Study On The Mechanism Of Low Molecular Weight Fucoidan From Saccharina Japonica On Diabetic Nephropathy

Diabetic nephropathy(DN),which occurred as the earliest diabetic complication,is one of diabetic microvascular diseases,and it is also the main reason for dialysis for chronic renal failure and end-stage renal disease.DN is a metabolic disorder complication caused by persistent hyperglycemia in diabetes mellitus,and it was closely related to various pathological processes.With the application of low molecular weight fucoidan(LMWF)extracted from Saccharina japonica,which consisted of fucose,sulfate,galactose,etc.,it was verified that LMWF exhibited various biological activities,such as anticoagulation,anti-inflammation,anti-oxidation,anti-tumor,etc.Moreover,polysaccharides and polysaccharide complexes play an important role in the occurrence and development of DN.As one of natural brown seaweed polysaccharides,LMWF could intervene the key polysaccharide complexes and other cytokines in the process of DN,nevertheless the mechanism was not been illustrated yet.Here,we aimed to explore the mechanism of LMWF in improving DN.Through the establishment of cell model with advanced glycation endproducts(AGEs),we verified that LMWF could significantly improve abnormal HRMC proliferation and hypertrophy caused by AGEs.It was proved that the LMWF could reduce the endotoxin content and lactate dehydrogenase(LDH)activity in cell culture medium.Quantitative proteomics KEGG enrichment analysis indicated that LMWF was mostly related to extracellular matrix(ECM)-receptor interaction pathway.In the ECM-receptor interaction,fibronectin(FN)protein expression was significantly influenced by LMWF.Cell immunofluorescence and surface plasmon resonance(SPR)detection reflected the co-localization and the specific binding of LMWF and FN,with an equilibrium dissociation constant K_Dof 453.7?mol/L.Moreover,we found that positively charged protamine sulfate(PS)can promote LMWF binding to HRMCs and enhance the therapeutic effect of LMWF on HRMC injury.Through the establishment of early DN rat model induced by STZ,we verified that LMWF could obviously alleviate the over drink,hyperphagia and emaciation compared with microcrystalline cellulose(MC).LMWF exhibited less effects on serum biochemical indexes and did not significantly improve the hyperglycemia of DN rats.LMWF could obviously improve DN early symptoms including urorrhagia,excessive urinary protein excretion ratio,high ACR,etc.It inhibited glomerular basement membrane lesions,prevented the thickening of glomerular mesangial and basement membrane,and alleviated glomerular structure lesions.LMWF decreased the protein expression of FN,muscle protein malnutrition chitosan(DG),laminin(LAMC1),interleukin 6(IL-6),intercellular adhesion molecule-1(ICAM1),and other proinflammatory factors.Nevetheless,the effects was greatly reduced when it was combined with antibiotics(Anti).We deduced that LMWF could improve kidney dysfunction in DN rats and reduce kidney tissue lesions caused by inflammation,which was related to gut microbiota.LMWF could significantly inhibit the intestinal dysfunction of DN rats,including reducing intestinal permeability and fecal weight,and increasing the length of colon.16S r DNA sequence analysis of DN rat faeces indicated that LMWF relieved the gut microbiota disorder,increased the abundance of Bacteroidetes and reduced the abundance of Firmicutes.Additionally,LMWF significantly increased the abundance of Bacteroidales S24-7 group,Ruminococcaceae,and other species which could yield short chain fatty acids(SCFAs).Therefore,LMWF could regulate the gut micobiota in DN rats.In summary,LMWF could effectively inhibited kidney damage,alleviating the abnormal HRMC proliferation and hypertrophy which caused by AGEs via binding FN and inhibiting ECM-receptor interaction in HRMCs.It regulated gut microbiota and improved intestinal dysfunction,and down-regulated the protein levels of ECM-related proinflammatory factors,such as FN and IL-6.LMWF alleviated renal pathological changes and inhibited the renal dysfunction.Our study provided references for further mechanism study on function of brown algal polysaccharides on DN,and potentially developed macromolecular bioactive substances as marine drugs in the future.