Niacin Derivatives in MASLD: Metabolic and Therapeutic Insights.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is becoming increasingly prevalent worldwide, particularly among individuals with obesity and type 2 diabetes (T2D). MASLD remains potentially reversible in the early phases but, without timely intervention, it can progress to metabolic dysfunction-associated steatohepatitis (MASH) and hepatic fibrosis, which in turn may advance to cirrhosis and hepatocellular carcinoma over time. With no pharmacological treatments specifically indicated for MASLD, current therapeutic strategies include lifestyle modifications, including dietary modifications. Niacin and its molecular derivatives (collectively belonging to the vitamin B3 group) play a central role in metabolic processes, especially through their involvement in the biosynthesis of the oxidized form of nicotinamide adenine dinucleotide (NAD). A growing body of preclinical evidence suggests that reduced NAD levels are a hallmark of MASLD, and that NAD precursors may help attenuate disease progression through multiple mechanisms, including sirtuin 1 (SIRT1)-mediated inhibition of hepatic lipogenesis. Although these findings from experimental models suggest a potential role for niacin and related molecular derivatives as a modulators of MASLD-related pathways, evidence from human studies remains limited and inconsistent. For instance, interventional studies evaluating niacin or molecular derivatives supplementation have reported variable findings, with several trials showing limited meaningful benefits on MASLD-related outcomes. Consequently, further well-designed, controlled trials are needed to clarify therapeutic efficacy, dose-response relationship, and the feasibility of integrating niacin derivatives into dietary or therapeutic strategies aimed at reducing liver fat and improving adverse metabolic outcomes. This review aims to (i) summarize mechanistic insights on the role of niacin as a source of NAD on experimental MASLD and (ii) critically evaluate the available human evidence on the effect of supplemental niacin and derivatives in the prevention of MASLD development and its progression to MASH and fibrosis.