Soy yoghurts produced with efficient GABA (γ-aminobutyric acid)-producing ameliorate hyperglycaemia and re-establish gut microbiota in streptozotocin (STZ)-induced diabetic mice.

Soy yogurt has been gaining popularity as a vegan food produced simply by soymilk fermentation with proper microbial manipulation. It is well known that soy containing rich isoflavones is beneficial for ameliorating hyperglycaemic disorders. Soy fermentation can improve the bioavailability of these precious nutrients. is one of the most abundant and frequently isolated species in soymilk manufacturing. Soy yogurts produced with efficient GABA (γ-aminobutyric acid)-producing and the deglycosylating activity of were functionally assessed in a STZ-induced hyperglycaemic mouse model. Hyperglycaemic mice were assigned into groups and treated with daily gavage of either dHO, soymilk, soy yoghurts produced with high GABA-producing (LPGA30), low GABA-producing (LPPV30) or the soy yoghurts fortified with additional 30 mg g GABA counterparts (GA + GABA and PV + GABA groups). Except the dHO group, all soy yoghurt groups retained body weight with improved glucose homeostasis, glucose tolerance test results and renal tissue integrity, while the soymilk group shows partial benefits. Plasma GABA concentrations in the daily soy yoghurt-supplemented groups (LPGA30 and LPPV30) plateaued at 5 times higher than the average 0.5 μM in dHO and soymilk groups, and their GABA-fortified soy yoghurt counterparts (GA + GABA and PV + GABA) groups were accountable for the restored plasma insulin levels. Gut microbiome analysis revealed dysbiosis in STZ-induced hyperglycemic mice of the dHO group with breached out facultative anaerobic Proteobacteria over the normal phyla Firmicutes and Bacteroidetes. Restored gut microbiota with transitionally populated Actinobacteria was demonstrated in the LPGA30 group but not in the LPPV30 group. Soy yoghurts produced with efficient GABA-producing showed exceptional benefits in modulating gut microbiota with dominant genera of , and , and the presence of some minor beneficial microbial communities including , , spp. and spp. Efficient GABA-producing fermented soymilk to produce soy yoghurts that exhibit profound synergistic protections over rich soy isoflavones to restore pancreatic β-cell functions for insulin production in STZ-induced hyperglycaemic mice. Additionally, the probiotic role of GABA-producing in re-establishing healthy gut microbiota in hyperglycaemic mice implies a possible symbiotic relationship, awaiting further exploration.