Intestinal metabolite TMAO promotes CKD progression by stimulating macrophage M2 polarization through histone H4 lysine 12 lactylation.

Chronic kidney disease (CKD) progression is tightly associated with renal fibrosis, which is regulated by macrophage M2 polarization. The intestinal metabolite trimethylamine N-oxide (TMAO) has been reported to promote CKD, yet its underlying mechanism remains unclear. Here, we elucidated a mechanism wherein TMAO excreted through the kidneys alters the pyruvate metabolism of renal tubular epithelial cells, resulting in the production of lactic acid. Local lactic acid accumulation in the kidney promotes adjacent macrophage M2 polarization, a process speculated to be mediated by specific lactylation of macrophage genes. Through lactylation omics analysis, we identified histone H4 lysine 12 (H4K12) as the most significantly up-regulated lysine residue subjected to lactylation. Subsequent chromatin immunoprecipitation sequencing (ChIP-seq) assays revealed H4K12 lactylation on several glycometabolism gene promoters and genes. Furthermore, we found that this lactylation-mediated epigenetic regulation requires the assistance of the "porter"protein p300, as knockdown of p300 weakened the trend towards M2 polarization induced by lactic acid. Using an in vivo unilateral ureteral obstruction (UUO) mouse model, we verified the M2 polarization effect of TMAO and its detrimental role in CKD, as well as the protective effect of the TMAO inhibitor iodomethylcholine (IMC) on CKD. Clinical data validated the up-regulated TMAO's effect on renal M2 polarization and fibrosis. Our findings suggest that CKD patients exhibit increased TMAO levels, which modulate the production of lactic acid by renal intrinsic cells. Epigenetic regulations mediated by lactic acid, particularly H4K12la on macrophage genes involved in glycometabolism, may contribute to M2 polarization. Targeting TMAO or its downstream pathways could have potential therapeutic benefits in CKD. Schematic diagram showing the whole TMAO modulation process. CKD dysfunction of microbiota leads to elevated TMA. TMA metabolized through liver into TMAO which excreted 90% through kidney. Renal tubular epithelial cells contact with TMAO and secrete lactic acid affecting adjacent macrophages more into M2 type through gene histone H4K12la under the help of p300 as a carrier. These genes include a large amount of glucose metabolism related genes which could at least partially explain this M2 polarization.