The mechanisms of insulin sensitivity improving effects of angiotensin converting enzyme inhibitor

It is well-known that angiotensin converting enzyme (ACE) inhibitor not onl y decreases blood pressure (BP) but also improves insulin sensitivity. To e lucidate the mechanisms of these actions of ACE inhibitor, we evaluated its effect on both BP and insulin sensitivity (M-value) as estimated by the gl ucose clamp technique in essential hypertensives in comparison with the eff ect of angiotensin receptor (AT) antagonist. We also evaluated the effect o f ACE inhibitor on BP, M-value and muscle fiber composition in fructose-fed rats (FFR) as an insulin-resistant hypertensive model with or without trea tment with Hoe 140 (kinin receptor antagonist). In essential hypertensives, both ACE inhibitor and AT antagonist decreased BP and improved insulin sen sitivity to the same extent. In FFR, ACE inhibitor also decreased BP and im proved insulin sensitivity. Moreover, Hoe 140 showed no effect on these act ions of ACE inhibitor. The composite ratio of type I fiber of soleus muscle was decreased significantly in FFR compared to control and ACE inhibitor p roduced a recovery of the composite ratio of type I fiber to the same as co ntrol. These results suggested that muscle fiber composition of skeletal mu scle is Linked to insulin resistance, and that ACE inhibitor may modulate m uscle fiber composition through its vasodilative effect in hypertension. Th ese results also suggest that for vasodilation, it is more important to inh ibit angiotensin II than to block degradation of kinins or to improve insul in sensitivity by ACE inhibitor. (C) 1999 Elsevier Science B.V. All rights reserved.