| In recent years,collagen peptides have received extensive attention as an anti-skin aging health product.However,previous studies mostly focused on the beneficial effects of the oral administration of collagen peptides derived from the ocean on the aging of skin.However,Collagen peptides derived from poultry and their relative advantages on skin-aging were rarely investigated.Therefore,in this study,three methods were used to extract collagen from the chicken bone of spent-hens,and the effects of various extraction methods on the characteristics,functional properties,antioxidant properties and acceptability of chicken bone collagen were compared;The technological conditions of preparing chicken bone collagen peptides(CPs)by enzymatic hydrolysis of chicken bone collagen,were optimized,and the sequence,molecular weight distribution and in vitro antioxidant activity of CPs were analyzed;Further,mice with skin aging induced by ultraviolet(UV)combined with D-galactose were applied as model,using skin transcriptome sequencing,LC-MS/MS non-targeted metabolome and other methods to investigate the effect and mechanism of dietary supplementation of CPs on alleviating skin aging in mice,and compared the effect and mechanism of oral and external skin penetration of CPs on alleviating skin aging in mice.The main results are as follows:1.The extraction rates of collagen extracted from chicken bones of spent-hens by acid,alkali and enzymolysis were 3.39%,2.42% and 9.63%,respectively.The analysis of the amino acid composition,SDS-PAGE,Fourier transform infrared spectroscopy,differential scanning caborimetry(DSC),and ultraviolet full spectrum showed that the collagen extracted by the three methods had typical collagen characteristics,good functional properties and in vitro antioxidant activity.However,acid and alkaline extraction have adverse effects on the secondary structure of chicken bone collagen.In contrast,chicken bone collagen prepared by enzymatic hydrolysis has regular,loose and porous spongy microstructure,a more complete collagen secondary structure,higher extraction yield,antioxidant activity,functional properties and organoleptic acceptability.Therefore,enzymatic hydrolysis was the best method to prepare collagen from bones of spent-hens.2.Papain is the most effective enzyme for the enzymatic hydrolysis of chicken bone collagen.The optimal process conditions for the enzymatic hydrolysis of chicken bone collagen are: enzymatic hydrolysis temperature 63 °C,enzymatic hydrolysis time 4.9 h,and enzyme concentration 1/42 g/m L with a p H of 7.2.Under these conditions,the degree of hydrolysis of chicken bone collagen was 11.86 %.The prepared CPs were mainly small molecular peptides with a molecular weight of <3000 Da(87.61%),and the CPs had good free radical scavenging ability in vitro.3.In vivo experiments results showed that dietary supplementation of CPs had a significant relieving effect on aging skin in mice induced by UV combined with D-galactose,indicated by the changes in the composition and structure of the aging skin,improvement of skin antioxidant level,and inhibition of inflammation.The relieving effect was positively correlated with the dose of CPs.Further investigation showed that CPs first reduce the level of skin oxidation,activate the TGF-β/Smad signaling pathway to promote collagen synthesis,inhibit the expression of the nuclear transcription factor activator protein AP-1(c-Jun and c-Fos),and then inhibit the expression of MMP-1/3 to inhibit collagen degradation,and inhibit skin inflammation to alleviate skin aging in mice.Moreover,lysosomes activated after oral administration of CPs may be an important pathway for CPs to anti-skin aging.4.The LC-MS/MS non-targeted metabolome results showed that after oral administration of CPs,17 and 21 significantly different metabolites were screened from mouse skin in the positive and negative ion modes,respectively(P<0.05).These differential metabolites are mainly involve five metabolic pathways,namely glycolysis and gluconeogenesis,citric acid cycle,pyruvate metabolism,glyoxylic acid and dicarboxylic acid metabolism,and nicotinate and nicotinamide metabolism.Metabolic pathway analysis showed that the mechanism of CPs alleviating mouse skin aging was closely related to energy metabolism,fatty acid,amino acid and vitamin metabolism.5.Different supplementary form of CPs treatment showed that both oral and external skin penetration of CPs could alleviate the UV combined with D-galactose induced skin aging in mice,but the current research results are difficult to compare the advantages and disadvantages of the two methods.Mechanistically,CPs external skin penetration into the skin also promoted collagen synthesis,inhibited the expression of MMP-1 and MMP-3,and alleviated skin aging in mice by activating TGF-β/Smad signaling pathway.6.Transcriptome sequencing analysis found that the enrichment results of up-regulated genes GO and KEGG in mouse skin both after oral or external skin penetration of CPs first pointed to lysosomes,which may be that CPs treatment activated the functional activity of lysosomes in the skin.In addition,the pathways involved in differential metabolites in mouse skin after oral administration of CPs are closely related to energy metabolism.Mitochondria,as the center of cellular energy metabolism,its dysfunction will lead to cell senescence and death.Therefore,CPs may promote metabolic activities such as energy,fatty acids,and amino acids by activating mitochondrial function in aging skin cells.Based on the transcriptome and metabolome results show that CPs may alleviate skin aging in mice by activating lysosomal activity and mitochondrial function,which is worthy of focus in follow-up studies.The results of this study showed that CPs alleviated mouse skin aging by activating TGF-β/Smad signaling pathway to promote collagen synthesis,inhibit the expression of the nuclear transcription factor activator protein AP-1,and then inhibit the expression of MMP-1/3 to inhibit collagen degradation,and inhibit skin inflammation.Further analysis showed that chicken bone collagen peptides may alleviate skin aging in mice by activating lysosome activity and mitochondrial function. |
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