Spatial alteration of metabolites in diabetic cortical cataracts: New insight into lactate

This study aimed to use metabolomics to accurately reveal alterations in metabolites and potential regulatory mechanisms in patients with diabetic cortical cataracts (DCC). We first collected cortical samples from different pathological areas of the same lens in DCC patients for metabolomics. Then, we used transcriptomic analysis to study lactate's effect on gene expression in human lens epithelial cells (HLECs). An in vitro rat lens culture assay evaluated lactate's impact on lens transparency, and WB and immunofluorescence assessed lactate-induced apoptosis and oxidative damage in rat LECs. Furthermore, CHIP sequencing and LC-MS identified H3K18la separately modified genes and potential lactylation proteins in HLECs. Immunoprecipitation validated lactylation levels of proteins. Our findings identified 11 upregulated and 18 downregulated metabolites in the opacity zone of LFCs (OZ-LFCs) compared to the clear zone (CZ-LFCs) in DCC patients. We confirmed the differential lactate content between OZ-LFCs and CZ-LFCs and, through transcriptomic analysis, discovered that lactate affects gene expression, protein metabolism, and DNA repair in primary Human Lens epithelial cells (HLECs). Lactate-induced apoptosis and DNA repair hastened lens opacity in a high-sugar rat lens culture model. Lactylation-MS and H3K18la-ChIP sequencing revealed 591 H3K18la-modified genes and 953 lactylation proteins in HLECs. PKM2 and NPM1 lactylation was confirmed through immunoprecipitation. These findings improve our grasp of spatial dynamics in DCC patient metabolomics and suggest a new research path into lactylation modification to understand lactate's role in cataract formation.