Loss of function in the Drosophila clock gene period results in altered intermediary lipid metabolism and increased susceptibility to starvation

Abstract

The fruit fly Drosophila is a prime model in circadian research, but still little is known about its circadian regulation of metabolism. Daily rhythmicity in levels of several metabolites has been found, but knowledge about hydrophobic metabolites is limited. We here compared metabolite levels including lipids between period 01 (per 01) clock mutants and CantonS wildtype (WT CS) flies in an isogenic and non-isogenic background using LC-MS. In the non-isogenic background, metabolites with differing levels comprised essential amino acids, kynurenines, pterinates, glycero(phospho)lipids, and fatty acid esters. Notably, detectable diacylglycerols (DAG) and acylcarnitines (AC), involved in lipid metabolism, showed lower levels in per 01 mutants. Most of these differences disappeared in the isogenic background, yet the level differences for AC as well as DAG were consistent for fly bodies. AC levels were dependent on the time of day in WT CS in phase with food consumption under LD conditions, while DAGs showed weak daily oscillations. Two short-chain ACs continued to cycle even in constant darkness. per 01 mutants in LD showed no or very weak diel AC oscillations out of phase with feeding activity. The low levels of DAGs and ACs in per 01 did not correlate with lower total food consumption, body mass or weight. Clock mutant flies showed higher sensitivity to starvation independent of their background-dependent activity level. Our results suggest that neither feeding, energy storage nor mobilisation is significantly affected in per 01 mutants, but point towards impaired mitochondrial activity, supported by upregulation of the mitochondrial stress marker 4EBP in the clock mutants.

Model and Non-model Insects in Chronobiology

“…Similar to activity, feeding occurs at slightly different times of the day in male and female flies. While males feed maximally in the early morning, females do so from the middle of the day until the evening (Seay and Thummel, 2011;Xu et al, 2011;Liu et al, 2020;Schäbler et al, 2020). In summary, general activity, mating and feeding occur at different times of the day and additionally show sex differences in timing.…”

Circadian rhythms and obesity: Timekeeping governs lipid metabolism

“…[38][39][40][41] Period-mutant Drosophila show an intermediary change in lipid metabolism (detectable diacylglycerols and acylcarnitines) and increased sensitivity to starvation. 34 In turn, a significant increase in the expression of the Bmal1, Cry1, Cry2, and Per2 genes during the light (day) phase and downregulation in the dark (night) phase is observed in obese patients, 42 indicating that the expression of circadian clock genes and their downstream pathways are also influenced by lipid metabolic disorders.…”

“…30 However, various studies show that circadian disruption, either genetic or environmental variants (ie, nocturnal light exposure, sleep disorders, social jet lag, and late-night snacking), widely affects host lipid metabolism and accelerates the development of obesity. [31][32][33][34] For example, both Clock mutant (delta 19) and Bmal1 knockout (KO) mice exhibit glucose intolerance, reduced insulin secretion, increased sensitivity to high-fat diet feeding, are hyperphagic and became overweight. [35][36][37] Additionally, glucose metabolism and systemic glucose homeostasis are also impaired in peripheral tissues-specific (skeletal muscle, beta cells and liver) Bmal1 KO models.…”

Endocrine fine-tuning of daily locomotor activity patterns under non-starving conditions in Drosophila

“…Glucose-6,6-d 2 and Trehalose-1,1′-d 2 were used as internal standards for quantification of mono-and disaccharides. Trehalose-1,1′-d 2 343 180 32 15 Determination of diacylglycerols were performed according to [86]. Prior to analysis, haemolymph samples were dried and recovered in 75 µl isopropanol containing 1 µg/ml 1,2-didecanoyl-glycerol used as an internal standard.…”

“…Trehalose-1,1′-d2 were used as internal standards for quantification of mono-and disaccharides. Determination of diacylglycerols were performed according to [86].…”