Physicochemical characterization and hypoglycemic potential of a novel polysaccharide from Polygonatum sibiricum Red through PI3K/Akt mediated signaling pathway

The rhizome of Polygonatum sibiricum is traditionally used as a tonic-type edible herb. In this study, a homogenous polysaccharide (PSPW) was isolated from P. sibiricum. PSPW primarily consisted of fructose and glucose in a molar ratio of 18:1 with a molecular weight of 14.35 kDa. PSPW presented a triple-helical conformation with a rough surface and hill-shaped microstructure. Furthermore, after oral administration of PSPW, the serum levels of fasting blood glucose, glycosylated serum protein and insulin were respectively decreased by 22.5%, 28.4%, and 46.4%, and glucagon-like peptide-1 (GLP-1) secretion showed a 1.7-fold increase in type 2 diabetic (T2D) mice. The glucose tolerance, insulin sensitivity, and hepatic glucose metabolism were improved by PSPW treatment. The elevated PI3K and Akt phosphorylation and reduced FoxO1 and GSK3β phosphorylation were found in liver of PSPW-treated T2D mice, suggesting the potential hypoglycemic mechanism of PSPW may be associated with the activation of insulin-mediated PI3K/AKT signaling pathway.