Insulin Resistance and Hyperinsulinemia Are Related to Plasma Aldosterone Levels in Hypertensive Patients

Abstract

OBJECTIVE—An association between aldosterone and insulin resistance has been demonstrated in obesity and primary aldosteronism and in blacks with the metabolic syndrome. The aim of this study was to evaluate the relationship of plasma aldosterone with insulin sensitivity in white subjects. RESEARCH DESIGN AND METHODS—In 356 patients with essential hypertension and 102 normotensive control subjects of comparable age and BMI, we measured, after discontinuation of treatment, plasma active renin, aldosterone, cortisol, glucose, insulin, and C-peptide levels and calculated markers of insulin sensitivity. Direct assessment of insulin sensitivity was obtained in a subset of 64 hypertensive patients by a hyperinsulinemic clamp. RESULTS—Hypertensive patients had significantly greater fasting plasma insulin and C-peptide concentrations and homeostasis model assessment (HOMA) indexes than normotensive control subjects. A positive association with increasing plasma aldosterone concentrations was demonstrated for plasma glucose, insulin, C-peptides, and HOMA. Assessment of insulin sensitivity by clamp showed a significant decrease of the metabolic clearance rate of glucose with increasing aldosterone levels. Significant correlations were found between plasma aldosterone, plasma insulin, and C-peptide levels, HOMA, and glucose metabolic clearance rate. Blood pressure and plasma potassium, plasma cortisol, and renin levels, but not BMI, were also directly correlated with plasma aldosterone. Multiple regression analysis showed that HOMA, together with plasma potassium, cortisol, and renin levels, was independently correlated with plasma aldosterone. CONCLUSIONS—This study demonstrates a direct relationship between aldosterone, insulin resistance, and hyperinsulinemia in white subjects. In patients with hypertension, this relationship might contribute to maintenance of high blood pressure and increased cardiovascular risk.