Spindler’s team fed three mice a normal diet for their whole lives, and fed another three on half-rations.³ Three more mice were switched from the normal diet to half-feed³ for a month when they were 34 months old --- equivalent to about 70 human years.

The researchers checked the activity of 11,000 genes from the mouse livers, and found that 46 changed with age in the normally fed mice. The changes were associated with things like inflammation and free radical production4--- probably bad news for mouse health. In the mice that had dieted all their lives, 27 of those 46 genes continued to behave like young genes. But the most surprising finding was that the mice that only started dieting in old age also benefited from 70 per cent of these gene changes.

“This is the first indication that these effects kick in5 pretty quickly,” says Huber Warner from the National Institute on Aging near Washington, D.C..

No one yet knows if calorie restriction works in people as it does in mice, but Spindler is hopeful. “There’s attracting and tempting evidence out there that it will work,” he says.

If it does work in people, there might be good reasons for rejuvenating the liver. As we get older, our bodies are less efficient at metabolizing drugs, for example. A brief period of time of dieting, says Spindler, could be enough to made sure a drug is effective.

But Spindler isn’t sure the trade-off  is worth it6. “The mice get less disease, they live longer, but they’re hungry,” he says.   “Even seeing what a diet does, it’s still hard to go to a restaurant and say: ‘I can only eat half of that’.”

Spindler hopes we soon won’t need to diet at all. His company, Life Span Genetics in California, is looking for drugs that have the effects of calorie restriction.

词汇 ：

meager  adj.   不足的                             youthful   adj.   有青春活力的

vigor n. 精力，活力                    metabolize  vt. 使（一种物质）进入新陈代谢过程

 rejuvenation  n. 恢复活力，返老还童        liver  n. 肝脏

toxin  n.  毒素                                                    ration  n. 定量

inflammation  n. 炎症，发炎                          trade-off  n. 交换，交易

rejuvenate vt. 使恢复活力，使回春

注释：

1.       hang on to : 继续保留。例如：You should hang on to that painting --- it might be worth a lot of money one day. (你应该继续保留那幅画，或许有一天它会值很多钱。) 

2.       The genetic rejuvenation won’t reverse other damage caused by time for the mouse, but could help its liver metabolize drugs or get rid of toxins. 老鼠的肝部基因恢复活力不会逆转老鼠在其他方面的老化，但却有助于肝脏代谢药物或出去毒素。Other damage caused by time 岁月造成的其他方面的破坏，即“其他方面的老化”。Metabolize drugs: 代谢药物，即“使药物参与新陈代谢以提高药效”。Get rid of :  摆脱，除去。

3.       half-ration 和half-feed: 都是指“老鼠饲料正常定量（normal diet）的一半”。

4.       free radical production : 指“（有机体组织、器官等的）无限激增”。

5.       kick in: 意为“开始起作用”。如：We’re still waiting for the air conditioning to kick in. （我们还在等着空调开始起作用。）

6.       be worth it: 意为“值得，有益”。例如：They are expensive, but they are worth it. (那些东西很贵，但划得来。)

练习：

1.       According to the passage, which of the following is NOT true?

A)      Eating less than usual might make us live longer.

B)      If we go on a diet when old, we may keep healthy.

C)      Dieting might not be needed.

D)     We have to begin dieting from childhood.

2.       Why does the author mention an elderly mouse in paragraph 2?

A)      To describe the influence of old age on mice.

B)      To illustrate the effect of meager food on mice.

C)      To tell us how mice’s liver genes behave.

D)     To inform us of the process of metabolizing drugs.

3.       What can be inferred about completely normally fed mice mentioned in the passage?

A)      They will not experience free radical production.

B)      They will experience more genetic rejuvenation in their lifetime.

C)      They have more old liver genes to behave like young genes.

D)     They are more likely to suffer from inflammation.

4.       According to the author, which of the following most interested the researchers?

A)      The mice that started dieting in old age.

B)      27 of those 46 old genes that continued to behave like young genes.

C)      Calorie restriction that works in people.

D)     Dieting that makes sure a drug is effective.

5.       According to the last two paragraphs, Spindler believes that

A)      calorie restriction is very important to young people.

B)      seeing the effect of a diet, people will eat less than normal.

C)      drugs do not have the effects of calorie restriction.

 

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