Department of Neuroscience, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
Proc Natl Acad Sci U S A. 2010 Nov 16;107(46):20087-92. doi: 10.1073/pnas.1008189107. Epub 2010 Nov 1.
At present, there are few means to track symptomatic stages of CNS aging. Thus, although metabolic changes are implicated in mtDNA mutation-driven aging, the manifestations remain unclear. Here, we used normally aging and prematurely aging mtDNA mutator mice to establish a molecular link between mitochondrial dysfunction and abnormal metabolism in the aging process. Using proton magnetic resonance spectroscopy and HPLC, we found that brain lactate levels were increased twofold in both normally and prematurely aging mice during aging. To correlate the striking increase in lactate with tissue pathology, we investigated the respiratory chain enzymes and detected mitochondrial failure in key brain areas from both normally and prematurely aging mice. We used in situ hybridization to show that increased brain lactate levels were caused by a shift in transcriptional activities of the lactate dehydrogenases to promote pyruvate to lactate conversion. Separation of the five tetrameric lactate dehydrogenase (LDH) isoenzymes revealed an increase of those dominated by the Ldh-A product and a decrease of those rich in the Ldh-B product, which, in turn, increases pyruvate to lactate conversion. Spectrophotometric assays measuring LDH activity from the pyruvate and lactate sides of the reaction showed a higher pyruvate → lactate activity in the brain. We argue for the use of lactate proton magnetic resonance spectroscopy as a noninvasive strategy for monitoring this hallmark of the aging process. The mtDNA mutator mouse allows us to conclude that the increased LDH-A/LDH-B ratio causes high brain lactate levels, which, in turn, are predictive of aging phenotypes.
目前，很少有方法可以追踪中枢神经系统衰老的症状阶段。因此，尽管代谢变化与 mtDNA 突变驱动的衰老有关，但表现仍不清楚。在这里，我们使用正常衰老和过早衰老的 mtDNA 突变体小鼠，建立了线粒体功能障碍与衰老过程中异常代谢之间的分子联系。使用质子磁共振波谱和 HPLC，我们发现正常衰老和过早衰老的小鼠在衰老过程中大脑中的乳酸水平增加了两倍。为了将乳酸的显著增加与组织病理学相关联，我们研究了呼吸链酶，并检测了正常衰老和过早衰老的小鼠关键大脑区域的线粒体功能障碍。我们使用原位杂交显示，大脑中乳酸水平的增加是由于乳酸脱氢酶的转录活性发生变化，从而促进了丙酮酸向乳酸的转化。五种四聚体乳酸脱氢酶（LDH）同工酶的分离显示，LDH-A 产物主导的同工酶增加，而富含 Ldh-B 产物的同工酶减少，这反过来又增加了丙酮酸向乳酸的转化。从反应的丙酮酸和乳酸侧测量 LDH 活性的分光光度测定显示，大脑中丙酮酸→乳酸的活性更高。我们认为使用乳酸质子磁共振波谱作为监测衰老过程这一特征的非侵入性策略。mtDNA 突变体小鼠使我们能够得出结论，增加的 LDH-A/LDH-B 比率导致大脑中高乳酸水平，而高乳酸水平反过来又可预测衰老表型。
