Deterioration of Insulin Sensitivity and Glucose Effectiveness With Age and Hypertension

Background This study examined the relative role of age and hypertension in deterioration of insulin-dependent (insulin sensitivity, SI) and insulin-independent (glucose effectiveness, SG) actions on glucose tolerance. Methods We applied the minimal model of glucose kinetics to estimate SI and SG indexes from insulinemia and glycemia data detected during a frequently sampled intravenous glucose tolerance test performed in 21 normoglycemic subjects who were not affected by the metabolic syndrome (MS): seven young normotensive subjects (YN; mean age 29.3 ± 1.5 years), six elderly normotensive subjects (EN; mean age 57.0 ± 3.4 years) and eight elderly hypertensive patients (EH; mean age 62.1 ± 2.1 years). Results Both normotensive subject groups (YN and EN) showed no significant difference in SI estimates despite significantly different age, whereas a significant reduction was evident in the EH patients compared with these groups. Mean estimates of SG showed no significant difference in elderly subject groups (EN and EH), irrespective of hypertension, whereas a significant increase was evident in the YN (analysis of variance followed by Scheffé test, P< .05). Conclusions Our study demonstrates that, in the absence of MS: 1) insulin sensitivity in normotensive subjects is independent of age; b) hypertension is associated with insulin resistance in elderly subjects; and c) age is a primary predictor of deterioration in glucose effectiveness, independent of hypertension.