Nicotinamide N-Methyltransferase in Cardiovascular Diseases: Metabolic Regulator and Emerging Therapeutic Target

Cardiovascular disease (CVD) remains a leading cause of morbidity and mortality worldwide, arising from complex interactions among metabolic, genetic, and environmental factors. Nicotinamide N-methyltransferase (NNMT) has recently emerged as a key metabolic regulator in CVD pathogenesis. By consuming nicotinamide and methyl groups, NNMT perturbs epigenetic, metabolic, and redox pathways that are critical for cardiovascular health. NNMT-mediated NAD⁺ depletion impairs mitochondrial function, sirtuin (SIRT) activity, redox balance, and energy metabolism, thereby creating a pro-atherogenic environment. NNMT and its product 1-methylnicotinamide (1-MNA) show a complex duality: they modulate SIRT activity-particularly SIRT1 and SIRT3-to influence gluconeogenesis, cholesterol synthesis, lipogenesis, and mitochondrial antioxidant defenses. NNMT upregulation also elevates homocysteine levels, activating pro-inflammatory and pro-oxidative cascades (e.g., TLR4-NF-κB and STAT3-IL-1β). Growing evidence links NNMT to major CVD risk factors, including hyperlipidemia, hypertension, diabetes mellitus, and obesity. Thus, NNMT has a multifaceted role in cardiovascular health: while its enzymatic activity is often pathogenic (via NAD⁺/SAM consumption and homocysteine production), its metabolite 1-MNA can exert protective effects (via NRF2 activation and anti-thrombotic mechanisms). This duality highlights the need to delineate the molecular processes that balance these opposing actions. Experimental studies using small-molecule NNMT inhibitors and RNA interference have shown promising cardiometabolic benefits in preclinical models, including improved insulin sensitivity, reduced atherosclerosis, and attenuated cardiac dysfunction. However, no clinical trials have yet targeted NNMT specifically in CVD. Future research should clarify the tissue-specific functions of NNMT and translate these insights into novel therapeutic strategies.