High brain lactate is a hallmark of aging and caused by a shift in the lactate dehydrogenase A/B ratio.
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.
Department of Neuroscience, Karolinska Institutet, SE-171 77 Stockholm, Sweden. rossja@nida.nih.gov
Jaime M
JM
Ross
Johanna
J
Öberg
Stefan
S
Brené
Giuseppe
G
Coppotelli
Mügen
M
Terzioglu
Karin
K
Pernold
Michel
M
Goiny
Rouslan
R
Sitnikov
Jan
J
Kehr
Aleksandra
A
Trifunovic
Nils-Göran
NG
Larsson
Barry J
BJ
Hoffer
Lars
L
Olson
D000375:Aging / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology*; D004272:DNA, Mitochondrial / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D000080864:Lactate Dehydrogenase 5; D019344:Lactic Acid / Q000378:metabolism*; D051379:Mice; D008928:Mitochondria / Q000201:enzymology / Q000473:pathology; D009154:Mutation / Q000235:genetics; D009928:Organ Specificity
D004272:DNA, Mitochondrial; D007527:Isoenzymes; D019344:Lactic Acid; D007770:L-Lactate Dehydrogenase; D000080864:Lactate Dehydrogenase 5; C409667:lactate dehydrogenase 1