Regulation of starvation-mediated hyperactivity and triglyceride metabolism by Short neuropeptide F and Insulin Like Peptide in Drosophila
The circadian clock regulates various behavioral, metabolic and physiological processes to occur at the most suitable time of the day. Internal energy stores and nutrient availability modulates the most apparent circadian clock mediated locmotor activity rhythm in Drosophila. Although previous studies unraveled the role of circadian clock in metabolism and activity rest rhythm, the precise pathway through which the circadian neuropeptidergic signaling regulates internal energy storage and the starvation-mediated increase in activity resembling foraging remains largely unclear. This study was aimed to elucidate the role of circadian neuropeptide, short neuropeptide F (sNPF) in triglyceride metabolism, starvation resistance and starvation-mediated increased locomotor activity in Drosophila. The results showed that snpf transcripts exhibits significant rhythmicity in wild type flies under 12:12 hour light-dark cycles (LD) and constant darkness (DD) whereas snpf transcript level in period null flies did not exhibit any significant rhythmicity under LD. Knockdown of sNPF in circadian clock neurons reduced the triglyceride level, starvation resistance and increased the starvation-mediated hyperactivity response after 24 hour of starvation. Further studies showed that knock down of sNPF receptors (sNPFR) expressed in insulin producing cells (IPC) increased the starvation resistance and reduced starvation-induced hyperactivity response after 24 hour of starvation. Collectively, our results suggest that transcriptional oscillation of snpf mRNA is endogenously controlled by the circadian clock and elucidate the role of sNPF in modulating locomotor activity in accordance with the nutrient availability in Drosophila.