Rosiglitazone, a thiazolidinedione, enhances peripheral insulin sensitivity in patients with type 2 diabetes. Because the synergic action of insulin and exercise has been shown to be decreased in insulin resistance, the aim of this study was to compare the effects of rosiglitazone and metformin on muscle insulin responsiveness at rest and during exercise in patients with type 2 diabetes. Therefore, 45 patients with newly diagnosed or diet-treated type 2 diabetes were randomized for treatment with rosiglitazone (4 mg b.i.d.), metformin (1 g b.i.d.), or placebo in a 26-week double-blind trial. Skeletal muscle glucose uptake was measured using fluorine-18-labeled fluoro-deoxy-glucose and positron emission tomography (PET) during euglycemic-hyperinsulinemic clamp and one-legged exercise before and after the treatment period. Rosiglitazone (P < 0.05) and metformin (P < 0.0001) treatment lowered the mean glycosylated hemoglobin. The skeletal muscle glucose uptake was increased by 38% (P < 0.01) and whole-body glucose uptake by 44% in the rosiglitazone group. Furthermore, the exercise-induced increment during insulin stimulation was enhanced by 99% (P < 0.0001). No changes were observed in skeletal muscle or whole-body insulin sensitivity in the metformin group. In conclusion, rosiglitazone but not metformin 1) improves insulin responsiveness in resting skeletal muscle and 2) doubles the insulin-stimulated glucose uptake rate during physical exercise in patients with type 2 diabetes. Our results suggest that rosiglitazone improves synergic action of insulin and exercise.
Address correspondence and reprint requests to Dr. Pirjo Nuutila, PhD, Turku PET Centre, University of Turku, PO Box 52, FIN-20521 Turku, Finland. E-mail:.
Received for publication 17 May 2002 and accepted in revised form 5 September 2002.
FFA, free fatty acid; [18F]FDG, fluorine-18-labeled fluoro-deoxy-glucose; [15O]H2O, oxygen-15-labeled water; [15O]O2, oxygen-15-labeled oxygen; PET, positron emission tomography; PI, phosphatidylinositol; PPAR, peroxisome proliferator-activated receptor; t1/2, half-life; TZD, thiazolidinedione.