慢性高剂量胰岛素刺激猪脂肪细胞脂肪分解

Chronic high dose of insulin stimulates lipolysis in porcine adipocytes

摘要:

为研究慢性高剂量胰岛素对猪脂肪细胞脂肪分解的影响及其分子机制, 分化的猪脂肪细胞在PKA(Protein kinase A)或ERK(Extracellular signal-related kinase)抑制剂预处理或不处理的情况下, 再用不同浓度的胰岛素(0、200、400、800、1600 nmol/L)处理不同时间(24、48、72、96 h), 通过测定甘油释放量检测脂肪细胞的脂解率; 采用RT-PCR和Western blotting检测perilipin A和PPARg2的mRNA和蛋白表达。结果显示, 慢性高剂量胰岛素以剂量和时间依赖性的方式刺激猪脂肪细胞的脂肪分解, 并削弱脂肪细胞对异丙肾上腺素刺激的脂解应答; 同时显著下调perilipin A和PPARg2的mRNA及蛋白表达; 另外, PKA和ERK抑制剂均显著抑制胰岛素刺激的脂肪分解, 但仅ERK抑制剂显著逆转perilipin A基因表达的下调。由此推测, 慢性高剂量胰岛素通过ERK通路抑制perilipin A的表达, 进而刺激猪脂肪细胞的脂肪分解。

Abstract:

To explore the effect of chronic high dose of insulin on lipolysis in porcine adipocytes and the underlying molecular regulation mechanisms, we cultured primary porcine adipocytes and incubated them with different concentrations of insulin (0, 200, 400, 800, 1600 nmol/L) for 24~96 h in the absence or presence of specific protein kinase A (PKA) inhibitor or extracellular signal-related kinase (ERK) inhibitor. Then, we measured the glycerol release into the culture media as an indicator of the lipolysis, and observed the lipid accumulation morphology by phase-contrast microscopy. Further, we analyzed the gene expressions of perilipin A and peroxisome proliferator-activated receptor-gamma2 (PPARg2) with semi-quantitative RT-PCR and Western blotting, respectively. The results showed that chronic high dose of insulin stimulated lipolysis in differentiated porcine adipocytes in a dose- and time-dependent manner, and significantly attenuated the lipolytic response to isoprenaline. Meanwhile, the protein and mRNA expressions of PPARγ2 and perilipin A were significantly reduced. In addition, both PKA and ERK inhibitors significantly suppressed insulin-stimulated lipolysis, however, only ERK inhibitor reversed the insulin-induced down-regulation of perilipin A. These findings imply that chronic high dose of insulin stimulates lipolysis in porcine adipocytes by repressing perilipin A, which is involved in ERK pathway.