Increased forearm blood flow during glucose clamp is related neither to insulin sensitivity nor to hyperinsulinemia in borderline hypertensive young men.

It is controversial whether raised insulin within the physiological concentration range increases forearm blood flow (FBF). The aim of the present study was therefore to examine the effect of the isoglycemic hyperinsulinemic glucose clamp procedure on FBF and to relate the increase to the glucose disposal rate (GDR), i.e. insulin sensitivity. Borderline hypertensive young men were examined with the clamp technique or received saline infusion, and FBF was measured using plethysmography. It is of particular interest to study this group of subjects because their GDR correlates to a number of metabolic and hemodynamic variables, and these subjects hyperreact to stressful stimuli. There was no correlation between deltaFBF during clamp and GDR (r = -0.002, p = 0.99, n = 28). While serum insulin increased from 107 +/- 5 to 628 +/- 31 pmol/l in the hyperinsulinemic group and remained unchanged (135 +/- 11 vs 116 +/- 11 pmol/l) in the saline group, FBF increased from 3.5 +/- 0.3 to a maximum of 5.1 +/- 0.4 ml/min/100 ml (p < 0.001, n = 28) and from 2.8 +/- 0.5 to a maximum of 4.5 +/- 0.5 ml/min/100 ml (p = 0.01, n = 8), respectively. The increase in FBF (delta%) was similar in the two groups (p = 0.9). Thus, we could not demonstrate any relationship between insulin sensitivity and increments in FBF during hyperinsulinemic glucose clamp in borderline hypertensive young men. The moderate increases in FBF during insulin infusion with serum concentrations within the physiological range seem to be time-dependent and not caused by hyperinsulinemia.