Deterioration of insulin sensitivity effectiveness with and glucose age and hypertension

Background: This study examined the relative role of age and hypertension in deterioration of insulin-dependent (insulin sensitivity, S-I) and insulin-independent (glucose effectiveness, S-G) actions on glucose tolerance. Methods: We applied the minimal model of glucose kinetics to estimate S-I and SG indexes from insulinemia and glycemia data detected during a frequently sampled intravenous glucose tolerance test performed in 21 normo-glycemic 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 S-I estimates despite significantly different age, whereas a significant reduction was evident in the EH patients compared with these groups. Mean estimates of S-G 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 Scheffe 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.