Background: The synthetic steroid mifepristone is reported to have anti-obesity and anti-diabetic effects in mammals on normal and high-fat diets (HFD). We previously reported that mifepristone blocks the negative effect on life span caused by mating in female Drosophila melanogaster.Methods: Here we asked if mifepristone could protect virgin females from the life span-shortening effect of HFD. Mifepristone was assayed for effects on life span in virgin females, in repeated assays, on regular media and on media supplemented with coconut oil (HFD). The excrement quantification (EX-Q) assay was used to measure food intake of the flies after 12 days mifepristone treatment. In addition, experiments were conducted to compare the effects of mifepristone in virgin and mated females, and to identify candidate mifepristone targets and mechanisms.Results: Mifepristone increased life span of virgin females on regular media, as well as on media supplemented with either 2.5 or 5% coconut oil. Food intake was not reduced in any assay, and was significantly increased by mifepristone in half of the assays. To ask if mifepristone might rescue virgin females from all life span-shortening stresses, the oxidative stressor paraquat was tested, and mifepristone produced little to no rescue. Analysis of extant metabolomics and transcriptomics data suggested similarities between effects of mifepristone in virgin and mated females, including reduced tryptophan breakdown and similarities to dietary restriction. Bioinformatics analysis identified candidate mifepristone targets, including transcription factors Paired and Extra-extra. In addition to shortening life span, mating also causes midgut hypertrophy and activation of the lipid metabolism regulatory factor SREBP. Mifepristone blocked the increase in midgut size caused by mating, but did not detectably affect midgut size in virgins. Finally, mating increased activity of a SREBP reporter in abdominal tissues, as expected, but reporter activity was not detectably reduced by mifepristone in either mated or virgin females.Conclusion: Mifepristone increases life span of virgin females on regular and HFD without reducing food intake. Metabolomics and transcriptomics analyses suggest some similar effects of mifepristone between virgin and mated females, however reduced midgut size was observed only in mated females. The results are discussed regarding possible mifepristone mechanisms and targets.
This article describes the characterization of a new Drosophila gene that we have called pitchoune (pit) (meaning small in Provence) because mutations in this gene produce larvae that cannot grow beyond the first instar larval stage although they can live as long as 7–10 days. All the tissues are equally affected and the perfectly shaped larvae are indistinguishable from first instar wild-type animals. Analysis of mutant somatic clones suggests a function in cell growth and proliferation, which is supported by the fact that cell proliferation is promoted by pit overexpression. Tagged-Pit, when transfected in S2 cells, localizes mainly to the nucleolus, pointing towards a possible role in ribosome biogenesis and, consequently, in protein biosynthesis. pit encodes a DEAD-box RNA helicase, a family of proteins involved in the control of RNA structure in many cellular processes and its closest homologue is a human DEAD-box RNA helicase, MrDb, whose corresponding gene transcription is directly activated by Myc-Max heterodimers (Grandori, C., Mac, J., Siebelt, F., Ayer, D. E. and Eisenman, R. N. (1996) EMBO J. 15, 4344–4357). The patterns of expression of d-myc and pit are superimposable. Ectopic expression of myc in the nervous system drives an ectopic expression of pit in this tissue indicating that in Drosophila as well, pit is a potential target of d-Myc. These results suggest that myc might promote cell proliferation by activating genes that are required in protein biosynthesis, thus linking cell growth and cell proliferation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.