Insulin and Blood Pressure Relationships

Insulin is not only a pancreatic hormone of fundamental importance for glucose and lipid metabolism, but also for vasodilation and blood pressure regulation. In normal subjects, insulin acts as a post-alimentary hormone to induce vasodilation and a fall in blood pressure within normal range. This is in contrast to states of insulin resistance when the effect of insulin (hyperinsulinaemia), by itself, or as a marker of the underlying insulin resistance, is different and a promotor of increased blood pressure. Several epidemiological studies have shown associations between hyperinsulinaemia, as a marker of impaired insulin sensitivity, and increased blood pressure. This is even more pronounced in insulin-resistant subjects with features of the metabolic syndrome or early type 2 diabetes. Several mechanisms are activated to increase blood pressure levels in these subjects, i.e. sodium retention, increased sympathetic nervous activation, endothelial dysfunction, vascular remodelling and electrolyte imbalance. Genetic studies have indicated that insulin-like growth factor binding protein 3 (IGF-BP3) is a regulator of blood pressure. Interventions based on healthy lifestyle advice may decrease body weight and blood pressure in parallel with an improvement of insulin sensitivity and a reduction of hyperinsulinaemia. Several antihypertensive drugs (RAS blockers, calcium antagonists, alpha-receptor blockers, moxonidine), as well as some antidiabetic drugs (glitazones), may improve insulin sensitivity and reduce blood pressure, indicating a causal link.