Morten K J, Caky M, Matthews P M
Institute of Molecular Medicine and Department of Clinical Neurology, University of Oxford, John Radcliffe Hospital, Headington, UK.
Neurology. 1998 Nov;51(5):1331-5. doi: 10.1212/wnl.51.5.1331.
To test the effects of dichloroacetate (DCA) treatment on the rate of turnover of pyruvate dehydrogenase (PDH) subunits.
PDH deficiency is a nuclear-encoded mitochondrial disorder and a major recognized cause of neonatal encephalomyopathies associated with primary lactic acidosis. DCA has been used for its treatment. The primary mechanism of action of DCA has been thought to increase the proportion of enzyme in the activated, dephosphorylated state. However, this mechanism does not readily account for responses to treatment with mutations that do not obviously affect regulation of the enzyme complex.
PDH subunit turnover rates were measured using pulse-chase methods in a normal fibroblastic cell line before and after chronic (5-day) treatment with 5 mM DCA.
Chronic DCA treatment causes a more than twofold decrease in the apparent first-order rate constant for degradation of the PDH E1alpha subunit (kE1alpha(pre-DCA) = 0.025 +/- 0.006 hr(-1), n = 6; kE1alpha(post-DCA) = 0.011 /- 0.002 hr(-1), n = 3; p < 0.01) and a selective, progressive increase in the total cell PDH activity by 150 +/- 5% (p < 0.0005).
These results suggest an additional novel mechanism of action for the chronic DCA treatment of lactic acidemia; namely, inhibition of mitochondrial E1alpha subunit degradation leading to an increase in maximal PDH complex activity.
测试二氯乙酸（DCA）治疗对丙酮酸脱氢酶（PDH）亚基周转速率的影响。
PDH缺乏症是一种核编码的线粒体疾病，是与原发性乳酸性酸中毒相关的新生儿脑肌病的主要公认病因。DCA已被用于其治疗。DCA的主要作用机制被认为是增加处于活化、去磷酸化状态的酶的比例。然而，这种机制难以解释对那些不会明显影响酶复合物调节的突变的治疗反应。
在正常成纤维细胞系中，使用脉冲追踪法在5 mM DCA慢性（5天）治疗前后测量PDH亚基的周转速率。
慢性DCA治疗导致PDH E1α亚基降解的表观一级速率常数下降超过两倍（kE1α（DCA治疗前）= 0.025 +/- 0.006小时-1，n = 6；kE1α（DCA治疗后）= 0.011 /- 0.002小时-1，n = 3；p < 0.01），并且细胞总PDH活性选择性地、逐渐增加150 +/- 5%（p < 0.0005）。
这些结果提示了慢性DCA治疗乳酸性血症的另一种新的作用机制；即，抑制线粒体E1α亚基降解导致最大PDH复合物活性增加。
