Lactate metabolism is essential in early-onset mitochondrial myopathy

Myopathies secondary to mitochondrial electron transport chain (ETC) dysfunction can result in devastating disease. While the consequences of ETC defects have been extensively studied in culture, little in vivo data are available. Using a mouse model of severe, early-onset mitochondrial myopathy, we characterized the proteomic, transcriptomic, and metabolic characteristics of disease progression. Unexpectedly, ETC dysfunction in muscle results in reduced expression of glycolytic enzymes in our animal model and patient muscle biopsies. The decrease in glycolysis was mediated by loss of constitutive Hif1α signaling, down-regulation of the purine nucleotide cycle enzyme AMPD1, and activation of AMPK. In vivo isotope tracing experiments indicated that myopathic muscle relies on lactate import to supply central carbon metabolites. Inhibition of lactate import reduced steady-state levels of tricarboxylic acid cycle intermediates and compromised the life span of myopathic mice. These data indicate an unexpected mode of metabolic reprogramming in severe mitochondrial myopathy that regulates disease progression.