NAD+-Dependent Transcriptional Upregulation of MCT1 to Restore Neuronal Ketone Metabolism

This hypothesis proposes that NAD+ precursor supplementation can restore neuronal ketone body utilization by activating SIRT1-mediated transcriptional upregulation of MCT1 (monocarboxylate transporter 1). In neurodegenerative conditions, chronic PARP1 activation depletes cellular NAD+ pools, leading to reduced SIRT1 activity and subsequent downregulation of MCT1 expression. This creates a metabolic bottleneck where neurons cannot efficiently import ketone bodies as an alternative fuel source, exacerbating energy deficits. By supplementing with NAD+ precursors (such as nicotinamide riboside or nicotinamide mononucleotide), cellular NAD+ levels are restored, reactivating SIRT1 deacetylase activity. Active SIRT1 then deacetylates key transcription factors and chromatin proteins at the SLC16A1 promoter region, enhancing MCT1 gene expression. Increased MCT1 protein levels restore the neuron’s capacity to import β-hydroxybutyrate and acetoacetate, providing crucial ketone-derived acetyl-CoA for mitochondrial ATP production. This mechanism bypasses glucose-dependent energy pathways that may be compromised in neurodegeneration. The hypothesis predicts that NAD+ precursor treatment will increase both MCT1 mRNA and protein expression in neurons, correlating with improved ketone uptake rates and enhanced cellular bioenergetics. This restoration of ketone metabolism could provide neuroprotection by maintaining ATP levels, reducing oxidative stress, and supporting synaptic function even when glucose metabolism is impaired.