ObjectiveTo investigate the effects of Erchentang （ECD） on the body weight of the mouse model of simple obesity induced by a high-fat diet （HFD） and decipher the underlying mechanisms. MethodsFirstly， single-cell transcriptomics （Sc-RNAseq） was employed to analyze the transcriptional changes in the ileum tissue of mice in the normal group and model group. Then， a mouse model of simple obesity was established with a high-fat diet. The successfully modeled mice were randomly allocated into the following four groups （n=8）： model， low-dose （7.5 g·kg^-1） ECD， medium-dose （15 g·kg^-1） ECD， and high-dose （30 g·kg^-1） ECD. Additionally， 8 mice of the same age were selected as the normal group. The body weight was measured at fixed time points during the 4-week gavage period. The overall efficacy of ECD in alleviating obesity was evaluated through glucose tolerance testing， behavioral analysis， hematoxylin-eosin （HE） staining， and biochemical testing. Protein docking was employed to predict the degree of binding between corresponding proteins. Molecular docking was employed to predict the binding degree between key components of ECD and target proteins. Real-time PCR was employed to determine the mRNA levels of tumor necrosis factor-α （TNF-α）， inducible nitric oxide synthase （iNOS）， interleukin-1β （IL-1β）， CD68， CD206， zonula occludens-1 （ZO-1）， and Claudin-5 in the ileum. Immunofluorescence staining was used to observe the expression and distribution of Claudin-5 and ZO-1. ResultsThe Sc-RNAseq results indicated that the differentially expressed genes of immune cells in the model group in comparison with the normal group were primarily enriched in biological functions related to lipid metabolism and inflammatory metabolism. Additionally， these genes were associated with the janus kinases（JAK）/signal transducers and activators of transcription （STAT） signaling pathway， an inflammation-related pathway. Compared with the normal group， the model group showed increases in body weight （P<0.01） and blood glucose level （P<0.01）， a decrease in limb strength （P<0.01）， an increase in liver weight （P<0.05）， and elevated serum alanine amino-transferase （ALT） and aspartate transferase （AST） levels （P<0.05， P<0.01）. Additionally， the model group exhibited increased hepatic fat vacuoles， notably enlarged adipocytes in the epididymal and inguinal white adipose tissue， and increased inflammation. Compared with the model group， ECD groups showed reduced body weights （P<0.01） and blood glucose levels （P<0.01）， increased limb strength （P<0.05， P<0.01）， decreased liver weights （P<0.05， P<0.01）， and declined serum ALT and AST levels （P<0.05， P<0.01）. Additionally， ECD reduced hepatic fat vacuoles and the adipocyte volume in the epididymal and inguinal white adipose tissue， and alleviated inflammation. Potential interactions existed between CD68 and ZO-1/Claudin-5， as well as between CD206 and ZO-1/Claudin-5. The key components of ECD， nobiletin， diosmetin， and naringenin， all demonstrated strong binding affinity with the target proteins ZO-1 and Claudin-5. Compared with the normal group， the model group exhibited up-regulated mRNA levels of the pro-inflammatory cytokines TNF-α， iNOS， IL-1β， and CD68 （P<0.05， P<0.01） and down-regulated mRNA levels of the anti-inflammatory cytokine CD206 （P<0.01） and the tight junction proteins Claudin-5 and ZO-1 （P<0.05， P<0.01）. In comparison with the model group， the ECD groups showed down-regulated mRNA levels of TNF-α， iNOS， IL-1β， and CD68 （P<0.05， P<0.01） and up-regulated mRNA levels of CD206， Claudin-5， and ZO-1 （P<0.05， P<0.01）. Compared with the normal group， the model group exhibited down-regulated expression of tight junction proteins Claudin-5 and ZO-1 （P<0.01）. Compared with the model group， ECD groups showed up-regulated expression of Claudin-5 and ZO-1 （P<0.05， P<0.01）. ConclusionECD can significantly ameliorate HFD-induced obesity and excessive body weight gain in mice by improving the inflammatory microenvironment in the ileum and further restoring the integrity of the impaired ileal barrier.