Potassium as a link between insulin and the renin-angiotensin-aldosterone system.

PURPOSE

To focus on the interactions between insulin secretion, glucose tolerance and insulin sensitivity on the one hand and the renin-angiotensin-aldosterone system on the other.

EFFECTS ON INSULIN

Insulin is a potent stimulus for hypokalaemia, sparing body potassium from urinary excretion by transporting it into cells. Potassium also appears to play a key role in the antinatriuretic effect of insulin. Insulin-induced hypokalaemia increases plasma renin and angiotensin II levels while decreasing the serum aldosterone concentration. In turn, the renin-angiotensin-aldosterone system affects glucose tolerance by modulating plasma potassium levels, which act as a stimulus for glucose-induced insulin release.

EFFECTS OF ANGIOTENSIN CONVERTING ENZYME (ACE) INHIBITION: Interference with the renin-angiotensin-aldosterone system by ACE inhibition blunts the hypokalaemic response to insulin, thereby improving glucose-induced insulin release and oral glucose tolerance. ACE inhibition, however, does not cause major changes in insulin sensitivity.

POTASSIUM AND BLOOD PRESSURE

Plasma potassium levels are inversely related to blood pressure, both in population surveys and in intervention studies. In addition, in patients with essential hypertension, the level of plasma potassium appears to predict the blood pressure response to ACE inhibition.

SUMMARY

Potassium metabolism is an important link between carbohydrate metabolism and the renin-angiotensin-aldosterone system by way of a double-feedback mechanism. Through the potential effects on blood pressure control, plasma levels of potassium represent a link between insulin and blood pressure in humans.