Effect Of Purple Yam Polysaccharides(PYPs) On Anti-aging Activity And Its Mechanism

Purple yam is the dry rhizome of dioscoreaceae plants,with purple brown skin and bright purple flesh.That is why it is named as 'purple yam'.It is rich in nutrients and tastes a little sweet,but belongs to the group of neutral foods according to traditional chinese medicine.High concentration of anthocyanin compounds make purple yam much more valuable in health care than the ordinary one.Purple yam is a potencially nutrientional source since it is thought to be good for lung and kidney,and may has certain beneficial effects on relieving spleen deficiency,diarrhea,dysentery and other diseases.This dissertation is aimed to explore the anti-aging biological activity of the purple yam polysaccharides(PYPs)and its mechanism.The main results are as follows:1.In order to explore the anti-aging activity of PYPs,the model of aging rats taking D-galactose(400 mg/kg bw)was established.The rats were treated with different dosages of PYPs(20,100,500 mg/kg bw),so as to investigate its antioxidant capacity.The results showed that PYPs can significantly reduce the amount of MDA,a peroxidation products in liver and brain.At the same time,PYPs can increase the activity of endogenous antioxidant enzymes SOD,CAT and GSH-Px,the T-AOC level of total antioxidant capacity,and the content of GSH in vivo.It was also observed that PYPs could affect the morphology of liver and brain tissue of aging rats,indicating that PYPs can protect the organs from being damaged by enhancing the antioxidant capacity of aging rats.2.The effect of PYPs on immune system in aging rats was studied through the observation of the changes of the index of thymus,spleen and other organs,and the content of cytokines IL-2 and IL-6 in the serum of aging rats being treated with PYPs.The results showed that the concentration of IL-2 factor in the serum of rats was significantly increased after treatment.IL-6 factor decreased obviously.The index of thymus and spleen significantly changed with the treatment dose.The spleen tissue morphology was improved,indicating that PYPs is functional in delaying immune senescence.PYPs can significantly reduce the AGEs products in aging rats.The results indicated that PYPs could prevent the non-enzymatic glycation reaction,and protect organs from damage.3.The anti-aging activity of PYPs was explored from the perspective of molecular biology in terms of changing key genes involved in aging cell signal path p53-p21 pathway and p16.The study adopted qRT-PCR to measure the expression of p16 and p21 genes in the liver and brain tissues of aging rats.The results showed that PYPs significantly reduced the expression of aging gene p16 and p21 and delayed the occurrence and progress of cell replicative senescence.The expression of p53 and p21 protein in the liver and brain was studied by Western blot.The results showed that PYPs can significantly down-regulate the expression of p53 and p21 protein in the liver and brain of the rat,thus inhibiting the occurrence and progress of aging from p53-p21 signaling pathway.4.In order to understand in-depth the anti-aging mechanism of PYPs,the model of cell aging induced by D-gal on HepG2 and PC 12 was established and the effect on senescent cells with PYPs administration was observed.The results showed that PYPs can slow down the cell's aging progress by testing with SA-?-gal staining,PYPs can improve the cell activity by CCK8 analysis,furthermore,PYPs can effectively prevent HepG2,PC 12 cell apoptosis.All affections of PYPs were dependent upon concentration.The Western blot on p53,p21,pRb expression in cell was implemented.It is found that the expression of p53,p21,pRb was decreased in D-gal group(p<0.05),nevertheless steep rised after PYPs treat(p<0.01 compared with D-gal group).This result showed the relation between the anti-aging activity of PYPs and p53-p21 signal pathway.It is further confirmed by cell cycle studying with PI staining:the cell column in G2/M phase was remarkably increased by PYPs administration(p<0.05),the cell cycle was delayed in the G2/M phase.It can be concluded that PYPs can delay cell senescence through p53-p21 pathway.5.The life-prolongation activity of PYPs was studied with C.elegans because life span is an intuitional indicator of delaying senility.It is discovered that the lifespan of C.elegans after PYPs administration was extended approximately 24%compared with control group,the locomotion,the number of swallowing and the brood size of C.elegans in PYPs group were increased.And the C.elegans viability of anti-heat and anti-oxidant were improved obviously by treated with PYPs.The research on daf-16 translocation revealed that the anti aging activity of PYPs can be achieved by promoting the daf-16 gene in cell and inducing the aging-associated genes expression.In conclusion,PYPs has a distinct anti-aging activity through p53-p21 pathway.