Dilinoleoyl-phosphatidic acid mediates reduced IRS-1 tyrosine phosphorylation in rat skeletal muscle cells and mouse muscle
Dilinoleoyl-phosphatidic acid mediates reduced IRS-1 tyrosine phosphorylation in rat skeletal muscle cells and mouse muscle
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DOI：
10.1007/s00125-007-0709-x
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发表时间：
2007-08-01
期刊：
影响因子：
8.2
通讯作者：
Schmitz-Peiffer, C.
中科院分区：
文献类型：
--
作者：
Cazzolli, R.;Mitchell, T. W.;Schmitz-Peiffer, C.
目的/假设骨骼肌中的胰岛素抵抗与脂质过度供应密切相关，但细胞内代谢产物和潜在机制尚不清楚。因此，我们试图确定的脂质中间体，通过它的共同的不饱和脂肪酸亚油酸导致缺陷IRS-1信号在L 6肌管和小鼠骨骼muscle.Materials and Methods细胞预处理与1 mmol/L亚油酸24小时。随后胰岛素刺激的IRS-1酪氨酸磷酸化及其与磷脂酰肌醇3-激酶的p85亚基的关联通过免疫印迹法测定。细胞内脂质种类和蛋白激酶C的激活受到过表达的二酰基甘油激酶α，它优先将不饱和二酰基甘油转化为磷脂酸，或通过抑制溶血磷脂酸酰基转移酶与异茶碱，减少磷脂酸的合成。磷脂酸物种在亚油酸处理的细胞或胰岛素抵抗的小鼠喂养的红花油为基础的高脂肪饮食，富含亚油酸酯的肌肉进行了分析，通过massspectrometry.Results亚油酸酯预处理降低IRS-1酪氨酸磷酸化和p85协会。过表达的二酰基甘油激酶β逆转激活蛋白激酶C亚型亚油酸，但矛盾的是进一步减少IRS-1酪氨酸磷酸化。相反，异茶碱治疗恢复IRS-1磷酸化。质谱分析表明，二亚油酰基磷脂酸含量从检测不到的水平增加到几乎20%的总磷脂酸在L 6细胞和8%的总在肌肉中的小鼠喂食高脂肪饮食。胶束含有二亚油酰基磷脂酸特异性抑制IRS-1酪氨酸磷酸化和糖原合成在L 6 celles.Conclusions/interpretation这些数据表明，亚油酸衍生的磷脂酸是一种新的脂质物种，有助于独立的蛋白激酶C IRS-1信号缺陷，在肌肉细胞中的脂质供应过剩。
Aims/hypothesis Insulin resistance in skeletal muscle is strongly associated with lipid oversupply, but the intracellular metabolites and underlying mechanisms are unclear. We therefore sought to identify the lipid intermediates through which the common unsaturated fatty acid linoleate causes defects in IRS-1 signalling in L6 myotubes and mouse skeletal muscle.Materials and methods Cells were pre-treated with 1 mmol/l linoleate for 24 h. Subsequent insulin-stimulated IRS-1 tyrosine phosphorylation and its association with the p85 subunit of phosphatidylinositol 3-kinase were determined by immunoblotting. Intracellular lipid species and protein kinase C activation were modulated by overexpression of diacylglycerol kinase epsilon, which preferentially converts unsaturated diacylglycerol into phosphatidic acid, or by inhibition of lysophosphatidic acid acyl transferase with lisofylline, which reduces phosphatidic acid synthesis. Phosphatidic acid species in linoleate-treated cells or muscle from insulin-resistant mice fed a safflower oil-based high-fat diet that was rich in linoleate were analysed by mass spectrometry.Results Linoleate pretreatment reduced IRS-1 tyrosine phosphorylation and p85 association. Overexpression of diacylglycerol kinase epsilon reversed the activation of protein kinase C isoforms by linoleate, but paradoxically further diminished IRS-1 tyrosine phosphorylation. Conversely, lisofylline treatment restored IRS-1 phosphorylation. Mass spectrometry indicated that the dilinoleoyl-phosphatidic acid content increased from undetectable levels to almost 20% of total phosphatidic acid in L6 cells and to 8% of total in the muscle of mice fed a high-fat diet. Micelles containing dilinoleoyl-phosphatidic acid specifically inhibited IRS-1 tyrosine phosphorylation and glycogen synthesis in L6 cells.Conclusions/interpretation These data indicate that linoleate-derived phosphatidic acid is a novel lipid species that contributes independently of protein kinase C to IRS-1 signalling defects in muscle cells in response to lipid oversupply.