A growing body of preclinical evidence suggests that reduced NAD<sup>+</sup> levels are a hallmark of MASLD, and that NAD<sup>+</sup> precursors may help attenuate disease progression through multiple mechanisms, including sirtuin 1 (SIRT1)-mediated inhibition of hepatic lipogenesis. The gene discussed is SIRT1; the disease is metabolic dysfunction-associated steatotic liver disease.