Diet-induced dampness-heat psoriasis is characterized by reduced Lactobacillus and accumulation of deoxycholic acid

Background Psoriasis is a common immune-mediated skin disease influenced by environmental and dietary factors. In traditional Chinese medicine (TCM), endogenous dampness-heat syndrome, often induced by diets rich in stimulating foods, is considered a trigger that aggravates psoriasis. However, the underlying mechanisms remain unclear. This study investigated the gut microbiota and metabolic alterations associated with endogenous dampness-heat syndrome in psoriasis. Materials and methods BALB/c mice were fed a stimulating food diet to establish a model of endogenous dampness-heat syndrome, followed by the induction of psoriasis-like dermatitis by applying imiquimod. Mice on a standard diet served as disease controls and healthy controls. Characteristics of the gut microbiota were analyzed by 16S rDNA sequencing. UPLC–MS/MS was used to detect metabolic changes in the feces and serum of mice and to quantify multiple bile acids. Lipid accumulation and bile acid content in the liver were evaluated by Oil Red O staining and total bile acid assays. Results Endogenous dampness-heat modeling aggravated psoriasis-like symptoms in mice. This was accompanied by marked dysbiosis of the gut microbiota, characterized by reduced abundance of Lactobacillus and Bacteroides . Serum and fecal metabolomics revealed prominent alterations in bile acid metabolism, closely associated with the reduction in Lactobacillus . Targeted quantification confirmed elevated deoxycholic acid in serum, together with increased total bile acids and lipid deposition in the liver. The expression of FXR in bile acid pathway in the liver was decreased, while the expression of CYP7A1 was increased. Conclusion The exacerbation of skin lesions and hepatic lipid deposition in endogenous dampness-heat pattern psoriasis may be associated with bile acid imbalance and reduced Lactobacillus levels.