U.S. researchers said Tuesday that they have identified an enzyme that may play a central role in the development of obesity in mid-life.

　　本周二，美国研究者表示称，他们发现了一种可能在中年人发福现象中起到核心作用的酶。

　　In two groups of mice being fed high-fat foods, those who received an inhibitor that blocked the enzyme had a 40 percent decrease in weight gain compared with those that did not receive the drug.

　　在两组喂食高脂肪食物的小白鼠中，一组被使用了阻断这种酶的抑制剂，结果发现相比于另一组没有用药的小白鼠，这组小白鼠体重增加量要少40%。

　　The findings, published in the U.S. journal Cell Metabolism, could upend current notions about why people gain weight as they age, and could one day lead to more effective weight-loss medications.

　　该研究结果刊载于美国杂志《细胞新陈代谢(Cell Metabolism)》，可能会颠覆人们对于随着年龄增长身体发福这一现象的认知，或许有一天能够帮助研制出更有效的减肥药。

　　"Our society attributes the weight gain and lack of exercise at mid-life (approximately 30 to 60 years) primarily to poor lifestyle choices and lack of will power, but this study shows that there is a genetic program driven by an overactive enzyme that promotes weight gain and loss of exercise capacity at mid-life," said lead study author Jay H. Chung, head of the Laboratory of Obesity and Aging Research at the National Heart, Lung, and Blood Institute (NHLBI), part of the U.S. National Institutes of Health.

　　杰伊·常是这项研究的主要作者，他是美国心肺血液研究所(该研究所是美国国家卫生研究院的一部分)下属肥胖和衰老研究室主任，他说道：“我们社会一般认为中年人(30到60岁)体重增加和缺乏锻炼是因为不良的生活方式和缺乏意志力的原因，但是这项研究表明也存在着遗传因素——一种过度活跃的酶会使得人们中年时体重增加、丧失运动能力。”

　　Researchers have known for years that losing weight and maintaining the capacity to exercise tend to get harder beginning between ages 30 to 40 -- the start of mid-life.

　　多年来研究人员发现，在刚步入中年时(30到40岁)减肥和保持运动能力往往会变得越来越困难。

　　In fact, it’s estimated that an average adult in America gains 30 pounds (13.6 kilograms) from age 20 to 50, even though food intake usually decreases during this period.

　　事实上据估计，美国成年人在20到50岁期间会平均增重30磅(约合13.6公斤)——即使这一年龄段人的进食量通常会减少。

　　Scientists have developed new therapies for obesity, including fat-fighting pills, but many of those therapies have failed.

　　科学家们也已经开发出了治疗肥胖的新方法，包括减肥药，但是许多治疗方法都失败了。

　　Chung and his associates searched for biochemical changes that occurred in middle-aged animals that are equivalent to 45 years in humans.

　　Chung和他的同事们在中年动物(相当于45岁的人类)的身体上寻找生物学变化。

　　They found that an enzyme called DNA-dependent protein kinase, or DNA-PK, increases in activity with age.

　　他们发现随着年龄的增长，一种被称之为DNA依赖蛋白激酶(DNA-dependent protein kinase)的物质活性与日俱增。

　　Further work showed that DNA-PK promotes conversion of nutrients to fat and decreases the number of mitochondria, tiny organelles in the cells that turn fat into energy to fuel the body.

　　进一步的研究发现，DNA依赖蛋白激酶会促进营养物质转化为脂肪，并且减少线粒体的数量——而线粒体是将脂肪转化为能量以供应人体的细胞器。

　　Mitochondria can be found in abundance among young people, but the numbers drop considerably in older people.

　　年轻人体内存在着大量线粒体，但是老年人体内线粒体的数量却大幅下降。

　　Researchers know that decreased mitochondria can promote obesity as well as loss of exercise capacity.

　　研究人员发现，线粒体数量的减少会促进肥胖、并且导致运动能力丧失。

（编辑：何莹莹）