Effects of 17β-estradiol on leptin signaling in anterior pituitary of ovariectomized rats

Leptin is secreted predominantly by adipocytes and exerts its role mainly by interaction with the long form of leptin receptor (LEPR_V2). It has been identified that LEPR_V2 is widely distributed in various tissues, including the anterior pituitary. Cross-talk between leptin and estrogens has been indentified. Estrogen is known to modulate the tissue-specific expression of LEPR_V2 and leptin in ovariectomized (OVX) rats, a model of postmenopausal condition. Our previous data showed that 17β-estradiol (E2) up-regulated the expression of LEPR_V2 protein and mRNA in rat dorsal root ganglion (DRG) in an estrogen receptor alpha (ERα)-dependent manner. But it is still unclear whether estrogen can regulate leptin signalling in the pituitary of OVX rats. In the present study, we found that ovariectomy decreased the expressions of LEPR_V2. Administration of E2 increased the expressions of LEPR_V2 in a dose-dependent manner. In addition, E2 improved LEPR_V2, STAT3, and SOCS3 protein levels in OVX rats. The effects of exogenous E2 were attenuated by ICI 182,780, a specific estrogen receptors antagonist. However, E2 did not change the Lepr_v1, a type of short form of leptin receptor (LEPR), or leptin mRNA levels. Thus, E2 plays a crucial role in regulating pituitary sensitivity to leptin in OVX rats. Our findings implied that exogenous E2 had potential roles in modification of the function of pituitary in postmenopausal women.