Department of Animal Physiology, University of Bayreuth, 95440 Bayreuth, Germany.
Integr Comp Biol. 2009 Oct;49(4):380-92. doi: 10.1093/icb/icp019. Epub 2009 Jun 4.
Since all life processes depend on energy, the endocrine control of energy metabolism is one of the driving forces for the performance of an individual. Here, we review the literature on the key players in the endocrine regulation of energy homeostasis in insects, the adipokinetic hormones. These pleiotropic peptides not only control dynamic performance traits (flight, swimming, walking) but also regulatory performance traits (egg production, larval growth, and molting). Adipokinetic hormone is released into the hemolymph during intense muscular activity (flight) and also during apparently less energy-demanding locomotory activities, such as swimming and even walking, and, finally, activates the catabolic enzymes phosphorylase and/or triacylglycerol lipase that mobilize carbohydrates and/or lipids and proline, respectively. At the same time, anabolic processes such as the synthesis of protein, lipid, and glycogen are inhibited. Furthermore, adipokinetic hormones affect locomotory activity via neuromodulatory mechanisms that apparently employ biogenic amines. During oogenesis, it is thought that adipokinetic hormone performs similar tasks, because energetic substrates have to be mobilized and transported from the fat body to the ovaries in order to support oocyte growth. Inhibition of anabolic processes by exogenous adipokinetic hormone results in females that lay fewer and smaller eggs. Much less is known about the role of adipokinetic hormones during larval development and during molting but in this case energy homeostasis has to be tightly regulated as well: in general, during the early phase of a larval instar intake of food prevails and the energy stores of the fat body are established, whereas, prior to the molt, insects stop feeding and mobilize energy stores in the fat body, thereby fueling energy-demanding processes such as the formation of the new cuticle and the emergence from the old one. From the few data available to date, it is clear that adipokinetic hormones are involved in the regulation of these events in larvae.
由于所有生命过程都依赖于能量，因此内分泌对能量代谢的控制是个体表现的驱动力之一。在这里，我们回顾了关于昆虫能量稳态内分泌调节的关键因子——脂动激素的文献。这些多功能肽不仅控制动态性能特征（飞行、游泳、行走），还控制调节性能特征（产卵、幼虫生长和蜕皮）。脂动激素在剧烈的肌肉活动（飞行）期间以及在明显能量需求较低的运动活动期间（如游泳甚至行走）释放到血淋巴中，最终激活分解代谢酶磷酸化酶和/或三酰基甘油脂肪酶，分别动员碳水化合物和/或脂质以及脯氨酸。同时，蛋白质、脂质和糖原的合成等合成过程被抑制。此外，脂动激素通过神经调节机制影响运动活性，这些机制显然利用生物胺。在卵子发生期间，人们认为脂动激素执行类似的任务，因为必须动员和从脂肪体向卵巢运输能量底物，以支持卵母细胞生长。外源性脂动激素抑制合成代谢过程会导致产卵量减少和产卵个体变小。在幼虫发育和蜕皮期间，脂动激素的作用知之甚少，但在这种情况下，能量稳态也必须得到严格调节：一般来说，在幼虫的早期阶段，进食占主导地位，脂肪体的能量储存建立，而在蜕皮之前，昆虫停止进食并动员脂肪体的能量储存，从而为能量需求过程提供燃料，如新表皮的形成和从旧表皮中脱出。从目前为数不多的数据来看，脂动激素参与了幼虫这些事件的调节是明确的。
