Effects of Bifidobacterium breve B-3 on Glycemic Control and Glucose-Regulatory Responses in db/db Mice

Type 2 diabetes mellitus is characterized by chronic hyperglycemia and impaired glucose homeostasis. This study evaluated the anti-diabetic effects of Bifidobacterium breve B-3 using in vitro models and db/db mice. B. breve B-3 inhibited α-amylase activity and enhanced insulin-stimulated glucose uptake in palmitic acid-induced insulin-resistant C2C12 myotubes. Metabolite profiling also showed distinct strain-associated metabolic characteristics of B. breve B-3. In db/db mice, oral administration of B. breve B-3 significantly reduced fasting blood glucose levels and improved oral glucose tolerance without affecting body weight. These effects were accompanied by changes in incretin-related endocrine responses, including increased serum GLP-1 levels and decreased DPP-4 activity. B. breve B-3 also increased serum insulin and C-peptide levels and partially preserved pancreatic insulin immunoreactivity. In addition, mild diabetes-associated intestinal morphological alterations and glucose-regulatory marker expression were partially normalized after administration. In skeletal muscle, B. breve B-3 was associated with increased expression of glucose uptake- and metabolic signaling-related markers, including AKT/GLUT4 and ADIPOR1/AMPK pathways. Overall, these findings suggest that B. breve B-3 improves glycemic control in db/db mice in association with changes in incretin-related endocrine responses and glucose-regulatory signaling markers.