Muscle directs diurnal energy homeostasis through a myokine-dependent hormone module in Drosophila

Inter-tissue communication is critical to control organismal energy homeostasis in response to temporal changes in feeding and activity or external challenges. Muscle is emerging as a key mediator of this homeostatic control through consumption of lipids, carbohydrates, and amino acids, as well as governing systemic signaling networks. However, it remains less clear how energy substrate usage tissues, such as muscle, communicate with energy substrate storage tissues in order to adapt with diurnal changes in energy supply and demand. Using Drosophila, we show here that muscle plays a crucial physiological role in promoting systemic synthesis and accumulation of lipids in fat storage tissues through Foxo. To gain more insight into these tissue-specific changes in lipid metabolism, we generated genome-wide expression profiles from dissected thoraces (enriched in indirect flight muscle), carcass (enriched in fat body), and intestines of Act88FG4>FoxoRNAi flies and control animals. Intact fly thorax, carcass (with all of the eggs and intact intestines removed) and intestines were dissected in PBS from Act88FGal4>UAS-FoxoRNAi or genetically matched control flies (Act88FGal4>w1118) 10 days post-eclosion. Total RNA was extracted using Trizol reagent and used as template to generate sample libraries for RNA sequencing (using the TruSeq Stranded Total RNA Library Prep Kit). Sample libraries were sequenced using the Illumina HiSeq 2500. Sequence cluster identification, quality pre-filtering, base calling and uncertainty assessment were done in real time using Illumina's HCS 2.2.58 and RTA 1.18.64 software with default parameter settings. Between 7 and 12 million (1X50) base pair reads were generated per library and mapped to the Drosophila genome (Release 6).