Aldosterone and dexamethasone both stimulate energy acquisition whereas only the glucocorticoid alters energy storage

Abstract

Corticosteroids stimulate and insulin inhibits energy acquisition (food intake); conversely, corticosteroids inhibit and insulin stimulates energy storage (body weight gain). Thus, together these hormones mediate long-term energy balance. This study tested whether the stimulatory action of corticosteroids on food intake was mediated by association with high affinity mineralocorticoid receptors (MRs) or lower affinity glucocorticoid receptors (GRs). Young male rats were adrenalectomized (ADX) and given vehicle (control) or streptozotocin (diabetic); subgroups of rats were infused with vehicle, aldosterone (Aldo, an MR agonist in vivo), dexamethasone (Dex, a GR agonist in vivo), or Aldo&Dex for the 5 days after ADX. Sham-ADX rats were included. Food intake, body weight gain, and epididymal white adipose and interscapular brown adipose tissue stores were weighed. ADX decreased food intake by approximately 24%, and food intake was not increased by diabetes as it was in sham-ADX rats. In control ADX rats, Dex, but not Aldo, stimulated insulin, and food intake was not significantly affected by either hormone; together, Aldo and Dex restored insulin and food intake to sham-ADX rats. Food intake in diabetic ADX rats was significantly increased by each treatment (ADX < Aldo < Dex < Aldo&Dex = sham). Aldo increased body weight through an increase in fluid volume (estimated by decreased plasma protein concentration); however, fat stores were not different from ADX. Dex reduced body weight in control rats but maintained fat stores; in diabetic rats, body weight and fat stores were less than or similar to ADX. We conclude that: 1) corticosteroids, acting through association with both MRs and GRs, stimulate food intake; 2) insulin counteracts the GR-mediated stimulation of food intake in control rats; and 3) Dex and insulin, which is stimulated by Dex, selectively maintain or increase body fat stores, probably at the expense of protein stores.