CD38 Inhibition to Prevent NAD+ Depletion and Restore Cellular Bioenergetics in Age-Related Metabolic Dysfunction

This hypothesis proposes that targeting CD38, the primary NAD±consuming enzyme, represents a more direct therapeutic approach to metabolic dysfunction than NAD+ precursor supplementation. CD38 expression increases dramatically with aging and inflammation, creating a futile cycle where enhanced NAD+ consumption outpaces biosynthetic capacity. Rather than attempting to replenish NAD+ pools through precursor loading, selective CD38 inhibition would preserve endogenous NAD+ levels by blocking its enzymatic degradation. This approach targets the root cause of NAD+ depletion rather than compensating for it. The hypothesis predicts that CD38 inhibitors like 78c or apigenin will restore NAD+/NADH ratios more effectively than nicotinamide riboside or nicotinamide mononucleotide supplementation. By preserving NAD+ availability, CD38 inhibition would maintain SIRT1/3 deacetylase activity, support mitochondrial biogenesis, and prevent the metabolic shift toward glycolysis characteristic of cellular senescence. This mechanism would be particularly relevant in tissues with high CD38 expression during aging, including immune cells, endothelial cells, and adipose tissue. The intervention could break the vicious cycle where inflammatory cytokines upregulate CD38, which depletes NAD+, which impairs mitochondrial function, which generates more oxidative stress and inflammation. Metabolomic profiling would reveal improved TCA cycle flux, enhanced fatty acid oxidation, and restored amino acid metabolism. Unlike NAD+ precursors that may have limited bioavailability and tissue distribution, CD38 inhibition would provide sustained NAD+ preservation across multiple cellular compartments.