BACKGROUND: In chronic heart failure (CHF) skeletal muscle insulin resistance occurs independently of etiology and contributes to impaired energy metabolism. GLUT4, the predominant glucose transporter in the skeletal muscle promotes the rate-limiting step of glucose utilization in skeletal muscle. The significance of skeletal muscle GLUT4 in patients with CHF has not been studied in detail. METHODS: In patients with CHF and free of diabetes mellitus (n=29; mean NYHA class 2.3+/-0.1, peak VO(2) 18.8+/-1.1 mL/kg/min) and healthy control subjects of similar age (n=7), GLUT4 protein was assessed from percutaneous skeletal muscle biopsies. Skeletal muscle insulin sensitivity was assessed by intravenous glucose tolerance testing using a minimal modeling technique. Body composition was analyzed by dual energy X-ray absorptiometry (DEXA) scanning. RESULTS: Skeletal muscle GLUT4 was lower in CHF patients than in controls (0.75+/-0.07 vs 1.24+/-0.19 density units, P0.2). Low GLUT4 predicted impaired insulin sensitivity, i.e. insulin resistance (r=0.55, P