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  剑6Test3雅思阅读Passage3原文翻译-寻找抗衰老药

  The Search for the Anti-aging Pill

  寻找抗衰老药

  In government laboratories and elsewhere, scientists are seeking a drug able to prolong life and youthful vigor. Studies of caloric restriction are showing the way

  在政府实验室等地，科学家们正在寻找能够延长生命和保持青春活力的药物。有关热量限制的研究为我们指明了出路。

  As researchers on aging noted recently, no treatment on the market today has been proved to slow human aging — the build-up of molecular and cellular damage that increases vulnerability to infirmity as we grow older. But one intervention, consumption of a low-calorie*yet nutritionally balanced diet, works incredibly well in a broad range of animals, increasing longevity and prolonging good health. Those findings suggest that caloric restriction could delay aging and increase longevity in humans, too.

  衰老问题的研究者们最近指出，目前市面上还没有任何疗法证明可以延缓人类衰老。衰老是一种随着年龄增长，人体内分子与细胞损伤的累积导致人越来越虚弱的现象。然而，有一种干预措施对许多动物都十分有效，那就是低热量且营养均衡的饮食，它会延长实验动物的寿命并维系健康。这些研究结果表明，限制热量的摄取可能也会延缓衰老，延长人类的寿命。

  Unfortunately, for maximum benefit, people would probably have to reduce their caloric intake by roughly thirty per cent, equivalent to dropping from 2,500 calories a day to 1,750. Few mortals could stick to that harsh a regimen, especially for years on end. But what if someone could create a pill that mimicked the physiological effects of eating less without actually forcing people to eat less? Could such a ‘caloric-restriction mimetic’, as we call it, enable people to stay healthy longer, postponing age-related disorders (such as diabetes, arteriosclerosis, heart disease and cancer) until very late in life? Scientists first posed this question in the mid-1990s, after researchers came upon a chemical agent that in rodents seemed to reproduce many of caloric restriction’s benefits. No compound that would safely achieve the same feat in people has been found yet, but the search has been informative and has fanned hope that caloric-restriction (CR) mimetics can indeed be developed eventually.

  不幸的是，若想达到最佳效果，人们大概需要减少约30%卡路里的摄人量，相当于从每天2500大卡降低到1750大卡。很少有人能够坚持这样严格的养生之道，尤其是年复一年这样做。但能不能制造出一种药来模拟限食的生理效应，而又不需要强迫人们少吃东西呢?这种被我们称为“限食拟药”的药片是否能让人们长久保持健康，延缓老年疾病(比如糖尿病、动脉硬化症、心脏病及癌症)的发生，直到更老的时候?科学家们早在20世纪90年代中期就提出了这个问题，此前研究者们偶然发现了一种化学药剂，该药剂似乎可以在啮齿动物身上产生限制热量摄取的许多好处。至今我们还没有发现能够安全应用到人类身上并达到同样功效的药物，但研究经验助燃了希望之火，令我们相信，限食拟药终究会研制出来的。

  The benefits of caloric restriction

  限制能量摄入的好处

  The hunt for CR mimetics grew out of a desire to better understand caloric restriction’s many effects on the body. Scientists first recognized the value of the practice more than 60 years ago, when they found that rats fed a low-calorie diet lived longer on average than free-feeding rats and also had a reduced incidence of conditions that become increasingly common in old age. What is more, some of the treated animals survived longer than the oldest-living animals in the control group, which means that the maximum lifespan (the oldest attainable age), not merely the normal lifespan, increased. Various interventions, such as infection-fighting drugs, can increase a population’s average survival time, but only approaches that slow the body’s rate of aging will increase the maximum lifespan.

  寻找限食拟药的动机是我们想更多地了解限制热量摄取对身体的影响。科学家们早在60多年前就已经认识到限制热量摄人的益处。当时，他们发现被喂食低热量食物的鼠类平均寿命长于自由摄取食物的鼠类，而且也更少患鼠类衰老时的常见病。除此之外，食用低热食物的鼠类活得比对照组中最老的鼠类还要长，这表明不仅是平均寿命，连最大寿命(可活的最大年龄)也增加了。尽管抗感染药物等各种干预方法也可以增加种群的平均寿命，但只有通过降低身体衰老速率才能增加最大寿命。

  The rat findings have been replicated many times and extended to creatures ranging from yeast to fruit flies, worms, fish, spiders, mice and hamsters. Until fairly recently, the studies were limited to short-lived creatures genetically distant from humans. But caloric-restriction projects underway in two species more closely related to humans — rhesus and squirrel monkeys — have made scientists optimistic that CR mimetics could help people.

  鼠类的实验结果已经重复过多次，而且对酵母菌、果蝇、蠕虫、鱼、蜘蛛、小鼠及仓鼠的实验也都有同样的结果。迄今，这类研究针对的都只是与人类基因相去甚远的短命生物，然而，正在进行中的研究采用了恒河猴与松鼠猴这两种更接近人类的物种做实验对象，这使科学家们乐观地相信限食拟药可以帮助人类。

  The monkey projects demonstrate that, compared with control animals that eat normally, caloric-restricted monkeys have lower body temperatures and levels of the pancreatic hormone insulin, and they retain more youthful levels of certain hormones that tend to fall with age.

  对这些猴类的研究证实，比起正常饮食的对照组动物，限制热量摄人组猴子的体温和胰岛素浓度都较低，而且某些随年龄增长而降低的荷尔蒙在他们体内仍维持在年轻时的水平。

  The caloric-restricted animals also look better on indicators of risk for age-related diseases. For example, they have lower blood pressure and triglyceride levels (signifying a decreased likelihood of heart disease), and they have more normal blood glucose levels (pointing to a reduced risk for diabetes, which is marked by unusually high blood glucose levels). Further, it has recently been shown that rhesus monkeys kept on caloric-restricted diets for an extended time (nearly 15 years) have less chronic disease. They and the other monkeys must be followed still longer, however, to know whether low-calorie intake can increase both average and maximum life spans in monkeys. Unlike the multitude of elixirs being touted as the latest anti-aging cure, CR mimetics would alter fundamental processes that underlie aging. We aim to develop compounds that fool cells into activating maintenance and repair.

  在与衰老有关的疾病风险指数方面，这些热量摄人受限的动物看起来也更加健康。例如，它们的血压与甘油三酸酷含量都比较低(表示得心脏病的可能性较小)，血糖浓度也比较正常(表示得糖尿病的风险较低，糖尿病的特征是高于常规的血糖浓度)。此外，有关研究最近指出，长期限制热量摄人(将近15年)的恒河猴患慢性病的几率也较低。但想要知道限制热量摄人是否会延长猴类的平均寿命和最长寿命，我们还必须对这些恒河猴以及其他猴类做更长时间的跟踪研究。与众多被吹捧为最新抗衰老疗法的长生不老药不同，限食拟药会改变衰老的基本进程。我们的目标是研制出能够欺骗细胞进人保养与修复状态的药物。

  How a prototype caloric-restriction mimetic works

  限食拟药如何完成任务

  The best-studied candidate for a caloric-restriction mimetic, 2DG (2-deoxy-D-glucose), works by interfering with the way cells process glucose. It has proved toxic at some doses in animals and so cannot be used in humans. But it has demonstrated that chemicals can replicate the effects of caloric restriction; the trick is finding the right one.

  研究得最多、也是最有可能的限食拟药是2DG(2-去氧-D-葡萄糖)，它是通过影响细胞中葡萄糖的代谢过程而发挥作用的。实验发现，达到某一剂量时，2DG会对动物产生毒性，所以无法应用到人类身上。尽管如此，这表明有些化学药物的确可以模拟热量摄人受限的效果;关键在于如何找到合适的药物。

  Cells use the glucose from food to generate ATP (adenosine triphosphate), the molecule that powers many activities in the body. By limiting food intake, caloric restriction minimizes the amount of glucose entering cells and decreases ATP generation. When 2DG is administered to animals that eat normally, glucose reaches cells in abundance but the drug prevents most of it from being processed and thus reduces ATP synthesis. Researchers have proposed several explanations for why interruption of glucose processing and ATP production might retard aging. One possibility relates to the ATP-making machinery’s emission of free radicals, which are thought to contribute to aging and to such age-related diseases as cancer by damaging cells. Reduced operation of the machinery should limit their production and thereby constrain the damage. Another hypothesis suggests that decreased processing of glucose could indicate to cells that food is scarce (even if it isn’t) and induce them to shift into an anti-aging mode that emphasizes preservation of the organism over such ‘luxuries’ as growth and reproduction.

  细胞利用食物中的葡萄糖制造ATP(三磷酸腺苷)，该分子为身体的许多活动提供能量。通过限制食物的摄取量，可使进人细胞的葡萄糖降到最低，因此减少ATP的生成量。当食量正常的实验动物服用2DG时，葡萄糖大量进人细胞，但2DG会阻止大部分葡萄糖的代谢，因而降低ATP的合成量。研究人员提出了几种说法，解释为什么妨碍葡萄糖代谢与ATP合成可以延级衰老。其中一种说法与ATP生成过程中自由基的释放有关，人们认为自由基会损伤细胞，因此导致衰老以及像癌症这类与衰老有关的疾病。减少ATP生成机制的运作次数可以限制自由基的数量，从而减少细胞受到的伤害。另一种假设认为，葡萄糖代谢的降低让细胞以为食物不足(即使事实并非如此)，而促使细胞进人抗衰老的状态，这种状态着重的是机体本身的维持，而不是生长或繁殖这类“奢侈活动”。

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