Reduced Adipose Glucocorticoid Reactivation and Increased Hepatic Glucocorticoid Clearance as an Early Adaptation to High-Fat Feeding in Wistar Rats

Abstract

Altered peripheral glucocorticoid metabolism may be important in the pathogenesis of obesity in humans and animal models. Genetically obese Zucker rats, Lep/ob mice, and obese humans exhibit increased regeneration of active glucocorticoids selectively in adipose tissue by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD-1) and increased glucocorticoid clearance by hepatic A-ring reductases. We have examined whether dietary obesity in rats induces the same changes in glucocorticoid metabolism. Male Wistar rats were weaned onto high-fat (HF; 45% kcal from fat) or control (10% fat) diets. After 3 wk, HF rats showed no differences in weight but were glucose intolerant, had lower 11β-HSD-1 activity in liver (3.8 ± 0.2 vs. 4.9 ± 0.2 pmol product/min·mg protein; P < 0.01), sc fat (0.03 ± 0.01 vs. 0.09 ± 0.01 pmol product/min·mg protein; P < 0.01), and omental fat (0.02 ± 0.001 vs. 0.03 ± 0.003 pmol/ product/min·mg protein; P < 0.05) and higher hepatic 5β-reductase activity (0.26 ± 0.05 vs. 0.10 ± 0.007 pmol product/min·mg protein; P < 0.05). After 20 wk, HF rats were obese, hyperglycemic, and hyperinsulinemic, but differences in 11β-HSD-1 and 5β-reductase activities were no longer apparent. Mature male rats given HF diets for 24 or 72 h showed increased hepatic 5β-reductase activity and a trend for decreased sc adipose 11β-HSD-1 activity. Dietary obesity is not accompanied by the changes in 11β-HSD-1 and 5β-reductase expression and activity observed in genetically obese rodents. Acute exposure to HF diet alters glucocorticoid metabolism, predicting lower hepatic and adipose intracellular glucocorticoid concentrations, which may be a key mechanism protecting against the metabolic complications of obesity.