Role of Estrogen Receptor-α and -β in Regulating Leptin Expression in 3T3-L1 Adipocytes

We investigated the effects of the estrogen receptor-alpha (ER alpha) and-beta (ER beta) in the regulation of leptin, resistin, and adiponectin expression in 3T3-L1 adipocytes. Mature adipocytes were exposed to estradiol (E2), ER alpha agonist (PPT (4,4', 4 ''-(4-propyl-[1H]-pyrazole-1,3,5-triyl) trisphenol)), ER beta agonist (DPN (2,3-bis(4-Hydroxyphenyl)-propionitrile)), E2 with ERa antagonist (MPP (1,3-Bis(4-hydroxyphenyl)-4-methyl-5-[4-(2-piperidinylethoxy) phenol]-1H-pyrazole dihydrochloride)), and E2 with ER beta antagonist (R, R-THC ((R, R)-5,11-diethyl-5,6,11,12-tetrahydro-2,8-chrysenediol)) at different concentrations. To clarify the expression and regulation of adipokines by ER subtypes, total RNA was extracted from cells and measured using quantitative PCR. Western blot analysis was performed to evaluate the protein expression of adipokines, ER alpha, and ER beta. The leptin expression was significantly increased in the cells treated with high concentrations (10(-5) and 10(-6) mol/l) of the PPT (P < 0.01, P < 0.05). By contrast, the leptin expression decreased in a dose-dependent manner in the MPP-treated groups (P < 0.05). High concentrations (10(-5) mol/l) of R, R-THC with E2 (10(-7) mol/l) caused a significant increase of the leptin expression (P < 0.01). The leptin mRNA levels were positively correlated with the ER alpha mRNA levels (r = 0.584, P < 0.01) and negatively correlated with the ER beta mRNA levels (r =-0.236, P = 0.03) in the adipocytes. The ratio of the ER alpha to ER beta mRNA levels in the adipocytes was significantly associated with leptin mRNA levels (r = 0.454, P < 0.01). ER alpha induced leptin expression and ER beta inhibited its expression in 3T3-L1 adipocytes. The ratio of the ER alpha-to-ER beta expression in 3T3-L1 adipocytes may be an important potential regulatory factor in leptin expression.