'Physiological' hyperinsulinaemia increases distal artery systolic blood pressure without changing proximal blood pressure.

1. Although epidemiological data links essential hypertension with insulin resistance, 'physiological' insulin concentrations have not had pressor effects in humans. Our previous studies suggested that hyperinsulinaemia might have effects on distal blood pressure which are not detected more proximally. Therefore, we used non-invasive techniques to determine the acute effects of insulin on proximal and distal blood pressure. 2. Blood pressure was measured in the finger (Finapres) and arm (Dinamap monitor) during a two-stage euglycaemic clamp. Values obtained during the insulin infusion were compared with a control infusion. 3. Plasma insulin concentrations were 7.0 +/- 1.0 mu-units/ml at baseline and remained within the accepted post-prandial 'physiological' range during low- and high-dose insulin infusions (28.9 +/- 2.1 and 101.7 +/- 6.8 mu-units/ml respectively). From a baseline value of 130 +/- 3 mmHg, finger systolic blood pressure rose by 9.9 +/- 1.9 mmHg during the low-dose infusion (compared with 7.5 +/- 2.7 mmHg in control, P < 0.05) and by 21.9 +/- 2.3 mmHg during the high-dose infusion (compared with 14.6 +/- 3.1 mmHg in control, P < 0.01). Compared with control, insulin did not have an additional effect on arm pressures. 4. Although finger systolic pressure was increased by hyperinsulinaemia, this occurred in the absence of a change in mean blood pressure or in arm pressures. These data therefore suggest that insulin augmented pulse wave reflection. This novel haemodynamic effect of insulin could contribute to the association of insulin resistance with essential hypertension.