Preparation of hypoglycemic peptides from oysters fermented with Bacillus subtilis: characterization, molecular docking, and in vivo evaluation.

Type 2 diabetes mellitus (T2DM), a highly prevalent chronic metabolic disorder, is primarily defined by persistent hyperglycemia due to defects in insulin secretion or action. In this study, a hypoglycemic peptide-containing fraction was prepared from oysters via liquid fermentation using Bacillus subtilis (CGMCC no. 28507). Following optimization of fermentation conditions and ultrafiltration separation, a fraction (FOP) with a molecular weight below 3 kDa was obtained, demonstrating the highest inhibitory potency against α-glucosidase. In vivo experiments using mice with T2DM confirmed that FOP markedly reduced fasting blood glucose, glycated haemoglobin levels, and insulin resistance and simultaneously improved glucose tolerance and lipid metabolism profiles, downregulating pro-inflammatory cytokines and alleviating pathological damage to the liver and pancreas. Following gel chromatography purification, three bioactive peptides (KSYFPT, VGGQGFF, and LRFPGQ) were identified by LC-MS/MS. According to molecular docking experiments, these peptides exhibited stable binding interactions with the α-glucosidase active site. All synthesized peptides exhibited significant inhibitory activity. This study delineates an eco-friendly protocol for the sustainable valorization of oyster proteins, simultaneously providing a theoretical basis for the formulation of food-derived functional agents with significant hypoglycemic potential.