Chronic Circadian Misalignment Results in Reduced Longevity and Large-Scale Changes in Gene Expression in Drosophila

We investigated the consequences of chronic circadian misalignment (CCM) in the powerful model system of the fruit fly, Drosophila melanogaster. We subjected flies to daily 4-hr phase delays in the light-dark schedule and used the Drosophila Activity Monitoring (DAM) system to continuously track locomotor activity and sleep while simultaneously monitoring fly lifespan. Consistent with previous results, we find that exposing flies to CCM leads to a ~15% reduction in median lifespan in both male and female flies. Importantly, we demonstrate that the reduced longevity occurs independent of changes in overall sleep or activity. To uncover potential molecular mechanisms of CCM-induced reduction in lifespan, we conducted whole body RNA-sequencing to assess differences in gene transcription between control and misaligned flies. CCM caused progressive, large-scale changes in gene expression characterized by upregulation of genes involved in response to toxic substances, aging and oxidative stress, and downregulation of genes involved in regulation of development and differentiation, gene expression and biosynthesis. Many of these gene expression changes mimic those that occur during natural aging, consistent with the idea that CCM results in premature organismal decline, however, we found that genes involved in lipid metabolism are overrepresented among those that are differentially regulated by CCM and aging. This category of genes is also among the earliest to exhibit CCM-induced changes in expression, thus highlighting altered lipid metabolism as a potentially important mediator of the negative health consequences of CCM. Humidity and temperature-controlled incubators were used to expose male and female iso31 flies to either a 24-hour schedule (LD 12:12; control group), or a 28-hour schedule (LD 14:14; chronic circadian misalignment (CCM) group) for 2 or 3 weeks. Flies were fed 5% sucrose/ 2% agar food. 10 male and 10 female flies were collected for each sample (3 CCM and 3 control samples at each time point; 12 total) and total RNA was extracted at ZT0-3