University of Wisconsin-Madison, Department of Forest and Wildlife Ecology, Madison, WI 53706, United States.
University of Wisconsin-Madison, Department of Forest and Wildlife Ecology, Madison, WI 53706, United States.
Comp Biochem Physiol A Mol Integr Physiol. 2022 Sep;271:111243. doi: 10.1016/j.cbpa.2022.111243. Epub 2022 May 21.
According to the adaptive modulation hypothesis, digestive enzyme activities are matched to their respective dietary substrate level so that ingested nutrients are not wasted in excreta due to insufficient digestive capacity, and so membrane space or expenditures building/maintaining the intestinal hydrolytic machinery are not wasted when substrate levels are low. We tested predictions in juvenile northern bobwhites (Colinus virginianus) and juvenile and adult domestic chickens (Gallus gallus domesticus) by feeding them on diets varying in starch, protein, and lipid composition for 7-9 d (bobwhites) or 15 d (chickens). Birds were euthanized, intestinal tissue harvested, and enzyme activities measured in tissue homogenates from proximal, medial and distal small intestine. We found that (1) α-glucosidase (AG; maltase and sucrase) activities were induced by dietary starch in both juvenile and adult chickens but not in northern bobwhites; (2) aminopeptidase-N (APN) activities were induced by dietary protein in both bobwhites and juvenile but not adult chickens; (3) AG activities were suppressed by an increase in dietary lipid in both bobwhites and juvenile but not adult chickens; and (4) APN activities were not suppressed by high dietary lipid in any birds. We review findings from 35 analogous trials in 16 avian species. 100% of avian omnivores modulate at least one enzyme in response to change in dietary substrate level. AG induction by dietary carbohydrate occurs in more members of Galloanserae than in Neoaves, and all omnivorous members of Neoaves tested so far increase APN activity on high dietary protein, whereas fewer of the Galloanserae do.
根据适应性调制假说，消化酶的活性与各自的膳食底物水平相匹配，以避免由于消化能力不足而将摄入的营养物质浪费在粪便中，并且当底物水平较低时，不会浪费膜空间或用于构建/维持肠道水解机制的支出。我们通过在 7-9 天（鹌鹑）或 15 天（鸡）的时间内用不同淀粉、蛋白质和脂质组成的饮食喂养幼年北方鹌鹑（Colinus virginianus）和幼年及成年家鸡（Gallus gallus domesticus）来检验该假说。处死鸟类，采集肠组织，并在近端、中端和远端小肠组织匀浆中测量酶活性。我们发现：（1）α-葡萄糖苷酶（AG；麦芽糖酶和蔗糖酶）活性在幼年和成年鸡的饮食淀粉中被诱导，但在北方鹌鹑中没有；（2）氨肽酶-N（APN）活性在鹌鹑和幼年鸡的饮食蛋白质中被诱导，但在成年鸡中没有；（3）AG 活性在鹌鹑和幼年鸡的饮食脂质增加时被抑制，但在成年鸡中没有；（4）APN 活性在任何鸟类的高饮食脂质中都没有被抑制。我们回顾了 35 项在 16 种鸟类中进行的类似试验的结果。100%的杂食鸟类会根据饮食底物水平的变化来调节至少一种酶。饮食碳水化合物对 AG 的诱导在 Galloanserae 中比在 Neoaves 中更为常见，而且迄今为止，所有测试过的杂食性 Neoaves 鸟类都会在高蛋白质饮食中增加 APN 活性，而 Galloanserae 中则较少。
