Isolation And Hypoglycemic Mechanism Effect Of Polysacchaide From Brasenia Schreberi

Brasenia schreberi is a rare and precious vegetable,which is coated with a gelatinous mucilage with unique texture.This study is aiming to investigate the effect of ultrafiltration on the hypoglycemic activities of polysaccharide.(1)Alkaline extraction of polysaccharide(BSP-NaOH)from Brasenia schreberi mucilage was used as raw material.BSP-U100,BSP-U50 and BSP-U10 were obtained by ultrafiltration from BSP-NaOH.The structural characteristics of different samples were compared by scanning electron microscopy,Congo red test and Circular dichroism(CD).BSP-U100 had a triple helix structure and existed as the ordered structure in aqueous solution.BSP-U100 exhibited high α-amylase(IC50=0.4414 mg/mL)and α-glucosidase(IC50=0.5993 mg/mL)inhibitory activity compared to the polysaccharides without ultrafiltration.(2)STZ induced diabetic C57BL/6 mice were used to examine the auxiliary hypoglycemic function of Brasenia schreberi polysaccharide.After 4 weeks of gavage administration,the results showed that BSP-NaOH and BSP-U100 can improve the condition of weight loss,polydipsia and polyphagy caused by diabetes.The blood glucose levels can be effectively controlled.BSP-NaOH and BSP-U100 can effectively reduce serum insulin(INS)levels,serum glucagon(GC)levels and serum epinephrine(E)levels,and also reduces serum total cholesterol(TC),triglyceride(TG)levels and High-density lipoprotein cholesterol(HDL-C)levels,with auxiliary hypolipidemic effect,the contents of glycogen increased 1.43mg/g and 0.60mg/g,the contents of myoglycogen increased 1.03mg/g and 0.86mg/g.By Q-PCR analysis indicated that the up-regulated IRS1-PI3K-Akt phosphorylation followed by the down-regulated GSK-3β phosphorylation contributed to the enhanced glycogen synthesis and the decreased gluconeogenesis by BSP-NaOH and BSP-U100.Thus,it is shown that BSP-NaOH and BSP-U100 can promote insulin PI3K-Akt signaling pathway,and develop type 2 diabetes.(3)BSP-Peptide was obtained using EDC/NHS method by crosslinking the BSP-NaOH and walnut peptide.The corresponding modification groups that appeared in theinfrared images of BSP-Peptide,indicated the crosslink was successful.Compared with the BSP-NaOH group,the α-amylase and α-glucosidase inhibition rate of BSP-Peptide was higher(with IC50=0.4414 mg/mL and IC50=0.5993 mg/mL,respectively).HepG2 cells were used as a receptor model to study the effects of polysaccharides on glucose consumption in insulin resistance hepatic cells.Compared with the control,both BSP-NaOH,BSP-U100 and BSP-Peptide could increase the glucose consumption of insulin-resistant HepG2 cells within the range of safe administration(0.5-2 mg/mL).Among them,the highest glucose consumption was obtained,when BSP-NaOH was at a concentration of 1.0 mg/mL,BSP-U100 was at a concentration of 1.5 mg/mL and BSP-Peptide was at a concentration of 2.0 mg/mL,the effect of BSP-Peptide(2.94 mmol/L)was better than the experimental insulin group(1.881 mmol/L)and metformin group(2.752 mmol/L).Compared with the normal control group,the glucoseconsumption of the model group(IR)induced by high insulin was significantly reduced,indicating that the insulin resistance model was successfully established.This study provided a useful theoretical basis for the development and application of Brasenia schreberi polysaccharides as one of the potential anti-diabetic supplement.