避免母乳產(chǎn)生毒素的內(nèi)控奧秘(英漢對(duì)照)

牧童

Hidden Quality Control System Keeps Mothers from Producing Toxic Milk

Throughout human history, mother's milk has been regarded as the perfect food. Rich, nutritious and readily available, it is the drink of choice for tens of millions of human infants, not to mention all mammals from mice to whales.

But even mother's milk can turn toxic if the molecular pathways that govern its production are disrupted, according to a new study by Howard Hughes Medical Institute (HHMI) researchers at The Salk Institute for Biological Studies.

“It's one of those unexpected observations. It tells you the mother can transmit quite a bit more than nutrition through the milk.”
Ronald M. Evans

Writing in the August 2007 issue of the journal Genes & Development, a group led by HHMI investigator Ronald M. Evans reports that female mice that are deficient in the protein PPAR gamma produce toxic milk. The milk that had been nutritious instead causes inflammation, growth retardation and loss of hair in nursing mouse pups.

“We all think of milk as the ultimate food, the soul food for young animals,” said Evans. “The quality of that milk is also something that is genetically predetermined.”

In essence, the new finding reveals a genetic program for ensuring that mother's milk is the wonder food it is hailed to be: “We stumbled onto a hidden quality control system. Milk has to be a very clean product. It seems there is a whole process the body uses so that milk is scrubbed and doesn't have anything toxic in it.”

Evans said the finding was unanticipated, discovered when his group engineered mice to be deficient in PPAR gamma, a protein that helps regulate the body's sugar and fat stores. Mouse pups developed growth retardation and hair loss when they nursed on mothers who lacked the gene to produce PPAR gamma in blood cells and cells that line the interior of blood and lymph vessels.

“It's one of those unexpected observations,” Evans explained. “It tells you the mother can transmit quite a bit more than nutrition through the milk.”

Evans's group found they could reverse the toxic effects of the milk by letting the affected mouse pups nurse on a mother without the genetic variation in PPAR gamma.

Further studies showed that the mouse mothers with the PPAR-gamma deficiency produced milk with oxidized fatty acids, toxic substances that can prompt inflammation.

Evans and his colleagues showed that they could reverse the toxic effects of the milk by administering aspirin or other anti-inflammatory agents. “If you suppress the inflammation, the hair grows back,” said Evans.

PPARs are a widely studied family of nuclear receptors, proteins that are responsible for sensing hormones and other molecules. They work in concert with other proteins to switch genes on or off and are intimately connected to the cellular metabolism of carbohydrates, fats and proteins.

Although their discovery came as a surprise, Evans said it should have been obvious that there would be a mechanism in place to ensure the quality of milk.

“We should have realized there is something very special about it,” he said. “The reason we haven't heard about toxic milk is because there is a system that keeps it clean. It is logical and should have been anticipated.”

In Evans's view, PPAR gamma's role in ensuring the quality of mother's milk is likely to be a fundamental feature of evolution.

Lactating mothers, he noted, are not protected from inflammation, yet the milk they produce must be a pristine product: “Healthfulness in the body or products of the body is due to a (genetic) program, a process designed over the course of evolutionary history to maintain health.”

PPAR gamma's role in cleansing milk is “a very straightforward variation on how this system controls both lipid metabolism and inflammation. It's the secret of keeping them apart. That may be the reason the whole system exists,” Evans said.

In the human population, there are variants in the genetic program that governs PPAR gamma, which alters the fate of sugar and fat in the body. The system is already the target of anti-inflammatory drug therapy used to manage conditions such as diabetes.

Co-authors of the new Genes & Development article include Yihong Wan, Ling-Wa Chong and Chun-Li Zhang, all of The Salk Institute; and Alan Saghatelian and Benjamin F. Cravatt of The Scripps Research Institute.


譯文來(lái)自丁香園：
http://www.dxy.cn/bbs/post/view?bid=116&id=9801820&sty=1&tpg=1&age=0

避免母乳產(chǎn)生毒素的內(nèi)控奧秘


母乳由于其營(yíng)養(yǎng)成分豐富，營(yíng)養(yǎng)價(jià)值高以及容易取得而被認(rèn)為是完美的食物。然而最新研究表明如果調(diào)控乳汁分泌的分子通道被破壞，母乳也會(huì)具有毒性。

以休斯醫(yī)學(xué)研究院研究員Ronald M. Evans為首的研究小組在2007年8月份的《基因與發(fā)育》雜志上報(bào)道,過氧化物酶體增殖劑激活受體-gamma蛋白（PPAR gamma）缺陷的母鼠可產(chǎn)生有毒性的乳汁。

Evans研究小組發(fā)現(xiàn)用血細(xì)胞以及排列于血管與淋巴管內(nèi)部的細(xì)胞中產(chǎn)生PPAR gamma蛋白的基因缺失的母鼠乳汁喂養(yǎng)幼鼠時(shí)，可致幼鼠發(fā)生炎癥、生長(zhǎng)發(fā)育遲緩以及脫毛。用PPAR gamma未發(fā)生遺傳變異的母乳喂養(yǎng)上述受累的幼鼠時(shí)，乳汁的毒性作用可得到逆轉(zhuǎn)。進(jìn)一步研究顯示PPAR-gamma缺陷母鼠乳汁中含有可促使炎癥發(fā)生的氧化型脂肪酸和毒性物質(zhì)。使用阿司匹林或其它的抗炎藥物也可逆轉(zhuǎn)上述乳汁的毒性作用。

PPARs是細(xì)胞核受體中被深入研究的一個(gè)家族，細(xì)胞核受體是負(fù)責(zé)感應(yīng)激素和其它分子的蛋白。和其它蛋白一起調(diào)控基因的開放和關(guān)閉，與細(xì)胞內(nèi)糖、脂肪和蛋白質(zhì)的代謝密切相關(guān)。PPAR gamma是一種幫助調(diào)節(jié)體內(nèi)糖和脂肪儲(chǔ)備的蛋白。

Evans說(shuō)顯然這里存在著一個(gè)特定的機(jī)制用以保證乳汁的質(zhì)量。 “我們沒有聽說(shuō)過乳汁的毒性是因?yàn)榇嬖谥粋€(gè)特定的系統(tǒng)來(lái)使之保持清潔。這是合理的，也是可以預(yù)料的?！?br />
Evans認(rèn)為PPAR gamma用來(lái)保證母乳質(zhì)量這一作用可能是進(jìn)化的基本特征。

PPAR gamma是用來(lái)改變體內(nèi)的糖和脂肪的去向的，人類群體中調(diào)控PPAR gamma的遺傳程序設(shè)計(jì)存在著不同的變異。這一系統(tǒng)已經(jīng)成為用抗炎藥物療法來(lái)處理像糖尿病這類情況的靶標(biāo)。

wning

it is very informative.thank you so much for dilivering

sharplew

:tiaotiao: :sdsd: :sdsd: 無(wú)起步有

sharplew

好帖子，頂:hihi: :hihi: :hihi: :huahua: