Female tsetse flies undergo viviparous reproduction, generating one larva each gonotrophic cycle. Larval nourishment is provided by the mother in the form of milk secretions. The milk consists mostly of lipids during early larval development and shifts to a balanced combination of protein and lipids in the late larval instars. Provisioning of adequate lipids to the accessory gland is an indispensable process for tsetse fecundity. This work investigates the roles of Brummer lipase (Bmm) and the adipokinetic hormone (AKH)/adipokinetic hormone receptor (AKHR) systems on lipid metabolism and mobilization during lactation in tsetse. The contributions of each system were investigated by a knockdown approach utilizing siRNA injections. Starvation experiments revealed that silencing of either system results in prolonged female lifespan. Simultaneous suppression of bmm and akhr prolonged survival further than either individual knockdown. Knockdown of akhr and bmm transcript levels resulted in high levels of whole body lipids at death, indicating an inability to utilize lipid reserves during starvation. Silencing of bmm resulted in delayed oocyte development. Respective reductions in fecundity of 20 and 50% were observed upon knockdown of akhr and bmm, while simultaneous knockdown of both genes resulted in 80% reduction of larval production. Omission of one bloodmeal during larvigenesis (nutritional stress) after simultaneous knockdown led to almost complete suppression of larval production. This phenotype likely results from tsetse's inability to utilize lipid reserves as loss of both lipolysis systems leads to accumulation and retention of stored lipids during pregnancy. This shows that both Bmm lipolysis and AKH/AKHR signaling are critical for lipolysis required for milk production during tsetse pregnancy, and identifies the underlying mechanisms of lipid metabolism critical to tsetse lactation. The similarities in the lipid metabolic pathways and other aspects of milk production between tsetse and mammals indicate that this fly could be used as a novel model for lactation research.

中文翻译：

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采采蝇，Glossina morsitans 中泌乳基础的脂解分析。

雌性采采蝇进行胎生繁殖，每个生殖营养周期产生一只幼虫。幼虫的营养由母体以乳汁分泌物的形式提供。在幼虫发育早期，乳汁主要由脂质组成，并在幼虫发育后期转变为蛋白质和脂质的平衡组合。为附属腺体提供足够的脂质是采采蝇繁殖力不可或缺的过程。这项工作研究了 Brummer 脂肪酶 (Bmm) 和脂肪动力激素 (AKH)/脂肪动力激素受体 (AKHR) 系统对采采蝇哺乳期间脂质代谢和动员的作用。通过使用 siRNA 注射的击倒方法研究了每个系统的贡献。饥饿实验表明，任一系统的沉默都会导致女性寿命延长。同时抑制 bmm 和 akhr 比任何一种单独的敲低都能延长存活时间。akhr 和 bmm 转录水平的抑制导致死亡时全身脂质水平升高，表明在饥饿期间无法利用脂质储备。bmm 的沉默导致卵母细胞发育延迟。在击倒 akhr 和 bmm 后观察到繁殖力分别降低 20% 和 50%，而同时击倒这两个基因导致幼虫产量减少 80%。在同时敲低后在幼虫发生（营养应激）期间省略一种血粉几乎完全抑制了幼虫的产生。这种表型可能是由于采采蝇无法利用脂质储备，因为两种脂解系统的丧失导致怀孕期间储存的脂质的积累和保留。这表明 Bmm 脂解和 AKH/AKHR 信号对于采采蝇怀孕期间产奶所需的脂解至关重要，并确定了对采采蝇泌乳至关重要的脂质代谢的潜在机制。采采蝇与哺乳动物之间脂质代谢途径和产奶其他方面的相似性表明，这种苍蝇可用作哺乳研究的新模型。