Photoreceptor deletion of pyruvate dehydrogenase E1 subunit α1 induces retinal degeneration and reprograms retinal metabolism

Rod and cone photoreceptors are among the most energy-demanding cells in the body, exhibiting a high rate of ATP consumption. Their primary energy source is glucose, which is metabolized through both glycolysis and mitochondrial pyruvate oxidative phosphorylation. The pyruvate dehydrogenase E1 subunit α1 is a critical component of the pyruvate dehydrogenase, which catalyzes the conversion of pyruvate to acetyl-CoA, thereby regulating mitochondrial pyruvate metabolism. To determine the significance of mitochondrial pyruvate metabolism in these cells, we investigated the impact of photoreceptor-specific Pdha1 deletion in the mouse retina. Rod- or cone-specific Pdha1 knockout mice at 2-5 months were used. These mice were evaluated across multiple modalities, including retinal structure and integrity (morphometry), retinal function (electroretinogram), photoreceptor ultrastructure (transmission electron microscopy), retinal metabolic profiles (mass spectrometry), gene expression (RT-PCR), and retinal stress response (glial activation analysis). Mice with rod- or cone-specific Pdha1 deletion exhibited retinal degeneration phenotype, manifested by impaired retinal morphology and light responses and significant retinal glial activation. Mechanistically, these retinas displayed profound metabolism reprogramming, evidenced by changes in key glycolysis and decreased tricarboxylic acid (TCA) cycle intermediates, carbohydrates, amino acids, nucleotides and their derivatives. This metabolic remodeling was further supported by enhanced glycolysis and decreased TCA cycle gene expression and was accompanied by impaired mitochondrial morphology. Our findings demonstrate that PDHA1 is essential for photoreceptor energy metabolism and for maintaining both their structural and functional integrity, thus highlighting the critical importance of proper mitochondrial glucose metabolism for photoreceptor health.