ESTROGEN INCREASES IN-VIVO LEPTIN PRODUCTION IN RATS AND HUMAN-SUBJECTS

The decrease in estrogen in menopausal women increases body fat. The p resent studies were undertaken to investigate the involvement of estro gen in leptin production in vivo. In the first study, expression of ob gene mRNA in white adipose tissue was measured at 2 and 8 weeks after ovariectomy in rats. In the second, serum leptin concentration was me asured in total body fat of 87 weight-matched human subjects (29 men, 29 premenopausal and 29 postmenopausal women). In the third, changes i n serum leptin concentration with the menstrual cycle were determined. ob gene expression decreased in subcutaneous and retroperitoneal whit e adipose tissue of ovariectomized rats 8 weeks after the operation, w hile ovariectomy increased ob gene expression in mesenteric white adip ose tissue. Serum leptin concentration was decreased by ovariectomy. E stradiol supplement reversed the effect of ovariectomy on ob gene expr ession and circulating leptin levels. In humans, serum leptin concentr ation was higher in premenopausal women than in men, and in postmenopa usal women it was lower than in premenopausal women, but still higher than in men. In 13 premenopausal women, serum leptin levels were signi ficantly higher in the luteal phase than in the follicular phase. The present studies strongly indicate that estrogen regulates leptin produ ction in rats and human subjects in viva. Regional variation in the re gulation of ob gene expression by estrogen was found.