Abstract 017: Spironolactone Improves Insulin Secretion In Metabolic Syndrome Subjects

Abstract

Renin-angiotensin-aldosterone system blockade reduces the incidence of type 2 diabetes in clinical trials. We previously demonstrated that aldosterone impairs insulin secretion via a direct beta-cell effect in mice. To test the hypothesis that aldosterone and the mineralocorticoid receptor contribute to impaired insulin secretion in humans, we enrolled subjects with metabolic syndrome treated with hydrochlorothiazide (HCTZ) 12.5 mg daily for 4 weeks (baseline) followed by either Spironolactone 25 mg daily (SPL, n=16) versus Aliskiren 150 mg daily (ALI, n=19) for 4 weeks. We assessed insulin secretion and sensitivity using hyperglycemic clamps during sodium controlled diet (160 mmol Na). During HCTZ alone, plasma aldosterone correlated inversely with the initial insulin response and disposition index (Figure A), but not with insulin sensitivity index. Plasma aldosterone decreased during aliskiren (-1.5±0.78 ng/dL) and increased during spironolactone treatment (+4.0±0.8 ng/dL; p<0.001 between treatment). Blood pressure, serum potassium, and insulin sensitivity index were unchanged. The acute insulin response increased compared to baseline during SPL compared to ALI (+11.6±7.9 vs -10.7±7.7 μU/mL; p=0.048), whereas insulin sensitivity index was unchanged. We conclude that aldosterone is inversely associated with the initial phase insulin secretory response, the earliest detectable change in impaired glucose tolerance. Treatment with spironolactone could improve glucose homeostasis by restoring insulin secretion in subjects with metabolic syndrome.