Clever genetic detective work may have found out the reason why a near-starvation diet prolongs the life of many animals.
Ronald Kahn at Harvard Medical School in Boston, US, and his colleagues have been able to extend the lifespan (寿命) of mice by 18 percent by blocking the rodent’s (啮齿动物) increase of fat in specific cells. This suggests that thinness-and not necessarily diet-promotes long life in "calorie (热量单位，卡) restricted" animals.
"It’s very cool work," says aging researcher Cynthia Kenyon of the University of California, San Francisco. "These mice eat all they want, lose weight and live longer. It’s like heaven. "
Calorie restriction dramatically extends the lifespan of organisms as different as worms and rodents. Whether this works in humans is still unknown, partly because few people are willing to submit to such a strict diet.
But many researchers hope they will be able to trigger the same effect with a drug once they understand how less food leads to a longer life. One theory is that eating less reduces the increase of harmful things that can damage cells. But Kahn’s team wondered whether the animals simply benefit by becoming thin.
To find out, they used biology tricks to disrupt the insulin (胰岛素) receptor (受体) gene in lab mice—but only in their fat cells. "Since insulin is needed to help fat cells store fat, these animals were protected against becoming fat," explains Kahn.
This slight genetic change in a single tissue had dramatic effects. By three months of age, Kahn’s modified mice had up to 70 percent less body fat than normal control mice, despite the fact that they ate 55 percent more food per gram of body weight.
In addition, their lifespan increased. The average control mouse lived 753 days, while the thin rodents averaged a lifespan of 887 days. After three years, all the control mice had died, but one-quarter of the modified rodents were still alive.
"That they get these effects by just manipulating the fat cells is controversial, "says Leonard Guarente of the Massachusetts Institute of Technology, who studies calorie restriction and aging.
But Guarente says Kahn has yet to prove that the same effect is responsible for increased lifespan in calorie restricted animals. "It might be the same effect or there might be two routes to long life," he points out, "and that would be very interesting./

What does the last sentence in the third paragraph imply（　）

A:People like to lose weight, but they do not like to eat less. B:People want to go to heaven, but they do not want to die. C:Mice will go to heaven if they lose weight. D:Mice enjoy losing weight.

A. meager diet may give you health and long life, but it’s not much fun — and it might not even be necessary. We may be able to hang on to most of that youthful vigor even if we don’t start to diet until old age.
Stephen Spindler and his colleagues from the University of California at Riverside have found that some of an elderly mouse’s liver genes can be made to behave as they did when the mouse was young simply by limiting its food for four weeks. 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.
Spindler’s team fed three mice a normal diet for their whole lives, and fed another three on half-rations. Three more mice were switched from the normal diet to half-feed 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 production — 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 in 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 make sure a drug is effective.
But Spindler isn’t sure the trade-off is worth it. "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, Lifespan Genetics in California, is looking for drugs that have the effects of calorie restriction.
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.

Clever genetic detective work may have found out the reason why a near-starvation diet prolongs the life of many animals.
Ronald Kahn at Harvard Medical School in Boston, U.S., and his colleagues have been able to extend the lifespan (寿命) of mice by 18 per cent by blocking the rodent’s (啮齿动物) increase of fat in specific cells. This suggests that thinness--and not necessarily diet--promotes long life in "calorie (热量卡) restricted" animals.
"It’s very cool work," says aging researcher Cynthia Kenyon of the University of California, San Francisco. "These mice eat all they want, lose weight and live longer. It’s like heaven."
Calorie restriction dramatically extends the lifespan of organisms as different as worms and rodents. Whether this works in humans is still unknown partly because few people are willing to submit to such a strict diet.
But many researchers hope they will be able to trigger the same effect with a drug once they understand how less food leads to a longer life. One theory is that eating less reduces the increase of harmful things that can damage cells. But Kahn’s team wondered whether the animals simply benefit by becoming thin.
To find out, they used biology tricks to disrupt the insulin (胰岛素) receptor (受体) gene in lab mice, but only in their fat cells. "Since insulin is needed to help fat cells store fat, these animals were protected against becoming fat," explains Kahn.
This slight genetic change in a single tissue had dramatic effects. By three months of age, Kahn’s modified mice had up to 70 per cent less body fat than normal control mice, despite the fact that they ate 55 per cent more food per gram of body weight.
In addition, their lifespan increased. The average control mouse lived 753 days, while the thin rodents averaged a lifespan of 887 days. After three years, all the control mice had died, but one-quarter of the modified rodents were still alive.
"That they get these effects by just manipulating the fat cells is controversial," says Leonard Guarente of the Massachusetts Institute of Technology, who studies calorie restriction and aging.
But Guarente says Kahn has yet to prove that the same effect is responsible for increased lifespan in calorie-restricted animals. "It might be the same effect or there might be two routes to long life," he points out, "and that would be very interesting./
What does the last sentence in the third paragraph imply

A:People like to lose weight, but they do not like to eat less B:People want to go to heaven, but they do not want to die C:Mice will go to heaven if they lose weight D:Mice enjoy losing weight

{{B}}第二篇{{/B}}

What can be inferred about the experiment?

A:Completely normally fed mice will not experience free radical production. B:Mice dieting in old age are not prone to diseases. C:Mice dieting all their lives live longer. D:Dieting doesn’t play any role in slowing down aging.

Clever genetic detective work may have found out the reason why a near-starvation diet prolongs the life of many animals.
Ronald Kahn at Harvard Medical School in Boston, US, and his colleagues have been able to extend the lifespan (寿命) of mice by 18 percent by blocking the rodent’s (啮齿动物) increase of fat in specific cells. This suggests that thinness—and not necessarily diet— promotes long life in "calorie (热量单位, 卡) restricted" animals.
"It’s very cool work, "says aging researcher Cynthia Kenyon of the University of California, San Francisco. "These mice eat all they want, lose weight and live longer. It’s like heaven."
Calorie restriction dramatically extends the lifespan of organisms as different as worms and rodents. Whether this works in humans is still unknown, partly because few people are willing to submit to such a strict diet.
But many researchers hope they will be able to trigger the same effect with a drug once they understand how less food leads to a longer life. One theory is that eating less reduces the increase of harmful things that can damage cells. But Kahn’s team wondered whether the animals simply benefit by becoming thin.
To find out, they used biology tricks to disrupt the insulin (胰岛素) receptor (受体) gene in lab mice—but only in their fat cells. "Since insulin is needed to help fat ceils store fat, these animals were protected against becoming fat," explains Kahn.
This slight genetic change in a single tissue had dramatic effects. By three months of age, Kahn’s modified mice had up to 70 percent less body fat than normal control mice, despite the fact that they ate 55 percent more food per gram of body weight.
In addition, their lifespan increased. The average control mouse lived 753 days, while the thin rodents averaged a lifespan of 887 days. After three years, all the control mice had died, but one-quarter of the modified rodents were still alive.
"That they get these effects by just manipulating the fat cells is controversial," says Leonard Guarente of the Massachusetts Institute of Technology, who studies calorie restriction and aging.
But Guarente says Kahn has yet to prove that the same effect is responsible for increased lifespan in calorie-restricted animals. "It might be the same effect or there might be two routes to long life," he points out, "and that would be very interesting./

What does the last sentence in the third paragraph imply（　）

A:People like to lose weight, but they do not like to eat less. B:People want to go to heaven,but they do not want to die. C:Mice will go to heaven if they lose weight. D:Mice enjoy losing weight.

Eat More, Weigh Less, Live Longer
Clever genetic detective work may have found out the reason why a near-starvation diet prolongs the life of many animals.
Ronald Kahn at Harvard Medical School in Boston, US, and his colleagues have been able to extend the lifespan (寿命) of mice by 18 per cent by blocking the rodent’s (啮齿动物) increase of fat in specific cells. This suggests that thinness—and not necessarily diet—promotes long life in "calorie (热量卡) restricted" animals.
"It’s very coal work," says aging researcher Cynthia Kenyon of the University of California, San Francisco. "These mice eat all they want, lose weight and live longer. It’s like heaven."
Calorie restriction .dramatically extends the lifespan of organisms as different as worms and rodents. Whether this works in humans is still unknown, partly because few people are willing to submit to such a strict diet.
But many researchers hope they will be able to trigger the same effect with a drug once they understand how less .food leads to a longer life. One theory is that eating less reduces the increase of harmful things that can damage cells. But kahn’s team wondered whether the animals simply benefit by becoming thin:
To find out, they used biology tricks to disrupt the insulin (胰岛素) receptor (受体) gene in lab mice—but only in their fat cells. "Since insulin is needed to help fat cells store fat, these animals were protected against becoming fat," explains Kahn.
This slight genetic change in a single tissue had dramatic effects. By three months of age, Kahn’s modified mice had up to 70 per cent less body fat than normal control mice, despite the fact that they ate 55 per cent more food per gram of body weight.
In addition, their lifespan increased. The average control mouse lived 753 days, while the thin rodents averaged a lifespan of 887 days. After three years, all the control mice had died, but one-quarter of the modified rodents were still alive.
"That they get these effects by just manipulating the fat cells is controversial," says Leonard Guarente of the Massachusetts Institute of Technology, who studies calorie restriction and aging..
But Guarente says Kahn has yet to prove that the same effect is responsible for increased lifespan in calorie-restricted animals. "It might be the same effect or there might be two routes to long life," he points out, "and that would be very interesting./

What does the last sentence in the third paragraph imply（　）.

A:People like to lose weight, but they do not like to eat less. B:People want to go to heaven, but they do not want to die. C:Mice will go to heaven if they lose weight. D:Mice enjoy losing weight.

Eat More, Weigh Less, Live Longer
Clever genetic detective work may have found out the reason why a near-starvation diet prolongs the life of many animals.
Ronald Kahn at Harvard Medical School in Boston, US, and his colleagues have been able to extend the lifespan (寿命) of mice by 18 per cent by blocking the rodent’s (啮齿动物) increase of fat in specific cells. This suggests that thinness—and not necessarily diet—promotes long life in "calorie (热量卡) restricted" animals.
"It’s very coal work," says aging researcher Cynthia Kenyon of the University of California, San Francisco. "These mice eat all they want, lose weight and live longer. It’s like heaven."
Calorie restriction .dramatically extends the lifespan of organisms as different as worms and rodents. Whether this works in humans is still unknown, partly because few people are willing to submit to such a strict diet.
But many researchers hope they will be able to trigger the same effect with a drug once they understand how less .food leads to a longer life. One theory is that eating less reduces the increase of harmful things that can damage cells. But kahn’s team wondered whether the animals simply benefit by becoming thin:
To find out, they used biology tricks to disrupt the insulin (胰岛素) receptor (受体) gene in lab mice—but only in their fat cells. "Since insulin is needed to help fat cells store fat, these animals were protected against becoming fat," explains Kahn.
This slight genetic change in a single tissue had dramatic effects. By three months of age, Kahn’s modified mice had up to 70 per cent less body fat than normal control mice, despite the fact that they ate 55 per cent more food per gram of body weight.
In addition, their lifespan increased. The average control mouse lived 753 days, while the thin rodents averaged a lifespan of 887 days. After three years, all the control mice had died, but one-quarter of the modified rodents were still alive.
"That they get these effects by just manipulating the fat cells is controversial," says Leonard Guarente of the Massachusetts Institute of Technology, who studies calorie restriction and aging..
But Guarente says Kahn has yet to prove that the same effect is responsible for increased lifespan in calorie-restricted animals. "It might be the same effect or there might be two routes to long life," he points out, "and that would be very interesting./

What does the last sentence in the third paragraph imply（）。

A:People like to lose weight, but they do not like to eat less. B:People want to go to heaven, but they do not want to die. C:Mice will go to heaven if they lose weight. D:Mice enjoy losing weight。

Clever genetic detective work may have found out the reason why a near starvation diet prolongs the life of many animals.
Ronald Kahn at Harvard Medical School in Boston, U.S., and his colleagues have been able to extend the lifespan of mice by 18 per cent by blocking the rodent’s increase of fat in specific cells. This suggests that thinness and hot necessarily diet promotes long life in "calorie restricted" animals.
"It’s very cool work." says aging researcher Cynthia Kenyon of the University of California, San Francisco. "These mice eat all they want, lose weight and live longer. It’s like heaven."
Calorie restriction dramatically extends the lifespan of organisms as different as worms and rodents. Whether this works in humans is still unknown, partly because few people are willing to submit to such a strict diet.
But many researchers hope they will be able to trigger the same effect with a drug once they understand how less food leads to a longer life. One theory is that eating less reduces the increase of harmful things that can damage cells. But Kahn’s team wondered whether the animals simply benefit by becoming thin.
To find out they used biology tricks to disrupt the insulin (胰岛素) receptor (受体) gene in lab mice but only in their fat cells. "Since insulin is needed to help fat cells store fat, these animals were protected against becoming fat," explains Kahn.
This slight genetic change in a single tissue had dramatic effects. By three months of age, Kahn’s modified mice had up to 70 percent less body fat than normal control mice, despite the fact that they ate 55 percent more food per gram of body weight.
In addition, their lifespan increased. The average control mouse lived 753 days, while the thin rodents averaged a lifespan of 887 days. After three years, all the control mice had died, but one-quarter of the modified rodents were still alive.
"That they get these effects by just manipulating the fat cells is controversial," says Leonard Guarente of the Massachusetts Institute of Technology, who studies calorie restriction and aging.
But Guarente says Kahn has yet to prove that the same effect is responsible for increased lifespan in calorie restricted animals. "It might be the same effect or there might be two routes to long life," he points out, "and that would be very interesting./
What does the last sentence in the third paragraph imply

A:People like to lose weight, but they do not like to eat less. B:People want to go to heaven but they do not want to die. C:Mice will go to heaven if they lose weight. D:Mice enjoy losing weight.

{{B}}第三篇{{/B}}

What does the last sentence in the third paragraph imply?

A:People like to lose weight, but they do not like to eat less. B:People want to go to heaven, but they do not want to die. C:Mice will go to heaven if they lose weight. D:Mice enjoy losing weight.