ABSTRACT
Using molecular, biochemical, and untargeted stable isotope tracing approaches, we identify a previously unappreciated glutamine-derived α-ketoglutarate (αKG) energy-generating anaplerotic flux to be critical in mitochondrial DNA (mtDNA) mutant cells that harbor human disease-associated oxidative phosphorylation defects. Stimulating this flux with αKG supplementation enables the survival of diverse mtDNA mutant cells under otherwise lethal obligatory oxidative conditions. Strikingly, we demonstrate that when residual mitochondrial respiration in mtDNA mutant cells exceeds 45% of control levels, αKG oxidative flux prevails over reductive carboxylation. Furthermore, in a mouse model of mitochondrial myopathy, we show that increased oxidative αKG flux in muscle arises from enhanced alanine synthesis and release into blood, concomitant with accelerated amino acid catabolism from protein breakdown. Importantly, in this mouse model of mitochondriopathy, muscle amino acid imbalance is normalized by αKG supplementation. Taken together, our findings provide a rationale for αKG supplementation as a therapeutic strategy for mitochondrial myopathies.
Subject(s)
DNA, Mitochondrial/genetics , Glutamine/metabolism , Ketoglutaric Acids , Mitochondria , Mitochondrial Myopathies , Adaptation, Physiological , Alanine/metabolism , Animals , Disease Models, Animal , Energy Metabolism , HeLa Cells , Humans , Ketoglutaric Acids/metabolism , Ketoglutaric Acids/therapeutic use , Male , Mice , Mitochondria/genetics , Mitochondria/metabolism , Mitochondrial Myopathies/genetics , Mitochondrial Myopathies/metabolism , Mutation , Oxidative PhosphorylationABSTRACT
Energy metabolism could influence amyotrophic lateral sclerosis (ALS) and progressive lateral sclerosis (PLS) pathogenesis and the response to therapy. We developed a novel assay to simultaneously assess mitochondrial content and membrane potential in patients' skin fibroblasts. In ALS and PLS fibroblasts, membrane potential was increased and mitochondrial content decreased, relative to healthy controls. In ALS higher mitochondrial membrane potential correlated with age at diagnosis, and in PLS it correlated with disease severity. These unprecedented findings in ALS and PLS fibroblasts could shed new light onto disease pathogenesis and help in developing biomarkers to predict disease evolution and the individual response to therapy in motor neuron diseases.