Parallel regulation of the local vascular and systemic metabolic effects of insulin

Recent studies have focused on the link between the development of disordered vascular regulation (e.g. hypertension) and alteration in the effects of insulin to mediate glucose uptake. We and others have recently demonstrated that insulin is a potent vasodilator. Further, it has been suggested that impairment of insulin-mediated vasodilation may be an important contributing factor in the development of increased peripheral resistance. However, whether the local vascular effects of insulin correlate with its systemic glucose regulatory effects remains unclear. Therefore, we assessed both vascular sensitivity to insulin (using dorsal hand vein linear variable differential transformer techniques) and glucoregulatory sensitivity to insulin (using the minimal model technique applied to a frequently sampled iv glucose tolerance test) in 12 normotensive nondiabetic volunteers. In these subjects, metabolic sensitivity to insulin and venous sensitivity to insulin were highly correlated (r2 = 0.42; P = 0.02). Additionally, vascular sensitivity to insulin was inversely correlated with fasting C-peptide levels (r2 = 0.49; P = 0.02). Both systemic and vascular sensitivities to insulin were also highly correlated with body mass index. These studies demonstrate that the glucoregulatory effects of insulin are paralleled by its local vasodilating effects and continue to support this linkage as an important factor in the correlation between alterations in systemic sensitivity to insulin and the development of elevated peripheral resistance in hypertension and obesity.