Alterations in the expression and cellular localization of protein kinase C isozymes epsilon and theta are associated with insulin resistance in skeletal muscle of the high-fat-fed rat
Alterations in the expression and cellular localization of protein kinase C isozymes epsilon and theta are associated with insulin resistance in skeletal muscle of the high-fat-fed rat
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DOI：
10.2337/diabetes.46.2.169
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发表时间：
1997-02-01
期刊：
影响因子：
7.7
通讯作者：
Biden, TJ
中科院分区：
文献类型：
--
作者：
SchmitzPeiffer, C;Browne, CL;Biden, TJ
我们已经测试了这一假设，蛋白激酶C（PKC）同工酶的水平和细胞位置的变化可能与高脂喂养大鼠骨骼肌胰岛素抵抗的发展。血脂测量结果表明，甘油三酯和甘油二酯，PKC的激活剂，分别升高了四倍和两倍。PKC活性测定表明，膜相关的钙非依赖性PKC的比例也增加。通过免疫印迹法测定，对照组和脂肪喂养大鼠之间的总（颗粒加胞质）PKC α、β和ζ水平没有差异。然而，在脂肪喂养的大鼠的红色肌肉中，颗粒与胞质PKC β的比例增加了近六倍，表明慢性激活。相比之下，胞质PKC θ的量下调至对照组的45%，而颗粒与胞质水平的比率增加，表明慢性激活和下调的组合。有趣的是，虽然葡萄糖钳夹大鼠的胰岛素输注增加了红肌颗粒部分中PKC θ的比例，但这是由脂肪喂养增强的，这表明易位是脂质通量改变的结果，而不是胰岛素信号传导中的近端事件。从个别大鼠的PKC β和θ测量与红色腓肠肌的甘油三酯含量，他们没有相关的血糖，这是不升高的脂肪喂养的大鼠，这表明他们不是简单的高血糖症的后果。我们的研究结果表明，这些具体的改变，在PKC β和PKC θ可能有助于增加脂质的可用性和肌肉胰岛素抵抗之间的联系，以前使用高脂肪喂养大鼠描述。
We have tested the hypothesis that changes in the levels and cellular location of protein kinase C (PKC) isozymes might be associated with the development of insulin resistance in skeletal muscles from the high-fat-fed rat. Lipid measurements showed that triglyceride and diacylglycerol, an activator of PKC, were elevated four- and twofold, respectively. PKC activity assays indicated that the proportion of membrane-associated calcium-independent PKC was also increased. As determined by immunoblotting, total (particulate plus cytosolic) PKC alpha, epsilon, and zeta levels were not different between control and fat-fed rats. However, the ratio of particulate to cytosolic PKC epsilon in red muscles from fat-fed rats was increased nearly sixfold, suggesting chronic activation. In contrast, the amount of cytosolic PKC theta was downregulated to 45% of control, while the ratio of particulate to cytosolic levels increased, suggesting a combination of chronic activation and downregulation. Interestingly, while insulin infusion in glucose-clamped rats increased the proportion of PKC theta in the particulate fraction of red muscle, this was potentiated by fat-feeding, suggesting that the translocation is a consequence of altered lipid flux rather than a proximal event in insulin signaling. PKC epsilon and theta measurements from individual rats correlated with triglyceride content of red gastrocnemius muscle; they did not correlate with plasma glucose, which was not elevated in fat-fed rats, suggesting that they were not simply a consequence of hyperglycemia. Our results suggest that these specific alterations in PKC epsilon and PKC theta might contribute to the link between increased lipid availability and muscle insulin resistance previously described using high-fat-fed rats.