Green propolis modulates gut microbiota, reduces endotoxemia and expression of TLR4 pathway in mice fed a high-fat diet

Due to the various beneficial effects attributed to propolis, which include anti-inflammatory and anti-bacterial infection properties, the objective of the study was to evaluate the effect of propolis supplementation on the composition of the intestinal microbiota and its anti-inflammatory action. Forty male C57BL/6 mice were fed either a standard diet (control), a high-fat (HF) diet, or a high-fat diet supplemented with 0.2% crude propolis (HFP) for 2 or 5 weeks prior to sacrifice. Blood samples were collected for the determination of lipopolysaccharide (LPS) and classical biochemical parameters. Expression of the TLR4 pathway in muscle, and DNA sequencing for the 16S rRNA of the gut microbiota were performed. The HF diet increased the proportion of the phylum Firmicutes and inflammatory biomarkers, while supplementation with propolis for five weeks rendered the microbiota profile nearly normal. Consistently with the above, the supplementation reduced levels of circulating LPS and down-regulated the TLR4 pathway and inflammatory cytokine expressions in muscle. Moreover, propolis improved such biochemical parameters as serum triacylglycerols and glucose levels. The data suggest that propolis supplementation reduces inflammatory response and endotoxemia by preventing dysbiosis in mice challenged with a high-fat diet.