Potential Role of Vitamin B6 as an Antioxidant via Pyridoxal-5'-Phosphate-Dependent Metabolic Pathways and Subsequent Activation of Nrf2 Signaling.

Accumulating evidence suggests that vitamin B6 (B6) deficiency among older adults is associated with sarcopenia, frailty, heart disease, and brain diseases. Oxidative stress and inflammation play key roles in cardiac and skeletal muscle and neuronal pathology. However, the detailed roles of B6 supplementation in oxidative stress and inflammation are not fully understood. Recent studies have shown that supplemental B6 upregulated the nuclear factor erythroid 2-like 2 (Nrf2) signaling pathway with the coordinated activation of antioxidant responses. Accumulating evidence suggests the potential of targeted Nrf2 signaling regulation in the treatment of aging-related musculoskeletal, heart, and brain diseases. Notably, dietary supplementation of B6 elevates the levels of several antioxidant metabolites, such as carnosine, anserine, taurine, hydrogen sulfide (H₂S), 5-methyltetrahydrofolate, kynurenic acid, 3-hydroxyanthranilic acid, and γ-aminobutyric acid (GABA) via the upregulation of pyridoxal 5'-phosphate (PLP)-dependent metabolic pathways, thereby linking to Nrf2 signaling activation. Furthermore, supplemental B6 stimulates glycogen breakdown through the PLP enzyme, glycogen phosphorylase, which in turn enhances the pentose phosphate pathway, thereby increasing nicotinamide adenine dinucleotide phosphate (NADPH) availability to regenerate glutathione (GSH). In this perspective article, we propose the potential role of B6 as an antioxidant mediated by the PLP-dependent multi-metabolic productions of antioxidant metabolites.