NAMPT and metabolic dysfunction-associated steatotic liver disease: It is reported that hepatic NAD+ level is decreased in aged mice and humans with NAFLD; middle-age dominant-negative, enzymically inactive nicotinamide phosphoribosyltransferase transgenic mice given normal chow exhibit systemic NAD+ reduction and have moderate NAFLD-related phenotypes, such as enhanced oxidative stress, lipid accumulation, increased inflammation, and impaired insulin sensitivity in the liver; conversely, these NAFLD phenotypes driven by NAD+ deficiency or high-fat diet can be completely rescued by oral administration of NR.15