狗狗也因肥胖而烦恼 | 经济学人

正文字数 750 words

Some Labradors have a predisposition to obesity
一些拉布拉多犬有肥胖的倾向

【Para.1】Much like their human owners, dogs are experiencing an obesity epidemic. One recent study of British pooches found that one in 14 is too pudgy, putting them at higher risk of conditions like arthritis, shortening their lifespan and making walks more of a drag. Certain breeds, like Labradors, are particularly prone to fatness. Purebred Labs are around 70% more likely to be overweight than mixed-breed mutts. A new study, published in the journal Science Advances, has identified one reason why—a genetic quirk makes some Labradors prone to obesity.
【第1段】就像它们的人类主人一样，狗正在经历肥胖症的流行。最近一项针对英国狗的研究发现，每 14 只狗中就有一只太胖了，这使它们患关节炎等疾病的风险更高，缩短了它们的寿命，并使步行更加拖累。某些品种，如拉布拉多犬，特别容易发胖。纯种实验室比混种犬超重的可能性高出约 70%。发表在《科学进展》（Science Advances）杂志上的一项新研究已经确定了一个原因——遗传怪癖使一些拉布拉多犬容易肥胖。

【Para.2】The study, led by Eleanor Raffan, a veterinary geneticist at the University of Cambridge, focused on a gene known as POMC, which is found in humans as well as dogs. In a previous study, published in 2016, Dr Raffan and her colleagues found that obese Labradors were much more likely than slimmer dogs to be missing a small section of DNA in the gene, a so-called deletion mutation. In the latest study the researchers set out to identify how this genetic variant, which is present in a quarter of Labs, might cause them to gain weight.
【第2段】这项研究由剑桥大学兽医遗传学家埃莉诺·拉凡（Eleanor Raffan）领导，重点研究一种名为POMC的基因，该基因在人类和狗中都有发现。在2016年发表的一项研究中，Raffan博士和她的同事们发现，肥胖的拉布拉多犬比苗条的狗更有可能在基因中缺少一小段DNA，即所谓的缺失突变。在最新的研究中，研究人员着手确定这种存在于四分之一实验室中的遗传变异如何导致他们体重增加。

【Para.3】Their first finding was that dogs with the mutation seemed to be hungrier than dogs without it. This conclusion rested on the results of a “sausage-in-a-box test”. Experimenters recorded the Labs’ reaction to a meaty treat that they could see and smell, but couldn’t eat. On average, dogs with the POMC mutation spent almost twice as long looking at, or—for whatever reason—playing with, the tantalising box than did those without.
【第3段】他们的第一个发现是，有突变的狗似乎比没有突变的狗更饿。这一结论基于“盒装香肠测试”的结果。实验者记录了实验室对一种他们可以看到和闻到但不能吃的肉食的反应。平均而言，具有POMC突变的狗花在看这个诱人盒子上的时间几乎是没有POMC突变的狗的两倍。

【Para.4】The POMC mutation seemed to boost how much the dogs wanted food, but not how much they liked it. Dogs with and without the mutation were just as likely to be put off their kibble if it had been slathered with lime juice. If the dogs were given the chance to eat unlimited food in one sitting, there were also no clear differences in how much they binged. The authors suggested that Labs with the mutation may be more inclined to seek out food in between meals, causing them to put on the pounds.
【第4段】POMC突变似乎增加了狗对食物的需求，但并没有增加它们对食物的喜爱程度。如果涂上酸橙汁，有和没有突变的狗都有可能被推迟吃粗磨食物。如果让狗有机会一次吃无限量的食物，那么它们暴饮暴食的程度也没有明显的差异。作者认为，具有突变的实验室可能更倾向于在两餐之间寻找食物，导致他们增加体重。

【Para.5】Not only did the mutation influence the dogs’ desire for food, it also slowed their metabolism. In another experiment the dogs were encouraged to sleep in a respiratory chamber, which measured the volume of oxygen and carbon dioxide breathed in and out. From this, the scientists calculated that Retrievers with the POMC mutation burned 25% fewer calories at rest than those without, indicating that the hungry dogs may need to stick to a particularly light diet in order to stay slim.
【第5段】这种突变不仅影响了狗对食物的渴望，还减缓了它们的新陈代谢。在另一项实验中，鼓励狗在呼吸室中睡觉，呼吸室测量吸入和呼出的氧气和二氧化碳的体积。据此，科学家们计算出，具有POMC突变的猎犬在休息时燃烧的卡路里比没有POMC突变的猎犬少25%，这表明饥饿的狗可能需要坚持特别清淡的饮食以保持苗条。

【Para.6】Many other factors are likely to influence obesity in dogs. The authors have only found the POMC deletion in Labradors and Flat-Coated Retrievers, despite testing for it in many other portly breeds. But in these dogs the mutation is probably here to stay, as selective breeding to eliminate it would require a huge reduction in an already limited gene pool. The scientists also suspect that the variant may make dogs easier to train—it is present in around three-quarters of Labrador assistance dogs.
【第6段】许多其他因素都可能影响狗的肥胖。作者只在拉布拉多犬和扁平猎犬中发现了POMC缺失，尽管在许多其他波特犬品种中对其进行了测试。但是在这些狗中，这种突变可能会继续存在，因为选择性育种以消除它需要大幅减少已经有限的基因库。科学家们还怀疑，这种变种可能使狗更容易训练——它存在于大约四分之三的拉布拉多辅助犬中。

【Para.7】Dr Raffan’s work also provides insights into the biology of POMC mutations, which are relevant for humans too. People with these rare mutations report extreme hunger and many become obese as children. Scientists investigating the effects of genes typically study rats and mice, but in the case of POMC there are important differences between the genes of rodents and other mammals. The authors identified a protein which is affected by POMC mutation in the Labradors, but is not present in mice. They think this overlooked protein may well be involved in human weight control too.
【第7段】Raffan博士的工作还为POMC突变的生物学提供了见解，这些突变也与人类有关。具有这些罕见突变的人报告说极度饥饿，许多人在儿童时期变得肥胖。研究基因影响的科学家通常研究大鼠和小鼠，但在POMC的情况下，啮齿动物和其他哺乳动物的基因之间存在重要差异。作者在拉布拉多犬中发现了一种受POMC突变影响的蛋白质，但在小鼠中不存在。他们认为这种被忽视的蛋白质很可能也与人类体重控制有关。

【Para.8】Medication targeting the faulty POMC pathway in humans has already been developed. In 2020, setmelanotide, a drug that mimics one of the proteins produced by POMC, was approved for use in humans. It is unclear whether it would work in dogs, and with a price tag of at least £240 in Britain ($330 in America) per daily dose, it is unlikely to be prescribed to even the most pampered pets anytime soon. “There are many healthy, happy Labs who have a POMC mutation,” explained Dr Raffan. For now, owners looking to keep their pets in shape will just need to hide the treats and resist those pleading, puppy-dog eyes.
【第8段】针对人类错误POMC通路的药物已经开发出来。2020 年，一种模仿 POMC 产生的一种蛋白质的药物 setmelanotide 被批准用于人类。目前尚不清楚它是否适用于狗，而且在英国，每日剂量的价格至少为240英镑（美国为330美元），即使是最受宠爱的宠物也不太可能很快开处方。“有许多健康、快乐的实验室都有POMC突变，”Raffan博士解释说。目前，希望保持宠物身材的主人只需要隐藏零食并抵制那些恳求的小狗眼睛。

【声明】：本文原文摘选自经济学人，原文版权归杂志所有，仅供个人学习交流使用。

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