Hypoglycemic Effect of Ganoderma lucidum Purified Polysaccharide F31 Targeted Glucose-6-Phosphatase-Catalytic Protein in Type 2 Diabetic Mice

摘要

Previous studies have demonstrated that Ganoderma lucidum polysaccharides (GLPs) have hypoglycemic effects in type 2 diabetic mice.This study aimed to investigate the hypoglycemic effects and mechanisms of action of Ganoderma lucidum purified polysaccharides-enriched fraction from GLPs in type 2 diabetic mice.GLPs were applied onto a column of deaerator (DEAE) Sepharose Fast Flow chromatography,then onto gel filtration-Sephacryl S300.Four purified polysaccharide fractions named F21,F22,F31 and F32 were obtained.The mice were randomLy divided into 6 groups (8 mice/group).The 6 groups were as follows:normal control group,diabetic control group,F21-treated diabetic group [50 milligrams/kilograms/day (mg/kg/d)],F22-treated diabetic group (50 mg/kg/d),F31-treated diabetic group (50 mg/kg/d) and F32-treated diabetic group (50 mg/kg/d).Diabetes was induced via streptozotocin (STZ) injection and high-fat dietary feeding.In seven days following the STZ injection,fasting serum glucose and insulin levels were measured.The hepatic messenger ribonucleic acid (mRNA) levels of glycogen phosphorylase (GP),fructose-l,6-bisphosphatase (FBPase),phosphoenolpyruvate carboxykinase (PEPCK),glucose-6-phosphatase (G6Pase,including G6Pase-catalytic protein and a specific transporter named G6Pase-T1) were determined by real-time polymerase chain reaction (RT-PCR).Results showed that F31 significantly decreased fasting serum glucose compared with the diabetic control group (p＜0.05),and simultaneously decreased the hepatic mRNA levels of GP,FBPase,PEPCK and G6Pase (p＜0.01).In contrast to F21,F22,and F32,only F31 significantly decreased mRNA levels of G6Pase-catalytic protein.Taken together,the decreases in fasting serum glucose levels may be associated with decreased mRNA levels of G6Pase-catalytic protein,indicating that G6Pase-catalytic protein may be the key factor of glucose regulatory enzymes due to hypoglycemic effect.The structural characteristics of F31 were investigated by gel permeation chromatography (GPC),Fourier transform infrared (FTIR),nuclear magnetic resonance (NMR) and gas chromatography mass spectrometry (GC-MS).Based on the data obtained,F31 was determined to be a β-heteropolysaccharide composed of glucose,mannose,xylose,arabinose and galactose with the kilo Dalton molecular weight (kDa) of 15.9.