Peripheral tissue insulin sensitivity in healthy elderly subjects

To determine whether the decline in glucose tolerance with age is related to changes in peripheral tissue insulin sensitivity, 11 healthy older (65-85 years) and 12 healthy younger (20-38 years) subjects, matched for physical activity and body mass index, were studied. The glucose-insulin infusion technique, in which glucose and insulin are infused at constant rates over 150 min, was used to assess peripheral tissue insulin sensitivity. The metabolic clearance rate (MCR) of glucose, which reflects peripheral tissue insulin sensitivity, is derived from the resulting steady-state blood glucose. Fasting blood glucose was similar in the two groups, but mean blood glucose 2 h after an oral glucose load was higher in the older group. MCR of glucose expressed per kilogram lean body mass was almost identical in both groups (13.3 +/- 1.3 vs. 13.5 +/- 1.3 ml/kg lean body mass/min, respectively). Evidence of decreased glucose tolerance with normal peripheral tissue insulin sensitivity suggests that changes in other factors may be more important than previously recognised.