Regulation of leptin by steroid hormones in rat adipose tissue

We investigated if steroid hormones regulate the secretion and the expressi on of leptin in female and male rat adipose tissue fragments in vitro. Dexa methasone time and dose-dependently increased the secretion and mRNA expres sion of leptin with a half-maximal stimulation of approximately 1 nM. A tim ecourse revealed a maximal stimulatory effect of 17 beta-estradiol after 24 hours. In male adipose tissue 17 beta-estradiol increased leptin secretion (32% by 50 nM 17 beta-estradiol, P = 0.07 and 34% by 500 nM 17 beta-estrad iol, 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 beta-estr adiol, P < 0.05 and 48% by 500 nM 17 beta-estradiol, P < 0.05). Basal secre tion of leptin was equal in female and male adipose tissue, whereas the eff ects of 17 beta-estradiol (50 nM) and dexamethasone mere significantly incr eased in female as compared with male adipose tissue. Progesterone, testost erone, dihydrotestosterone and dehydroepiandrostendione-sulfate neither aff ected leptin secretion in male nor female adipose tissue in vitro. Furtherm ore, to investigate the effect of estrogen female rats were ovariectomized (OVX) and the adipose tissue was incubated in vitro and compared with adipo se tissue leptin secretion from sham operated rats (SHAM), and with ovariec tomized rats treated with 17 beta-estradiol (EST). A decreased basal and de xamethasone-stimulated leptin secretion from OVX rats compared with SHAM ra ts was found (P < 0.005) whereas 17 beta-estradiol treatment of ovariectomi zed rats maintained a normal leptin secretion. However, the dexamethasone s timulation was equally increased above basal levels in SHAM, OVX and EST ra ts (3.7 +/- 1.2, 2.9 +/- 0.8, 4.2 +/- 1.4, NS,ANOVA) respectively. (C) 1999 Academic Press.