Ageing impairs insulin-mediated vasodilatation but not forearm glucose uptake.

Abstract

It is unclear if insulin-mediated vasodilatation is altered by ageing and if this affects insulin-mediated glucose uptake. A 2-h euglycaemic hyperinsulinaemic clamp (56 mU m(-2) min(-1)) was performed in 10 healthy, nonobese elderly men (70-75 years) and 13 young men (23-28 years). Forearm blood flow (FBF) was measured by venous occlusion plethysmography and forearm glucose uptake was calculated by arterial and venous serum glucose determinations in the forearm. Insulin induced an increase in FBF in the younger men (from 3.9 +/- 1.1 SD to 5.9 +/- 2.2 mL min(-1) 100(-1)mL tissue, P < 0.001), but this insulin-mediated vasodilatation was completely blunted in the elderly subjects. Glucose extraction during the clamp was significantly higher in the elderly subjects (1.2 +/- 0.76 vs. 0.82 +/- 0.37 mmol L(-1) at 120 min, P < 0.01), resulting in a similar forearm glucose uptake in the two groups. On the other hand, whole-body glucose uptake was significantly decreased in the elderly subjects (5.3 +/- 1.8 vs. 8.0 +/- 1.1 mg kg(-1) min(-1), P < 0.001). The present study showed that the ability of insulin to induce vasodilatation is blunted in the forearm in healthy, nonobese elderly subjects. However, the elderly compensate for this impairment with an increased glucose extraction from arterial blood to maintain an unaltered forearm glucose uptake.