Cassese Angela, Esposito Iolanda, Fiory Francesca, Barbagallo Alessia P M, Paturzo Flora, Mirra Paola, Ulianich Luca, Giacco Ferdinando, Iadicicco Claudia, Lombardi Angela, Oriente Francesco, Van Obberghen Emmanuel, Beguinot Francesco, Formisano Pietro, Miele Claudia
Dipartimento di Biologia e Patologia Cellulare e Molecolare and Istituto di Endocrinologia ed Oncologia Sperimentale del Consiglio Nazionale delle Ricerche, Università degli Studi di Napoli Federico II, Naples 80131, Italy.
J Biol Chem. 2008 Dec 26;283(52):36088-99. doi: 10.1074/jbc.M801698200. Epub 2008 Oct 27.
Chronic hyperglycemia promotes insulin resistance at least in part by increasing the formation of advanced glycation end products (AGEs). We have previously shown that in L6 myotubes human glycated albumin (HGA) induces insulin resistance by activating protein kinase Calpha (PKCalpha). Here we show that HGA-induced PKCalpha activation is mediated by Src. Coprecipitation experiments showed that Src interacts with both the receptor for AGE (RAGE) and PKCalpha in HGA-treated L6 cells. A direct interaction of PKCalpha with Src and insulin receptor substrate-1 (IRS-1) has also been detected. In addition, silencing of IRS-1 expression abolished HGA-induced RAGE-PKCalpha co-precipitation. AGEs were able to induce insulin resistance also in vivo, as insulin tolerance tests revealed a significant impairment of insulin sensitivity in C57/BL6 mice fed a high AGEs diet (HAD). In tibialis muscle of HAD-fed mice, insulin-induced glucose uptake and protein kinase B phosphorylation were reduced. This was paralleled by a 2.5-fold increase in PKCalpha activity. Similarly to in vitro observations, Src phosphorylation was increased in tibialis muscle of HAD-fed mice, and co-precipitation experiments showed that Src interacts with both RAGE and PKCalpha. These results indicate that AGEs impairment of insulin action in the muscle might be mediated by the formation of a multimolecular complex including RAGE/IRS-1/Src and PKCalpha.
慢性高血糖至少部分通过增加晚期糖基化终产物(AGEs)的形成来促进胰岛素抵抗。我们之前已经表明,在L6肌管中,人糖化白蛋白(HGA)通过激活蛋白激酶Cα(PKCα)诱导胰岛素抵抗。在此我们表明,HGA诱导的PKCα激活是由Src介导的。共沉淀实验表明,在HGA处理的L6细胞中,Src与AGE受体(RAGE)和PKCα相互作用。还检测到PKCα与Src和胰岛素受体底物-1(IRS-1)之间存在直接相互作用。此外,IRS-1表达的沉默消除了HGA诱导的RAGE-PKCα共沉淀。AGEs在体内也能够诱导胰岛素抵抗,因为胰岛素耐量试验显示,喂食高AGEs饮食(HAD)的C57/BL6小鼠的胰岛素敏感性显著受损。在喂食HAD的小鼠的胫骨肌中,胰岛素诱导的葡萄糖摄取和蛋白激酶B磷酸化降低。这与PKCα活性增加2.5倍相平行。与体外观察结果相似,喂食HAD的小鼠的胫骨肌中Src磷酸化增加,共沉淀实验表明,Src与RAGE和PKCα都相互作用。这些结果表明,AGEs对肌肉中胰岛素作用的损害可能是由包括RAGE/IRS-1/Src和PKCα的多分子复合物的形成介导的。