The effect of treatment with enalapril versus losartan on levels of insulin resistance in patients with essential hypertension

Insulin resistance and hyperinsulinaemia are presumed to participate in the pathogenesis of essential hypertension (EH). Insulin resistance is characterised by an impaired insulin-mediated glucose uptake. Participation of the renin-angiotensin system in the development of hyperinsulinaemia in EH patients has not been unanimously proven. The present study aimed to asses the influence of antihypertensive therapy with angiotensin converting enzyme inhibitor (ACEI, enalapril = 10 mg/day) (9 male patients) or angiotensin II AT-1 receptor blocker (A II RB = losartan 50 mg/day) (9 male patients) respectively on insulin sensitivity in patients with EH. 3-hours euglycaemic clamp test with constant infusion of insulin (50 mU/m2/min) was performed twice: before and after 8 weeks of therapy with ACEI or A II RB respectively. The control group (CG) consisted of 12 healthy males (clamp test was performed once). Serum insulin concentration (I) was estimated by radioimmunoassay. Glucose disposal rate (M-value = mg/kg/min) and tissue insulin sensitivity (M/I value = mg/kg/min per mU/l) were calculated in subjects of the CG and in patients with EH before and after antihypertensive therapy with ACEI or A II RB, respectively. In CG the M-value (7.38 +/- 0.13) and tissue insulin sensitivity (M/I = = 6.76 +/- 0.19) were significantly higher than in EH before treatment with ACEI (M-value = 5.44 +/- 0.16; M/I = = 4.57 +/- 0.18) or A II RB (M-value = 5.75 +/- 0.21; M/I = 4.77 +/- 0.31), respectively. ACEI therapy was followed by a significant increase of both M (6.82 +/- 0.25) and M/I (5.68 +/- 0.25) values. In contrast to ACEI, treatment with A II RB did not influence neither M (5.75 +/- 0.21) nor M/I (4.79 +/- 0.21) values respectively. In contrast to A II RB, ACEI shows a beneficial effect on insulin sensitivity in EH patients. This effect does not seem to be mediated by an influence on the AT-1 receptor.