Inducible chronic NAD deficiency in mice reveals multi-systemic phenotypical, metabolic, and transcriptional changes.

Nicotinamide adenine dinucleotide (NAD) is a metabolic cofactor regulating energy metabolism, epigenetics, DNA repair, and signaling. Although NAD declines with vitamin B3 deficiency, disease, and aging, systemic consequences of chronic depletion remain unclear. Here, we characterize an in vivo model of inducible NAD deficiency using acquired niacin dependency (ANDY) mice, in which NAD synthesis becomes dependent on dietary niacin. On a niacin-free diet, ANDY mice developed widespread tissue NAD depletion and sex-independent multisystem abnormalities, including kyphosis, reduced bone, lean, and fat mass, impaired exercise capacity, fur browning, frailty, cataracts, disrupted energy homeostasis, and shortened lifespan. NAD depletion was accompanied by tissue inflammation and cellular senescence. Transcriptomic analyses revealed broad metabolic remodeling and only partial overlap with chronological aging. Senolytic treatment partially improved functional decline without restoring NAD. In contrast, dietary niacin repletion reversed phenotypic, biochemical, senescence-associated, and transcriptional abnormalities, demonstrating that recovery of tissue NAD levels restored systemic function.