Effect And Molecular Mechanism Of Collagen From Sturgeon Bladder On Delaying Natural Skin Aging

With the rapid development of Chinese fishery,the processing methods are still lagging behind,leading to a large amount of scraps are produced during the processing.These scraps are rich in collagen,and discarding them will not only pollute the environment,but also cause the waste of resources.Collagen has a long history of application in delaying skin aging,but its molecular mechanism is still unclear,leading to controversial efficacy.In this study,collagen,extracted from sturgeon bladder,was evaluated from physical and chemical properties,digestion and absorption dynamics,delaying skin aging effect,and promoting FBs proliferation,secretion and molecular mechanism.The main contents and results are summarized as follows:(1)The extraction methods of collagen from sturgeon bladder were compared and its physicochemical properties were studied.The extraction rate of pepsin-solubilized collagen(PSC)was 92.29%,which had a typical gel electrophoresis pattern of type I collagen.The extraction rate of hot water-solubilized collagen(HSC)was 76.54%,and the molecular structure was relatively complete.The extraction rate of Swim bladder gelatin(SBG)was 84.83%,electrophoresis showed that the molecular structure of collagen basically disappeared and a large number of peptides were produced.The amino acid composition of the three collagen proteins or gelatin is similar,glycine content is the most abundant(about 1/3);the contents of alanine,glutamic acid,proline and hydroxyproline content are higher,the contents of aspartic acid and histidine content are lower,cysteine and tryptophan are not detected.(2)Dynamics of collagen digestion and absorption were studied by simulating gastrointestinal digestion,intestinal absorption and peripheral blood circulation.The degree of hydrolysis of collagen increased sharply to 25.11%.When it reached the peripheral blood circulation,the degree of hydrolysis reached 70.42%.Compared with gastrointestinal digestion stage,the content of collagen peptide decreased slightly to 84.44% and the average molecular weight decreased by 30% during intestinal absorption.Furthermore,the content of collagen peptide decreased,and themolecular weight all decreased significantly.The content of collagen peptide in blood continued to decrease to 26.55% continuously.The average molecular weight finally decreased to 380.76 Da.In the one-way intestinal perfusion experiment,the collagen peptide content was decreased and the absorption rate significantly increased,among which the jejunum absorption rate was the highest,reaching 61.11% and the lower ileum absorption rate increased to 78.67%.(3)The effect of collagen on delaying skin aging was studied by feeding healthy female SD rats at 6 months.The results showed that after oral administration of collagen with 3.85 g/kg bw.d,the dermal thickness of rats increased by 18.45%,the density of collagen fiber and hydroxyproline content in the skin were significantly increased by 22.17% and 41.39%,respectively,the elasticity of skin increased by51.54%,and the ratio of collagen typeIII and typeI decreased by 43.44%.The activities of CAT,SOD and GSH-px increased by 49.19%,49.47% and 24.31%,the content of MDA decreased by 31.99%.The morphology of skin tissue,collagen fibers and collagen types were significantly improved.(4)The regulation of collagen peptide on fibroblasts(FBs)and its molecular mechanism were studied by cell culture in vitro.Hyp-Gly showed the strongest proliferation activity of FBs,the number of cells exceeded 2.09 times of the control group,and the maximum dose of Hyp-Gly on FBs proliferation was 200 ?M.After Hyp-Gly cultured FBs for 24 hours,the content of type I collagen increased by about3.74 times compared with the control group,and the expression of type I collagen ?1gene COL1A1 mRNA increased by 2.46 times.Genistein(tyrosine kinase inhibitor)and H7(serine/threonine kinase inhibitor)significantly decreased the expression of FBs COL1A1 mRNA.The phosphorylation level of p38 was significantly increased in the 30 th and 60 th minutes after the treatment of Hyp-Gly.This indicates that Hyp-Gly can activate the MAPK cell signal transduction pathway through the phosphorylation of p38 protein,and promote the proliferation of FBs and the secretion of collagen.