Combined ketone body and glutamine supplementation restores aerobic energy production in AGC1-deficient neuronal progenitors

: AGC1 deficiency is a rare, early-onset encephalopathy caused by mutations in the SLC25A12 gene, encoding the mitochondrial aspartate/glutamate carrier isoform 1 (AGC1). Patients exhibit epileptic encephalopathy, cerebral hypomyelination, severe hypotonia, and global developmental delay. A hallmark biochemical feature of AGC1 deficiency is reduced brain N-acetylaspartate (NAA), a key metabolite involved in myelin lipid synthesis. However, the underlying mechanisms leading to the hypomyelinating phenotype remain unclear. In this study, we generated neuronal progenitors (NPs) derived from human-induced pluripotent stem cells (hiPSCs) of AGC1-deficient patients to investigate the metabolic and bioenergetic consequences of AGC1 loss. We demonstrated that AGC1-deficient NPs exhibit impaired proliferation, increased apoptosis, and a metabolic shift toward a hyperglycolytic phenotype due to defective mitochondrial pyruvate oxidation. RNA sequencing revealed downregulation of mitochondrial pyruvate carrier MPC1/2, limiting pyruvate-driven oxidative phosphorylation (OXPHOS) and reinforcing glycolysis as the primary energy source. Despite this metabolic shift, AGC1-deficient mitochondria retained the potential for OXPHOS when alternative anaplerotic substrates were provided. Notably, the administration of ketone bodies, in combination with glutamine, fully restored mitochondrial respiration, suggesting a mechanistic basis for the clinical improvements observed in AGC1-deficient patients undergoing ketogenic diet therapy. Our study highlights the importance of alternative metabolic pathways in maintaining neuronal energy homeostasis in AGC1 deficiency and offers insights into potential therapeutic strategies aimed at bypassing the mitochondrial pyruvate oxidation defect.