Dietary Fatty Acids and Temperature Modulate Mitochondrial Function and Longevity in Drosophila

Evolution and development of Drosophila melanogaster under different thermal conditions affected cell sizes and sensitivity to paralyzing hypoxia

Environmental gradients cause evolutionary and developmental changes in the cellular composition of organisms, but the physiological consequences of these effects are not well understood. Here, we studied experimental populations of Drosophila melanogaster that had evolved in one of three selective regimes: constant 16 °C, constant 25 °C, or intergenerational shifts between 16 °C and 25 °C. Genotypes from each population were reared at three developmental temperatures (16 °C, 20.5 °C, and 25 °C). As adults, we measured thorax length and cell sizes in the Malpighian tubules and wing epithelia of flies from each combination of evolutionary and developmental temperatures. We also exposed flies from these treatments to a short period of nearly complete oxygen deprivation to measure hypoxia tolerance. For genotypes from any selective regime, development at a higher temperature resulted in smaller flies with smaller cells, regardless of the tissue. At every developmental temperature, genotypes from the warm selective regime had smaller bodies and smaller wing cells but had larger tubule cells than did genotypes from the cold selective regime. Genotypes from the fluctuating selective regime were similar in size to those from the cold selective regime, but their cells of either tissue were the smallest among the three regimes. Evolutionary and developmental treatments interactively affected a fly's sensitivity to short-term paralyzing hypoxia. Genotypes from the cold selective regime were less sensitive to hypoxia after developing at a higher temperature. Genotypes from the other selective regimes were more sensitive to hypoxia after developing at a higher temperature. Our results show that thermal conditions can trigger evolutionary and developmental shifts in cell size, coupled with changes in body size and hypoxia tolerance. These patterns suggest links between the cellular composition of the body, levels of hypoxia within cells, and the energetic cost of tissue maintenance. However, the patterns can be only partially explained by existing theories about the role of cell size in tissue oxygenation and metabolic performance.

Larval diet impacts black soldier fly (Diptera: Stratiomyidae) thermal tolerance and preference

Thermal tolerance and preference are key parameters impacting agricultural production systems. In this study, the impact of larval diet on black soldier fly thermal tolerance and preference across life-stages and sexes was examined. Larvae were fed either a low-protein high-carbohydrate synthetic diet (i.e., P7C35), a high-protein low-carbohydrate synthetic diet (i.e., P35C7), or the Gainesville diet (i.e., C) as a control and reference. Our results demonstrate that the impacts of larval diet on black soldier fly thermal tolerance and preference could be stage and sex specific. The mean heat knockdown temperatures (HKT) ranged between 46.6 and 47.9 °C. Synthetic diets resulted in greater HKT and the difference decreased form larvae (e.g., ∼1 °C) to adults (e.g., ∼0.2 °C). The mean chill-coma recovery time (CCRT) ranged between 8.3 and 21.6 min. Not much differences were detected between diets, but CCRT became longer from larvae to adults. The mean thermal preference ranged between 13.6 and 29.5 °C. Larvae fed synthetic diets preferred much lower temperatures than the control diet. A bimodal distribution was observed for adults regardless of sex. Differences on body mass, lipid, and protein contents were detected among diets; however, more research should be done before any conclusions can be linked to their thermal traits. These findings highlight the importance of considering the ingredients and nutritional makeup of larval diets when optimizing temperature management protocols for mass production of black soldier flies. Conversely, specific diets can be developed to promote survival under extreme rearing temperatures.

The untapped potential of cold water therapy as part of a lifestyle intervention for promoting healthy aging

Healthy aging is a crucial goal in aging societies of the western world, with various lifestyle strategies being employed to achieve it. Among these strategies, hydrotherapy stands out for its potential to promote cardiovascular and mental health. Cold water therapy, a hydrotherapy technique, has emerged as a lifestyle strategy with the potential capacity to evoke a wide array of health benefits. This review aims to synthesize the extensive body of research surrounding cold water therapy and its beneficial effects on various health systems as well as the underlying biological mechanisms driving these benefits. We conducted a search for interventional and observational cohort studies from MEDLINE and EMBASE up to July 2024. Deliberate exposure of the body to cold water results in distinct physiological responses that may be linked to several health benefits. Evidence, primarily from small interventional studies, suggests that cold water therapy positively impacts cardiometabolic risk factors, stimulates brown adipose tissue and promotes energy expenditure-potentially reducing the risk of cardiometabolic diseases. It also triggers the release of stress hormones, catecholamines and endorphins, enhancing alertness and elevating mood, which may alleviate mental health conditions. Cold water therapy also reduces inflammation, boosts the immune system, promotes sleep and enhances recovery following exercise. The optimal duration and temperature needed to derive maximal benefits is uncertain but current evidence suggests that short-term exposure and lower temperatures may be more beneficial. Overall, cold water therapy presents a potential lifestyle strategy to enhancing physical and mental well-being, promoting healthy aging and extending the healthspan, but definitive interventional evidence is warranted.

Protocol to build a drug-testing pipeline using large populations of Drosophila melanogaster

As a small animal that recapitulates many fundamental aspects of human disease, Drosophila lends itself to probing the biological activity of molecules and drug candidates. Here, we present a protocol to build a drug-testing pipeline in Drosophila. We describe steps for generating synchronous populations of Bicaudal C mutants by genetic crossing and wild-type fly culturing for controlled compound administration and exemplary phenotypic assays. For complete details on the use and execution of this protocol, please refer to Millet-Boureima et al.,1 Millet-Boureima et al.,2 and Gamberi et al.3.

Time-dependent metabolome and fatty acid profile changes following a high-fat diet exposure in Drosophila melanogaster

High-fat diets (HFDs) are often used to study metabolic disorders using different animal models. However, the underlying cellular mechanisms pertaining to the concurrent loss of metabolic homeostasis characteristics of these disorders are still unclear mainly because the effects of such diets are also dependent on the time frame of the experiments. Here, we used the fruit fly, Drosophila melanogaster, to investigate the metabolic dynamic effects following 0, 2, 4, 7 and 9 days of an exposure to a HFD (standard diet supplemented with 20% w/v coconut oil, rich in 12:0 and 14:0) by combining NMR metabolomics and GC-FID fatty acid profiling. Our results show that after 2 days, the ingested 12:0 and 14:0 fatty acids are used for both lipogenesis and fatty acid oxidation. After 4 days, metabolites from several different pathways are highly modulated in response to the HFD, and an accumulation of 12:0 is also observed, suggesting that the balance of lipid, amino acid and carbohydrate metabolism is profoundly perturbed at this specific time point. Following a longer exposure to the HFD (and notably after 9 days), an accumulation of many metabolites is observed indicating a clear dysfunction of the metabolic system. Overall, our study highlights the relevance of the Drosophila model to study metabolic disorders and the importance of the duration of the exposure to a HFD to study the dynamics of the fundamental mechanisms that control metabolism following exposure to dietary fats. This knowledge is crucial to understand the development and progression of metabolic diseases.

Antioxidant Activity of Hemp (Cannabis sativa L.) Seed Oil in Drosophila melanogaster Larvae under Non-Stress and H2O2-Induced Oxidative Stress Conditions

The oil extracted from hemp seeds has significant nutritional and biological properties due to the unique composition of polyunsaturated fatty acids and various antioxidant compounds. The potential of this oil for the prevention of oxidative stress and for the treatment of oxidative-stress-induced ailments is of increasing interest. Most studies of hemp seed oil were conducted in-vitro, meaning we lack information about effects and activity in vivo. In the present study, we evaluated the hypothesis that hemp seed oil at different concentrations improves the oxidative state of D. melanogaster, under non-stress as well as hydrogen-peroxide-induced stress. We analyzed the effects of hemp seed oil on oxidative stress markers and on the life cycle of D.melanogaster under non-stress and hydrogen-peroxide-induced stress conditions. D.melanogaster larvae were exposed to hemp seed oil concentrations ranging from 12.5 to 125 μL/mL. The results revealed that under non-stress conditions, oil concentrations up to 62.5 µL/mL did not induce negative effects on the life cycle of D. melanogaster and maintained the redox status of the larval cells at similar levels to the control level. Under oxidative stress conditions, biochemical parameters were significantly affected and only two oil concentrations, 18.7 and 31.2 µL/mL, provided protection against hydrogen peroxide stress effects. A higher oil concentration (125 μL/mL) exerted negative effects on the oxidative status and increased larval mortality. The tested oil was characterized chemically by NMR, transesterification, and silylation, followed by GC-MS analyses, and was shown to contain polyunsaturated fatty acid triglycerides and low levels of tocopherols. The high levels of linoleic and linolenic acids in the oil are suggested to be responsible for the observed in vivo antioxidant effects. Taken together, the results show that hemp seed oil is effective for reducing oxidative stress at the cellular level, thus supporting the hypothesis. The obtained results point to the potential of hemp seed oil for the prevention and treatment of conditions caused by the action of reactive oxygen species.

Breaking free from thermodynamic constraints: thermal acclimation and metabolic compensation in a freshwater zooplankton species

Respiration rates of ectothermic organisms are affected by environmental temperatures, and sustainable metabolism at high temperatures sometimes limits heat tolerance. Organisms are hypothesized to exhibit acclimatory metabolic compensation effects, decelerating their metabolic processes below Arrhenius expectations based on temperature alone. We tested the hypothesis that either heritable or plastic heat tolerance differences can be explained by metabolic compensation in the eurythermal freshwater zooplankton crustacean Daphnia magna We measured respiration rates in a ramp-up experiment over a range of assay temperatures (5-37°C) in eight genotypes of D. magna representing a range of previously reported acute heat tolerances and, at a narrower range of temperatures (10-35°C), in D. magna with different acclimation history (either 10 or 25°C). We discovered no difference in temperature-specific respiration rates between heat-tolerant and heat-sensitive genotypes. In contrast, we observed acclimation-specific compensatory differences in respiration rates at both extremes of the temperature range studied. Notably, there was a deceleration of oxygen consumption at higher temperature in 25°C-acclimated D. magna relative to their 10°C-acclimated counterparts, observed in active animals, a pattern corroborated by similar changes in filtering rate and, partly, by changes in mitochondrial membrane potential. A recovery experiment indicated that the reduction of respiration was not caused by irreversible damage during exposure to a sublethal temperature. Response time necessary to acquire the respiratory adjustment to high temperature was lower than for low temperature, indicating that metabolic compensation at lower temperatures requires slower, possibly structural changes.

Evolution of coding sequence and gene expression of blowflies and botflies with contrasting feeding habits

The Oestroidea superfamily is characterized by the diversity of feeding preferences among closely-related species; these flies are saprophagous, obligate parasites, or facultative parasites. We used gene expression and coding sequence data from five species (Cochliomyia hominivorax, Chrysomya megacephala, Lucilia cuprina, Dermatobia hominis, and Oestrus ovis) to identify underlying genetic differences involved in the diverse lifestyles. We tested whether 1287 orthologs have different expression and evolutionary constraints under different scenarios. We found two up-regulated genes; one in species causing cutaneous myiasis that is involved in iron transportation/metabolization (ferritin), and another in species causing traumatic myiasis that responds to reduced oxygen levels (anoxia up-regulated-like). Our evolutionary analysis showed a similar result. In the Co. hominivorax branch, we found one gene with the same function as ferritin that may be evolving under positive selection, spook. This is the first step towards understanding origins and evolution of parasitic strategy diversity in Oestroidea.

Dietary yeast influences ethanol sedation in Drosophila via serotonergic neuron function

Abuse of alcohol is a major clinical problem with far-reaching health consequences. Understanding the environmental and genetic factors that contribute to alcohol-related behaviors is a potential gateway for developing novel therapeutic approaches for patients that abuse the drug. To this end, we have used Drosophila melanogaster as a model to investigate the effect of diet, an environmental factor, on ethanol sedation. Providing flies with diets high in yeast, a routinely used component of fly media, increased their resistance to ethanol sedation. The yeast-induced resistance to ethanol sedation occurred in several different genetic backgrounds, was observed in males and females, was elicited by yeast from different sources, was readily reversible, and was associated with increased nutrient intake as well as decreased internal ethanol levels. Inhibition of serotonergic neuron function using multiple independent genetic manipulations blocked the effect of yeast supplementation on ethanol sedation, nutrient intake, and internal ethanol levels. Our results demonstrate that yeast is a critical dietary component that influences ethanol sedation in flies and that serotonergic signaling is required for the effect of dietary yeast on nutrient intake, ethanol uptake/elimination, and ethanol sedation. Our studies establish the fly as a model for diet-induced changes in ethanol sedation and raise the possibility that serotonin might mediate the effect of diet on alcohol-related behavior in other species.

The cuticle inward barrier in Drosophila melanogaster is shaped by mitochondrial and nuclear genotypes and a sex-specific effect of diet

An important role of the insect cuticle is to prevent wetting (i.e., permeation of water) and also to prevent penetration of potentially harmful substances. This barrier function mainly depends on the hydrophobic cuticle surface composed of lipids including cuticular hydrocarbons (CHCs). We investigated to what extent the cuticle inward barrier function depends on the genotype, comprising mitochondrial and nuclear genes in the fruit fly Drosophila melanogaster, and investigated the contribution of interactions between mitochondrial and nuclear genotypes (mito-nuclear interactions) on this function. In addition, we assessed the effects of nutrition and sex on the cuticle barrier function. Based on a dye penetration assay, we find that cuticle barrier function varies across three fly lines that were captured from geographically separated regions in three continents. Testing different combinations of mito-nuclear genotypes, we show that the inward barrier efficiency is modulated by the nuclear and mitochondrial genomes independently. We also find an interaction between diet and sex. Our findings provide new insights into the regulation of cuticle inward barrier function in nature.

Molecular basis for efficacy of Guduchi and Madhuyashti feeding on different environmental stressors in Drosophila

Stressors of different kinds adversely affect life history parameters like growth, development, and reproduction. Organisms overcome the negative impact of environmental stressors and strive to reach a tolerant state through genetic and metabolic activities. Ayurvedic formulations are reported to have life trait benefitting properties which improve capacity to withstand stress and tolerate adverse conditions. Guduchi (Tinospora cordifolia) and Madhuyashti (Glycirrhiza glabra) Ayurvedic formulations are known to have immunomodulatory, intellect promoting, and adaptogenic properties, thus favoring good health and healthy aging. Present study investigates the efficacy of Guduchi and Madhuyashti in providing tolerance to different stresses and the underlying mechanisms using the Drosophila model. Drosophila larvae/flies fed on Guduchi or Madhuyashti were better thermo-protected, which correlated with increased expression of heat shock genes even without the heat shock. Guduchi or Madhuyashti feeding also increased antimicrobial peptide expression, thus providing better tolerance to pathogenic assaults. Feeding on Guduchi- or Madhuyashti- supplemented food also enhanced starvation and desiccation tolerance. However, neither of these formulations provided beneficial effects when grown under crowded conditions or when exposed to oxidative stressors.

Omega-3 Monoacylglyceride Effects on Longevity, Mitochondrial Metabolism and Oxidative Stress: Insights from Drosophila melanogaster

During the last decade, essential polyunsaturated fatty acids (PUFAs) such as eicosatetraenoic acid (EPA) and docosahexaenoic acid (DHA) derived from marine sources have been investigated as nonpharmacological dietary supplements to improve different pathological conditions, as well as aging. The aim of this study was to determine the effects of dietary n-3 PUFA monoacylglycerides (MAG, both EPA and DHA) on the mitochondrial metabolism and oxidative stress of a short-lifespan model, Drosophila melanogaster, sampled at five different ages. Our results showed that diets supplemented with MAG-EPA and MAG-DHA increased median lifespan by 14.6% and decreased mitochondrial proton leak resulting in an increase of mitochondrial coupling. The flies fed on MAG-EPA also had higher electron transport system capacity and mitochondrial oxidative capacities. Moreover, both n-3 PUFAs delayed the occurrence of lipid peroxidation but only flies fed the MAG-EPA diet showed maintenance of superoxide dismutase activity during aging. Our study therefore highlights the potential of n-3 PUFA monoacylglycerides as nutraceutical compounds to delay the onset of senescence by acting directly or indirectly on the mitochondrial metabolism and suggests that Drosophila could be a relevant model for the study of the fundamental mechanisms linking the effects of n-3 PUFAs to aging.

Measurement of solid food intake in Drosophila via consumption-excretion of a dye tracer

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.

Dietary management and physical exercise can improve climbing defects and mitochondrial activity in Drosophila melanogaster parkin null mutants

Physical exercise can improve gait, balance, tremor, flexibility, grip strength and motor coordination in Parkinson's disease (PD) patients. Several lines of evidence have also shown the therapeutic potential of dietary management and supplementation in halting the progression of PD. However, there is a lack of research on the combined effects of physical activity and nutrition in the progression of PD. We test the effects exercise and dietary modification in a Drosophila model of PD. In this study, we fed Drosophila parkin mutants high protein and high carbohydrate diets without and with stearic acid (4 treatments in total). In parallel, we subjected mutants to a regimen of exercise using a purpose-built 'Power tower' exercise machine. We then measured climbing ability, aconitase activity, and basal mitochondrial ROS levels. We observed that exercising parkin mutants fed the high protein diet improved their climbing ability and increased aconitase activity. There was an additional improvement in climbing and aconitase activity in exercised parkin mutants fed the high protein diet supplemented with stearic acid. No benefits of exercise were seen in parkin mutants fed the high carbohydrate diet. Combined, these results suggest that dietary management along with physical activty has potential to improve mitochondrial biogenesis and delay the progression of PD in Drosophila parkin mutants.

Drosophila Gr64e mediates fatty acid sensing via the phospholipase C pathway

Animals use taste to sample and ingest essential nutrients for survival. Free fatty acids (FAs) are energy-rich nutrients that contribute to various cellular functions. Recent evidence suggests FAs are detected through the gustatory system to promote feeding. In Drosophila, phospholipase C (PLC) signaling in sweet-sensing cells is required for FA detection but other signaling molecules are unknown. Here, we show Gr64e is required for the behavioral and electrophysiological responses to FAs. GR64e and TRPA1 are interchangeable when they act downstream of PLC: TRPA1 can substitute for GR64e in FA but not glycerol sensing, and GR64e can substitute for TRPA1 in aristolochic acid but not N-methylmaleimide sensing. In contrast to its role in FA sensing, GR64e functions as a ligand-gated ion channel for glycerol detection. Our results identify a novel FA transduction molecule and reveal that Drosophila Grs can act via distinct molecular mechanisms depending on context.

Fatty acids (FAs) are energy-rich nutrients that are detected through the gustatory system to promote feeding. Here, we show FA detection requires a Drosophila gustatory receptor, Gr64e. Although GR64e functions as a ligand-gated ion channel for glycerol detection, in FA sensing, it acts downstream of phospholipase C signaling. We identified a novel signaling molecule for FA sensing in Drosophila. Furthermore, our findings suggest Drosophila GRs have multiple modes of action depending on their cellular and molecular context.

The 4E-BP growth pathway regulates the effect of ambient temperature on Drosophila metabolism and lifespan

Changes in body temperature can profoundly affect survival. The dramatic longevity-enhancing effect of cold has long been known in organisms ranging from invertebrates to mammals, yet the underlying mechanisms have only recently begun to be uncovered. In the nematode Caenorhabditis elegans, this process is regulated by a thermosensitive membrane TRP channel and the DAF-16/FOXO transcription factor, but in more complex organisms the underpinnings of cold-induced longevity remain largely mysterious. We report that, in Drosophila melanogaster, variation in ambient temperature triggers metabolic changes in protein translation, mitochondrial protein synthesis, and posttranslational regulation of the translation repressor, 4E-BP (eukaryotic translation initiation factor 4E-binding protein). We show that 4E-BP determines Drosophila lifespan in the context of temperature changes, revealing a genetic mechanism for cold-induced longevity in this model organism. Our results suggest that the 4E-BP pathway, chiefly thought of as a nutrient sensor, may represent a master metabolic switch responding to diverse environmental factors.

The Mitochondria-Targeted Plastoquinone-Derivative SkQ1 Promotes Health and Increases Drosophila melanogaster Longevity in Various Environments

Mitochondria play an important role in aging. Strongly reduced function of the mitochondria shortens life span, whereas moderate reduction prolongs life span, with reactive oxygen species production being the major factor contributing to life span changes. Previously, picomolar concentrations of the mitochondria-targeted antioxidant SkQ1 were shown to increase the life span of Drosophila by approximately 10%. In this article, we demonstrate that SkQ1 elevates locomotion, which is often considered a marker of health and age. We also show that mating frequency and fecundity may be slightly increased in SkQ1-treated flies. These results indicate that SkQ1 not only prolongs life span but also improves health and vigor. An important property of any potential therapeutic is the stability of its effects in an uncontrolled and changing environment as well as on individuals with various genetic constitutions. In this article, we present data on SkQ1 effects on Drosophila longevity in extreme environments (low temperatures and starvation) and on individuals with severe genetic alterations in the mitochondrial systems responsible for production and detoxification of reactive oxygen species. We hypothesize that in vivo SkQ1 is capable of alleviating the probable negative effects of increased mitochondrial reactive oxygen species production on longevity but is not effective when reactive oxygen species production is already reduced by other means.

OXIDIZED LIPIDS DID NOT REDUCE LIFESPAN IN THE FRUIT FLY, Drosophila melanogaster

Aging is often associated with accumulation of oxidative damage in proteins and lipids. However, some studies do not support this view, raising the question of whether high levels of oxidative damage are associated with lifespan. In the current investigation, Drosophila melanogaster flies were kept on diets with 2 or 10% of either glucose or fructose. The lifespan, fecundity, and feeding as well as amounts of protein carbonyls (PC) and lipid peroxides (LOOH), activities of superoxide dismutase (SOD), catalase, glutathione-S-transferase (GST), and glutathione reductase activity of thioredoxin reductase (TrxR) were measured in "young" (10-day old) and "aged" (50-day old) flies. Flies maintained on diets with 10% carbohydrate lived longer than those on the 2% diets. However, neither lifespan nor fecundity was affected by the type of carbohydrate. The amount of PC was unaffected by diet and age, whereas flies fed on diets with 10% carbohydrate had about fivefold higher amounts of LOOH compared to flies maintained on the 2% carbohydrate diets. Catalase activity was significantly lower in flies fed on diets with 10% carbohydrates compared to flies on 2% carbohydrate diets. The activities of SOD, GST, and TrxR were not affected by the diet or age of the flies. The higher levels of LOOH in flies maintained on 10% carbohydrate did not reduce their lifespan, from which we infer that oxidative damage to only one class of biomolecules, particularly lipids, is not sufficient to influence lifespan.