Modulating Folate Metabolism and Thymidylate Synthase in Diabetic Retinopathy: Zebrafish Insights and the Prophylactic Potential of Mesona chinensis

Diabetic retinopathy (DR) is a major microvascular complication of diabetes, yet safe and sustainable dietary strategies for long-term vascular protection remain limited. This study evaluated the functional food potential of Mesona chinensis (Mc) extract, a traditional botanical ingredient widely consumed in East Asia, in attenuating hyperglycemia-associated retinal angiopathy using larval and adult zebrafish models. Retinal vascular morphology and visual responsiveness were assessed together with folate profiling, gene and protein expression analyses, endothelial cell assays, metabolic rescue experiments, and molecular docking. High-glucose exposure altered folate-mediated one-carbon metabolism (OCM) and was associated with increased expression of thymidylate synthase (TYMS), a key enzyme involved in nucleotide biosynthesis. Notably, Mc extract attenuated glucose-induced retinal vascular hyper-branching and improved visual responsiveness in zebrafish larvae, effects accompanied by reduced TYMS expression under hyperglycemic conditions. In retro-orbitally glucose-injected adult zebrafish, Mc co-administration significantly suppressed pathological retinal vascular sprouting. Furthermore, dTTP supplementation reversed the anti-angiogenic effects of Mc, supporting the involvement of thymidylate metabolism. In silico analysis suggested that quercetin, a component of Mc, may interact with the TYMS active site, providing a potential mechanistic link between dietary compounds and metabolic regulation. Importantly, Mc treatment induced no detectable developmental toxicity under the tested conditions, in contrast to synthetic antifolate agents. Together, these findings indicate that Mc modulates hyperglycemia-associated retinal angiogenesis, potentially through regulation of folate-dependent metabolic pathways. This study highlights the potential of food-derived compounds in modulating metabolic pathways linked to vascular homeostasis and provides a foundation for future investigation in disease-relevant models.