Excreta Quantification (EX-Q) for Longitudinal Measurements of Food Intake in Drosophila.
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ABSTRACT:
SUBMITTER: Wu Q
PROVIDER: S-EPMC6941854 | biostudies-literature | 2020 Jan
REPOSITORIES: biostudies-literature
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Project description:Food intake is an essential animal activity, regulated by neural circuits that motivate food localization, evaluate nutritional content and acceptance or rejection responses through the gustatory system, and regulate neuroendocrine feedback loops that maintain energy homeostasis. Excess food consumption in people is associated with obesity and metabolic and cardiovascular disorders. However, little is known about the genetic basis of natural variation in food consumption. To gain insights in evolutionarily conserved genetic principles that regulate food intake, we took advantage of a model system, Drosophila melanogaster, in which food intake, environmental conditions and genetic background can be controlled precisely. We quantified variation in food intake among 182 inbred, sequenced lines of the Drosophila melanogaster Genetic Reference Panel (DGRP). We found significant genetic variation in the mean and within-line environmental variance of food consumption and observed sexual dimorphism and genetic variation in sexual dimorphism for both food intake traits (mean and variance). We performed genome wide association (GWA) analyses for mean food intake and environmental variance of food intake (using the coefficient of environmental variation, CVE, as the metric for environmental variance) and identified molecular polymorphisms associated with both traits. Validation experiments using RNAi-knockdown confirmed 24 of 31 (77%) candidate genes affecting food intake and/or variance of food intake, and a test cross between selected DGRP lines confirmed a SNP affecting mean food intake identified in the GWA analysis. The majority of the validated candidate genes were novel with respect to feeding behavior, and many had mammalian orthologs implicated in metabolic diseases.
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Project description:Food intake is a fundamental parameter in animal studies. Despite the prevalent use of Drosophila in laboratory research, precise measurements of food intake remain challenging in this model organism. Here, we compare several common Drosophila feeding assays: the capillary feeder (CAFE), food labeling with a radioactive tracer or colorimetric dye and observations of proboscis extension (PE). We show that the CAFE and radioisotope labeling provide the most consistent results, have the highest sensitivity and can resolve differences in feeding that dye labeling and PE fail to distinguish. We conclude that performing the radiolabeling and CAFE assays in parallel is currently the best approach for quantifying Drosophila food intake. Understanding the strengths and limitations of methods for measuring food intake will greatly advance Drosophila studies of nutrition, behavior and disease.
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Project description:Feeding and sleep are highly conserved, interconnected behaviors essential for survival. Starvation has been shown to potently suppress sleep across species; however, whether satiety promotes sleep is still unclear. Here we use the fruit fly, Drosophila melanogaster, as a model organism to address the interaction between feeding and sleep. We first monitored the sleep of flies that had been starved for 24 h and found that sleep amount increased in the first 4 h after flies were given food. Increased sleep after starvation was due to an increase in sleep bout number and average sleep bout length. Mutants of translin or adipokinetic hormone, which fail to suppress sleep during starvation, still exhibited a sleep increase after starvation, suggesting that sleep increase after starvation is not a consequence of sleep loss during starvation. We also found that feeding activity and food consumption were higher in the first 10-30 min after starvation. Restricting food consumption in starved flies to 30 min was sufficient to increase sleep for 1 h. Although flies ingested a comparable amount of food at differing sucrose concentrations, sleep increase after starvation on a lower sucrose concentration was undetectable. Taken together, our results suggest that increased food intake after starvation enhances sleep and reveals a novel relationship between feeding and sleep.
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Project description:ObjectiveMeasures of glycaemic impact (e.g. postprandial glucose (PPG), oral glucose tolerance test (OGTT) and glycaemic index (GI)) are used by government health and regulatory agencies and public health associations around the world. The objective of this global review was to identify similarities and differences in the use of glycaemic impact measures for potential considerations for harmonisation.DesignA literature and internet search was conducted to identify country government agencies and health associations that provide guidance or recommendations for PPG, OGTT, GI and glycaemic load.ResultsBased on this global review, the use of GI for food labelling (e.g. low GI) is limited and its use is voluntary. The application of OGTT as a diagnostic measurement of diabetes and gestational diabetes is widely used and in a consistent manner among the different regions of the world. Time-specific (e.g. 2 h) PPG is commonly used as a target not to exceed in individuals with diabetes and gestational diabetes. PPG is used by regulatory agencies for the substantiation of food labelling. There are differences, however, among regulatory agencies in the specific measure of PPG (i.e. PPG AUC v. peak PPG). Maximum targets for 2-h PPG for individuals with diabetes and gestational diabetes, ranging between 6 and 10 mmol/l, across countries suggest a potential consideration to harmonise PPG targets.ConclusionsThere is general consistency in the use and/or target levels of glycaemic impact measures; however, there is a potential need to investigate harmonisation strategies on certain aspects of glycaemic impact measures.
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Project description:The Drosophila model is used to investigate the effects of diet on physiology as well as the effects of genetic pathways, neural systems and environment on feeding behavior. We previously showed that Blue 1 works well as a dye tracer to track consumption of agar-based media in Drosophila in a method called Con-Ex. Here, we describe Orange 4 as a novel dye for use in Con-Ex studies that expands the utility of this method. Con-Ex experiments using Orange 4 detect the predicted effects of starvation, mating status, strain, and sex on feeding behavior in flies. Orange 4 is consumed and excreted into vials linearly with time in Con-Ex experiments, the number of replicates required to detect differences between groups when using Orange 4 is comparable to that for Blue 1, and excretion of the dye reflects the volume of consumed dye. In food preference studies using Orange 4 and Blue 1 as a dye pair, flies decreased their intake of food laced with the aversive tastants caffeine and NaCl as determined using Con-Ex or a more recently described modification called EX-Q. Our results indicate that Orange 4 is suitable for Con-Ex experiments, has comparable utility to Blue 1 in Con-Ex studies, and can be paired with Blue 1 to assess food preference via both Con-Ex and EX-Q.
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Project description:Insulin and IGF signaling are critical to numerous developmental and physiological processes, with perturbations being pathognomonic of various diseases, including diabetes. Although the functional roles of the respective signaling pathways have been extensively studied, the control of insulin production and release is only partially understood. Herein, we show that in Drosophila expression of insulin-like peptides is regulated by neprilysin activity. Concomitant phenotypes of altered neprilysin expression included impaired food intake, reduced body size, and characteristic changes in the metabolite composition. Ectopic expression of a catalytically inactive mutant did not elicit any of the phenotypes, which confirms abnormal peptide hydrolysis as a causative factor. A screen for corresponding substrates of the neprilysin identified distinct peptides that regulate insulin-like peptide expression, feeding behavior, or both. The high functional conservation of neprilysins and their substrates renders the characterized principles applicable to numerous species, including higher eukaryotes and humans.
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Project description:The Drosophila model has become a leading platform for investigating mechanisms that drive feeding behavior and the effect of diet on physiological outputs. Several methods for tracking feeding behavior in flies have been developed. One method, consumption-excretion or Con-Ex, provides flies with media labeled with dye and then quantifies the amount of dye excreted into the vial as a measure of consumption. We previously found that Blue 1 and Orange 4 work well in Con-Ex and can be used as a dye pair in food preference studies. We have expanded our development of Con-Ex by identifying two additional dyes, Orange G and Yellow 10, that detect the anticipated effects of mating status, strain, starvation and nutrient concentration. Additionally, Orange G and Yellow 10 accumulate linearly in excretion products out to 48 h and the excreted volumes of these two dyes reflect the volumes consumed. Orange G also works with Blue 1 as a dye pair in food preference studies. Finally, consumption of Blue 1, Orange 4, Orange G or Yellow 10 does not affect ethanol sedation or rapid tolerance to ethanol. Our findings establish that Orange G and Yellow 10, like Blue 1 and Orange 4, are suitable for use in Con-Ex.
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Project description:BackgroundWhile dietary intake is shaped by cost, there is minimal research on the association between community-level food prices and dietary intake.MethodsWe used nationally representative, longitudinal data to examine how community-level food price variation was associated with individual-level fast food intake by race/ethnicity and income across waves II (1996) and III (2001-2002) of the National Longitudinal Study of Adolescent Health (n=11,088) from 158 baseline and 363 follow-up US counties.ResultsNegative binomial regression models predicting the number of fast food meals per week show strong relationships between fast food consumption and prices of fast food and soda that varied by gender and race/ethnicity. We found relatively stronger association between food prices and fast food intake for males and relatively greater price sensitivity for soda versus burgers. In the group with strongest associations (black males), a 20% increase in the price of soda was associated with a decrease of 0.25 visits to a fast food restaurant per week.ConclusionsEconomic incentives may be an effective mechanism to address fast food intake in an age group at high risk for obesity.
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Project description:Although the Drosophila melanogaster (fly) model is a popular platform for investigating diet-related phenomena, it can be challenging to measure the volume of agar-based food media flies consume. We addressed this challenge by developing a dye-based method called Consumption-Excretion (Con-Ex). In Con-Ex studies, flies consume solid food labeled with dye, and the volume of food consumed is reflected by the sum of the dye inside of and excreted by flies. Flies consumed-excreted measurable amounts of FD&C Blue No. 1 (Blue 1) and other dyes in Con-Ex studies, but only Blue 1 was readily detectable at concentrations that had no discernable effect on consumption-excretion. In studies with Blue 1, consumption-excretion (i) increased linearly with feeding duration out to 24?h at two different laboratory sites, (ii) was sensitive to starvation, mating status and strain, and (iii) changed in response to alteration of media composition as expected. Additionally, the volume of liquid Blue 1 consumed from capillary tubes was indistinguishable from the volume of Blue 1 excreted by flies, indicating that excreted Blue 1 reflects consumed Blue 1. Our results demonstrate that Con-Ex with Blue 1 as a food tracer is a useful method for assessing ingestion of agar-based food media in adult flies.
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Project description:Food parenting practices (FPPs) have an important role in shaping children's dietary behaviors. This study aimed to investigate cross-sectional and longitudinal associations over a two-year follow-up between FPP and dietary intake and compliance with current recommendations in 6- to 11-year-old European children. A total of 2967 parent-child dyads from the Feel4Diabetes study, a randomized controlled trial of a school and community-based intervention, (50.4% girls and 93.5% mothers) were included. FPPs assessed were: (1) home food availability; (2) parental role modeling of fruit intake; (3) permissiveness; (4) using food as a reward. Children's dietary intake was assessed through a parent-reported food frequency questionnaire. In regression analyses, the strongest cross-sectional associations were observed between home availability of 100% fruit juice and corresponding intake (β = 0.492 in girls and β = 0.506 in boys, p < 0.001), and between parental role modeling of fruit intake and children's fruit intake (β = 0.431 in girls and β = 0.448 in boys, p < 0.001). In multilevel logistic regression models, results indicated that improvements in positive FPPs over time were mainly associated with higher odds of compliance with healthy food recommendations, whereas a decrease in negative FPP over time was associated with higher odds of complying with energy-dense/nutrient-poor food recommendations. Improving FPPs could be an effective way to improve children's dietary intake.
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