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Structure and in vitro hypoglycemic activity of a homogenous polysaccharide purified from Sargassum pallidum

Cao, Changliang, Zhang, Bin, Li, Chao, Huang, Qiang, Fu, Xiong, Liu, Rui Hai
Food & function 2019 v.10 no.5 pp. 2828-2838
Sargassum, arabinose, fucose, galactose, galacturonic acid, glucose, glucose transporters, glucuronic acid, glycemic effect, glycogen, glycogen (starch) synthase, hexokinase, human cell lines, insulin receptor substrate proteins, insulin resistance, mannose, molecular weight, phosphatidylinositol 3-kinase, pyruvate kinase, xylose
This study aimed at investigating the structure, hypoglycemic activity and the underlying mechanism of a homogeneous polysaccharide (PSP-2) purified from Sargassum pallidum. Structural characterization revealed that PSP-2 with a molecular weight of 144.8 kDa was composed of fucose (21.6%), arabinose (2.5%), galactose (22.4%), glucose (2.2%), xylose (18.8%), mannose (1.2%), glucuronic acid (7.7%) and galacturonic acid (23.6%). The backbone chain of PSP-2 was composed of →1)-β-d-Xylp-(3→, →1,3)-β-l-Fucp-(4→, →1)-α-d-Galp-(6→, and →1)-α-d-GlcpNAc-(2→, and the side chains were composed of →1,3,6)-α-d-Galp-(2→, →3)-β-l-Fucp-(1,4→, β-d-GalpNAc-(1→, and α-d-Manp-(1→. In vitro hypoglycemic assays indicated that PSP-2 could significantly enhance glucose consumption, glycogen synthesis, and pyruvate kinase (PK) and hexokinase (HK) activities of insulin-resistant HepG2 cells. Furthermore, the underlying mechanistic studies revealed that PSP-2 could ameliorate insulin resistance by up-regulating the expression levels of insulin receptor substrate-1 (IRS-1), glycogen synthase (GS), phosphoinositide-3-kinase (PI3K) and glucose transporter-4 (GLUT4). These results suggested that PSP-2 may be a potential candidate for the prevention and treatment of Type 2 diabetes mellitus.