对老鼠进行的实验表明如果某段基因发生了突变，那么身体发出的“停止进食”的信号就会被阻断�?/p>
发表在《自然医学》杂志上的这篇文章认为大脑对控制饮食的荷尔蒙反应会因此趋于紊乱�?/p>
乔治敦大学医学中心的研究者们希望他们的发现能够为控制体重提供新的途径�?/p>
有很多基因与肥胖联系在一起，其中之一——脑原性神经营养因子（BDNF�?mdash;—已经在动物和一些人体试验中被证实对肥胖起到了一定的作用�?/p>
然而，该医学中心的科学家们还不能对这种联系做出解释�?/p>
饱食反应
研究表明那些被实施了特定基因诱变的老鼠要比普通老鼠多吃80%的食物�?/p>
通常情况下，一顿饱餐之后，胰岛素和瘦蛋白等荷尔蒙会告知大脑停止进食。而在基因变异后的老鼠中研究人员却发现这条讯息没有从血液中的荷尔蒙被传导到大脑的正确部位�?/p>
其中一位研究者，徐宝吉（音译）教授说�?ldquo;如果BDNF基因出现问题，神经元就不能互相通信，胰岛素和瘦蛋白等信号就会被掐断，从而使进食不能得到抑制�?rdquo;
他说这项发现“能够提供一些新的思路来帮助大脑控制体�?rdquo;比如找到一�?ldquo;能模拟BDNF表达的药�?rdquo;�?/p>
研究基因与肥胖关系的剑桥大学Sadaf Farooqi教授告诉BBC�?ldquo;基因的作用比我们想象的要大得多，它一直被低估了。对于两个不同的人，他们体重差异�?0%�?0%是由基因决定的�?rdquo;
她说BDNF因子的完全紊乱已经被证实会造成严重肥胖。但是她也谨慎地表示这些研究�?ldquo;完全基于老鼠�?rdquo;，并且类似的基因突变在人类身�?ldquo;非常少见”�?/p>
#p#副标�?e#Mouse experiments suggested the body's message to "stop eating" was blocked if the animals had the mutation.
The study, published in Nature Medicine, said the brain's response to appetite hormones was being disrupted.
The Georgetown University Medical Center researchers hope their findings could lead to new ways to control weight.
Many genes have been linked to obesity, one of them - brain-derived neurotrophic factor gene - has been shown to play a role in putting on weight in animal and some human studies.
However, scientists at the Georgetown University Medical Center said the explanation for this link was unknown.
Overeating
In studies on mice which had been genetically modified to have the mutation, the mice consumed up to 80% more food than normal.
After a meal, hormones such as insulin and leptin should tell the brain that the body is full and should stop eating. The researchers showed that in the mutated mice the message was not being passed on from the hormones in the blood to the correct part of the brain.
One of the researchers Prof Baoji Xu said: "If there is a problem with the BDNF gene, neurons can't talk to each other, and the leptin and insulin signals are ineffective, and appetite is not modified."
He said the discovery "may open up novel strategies to help the brain control body weight" such as finding a "drug that can stimulate BDNF expression".
Prof Sadaf Farooqi, who studies the relationship between genes and obesity at the University of Cambridge, told the BBC: "Genes have a surprisingly large role, it's often underestimated. Between 40 and 70% of the difference in weight between two individuals is due to genetics."
She said completely disrupting the brain-derived neurotrophic factor gene had been shown to lead to severe obesity. However, she cautioned that the study was "entirely in mice" and the mutation was "very rare" in people.
