Effects of Litchi on Systemic Low-Grade Inflammation and the Structure and Function of Gut Microbiota in HFA Mice

Abstract

Background: Certain foods are known as “heating” foods in Chinese medicine as over consumption of them can lead to symptoms known as “heating up”, which have been shown to be symptoms of systemic low-grade inflammation. However, the mechanism by which these foods cause inflammation is not clear. In this study, we investigated dysbacteriosis of gut microbiota as a possible cause of inflammation by litchi, a typical “heating” food. Human flora-associated (HFA) mice model was constructed by first sterilizing their guts by oral administration of antibiotics, and then transplantation of fecal microbial suspension from a healthy human adult. After gavaging the mice with litchi powder suspension at low, medium and high doses (400, 800, 1600 mg/kg·d-1 respectively) for 7 days, the serum level of inflammatory cytokines, gut microbiota and the integrity of intestinal mucosal barrier were measured.Result: The intervention of litchi significantly increased the diversity of mice gut flora. The ratio of Bacteroidetes/Firmicutes and the abundance of Actinobacteria increased significantly. At the genus level, the abundance of Phascolarctobacterium, Akkermansia, Megasomonas and Lactobacillus generally decreased, while the abundance of Prevotella and Bacteroides increased significantly, especially in the high litchi dose group. The abundance of Bilophila increased significantly only in high dose group. litchi intervention caused serum TNF-α level to increase by more than two times and LPS level to double, but a decrease in IL-1β and IL-6 levels. Medium and high dose litchi intervention caused a widening of intestinal epithelial cell junction complex, and general weakening of the intestinal mucosal barrier as well as reduced efficiency of gut microbiota in energy conversion. Conclusion: This study confirmed the notion in Chinese medicine that as a “heating” food, litchi when consumed excessively can lead to low degree systematic inflammation and demonstrated that this is linked to its ability to cause dysbacteriosis of the gut microbiota and weakening of the intestinal mucosal tissues.