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别小看肝脏,有时候它比你的大脑更了解你

更新时间:2017-6-15 18:28:37 来源:纽约时报中文网 作者:佚名

The Liver: A ‘Blob’ That Runs the Body
别小看肝脏,有时候它比你的大脑更了解你

To the Mesopotamians, the liver was the body’s premier organ, the seat of the human soul and emotions. The ancient Greeks linked the liver to pleasure: The words hepatic and hedonic are thought to share the same root.

对美索不达米亚人来说,肝脏是身体的首要器官,是人类灵魂和情感的所在。古希腊人将肝脏与快乐联系在一起:肝脏的(hepatic)和快乐的(hedonic)这两个词被认为是同源的。

The Elizabethans referred to their monarch not as the head of state but as its liver, and woe to any people saddled with a lily-livered leader, whose bloodless cowardice would surely prove their undoing.

伊丽莎白一世时代,英国人提到君主的时候不称元首,而称国家的肝脏,如果一个领导人是百合肝脏,人民就倒了霉,因为领导者的懦弱注定会给民众带来祸患。

Yet even the most ardent liverati of history may have underestimated the scope and complexity of the organ. Its powers are so profound that the old toss-away line, “What am I, chopped liver?” can be seen as a kind of humblebrag.

然而,就算是历史上最热烈的肝脏专家,可能也未充分意识到这个器官的作用范围和复杂性。它能力之强大,哪怕“我是什么,被切碎的肝脏(意思是无足轻重的事物——译注)?”这句老话可以被视为表面谦虚,实则自夸。

After all, a healthy liver is the one organ in the adult body that, if chopped down to a fraction of its initial size, will rapidly regenerate and perform as if brand-new. Which is a lucky thing, for the liver’s to-do list is second only to that of the brain and numbers well over 300 items, including systematically reworking the food we eat into usable building blocks for our cells; neutralizing the many potentially harmful substances that we incidentally or deliberately ingest; generating a vast pharmacopoeia of hormones, enzymes, clotting factors and immune molecules; controlling blood chemistry; and really, we are just getting started.

毕竟,成年人体内的健康肝脏是这样的:被切碎到其初始尺寸的一小部分,也会快速再生,然后像全新肝脏一样发挥作用。这是一件幸事,肝脏要做的事情超过300种,仅次于大脑,比如肝脏有条不紊地将我们吃的食物重新加工成细胞成长的原料;中和我们偶然或故意摄入的多种可能有害的物质;产生多种激素、酶、凝血因子和免疫分子;控制血液化学成分;真的,这只是略举几例而已。

“We have mechanical ventilators to breathe for you if your lungs fail, dialysis machines if your kidneys fail, and the heart is mostly just a pump, so we have an artificial heart,” said Dr. Anna Lok, president of the American Association for the Study of Liver Diseases and director of clinical hepatology at the University of Michigan.

美国肝病研究协会(American Association for the Study of Liver Diseases)会长、密歇根大学肝病研究与临床肝病学主任安娜·洛克(Anna Lok)博士说:“如果你的肺部有问题,我们有呼吸机帮你呼吸;如果你的肾脏有问题,我们有透析机;心脏主要就是一个泵,所以可以使用人造心脏。”

“But if your liver fails, there’s no machine to replace all its different functions, and the best you can hope for is a transplant.”

“但如果你的肝脏出了问题,没有机器可以完全替代它,你就只能指望移植。”

And while scientists admit it hardly seems possible, the closer they look, the longer the liver’s inventory of talents and tasks becomes.

科学家承认,越是详细研究,肝脏的作用和功能清单就越长——怎么会这样。

In one recent study, researchers were astonished to discover that the liver grows and shrinks by up to 40 percent every 24 hours, while the organs around it barely budge.

在最近的一项研究中,研究人员惊奇地发现,肝脏每24小时最高可膨胀和收缩40%,而其周围的器官几乎纹丝不动。

Others have found that signals from the liver may help dictate our dietary choices, particularly our cravings for sweets, like a ripe peach or a tall glass of Newman’s Own Virgin Limeade — which our local supermarket chain has, to our personal devastation, suddenly stopped selling, so please, liver, get a grip.

还有些人觉得肝脏发出的信号可能会帮助决定我们的饮食选择,特别是我们对甜食的渴望,比如一个成熟的桃子,或一大杯纽曼牌初榨青柠果汁——如果超市连锁店让人崩溃,突然停止销售它们,那么我们就务必要让肝脏稳住。

Scientists have also discovered that hepatocytes, the metabolically active cells that constitute 80 percent of the liver, possess traits not seen in any other normal cells of the body. For example, whereas most cells have two sets of chromosomes — two sets of genetic instructions on how a cell should behave — hepatocytes can enfold and deftly manipulate up to eight sets of chromosomes, and all without falling apart or turning cancerous.

科学家们也发现,构成肝脏80%的代谢活性细胞,也就是肝细胞,具有人体内任何其他正常细胞没有的特征。例如,虽然大多数细胞都有两组染色体——两组关于细胞应如何行为的遗传指令——肝细胞却可以拥有最多八组染色体,并巧妙地对其施以控制,而且都不会分崩离析或转化为癌变。

That sort of composed chromosomal excess, said Dr. Markus Grompe, who studies the phenomenon at Oregon Health and Science University, is “superunique,” and most likely helps account for the liver’s regenerative prowess.

俄勒冈卫生科技大学(Oregon Health and Science University)的马库斯·葛鲁普(Markus Grompe)博士对这种沉着冷静的染色体过量现象进行了研究,他说该现象是“超级独一无二的”,很可能有助于解释肝脏的再生能力。

Scientists hope that the new insights into liver development and performance will yield novel therapies for the more than 100 disorders that afflict the organ, many of which are on the rise worldwide, in concert with soaring rates of obesity and diabetes.

科学家希望,对于肝脏发育和功能的新洞见将为100多种与该器官相关的疾病带来新疗法,其中很多疾病在全球范围内呈上升趋势,与肥胖和糖尿病患病率的飙升相吻合。

“It’s a funny thing,” said Valerie Gouon-Evans, a liver specialist at the Mount Sinai School of Medicine. “The liver is not a very sexy organ. It doesn’t look important. It just looks like a big blob.

“这很有趣。”西奈山医学院(Mount Sinai School of Medicine)的肝脏专家瓦莱丽·古文-埃文斯(Valerie Gouon-Evans)说:“肝脏不是一个很性感的器官。看起来不怎么重要。它看起来不过是一大团难以名状的东西。”

“But it is quietly vital, the control tower of the body,” and the hepatocytes that it is composed of “are astonishing.”

“但它静默而至关重要,它是身体的控制塔”,组成它的肝细胞“很惊人”。

The liver is our largest internal organ, weighing 3 1/2 pounds and measuring 6 inches long. The reddish-brown mass of four unevenly sized lobes sprawls like a beached sea lion across the upper right side of the abdominal cavity, beneath the diaphragm and atop the stomach.

肝脏是我们最大的内脏器官,重3.5磅(约合1.6公斤),长6英寸(约合15厘米)。由四个大小不均匀的部分组成,呈红褐色,像匍匐的海狮一样,位于人体腹腔右上方、隔膜下方和胃的上方。

The organ is always flush with blood, holding about 13 percent of the body’s supply at any given time. Many of the liver’s unusual features are linked to its intimate association with blood.

因为血液的缘故,这个器官总是呈现红色,每时每刻,它都拥有身体血液供应的13%。肝脏很多不寻常的特征都与它跟血液的紧密联系相关。

During fetal development, blood cells are born in the liver, and though that task later migrates to the bone marrow, the liver never loses its taste for the bodywide biochemical gossip that only the circulatory system can bring.

在胎儿的发育过程中,血细胞是在肝脏中产生的,虽然这个任务后来转移到了骨髓,但对于只有循环系统可以提供的全身生化信息,肝脏从来没有丧失过兴致。

Most organs have a single source of blood. The liver alone has two blood supplies, the hepatic artery conveying oxygen-rich blood from the heart and the hepatic portal vein dropping off blood drained from the intestines and spleen. That portal blood delivers semi-processed foodstuffs in need of hepatic massaging, conversion, detoxification, storage, secretion and elimination.

大多数器官都有单一的血供来源,而肝脏有两个。肝动脉输送的是来自心脏的富氧血液,而肝门静脉回收来自肠和脾的血液。这种门静脉血液传输的是需要肝脏按摩、转换、解毒、储存、分泌和淘汰的半加工食品。

“Everything you put in your mouth must go through the liver before it does anything useful elsewhere in the body,” Lok said.

“你吃到嘴里的东西都必须经过肝脏,才能为身体的其他部位带来好处,”洛克说。

As the master sampler of circulating blood, the liver keeps track of the body’s moment-to-moment energy demands, releasing glucose as needed from its stash of stored glycogen, along with any vitamins, minerals, lipids, amino acids or other micronutrients that might be required.

作为循环血液的取样能手,肝脏追踪着身体时时刻刻的能量需求,从自身储存的糖原里按需释放葡萄糖,还有各种维生素、矿物质、脂质、氨基酸或其他可能需要的微量营养素。

New research suggests the liver may take a proactive, as well as a reactive, role in the control of appetite and food choice.

有新研究显示,肝脏可能在控制胃口和食物选择上扮演着一种积极主动且容易引起反应的角色。

“It makes sense that the liver could be a nexus of metabolic control,” Gillum said. “At some level it knows more than the brain does about energy availability, and whether you’re eating too many pears.”

“肝脏成为新陈代谢的中心是有道理的,”吉勒姆说。“从某种程度上讲,在有关可用能量的信息,以及你是否吃梨吃多了的问题上,它知道的比大脑还多。”

The liver also keeps track of time. In a recent issue of the journal Cell, Ulrich Schibler of the University of Geneva and his colleagues described their studies of the oscillating liver, and how it swells and shrinks each day, depending on an animal’s normal circadian rhythms and feeding schedule.

肝脏也会追踪时间变化。在最近一期的《细胞》(Cell)杂志上,日内瓦大学(University of Geneva)的乌尔里克·希布勒(Ulrich Schibler)及同事描述了他们对肝脏收缩所做的研究,提到它每天如何随动物的正常生理节律和进食规律膨胀与收缩。

The researchers found that in mice, which normally eat at night and sleep during the day, the size of the liver expands by nearly half after dark and then retrenches come daylight. The scientists also determined the cause of the changing dimensions.

研究人员发现,通常为夜间进食、白天睡觉的小鼠的肝脏会在天黑后会膨胀近一半,然后又在天亮时缩回去。科学家也确定了出现这种收缩幅度的原因。

“We wanted to know, is it just extra water or glycogen?” Schibler said. “Because that would be boring.”

“我们想知道,只是额外摄入的水或糖元吗?”希布勒说。“因为那样就没意思了。”

It was not boring. “The total gemish, the total soup of the liver turns out to be different,” he said. Protein production in mouse hepatocytes rises sharply at night, followed by equivalent protein destruction during the day.

情况并非如此。“结果证明,所有的混合物,肝脏中容纳的所有东西都是有变化的,”他说。小鼠肝细胞中的蛋白质产量在夜间会剧增,到了白天又会出现同等程度的蛋白质破坏。

Evidence suggests that a similar extravaganza of protein creation and destruction occurs in the human liver, too, but the timing is flipped to match our largely diurnal pattern.

有证据显示,人的肝脏中也存在类似的蛋白质生产激增与破坏的过程,只不过时间与之相反,以适应我们大多数人日间活动的规律。

The researchers do not yet know why the liver oscillates, but Schibler suggested it is part of the organ’s fastidious maintenance program.

研究人员还不知道为什么肝脏会收缩,但希布勒表示,那是这种器官一丝不苟的程序维护工作的一部分。

“The liver gets a lot of bad stuff coming through,” he said. “If you damage some of its components, you need to replace them.” By having a rhythm to that replacement, he said, “you keep the liver in a good state.”

“肝脏中有大量的坏东西要通过,”他说。“如果有部分受损,就需要替换。”但如果形成了一种有规律的替换,他说,“就能让肝脏一直处在良好的状态。”

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