dFatp regulates nutrient distribution and long‐term physiology in Drosophila

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94477/1/acel864.pd

Sestrins are evolutionarily conserved mediators of exercise benefits.

Exercise is among the most effective interventions for age-associated mobility decline and metabolic dysregulation. Although long-term endurance exercise promotes insulin sensitivity and expands respiratory capacity, genetic components and pathways mediating the metabolic benefits of exercise have remained elusive. Here, we show that Sestrins, a family of evolutionarily conserved exercise-inducible proteins, are critical mediators of exercise benefits. In both fly and mouse models, genetic ablation of Sestrins prevents organisms from acquiring metabolic benefits of exercise and improving their endurance through training. Conversely, Sestrin upregulation mimics both molecular and physiological effects of exercise, suggesting that it could be a major effector of exercise metabolism. Among the various targets modulated by Sestrin in response to exercise, AKT and PGC1α are critical for the Sestrin effects in extending endurance. These results indicate that Sestrin is a key integrating factor that drives the benefits of chronic exercise to metabolism and physical endurance

A Phenotypically Robust Model of Spinal and Bulbar Muscular Atrophy in Drosophila

Spinal and bulbar muscular atrophy (SBMA) is an X-linked disorder that affects males who inherit the androgen receptor (AR) gene with an abnormal CAG triplet repeat expansion. The resulting protein contains an elongated polyglutamine (polyQ) tract and causes motor neuron degeneration in an androgen-dependent manner. The precise molecular sequelae of SBMA are unclear. To assist with its investigation and the identification of therapeutic options, we report here a new model of SBMA in Drosophila melanogaster. We generated transgenic flies that express the full-length, human AR with a wild-type or pathogenic polyQ repeat. Each transgene is inserted into the same safe harbor site on the third chromosome of the fly as a single copy and in the same orientation. Expression of pathogenic AR, but not of its wild-type variant, in neurons or muscles leads to consistent, progressive defects in longevity and motility that are concomitant with polyQ-expanded AR protein aggregation and reduced complexity in neuromuscular junctions. Additional assays show adult fly eye abnormalities associated with the pathogenic AR species. The detrimental effects of pathogenic AR are accentuated by feeding flies the androgen, dihydrotestosterone. This new, robust SBMA model can be a valuable tool toward future investigations of this incurable disease

Sestrins are evolutionarily conserved mediators of exercise benefits

Exercise is among the most effective interventions for age-associated mobility decline and metabolic dysregulation. Although long-term endurance exercise promotes insulin sensitivity and expands respiratory capacity, genetic components and pathways mediating the meta- bolic benefits of exercise have remained elusive. Here, we show that Sestrins, a family of evolutionarily conserved exercise-inducible proteins, are critical mediators of exercise ben- efits. In both fly and mouse models, genetic ablation of Sestrins prevents organisms from acquiring metabolic benefits of exercise and improving their endurance through training. Conversely, Sestrin upregulation mimics both molecular and physiological effects of exercise, suggesting that it could be a major effector of exercise metabolism. Among the various targets modulated by Sestrin in response to exercise, AKT and PGC1α are critical for the Sestrin effects in extending endurance. These results indicate that Sestrin is a key integrating factor that drives the benefits of chronic exercise to metabolism and physical endurance

Conserved Exercise Pathways In Drosophila Melanogaster

Deciphering mechanisms by which exercise promotes health is of wide-ranging biomedical importance. The prevalence of cancers and cardiovascular, metabolic, and neurodegenerative diseases has increased dramatically. The negative impact of these ailments and their complications take a huge toll on the overall health of the population and the economy. While regular exercise remains the most powerful intervention known, we understand very little about the underlying molecular mechanisms. This knowledge gap has limited development of effective strategies to prevent and treat these diseases. We developed a protocol for inducing endurance training in Drosophila. The system relies on a machine that induces a behavioral instinct to respond to a sudden drop by running upward (negative geotaxis). This training machine, known as the Power Tower, can induce continuous running in several hundred vials of flies simultaneously. Flies continue to respond for as long as the machine is activated. We have defined a gradual, ramped endurance program that induces several responses that are similar to the physiological changes that occur in exercised vertebrates. These changes include increased mitochondrial activity, increased time to fatigue, increased running speed, increased cardiac stress resistance, improved oxidative metabolism and increased cardiac contractile strength. We have identified the PGC1 homolog spargel, the stress-response protein Sestrin, and the invertebrate orthologue of norepinephrine, octopamine, as requirements for maximal exercise benefits, supporting a conserved adaptation mechanism. We use this model to quantitatively evaluate training outcomes during both normal aging and age-related disease. Furthermore, we have leveraged our exercise model and the discovery of these conserved factors to investigate the potential impact of exercise on loss of mobility and early mortality in Drosophila melanogaster models of three polyQ disorders, SCA2, SCA3 and SCA6. Excitingly, we find that daily exercise differentially affects these SCAs, increasing motility and reducing early mortality in SCA2 model flies, and conferring modest improvement in SCA6. In addition, we find that exercise reduces disease protein in SCA2 model flies, and that these benefits can be replicated with Sestrin overexpression, even in flies that do not undergo training. This work provides the foundation for further investigations that will explore the protective role of exercise during physiological aging and across the spectrum of polyQ diseases, opening the door for the development of targeted therapeutics

Exercise and Sestrin Mediate Speed and Lysosomal Activity in Drosophila by Partially Overlapping Mechanisms

Chronic exercise is widely recognized as an important contributor to healthspan in humans and in diverse animal models. Recently, we have demonstrated that Sestrins, a family of evolutionarily conserved exercise-inducible proteins, are critical mediators of exercise benefits in flies and mice. Knockout of Sestrins prevents exercise adaptations to endurance and flight in Drosophila, and similarly prevents benefits to endurance and metabolism in exercising mice. In contrast, overexpression of dSestrin in muscle mimics several of the molecular and physiological adaptations characteristic of endurance exercise. Here, we extend those observations to examine the impact of dSestrin on preserving speed and increasing lysosomal activity. We find that dSestrin is a critical factor driving exercise adaptations to climbing speed, but is not absolutely required for exercise to increase lysosomal activity in Drosophila. The role of Sestrin in increasing speed during chronic exercise requires both the TORC2/AKT axis and the PGC1α homolog spargel, while dSestrin requires interactions with TORC1 to cell-autonomously increase lysosomal activity. These results highlight the conserved role of Sestrins as key factors that drive diverse physiological adaptations conferred by chronic exercise

Octopamine Drives Endurance Exercise Adaptations in Drosophila

Summary: Endurance exercise is an effective therapeutic intervention with substantial pro-healthspan effects. Male Drosophila respond to a ramped daily program of exercise by inducing conserved physiological responses similar to those seen in mice and humans. Female flies respond to an exercise stimulus but do not experience the adaptive training response seen in males. Here, we use female flies as a model to demonstrate that differences in exercise response are mediated by differences in neuronal activity. The activity of octopaminergic neurons is specifically required to induce the conserved cellular and physiological changes seen following endurance training. Furthermore, either intermittent, scheduled activation of octopaminergic neurons or octopamine feeding is able to fully substitute for exercise, conferring a suite of pro-healthspan benefits to sedentary Drosophila. These experiments indicate that octopamine is a critical mediator of adaptation to endurance exercise in Drosophila. : Chronic exercise causes stereotypical adaptations in muscle and adipose tissue of Drosophila. Sujkowski et al. show that these adaptations require the activity of octopaminergic neurons. Differences in octopaminergic activity control sexual dimorphism in exercise response. Both octopamine feeding and stimulation of octopaminergic neurons can substitute for endurance exercise. Keywords: Drosophila, exercise, octopamine, adaptation, endurance, negative geotaxis, sexual dimorphis

Octopamine Drives Endurance Exercise Adaptations in Drosophila

Summary: Endurance exercise is an effective therapeutic intervention with substantial pro-healthspan effects. Male Drosophila respond to a ramped daily program of exercise by inducing conserved physiological responses similar to those seen in mice and humans. Female flies respond to an exercise stimulus but do not experience the adaptive training response seen in males. Here, we use female flies as a model to demonstrate that differences in exercise response are mediated by differences in neuronal activity. The activity of octopaminergic neurons is specifically required to induce the conserved cellular and physiological changes seen following endurance training. Furthermore, either intermittent, scheduled activation of octopaminergic neurons or octopamine feeding is able to fully substitute for exercise, conferring a suite of pro-healthspan benefits to sedentary Drosophila. These experiments indicate that octopamine is a critical mediator of adaptation to endurance exercise in Drosophila. : Chronic exercise causes stereotypical adaptations in muscle and adipose tissue of Drosophila. Sujkowski et al. show that these adaptations require the activity of octopaminergic neurons. Differences in octopaminergic activity control sexual dimorphism in exercise response. Both octopamine feeding and stimulation of octopaminergic neurons can substitute for endurance exercise. Keywords: Drosophila, exercise, octopamine, adaptation, endurance, negative geotaxis, sexual dimorphis

Variation in mobility and exercise adaptations between Drosophila species

Locomotion and mobility have been studied extensively in Drosophila melanogaster but less is known about the locomotor capacity of other Drosophila species, while the response to chronic exercise in other species has yet to be examined. We have shown that adult male D. melanogaster adapt to exercise training with improved running endurance, climbing speed, and flight ability compared to unexercised flies. Here, we examine baseline mobility of D. sechellia, D. simulans, and D. virilis, and their response to chronic exercise training. We found significant interspecific differences in mobility and in the response to exercise. Although there is a significant sex difference in exercise adaptations in D. melanogaster, intraspecific analysis reveals few sex differences in other Drosophila species. As octopamine has been shown to be important for exercise adaptations in D. melanogaster, we also asked if any observed differences could be attributed to baseline octopamine levels. We find that octopamine and tyramine levels have the same rank order as baseline climbing speed and endurance in males, but do not predict the response to chronic exercise in males or females. Future research should focus on determining the mechanisms responsible for the inter- and intraspecific differences in mobility and the response to exercise.publishe

Delayed Induction of Human NTE (PNPLA6) Rescues Neurodegeneration and Mobility Defects of Drosophila swiss cheese (sws) Mutants.

Human PNPLA6 gene encodes Neuropathy Target Esterase protein (NTE). PNPLA6 gene mutations cause hereditary spastic paraplegia (SPG39 HSP), Gordon-Holmes syndrome, Boucher-Neuhäuser syndromes, Laurence-Moon syndrome, and Oliver-McFarlane syndrome. Mutations in the Drosophila NTE homolog swiss cheese (sws) cause early-onset, progressive behavioral defects and neurodegeneration characterized by vacuole formation. We investigated sws5 flies and show for the first time that this allele causes progressive vacuolar formation in the brain and progressive deterioration of negative geotaxis speed and endurance. We demonstrate that inducible, neuron-specific expression of full-length human wildtype NTE reduces vacuole formation and substantially rescues mobility. Indeed, neuron-specific expression of wildtype human NTE is capable of rescuing mobility defects after 10 days of adult life at 29°C, when significant degeneration has already occurred, and significantly extends longevity of mutants at 25°C. These results raise the exciting possibility that late induction of NTE function may reduce or ameliorate neurodegeneration in humans even after symptoms begin. In addition, these results highlight the utility of negative geotaxis endurance as a new assay for longitudinal tracking of degenerative phenotypes in Drosophila