SHORT COMMUNICATION Central metabolic sensing remotely controls nutrient-sensitive endocrine response in Drosophila via Sir2/Sirt1–upd2–IIS axis Kushal K. Banerjee, Rujuta S. Deshpande, Pranavi Koppula, Champakali Ayyub and Ullas Kolthur-Seetharam* ABSTRACT Endocrine signaling is central in coupling organismal nutrient status with maintenance of systemic metabolic homeostasis. While local nutrient sensing within the insulinogenic tissue is well studied, distant mechanisms that relay organismal nutrient status in controlling metabolic–endocrine signaling are less well understood. Here, we report a novel mechanism underlying the distant regulation of the metabolic endocrine response in Drosophila melanogaster. We show that the communication between the fat body and insulin-producing cells (IPCs), important for the secretion of Drosophila insulin-like peptides (dILPs), is regulated by the master metabolic sensor Sir2/Sirt1. This communication involves a fat body-specific direct regulation of the JAK/STAT cytokine upd2 by Sir2/Sirt1. We have also uncovered the importance of this regulation in coupling nutrient inputs with dILP secretion, and distantly controlling insulin/IGF signaling (IIS) in the intestine. Our results provide fundamental mechanistic insights into the top-down control involving tissues that play key roles in metabolic sensing, endocrine signaling and nutrient uptake. KEY WORDS: Metabolic homeostasis, NAD + sensor, JAK/STAT ligand, Insulin secretion, Metabolism, Nutrient sensing, DILP secretion, Insulin signaling, Intestine INTRODUCTION Metabolic homeostasis is indispensable for all organisms and involves the coupling of metabolic sensing with adaptive responses. In multicellular organisms, metabolic homeostasis depends on efficient communication across diverse organ systems, predominantly by endocrine mechanisms (Frühbeck et al., 2001; Pedersen, 2011; Stefan and Häring, 2013; Unger et al., 1978). Pancreatic hormones such as insulin and glucagon couple organismal nutrient status with nutrient uptake across organ systems (Unger et al., 1978). A large body of work has facilitated our understanding of the mechanisms within insulinogenic cells (specifically, pancreatic β-islets in vertebrates) that mediate the integration of organismal nutrient status with insulin secretion (Rorsman and Braun, 2013). However, emerging findings from evolutionarily diverse organisms highlight the importance of such an endocrine control from distant tissues (Song et al., 2014; Géminard et al., 2009). In this context, relatively less is known about molecular factors that mediate distant regulation of insulin secretion across species. The evolutionarily conserved NAD + sensor Sir2/Sirt1 plays critical roles in controlling insulin secretion from the β-islets in the pancreas (Ramachandran et al., 2011; Bordone et al., 2006). Previous reports from our lab and others have indicated a possible role for Sir2/Sirt1 in distant tissues in regulating insulin production and secretion (Palu and Thummel, 2016; Schenk et al., 2011; Wang et al., 2011; Purushotham et al., 2009; Banerjee et al., 2013). However, the mechanistic details and the physiological understanding of this endocrine control are currently lacking. Drosophila melanogaster has been extensively used to investigate the physiological and genetic bases of metabolic homeostasis. Under conditions of nutrient excess, the insulin-producing cells (IPCs) located in the median neurosecretory cluster (mNSC) in the brain secrete Drosophila insulin-like peptides (dILPs) (Ikeya et al., 2002; Kim and Rulifson, 2004). Interestingly, IPCs lack the ability to sense organismal metabolic status and depend on signals from the fat body (Ikeya et al., 2002; Kim and Rulifson, 2004). Genetic evidence implicates the metabolic transcription factor FOXO (dFOXO) (Hwangbo et al., 2004), target of rapamycin (TOR) signaling (Géminard et al., 2009) and a secretory cytokine upd2 (Rajan and Perrimon, 2012), among others, in mediating the distant control of dILP secretion by the fat body. However, the physiological relevance of these factors and a role for a master metabolic sensor within the fat body in establishing systemic metabolic homeostasis by controlling an inter-organ communication network has not been addressed. Here, we have investigated the molecular underpinnings of the distant control of a metabolic response by addressing the role of the master metabolic sensor Sir2/Sirt1 within the fat body in regulating an endocrine response to nutrient fluctuations. MATERIALS AND METHODS Fly stocks S 1 106 (P{Switch 1}106 Gal4), Sir2/Sirt1 EP2300 (w 1118 ; P{w[+mC] =EP}Sirt1[EP2300] DnaJ-H[EP2300]/CyO), chico (cn 1 P{ry11} chico 1 /CyO; ry 506 ) and InR (InR E19 /TM2) stocks were obtained from Bloomington Stock Center (Indiana University). SIR2 RNAi (23201) and upd2 RNAi (6513) lines were obtained from Vienna Drosophila RNAi Center (VDRC). Growth conditions Flies were grown on standard CM/S/Y media (8.6% cornmeal, 5% sucrose, 2.5% yeast) under non-crowding conditions at 25°C with a 12 h:12 h light:dark cycle. Age-matched 3–5 day old female flies were used for all analyses. Activation of Gal4 Gene-switch Gal4 S 1 106 was crossed with relevant transgene lines. Gal4 was activated to drive UAS-RNAi or EP-Sir2/Sirt1 lines, by rearing the appropriate lines on diets supplemented with 200 μmol l -1 (or 400 μmol l -1 , in the case of RNAi combinations) RU486 (Mifeprestone, Sigma-Aldrich; hereafter, RU) dissolved in 95% ethanol. Flies that were reared on diets containing only ethanol served as controls. Received 20 October 2016; Accepted 12 January 2017 Department of Biological Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India. *Author for correspondence (ullas@tifr.res.in) U.K., 0000-0003-2612-1743 1187 © 2017. Published by The Company of Biologists Ltd | Journal of Experimental Biology (2017) 220, 1187-1191 doi:10.1242/jeb.150805 Journal of Experimental Biology