Preparation Of Burdock Polysaccharide And Its Regulation Effect On Glycolipid Metabolism In NAFLD Model Cells

Arctium lappa L.,also known as Burdock,is a biennial herb of the genus Arctium in the family Asteraceae.It is cold,bitter and non-toxic,and both the achene and the root are used as medicine.The nutritional value,bioactivity and health benefits of burdock have been internationally recognised over the last few decades,but less specific research has been carried out on its glycolipid metabolism and no effective components have been identified to improve it.In this thesis,a high sugar and high fat diet was used to induce an obesity model in Sprague-Dawley(SD)rats,and Arctium lappa L.root powder(ARP)was found to be effective in suppressing intestinal inflammation in obese rats,and had a weight loss and lipid-lowering effect on obese rats.The polysaccharide was purified by Cellulose DEAE-52 cellulose anion exchange column and SephacrylTM S-400 dextran gel column,and then freeze-dried to obtain Arctium lappa L.polysaccharide(ALP).The purity and structural characterization of ALP were carried out using various spectroscopic and chromatographic methods;finally,a model of non-alcoholic fatty liver was constructed using oleic acid-induced HepG2 cells to explore the biological activity of ALP at the cellular and molecular levels.The main findings of this thesis are as follows:(1)A high-sugar and high-fat diet induced Sprague-Dawley(SD)rats to construct an obesity model,and the data showed that a high-sugar and high-fat diet induced the production of pro-inflammatory and inflammatory factors in intestinal tissues,and Arctium lappa L.root powder(ARP)inhibited the excess of pro-inflammatory and inflammatory factors in colon tissues of obese rats,including interleukin-1β(IL-1β),interleukin-8(IL-8),interleukin-6(IL-6),tumor necrosis factor-α(TNF-α),monocyte chemotactic protein-1(MCP-1),intercellular adhesion molecule-1(ICAM-1)and vascular cell adhesion molecule-1(VCAM-1).In addition,ARP downregulated key genes of the Toll-like receptor 4(TLR4)complex,namely TLR4,myeloid differentiation protein-2(MD2)and myeloid differentiation factor-88(Myd88),as well as downstream signals,such as tumor necrosis factor receptor associated factor 6(TRAF6)and nuclear factor-κB(NF-κB).At the same time,ARP regulates immunity and inflammation through the TLR4/NF-κB signalling pathway,inhibits the release of pro-inflammatory and inflammatory factors and effectively suppresses intestinal inflammation in obese rats;(2)Arctium lappa L.crude polysaccharide(ALCP)was extracted from burdock root powder,with a total sugar content of(80.99±0.04)%,protein content of(12.32±0.48)%,fat content of(0.50±0.06)%,and moisture content of(5.29± 0.52)%,as well as total phenol content(TPC)of(765.13 ± 0.70)mg gallic acid equivalent(GAE)/100 g dry weight(DW).The ALCP was purified by Cellulose DE-52 fibre resin and SephacrylTM S-400 dextran gel resin.The obtained refined polysaccharide ALP was a neutral polysaccharide with a purity of 99%.The UV spectrophotometer showed that ALP did not contain nucleic acid and protein.The relative heavy average molecular weight(Mw)of ALP was 4256 Da,the peak molecular weight(Mp)was 4001 Da,the number average molecular weight(Mn)was 3437 Da,and the Mw/Mn was 1.24,which indicated that the homogeneity of ALP was good.The in vitro pancreatic lipase inhibition rate IC50 of ALP was 8.18 mg/mL,while the inhibition rate of ALCP was 45.44%at 10 mg/mL.(3)Oleic acid induced human hepatoma cells HepG2 to construct an in vitro model of nonalcoholic fatty liver disease(NAFLD)and the effect of burdock polysaccharides on NAFLD in vitro model cells was investigated.It was found that both ALP and ALCP could reduce triglycerides and liver sensitivity indexes,aspartate transaminase(AST)and alanine transaminase(ALT),in NAFLD model cells,TLR4 and its downstream signaling pathway NF-κB,phosphatidylinositol-3-kinase(PI3K)-protein kinase-B(Akt)to activate adenosine 5’-monophosphate-activated protein kinase(AMPK)signaling pathway,thereby upregulating the glycolipid metabolism-related factors PI3K,Akt,acetyl CoA carboxylase(ACC),AMPK,carnitine palmitoyltransferase-1(CPT-1),and downregulating forkhead box O1(FoxO1),glucose-6-phosphatase(G6Pase)factor.In addition,the effect of ALP in regulating glycolipid metabolism was more significant than that of ALCP,which may be related to the higher purity of ALP,suggesting that there is indeed a close correlation between the purity and structure of the polysaccharide and its activity.The experimental results obtained from in vitro cellular experiments with burdock polysaccharides were similar to those obtained from burdock root powder in animals,suggesting that the polysaccharides in burdock roots are the main components that play a role in improving glucolipid metabolism.The above series of studies revealed that the components of burdock root powder that plays a role in regulating glycolipid metabolism may be burdock polysaccharides,which is of great significance for the development and application of burdock resources.This study provides a scientific basis for the development of functional foods from burdock roots for the prevention and treatment of obesity and other metabolic syndromes and for improving the intestinal health of patients,and provides new ideas for the development of burdock nutritional meal replacement powder,fermented tea,essence drink,chewable tablets,jelly drink,enzyme shake and other products of burdocks to lower sugar and fat.