NAD Depletion in Skeletal Muscle does not Compromise Muscle Function or Accelerate Aging

NAD is a ubiquitous electron carrier essential for energy metabolism and the post-translational modification of numerous regulatory proteins. Perturbation of NAD metabolism is considered detrimental to health, with NAD depletion commonly thought to promote aging. However, the extent to which cellular NAD concentration can be decreased without deleterious repercussions is unclear. We generated a mouse model where nicotinamide phosphoribosyltransferase (NAMPT)-mediated NAD+ biosynthesis is disrupted in adult skeletal muscle. The resulting 85% decrease in muscle NAD+ abundance was associated with preserved tissue integrity and functionality, as demonstrated by its unchanged morphology, contractility, and exercise tolerance. This lack of defects was corroborated by intact mitochondrial respiratory capacity and unaffected muscle transcriptomic and proteomic profiles. Furthermore, lifelong NAD depletion did not accelerate muscle aging or impair whole-body metabolism. Collectively, these findings indicate that NAD depletion does not contribute to age-related decline in skeletal muscle function. We profiled DNA methylation in 48 samples. The experiment is a two-way factorial design with 23 old and 25 young mice, 25 of which were wild-type and 23 of which where NAMPT was knocked out in adult skeletal muscle.