The Effect Of Estrogen On Triglyceride Hydrolysis In Adipocyte And Its Mechanism

ObjectivesTo investigate the impact of17β-estradiol(17(3-E2) on triglyceride metabolism in adipocyte and its mechanism.Methods3T3-L1adipocytes were cultured and differentiated into mature adipocytes in vitro. The adipocytes were divided into three groups:(1)estrogen groups:the adipocytes were treated with17(3-E2with various concentrations (0,10-9,10"7and10-6mol/L) for48hours.(2)selective estrogen receptors(ER) antagonist groups:the adipocytes were intervened with MPP (selective ER a antagonist) or PHTPP (selective ERβ antagonist) for one hour and the adipocytes in the blank control group were maintained in plates containing culture medium alone. Then they were treaded with17β-E210-6mol/L for48hours.(3) lipopolysaccharide (LPS) groups:after the intervention with100ng/ml LPS for24hours, the adipocytes were treated with10-6mol/L17β-E2for48hours. The adipocytes in the control group were treated with LPS alone.The levels of triglyceride in mature adipocytes and the concentration of interleukin-6(IL-6) in supernatant in LPS groups were measured using enzyme-linked immunosorbent assay (ELISA). The protein expression of hormone-sensitive lipase(HSL), adipose triacylglycerol lipase(ATGL) and perilipin in adipocytes were detected by Western blot.Results1. With the increase of the17β-E2concentration, the triglyceride levels in mature adipocytes were to tend decrease, especially in the group treated with10"6mol/L17β-E2for48hours. Comparing with control, the levels of triglyceride of mature adipocytes in the group treated with10-6mol/L17β-E2were significantly lower (P<0.01),and there were also significant difference when comparing with10-7mol/L and10-9mol/L17β-E2groups(all P<0.01).However, the difference of the triglyceride levels in adipocytes between10-7mol/L or10-9mol/L17β-E2 group and control group had no statistical significance (all P>0.05).2. Compared with control group, the triglyceride levels of mature adipocytes in17β-E2group and17P-E2+PHTPP group were significantly lower (P<0.05and P<0.01,respectly). But they were similar in the17β-E2+MPP group and control group(P>0.05).3. There were no significant differences of the triglyceride levels in mature adipocytes among LPS group,17β-E2+LPS group and control group (all P>0.05). The IL-6levels in the supernatant of the cultured mature adipocytes in LPS group and17β-E2+LPS group were higher than those in control group(P<0.01and P<0.05,respectly). However, the IL-6levels were similar in LPS group and17β-E2+LPS group (P>0.05).4. The expression of HSL, ATGL and perilipin of matured adipocytes in17β-E2group,17β-E2+MPP group,17β-E2+PHTPP group,LPS group,17P-E2+LPS group and control group was measured by Western blot. Compared with control group and17β-E2+MPP group, the expression of ATGL was markedly elevated in17P-E2+PHTPP group(all P<0.01).The expression of ATGL was also higher than that of17β-E2group(P<0.05).The expression of ATGL was similar among other groups(all P>0.05). The expression of HSL and perilipin in all the groups had no significant differences(all P>0.05).Conclusions17β-E2up-regulates the expression of ATGL and promotes triglyceride hydrolysis in mature adipocytes which may be mediated by ERa. The effect of estrogen on triglyceride metabolism in adipocytes may be attenuated or disappered in the presence of inflammation.