The Fucoidan From Seaweed Ascophyllum Nodosum Alleviates The Formation Of Atherosclerotic Plaques In Apolipoprotein E-deficient Mice By Lipid Lowering

Cardiovascular and cerebrovascular disease(CCVD)is the main cause of death worldwide,and its basic pathological change is atherosclerosis(AS).Hyperlipidemia plays a key role in the progression of AS.However,a long-term use of synthesized lipid-lowering drugs can induce various side effects.Therefore,researchers are impelled to explore natural compounds with lipid-lowering activity and low toxicity.Recently,fucoidans with low toxicity are reported to have hypolipidemic effects.However,the underlying mechanisms are still far from clear.This study was designed to investigate the hypolipidemic and anti-atherosclerotic effects and especially the underlying mechanisms of action of the fucoidan from seaweed Ascophyllum nodosum.In this study,the crude polysaccharides of A.nodosum were isolated and purified by an AKTA pure 150 fast protein liquid chromatography system combined with Q-SepharoseTM Fast Flow anion exchange column and Sephacryl S-200HR size-exclusion chromatography columns.Our results demonstrated that the fucoidan An1 obtained from A.nodosum displayed one major peak on a GPC column.Its weight-average molecular weight(Mw),number-average molecular weight(Mn)and z-average molecular weight(Mz)were 361.4 kDa,69.5 kDa,and 872.3 kDa,respectively.The carbohydrate content,sulphate content,and protein content of the fucoidan were 68.0%,16.6%and 2.8%,respectively.The fucoidan An1 was composed of mannose,glucose,galactose,xylose,and fucose in a molar ratio of 2.3:1.5:1.0:6.9:22.4 as measured by HPLC.Based on our results,fucose accounted for～65.6%of this fucoidan.In this study,apolipoprotein(apo)E-deficient(apoE(-/-)mice(10-11 weeks old)was chosen as the atherosclerosis model.After acclimatization for 1 week,the mice were randomly divided into four groups,namely,the model group(n=5,0.9%sodium chloride by gavage),the fenofibrate group(n=5,50 mg·kg-1·d-1 by gavage),the low-dose fucoidan group(Anl-L,n=5,50 mg·kg-1·d-1 by gavage)and the high-dose fucoidan group(An1-H,n=5,200 mg·kg-1·d-1 by gavage).The apoE(-/-)mice had free access to the high-fat diet(21%fat and 0.15%cholesterol).and water during the 8-week experimental period.After the last administration,the mice was fasted for 12 hours.Blood,heart,liver,and small intestine were collected and stored in a refrigerator at-80℃.The bottom sections of the heart were stained with Oil red O to detect the changes of atherosclerotic plaque.The liver,kidney and small intestine were stained with hematoxylin-eosin staining(H&E)to detect their pathological changes.Plasma levels of total cholesterol(TC)and triglyceride(TG)were measured by TC and TG kits.Reverse transcription-polymerase chain reaction(RT-PCR)and Western blot were used to analyze the expression of Anl genes and proteins related to reverse cholesterol transport(RCT)in the liver and small intestine.Our results demonstrated that the fucoidan administration ameliorated atherosclerotic lesion and lipid profiles in a dose-dependent manner in the apoE(-/-)mice fed with a high-fat diet.Oil red O staining results revealed that the lesion/lumen ratio reduced by 29.9%and 46.9%in the An-L and An-H treated apoE(-/-)mice compared to the model group,respectively.Furthermore,the lipid deposition in the liver decreased by 35.5%and 59.3%in the An-L and An-H group compared to the model group,respectively.Fucoidan intervention significantly decreased the plasma alanine aminotransferase(ALT)and aspertate aminotransferase(AST)levels in a dose-dependent manner compared to the model group,which suggested that this fucoidan reduced the high-fat diet-induced toxicity to some extent in the apoE(-/-)mice.However,Anl-H displayed minor toxicity to the small intestine.In plasma,Anl decreased the levels of TG and TC and increased the protein expression of LPL in apoE(-/-)mice.In the mice liver,the fucoidan treatment significantly increased the protein expression of scavenger receptor B type 1(SR-B1),peroxisome proliferator-activated receptor(PPAR)α and β,liver X receptor(LXR)α,ATP-binding cassette transporter(ABC)A1 and ABCG8,and decreased the protein expression of PPARy and sterol regulatory element-binding protein(SREBP)1c.The protein expression of low-density lipoprotein receptor(LDLR)and proprotein convertase subtilisin/Kexin type 9(PCSK9)was not affected.In the small intestine of the apoE(-/-)mice,the fucoidan treatment significantly reduced the protein expression of niemann-pick C1-like 1(NPC1L1)and dramatically improved ABCG8 levels.These results demonstrated for the first time that the fucoidan from A.nodosum attenuated AS by regulating RCT-related genes and proteins expression in apoE(-/-)mice.In summary,this fucoidan from A.nodosum may be explored as a potential compound for prevention or treatment of hyperlipidemia-induced AS.