Glucose Transport Activity in Insulin-Resistant Rat Muscle: Effects of Angiotensin-Converting Enzyme Inhibitors and Bradykinin Antagonism

Insulin resistance of skeletal muscle glucose disposal underlies the pathogenesis of NIDDM and is associated with hypertension, obesity, and dyslipidemia. Angiotensin-converting enzyme (ACE) inhibitors are used primarily in antihypertensive therapy but also are known to improve whole-body insulin-mediated glucose disposal. However, the exact site of action is not well characterized. We have used the isolated epitrochlearis muscle from a well-established animal model of skeletal muscle insulin resistance, the obese Zucker rat, to test the effect of oral administration of ACE inhibitors on insulin-sensitive muscle glucose transport activity. Both acute and chronic administration of a sulfhydiyl-containing ACE inhibitor (captopril) or a non–sulfhydryl-containing ACE inhibitor (tran-dolapril) significantly enhanced in vitro insulin-mediated muscle glucose transport activity. In addition, the acute effect of oral captopril administration was completely abolished by pretreatment of the animal with a bradykinin B₂ receptor antagonist (HOE 140). These findings indicate that ACE inhibitors may improve whole-body glucose metabolism by acting on the insulinsensitive skeletal muscle glucose transport system. In addition, bradykinin or one of its metabolites may be involved in the action of the ACE inhibitor captopril on insulin-resistant muscle.