Double-Pronged NAD Preservation: Delaying Cellular Senescence and Initiating Musculoskeletal Regeneration

In the context of population aging, musculoskeletal fitness has emerged as a cornerstone of overall well-being and injury prevention, relying on the coordinated function of cartilage, bone, and muscle. Drawing on the principle of "increasing income and reducing expenditure," we propose a combinatorial formulation consisting of the nicotinamide adenine dinucleotide (NAD) precursor nicotinamide mononucleotide (NMN) and the NAD⁺-consuming enzyme inhibitor apigenin (API), hereafter referred to as the "N + A" regimen, to enhance NAD⁺ reserves. Our results revealed that the N + A formulation alleviated cellular senescence, thereby promoting the differentiation of skeletal precursor cells into chondrocytes, osteoblasts, and myocytes for the reconstruction of the musculoskeletal system. Oral administration of the N + A formulation alleviated cartilage degeneration, bone loss, and muscle atrophy; additionally, it enhanced exercise capacity in aged mice. Mechanistically, the N + A strategy preserves NAD⁺ levels, which are subsequently utilized by mitochondrial sirtuin 3 (SIRT3) to promote deacetylation modifications and alleviate the senescent phenotype. Moreover, oral administration of N + A indirectly enhanced the synthesis of the metabolite phytosphingosine (PHS) by the intestinal microbiota members Coriobacteriaceae_UCG-002 and Ruminococcus, thereby alleviating age-related degeneration. In summary, our findings demonstrate that enhancing the NAD⁺ reservoir represents a promising strategy for promoting musculoskeletal regeneration, and we developed a rational combinatorial regimen with potential for clinical translation.