胰岛素对高糖培养的人系膜细胞表达SGK1及合成细胞外基质的影响

Effect of insulin on the SGK1 expression and extracellular matrix synthesis in human mesangial cells cultured in high glucose

目的:研究胰岛素对高糖培养的人系膜细胞(HMC)血清和糖皮质激素诱导的蛋白激酶1(SGK1)的表达及细胞外基质(ECM)合成的影响,初步探讨其主要作用环节。方法:用含有5.5 mmol/L、25 mmol/L葡萄糖和100 nmol/L胰岛素的DMEM培养基培养HMC细胞,即为对照组(NG)、高糖组(HG)、胰岛素干预对照组(NI)和胰岛素干预高糖组(HI)。4 h后检测SGK1的表达、胰岛素受体底物(IRS1和IRS2)蛋白的表达及磷酸化水平;24 h后检测结缔组织生长因子(CTGF)和纤连蛋白(FN)的表达。结果:HG组、NI组和HI组SGK1蛋白表达均显著高于NG组(P<0.01),高糖主要导致IRS2蛋白表达及磷酸化水平的增高(P<0.01)。胰岛素干预后,HI组IRS1蛋白表达及磷酸化水平明显高于HG组(P<0.05),而IRS2蛋白表达及磷酸化水平出现部分抑制(P<0.05)。高糖促进CTGF和FN的表达,胰岛素加强高糖此作用。结论:胰岛素和高糖能够通过不同的分子途径促进体外肾小球系膜细胞SGK1的表达,并最终促进ECM的合成;胰岛素的这种作用与IRS1信号转导通路密切相关。

AIM ： To study the effect of insulin on the serum and glucocorticoid - inducible kinase 1 （ SGK1 ） expression and extracellular matrix synthesis in human glomerular mesangial cells （HMC） cultured in high glucose. METHODS： The HMCs were cultured in the presence of 5.5 or 25 mmol/L glucose with or without 100 nmol/L insulin （ i.e. NG, HG, NI and HI groups）. 4 h latter, expressions of SGK1, insulin receptor substrate - 1 （IRS1） and IRS2 in corresponding groups were detected by immunofluorescence or examined by Western blotting. The phosphorylation of IRS1 and IRS2 was measured by immunoprecipitation. 24 h latter, connective tissue growth factor（CTGF） and fibronectin （FN） were also examined by RT - PCR and ELISA, respectively. RESULTS ： Compared with NG, the SGK1 protein expression in HG, NI and HI groups was significantly higher （P 〈 0. 01 ）. High glucose mainly caused IRS2 protein and its phospho- rylation level increase （P 〈 0. 01 ）. When treated with 100 nmol/L insulin, IRS1 protein and its phosphorylation in HI group apparently elevated while slight inhibition of IRS2 protein expression and its phosphorylation were observed （ HI vs HG, P 〈0. 05）. High glucose enhanced the expression of CTGF and FN, and insulin strengthened this effect. CONCLUSION ： Insulin and high glucose up - regulate the expression of SGK1 in mesangial cells through different target molecular pathways and ultimately enhance ECM synthesis. The effect of insulin is highly associated with IRS1 signaling cascades.