title: Lactate metabolism during exercise in patients with mitochondrial myopathy.
abstract: Patients with mitochondrial DNA mutations often have elevated plasma lactate at rest and during exercise, but it is unknown whether the high lactate levels are caused by a high production, an impaired oxidation or a combination. We studied lactate kinetics in 10 patients with mtDNA mutations and 10 matched healthy control subjects at rest and during cycle exercise with a combination of femoral arterio-venous differences of lactate, and lactate tracer dilution methodology. During exercise, lactate concentration and production rates were several-fold higher in patients, but despite mitochondrial dysfunction, lactate was oxidized in muscle to the same extent as in healthy control subjects. This surprisingly high ability to burn lactate in working muscle with defective mitochondria, probably relates to the variability of oxidative capacity among muscle fibers. The data suggests that lactate is not solely an indicator of impaired oxidative capacity, but an important fuel for oxidative metabolism, even in muscle with severely impaired mitochondrial function.
authors.affiliation: Neuromuscular Research Unit, Section 3342, Department of Neurology, Rigshospitalet, University of Copenhagen, Denmark. Tina@Dysgaard.dk
authors.forename: Tina D
authors.initials: TD
authors.lastname: Jeppesen
authors.forename: Mette C
authors.initials: MC
authors.lastname: Orngreen
authors.forename: Gerrit
authors.initials: G
authors.lastname: Van Hall
authors.forename: John
authors.initials: J
authors.lastname: Vissing
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001794:Blood Pressure / Q000502:physiology; D004272:DNA, Mitochondrial / Q000235:genetics; D004837:Epinephrine / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007328:Insulin / Q000378:metabolism; D019344:Lactic Acid / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D017240:Mitochondrial Myopathies / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology*; D009154:Mutation / Q000235:genetics; D009638:Norepinephrine / Q000378:metabolism; D010101:Oxygen Consumption; D013997:Time Factors
chemical_list: D004272:DNA, Mitochondrial; D007328:Insulin; D019344:Lactic Acid; D009638:Norepinephrine; D004837:Epinephrine
keywords: Lactate acidosis; Lactate kinetics; Mitochondrial myopathy; Premature fatigue