Microbiome and metabonomics study of quercetin for the treatment of atherosclerosis

The molecular mechanism of quercetin in the prevention and treatment of AS has been widely reported. However, the microbial and metabolic characteristics of quercetin in AS treatment are still poorly understood. In this study, we aimed to explore the gut microbial and metabolic signatures of quercetin in AS treatment and conduct an integrative analysis on its biomechanism.

An atherosclerosis mouse model was induced by a high cholesterol diet (HCD). The duration of the quercetin treatment was 12 weeks. We measured TC, TG, HDL and LDL for plasma biochemical analysis and TNF-α and IL-6 for plasma inflammatory analysis. Haematoxylin-eosin (HE) staining was conducted to evaluate the aortic structure and atherosclerosis. Bacterial DNA, which was extracted from mouse faeces, was identified by the V3-V4 regions of the 16S rRNA for microbiological analysis. The HeatMap package of BTtools was applied to visualize the data of the microbial difference matrix according to the OTU results. Fecal metabolites were assessed through LC-MS. Multivariate data analysis was conducted on the normalized data with SIMCA-P+. Significantly different metabolites were extracted based on the Pearson correlation coefficients at the level of P<0.05. Key significantly changed metabolites were screened from the intersection between metabolic signatures of the normal-model and model-quercetin groups. To investigate the biological function of quercetin on AS, we identified the differential metabolic signatures of the model vs. quercetin groups and performed KEGG analyses via MBROLE, MetaboAnalyst database.

Quercetin treatment for 12 weeks significantly reduced the levels of TC (P<0.001), TG (P<0.05), HDL (P<0.001), LDL (P<0.001), TNF-α (P<0.001) and IL-6 (P<0.001) compared with the model group. HE staining indicated that quercetin could protect damaged vessels caused by HFD. Bacteroidetes, Firmicutes and Proteobacteria were dominant microbial groups in the samples. There was no significant difference between the three groups (P>0.05) at the phylum level, and the genera Phascolarctobacterium and Anaerovibrio can be regarded as the key microbiota signatures of quercetin treatment. PLS-DA results further showed that these 18 faecal metabolites (clustered in 3 groups) had significant differences between the control, model and quercetin groups throughout the 12-day treatment. According to the quantitative analysis results, 32 key metabolic signatures were screened for quercetin treatment. The main pathway in quercetin treatment is primary bile acid biosynthesis, as 3α,7α,12α,26-tetrahydroxy-5β-cholestane (C27H48O4) was defined as the most important key metabolic signature.

We explored the gut microbial and metabolic involvement of quercetin in AS treatment and suggest the association between AS and gut metabolic regulation.