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目的研究不同程度感染大鼠骨骼肌胰岛素受体底物-1(IRS-1)及其丝氨酸(Ser307)磷酸化和酪氨酸(Tyr)磷酸化在胰岛素抵抗(IR)中的作用。方法SD大鼠随机分为对照组、10%组和30%组。10%组和30%组大鼠用盲肠结扎穿孔制造感染模型,结扎长度分别为总长度的10%和30%,对照组为假手术组。3组大鼠分别在术前和术后各时间点取空腹血和后腿腓肠肌后处死。测定血浆空腹血糖(FPG)、空腹血胰岛素(FINS)、TNF-α和IL-6浓度,计算IR指数(lgIRI),同时检测IRS-1及其Tyr磷酸化和Ser307磷酸化水平。结果3组大鼠生存曲线之间,均差异有统计学意义(P<0·01)。术后10%组和30%组TNF-α和IL-6均明显高于对照组(均P<0·01),其中30%组更高(均P<0·01)。术后10%组和30%组FPG、FINS和lgIRI在各时间点均明显高于对照组(均P<0·01),而30%组则明显高于10%组(P<0·01),术后FINS升高程度要明显高于FPG。对照组和30%组IRS-1均呈阳性位于骨骼肌细胞质内;对照组IRS-1Tyr磷酸化呈阳性,而30%组仅呈散在阳性;对照组IRS-1Ser307磷酸化呈阴性,而30%组呈强阳性。半定量分析显示30%组IRS-1在术后各个时间点与对照组相似(均P>0·05),IRS-1Tyr磷酸化在30%组术后各时间点明显低于对照组(均P<0·01),IRS-1Ser307磷酸化在术后各时间点明显高于对照组(均P<0·01)。lgIRI与IRS-1Tyr磷酸化呈显著负相关(r=-0·957,P<0·01),与IRS-1Ser307磷酸化呈显著正相关(r=0·955,P<0·01)。结论感染状态下骨骼肌细胞内IRS-1的含量不变,而是其Tyr磷酸化降低,同时Ser307磷酸化增强,其变化程度与机体胰岛素抵抗程度密切相关。
Objective To investigate the role of insulin receptor substrate-1 (IRS-1) and its serine phosphorylation (Ser307) and tyrosine (Tyr) phosphorylation in insulin resistance (IR) in skeletal muscle of rats with different degrees of infection. Methods SD rats were randomly divided into control group, 10% and 30% groups. In 10% and 30% of the rats, the infection model was made by cecum ligation and puncture. The ligation lengths were 10% and 30% of the total length, respectively. The control group was sham operation group. Three groups of rats were taken preoperatively and postoperative fasting blood and hind leg gastrocnemius were sacrificed. Plasma fasting blood glucose (FPG), fasting blood insulin (FINS), TNF-α and IL-6 levels were measured and the IR index (lgIRI) was calculated. IRS-1, Tyr phosphorylation and Ser307 phosphorylation were also measured. Results There were significant differences in survival curves between the three groups (P <0.01). After operation, the levels of TNF-α and IL-6 in 10% and 30% groups were significantly higher than those in control group (all P <0.01), of which 30% were higher (all P <0.01). The levels of FPG, FINS and lgIRI in 10% and 30% group were significantly higher than those in control group at each time point (all P <0.01), but were significantly higher in 30% and 10% groups (P <0.01 ), Postoperative FINS elevation was significantly higher than FPG. IRS-1Tyr phosphorylation in the control group was positive, while only 30% of the group was positive in the sporadic; IRS-1Ser307 phosphorylation in the control group was negative, while the control group 30% IRS-1 were positive in skeletal muscle cytoplasm; Group was strongly positive. Semi-quantitative analysis showed that IRS-1 in 30% group was similar to control group (all P> 0.05) at all time points after surgery, and IRS-1Tyr phosphorylation in 30% group was significantly lower than that in control group P <0.01). The phosphorylation of IRS-1Ser307 at each time point was significantly higher than that in the control group (all P <0.01). There was a significant negative correlation between lgIRI and IRS-1Tyr phosphorylation (r = -0.9557, P <0.01), which was positively correlated with IRS-1Ser307 phosphorylation (r = 0.955, P <0.01). CONCLUSIONS: The content of IRS-1 in skeletal muscle cells is not changed under the infection, but the phosphorylation of Tyr is decreased and the phosphorylation of Ser307 is enhanced. The degree of IRS-1 is closely related to the degree of insulin resistance.