调节脂肪组织丙酮酸脱氢酶的机制

Mechanisms regulating adipose-tissue pyruvate dehydrogenase.

作者信息

Martin B R, Denton R M, Pask H T, Randle P J

出版信息

Biochem J. 1972 Sep;129(3):763-73. doi: 10.1042/bj1290763.

DOI:10.1042/bj1290763

PMID:4658997

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1174178/

Abstract

Isolated rat epididymal fat-cell mitochondria showed an inverse relationship between ATP content and pyruvate dehydrogenase activity consistent with competitive inhibition of pyruvate dehydrogenase kinase by ADP. At constant ATP concentration pyruvate rapidly activated pyruvate dehydrogenase in fat-cell mitochondria, an observation consistent with inhibition of fat-cell pyruvate dehydrogenase kinase by pyruvate. Pyruvate dehydrogenase in fat-cell mitochondria was also activated by nicotinate (100mum) and by extramitochondrial Na(+) (replacing K(+)) but not by ouabain or insulin. 2. In rat epididymal fat-pads incubated in vitro pyruvate dehydrogenase was activated by addition of insulin in the absence of substrate or in the presence of glucose (10mm) or fructose (10mm). Glucose and fructose activated the dehydrogenase in the absence or in the presence of insulin, and pyruvate also activated in the absence of insulin. It is concluded that extracellular glucose, fructose and pyruvate may activate the dehydrogenase by raising intracellular pyruvate and that insulin may activate the dehydrogenase by some other mechanism. 3. Ouabain (300mum) and medium in which K(+) was replaced by Na(+), activated pyruvate dehydrogenase in epididymal fat-pads. Prostaglandin E(1) (1mug/ml), 5-methylpyrazole-3-carboxylate (10mum) and nicotinate (10mum), which are as effective as insulin as inhibitors of lipolysis and which like insulin lower tissue concentration of cyclic AMP (adenosine 3':5'-cyclic monophosphate), did not activate pyruvate dehydrogenase. Higher concentrations of prostaglandin E(1) (10mug/ml) and nicotinate (100mum) produced some activation of the dehydrogenase. 4. It is concluded that the activation of pyruvate dehydrogenase by insulin is not due to the antilipolytic effect of the hormone and that the action of insulin in lowering adipose-cell concentrations of cyclic AMP does not afford an obvious explanation for the effect of the hormone on pyruvate dehydrogenase. The possibility that the effects of insulin, ouabain and K(+)-free medium may be mediated by Ca(2+) is discussed.

摘要

分离出的大鼠附睾脂肪细胞线粒体显示，ATP含量与丙酮酸脱氢酶活性呈负相关，这与ADP对丙酮酸脱氢酶激酶的竞争性抑制作用相一致。在ATP浓度恒定的情况下，丙酮酸能迅速激活脂肪细胞线粒体中的丙酮酸脱氢酶，这一观察结果与丙酮酸对脂肪细胞丙酮酸脱氢酶激酶的抑制作用相符。脂肪细胞线粒体中的丙酮酸脱氢酶也可被烟酸（100μM）和线粒体外的Na⁺（取代K⁺）激活，但不受哇巴因或胰岛素的激活。2. 在体外培养的大鼠附睾脂肪垫中，在无底物或存在葡萄糖（10mM）或果糖（10mM）的情况下，添加胰岛素可激活丙酮酸脱氢酶。葡萄糖和果糖在有无胰岛素的情况下均可激活该脱氢酶，丙酮酸在无胰岛素时也可激活该脱氢酶。由此得出结论，细胞外葡萄糖、果糖和丙酮酸可能通过提高细胞内丙酮酸水平来激活脱氢酶，而胰岛素可能通过其他机制激活脱氢酶。3. 哇巴因（300μM）以及用Na⁺取代K⁺的培养基可激活附睾脂肪垫中的丙酮酸脱氢酶。前列腺素E₁（1μg/ml）、5 - 甲基吡唑 - 3 - 羧酸盐（10μM）和烟酸（10μM），它们作为脂解抑制剂与胰岛素一样有效，且与胰岛素一样能降低组织中环磷酸腺苷（腺苷3':5'-环一磷酸）的浓度，但它们并不能激活丙酮酸脱氢酶。更高浓度的前列腺素E₁（10μg/ml）和烟酸（100μM）可使该脱氢酶产生一定程度的激活。4. 得出结论，胰岛素对丙酮酸脱氢酶的激活作用并非由于该激素的抗脂解作用，且胰岛素降低脂肪细胞中环磷酸腺苷浓度的作用并不能明显解释该激素对丙酮酸脱氢酶的作用。文中讨论了胰岛素、哇巴因和无钾培养基的作用可能由Ca²⁺介导的可能性。