Diet and the role of 11beta-hydroxysteroid dehydrogenase-1 on obesity.

11beta-Hydroxysteroid dehydrogenase-1 (11beta-HSD-1) is a key regulatory enzyme in glucocorticoid metabolism, specifically in regulating intracellular concentrations of cortisol, the primary glucocorticoid. While the excessive level of circulating cortisol in Cushing's disease is of adrenal origin, it is the intracellular and not the systemic level of cortisol that is elevated in obesity. This tissue-specific dysregulation of glucocorticoids observed in obesity results from alterations in 11beta-HSD-1 in both liver and mesenteric adipose. While cortisol has been identified as playing a permissive role in obesity, little is known about how diet may regulate message, expression and activity of 11beta-HSD-1. In this review, we have integrated three lines of evidence that, taken together, suggest that dietary composition can play a primary role in promoting increased intracellular cortisol and in that way form the basis of a mechanism that results in excessive adiposity. We review evidence from studies of adrenalectomized rats, as well as studies linking 11beta-HSD-1 to the pentose phosphate pathway and other metabolic pathways via the enzyme hexose-6-phosphate dehydrogenase. Emerging evidence from dietary manipulation experiments suggesting that macronutrient composition may elicit changes in 11beta-HSD-1 and promote obesity is discussed.