Gut microbiota dysbiosis and intestinal barrier impairment in diarrhea caused by cold drink and high-fat diet

Cold drink and high-fat diet (CDHFD) are common diet patterns. However, the potential risks remain unclear. We investigated the effects of CDHFD in adult mice and explored the mechanisms of action. Twenty adult male mice were randomly divided into control and model groups, and the control group was fed a normal diet, whereas the model group was fed CDHFD for 28 days. We found that mice in the model group developed diarrhea symptoms accompanied by fatigue and weakness. Analysis of the intestinal flora revealed that the model group had a lower diversity and richness of microorganism species in the gut than the control group. Furthermore, the characteristic analysis indicated that CDHFD downregulated specific bacteria, such as norank_f_Muribaculaceae, Muribaculum, and Odoribacter, which are known to be associated with the systemic inflammatory response and mucosal barrier function. Blood tests showed that immune cells and inflammatory cytokines were significantly elevated in the model group, along with increased LPS induced by CDHFD. Pathological investigations demonstrated that CDHFD damages the intestinal mucosa while affecting the expression of tight junction proteins, including ZO-1, Claudin-1, Claudin-2, and Occludin, which may be attributed to the activation of the TRAF6/IκB/p65 signaling pathway. In conclusion, impaired gut microbial and mechanical barrier function is responsible for CDHFD-induced diarrhea. In this study, we constructed a model of diet-induced diarrhea by simulating human dietary patterns, evaluated the long-term effects of CDHFD on human intestinal barriers and immune systems, and revealed its mechanism of action based on chronic inflammation. This study validated the model's fit to provide an effective screening model for drug or functional food development.