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》
[00:00]In the latest issue of the Proceedings of the National Academy of Sciences,
[00:06]researchers report that a variant of a gene linked to very long life
[00:12]and small stature in animals may be linked to both in humans as well.
[00:18]Children of centenarians are more likely to have the genetic variant;
[00:23]they're also more likely to be lacking in the height department.
[00:27]In other words, short people may live longer.
[00:31]The study began with a group of Ashkenazi Jews, all of them over 95.
[00:38]Researchers asked them why they thought they had lived for so long.
[00:43]"We would get two answers. My mother was 102
[00:48]and my grandmother was 108-a strong family history",
[00:52]says one of the scientists, Nir Barzilai,
[00:55]director of the Institute for Aging Research
[00:59]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.
