Endocrine Abstracts

Excess glucocorticoids (GC) promote visceral obesity, hyperlipidemia and insulin resistance. The main regulators of intracellular GC levels are 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which converts inactive GC into bioactive forms such as cortisol in humans and corticosterone in rodents. Therefore, the inhibition of 11β-HSD1 has considerable therapeutic potential for metabolic diseases including obesity and diabetes. Benzofran is a key structure in many biologically active compounds such as benzbromarone, Malibatol A and (+)-liphagal. The aim of this study is to investigate the inhibitory effect of benzofuran derivatives on 11β-HSD1. Microsomes were prepared from mesenteric adipose tissue from male Wistar rats. 11β-HSD1 activity was determined by incubation under an NADPH-regenerating system where the incubation medium, MOPS buffer, contained G-6-P (6 mM), NADP+(1 mM), G-6-PDH (0.35 units/ml), and 11-dehydrocorticosterone (1 μM) with and without benzofuran derivatives (Compound 1–14, 50 μM). The reaction was started by the addition of 15 μl of microsomes (1.6 mg protein/ml) and the reactants were incubated at 37°C up to 40 min. Two milliliters of CH₂Cl₂ solution was added to stop the reaction. Corticosterone produced was measured by HPLC. Significant inhibition of 11β-HSD1 activity was observed in compound 1 (57%), 5 (36%), 7 (37%) and 8 (50%) compared with control. Further, we investigated the effect of these compounds on 11β-HSD2 (conversion of corticosterone to 11-dehydrocorticosterone). Compound 7 and 8 did not suppressed 11β-HSD2, whereas compound 1 and 5 inhibited 11β-HSD2 by 18.7 and 56.3%, respectively. Compound 7 and 8 inhibited 11β-HSD1 in time- and dose-dependent manner. Kinetic study revealed that compound 7 (the most potent and selective inhibitor) acted as a non-competitive inhibitor of 11β-HSD1 and the apparent Km value for 11-dehydrocorticosterone was 0.25 μM. These results suggest that compound 7 may exert its inhibitory effect by interacting with the enzyme 11β-HSD1.