Hypoglycemic activity and gut microbiota regulation of a novel polysaccharide from Grifola frondosa in type 2 diabetic mice

GFP-N, a novel heteropolysaccharide with a molecular weight of 1.26 x 10(7) Da, was isolated from maitake mushroom and purified by anion -exchange chromatography on a DEAE cellulose-52 column and gel-filtration chromatography on a Sephadex G-100 column. Its structure was characterized by Fourier transform infrared spectroscopy and one-dimensional (H-1- and C-13-) NMR spectra, H-1-H-1 correlation spectroscopy, and H-1-C-13 heteronuclear single-quantum coherence spectroscopy. The structure of GFP-N consisted of L-arabinose, D-mannose and D-glucose and mainly contained three kinds of linkage type units as -> 2,6)-alpha-D-Manp-(1 -> 4, alpha-L-Araf-C1 ->, and -> 3,6)-beta-D-Glcp-(1 ->. GFP-N could activate insulin receptor substrate 1, phosphatidylinositol-3-kinase, and glucose transporter 4 and inhibit c-Jun N-terminal kinase 1/2 for hypoglycemic effects in diabetic mouse livers. This is also the first report of the regulatory efficacy of Grifola frondosa polysaccharide on intestinal microflora in vivo using single-molecule real-time sequencing. These results indicated that polysaccharide from maitake mushroom could be as an enhancer to improve type 2 diabetes and a healthy food option to help regulate gut microbiota in diabetic individuals.