INSULIN INCREASES FOREARM VASCULAR-RESISTANCE IN OBESE, INSULIN-RESISTANT HYPERTENSIVES

Objective To determine whether acutely lowering insulin levels with so matostatin in obese, insulin-resistant hypertensive individuals reduce s arterial pressure and forearm vascular resistance; and whether these changes are reversed by restoring insulin levels during continuing so matostatin infusion. Subjects Subjects were 11 obese (body mass index 36 +/- 4 kg/m(2)) insulin-resistant, hypertensive men (systolic/ diast olic blood pressures 153 +/- 6/94 +/- 2 mmHg, aged 51 +/- 7 years, fas ting insulin level 17 +/- 8 mU/l). Methods Arterial pressure, forearm blood flow and vascular resistance were measured during 2 h of somatos tatin infusion and during 2 h of somatostatin plus insulin infusion (h yperinsulinemic or euglycemic clamp). Results Somatostatin infusion de creased plasma insulin levels from 17 +/- 2 to < 3 mU/l, Insulin infus ion raised plasma insulin levels to 86 +/- 7 mU/l, The forearm vascula r resistance decreased significantly during somatostatin infusion and increased significantly during infusion of somatostatin plus insulin, Somatostatin also caused small but significant reductions in arterial pressure whereas insulin infusion during somatostatin infusion increas ed arterial pressure, Control experiments in six obese hypertensives i ndicated that the changes in forearm vascular resistance (but not in a rterial pressure) were caused neither by time nor by vehicle, Control studies in six young normotensives indicated that somatostatin does no t block the vasodilator response to insulin previously demonstrated in this group. Conclusions The present results suggest that insulin caus es forearm vasoconstriction in obese, insulin-resistant hypertensive h umans.