ABSTRACT
AIMS: The physiological effects of glucocorticoids in a given tissue are driven by the local level of the active glucocorticoid, which is determined by two sources: the plasma cortisol in human (or corticosterone in rodents) and the cortisol produced locally through 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) activity. Because of the circadian variation of plasma glucocorticoids, the pharmacological efficacy of 11beta-HSD1 inhibition may depend on the time of the day for inhibitor administration. METHODS: The circadian profile of corticosterone was established in lean and diet-induced obesity (DIO) C57BL/6 mice from blood collected at different time of the day. 11beta-HSD1 enzyme activity was also measured throughout the day in DIO mice. To determine the optimal timing for administration of an 11beta-HSD1 inhibitor to obtain maximum efficacy, we used a DIO mouse model and a small molecule inhibitor of 11beta-HSD1 from our thiazolinone series. Based on the circadian profile of corticosterone obtained, we administered the 11beta-HSD1 inhibitor to these animals at different times of the day and evaluated the effects on plasma glucose levels and glucose tolerance. RESULTS: We report that corticosterone circadian rhythm was similar between lean and DIO C57BL/6 mice, and 11beta-HSD1 enzyme activity undergoes minimal variations throughout the day. Interestingly, the compound exhibited maximum efficacy if dosed in the afternoon when plasma corticosterone is high; the morning dosing when plasma corticosterone is low did not lead to efficacy. CONCLUSION: These data suggest that because of the circadian rhythm of circulating glucocorticoids, the time of the day for 11beta-HSD1 inhibitor administration is important in achieving efficacy.
