Protocatechuic acid alleviates TMAO-aggravated atherosclerosis via mitigating inflammation, regulating lipid metabolism, and reshaping gut microbiota

Trimethylamine-N-oxide (TMAO) is a risk factor for atherosclerosis. As a natural phenolic acid, protocatechuic acid (PCA) is abundant in various plant foods. The present study was to investigate the effect of PCA on TMAO-aggravated atherosclerosis in ApoE-/- mice. The mice were randomly divided into five groups and fed one of the following five diets for 12 weeks: namely a low-fat diet (LFD), a western diet (WD), a WD+0.2% TMAO diet (WDT), a WDT+0.5% PCA diet (WDT+LPCA), and a WDT+1.0% PCA diet (WDT+HPCA). Results demonstrated that dietary TMAO exacerbated the development of atherosclerosis by eliciting inflammation and disturbing lipid metabolism. PCA at 1% diet reduced TMAO-induced aortic plaque by 30% and decreased the levels of plasma proinflammatory cytokines. PCA also improved the lipid metabolism by up-regulating hepatic gene expression of peroxisome proliferator-activated receptor alpha (PPARα). In addition, PCA supplementation enhanced fecal excretion of fatty acids and decreased hepatic fat accumulation. PCA supplementation favorably modulated gut microbiota by increasing α-diversity with an increase in the abundance of beneficial genera (Rikenella, Turicibacter, Clostridium_sensu_stricto and Bifidobacterium) and a decrease in the abundance of adverse Helicobacter genus. In summary, PCA could alleviate the TMAO-exacerbated atherosclerosis and inflammation, improve the lipid metabolism, and modulate gut microbiota.