瘦素抑制小鼠PPARγ1基因表达的机制探讨

An investigation of mechanism for leptin to inhibit PPARγ1 gene expression in mice

目的探讨瘦素抑制小鼠过氧化物酶体增殖物激活受体(PPAR)γ1基因表达的可能机制。方法从UCSC数据库获得小鼠PPARγ1基因转录起始点上游约3kbp的序列,分别运用Patch和Signal Scan在线软件分析该序列,筛选出两组结果中相同的转录因子及相应的结合位点,并找出其中与脂质代谢和脂肪细胞分化相关的转录因子,采用Western blot和瞬时转染实验验证。结果经过筛选,GATA结合蛋白2(GATA-2)是与脂质代谢和脂肪细胞分化相关的转录因子。Western blot结果显示,经瘦素处理的肝星状细胞的GATA-2表达升高(P<0.05);在转染pPPARγ1(-2333)Luc的肝星状细胞中,瘦素处理后的荧光素酶活性降低(P<0.05),而在转染pPPARγ1(-1823)Luc、pPPARγ1(-1313)Luc的肝星状细胞中,瘦素处理后的荧光素酶活性无明显变化(P>0.05)。与转染pPPARγ1(-2333)Luc的肝星状细胞相比,转染pPPARγ1(GATA mut)Luc的肝星状细胞荧光素酶活性升高(P<0.05)。结论 GATA-2通过与PPARγ1的5′端转录起始点上游-1823^-2333的区域结合参与瘦素对小鼠PPARγ1基因表达的抑制。

Objective To investigate the possible mechanism for leptin to inhibit peroxisome proliferator-activated receptor gamma 1 （PPARγ1） gene expression in mice. Methods Up-stream 3 kbp sequences of the transcription start site of mouse PPARγ1 gene were collected in UCSC, which were analyzed with Patch and Signal Scan respectively. Transcription factors related to lipid metabolism and adipocyte differentiation were selected, and Western blot and transient transfeetion assay were applied to verify. Results GATA-2 was selected as the potential transcription factor. Western blot showed that the expression of GATA-2 in HSCs was increased after treated with leptin （P〈0. 05）, The luciferase activity of HSCs transfected with pPPARγ1 （ - 2333） Luc was decreased after treated with leptin（P〈0. 05）, but the luciferase activity of HSCs transfected with pPPARγ1 （ - 1823） Luc and pPPARγ1 （- 1313） Luc was not changed significantly（P〉0. 05）. When incubated with leptin, the luciferase activity of the HSCs transfected with pPPARγ1 （GATAmut）Luc was increased compared with the HSCs transfected with pPPARγ1 （-2333） Luc. Conclusion GATA-2 plays a role in the inhibition effect of leptin on PPARγ1 by binding to the region of-1823 to -2333 on the 5P-untranslated sequences of mouse PPARγ1 gene.