A role for the circadian photoreceptor CRYPTOCHROME in regulating triglyceride metabolism in <i>Drosophila</i>

The biological rhythms generated by the endogenous circadian clocks across the tree of life regulate numerous behavioral, metabolic, and physiological processes. Although evidence from various studies in Drosophila melanogaster indicates the importance of the core circadian clock genes in the intricate interplay between the circadian clock and metabolism, little is known about the contribution of the circadian photoreceptor/s in this process. The deep brain circadian photoreceptor CRYPTOCHROME (CRY) is essential for resetting the clock in response to light and is also highly expressed in metabolically active tissues in Drosophila. In this study, we sought to explore the possible roles played by CRY in triglyceride (TG) metabolism. We observed that the cry mutant (cry01) flies exhibited increased starvation resistance and TG levels under both 12-hour (h) light:12-h dark cycle (LD) and under constant light compared with the control w1118 flies. We also observed that cry01 flies had significantly increased food intake, glycogen concentrations, and lifespan under LD. In addition, cryptochrome seemed to affect TG levels in adult flies in response to calorie-restricted and high-fat diets. These results suggest a role for the circadian photoreceptor CRY in TG metabolism in Drosophila.