Endogenous inhibitors (GALFs) of 11beta-hydroxysteroid dehydrogenase isoforms 1 and 2: derivatives of adrenally produced corticosterone and cortisol.

Two isoforms of 11beta-HSD exist; 11beta-HSD1 is bi-directional (the reductase usually being predominant) and 11beta-HSD2 functions as a dehydrogenase, conferring kidney mineralocorticoid specificity. We have previously described endogenous substances in human urine, "glycyrrhetinic acid-like factors (GALFs)", which like licorice, inhibit the bi-directional 11beta-HSD1 enzyme as well as the dehydrogenase reaction of 11beta-HSD2. Many of the more potent GALFs are derived from two major families of adrenal steroids, corticosterone and cortisol. For example, 3alpha5alpha-tetrahydro-corticosterone, its derivative, 3alpha5alpha-tetrahydro-11beta-hydroxy-progesterone (produced by 21-deoxygenation of corticosterone in intestinal flora); 3alpha5alpha-tetrahydro-11beta-hydroxy-testosterone (produced by side chain cleavage of cortisol); are potent inhibitors of 11beta-HSD1 and 11beta-HSD2-dehydrogenase, with IC50's in range 0.26-3.0 microM, whereas their 11-keto-3alpha5alpha-tetrahydro-derivatives inhibit 11beta-HSD1 reductase, with IC50's in range 0.7-0.8 microM (their 3alpha5beta-derivatives being completely inactive). Inhibitors of 11beta-HSD2 increase local cortisol levels, permitting it to act as a mineralocorticoid in kidney. Inhibitors of 11beta-HSD1 dehydrogenase/11beta-HSD1 reductase serve to adjust the set point of local deactivation/reactivation of cortisol in vascular and other glucocorticoid target tissues, including adipose, vascular, adrenal tissue, and the eye. These adrenally derived 11-oxygenated C21- and C19 -steroidal substances may serve as 11beta-HSD1- or 11beta-HSD2-GALFs. We conclude that adrenally derived products are likely regulators of local cortisol bioactivity in humans.