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标题: 美科学家发现果蝇肠道干细胞是其适应环境食物变化的关键 [打印本页]

作者: naturalkillerce 时间: 2011-10-28 23:12 标题: 美科学家发现果蝇肠道干细胞是其适应环境食物变化的关键

本帖最后由 naturalkillerce 于 2011-10-29 08:38 编辑

美科学家发现果蝇肠道干细胞通过增大肠道大小对食物做出反应
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局部释放的胰岛素激活肠道干细胞产生更多的肠道细胞和干细胞

naturalkillerce导语：看完后，觉得蛮有意思的。来自美国加州大学伯克利分校的研究人员在5年之前在果蝇肠道令人吃惊地发现干细胞，如今又发现果蝇进食时，其肠道在局部分泌它们自己的胰岛素，而分泌的胰岛素刺激肠道干细胞分裂并且产生更多的肠道细胞，而且肠道干细胞更加频繁地进行对称性分裂，更加有效地扩增细胞总数，从而增大肠道大小。然而当食物缺乏时，肠道大小减小。这一切就表明成体干细胞是果蝇适应环境变化的关键，能够根据不同的环境条件，主动地调整肠道大小来适应这些不同环境条件。由于由于果蝇和人存在很多相似性，这一发现可能是理解人类器官如何适应环境变化的关键。现编译如下：9 I6 H' r' \, M) u% c
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研究背景：
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背景之一：当前人们一直认为，一旦胚胎干细胞(embryonic stem cells, ESCs)发育为成体干细胞，它们就安静地呆在我们的组织里，替换死亡或受损的细胞，除此之外，它们做其他事情。/ m# {) U( h0 v% I3 P/ [: Z
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背景之二：很多组织在使用时增长或收缩，这其中就包括肌肉、肝脏和肠道。比如，由于癌症或损伤，通过手术移除一部分人肠道后，人肠道再次增长，而冬眠的动物在冬季时，它们的肠道收缩到正常大小的三分之一。
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背景之三：动物使用的一种策略来处理环境的变化以便它们的器官系统能够适应眼前的环境。然而，这种器官适应性如何精确发生长期以来一直是一个谜，特别是在成年动物中，因为它们不再生增长。

研究成果：
在5年之前在果蝇肠道令人吃惊地发现干细胞后，研究人员就决定研究成体干细胞在正常的肠道生长中所起的作用，以便期待发现它们在类似我们的脊椎动物中发挥作用的线索。

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果蝇中肠(midgut)中的细胞。这些肠道细胞用红色描出轮廓，有大的蓝色细胞核。肠道干细胞非常小，用绿色表示，它们的细胞核不可见。

如今，研究人员在2011年10月28日那期Cel杂志上发表了一项新的研究。在该研究中，来自美国加州大学伯克利分校的研究人员发现在果蝇中，肠道干细胞(intestinal stem cells)对增加的食物摄取做出反应产生更多的肠道细胞，只要食物一直保持在肠道流动，就能扩大肠道的大小。当果蝇开始吃时，肠道干细胞变得过于活跃，肠道扩大。四天之后，肠道比以前增大四倍，但是当食物拿走后，肠道减小。就像人类和其他哺乳动物一样，果蝇肠道分泌它自己的胰岛素。在果蝇中，肠道胰岛素似乎是使得干细胞加大肠道的信号。

研究人员发现，当果蝇进食时，它们的肠道局部分泌胰岛素，而分泌的胰岛素刺激肠道干细胞分裂并且产生更多的肠道细胞。研究人员对果蝇能够分泌它们自己的胰岛素感到非常吃惊，当果蝇进食后不久，肠道胰岛素达到高峰并且直接与肠道干细胞发生信号交流，这样肠道就能够控制自己的适应性。! G% ]& J2 M _0 P, M" g3 @7 N

肠道干细胞或发生不对称性分裂产生一个干细胞和一个肠道细胞，或者发生对称性分裂产生两个干细胞。研究人员发现，当果蝇进食时，相对于不对称性分裂，肠道干细胞更加频繁地进行对称性分裂，是一种更加有效地扩增细胞总数的方法。

研究意义：5 o4 ?9 E7 v% {) x8 g; |9 o# ]
意义之一：在这项研究中，证实成体干细胞对身体和环境的变化做出反应能够重新塑造器官，这一发现可能对糖尿病能够和肥胖带来启示。
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意义之二：由于果蝇和人存在很多相似性，这一发现可能是理解人类器官如何适应环境变化的关键。. T% t0 K- I! f+ E/ s( k% s+ S) C+ E
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意义之三：研究人员认为，成体干细胞是适应环境变化的关键。从生理适应角度来看，肠道这种适应性调整大小言讲得通，因为维持肠壁大小在新陈代谢上是昂贵的，要消耗身体高达30%的能源。当食物稀缺时，最小化肠道大小，而当食物充足时，增大肠道大小最大化消化能力，因此通过干细胞适应性调整肠道大小有助于动物在不断变化的环境中存活下来。* H, _: W( u6 t" c
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原文信息：
Altered Modes of Stem Cell Division Drive Adaptive Intestinal Growth* M! }; A# q6 e) _# K' e& e( h
Lucy Erin O'Brien, Sarah S. Soliman, Xinghua Li, David Bilder
Cell, Volume 147, Issue 3, 603-614, 28 October 2011
本论坛帖子上这期Cell杂志，具体见：- m3 E( R2 ]. b; h9 `
《细胞》[Cell]11年10月28日出版pdf全文：http://www.stemcell8.cn/thread-48122-1-1.html，是由zorro提供的，在此先感谢zorro一下。

作者: naturalkillerce 时间: 2011-10-28 23:15

回复 naturalkillerce 的帖子% p. [3 c2 z5 X

Intestinal stem cells respond to food by supersizing the gut
Locally released insulin activates stem cells to produce more gut and stem cells
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A new study from University of California, Berkeley, researchers demonstrates that adult stem cells can reshape our organs in response to changes in the body and the environment, a finding that could have implications for diabetes and obesity.5 B+ g; X2 @# T# X+ h4 M- M
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Current thinking has been that, once embryonic stem cells mature into adult stem cells, they sit quietly in our tissues, replacing cells that die or are injured but doing little else.% N- b0 }1 N8 Z) z" T; I
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But in working with fruit flies, the researchers found that intestinal stem cells responded to increased food intake by producing more intestinal cells, expanding the size of the intestines as long as the food keeps flowing.+ ?+ [4 F9 L$ h

"When flies start to eat, the intestinal stem cells go into overdrive, and the gut expands," said UC Berkeley post-doctoral fellow Lucy O'Brien. "Four days later, the gut is four times bigger than before, but when food is taken away, the gut slims down."
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Just as in humans and other mammals, O'Brien added, the fly intestine secretes its own insulin. In flies, intestinal insulin seems to be the signal that makes stem cells "supersize the gut."

"Because of the many similarities between the fruit fly and the human, the discovery may hold a key to understanding how human organs adapt to environmental change," said David Bilder, UC-Berkeley associate professor of molecular and cell biology.& P* L& l9 O+ e- ?  f' B5 W, G1 ?

The research will be published in the Oct. 28 issue of the journal Cell.

Stem cells key to adaptability
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Many tissues grow or shrink with usage, including muscle, liver and intestine. Human intestines, for example, regrow after portions have been surgically removed because of cancer or injury, and hibernating animals see their intestines shrink to one-third their normal size during winter.

"One strategy animals use to deal with environmental variability is to tune the workings of their organ systems to match the conditions at hand," O'Brien said. "How exactly this 'organ adaptation' happens, particularly in adult animals that are no longer growing, has long been a mystery."
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Following the surprising discovery of stem cells in the intestines of fruit flies five years ago, O'Brien and Bilder decided to investigate the role of adult stem cells in normal intestinal growth in hopes of finding clues to their role in vertebrates like us.6 o4 e9 R. s8 a1 i+ T9 D8 O
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"I looked at stained stem cells in the fruit fly intestine, and they are studded throughout like jewels. The tissues were so beautiful, I knew I had to study them," O'Brien said.' V7 w: r. L5 R) L9 l

O'Brien, Bilder and their colleagues discovered that when fruit flies feed, their intestines secrete insulin locally, which stimulates intestinal stem cells to divide and produce more intestinal cells.

"The real surprise was that the fruit fly intestine is capable of secreting its own insulin," BIlder said. "This intestinal insulin spikes immediately after feeding and talks directly to stem cells, so the intestine controls its own adaptation."
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Stem cells can divide either asymmetrically, producing one stem cell and one intestinal cell, or symmetrically, producing two stem cells. The team found that, in response to food, intestinal stem cells underwent symmetric division more frequently than asymmetric division, which had the effect of maintaining the proportion of stem cells to intestinal cells, and is a more efficient way of ramping up the total number of cells, O'Brien said.

"Adaptive resizing of the intestine makes sense from the standpoint of physiological fitness," she said. "Upkeep of the intestinal lining is metabolically expensive, consuming up to 30 percent of the body's energy resources. By minimizing intestinal size when food is scarce, and maximizing digestive capacity when food is abundant, adaptive intestinal resizing by stem cells helps animals survive in constantly changing environments."

作者: hany2007 时间: 2011-10-29 03:22

那位大爷把全文发上来啊，太饥渴了！

作者: naturalkillerce 时间: 2011-10-29 08:09

回复 hany2007 的帖子
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Altered Modes of Stem Cell Division Drive Adaptive Intestinal Growth" @* `" _) b7 f5 I( ]1 s( Q$ l; q# ?7 R
Cell, Volume 147, Issue 3, 603-614, 28 October 2011
论坛上有这期Cell杂志的，自己去动手下载一下，地址为：
http://www.stemcell8.cn/thread-48122-1-1.html

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