Effects And Mechanisms Of Oolong Tea Extracts And Catechin Dimers On Anti-aging And Age-related Neurodegenerative Diseases

Aging is an inevitable process of all organisms and it is also the main cause of most neurodegenerative diseases.Oxidative stress is closely related to aging,and it plays an important role in the process of neuronal cell death and impaired neurite outgrowth in age-related neurodegenerative diseases.Oolong tea is a semi-fermented tea,due to the uniqueness of fresh leaf and processing,its biological activity components is quite unique,especially the catechin dimers oolonghomobisflavan A(OFA)and oolonghomobisflavan B(OFB).Qing flavour Tieguanyin oolong tea(QFT),Nong flavour Tieguanyin oolong tea(NFT)and Chen flavour Tieguanyin oolong tea(CFT)were used as experimental materials,the main purpose of this study is to investigate the effects and mechanisms of three different oolong tea extracts(OTEs)and catechin dimers(OFs)on anti-aging and age-related neurodegenerative diseases through cultured neuronal cells(Neuro-2a and HT22)in vitro and Caenorhabditis elegans in vivo.The main findings are as follows:(1)Using a widely-targeted metabolomics technology to detect all metabolites of OTEs(QFT,NFT and CFT),a total of 664 metabolites were detected,with flavonoids dominating,followed by phenolic acids,amino acids,and its derivatives,lipids,organic acids,nucleotides and its derivatives,alkaloids,tannins,lignans and coumarin compounds,terpenoids.The number of differential metabolites in the QFT vs NFT,QFT vs CFT,and NFT vs CFT comparison groups were screened as 184(104up-regulated,80 down-regulated),343(155 up-regulated,188 down-regulated),and 222(107 up-regulated,115 down-regulated).(2)Using wild-type C.elegans N2 and a variety of transgenic(mutant)C.elegans as models,exploring the effects and mechanisms of OTEs and OFs on the mean lifespan of C.elegans.The results showed that OTEs could not prolong the mean lifespan of wild-type C.elegans N2 under normal culture conditions,but could increase the resistance of the C.elegans to chronic(high glucose-induced N2,mutant nematode TK22)and acute(80?M juglone)oxidative stress,it can significantly improve the survival rate of C.elegans and prolong lifespan via DAF-16 signaling pathway under oxidative stress condition.OFs can significantly increase the survival rate of C.elegans and extend the mean lifespan via DAF-16signaling pathway under both normal culture and acute oxidative stress conditions.In addition,the effects of OTEs and OFs on C.elegans survival or mean lifespan is not connected with the SKN-1 signaling pathway.(3)Using in vitro cultured neuronal cells(Neuro-2a and HT22)as models,MTT,LDH,q RT-PCR,cell morphology methods were used to detect the protective effects of OTEs and OFs against glutamate-induced neuronal toxicity.The results show that both OTEs and OFs can up-regulate the m RNA expression of neuronal antioxidant enzymes such as GSTo1,GSTa2,GPx,SOD1,SOD2 and reduce the accumulation of ROS in neurons,thereby enhancing the protective effect of glutamate-induced neuronal toxicity and reducing neuronal cell death.(4)Using Neuro-2a neuronal cells as a model,under low concentration foetal bovine serum(1%FBS)culture conditions,q RT-PCR and cell morphology methods were used to detect the effects of OTEs and OFs on cell neurite outgrowth.The results show that both OTEs and OFs promote neurite outgrowth by up-regulating the expression of the transmembrane protein Ten-4,and this result is further verified by detecting the up-regulation of the neurite biomarker GAP-43 expression.(5)Using transgenic C.elegans neurodegenerative disease models to explore the neuroprotective effects of OTEs and OFs.The results showed that both OTEs and OFs could not only delay the paralysis caused by the toxicity of A?_1-42-induced in transgenic strain CL4176,improve the chemotaxis ability of A?_1-42-induced chemotaxis deficient in transgenic strain CL2355,but also inhibit?-synuclein accumulation in transgenic strain NL5901.It is preliminarily proved that OTEs and OFs have anti-age-related neurodegenerative diseases in the C.elegans model.(6)Although QFT,NFT and CFT these three different Tieguanyin oolong tea extracts show some differences among the metabolites detected by widely-targeted metabolomics technology,the experimental results of this study reveals that there is no significant difference among the effects of these three oolong tea extracts on anti-aging and age-related neurodegenerative diseases.It indicates that their anti-aging and age-related neurodegenerative effects are probably caused by the special(semi-fermented)process of oolong tea and are not correlated with the processing methods of different types of Tieguanyin oolong tea.This kind of issue needs further study.In summary,this study reports for the first time the effects of OTEs and OFs on cultured neuronal cells(Neuro-2a and HT22)and C.elegans model,and found that OTEs and OFs have the effects of delaying aging and age-related neurodegenerative diseases.This discovery is of great significance for further improving the health benefits of oolong tea and expanding the consumption of oolong tea.It also provides a theoretical basis for natural products OFs as potential drug candidates for anti-aging and age-related neurodegenerative diseases.