Impaired insulin sensitivity and maximal responsiveness in older hypertensive men

This study examines the relation between blood pressure and insulin resistance in obese, sedentary middle-aged and older men. Eleven hypertensive and 17 normotensive subjects of comparable age (58.6 +/- 1.0 years, mean +/- SEM), percent body fat (27.7 +/- 0.7%), and maximal aerobic capacity (30.2 +/- 0.9 mL.kg-1.min-1) participated in this study. Glucose disposal (M, milligrams per kilogram of fat-free mass per minute) determined during a three-dose hyperinsulinemic euglycemic clamp was lower in the hypertensive than normotensive subjects at the low (M at 120 pmol/m2.min: 2.3 +/- 0.2 versus 3.2 +/- 0.3, P = .06), intermediate (M at 600 pmol/m2.min: 8.0 +/- 0.6 versus 10.4 +/- 0.6, P = .02), and high (M at 3000 pmol/m2.min: 13.5 +/- 0.5 versus 15.5 +/- 0.7, P = .04) insulin infusion rates. The calculated insulin concentration necessary for a half-maximal effect (EC50) was greater in the hypertensive than normotensive subjects (1164 +/- 168 versus 864 +/- 66 pmol/L, P = .03). In this population of normotensive and hypertensive men, systolic, diastolic, and mean arterial blood pressures were related to glucose disposal at these insulin infusion rates (r = -.35 to -.46, P < .05) as well as the EC50 (r = .42 to .44, P < .05). Thus, hypertensive obese, sedentary older men have a reduction in both sensitivity and maximal responsiveness to insulin that is directly related to the severity of hypertension independent of obesity and physical fitness.