Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI 53706, USA.
J Exp Biol. 2013 Nov 1;216(Pt 21):4065-70. doi: 10.1242/jeb.088203. Epub 2013 Aug 2.
In situations of increased energy demand and food intake, animals can often acclimate within several days. The intestine generally responds to elevated digestive demand by increasing in size. However, there is likely a limit to how quickly the intestine can grow to meet the new demand. We investigated the immediate and longer-term changes to intestinal properties of the mouse when suddenly exposed to 4°C. We hypothesized that paracellular permeability to nutrients would increase as part of an immediate response to elevated absorptive demand. We measured absorption of l-arabinose, intestinal size and gene expression of several tight junction proteins (claudin-2, claudin-4, claudin-15 and ZO-1) at three time points: pre-exposure, and after 1 day and 2 weeks of cold exposure. Cold exposure increased food intake by 62% after 2 weeks but intake was not significantly increased after 1 day. Intestinal wet mass was elevated after 1 day and throughout the experiment. Absorption of arabinose rose by 20% after 1 day in the cold and was 33% higher after 2 weeks. Expression of claudin-2 increased after 1 day of cold exposure, but there were no changes in expression of any claudin genes when normalized to ZO-1 expression. Our results indicate that intestinal mass can respond rapidly to increased energy demand and that increased paracellular permeability is also part of that response. Increased paracellular permeability may be a consequence of enterocyte hyperplasia, resulting in more tight junctions across which molecules can absorb.
在能量需求和食物摄入增加的情况下，动物通常可以在几天内适应。肠道通常通过增加大小来应对消化需求的增加。然而，肠道的生长速度可能有一个极限，以满足新的需求。我们研究了小鼠突然暴露在 4°C 时肠道特性的即时和长期变化。我们假设，作为对吸收需求增加的即时反应的一部分，营养物质的旁细胞通透性会增加。我们测量了吸收 l-阿拉伯糖、肠道大小和几种紧密连接蛋白（claudin-2、claudin-4、claudin-15 和 ZO-1）的基因表达，在三个时间点进行测量：暴露前、暴露后 1 天和 2 周。2 周后，冷暴露使食物摄入量增加了 62%，但 1 天后摄入量没有明显增加。1 天后肠道湿重升高，整个实验过程中均升高。阿拉伯糖的吸收在冷暴露 1 天后增加了 20%，2 周后增加了 33%。冷暴露 1 天后 claudin-2 的表达增加，但 claudin 基因的表达在与 ZO-1 表达归一化后没有变化。我们的结果表明，肠道质量可以快速响应能量需求的增加，并且旁细胞通透性的增加也是该反应的一部分。增加的旁细胞通透性可能是肠细胞增生的结果，导致更多的紧密连接，分子可以通过这些连接吸收。
