Rewiring of Glutamine Metabolism Is a Bioenergetic Adaptation of Human Cells with Mitochondrial DNA Mutations

Using molecular, biochemical, and untargeted stable isotope tracing approaches, we identify a previously unappreciated glutamine-derived alpha-ketoglutarate (alpha KG ) 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 alpha KG 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, alpha KG oxidative flux prevails over reductive carboxylation. Furthermore, in a mouse model of mitochondrial myopathy, we show that increased oxidative alpha KG 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 alpha KG supplementation. Taken together, our findings provide a rationale for alpha KG supplementation as a therapeutic strategy for mitochondrial myopathies.