Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Brazil.
Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030, USA.
Biochim Biophys Acta Mol Cell Biol Lipids. 2021 Feb;1866(2):158851. doi: 10.1016/j.bbalip.2020.158851. Epub 2020 Nov 4.
Rhodnius prolixus, a vector of Chagas disease, is a hematophagous insect that feeds exclusively on blood. Each blood meal is digested within the first fourteen days after feeding, providing substrates for lipid synthesis for storage and egg production. These events are precisely regulated and emerging evidence points to a key function of insulin-like peptides (ILPs) in this control. Here we investigated the role of insulin receptor in the regulation of nutrient metabolism in fed adult females. The expression of insulin receptor (RhoprIR) gene was determined in adult organs, and it was highest in ovaries and previtellogenic follicles. We generated insects with RNAi-mediated knockdown of RhoprIR to address the physiological role of this receptor. RhoprIR deficiency improved longevity and reduced triacylglycerol storage in the fat body, whereas blood digestion remained unchanged for seven days after blood meal. The lower lipid content was attributable to decreased de novo lipogenesis as well as reduced incorporation of hemolymph-derived fatty acids into newly synthesized lipids within this organ. Consistent with that, fat bodies from RhoprIR-deficient insects exhibited decreased gene expression levels of lipophorin receptor (RhoprLpR), glycerol-3-phosphate acyltransferase 1 and 4 (RhoprGpat1 and RhoprGpat4), and carnitine palmitoyltransferase 1 (RhoprCpt1). Although hemolymph lipid profile was not affected by RhoprIR disruption, the concentration of circulating vitellogenin was increased. In line with these changes, RhoprIR-deficient females exhibited smaller ovaries and a marked reduction in oviposition. Taken together, these findings support a key role of insulin receptor in nutrient homeostasis, lipid synthesis and egg production following a blood meal.
吸血的丽蝇 R. prolixus 是恰加斯病的传播媒介，它只以血液为食。每次吸血后，在进食后的前 14 天内，血液就会被消化，为脂质合成提供了储存和产卵的底物。这些事件受到精确调控，新出现的证据表明胰岛素样肽 (ILPs) 在这种控制中起着关键作用。在这里，我们研究了胰岛素受体在进食成年雌性昆虫营养代谢调节中的作用。在成年器官中测定了胰岛素受体 (RhoprIR) 基因的表达，其在卵巢和前卵母细胞滤泡中表达最高。我们利用 RNAi 介导的 RhoprIR 敲低技术生成昆虫，以解决该受体的生理作用。RhoprIR 缺乏可延长寿命并减少脂肪体中的三酰基甘油储存，而在进食后 7 天内血液消化仍保持不变。脂质含量降低归因于从头合成脂质减少以及该器官内血液衍生脂肪酸掺入新合成脂质减少。与此一致的是，RhoprIR 缺陷昆虫的脂肪体中脂联蛋白受体 (RhoprLpR)、甘油-3-磷酸酰基转移酶 1 和 4 (RhoprGpat1 和 RhoprGpat4) 和肉碱棕榈酰基转移酶 1 (RhoprCpt1) 的基因表达水平降低。尽管 RhoprIR 破坏不影响血液中的脂质谱，但循环卵黄蛋白原的浓度增加。与这些变化一致的是，RhoprIR 缺陷的雌性昆虫卵巢较小，产卵量明显减少。综上所述，这些发现支持胰岛素受体在进食后营养平衡、脂质合成和产卵中的关键作用。
