Early diabetes‐like phenotypes in germ‐free mice induced by gut microbiota from patients with type 2 diabetes

BACKGROUND: The contribution of gut microbiota to the early stage of type 2 diabetes (T2D) remains incompletely understood. This study established a germ-free mouse model colonized with gut microbiota from donors with T2D to determine whether diabetes-associated microbiota could induce early diabetes-like phenotypes. METHODS: Human fecal samples were collected from 18 healthy donors and 14 donors with T2D for microbiota profiling. Based on these features, samples from 12 healthy donors and 3 donors with T2D were selected, pooled within each group, and transplanted into germ-free mice, generating a healthy microbiota recipient group (HM, n = 14) and a diabetes-associated microbiota recipient group (DM, n = 13). Glucose homeostasis was assessed over 10 weeks using fasting blood glucose and intraperitoneal glucose tolerance tests. Gut microbial succession was analyzed by 16S rRNA sequencing. Fecal and plasma metabolomics were performed to identify metabolic and their associations with microbial changes. RESULTS: DM mice developed an early diabetes-like phenotype characterized by progressive impairment of glucose tolerance, reduced insulin levels, and mild renal alterations, without sustained overt fasting hyperglycemia. Microbial divergence emerged before stable metabolic dysfunction and was accompanied by persistent dysbiosis in DM mice. Integrated metabolomic analysis identified coordinated alterations in fecal and plasma metabolites, with cholic acid and L-Dopa decreased in both compartments. L-Dopa showed consistent associations with altered genera, particularly Ruminococcus and Sellimonas. CONCLUSIONS: Transplanting diabetes-associated human gut microbiota effectively induced early glucose dysregulation in germ-free recipient mice. This model provides a framework for studying microbiota-associated events during early T2D-related metabolic deterioration.