Bacillus amyloliquefaciens exopolysaccharide preparation induces glucagon-like peptide 1 secretion through the activation of bitter taste receptors.

The exopolysaccharide preparation of Bacillus amyloliquefaciens amy-1 (EPS) regulates glycemic levels and promotes glucagon-like peptide 1 (GLP-1) secretion in vivo and in vitro. This study aimed to identify the molecular mechanism underlying EPS-induced GLP-1 secretion. HEK293T cells stably expressing human Gα-gustducin were used as a heterologous system for expressing the genes of human bitter taste receptor (T2R) 10, 14, 30, 38 (PAV), 38 (AVI), 43, and 46, which were expressed as recombinant proteins with an N-terminal tag composed of a Lucy peptide and a human somatostatin receptor subtype 3 fragment for membrane targeting and a C-terminal red fluorescent protein for expression monitoring. EPS induced a dose-dependent calcium response from the human NCI-H716 enteroendocrine cell line revealed by fluorescent calcium imaging, but inhibitors of the G protein-coupled receptor pathway suppressed the response. EPS activated heterologously expressed T2R14 and T2R38 (PAV). shRNAs of T2R14 effectively inhibited EPS-induced calcium response and GLP-1 secretion in NCI-H716 cells, suggesting the involvement of T2R14 in these effects. The involvement of T2R38 was not characterized because NCI-H716 cells express T2R38 (AVI). In conclusion, the activation of T2Rs mediates EPS-induced GLP-1 secretion from enteroendocrine cells, and T2R14 is a critical target activated by EPS in these cells.

Exopolysaccharides of Bacillus amyloliquefaciens modulate glycemic level in mice and promote glucose uptake of cells through the activation of Akt.

Bacillus amyloliquefaciens is a probiotic for animals. A strain of B. amyloliquefaciens designated amy-1 was isolated from soil, and the exopolysaccharides (EPSs) of the strain were characterized in terms of their effect on glycemic control. The EPSs were composed of mannose, glucose, and galactose, with the major components being polymers larger than 1000 kDa as revealed by size-exclusion high-performance liquid chromatography. The EPSs reduced the elevation of blood glucose in mice on oral glucose tolerance tests. The hypoglycemic effect was still apparent when glucose was administered through intraperitoneal injection. Further investigation revealed that the EPSs stimulated glucagon-like peptide 1 (GLP-1) secretion from enteroendocrine cells in vitro and increased plasma GLP-1 level in vivo. Moreover, the EPSs promoted the glucose consumption of a liver cell line and an intestinal epithelial cell line. Therefore, the interaction between EPSs and intestinal tissues at least partially contributed to their hypoglycemic effect. The enhanced glucose uptake of cells was likely mediated by the activation of phosphatidylinositol-3-kinase and Akt and was independent of insulin receptor substrate and AMP-activated protein kinase. These findings suggest that EPSs likely involve in the hypoglycemic functions of probiotics and are potential new agents for glycemic control.

Effects of the dietary administration of sodium alginate on the immune responses and disease resistance of Taiwan abalone, Haliotis diversicolor supertexta.

Sodium alginate extracted from brown algae was reported to enhance the immune response and resistance of fish and shrimp. In this study, survival rates of the abalone, Haliotis diversicolor supertexta, against Vibrio parahaemolyticus, and its non-specific immune parameters such as the total haemocyte count (THC), phenoloxidase (PO) activity, respiratory bursts, superoxide dismutase (SOD) activity, phagocytic activity, and clearance efficiency to V. parahaemolyticus by H. diversicolor supertexta were determined when abalone (4.5 ± 0.4 g) were fed diets containing sodium alginate at 0, 1.0, 2.0, and 3.0 g kg⁻¹. Abalone fed a diet containing sodium alginate at 2.0 and 3.0 g kg⁻¹ for 14 days and at 1.0 g kg⁻¹ for 21 days had significantly higher survival rates than those fed the control diet after challenge with V. parahaemolyticus. The relative survival percentages of abalone fed the 1.0, 2.0, and 3.0 g kg⁻¹ sodium alginate-containing diets for 14 and 21 days were 16.1%, 40.0%, and 48.0%, and 63.6%, 27.3% and 22.6%, respectively. The PO activity, respiratory bursts, SOD activity, and phagocytic activity and clearance efficiency of V. parahaemolyticus of abalone fed the sodium alginate-containing diets at 1.0, 2.0, and 3.0 g kg⁻¹ were significantly higher than those of abalone fed the control diet for 14 days. After 21 days, the PO activity, respiratory bursts, SOD activity, and phagocytic activity and clearance efficiency of V. parahaemolyticus by abalone fed the sodium alginate-containing diet at 1.0 g kg⁻¹ were significantly higher than those of abalone fed the other diets. It was concluded that sodium alginate can be used as an immunostimulant for abalone through dietary administration to enhance immune responses of abalone and resistance against V. parahaemolyticus, which were related to the dose and timing of administration.