摘要
为探究绿茶和红茶中的代表性组分对秀丽隐杆线虫在不同温度条件下的作用效果及机制,试验设置0.25、2.5、25 μmol/L 表没食子儿茶素没食子酸酯(epigallocatechin gallate,EGCG)和茶黄素(theaflavin,TF1),测定线虫在4 ℃和35 ℃条件下的存活率,进而测定在4 ℃、20 ℃和30 ℃条件下经25 μmol/L EGCG和TF1孵育后线虫体内脂肪含量和线粒体膜电位的变化。结果显示,25 μmol/L EGCG将热应激线虫的最大寿命和中位寿命分别提高了8.15%、22.44%,将冷应激线虫的最大寿命和中位寿命分别降低了20.25%、17.94%。25 μmol/L TF1对热应激线虫的存活率无显著影响,将冷应激线虫的最大寿命和中位寿命分别提高了9.43%、19.01%。在4 ℃条件下,EGCG和TF1孵育均提高了线虫体内的脂肪含量,TF1孵育降低了线虫的线粒体膜电位水平。在20 ℃条件下,EGCG和TF1具有明显的降脂作用,长时间孵育可显著提高衰老线虫线粒体活性。在30 ℃条件下,EGCG和TF1提高了线虫体内的脂肪含量。以上结果表明,在低温条件下TF1通过促进线粒体产热而非脂肪动员提高了线虫的存活率,而EGCG孵育可诱导线虫死亡。
流行病学研究表明,饮茶具有多种健康益处,日常生活中长期习惯性饮茶与高血压发病率和认知障碍风险呈负相
秀丽隐杆线虫(Caenorhabditis elegans)是一种发育迅速、生命周期短的非寄生线
N2野生型秀丽隐杆线虫、大肠杆菌OP50(E. coli OP50),Caenorhabditis Genetics Center (CGC);表没食子儿茶素没食子酸酯(EGCG,≥95%)、牛血清白蛋白(BSA)、Trito
提前制备涂布有E. coli OP50菌液的线虫生长培养基(nematode growth medium,NGM)平板,每5 d将成年线虫转移到平板上,每次挑取4~5条,置于20 ℃生化培养箱中进行恒温培养。
将同步化64 h后的秀丽隐杆线虫分别转移到含有EGCG和TF1的NGM平板上,于20 ℃下孵育5 d,每天使用S-basal缓冲液收集秀丽隐杆线虫后转移至新的NGM平板中以避免产卵带来的干扰。热、冷应激试验以DMSO为空白对照,每组3个平行,每个平行挑取约20条线虫分别置于35、4 ℃温度条件下培养。热应激试验每小时计数1 次线虫的死亡情况,直至所有线虫死亡,试验温度设置参考Wilson
将同步化64 h后的秀丽隐杆线虫分别转移到含有EGCG和TF1的NGM平板上,于不同温度(4、20、30 ℃)条件下分别孵育1、5和7 d。用提前冰浴的S-basal缓冲液收集线虫,洗涤3次以除去残留的菌液,随后将线虫转移至2 mL离心管并置于液氮中速冻成颗粒。将线虫颗粒在液氮预冷的研钵中与200 μL 5% Trito
线粒体膜电位(mitochondrial membrane potential,MMP)水平使用线粒体特异性染料四甲基罗丹明乙酯(tetramethylrhodamine ethyl ester,TMRE)检测。试验以1 μmol/L FCCP为阳性对照,100 μmol/L TMRE为荧光染料。试验时将同步化64 h后的秀丽隐杆线虫分别转移到含有EGCG和TF1的NGM平板上,于不同温度(4、20、30 ℃)条件下孵育1 h、2 h、12 h、24 h、5 d和7 d。提前制备热灭活的E. coli OP50菌液,与100 μL浓度为100 μmol/L的TMRE检测液混合后涂布于NGM平板上,避光吹干。用S-basal缓冲液分别收集孵育1、2、12、24 h及5 d和7 d的线虫,转移至含有TMRE染料的平板上,于20 ℃下孵育2 h。孵育结束后,用S-basal缓冲液收集线虫,转移至含有热灭活E. coli OP50菌液的NGM平板上使其自由爬行1 h。最后收集线虫,以100 μL/孔将线虫悬浮液加至黑色96孔酶标板中。荧光强度测定条件为激发波长540 nm、发射波长595 nm。测定完毕后,使用0.01% Trito
使用BCA蛋白测定试剂盒测定秀丽隐杆线虫体内的蛋白质含量。取超声破碎、离心后的线虫上清液,按照BCA蛋白测定试剂盒的操作说明加样,37 ℃条件下孵育30 min后于波长562 nm处测定吸光值。
由

图1 0.25~25 μmol/L EGCG(A)和TF1(B)孵育后35 ℃条件下热应激秀丽隐杆线虫的存活率
Fig.1 Survival rate of heat stressed C. elegans at 35 ℃ after incubation with 0.25-25 μmol/L EGCG(A) and TF1(B)
P<0.05表示试验组与对照组之间有显著性差异。 P<0.05 represents significant differences between the experimental group and the control groups.
如

图2 0.25~25 μmol/L EGCG(A)和TF1(B)孵育后4 ℃条件下冷应激秀丽隐杆线虫的存活率
Fig.2 The survival rate of cold stressed C. elegans at 4 ℃ after incubationwith 0.25-25 μmol/L EGCG(A) and TF1(B)
P<0.05表示试验组与对照组之间有显著性差异。 P<0.05 represents significant differences between the experimental group and the control groups.
根据冷、热应激试验结果,选取25 μmol/L的 EGCG和TF1孵育秀丽隐杆线虫至不同时间点后测定其体内脂肪含量。由

图3 4 ℃(A)、20 ℃(B)、30 ℃(C)条件下经25 μmol/L EGCG和TF1孵育后秀丽隐杆线虫体内的脂肪含量
Fig.3 Fat content of C. elegans at 4 ℃(A),20 ℃(B),30 ℃(C) after incubation with 25 μmol/L EGCG and TF1
同一时间不同字母表示有显著性差异(P<0.05)。The different letters in the same time indicate significant differences(P<0.05).

图4 4 ℃(A)、20 ℃(B)、30 ℃(C)条件下经25 μmol/L EGCG和TF1孵育后秀丽隐杆线虫线粒体膜电位水平
Fig.4 Mitochondrial membrane potential of C. elegans at 4 ℃(A),20 ℃(B),30 ℃(C)after incubation with 25 μmol/L EGCG and TF1
差异性用“*”(P<0.05)、“**”(P<0.01)和“***”(P<0.001)表示。Differences are indicated by“*”(P<0.05),“**”(P<0.01)and “***”(P<0.001).
环境温度是影响生物体存活率的重要因素之一,较低的环境温度可以延长变温动物的寿
为进一步验证EGCG及TF1对热、冷应激秀丽隐杆线虫的保护作用差异,本研究测定了不同温度条件下EGCG和TF1对秀丽隐杆线虫脂肪含量和线粒体膜电位水平的影响。有文献报道,冷应激可激活PKA信号进而上调激素敏感脂肪酶hosl-1的表达,脂肪酶诱导脂肪动员,导致甘油积累,从而保护秀丽隐杆线虫免受冷应激伤
线粒体功能与人体稳态息息相关,人类许多疾病的发生和发展均与线粒体功能紊乱相关,因此,研究外源性物质对其功能的影响尤为重要。研究表明,黄酮类化合物作为质子载体,通过线粒体解偶联消散线粒体膜电位诱导线粒体自噬,从而减轻与衰老相关的神经退行性
综上,在35 ℃热应激条件下,EGCG对秀丽隐杆线虫的保护作用强于TF1;在4 ℃冷应激条件下,TF1对秀丽隐杆线虫的保护作用强于EGCG。在冷、热应激条件下,当孵育浓度为25 μmol/L时二者对比最显著。与对照组相比,4 ℃条件下经25 μmol/L TF1短时间孵育后,秀丽隐杆线虫体内具有更高的脂肪含量和更低的线粒体膜电位,而25 μmol/L EGCG对秀丽隐杆线虫线粒体膜电位无显著影响,说明在冷应激条件下TF1可能是通过发挥类似线粒体解偶联剂的作用而非脂肪动员,进一步促进线粒体生热从而减轻冷应激对秀丽隐杆线虫造成的伤害。正常温度条件下EGCG和TF1均具有较好的降脂作用。随着孵育时间的延长,衰老秀丽隐杆线虫行为迟钝、生理功能下降,而EGCG和TF1可减轻衰老对其造成的不利影响,改善其线粒体功能。
参考文献References
YIN J Y,DUAN S Y,LIU F C,et al.Blood pressure is associated with tea consumption:a cross-sectional study in a rural,elderly population of Jiangsu China[J].The journal of nutrition,health & aging,2017,21(10):1151-1159. [百度学术]
GU Y J,HE C H,LI S,et al.Tea consumption is associated with cognitive impairment in older Chinese adults[J].Aging & mental health,2018,22(9):1232-1238. [百度学术]
KANWAR J,TASKEEN M,MOHAMMAD I,et al.Recent advances on tea polyphenols[J].Frontiers in bioscience,2012,4(1):111-131. [百度学术]
李朝云,邱树毅,班世栋,等.绿茶中表没食子儿茶素没食子酸酯生物活性研究进展[J].中国酿造,2019,38(9):12-18.LI Z Y,QIU S Y,BAN S D,et al.Research progress on bioactivity of epigallocatechin gallate in green tea[J].China brewing,2019,38(9):12-18(in Chinese with English abstract). [百度学术]
薛金金,尹鹏,张建勇,等.植物源多酚氧化酶氧化儿茶素形成茶黄素和聚酯型儿茶素的研究[J].食品工业科技,2019,40(20):76-81.XUE J J,YIN P,ZHANG J Y,et al.Screening of plant-derived polyphenol oxidase for the formation of theaflavins and theasinensins from the oxidation of catechins[J].Science and technology of food industry,2019,40(20):76-81(in Chinese with English abstract). [百度学术]
HE H F.Research progress on theaflavins:efficacy,formation,and preparation[J/OL].Food & nutrition research,2017,61(1):1344521[2022-05-19].https://doi.org/10.1080/16546628.2017.1344521. [百度学术]
徐燕,朱创,邰玲玲,等.红茶化学成分及生理活性的研究进展[J].安徽农业大学学报,2020,47(5):687-696.XU Y,ZHU C,TAI L L,et al.Research advance on chemical components and biological activities of black tea[J].Journal of Anhui Agricultural University,2020,47(5):687-696(in Chinese with English abstract). [百度学术]
WU Y Y,LI W,XU Y,et al.Evaluation of the antioxidant effects of four main theaflavin derivatives through chemiluminescence and DNA damage analyses[J].Journal of Zhejiang University,2011,12(9):744-751. [百度学术]
张静.茶黄素对阿尔茨海默病模型的神经保护作用研究[D].长沙:湖南农业大学,2017.ZHANG J.Neuroprotective effects of theaflavins on Alzheimer’s disease model[D].Changsha:Hunan Agricultural University,2017(in Chinese with English abstract). [百度学术]
OH J,JO S H,KIM J S,et al.Selected tea and tea pomace extracts inhibit intestinal α-glucosidase activity in vitro and postprandial hyperglycemia in vivo[J].International journal of molecular sciences,2015,16(4):8811-8825. [百度学术]
CORSI A K,WIGHTMAN B,CHALFIE M.A transparent window into biology:a primer on Caenorhabditis elegans[J].Genetics,2015,200(2):387-407. [百度学术]
BRENNER S.The genetics of Caenorhabditis elegans[J].Genetics,1974,77(1):71-94. [百度学术]
CULETTO E,SATTELLE D B.A role for Caenorhabditis elegans in understanding the function and interactions of human disease genes[J].Human molecular genetics,2000,9(6):869-877. [百度学术]
熊立瑰.茶叶中表没食子儿茶素没食子酸酯(EGCG)抗衰老的低促效应研究[D].长沙:湖南农业大学,2015.XIONG L G.Hormesis of epigallocatechin-3-gallate(EGCG)to antiaging[D].Changsha:Hunan Agricultural University,2015(in Chinese with English abstract). [百度学术]
ZHANG L Z,JIE G L,ZHANG J J,et al.Significant longevity-extending effects of EGCG on Caenorhabditis elegans under stress[J].Free radical biology and medicine,2009,46(3):414-421. [百度学术]
XIONG L G,HUANG J N,LI J,et al.Black tea increased survival of Caenorhabditis elegans under stress[J].Journal of agricultural and food chemistry,2014,62(46):11163-11169. [百度学术]
KUDO N,ARAI Y,SUHARA Y,et al.A single oral administration of theaflavins increases energy expenditure and the expression of metabolic genes[J/OL].PLoS One,2015,10(9):e0137809[2022-05-19].https://doi.org/10.1371/journal.pone.0137809. [百度学术]
LEE M S,SHIN Y,JUNG S,et al.Effects of epigallocatechin-3-gallate on thermogenesis and mitochondrial biogenesis in brown adipose tissues of diet-induced obese mice[J/OL].Food & nutrition research,2017,61(1):1325307[2022-05-19].https://doi.org/10.1080/16546628.2017.1325307. [百度学术]
WILSON M A,SHULITT-HALE B,KALT W,et al.Blueberry polyphenols increase lifespan and thermotolerance in Caenorhabditis elegans[J].Aging cell,2006,5(1):59-68. [百度学术]
LIU F,XIAO Y,JI X L,et al.The cAMP-PKA pathway-mediated fat mobilization is required for cold tolerance in C. elegans[J/OL].Scientific reports,2017,7:638[2022-05-19].https://doi.org/10.1038/s41598-017-00630-w. [百度学术]
CARVALHO G B,DRAGO I,HOXHA S,et al.The 4E-BP growth pathway regulates the effect of ambient temperature on Drosophila metabolism and lifespan[J].PNAS,2017,114(36):9737-9742. [百度学术]
XIAO R,ZHANG B,DONG Y M,et al.A genetic program promotes C. elegans longevity at cold temperatures via a thermosensitive TRP channel[J].Cell,2013,152(4):806-817. [百度学术]
ZHOU L,TONG H X,TANG H Q,et al.Fatty acid desaturation is essential for C.elegans longevity at high temperature[J/OL].Mechanisms of ageing and development,2021,200:111586[2022-05-19].https://doi.org/10.1016/j.mad.2021.111586. [百度学术]
WAGNER A E,PIEGHOLDT S,RABE D,et al.Epigallocatechin gallate affects glucose metabolism and increases fitness and lifespan in Drosophila melanogaster[J].Oncotarget,2015,6(31):30568-30578. [百度学术]
NIU Y C,NA L X,FENG R N,et al.The phytochemical,EGCG,extends lifespan by reducing liver and kidney function damage and improving age-associated inflammation and oxidative stress in healthy rats[J].Aging cell,2013,12(6):1041-1049. [百度学术]
IMRAN A,BUTT M S,ARSHAD M S,et al.Exploring the potential of black tea based flavonoids against hyperlipidemia related disorders[J/OL].Lipids in health and disease,2018,17(1):57[2022-05-19].https://doi.org/10.1186/s12944-018-0688-6. [百度学术]
AIZAWA T,YAMAMOTO A,UENO T.Effect of oral theaflavin administration on body weight,fat,and muscle in healthy subjects:a randomized pilot study[J].Bioscience biotechnology and biochemistry,2017,81(2):311-315. [百度学术]
CHO I,SONG H O,CHO J H.Flavonoids mitigate neurodegeneration in aged Caenorhabditis elegans by mitochondrial uncoupling[J].Food science & nutrition,2020,8(12):6633-6642. [百度学术]
金甲,张凤,杨玲玲,等.线粒体解偶联剂的研究进展[J].生命科学,2013,25(7):707-715.JIN J,ZHANG F,YANG L L,et al.Progress of study on mitochondrial uncoupler[J].Chinese bulletin of life sciences,2013,25(7):707-715(in Chinese with English abstract). [百度学术]