SREBP1c表达水平对肠道糖异生的影响

Effect of sterol regulatory element binding protein 1c expression on intestinal gluconeogenesis in mice

目的研究固醇调节元件结合蛋白1c(sterol regulatory element binding protein 1c,SREBP1c)对肠道糖异生的调控作用。方法饥饿处理C57BL/6小鼠、SREBP1c纯合敲除型(SREBP1c-KO)和同窝野生型(SREBP1c-WT)小鼠,通过qPCR、Western blot检测糖异生途径限速酶葡萄糖-6-磷酸酶(glucose-6-phosphatase catalytic,G6PC)和磷酸烯醇式丙酮酸羧激酶(phosphoenolpyruvate carboxykinase 1,PCK1)在肝脏、空肠和回肠组织中的表达水平;在肠上皮细胞CaCo-2中过表达或敲低SREBP1c,检测细胞内G6PC和PCK1表达水平。结果饥饿处理后,C57BL/6小鼠空肠、回肠组织中G6PC、PCK1和SREBP1c表达水平均显著增加(P<0.05)。SREBP1c基因敲除后,小鼠空肠、回肠组织中由饥饿诱导的糖异生限速酶G6PC和PCK1的表达明显下调(P<0.05)。在肠上皮细胞CaCo-2中过表达SREBP1c,可显著上调糖异生途径关键酶G6PC和PCK1的表达,促进细胞内葡萄糖的产生(P<0.05);反之,敲低SREBP1c的表达,可明显下调G6PC和PCK1,抑制细胞内葡萄糖的产生(P<0.05)。结论饥饿状态下,SREBP1c可调控肠上皮细胞中糖异生限速酶G6PC和PCK1的表达,进而影响葡萄糖的生成,表明SREBP1c可能参与肠道糖异生的调控,机制有待进一步探索。

Objective To investigate the regulation role of sterol regulatory element binding protein 1c(SREBP1c)in intestinal gluconeogenesis.Methods After C57BL/6 mice,and SREBP1c homozygous knockout(SREBP1c-KO)and littermate wild-type(SREBP1c-WT)mice were fasted for 48 h,qPCR and Western blotting were used to detect the expression of rate-limiting gluconeogenic genes glucose-6-phosphatase(G6PC)and phosphoenolpyruvate carboxykinase 1(PCK1)in the liver,jejunum and ileum tissues at mRNA and protein levels.After overexpression or knockdown of SREBP1c in the intestinal epithelial cell line CaCo-2,the expression levels of G6PC and PCK1 were measured.Results The expression levels of G6PC,PCK1,and SREBP1c were significantly increased in the jejunum and ileum tissues of C57BL/6 mice after fasting(P<0.05).In SREBP1c-KO mice,fasting treatment induced obviously inhibited expression of G6PC and PCK1 in the jejunum and ileum tissues(P<0.05).Overexpression of SREBP1c significantly upregulated the expression levels of G6PC and PCK1,and promoted the production of glucose in CaCo-2 cells(P<0.05).Conversely,knocking SREBP1c down resulted in down-regulation of G6PC and PCK1 and suppressed production of glucose in CaCo-2 cells(P<0.05).Conclusion Under fasting,SREBP1c is involved in regulation of G6PC and PCK1 in intestinal epithelial cells,and thus affects glucose production.It indicates that SREBP1c might be involved in the regulation of intestinal gluconeogenesis,and the mechanism needs further exploration.