The University of Sydney, New South Wales 2006, Australia.
Proc Biol Sci. 2010 Jun 7;277(1688):1751-9. doi: 10.1098/rspb.2009.2045. Epub 2010 Feb 3.
Failure to provision tissues with an appropriate balance of nutrients engenders fitness costs. Maintaining nutrient balance can be achieved by adjusting the selection and consumption of foods, but this may not be possible when the nutritional environment is limiting. Under such circumstances, rebalancing of an imbalanced nutrient intake requires post-ingestive mechanisms. The first stage at which such post-ingestive rebalancing might occur is within the gastrointestinal tract (GIT), by differential release of digestive enzymes-releasing less of those enzymes for nutrients present in excess while maintaining or boosting levels of enzymes for nutrients in deficit. Here, we use an insect herbivore, the locust, to show for the first time that such compensatory responses occur within the GIT. Furthermore, we show that differential release of proteases and carbohydrases in response to nutritional state translate into differential extraction of macronutrients from host plants. The prevailing view is that physiological and structural plasticity in the GIT serves to maximize the rate of nutrient gain in relation to costs of maintaining the GIT; our findings show that GIT plasticity is integral to the maintenance of nutrient balance.
如果组织没有获得适当平衡的营养物质，就会产生适应性代价。通过调整食物的选择和摄入，可以维持营养平衡，但当营养环境受到限制时，这可能是不可能的。在这种情况下，需要通过摄食后机制来重新平衡不平衡的营养摄入。这种摄食后再平衡可能发生的第一阶段是在胃肠道（GIT）中，通过释放消化酶的差异来实现——对于过量存在的营养素，释放较少的酶，同时维持或提高缺乏营养素的酶的水平。在这里，我们首次使用昆虫草食动物——蝗虫，证明这种补偿反应发生在 GIT 内。此外，我们还表明，对营养状态的响应而导致的蛋白酶和碳水化合物酶的差异释放，转化为从宿主植物中提取大量营养素的差异。目前的观点是，GIT 中的生理和结构可塑性有助于使与维持 GIT 相关的营养物质获取率最大化；我们的研究结果表明，GIT 可塑性是维持营养平衡的重要组成部分。
