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  3. Fat: what is it good for? Absolutely nothing, or so you might think. But obesity seems to protect mice against a fatal form of m

Fat: what is it good for? Absolutely nothing, or so you might think. But obesity seems to protect mice against a fatal form of m

admin2015-12-23  96
问题     Fat: what is it good for? Absolutely nothing, or so you might think. But obesity seems to protect mice against a fatal form of malaria—cerebral malaria. Working out how it has this effect might lead to new treatments for people.
    Although obesity is now on the rise in the developing world, it has traditionally been seen as a malaise of the rich. In contrast, malaria tends to be regarded as a disease of the poor, so few people have studied how the two conditions affect each other. In mice meanwhile, there are signs that diabetes, which often affects obese people, might offer some protectioa against malaria.
    To find out more about how obesity affects malaria in mice, Vincent Robert at the Institute for Development Research(IRD)in Paris, France, and colleagues injected 14 obese and 14 non-obese mice with the malaria parasite Plasmodium berghei. After six days, eight of the non-obese mice died from cerebral malaria, which causes coma and death in humans, and the rest died about two weeks later from severe anemia because the parasite had destroyed their red blood cells. In contrast, none of the obese mice showed signs of cerebral malaria. Although they all eventually succumbed to severe anemia and died 18 to 25 days after infection, anemia can be treated—so obesity did seem to offer mice some useful protection.
    Exactly how the obese mice resist malaria is not clear, says Delphine Depoix from the Museum of Natural History in Paris, but there are several possibilities. One clue lies in a mutation in the gene coding for the leptin, a hormone produced by fat cells, which makes the mice obese, but also controls the immune response. Previous research has shown that obese mice with the leptin mutation often react to infections with a "Th2" rather man "Thl" response. As Thl in mice is thought to trigger the inflammation mat helps cerebral malaria to kill its victims, Depoix speculates mat me Th2 response might be protecting me obese mice. Another possible explanation is that the abnormally high blood sugar associated with obesity in both mice and people "might compensate" for the low blood sugar caused by severe malaria, says Depoix, allowing me mice to better cope with parasite infection.
    Andrew Prentice of the London School of Hygiene and Tropical Medicine says that figuring out how me mice resist malaria will be crucial to developing new treatments for people with malaria. His colleague Christopher Whitty warns that any insights drawn from these results are preliminary: "Mouse models are always useful in raising hypotheses but cannot settle them as far as cerebral malaria is concerned."
Few people have conducted research on the relations between malaria and obesity because
选项 A、more and more people suffer from obesity in me developing world.
B、only a small number of the rich suffer from malaria.
C、both malaria and obesity are not prevalent in the world.
D、they were seen as the disease of the poor and of the rich respectively.
答案D
解析 事实细节题。考查因果细节。第二段讲到由于两种疾病被看成两个不同群体(富人与穷人)所特有的疾病，所以很少有人关注肥胖与疟疾之间的联系，故D项正确。A项并非原因，仅是一个现象；B项并非原因，且only a small number是对原文内容的过度引申；C项not prevalent与文意“肥胖呈上升趋势”相悖，且与主干不构成因果关系。
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