Haselton Aaron T, Fridell Yih-Woei C
Department of Biology, State University of New York, USA.
J Vis Exp. 2011 Jun 30(52):2722. doi: 10.3791/2722.
Conserved nutrient sensing mechanisms exist between mammal and fruit fly where peptides resembling mammalian insulin and glucagon, respectively function to maintain glucose homeostasis during developmental larval stages. Studies on largely post-mitotic adult flies have revealed perturbation of glucose homeostasis as the result of genetic ablation of insulin-like peptide (ILP) producing cells (IPCs). Thus, adult fruit flies hold great promise as a suitable genetic model system for metabolic disorders including type II diabetes. To further develop the fruit fly system, comparable physiological assays used to measure glucose tolerance and insulin sensitivity in mammals must be established. To this end, we have recently described a novel procedure for measuring oral glucose tolerance response in the adult fly and demonstrated the importance of adult IPCs in maintaining glucose homeostasis. Here, we have modified a previously described procedure for insulin injection and combined it with a novel hemolymph extraction method to measure peripheral insulin sensitivity in the adult fly. Uniquely, our protocol allows direct physiological measurements of the adult fly's ability to dispose of a peripheral glucose load upon insulin injection, a methodology that makes it feasible to characterize insulin signaling mutants and potential interventions affecting glucose tolerance and insulin sensitivity in the adult fly.
哺乳动物和果蝇之间存在保守的营养感知机制，在果蝇幼虫发育阶段，分别类似于哺乳动物胰岛素和胰高血糖素的肽发挥作用以维持葡萄糖稳态。对大多处于有丝分裂后期的成年果蝇的研究表明，胰岛素样肽（ILP）产生细胞（IPC）的基因消融会导致葡萄糖稳态紊乱。因此，成年果蝇作为包括II型糖尿病在内的代谢紊乱的合适遗传模型系统具有很大潜力。为了进一步开发果蝇系统，必须建立用于测量哺乳动物葡萄糖耐量和胰岛素敏感性的可比生理测定方法。为此，我们最近描述了一种测量成年果蝇口服葡萄糖耐量反应的新方法，并证明了成年IPC在维持葡萄糖稳态中的重要性。在此，我们改进了先前描述的胰岛素注射方法，并将其与一种新的血淋巴提取方法相结合，以测量成年果蝇的外周胰岛素敏感性。独特的是，我们的方案允许直接生理测量成年果蝇在注射胰岛素后处理外周葡萄糖负荷的能力，这种方法使得表征胰岛素信号突变体以及影响成年果蝇葡萄糖耐量和胰岛素敏感性的潜在干预措施成为可能。
