Post-COVID increase in N-methyl-2-pyridone-5-carboxamide (Met2PY) and N-methyl-4-pyridone-3-carboxamide (Met4PY) associates with inflammatory and endothelial activation markers

COVID-19 is associated with long-term vascular complications, but the underlying mechanisms remain incompletely understood. During infection, NAD+ homeostasis becomes dys-regulated, with excessive NAD+ consumption and enhanced catabolic flux through nicotinamide methylation pathways. This imbalance leads to NAD+ depletion accompanied by accumulation of pyridone metabolites, including N-methyl-2-pyridone-5-carboxamide (Met2PY) and N-methyl-4-pyridone-3-carboxamide (Met4PY). These derivatives have been linked to oxidative stress, endothelial dysfunction, and cardiovascular risk, yet their role in long COVID remains unclear. We enrolled 26 post-COVID patients with persistent cardiovascular symptoms and 8 healthy controls. Serum concentrations of Met2PY and Met4PY were quantified by LC/MS. High-sensitivity C-reactive protein (hsCRP), tumor necrosis factor-alpha (TNFα), interleukin-10 (IL-10), and soluble intercellular adhesion molecule-1 (sICAM-1) were measured to assess systemic inflammation and endothelial activation. Statistical analyses included group comparisons and correlation analyses. We observed significantly elevated Met2PY levels (0.770 ± 0.08 vs. 0.389 ± 0.09 µmol/l) and a trend toward increased Met4PY (0.095 ± 0.01 vs. 0.055 ± 0.01 µmol/l) in post-COVID patients compared with controls. Both metabolites positively correlated with hsCRP. Importantly, Met2PY was associated with an unfavorable cytokine profile (higher TNFα/IL-10 ratio) and increased sICAM-1 levels, whereas no such associations were observed for Met4PY. Persistent dysregulation of NAD+ metabolism and accumulation of pyridone metabolites, particularly Met2PY, are associated with markers of chronic endothelial activation and inflammation in long COVID. These findings support the potential utility of Met2PY as a biomarker to identify patients at higher risk for endothelial dysfunction and cardiovascular events, enabling more personalized risk stratification and follow-up.