The link between insulin resistance and hypertension. Effects of antihypertensive and antihyperlipidaemic drugs on insulin sensitivity.

Insulin resistance is generally interpreted as the physiological state under which insulin causes a reduced glucose-lowering effect. Hyperinsulinaemia is considered to be a result of insulin resistance. Many recent studies have suggested that hyperinsulinaemia and/or insulin resistance is associated with an elevated blood pressure, whereas several other studies have found a modest or no association. Many factors (e.g. adiposity, age, ethnic difference) have been suggested to confound the insulin-blood pressure relationship. Insulin is thought to raise blood pressure by a few possible mechanisms (e.g. stimulating sympathetic nervous system activity, enhancing renal tubular sodium reabsorption). On the other hand, insulin has also been reported to possess a vasodilatory property. Neither an insulin infusion within a physiological range nor continuously sustained hyperinsulinaemia in patients with insulinoma are associated with elevated blood pressure. Therefore, the relationship between insulin and blood pressure is still under discussion. Among the antihypertensive drugs, angiotensin converting enzyme (ACE) inhibitors seem to have marginal effects of improving insulin sensitivity, but whether this effect would lead to a better prognosis for diabetic patients remains to be proven. Lipid lowering drugs appear to show no benefit in lowering blood glucose.