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

Abstract

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.