The pathogenesis of obesity remains incompletely understood. Drosophila have conserved neuroendocrine and digestion systems with human and become an excellent system for studying energy homeostasis. Here, we reported a novel obesity Drosophila model, in which expression of human protein, synphilin-1 (SP1), in neurons fosters positive energy balance.
Subjects and methods:
To further understand the actions of SP1 in energy balance control, the upstream activation sequence UAS/GAL4 system was used to generate human SP1 transgenic Drosophila. We characterized a human SP1 transgenic Drosophila by assessing SP1 expression, fat lipid deposition, food intake and fly locomotor activity to determine the major behavioral changes and their consequences in the development of the obesity-like phenotype.
Overexpression of SP1 in neurons, but not peripheral cells, increased the body weight of flies compared with that of non-transgenic controls. SP1 increased food intake but did not affect locomotor activity. SP1 increased the levels of triacylglycerol, and the size of fat body cells and lipid droplets, indicating that SP1 increased lipid-fat disposition. Survival studies showed that SP1 transgenic flies were more resistant to food deprivation. SP1 regulated lipin gene expression that may participate in SP1-induced fat deposition and starvation resistance.
These studies demonstrate that SP1 expression affects energy homeostasis in ways that enhance positive energy balance and provide a useful obesity model for future pathogenesis and therapeutic studies.
"Feeding behavior is dramatically reduced in starvationresistant adult Drosophila Obesity in Drosophila can be induced in the laboratory by manipulating traits, such as decreasing metabolic rate, prolonging larval development, or increasing food consumption (Al-Anzi et al., 2009; Hathiramani et al., 2011; Liu et al., 2012). It has been suggested that larval development is a primary contributor to evolved starvation resistance, which is attributed to significantly elevated lipid levels in newly eclosed adults ( "
[Show abstract][Hide abstract] ABSTRACT: Animals respond to changes in food availability by adjusting sleep and foraging strategies to optimize their fitness. Wild populations of the fruit fly, Drosophila melanogaster, display highly variable levels of starvation resistance that are dependent on geographic location, food availability, and evolutionary history. How behaviors that include sleep and feeding vary in Drosophila with increased starvation resistance is unclear. We have generated starvation resistant flies through experimental evolution to investigate the relationship between foraging behaviors and starvation resistance. Outbred populations of D. melanogaster were selected for starvation resistance over 60 generations. This selection process resulted in flies with a three-fold increase in total lipids that survive up to 18 days without food. We tested starvation-selected (S) flies for sleep and feeding behaviors to determine the effect that selection for starvation resistance has had on foraging behavior. Flies from three replicated starvation-selected populations displayed a dramatic reduction in feeding and prolonged sleep duration compared to fed control (F) populations, suggesting that modified sleep and feeding may contribute to starvation resistance. A prolonged larval developmental period contributes to the elevated energy stores present in starvation-selected flies. By preventing S larvae from feeding longer than F larvae, we were able to reduce energy stores in adult S flies to levels seen in adult F flies, thus allowing us to control for energy storage levels. However, the reduction of energy stores in S flies fails to generate normal sleep and feeding behavior seen in F flies with similar energy stores. These findings suggest that the behavioral changes observed in S flies are due to genetic regulation of behavior rather than elevated lipid levels. Testing S-F hybrid individuals for both feeding and sleep revealed a lack of correlation between food consumption and sleep duration, indicating further independence in genetic factors underlying the sleep and feeding changes observed in S flies. Taken together, these findings provide evidence that starvation selection results in prolonged sleep and reduced feeding through a mechanism that is independent of elevated energy stores. These findings suggest changes in both metabolic function and behavior contribute to the increase in starvation resistance seen in flies selected for starvation resistance.
"Synphilin-1 can reduce PD-linked mutant alpha-synuclein-, rotenone-, and 6-HODA-induced toxicity in vitro and delays alpha-synucleinopathies in a PD mouse model in vivo , . Recent studies of human synphilin-1 transgenic Drosophila and mouse models have revealed that overexpression of human synphilin-1 results in increases in food intake, body weight and fat deposition, resembling key features of human obesity , . While these studies suggest a role for synphilin-1 in regulating energy balance, the biological mechanisms underlying synphilin-1-mediated hyperphagia and obesity are unknown. "
[Show abstract][Hide abstract] ABSTRACT: Synphilin-1 is a cytoplasmic protein that has been shown to be involved in the control of energy balance. Previously, we reported on the generation of a human synphilin-1 transgenic mouse model (SP1), in which overexpression of human synphilin-1 resulted in hyperphagia and obesity. Here, behavioral measures in SP1 mice were compared with those of their age-matched controls (NTg) at two time points: when there was not yet a group body weight difference ("pre-obese") and when SP1 mice were heavier ("obese"). At both time points, meal pattern analyses revealed that SP1 mice displayed higher daily chow intake than non-transgenic control mice. Furthermore, there was an increase in meal size in SP1 mice compared with NTg control mice at the obese stage. In contrast, there was no meal number change between SP1 and NTg control mice. In a brief-access taste procedure, both "pre-obese" and "obese" SP1 mice displayed concentration-dependent licking across a sucrose concentration range similar to their NTg controls. However, at the pre-obese stage, SP1 mice initiated significantly more trials to sucrose across the testing sessions and licked more vigorously at the highest concentration presented, than the NTg counterparts. These group differences in responsiveness to sucrose were no longer apparent in obese SP1 mice. These results suggest that at the pre-obese stage, the increased trials to sucrose in the SP1 mice reflects increased appetitive behavior to sucrose that may be indicative of the behavioral changes that may contribute to hyperphagia and development of obesity in SP1 mice. These studies provide new insight into synphilin-1 contributions to energy homeostasis.
PLoS ONE 05/2014; 9(5):e91449. DOI:10.1371/journal.pone.0091449 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Serotonin (5-hydroxytryptamine, 5-HT) is an ancient and conserved neuromodulator of energy balance. Despite its importance, the neural circuits and molecular mechanisms underlying 5-HT-mediated control of body fat remain poorly understood. Here, we decipher the serotonergic neural circuit for body fat loss in C. elegans and show that the effects of 5-HT require signaling from octopamine, the invertebrate analog of adrenaline, to sustain body fat loss. Our results provide a potential molecular explanation for the long-observed potent effects of combined serotonergic and adrenergic weight loss drugs. In metabolic tissues, we find that the conserved regulatory adipocyte triglyceride lipase ATGL-1 drives serotonergic fat loss. We show that the serotonergic chloride channel MOD-1 relays a long-range endocrine signal from C. elegans body cavity neurons to control distal ATGL-1 function, via the nuclear receptor NHR-76. Our findings establish a conserved neuroendocrine axis operated by neural serotonergic and adrenergic-like signaling to regulate body fat.
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