Regulation of Leptin by Steroid Hormones in Rat Adipose Tissue

Abstract

We investigated if steroid hormones regulate the secretion and the expression of leptin in female and male rat adipose tissue fragments in vitro. Dexamethasone time and dose-dependently increased the secretion and mRNA expression of leptin with a half-maximal stimulation of approximately 1 nM. A time-course revealed a maximal stimulatory effect of 17 β-estradiol after 24 hours. In male adipose tissue 17 β-estradiol increased leptin secretion (32% by 50 nM 17 β-estradiol, P = 0.07 and 34% by 500 nM 17 β-estradiol, P < 1780.05) after 24 hours. An additional effect of estrogen was seen in the dexamethasone (50 nM) stimulated cells (38% with 50 nM 17 β-estradiol, P < 0.05 and 48% by 500 nM 17 β-estradiol, P < 0.05). Basal secretion of leptin was equal in female and male adipose tissue, whereas the effects of 17 β-estradiol (50 nM) and dexamethasone were significantly increased in female as compared with male adipose tissue. Progesterone, testosterone, dihydrotestosterone and dehydroepiandrostendione-sulfate neither affected leptin secretion in male nor female adipose tissue in vitro. Furthermore, to investigate the effect of estrogen female rats were ovariectomized (OVX) and the adipose tissue was incubated in vitro and compared with adipose tissue leptin secretion from sham operated rats (SHAM), and with ovariectomized rats treated with 17 β-estradiol (EST). A decreased basal and dexamethasone-stimulated leptin secretion from OVX rats compared with SHAM rats was found (P < 0.005) whereas 17 β-estradiol treatment of ovariectomized rats maintained a normal leptin secretion. However, the dexamethasone stimulation was equally increased above basal levels in SHAM, OVX and EST rats (3.7 ± 1.2, 2.9 ± 0.8, 4.2 ± 1.4, NS, ANOVA) respectively.