一本教会你“做对”题的6级阅读书 day7 passage2
Passage 2 Short Men Live Longer 122
矮个子更长寿 《新闻周刊》
In the latest issue of the Proceedings of the National Academy of Sciences,
researchers report that a variant of a gene linked to very long life
and small stature in animals may be linked to both in humans as well.
Children of centenarians are more likely to have the genetic variant;
they're also more likely to be lacking in the height department.
In other words, short people may live longer.
The study began with a group of Ashkenazi Jews, all of them over 95.
Researchers asked them why they thought they had lived for so long.
"We would get two answers. My mother was 102
and my grandmother was 108-a strong family history",
says one of the scientists, Nir Barzilai,
director of the Institute for Aging Research
at the Albert Einstein College of Medicine in New York City.
[01:04]As a population, this group was doing exactly
[01:08]what we tell our patients not to do." Clearly, then,
[01:13]for the centenarians, the secret to long life wasn't lifestyle
[01:18]it was being born with the right genes.
[01:22]Barzilai was especially interested in the so-called "Methuselah" gene,
[01:27]which has been linked to small size and long life in the lab.
[01:33]By tinkering with the gene,
[01:35]scientists can make roundworms live 30 to 50 percent longer than
[01:40]they normally would. The worms also end up being smaller,
[01:45]because their bodies process less of a hormone called IGF-1,
[01:51]which encourages growth. A similar link has shown up mammals.
[01:56]The bottom line: more IGF-1 means a bigger body and a smaller lifespan.
[02:04]Barzilai thought his centenarians might have a Methuselah mutation
[02:09]that was tamping down their bodies' responsiveness to IGF-1.
[02:14]Sure enough, he found that in a few of them
[02:18]a variant of the Methuselah gene seemed to be doing just that.
[02:23]The subjects had plenty of the hormone, but they weren't reacting to it.
[02:29]They were, of course, long-lived. They were also short-and had always been,
[02:36]even in their prime, before age began to shrink their bones.
[02:41]The reason for both traits, he reasoned,
[02:44]might be their inefficiency in using IGF-1.
[02:49]So then Barzilai and his colleagues turned to the centenarians' children.
[02:55]This group too had an unusual variety of mutations
[02:59]that affected the IGF-1 pathway-they had high levels of the hormone
[03:06]but didn't seem to be processing it normally.
[03:09]The cellular receptors that take instructions from the hormone
[03:14]were basically hard of hearing;
[03:17]the subjects' bodies had turned up the volume by producing more of the hormone,
[03:23]but to no effect. Their levels of IGF-1 were much higher than a control group's,
[03:31]probably because their bodies were trying to compensate
[03:35]for the faulty receptors that weren't using it properly.
[03:40]There was only one more thing to measure: their height.
[03:44]Indeed, they were smaller than average,
[03:47]about an inch shorter than a control group
[03:49]with relatively normal IGF-1 function.