal transduction along the canonical insulin signalling cascade. A euglycaemic-hyperinsulinaemic clamp, with vastus lateralis skeletal muscle biopsies, was performed at baseline and 16 h after an acute bout of exercise and short-term exercise training (7 days) in obese non-diabetic (n=7) and obese type 2 diabetic (n=8) subjects. Insulin-mediated glucose disposal was unchanged following acute exercise in both groups. Short-term exercise training increased insulin-mediated glucose disposal in obese type 2 diabetic (p<0.05), but not in obese non-diabetic subjects. Insulin activation of (1) IRS1, (2) IRS2, (3) phosphotyrosine-associated phosphatidylinositol-3 kinase activity and (4) the substrate of phosphorylated Akt, AS160, a functional Rab GTPase activating protein important for GLUT4 (now known as solute carrier family 2 [facilitated glucose transporter], member 4 [SLC2A4]) translocation, was unchanged after acute or chronic exercise in either group. GLUT4 protein content was increased in obese type 2 diabetic subjects (p<0.05), but not in obese non-diabetic subjects following chronic exercise. Exercise training increased whole-body insulin-mediated glucose disposal in obese type 2 diabetic patients. These changes were independent of functional alterations in the insulin-signalling cascade and related to increased GLUT4 protein content.