【科普】氨基酸作為小鼠長壽「仙丹」的科學依據

2010-10-08 11:56

氨基酸作為小鼠長壽「仙丹」的科學依據

本文引用地址： http://www.sciencenet.cn/m/user_content.aspx?id=370801 《細胞——代謝》最近發表了義大利科學家的最新研究結果，初步證明支鏈氨基酸（亮氨酸、異亮氨酸和纈氨酸等）可以使小鼠壽命延長12%！相應地，此前美國科學家也曾在酵母中獲得類似結果。但是，迄今為止還沒有報道指出氨基酸對人類壽命有何影響。這樣看來，我們目前還只能說氨基酸肯定是人類營養添加劑，但不能斷言它們也是人類的長壽「仙丹」！這篇文章的題目是「支鏈氨基酸在中年小鼠中促進存活並維持心肌與骨骼肌線粒體生物發生」（Branched-Chain Amino Acid Supplementation Promotes Survival and Supports Cardiac and Skeletal Muscle Mitochondrial Biogenesis in Middle-Aged Mice），其主要研究結果是發現支鏈氨基酸能延長雄性小鼠的平均壽命、激活mTOR及eNOS信號轉導通路、強化中年小鼠線粒體生物發生及活性氧清除系統功能、改善年齡增長引起的肌肉損害等（附圖）。

圖解及注釋：紅色如地毯者代表一個心肌細胞（Cardiomyocytes）或骨骼肌纖維（Skeletal muscle fibers）；藍色如蠶蛹者代表線粒體（Mitochondria），其功能是消耗氧氣產生能量（ATP），同時也會釋放活性氧（ROS）；黃色如卵黃者代表細胞核（Nucleus），顯示了活性氧保護系統（ROS defense system）和線粒體基因表達（Mitochondrial gene expression）；箭頭所指為支鏈氨基酸（Branched-chain amino acids）激活哺乳類雷帕黴素靶點（mTOR）-內皮型一氧化氮合酶（eNOS)-一氧化氮（NO）信號轉導通路-基因表達級聯。許多證據顯示，線粒體的生物發生越頻繁，真核細胞存活的時間就越長。這是因為線粒體的功能與細胞壽命存在著密切關係，一般衰老細胞的線粒體數目減少，而活性氧自由基水平增高。相反，支鏈氨基酸不僅能大幅增加心肌及骨骼肌細胞中的線粒體數目，而且還能上調活性氧自由基清除系統的基因表達，進而整體提高細胞的抗衰老、抗脅迫能力，於是細胞乃至整個機體的壽命也就相應延長了。有趣的是，適度節食及鍛煉同樣能延長哺乳動物的壽命，其機理也是減少活性氧自由基對細胞的損害。從古至今人類一直都在追求長生不老，如今這個夢想似乎不再遙不可及了。據英國《每日電訊報》10月5日報道，科學家發現了一種能夠延年益壽的藥物，而且已經在小白鼠身上進行實驗，首次獲得成功。這種神奇的藥物就是由亮氨酸、異亮氨酸和纈氨酸這3種氨基酸組成的混合物，學名「支鏈氨基酸」。在實驗過程中，研究人員給被試小白鼠喝的水裡加入了這3種氨基酸，結果發現它們的壽命平均達到了869天，而普通小白鼠則只能存活大約774天。也就是說，「支鏈氨基酸」使小白鼠的生命延長了12%。在延長壽命的同時，小白鼠的機體內還發生了一系列積極的生物反應，比如細胞得以攝取更多的能量、自由基減少等。自由基是機體氧化反應中產生的有害化合物，具有強氧化性，可損害機體的組織和細胞，進而引起慢性疾病及衰老效應。經過這些體內變化，小白鼠看起來充滿活力，而且肌肉協調能力有所提高。研究人員介紹說，「支鏈氨基酸」是一種十分重要和有效的營養補劑，它可以幫助生物體自然地、沒有任何副作用地增強肌肉或獲得更多能量。去年，科學家已經發現這種氨基酸混合物在延長單細胞酵母壽命上的巨大作用。「人類首次證明了氨基酸混合物能夠延長小白鼠的壽命，」這項研究的主要研究員、來自義大利米蘭大學的恩佐·尼索里教授表示。他還指出，如果在此基礎上發明氨基酸補劑，那麼它很可能在未來造福人類，對於老年人或病人有很大幫助，尤其是那些患有以細胞能級降低為特徵的疾病的人，比如心力衰竭或慢性肺病患者等。這個新學說已經刊登在新一期的美國科學雜誌《細胞—代謝》（Cell Metabolism）上。前不久，俄羅斯科學家弗拉基米爾·斯庫拉喬夫宣布，他研製出一種可以抗衰老的藥物，有望兩年內投入市場。他自稱這種新葯能夠消除氧化對人體的負面影響，避免患上老年病，從而延長壽命多達數十年。 A genuine "elixir of life" - at least for miceA genuine "elixir of life" that can hold death at bay has been discovered by scientists. By Richard Alleyne, Science CorrespondentPublished: 6:00PM BST 05 Oct 2010CommentsThe treated mice had more stamina and improved muscle co-ordination Photo: ALAMY The cocktail of amino acids - building blocks of proteins - was found to increase the lifespan of mice by 12 per cent. Researchers believe it may also benefit humans, especially the elderly or sick. Related ArticlesElixir of life: past attempts to find eternal life The animals lived significantly longer than other mice fed a normal diet. Their lifespan range had a midpoint of 869 days compared with 774 days for untreated mice, a difference of 12 per cent. Longer survival was accompanied by biological changes which boosted the energy supply to cells and reduced oxidative damage caused by destructive molecules called free radicals. The treated mice had more stamina and improved muscle co-ordination. "This is the first demonstration that an amino acid mixture can increase survival in mice," said study leader Dr Enzo Nisoli, from the University of Milan in Italy. Last year scientists showed that the same amino acids, leucine, isoleucine and valine, could extend the lifespan of single-celled yeast. The new findings, reported in the journal Cell Metabolism, raise the possibility of amino acid supplements benefiting humans. The scientists pointed out that the mice studied were aged but otherwise healthy. They believe taking the amino acids might be especially helpful for the elderly or ill, particularly people with heart failure, chronic lung disease, or other conditions characterised by flagging energy levels. Dr Nisoli said a large patient trial was needed to provide evidence convincing enough for doctors. However, there was little financial incentive for companies to conduct such studies on dietary supplements. Leucine, isoleucine and valine, known as branched-chain amino acids (BCAAs), account for a fraction of the 20 amino acids from which proteins are made, but appear to have special anti-ageing properties. Mice given the three amino acids produced larger numbers of mitochondria - the rod-like "powerhouses" in cells that generate energy - in their heart and skeletal muscle. They also showed increased activity of SIRT1, a well-known longevity gene, and developed better defences against free radicals. BCAA nutritional supplements are readily available in health food stores and online. Amino acid supplements were likely to be more effective than consuming proteins containing the same amino acids, according to the researchers. Unlike protein, they did not have to be digested, and could enter the bloodstream immediately. "They come with no energy cost," said Dr Nisoli. In their paper the scientists wrote: "We have provided evidence that an original BCAA mixture increases average life span in male mice. "This was likely the consequence of increased mitochondrial biogenesis and reduced oxidative stress in cardiac and skeletal muscles. Our study offers a rationale for deeply exploring the role of amino acids in prevention and control of age-related disorders in humans." Email Print Share | Email | Print http://www.telegraph.co.uk/health/healthnews/8044018/A-genuine-elixir-of-life-at-least-for-mice.htmlTelegraphNewsHealth News Get feed updatesNews Get feed updatesUK News Get feed updatesScience Get feed updatesScience News Get feed updatesHealth Get feed updates AdvertisementAds by GoogleHealth FoodHealth SupplementHeart HealthProstate HealthHealth Nutrition
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