Endotoxin induced hyperlactatemia and hypoglycemia is linked to decreased mitochondrial phosphoenolpyruvate carboxykinase
Endotoxin induced hyperlactatemia and hypoglycemia is linked to decreased mitochondrial phosphoenolpyruvate carboxykinase
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DOI：
10.1016/j.lfs.2009.02.024
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发表时间：
2009-05-22
期刊：
影响因子：
6.1
通讯作者：
Corder, Roger
中科院分区：
文献类型：
--
作者：
Caton, Paul W.;Nayuni, Nanda K.;Corder, Roger
目的：磷酸烯醇丙酮酸羧激酶 (PEPCK) 是糖异生的限速酶，在回收乳酸用于葡萄糖生产方面发挥着关键作用。它被合成为两个独立的异构体；细胞质（PEPCK-C，基因代码；PCK1）和线粒体（PEPCK-M，基因代码；PCK2）。先前对内毒素血症中糖异生的研究仅集中于 PCK1。我们在内毒素休克大鼠模型和培养的肝细胞中研究了两种亚型在肝和肾糖异生中的相对作用。主要方法：给大鼠施用脂多糖（6 mg/kg；LPS）6小时。将培养的细胞与含有或不含肿瘤坏死因子α (1 - 10 ng/ml) 的乳酸 (5 mM) 一起孵育。对大鼠肝脏和肾脏样品以及培养的细胞进行亚细胞分级分离，产生线粒体和细胞质级分，用于 PEPCK 活性测定。使用定量 RT-PCR 测量 PCK1 和 PCK2 mRNA 水平。主要发现：在大鼠内毒素血症中，与假手术对照组相比，肝脏 PCK2 mRNA 和 PEPCK-M 酶活性分别降低 53% 和 38%。肝脏 PCK1 mRNA 水平增加 44%，但 PEPCK-C 酶活性保持不变。肝脏 PEPCK-M 的变化与明显的低血糖和高乳酸血症以及血浆白细胞介素 1 β (IL1β) 升高同时发生。将培养的肝细胞与 TNF-α 一起孵育可抑制乳酸诱导的葡萄糖产生、PCK2 mRNA 水平和 PEPCK-M 酶活性的增加，但对 PCK1 mRNA 水平或 PEPCK-C 活性没有影响。意义：这些结果表明，肝脏 PEPCK-M 的减少在内毒素血症中高乳酸血症和低血糖的表现中发挥关键作用。 (C) 2009 Elsevier Inc. 保留所有权利。
Aims: Phosphoenolpyruvate carboxykinase (PEPCK) is the rate limiting enzyme for gluconeogenesis, and plays a key role in recycling lactate for glucose production. It is synthesized as two separate isoforms; cytosolic (PEPCK-C, gene code; PCK1) and mitochondrial (PEPCK-M, gene code; PCK2). Previous studies of gluconeogenesis in endotoxemia have focused solely on PCK1. We investigated the relative roles of the two isoforms in hepatic and renal gluconeogenesis in a rat model of endotoxic shock, and in cultured hepatocytes.Main methods: Rats were administered lipopolysaccharide (6 mg/kg; LPS) for 6 h. Cultured cells were incubated with lactate (5 mM) with or without tumor necrosis factor alpha (1 - 10 ng/ml). Rat liver and kidney samples as well as cultured cells were subjected to subcellular fractionation to produce mitochondrial and cytosolic fractions for PEPCK activity assay. PCK1 and PCK2 mRNA levels were measured using quantitative RT-PCR.Key findings: In rat endotoxemia, hepatic PCK2 mRNA and PEPCK-M enzyme activity decreased by 53% and 38%, compared to sham controls. Hepatic PCK1 mRNA levels increased by 44%, but PEPCK-C enzyme activity remained unchanged. The changes in hepatic PEPCK-M coincided with a marked hypoglycemia and hyperlactatemia as well as elevated plasma interleukin 1 beta (IL1beta). Incubation of cultured hepatocytes with TNF-alpha inhibited lactate-induced increases in glucose production, PCK2 mRNA levels and PEPCK-M enzyme activity but had no effect on PCK1 mRNA levels or PEPCK-C activity.Significance: These results indicate that decreases in hepatic PEPCK-M play a key role in the manifestation of hyperlactatemia and hypoglycemia in endotoxemia. (C) 2009 Elsevier Inc. All rights reserved.