Salt Sensitivity and Glucose Metabolism

FUKUSHIMA, JapanSalt sensitivity of blood pressure is strongly associated with insulin resistance in lean, essential hypertensive patients, according to a study published in the American Journal of Clinical Nutrition (2010; 92(1):77-82). Both blood pressure and insulin resistance are sub-characteristics of hypertension and impaired glucose metabolism, respectively, and are components of metabolic syndrome.

The state of glucose metabolism was assessed by a hyperinsulinemic euglycemic glucose clamp technique and a 75-g oral-glucose-tolerance test in 24 essential hypertensive patients who were lean and without diabetes or chronic kidney disease. The subjects were classified as salt-sensitive or salt-resistant on the basis of the difference between 24-hour ambulatory blood pressure monitoring results on the seventh day of low-salt (34 mmol/d) and high-salt (252 mmol/d) diets.

There was a strong inverse relation between the glucose infusion rate (GIR) and the salt sensitivity index. The GIR correlated directly with the change in urinary sodium excretion and was inversely related to the change in hematocrit when the salt diet was changed from low to high, which is indicative of salt and fluid retention in salt-sensitive subjects. The GIR also showed an inverse correlation compared with the changes in urinary norepinephrine excretion, plasma renin activity and plasma aldosterone concentration. Hyperinsulinemia, sympathetic overactivation and reduced suppression of the renin-angiotensin system may play a role in the relationship blood pressure and insulin resistance.