Counting calories in Drosophila diet restriction

Response of fruit fly (Drosophila pseudoobscura) to diet manipulation of nutrient density

Caloric intake can greatly affect many aspects of an organism's life. A deficiency of calories can lead to stress resulting in decreased fecundity, insufficient calories to maintain tissues and increased lifespan. Conversely, increasing caloric density increases fecundity and decreases lifespan. Despite decades of work exploring food quality and quantity on physiology in the model species Drosophila melanogaster Meigan 1830 (Diptera: Drosophilidae) and the melanogaster group in general, relatively little work explores the physiological responses to diet manipulation in other Drosophila species, like the obscura species group. Here, we looked at the effects of five different caloric densities (0.5×, 0.75×, 1.0×, 1.5× and 3.0×) on food intake, body weight, body fat, fecundity and longevity in D. pseudoobscura Frolova & Astaurov, 1929 (Diptera: Drosophilidae). Comparing longevity and fecundity across diets, we found that heavy caloric concentration (3.0×) decreases lifespan and that calorie restriction (0.5× and 0.75×) led to significant decreases in fecundity and body weight. However, calorie concentration did not significantly increase D. pseudoobscura body fat. By expanding our understanding of the physiological responses to diet stress to D. pseudoobscura, we establish the framework for comparative work across Drosophila species. With this information, we can then identify which physiological responses to diet manipulation might be most conserved and comparable across species.

GLP-1, GIP, and Glucagon Agonists for Obesity Treatment: A Hunger Perspective

For centuries, increasingly sophisticated methods and approaches have been brought to bear to promote weight loss. Second only to the Holy Grail of research on aging, the idea of finding a single and simple way to lose weight has long preoccupied the minds of laymen and scientists alike. The effects of obesity are far-reaching and not to be minimized; the need for more effective treatments is obvious. Is there a single silver bullet that addresses this issue without effort on the part of the individual? The answer to this question has been one of the most elusive and sought-after in modern history. Now and then, a miraculous discovery propagates the illusion that a simple solution is possible. Now there are designer drugs that seem to accomplish the task: we can lose weight without effort using mono, dual, and triple agonists of receptors for glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic peptide (GIP), and glucagon. There are, however, fundamental biological principles that raise intriguing questions about these therapies beyond the currently reported side-effects. This perspective reflects upon these issues from the angle of complex goal-oriented behaviors, and systemic and cellular metabolism associated with satiety and hunger.

Within-population plastic responses to combined thermal-nutritional stress differ from those in response to single stressors, and are genetically independent across traits in both males and females

Phenotypic plasticity helps animals to buffer the effects of increasing thermal and nutritional stress created by climate change. Plastic responses to single and combined stressors can vary among genetically diverged populations. However, less is known about how plasticity in response to combined stress varies among individuals within a population or whether such variation changes across life-history traits. This is important because individual variation within populations shapes population-level responses to environmental change. Here, we used isogenic lines of Drosophila melanogaster to assess the plasticity of egg-to-adult viability and sex-specific body size for combinations of 2 temperatures (25 °C or 28 °C) and 3 diets (standard diet, low caloric diet, or low protein:carbohydrate ratio diet). Our results reveal substantial within-population genetic variation in plasticity for egg-to-adult viability and wing size in response to combined thermal-nutritional stress. This genetic variation in plasticity was a result of cross-environment genetic correlations that were often < 1 for both traits, as well as changes in the expression of genetic variation across environments for egg-to-adult viability. Cross-sex genetic correlations for body size were weaker when the sexes were reared in different conditions, suggesting that the genetic basis of traits may change with the environment. Furthermore, our results suggest that plasticity in egg-to-adult viability is genetically independent from plasticity in body size. Importantly, plasticity in response to diet and temperature individually differed from plastic shifts in response to diet and temperature in combination. By quantifying plasticity and the expression of genetic variance in response to combined stress across traits, our study reveals the complexity of animal responses to environmental change, and the need for a more nuanced understanding of the potential for populations to adapt to ongoing climate change.

Dietary restriction fails to extend lifespan of Drosophila model of Werner syndrome

Werner syndrome (WS) is a rare genetic disease in humans, caused by mutations in the WRN gene that encodes a protein containing helicase and exonuclease domains. WS is characterized by symptoms of accelerated aging in multiple tissues and organs, involving increased risk of cancer, heart failure, and metabolic dysfunction. These conditions ultimately lead to the premature mortality of patients with WS. In this study, using the null mutant flies (WRNexoΔ) for the gene WRNexo (CG7670), homologous to the exonuclease domain of WRN in humans, we examined how diets affect the lifespan, stress resistance, and sleep/wake patterns of a Drosophila model of WS. We observed that dietary restriction (DR), one of the most robust nongenetic interventions to extend lifespan in animal models, failed to extend the lifespan of WRNexoΔ mutant flies and even had a detrimental effect in females. Interestingly, the mean lifespan of WRNexoΔ mutant flies was not reduced on a protein-rich diet compared to that of wild-type (WT) flies. Compared to WT control flies, the mutant flies also exhibited altered responses to DR in their resistance to starvation and oxidative stress, as well as changes in sleep/wake patterns. These findings show that the WRN protein is necessary for mediating the effects of DR and suggest that the exonuclease domain of WRN plays an important role in metabolism in addition to its primary role in DNA-repair and genome stability.

Household air pollution and risk of incident lung cancer in urban China: A prospective cohort study

Household air pollution (HAP) is associated with the development of lung cancer, yet few studies investigated the exposure patterns and joint associations with tobacco smoking. In our study, we included 224 189 urban participants from China Kadoorie Biobank (CKB), 3288 of which diagnosed with lung cancer during the follow-up. Exposure to four HAP sources (solid fuels for cooking/heating/stove and environmental tobacco smoke exposure) was assessed at baseline. Distinct HAP patterns and their associations with lung cancer were examined through latent class analysis (LCA) and multivariable Cox regression. A total of 76.1% of the participants reported regular cooking and 52.2% reported winter heating, of which 9% and 24.7% used solid fuels, respectively. Solid fuel heating increased lung cancer risk (Hazards ratio [HR]: 1.25, 95% confidence interval [CI]: 1.08-1.46). LCA identified three HAP patterns; the "clean fuel cooking and solid fuel heating" pattern significantly increased lung cancer risk (HR: 1.25, 95% CI: 1.10-1.41), compared to low HAP pattern. An additive interaction was observed between heavy smoking and "clean fuel cooking and solid fuel heating" (relative excess risk [RERI]: 1.32, 95% CI: 0.29-2.47, attributable proportion [AP]: 0.23, 95% CI: 0.06-0.36). Cases resulting from solid fuel account for ~4% of total cases (population attribute fraction [PAF]overall : 4.31%, 95% CI: 2.16%-6.47%, PAFever smokers : 4.38%, 95% CI: 1.54%-7.23%). Our results suggest that in urban China, solid fuel heating increased the risk of lung cancer, particularly among heavy smokers. The whole population could benefit from cleaner indoor air quality by reducing using solid fuels, especially smokers.

The remoulding of dietary effects on the fecundity / longevity trade-off in a social insect

BACKGROUND

In many organisms increased reproductive effort is associated with a shortened life span. This trade-off is reflected in conserved molecular pathways that link nutrient-sensing with fecundity and longevity. Social insect queens apparently defy the fecundity / longevity trade-off as they are both, extremely long-lived and highly fecund. Here, we have examined the effects of a protein-enriched diet on these life-history traits and on tissue-specific gene expression in a termite species of low social complexity.

RESULTS

On a colony level, we did not observe reduced lifespan and increased fecundity, effects typically seen in solitary model organisms, after protein enrichment. Instead, on the individual level mortality was reduced in queens that consumed more of the protein-enriched diet - and partially also in workers - while fecundity seemed unaffected. Our transcriptome analyses supported our life-history results. Consistent with life span extension, the expression of IIS (insulin/insulin-like growth factor 1 signalling) components was reduced in fat bodies after protein enrichment. Interestingly, however, genes involved in reproductive physiology (e.g., vitellogenin) were largely unaffected in fat body and head transcriptomes.

CONCLUSION

These results suggest that IIS is decoupled from downstream fecundity-associated pathways, which can contribute to the remoulding of the fecundity/longevity trade-off in termites as compared to solitary insects.

Dietary Restriction Impacts Peripheral Circadian Clock Output Important for Longevity in Drosophila

Circadian clocks may mediate lifespan extension by caloric or dietary restriction (DR). We find that the core clock transcription factor Clock is crucial for a robust longevity and fecundity response to DR in Drosophila. To identify clock-controlled mediators, we performed RNA-sequencing from abdominal fat bodies across the 24 h day after just 5 days under control or DR diets. In contrast to more chronic DR regimens, we did not detect significant changes in the rhythmic expression of core clock genes. Yet we discovered that DR induced de novo rhythmicity or increased expression of rhythmic clock output genes. Network analysis revealed that DR increased network connectivity in one module comprised of genes encoding proteasome subunits. Adult, fat body specific RNAi knockdown demonstrated that proteasome subunits contribute to DR-mediated lifespan extension. Thus, clock control of output links DR-mediated changes in rhythmic transcription to lifespan extension.

Gender-specific effects of pro-longevity interventions in Drosophila

Sex differences in lifespan are well recognized in the majority of animal species. For example, in male versus female Drosophila melanogaster there are significant differences in behavior and physiology. However, little is known about the underlying mechanisms of gender differences in responses to pro-longevity interventions in this model organism. Here we summarize the existing data on the effects of nutritional and pharmacological anti-aging interventions such as nutrition regimens, diet and dietary supplementation on the lifespan of male and female Drosophila. We demonstrate that males and females have different sensitivities to interventions and that the effects are highly dependent on genetic background, mating, dose and exposure duration. Our work highlights the importance of understanding the mechanisms that underlie the gender-specific effect of anti-aging manipulations. This will provide insight into how these benefits may be valuable for elucidating the primary physiological and molecular targets involved in aging and lifespan determination.

Epigenome-wide Association Study Analysis of Calorie Restriction in Humans, CALERIETM Trial Analysis

Calorie restriction (CR) increases healthy life span and is accompanied by slowing or reversal of aging-associated DNA methylation (DNAm) changes in animal models. In the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIETM) human trial, we evaluated associations of CR and changes in whole-blood DNAm. CALERIETM randomized 220 healthy, nonobese adults in a 2:1 allocation to 2 years of CR or ad libitum (AL) diet. The average CR in the treatment group through 24 months of follow-up was 12%. Whole blood (baseline, 12, and 24 months) DNAm profiles were measured. Epigenome-wide association study (EWAS) analysis tested CR-induced changes from baseline to 12 and 24 months in the n = 197 participants with available DNAm data. CR treatment was not associated with epigenome-wide significant (false discovery rate [FDR] < 0.05) DNAm changes at the individual-CpG-site level. Secondary analysis of sets of CpG sites identified in published EWAS revealed that CR induced DNAm changes opposite to those associated with higher body mass index and cigarette smoking (p < .003 at 12- and 24-month follow-ups). In contrast, CR altered DNAm at chronological-age-associated CpG sites in the direction of older age (p < .003 at 12- and 24-month follow-ups). Although individual CpG site DNAm changes in response to CR were not identified, analyses of sets CpGs identified in prior EWAS revealed CR-induced changes to blood DNAm. Altered CpG sets were enriched for insulin production, glucose tolerance, inflammation, and DNA-binding and DNA-regulation pathways, several of which are known to be modified by CR. DNAm changes may contribute to CR effects on aging.

Metabolic and immunological responses of Drosophila melanogaster to dietary restriction and bacterial infection differ substantially between genotypes in a population

To respond to changing environmental conditions, a population may either shift toward better‐adapted genotypes or adapt on an individual level. The present work aimed to quantify the relevance of these two processes by comparing the responses of defined Drosophila melanogaster populations to different stressors. To do this, we infected two homogeneous populations (isofemale lines), which differ significantly in fitness, and a synthetic heterogeneous population with a specific pathogen and/or exposed them to food restriction. Pectobacterium carotovorum was used to infect Drosophila larvae either fed standard or protein‐restricted diet. In particular, the two homogeneous groups, which diverged in their fitness, showed considerable differences in all parameters assessed (survivorship, protein and lipid contents, phenol‐oxidase (PO) activity, and antibacterial rate). Under fully nutritious conditions, larvae of the homogeneous population with low fitness exhibited lower survivorship and protein levels, as well as higher PO activity and antibacterial rate compared with the fitter population. A protein‐restricted diet and bacterial infection provoked a decrease in survivorship, and antibacterial rate in most populations. Bacterial infection elicited an opposite response in protein and lipid content in both isofemale lines tested. Interestingly, the heterogeneous population showed a complex response pattern. The response of the heterogeneous population followed the fit genotype in terms of survival and antibacterial activity but followed the unfit genotype in terms of PO activity. In conclusion, our results show that defined genotypes exhibit highly divergent responses to varying stressors that are difficult to predict. Furthermore, the responses of heterogeneous populations do not follow a fixed pattern showing a very high degree of plasticity and differences between different genotypes.

Amino acid quality modifies the quantitative availability of protein for reproduction in Drosophila melanogaster

Diet composition, especially the relative abundance of key macronutrients, is well known to affect animal wellbeing by changing reproductive output, metabolism and length of life. However, less attention has been paid to the ways the quality of these nutrients modify these macronutrient interactions. Nutritional Geometry can be used to model the effects of multiple dietary components on life-history traits and to compare these responses when diet quality is varied. Previous studies have shown that dietary protein quality can be increased for egg production in Drosophila melanogaster by matching the dietary amino acid proportions to the balance of amino acids used by the sum of proteins in the fly's in silico translated exome. Here, we show that dietary protein quality dramatically alters the effect of protein quantity on female reproduction across a broad range of diets varying in both protein and carbohydrate concentrations. These data show that when sources of ingredients vary, their relative value to the consumer can vastly differ and yield very different physiological outcomes. Such variations could be particularly important for meta analyses that look to draw generalisable conclusions from diverse studies.

The evolution of sex peptide: sexual conflict, cooperation, and coevolution

A central paradigm in evolutionary biology is that the fundamental divergence in the fitness interests of the sexes (‘sexual conflict’) can lead to both the evolution of sex‐specific traits that reduce fitness for individuals of the opposite sex, and sexually antagonistic coevolution between the sexes. However, clear examples of traits that evolved in this way – where a single trait in one sex demonstrably depresses the fitness of members of the opposite sex, resulting in antagonistic coevolution – are rare. The Drosophila seminal protein ‘sex peptide’ (SP) is perhaps the most widely cited example of a trait that appears to harm females while benefitting males. Transferred in the ejaculate by males during mating, SP triggers profound and wide‐ranging changes in female behaviour and physiology. Early studies reported that the transfer of SP enhances male fitness while depressing female fitness, providing the foundations for the widespread view that SP has evolved to manipulate females for male benefit. Here, we argue that this view is (i) a simplification of a wider body of contradictory empirical research, (ii) narrow with respect to theory describing the origin and maintenance of sexually selected traits, and (iii) hard to reconcile with what we know of the evolutionary history of SP's effects on females. We begin by charting the history of thought regarding SP, both at proximate (its production, function, and mechanism of action) and ultimate (its fitness consequences and evolutionary history) levels, reviewing how studies of SP were central to the development of the field of sexual conflict. We describe a prevailing paradigm for SP's evolution: that SP originated and continues to evolve to manipulate females for male benefit. In contrast to this view, we argue on three grounds that the weight of evidence does not support the view that receipt of SP decreases female fitness: (i) results from studies of SP's impact on female fitness are mixed and more often neutral or positive, with fitness costs emerging only under nutritional extremes; (ii) whether costs from SP are appreciable in wild‐living populations remains untested; and (iii) recently described confounds in genetic manipulations of SP raise the possibility that measures of the costs and benefits of SP have been distorted. Beyond SP's fitness effects, comparative and genetic data are also difficult to square with the idea that females suffer fitness costs from SP. Instead, these data – from functional and evolutionary genetics and the neural circuitry of female responses to SP – suggest an evolutionary history involving the evolution of a dedicated SP‐sensing apparatus in the female reproductive tract that is likely to have evolved because it benefits females, rather than harms them. We end by exploring theory and evidence that SP benefits females by functioning as a signal of male quality or of sperm receipt and storage (or both). The expanded view of the evolution of SP that we outline recognises the context‐dependent and fluctuating roles played by both cooperative and antagonistic selection in the origin and maintenance of reproductive traits.

Neurotensin Regulates Proliferation and Stem Cell Function in the Small Intestine in a Nutrient-Dependent Manner

BACKGROUND & AIMS

Intestinal stem cells (ISCs) are sensitive to dietary alterations and nutrient availability. Neurotensin (NT), a gut peptide localized predominantly to the small bowel and released by fat ingestion, stimulates the growth of intestinal mucosa under basal conditions and during periods of nutrient deprivation, suggesting a possible role for NT on ISC function.

METHODS

Leucine-rich repeat-containing G-protein coupled receptor 5-Enhanced Green Fluorescent Protein (Lgr5-EGFP) NT wild type (Nt^+/+) and Lgr5-EGFP NT knockout (Nt^-/-) mice were fed ad libitum or fasted for 48 hours. Small intestine tissue and crypts were examined by gene expression analyses, fluorescence-activated cell sorting, Western blot, immunohistochemistry, and crypt-derived organoid culture. Drosophila expressing NT in midgut enteroendocrine cells were fed a standard diet or low-energy diet and esg-green fluorescent protein⁺ ISCs were quantified via immunofluorescence.

RESULTS

Loss of NT impaired crypt cell proliferation and ISC function in a manner dependent on nutrient status. Under nutrient-rich conditions, NT stimulated extracellular signal-regulated kinases 1 and 2 signaling and the expression of genes that promote cell-cycle progression, leading to crypt cell proliferation. Under conditions of nutrient depletion, NT stimulated WNT/β-catenin signaling and promoted an ISC gene signature, leading to enhanced ISC function. NT was required for the induction of WNT/β-catenin signaling and ISC-specific gene expression during nutrient depletion, and loss of NT reduced crypt cell proliferation and impaired ISC function and Lgr5 expression in the intestine during fasting. Conversely, the expression of NT in midgut enteroendocrine cells of Drosophila prevented loss of ISCs during nutrient depletion.

CONCLUSIONS

Collectively, our findings establish an evolutionarily conserved role for NT in ISC maintenance during nutritional stress. GSE182828.

Identification of genetic modifiers of lifespan on a high sugar diet in the Drosophila Genetic Reference Panel

Genome-wide association studies (GWAS) have become beneficial in identifying genetic variants underlying susceptibility to various complex diseases and conditions, including obesity. Utilizing the Drosophila Genetic Reference Panel (DGRP), we performed a GWAS of lifespan of 193 genetically distinct lines on a high sugar diet (HSD). The DGRP analysis pipeline determined the most significant lifespan associated polymorphisms were within loci of genes involved in: neural processes, behavior, development, and apoptosis, among other functions. Next, based on the relevance to obesity pathology, and the availability of transgenic RNAi lines targeting the genes we identified, whole-body in vivo knockdown of several candidate genes was performed. We utilized the GAL4-UAS binary expression system to independently validate the impacts of these loci on Drosophila lifespan during HSD. These loci were largely confirmed to affect lifespan in that HSD setting, as well as a normal diet setting. However, we also detected unexpected dietary effects of the HSD, including inconsistent diet effects on lifespan relative to a normal diet and a strong downregulation of feeding quantity.

Experimental increase in fecundity causes upregulation of fecundity and body maintenance genes in the fat body of ant queens

In most organisms, fecundity and longevity are negatively associated and the molecular regulation of these two life-history traits is highly interconnected. In addition, nutrient intake often has opposing effects on lifespan and reproduction. In contrast to solitary insects, the main reproductive individual of social hymenopterans, the queen, is also the most long-lived. During development, queen larvae are well-nourished, but we are only beginning to understand the impact of nutrition on the queens' adult life and the molecular regulation and connectivity of fecundity and longevity. Here, we used two experimental manipulations to alter queen fecundity in the ant Temnothorax rugatulus and investigated associated changes in fat body gene expression. Egg removal triggered a fecundity increase, leading to expression changes in genes with functions in fecundity such as oogenesis and body maintenance. Dietary restriction lowered the egg production of queens and altered the expression of genes linked to autophagy, Toll signalling, cellular homeostasis and immunity. Our study reveals that an experimental increase in fecundity causes the co-activation of reproduction and body maintenance mechanisms, shedding light on the molecular regulation of the link between longevity and fecundity in social insects.

Life-History Evolution and the Genetics of Fitness Components in Drosophila melanogaster

Life-history traits or "fitness components"-such as age and size at maturity, fecundity and fertility, age-specific rates of survival, and life span-are the major phenotypic determinants of Darwinian fitness. Analyzing the evolution and genetics of these phenotypic targets of selection is central to our understanding of adaptation. Due to its simple and rapid life cycle, cosmopolitan distribution, ease of maintenance in the laboratory, well-understood evolutionary genetics, and its versatile genetic toolbox, the "vinegar fly" Drosophila melanogaster is one of the most powerful, experimentally tractable model systems for studying "life-history evolution." Here, I review what has been learned about the evolution and genetics of life-history variation in D. melanogaster by drawing on numerous sources spanning population and quantitative genetics, genomics, experimental evolution, evolutionary ecology, and physiology. This body of work has contributed greatly to our knowledge of several fundamental problems in evolutionary biology, including the amount and maintenance of genetic variation, the evolution of body size, clines and climate adaptation, the evolution of senescence, phenotypic plasticity, the nature of life-history trade-offs, and so forth. While major progress has been made, important facets of these and other questions remain open, and the D. melanogaster system will undoubtedly continue to deliver key insights into central issues of life-history evolution and the genetics of adaptation.

An overview of two decades of diet restriction studies using Drosophila

Dietary restriction (DR) is a potent forerunner in aging studies capable of influencing lifespan and improving health in various model organisms even in their old age. Despite the importance of protein and carbohydrates in the diet (regulation of fecundity and body maintenance respectively), different ratio based combinations of these components has played a major role in lifespan extension studies. In spite of differences existing in dietary protocols across laboratories, diet manipulations have evolved as a major area of research in Drosophila lifespan studies, prominently shedding light on the multi-faceted process over the last two decades. Here, we review various advances and technicalities involved in understanding the DR-mediated lifespan alongside discussing the pros and cons of various existing approaches/diets used across labs. The current review also focuses on the importance of life-stage specific DR implementation and their influence on the life-history traits including lifespan and fecundity, by taking examples of results from different studies comprising diet dilution, calorie restriction, protein restriction, carbohydrate: protein ratios and the modulations in various minor diet components. We thereby intend to gather the major advances made in these fields alongside reviewing the practical implementations that need to be made to get a better view of the DR-mediated lifespan studies.

Effects of high-fat diet on feeding and performance in the tobacco hornworm, Manduca sexta

Nutritionally balanced diets are important for overall fitness. For insects, fat is vital for development due to its high-energy value. Little is known about how insects regulate dietary fat for storage, but research has shown conflicting results on how altering fat impacts development and performance. In this study, we sought to investigate how high-fat diets affect developing insects. To determine how insects respond to variation in dietary fat content, we reared Manduca sexta of different larval stages on diets containing varying concentrations of linseed oil in high (5.6%), medium (3.4%) or low (0.4%) fat. Young larvae reared on high-fat diets had 80% mortality and 43% lower body mass compared to those reared on medium- or low-fat diets. Older larvae showed no difference in mortality with increasing dietary fat content, but they were smaller than controls, suggesting a developmental shift in lipid metabolism. We measured mRNA expression of Apolipoprotein I and II (APO1 and 2), proteins responsible for transporting lipids, as a possible explanation of increased survival in older larvae. Levels of APO1 and 2 mRNA did not differ with dietary fat content. We then tested the hypothesis that the high-fat diet altered feeding, resulting in the observed decrease in body size. Caterpillars fed a high-fat diet indeed ate less, as indicated by a decrease in food consumption and the number and mass of fecal pellets produced. These results suggest that increased fat disrupted feeding and may indicate that there is a threshold for lipid storage, but further studies are needed to understand the underlying mechanism.

Nutrigenomics as a tool to study the impact of diet on aging and age-related diseases: the Drosophila approach

Aging is a complex phenomenon caused by the time-dependent loss of cellular homeodynamics and consequently of physiological organismal functions. This process is affected by both genetic and environmental (e.g., diet) factors, as well as by their constant interaction. Consistently, deregulation of nutrient sensing and signaling pathways is considered a hallmark of aging. Nutrigenomics is an emerging scientific discipline that studies changes induced by diet on the genome and thus it considers the intersection of three topics, namely health, diet, and genomics. Model organisms, such as the fruit fly Drosophila melanogaster, have been successfully used for in vivo modeling of higher metazoans aging and for nutrigenomic studies. Drosophila is a well-studied organism with sophisticated genetics and a fully annotated sequenced genome, in which ~ 75% of human disease-related genes have functional orthologs. Also, flies have organs/tissues that perform the equivalent functions of most mammalian organs, while discrete clusters of cells maintain insect carbohydrate homeostasis in a way similar to pancreatic cells. Herein, we discuss the mechanistic connections between nutrition and aging in Drosophila, and how this model organism can be used to study the effect of different diets (including natural products and/or their derivatives) on higher metazoans longevity.

Sirtuins as Mediator of the Anti-Ageing Effects of Calorie Restriction in Skeletal and Cardiac Muscle

Fighting diseases and controlling the signs of ageing are the major goals of biomedicine. Sirtuins, enzymes with mainly deacetylating activity, could be pivotal targets of novel preventive and therapeutic strategies to reach such aims. Scientific proofs are accumulating in experimental models, but, to a minor extent, also in humans, that the ancient practice of calorie restriction could prove an effective way to prevent several degenerative diseases and to postpone the detrimental signs of ageing. In the present review, we summarize the evidence about the central role of sirtuins in mediating the beneficial effects of calorie restriction in skeletal and cardiac muscle since these tissues are greatly damaged by diseases and advancing years. Moreover, we entertain the possibility that the identification of sirtuin activators that mimic calorie restriction could provide the benefits without the inconvenience of this dietary style.

Progeny of old parents have increased social space in Drosophila melanogaster

We report the effects of aging and parental age in Drosophila melanogaster on two types of responses to social cues: the choice of preferred social spacing in an undisturbed group and the response to the Drosophila stress odorant (dSO) emitted by stressed flies. The patterns of changes during aging were notably different for these two social responses. Flies were initially closer in space and then became further apart. However, the pattern of change in response to dSO followed a more typical decline in performance, similarly to changes in locomotion. Interestingly, the increased social space of old parents, as well as their reduced performance in avoiding dSO, was passed on to their progeny, such that young adults adopted the behavioural characteristic of their old parents. While the response to social cues was inherited, the changes in locomotion were not. We were able to scale the changes in the social space of parents and their progeny by accelerating or decelerating the physiological process of aging by increasing temperatures and exposure to oxidative stress, or via caloric restriction, respectively. Finally, when we aged only one parent, only the male progeny of old fathers and the progeny of very old mothers were more distant.

The effect of olive (Olea europaea L.) phenolics and sugar on Drosophila melanogaster’s development

Olive leaves (Olea europaea L.) contain phenolics that are used for various aims and can also be utilized as free radical scavengers and as a powerful antioxidant source. In this study, our aim was to observe the effects of olive phenolics on the survival rate, development, sex ratio, and adult longevity of Drosophila melanogaster Meigen (Diptera: Drosophilidae) fed with sugar and with a sugar-free diet. The amount of malondialdehyde and the activity of glutathione S-transferase were examined with UV-VIS spectrophotometry in third-stage larvae, pupae and adults. For this purpose, dried olive fruit and leaf extracts were added at different concentrations to the insect’s sugary diets. The results reveal that 12 mg/L phenolic fruit extract and 4 M sucrose had a negative impact on the development and survival of these insects. It was also found that phenolic leaf extract and low sugar concentrations changed the sex ratio, leading to fewer females and more males. The use of phenolic fruit and phenolic leaf extracts with increased sugar-based diets raised the amount of oxidation as well as the detoxification activity in this model organism. These results demonstrate that low amounts of sugar and olive phenolics may be used as an adjunct to adult nutrients to improve the insect’s adult characteristics.

Amino acid modulation of lifespan and reproduction in Drosophila

Manipulating amino acid (AA) intake in Drosophila can profoundly affect lifespan and reproduction. Remarkably, AA manipulation can uncouple the commonly observed trade-off between these traits. This finding seems to challenge the idea that this trade-off is due to competitive resource allocation, but here we argue that this view might be too simplistic. We also discuss the mechanisms of the AA response, mediated by the IIS/TOR and GCN2 pathways. Elucidating how these pathways respond to specific AA will likely yield important insights into how AA modulate the reproduction-lifespan relationship. The Drosophila model offers powerful genetic tools, combined with options for precise diet manipulation, to address these fundamental questions.

Genetic perturbation of key central metabolic genes extends lifespan in Drosophila and affects response to dietary restriction

There is a connection between nutrient inputs, energy-sensing pathways, lifespan variation and aging. Despite the role of metabolic enzymes in energy homeostasis and their metabolites as nutrient signals, little is known about how their gene expression impacts lifespan. In this report, we use P-element mutagenesis in Drosophila to study the effect on lifespan of reductions in expression of seven central metabolic enzymes, and contrast the effects on normal diet and dietary restriction. The major observation is that for five of seven genes, the reduction of gene expression extends lifespan on one or both diets. Two genes are involved in redox balance, and we observe that lower activity genotypes significantly extend lifespan. The hexokinases also show extension of lifespan with reduced gene activity. Since both affect the ATP/ADP ratio, this connects with the role of AMP-activated protein kinase as an energy sensor in regulating lifespan and mediating caloric restriction. These genes possess significant expression variation in natural populations, and our experimental genotypes span this level of natural activity variation. Our studies link the readout of energy state with the perturbation of the genes of central metabolism and demonstrate their effect on lifespan.

Acidic Food pH Increases Palatability and Consumption and Extends Drosophila Lifespan

BACKGROUND

Despite the prevalent use of Drosophila as a model in studies of nutrition, the effects of fundamental food properties, such as pH, on animal health and behavior are not well known.

OBJECTIVES

We examined the effect of food pH on adult Drosophila lifespan, feeding behavior, and microbiota composition and tested the hypothesis that pH-mediated changes in palatability and total consumption are required for modulating longevity.

METHODS

We measured the effect of buffered food (pH 5, 7, or 9) on male gustatory responses (proboscis extension), total food intake, and male and female lifespan. The effect of food pH on germfree male lifespan was also assessed. Changes in fly-associated microbial composition as a result of food pH were determined by 16S ribosomal RNA gene sequencing. Male gustatory responses, total consumption, and male and female longevity were additionally measured in the taste-defective Pox neuro (Poxn) mutant and its transgenic rescue control.

RESULTS

An acidic diet increased Drosophila gustatory responses (40-230%) and food intake (5-50%) and extended survival (10-160% longer median lifespan) compared with flies on either neutral or alkaline pH food. Alkaline food pH shifted the composition of fly-associated bacteria and resulted in greater lifespan extension (260% longer median survival) after microbes were eliminated compared with flies on an acidic (50%) or neutral (130%) diet. However, germfree flies lived longer on an acidic diet (5-20% longer median lifespan) compared with those on either neutral or alkaline pH food. Gustatory responses, total consumption, and longevity were unaffected by food pH in Poxn mutant flies.

CONCLUSIONS

Food pH can directly influence palatability and feeding behavior and affect parameters such as microbial growth to ultimately affect Drosophila lifespan. Fundamental food properties altered by dietary or drug interventions may therefore contribute to changes in animal physiology, metabolism, and survival.

Vitellogenin-RNAi and ovariectomy each increase lifespan, increase protein storage, and decrease feeding, but are not additive in grasshoppers

Reduced reproduction has been shown to increase lifespan in many animals, yet the mechanisms behind this trade-off are unclear. We addressed this question by combining two distinct, direct means of life-extension via reduced reproduction, to test whether they were additive. In the lubber grasshopper, Romalea microptera, ovariectomized (OVX) individuals had a ~20% increase in lifespan and a doubling of storage relative to controls (Sham operated). Similarly, young female grasshoppers treated with RNAi against vitellogenin (the precursor to egg yolk protein) had increased fat body mass and halted ovarian growth. In this study, we compared VgRNAi to two control groups that do not reduce reproduction, namely buffer injection (Buffer) and injection with RNAi against a hexameric storage protein (Hex90RNAi). Each injection treatment was tested with and without ovariectomy. Hence, we tested feeding, storage, and lifespans in six groups: OVX and Buffer, OVX and Hex90RNAi, OVX and VgRNAi, Sham and Buffer, Sham and Hex90RNAi, and Sham and VgRNAi. Ovariectomized grasshoppers and VgRNAi grasshoppers each had similar reductions in feeding (~40%), increases in protein storage in the hemolymph (150-300%), and extensions in lifespan (13-21%). Ovariectomized grasshoppers had higher vitellogenin protein levels than did VgRNAi grasshoppers. Last but not least, when ovariectomy and VgRNAi were applied together, there was no greater effect on feeding, protein storage, or longevity. Hence, feeding regulation, and protein storage in insects, may be conserved components of life-extension via reduced reproduction.

The Role of Storage Lipids in the Relation between Fecundity, Locomotor Activity, and Lifespan of Drosophila melanogaster Longevity-Selected and Control Lines

The contribution of insect fat body to multiple processes, such as development, metamorphosis, activity, and reproduction results in trade-offs between life history traits. In the present study, age-induced modulation of storage lipid composition in Drosophila melanogaster longevity-selected (L) and non-selected control (C) lines was studied and the correlation between total body fat mass and lifespan assessed. The trade-offs between fecundity, locomotor activity, and lifespan were re-evaluated from a lipid-related metabolic perspective. Fewer storage lipids in the L lines compared to the C lines supports the impact of body fat mass on extended lifespan. The higher rate of fecundity and locomotor activity in the L lines may increase the lipid metabolism and enhance the lipolysis of storage lipids, reducing fat reserves. The correlation between neutral lipid fatty acids and fecundity, as well as locomotor activity, varied across age groups and between the L and C lines. The fatty acids that correlated with egg production were different from the fatty acids that correlated with locomotor activity. The present study suggests that fecundity and locomotor activity may positively affect the lifespan of D. melanogaster through the inhibition of fat accumulation.

Dietary protein:carbohydrate balance is a critical modulator of lifespan and reproduction in Drosophila melanogaster: a test using a chemically defined diet

Macronutrient balance is an important determinant of fitness in many animals, including insects. Previous studies have shown that altering the concentrations of yeast and sugar in the semi-synthetic media has a profound impact on lifespan in Drosophila melanogaster, suggesting that dietary protein:carbohydrate (P:C) balance is the main driver of lifespan and ageing processes. However, since yeast is rich in multiple nutrients other than proteins, this lifespan-determining role of dietary P:C balance needs to be further substantiated through trials using a chemically-defined, synthetic diet. In the present study, the effects of dietary P:C balance on lifespan and fecundity were investigated in female D. melanogaster flies fed on one of eight isocaloric synthetic diets differing in P:C ratio (0:1, 1:16, 1:8, 1:4, 1:2, 1:1, 2:1 or 4:1). Lifespan and dietary P:C ratio were related in a convex manner, with lifespan increasing to a peak at the two intermediate P:C ratios (1:2 and 1:4) and falling at the imbalanced ratios (0:1 and 4:1). Ingesting nutritionally imbalanced diets not only caused an earlier onset of senescence but also accelerated the age-dependent increase in mortality. Egg production was suppressed when flies were fed on a protein-deficient food (0:1), but increased with increasing dietary P:C ratio. Long-lived flies at the intermediate P:C ratios (1:2 and 1:4) stored a greater amount of lipids than those short-lived ones at the two imbalanced ratios (0:1 and 4:1). These findings provide a strong support to the notion that adequate dietary P:C balance is crucial for extending lifespan in D. melanogaster and offer new insights into how dietary P:C balance affects lifespan and ageing through its impacts on body composition.

Macronutrient balance, reproductive function, and lifespan in aging mice

In invertebrates, reproductive output and lifespan are profoundly impacted by dietary macronutrient balance, with these traits achieving their maxima on different diet compositions, giving the appearance of a resource-based tradeoff between reproduction and longevity. For the first time in a mammal, to our knowledge, we evaluate the effects of dietary protein (P), carbohydrate (C), fat (F), and energy (E) on lifespan and reproductive function in aging male and female mice. We show that, as in invertebrates, the balance of macronutrients has marked and largely opposing effects on reproductive and longevity outcomes. Mice were provided ad libitum access to one of 25 diets differing in P, C, F, and E content, with reproductive outcomes assessed at 15 months. An optimal balance of macronutrients exists for reproductive function, which, for most measures, differs from the diets that optimize lifespan, and this response differs with sex. Maximal longevity was achieved on diets containing a P:C ratio of 1:13 in males and 1:11 for females. Diets that optimized testes mass and epididymal sperm counts (indicators of gamete production) contained a higher P:C ratio (1:1) than those that maximized lifespan. In females, uterine mass (an indicator of estrogenic activity) was also greatest on high P:C diets (1:1) whereas ovarian follicle number was greatest on P:C 3:1 associated with high-F intakes. By contrast, estrous cycling was more likely in mice on lower P:C (1:8), and the number of corpora lutea, indicative of recent ovulations, was greatest on P:C similar to those supporting greatest longevity (1:11).

The effect of developmental nutrition on life span and fecundity depends on the adult reproductive environment in Drosophila melanogaster

Both developmental nutrition and adult nutrition affect life-history traits; however, little is known about whether the effect of developmental nutrition depends on the adult environment experienced. We used the fruit fly to determine whether life-history traits, particularly life span and fecundity, are affected by developmental nutrition, and whether this depends on the extent to which the adult environment allows females to realize their full reproductive potential. We raised flies on three different developmental food levels containing increasing amounts of yeast and sugar: poor, control, and rich. We found that development on poor or rich larval food resulted in several life-history phenotypes indicative of suboptimal conditions, including increased developmental time, and, for poor food, decreased adult weight. However, development on poor larval food actually increased adult virgin life span. In addition, we manipulated the reproductive potential of the adult environment by adding yeast or yeast and a male. This manipulation interacted with larval food to determine adult fecundity. Specifically, under two adult conditions, flies raised on poor larval food had higher reproduction at certain ages - when singly mated this occurred early in life and when continuously mated with yeast this occurred during midlife. We show that poor larval food is not necessarily detrimental to key adult life-history traits, but does exert an adult environment-dependent effect, especially by affecting virgin life span and altering adult patterns of reproductive investment. Our findings are relevant because (1) they may explain differences between published studies on nutritional effects on life-history traits; (2) they indicate that optimal nutritional conditions are likely to be different for larvae and adults, potentially reflecting evolutionary history; and (3) they urge for the incorporation of developmental nutritional conditions into the central life-history concept of resource acquisition and allocation.

Nutrient control of Drosophila longevity

Dietary restriction (DR) extends the lifespan of many animals, including Drosophila melanogaster. Recent work with flies shows that longevity is controlled by the ratio of consumed protein relative to carbohydrates. Given that reduced insulin and/or insulin-like growth factor (IGF) and target of rapamycin (TOR) signaling increase Drosophila lifespan, these pathways are candidate mediators of DR. However, this idea has ambiguous experimental support. The Nutritional Geometric Framework (NGF), which dissects the impact of nutrient protein relative to carbohydrates, may provide an approach to resolving the roles for these pathways in DR. Nutrient sensing of protein and carbohydrate may occur in the fat body through signals to hypothalamic-like neurons in the fly brain and, thus, control secretion of insulin-like peptides that regulate longevity.

Mechanisms underlying the anti-aging and anti-tumor effects of lithocholic bile acid

Bile acids are cholesterol-derived bioactive lipids that play essential roles in the maintenance of a heathy lifespan. These amphipathic molecules with detergent-like properties display numerous beneficial effects on various longevity- and healthspan-promoting processes in evolutionarily distant organisms. Recent studies revealed that lithocholic bile acid not only causes a considerable lifespan extension in yeast, but also exhibits a substantial cytotoxic effect in cultured cancer cells derived from different tissues and organisms. The molecular and cellular mechanisms underlying the robust anti-aging and anti-tumor effects of lithocholic acid have emerged. This review summarizes the current knowledge of these mechanisms, outlines the most important unanswered questions and suggests directions for future research.

Caloric restriction and the aging process: a critique

The main objective of this review is to provide an appraisal of the current status of the relationship between energy intake and the life span of animals. The concept that a reduction in food intake, or caloric restriction (CR), retards the aging process, delays the age-associated decline in physiological fitness, and extends the life span of organisms of diverse phylogenetic groups is one of the leading paradigms in gerontology. However, emerging evidence disputes some of the primary tenets of this conception. One disparity is that the CR-related increase in longevity is not universal and may not even be shared among different strains of the same species. A further misgiving is that the control animals, fed ad libitum (AL), become overweight and prone to early onset of diseases and death, and thus may not be the ideal control animals for studies concerned with comparisons of longevity. Reexamination of body weight and longevity data from a study involving over 60,000 mice and rats, conducted by a National Institute on Aging-sponsored project, suggests that CR-related increase in life span of specific genotypes is directly related to the gain in body weight under the AL feeding regimen. Additionally, CR in mammals and "dietary restriction" in organisms such as Drosophila are dissimilar phenomena, albeit they are often presented to be the very same. The latter involves a reduction in yeast rather than caloric intake, which is inconsistent with the notion of a common, conserved mechanism of CR action in different species. Although specific mechanisms by which CR affects longevity are not well understood, existing evidence supports the view that CR increases the life span of those particular genotypes that develop energy imbalance owing to AL feeding. In such groups, CR lowers body temperature, rate of metabolism, and oxidant production and retards the age-related pro-oxidizing shift in the redox state.

ADI1, a methionine salvage pathway enzyme, is required for Drosophila fecundity

Background

Methionine, an essential amino acid, is required for protein synthesis and normal cell metabolism. The transmethylation pathway and methionine salvage pathway (MTA cycle) are two major pathways regulating methionine metabolism. Recently, methionine has been reported to play a key role in Drosophila fecundity.

Results

Here, we revealed that the MTA cycle plays a crucial role in Drosophila fecundity using the mutant of aci-reductone dioxygenase 1 (DADI1), an enzyme in the MTA cycle. In dietary restriction condition, the egg production of adi1 mutant flies was reduced compared to that of control flies. This fecundity defect in mutant flies was rescued by reintroduction of Dadi1 gene. Moreover, a functional homolog of human ADI1 also recovered the reproduction defect, in which the enzymatic activity of human ADI1 is required for normal fecundity. Importantly, methionine supply rescued the fecundity defect in Dadi1 mutant flies. The detailed analysis of Dadi1 mutant ovaries revealed a dramatic change in the levels of methionine metabolism. In addition, we found that three compounds namely, methionine, SAM and Methionine sulfoxide, respectively, may be required for normal fecundity.

Conclusions

In summary, these results suggest that ADI1, an MTA cycle enzyme, affects fly fecundity through the regulation of methionine metabolism.

Dietary intake of Curcuma longa and Emblica officinalis increases life span in Drosophila melanogaster

Intake of food and nutrition plays a major role in affecting aging process and longevity. However, the precise mechanisms underlying the ageing process are still unclear. To this respect, diet has been considered to be a determinant of ageing process. In order to better illustrate this, we used Drosophila melanogaster as a model and fed them orally with different concentrations of two commonly used Indian medicinal plant products, Curcuma longa (rhizome) and Emblica officinalis (fruit). The results revealed significant increase in life span of Drosophila flies on exposure to both the plant products, more efficiently by C. Longa than by E. officinalis. In order to understand whether the increase in lifespan was due to high-antioxidant properties of these medicinal plants, we performed enzymatic assays to assess the SOD and catalase activities in case of both treated and control Drosophila flies. Interestingly, the results support the free radical theory of aging as both these plant derivatives show high reactive oxygen species (ROS) scavenging activities.

Interactive effects of sex, social environment, dietary restriction, and methionine on survival and reproduction in fruit flies

For the evolution of life histories, the trade-off between survival and reproduction is fundamental. Because sexes optimize fitness in different ways, this trade-off is expected to be resolved differently by males and females. Consequently, the sexes are predicted to respond differently to changes in resource availability. In fruit flies, research on dietary restriction has focused largely on females maintained in the absence of males, thereby neglecting sexual interactions that affect reproductive behavior of both sexes under more natural conditions. Here, we tested for the interactive effects of diet (40, 60, 100, and 300 % of standard yeast concentrations) and social environment (separate-sex vs. mixed-sex groups) on male and female Drosophila melanogaster life histories. Additionally, we evaluated the essential amino acid methionine as an agent that can uncouple the survival-reproduction trade-off. We show sex differences in the effect of social environment on survival patterns, but not on reproductive fitness. In females, yeast had a positive effect on reproduction and a negative effect on survival. In males, yeast had a negative effect on reproduction and the effect on survival depended on the social environment. Methionine reduced survival, but had no effect on reproduction. Our findings highlight the need to include both sexes and to vary social environments in research programs aimed at lifespan extension and call for further evaluation of the fecundity-restoring effect of methionine.

High carbohydrate-low protein consumption maximizes Drosophila lifespan

Dietary restriction extends lifespan in a variety of organisms, but the key nutritional components driving this process and how they interact remain uncertain. In Drosophila, while a substantial body of research suggests that protein is the major dietary component affecting longevity, recent studies claim that carbohydrates also play a central role. To clarify how nutritional factors influence longevity, nutrient consumption and lifespan were measured on a series of diets with varying yeast and sugar content. We show that optimal lifespan requires both high carbohydrate and low protein consumption, but neither nutrient by itself entirely predicts lifespan. Increased dietary carbohydrate or protein concentration does not always result in reduced feeding-the regulation of food consumption is best described by a constant daily caloric intake target. Moreover, due to differences in food intake, increased concentration of a nutrient within the diet does not necessarily result in increased consumption of that particular nutrient. Our results shed light on the issue of dietary effects on lifespan and highlight the need for accurate measures of nutrient intake in dietary manipulation studies.

dSir2 in the adult fat body, but not in muscles, regulates life span in a diet-dependent manner

Sir2, an evolutionarily conserved NAD(+)-dependent deacetylase, has been implicated as a key factor in mediating organismal life span. However, recent contradictory findings have brought into question the role of Sir2 and its orthologs in regulating organismal longevity. In this study, we report that Drosophila Sir2 (dSir2) in the adult fat body regulates longevity in a diet-dependent manner. We used inducible Gal4 drivers to knock down and overexpress dSir2 in a tissue-specific manner. A diet-dependent life span phenotype of dSir2 perturbations (both knockdown and overexpression) in the fat body, but not muscles, negates the effects of background genetic mutations. In addition to providing clarity to the field, our study contrasts the ability of dSir2 in two metabolic tissues to affect longevity. We also show that dSir2 knockdown abrogates fat-body dFOXO-dependent life span extension. This report highlights the importance of the interplay between genetic factors and dietary inputs in determining organismal life spans.

Novel protein kinase signaling systems regulating lifespan identified by small molecule library screening using Drosophila

Protein kinase signaling cascades control most aspects of cellular function. The ATP binding domains of signaling protein kinases are the targets of most available inhibitors. These domains are highly conserved from mammals to flies. Herein we describe screening of a library of small molecule inhibitors of protein kinases for their ability to increase Drosophila lifespan. We developed an assay system which allowed screening using the small amounts of materials normally present in commercial chemical libraries. The studies identified 17 inhibitors, the majority of which targeted tyrosine kinases associated with the epidermal growth factor receptor (EGFR), platelet-derived growth factor (PDGF)/vascular endothelial growth factor (VEGF) receptors, G-protein coupled receptor (GPCR), Janus kinase (JAK)/signal transducer and activator of transcription (STAT), the insulin and insulin-like growth factor (IGFI) receptors. Comparison of the protein kinase signaling effects of the inhibitors in vitro defined a consensus intracellular signaling profile which included decreased signaling by p38MAPK (p38), c-Jun N-terminal kinase (JNK) and protein kinase C (PKC). If confirmed, many of these kinases will be novel additions to the signaling cascades known to regulate metazoan longevity.

Influence of two methods of dietary restriction on life history features and aging of the cricket Acheta domesticus

Studying aging is constrained using vertebrates by their longevity, size, ethical restrictions, and expense. The key insect model, Drosophila melanogaster, is holometabolous. Larvae feed on yeast in moist media and adults sponge food. Most aging studies are restricted to adults. Another key model, the nematode Caenorhabditis elegans, feeds on bacteria in moist media. For either invertebrate refreshing test materials, preventing degradation and obtaining accurate dosing are difficult even with synthetic media. The cricket Acheta domesticus has a short lifespan (∼120 days at 30°C) and is omnivorous. Age-matched cohorts are easily obtained from eggs. The life cycle is hemimetabolous and nymphs eat the same foods as adults. Growth is easily monitored, gender can be differentiated before maturity, and maturation is indicated by wings and mature genitalia. Crickets can be reared in large numbers at low cost. Test materials can be mixed into food and ingestion rates or mass budgets easily assessed. Here, we validate the cricket as a model of aging by testing two fundamental methods of restricting food intake: time-restricted access to food and dietary dilution. Growth, maturation, survivorship, and longevity varied with treatments and genders. Intermittent feeding (which is ineffective in flies) significantly extended longevity of crickets. Dietary dilution also extended longevity via remarkable prolongation of the juvenile period.

"Cost" of virginity in wild Drosophila melanogaster females

Laboratory studies have revealed a significant "cost of mating" to Drosophila melanogaster females in the form of reduced longevity. The effect is attributable to nonsperm components of the ejaculate. Female D. melanogaster are known to mate up to six times in nature, and given that they do not typically remate daily, it raises the question as to the extent to which the longevity of wild mated females is reduced. Here I addressed this question by comparing the longevity of wild virgin females, collected as they emerged from rotting fruit, to the longevity of randomly collected mature females at the same site. Because the randomly collected females all were inseminated and were fully pigmented at the time of collection, they already were older than the virgins when the experiment began. Contrary to expectations from laboratory studies, the older, mated females lived significantly longer than the virgins. Rather than a "cost of mating," there appears to be a "cost of virginity" to female D. melanogaster in the wild.

Management of protein intake in the fruit fly Anastrepha fraterculus

This work tested if carbohydrates and proteins ingestion is regulated in the South American fruit fly, Anastrepha fraterculus, to optimize survival and reproduction. Adult food treatments were established by providing sugar and hydrolyzed yeast in various combinations either alone or mixed at a standard 3:1 ratio (sugar:hydrolyzed yeast). Individual food consumption was assessed and related to survival patterns. The effects of adult feeding on fecundity and fertility patterns were investigated in groups of flies. Sugar consumption was the lowest in the treatment where it was provided with hydrolyzed yeast at a fixed 3:1 ratio. Consumption of hydrolyzed yeast did not differ between this treatment and the one in which this solution was complemented with one solution of sugar. It seems that a mixture of sugar and hydrolyzed yeast at a fixed ratio of 3:1, respectively, restricts extra ingestion of sugar; most probably because of negative response of the fly to overconsumption of protein. Survival was affected by the treatments, being lower in those cases where protein was at the fixed ratio. Group experiments revealed that protein restriction expanded longevity and decreased egg production. In contrast, egg production was enhanced when flies were kept continuously with a mixture of yeast and sugar plus an extra source of sugar, and this was not in detriment of survival. Our results suggest that fixed sugar-protein ratios in which protein is in excess affects fitness components such as longevity and reproduction. These findings are discussed from a theoretical and applied perspective in the context of pest control by means of the sterile insect technique.

Impact of caloric and dietary restriction regimens on markers of health and longevity in humans and animals: a summary of available findings

Considerable interest has been shown in the ability of caloric restriction (CR) to improve multiple parameters of health and to extend lifespan. CR is the reduction of caloric intake - typically by 20 - 40% of ad libitum consumption - while maintaining adequate nutrient intake. Several alternatives to CR exist. CR combined with exercise (CE) consists of both decreased caloric intake and increased caloric expenditure. Alternate-day fasting (ADF) consists of two interchanging days; one day, subjects may consume food ad libitum (sometimes equaling twice the normal intake); on the other day, food is reduced or withheld altogether. Dietary restriction (DR) - restriction of one or more components of intake (typically macronutrients) with minimal to no reduction in total caloric intake - is another alternative to CR. Many religions incorporate one or more forms of food restriction. The following religious fasting periods are featured in this review: 1) Islamic Ramadan; 2) the three principal fasting periods of Greek Orthodox Christianity (Nativity, Lent, and the Assumption); and 3) the Biblical-based Daniel Fast. This review provides a summary of the current state of knowledge related to CR and DR. A specific section is provided that illustrates related work pertaining to religious forms of food restriction. Where available, studies involving both humans and animals are presented. The review includes suggestions for future research pertaining to the topics of discussion.

Life-extending dietary restriction and ovariectomy result in similar feeding rates but different physiologic responses in grasshoppers

Dietary restriction (DR) and reduced reproduction each extend life span in many species. Females undergoing DR typically experience a reduction in their fecundity, which raises the question of whether the two treatments are actually extending life span in overlapping ways. Life span in lubber grasshoppers has been shown to be increased by DR, and separately by ovariectomy (OVX). Here, we test the combination of these on life span. If life extension by the two treatments are additive, it would suggest that they likely act through separate pathways. The experimental groups were: fully reproductive and fully fed (ShamFD); ovariectomized and fully fed (OVXFD); fully reproductive and restricted diet (ShamDR); and ovariectomized and restricted diet (OVXDR). The median life spans of these groups were: ShamFD=245 d, OVXFD=285 d, ShamDR=286 d, and OVXDR=322 d. Feeding rate for the OVXFD group was 64% of ad libitum, similar to the 70% of ad libitum that was used for ShamDR. We also measured hemolymph parameters of physiology in these same individuals. Hemolymph levels of vitellogenin (the egg yolk-precursor protein) were increased 5-fold by OVX, but were not affected by DR. In addition, hemolymph total anti-oxidant activity (per μg protein) was significantly reduced by OVX, but was not affected by DR. We show that OVX and DR produce different physiological responses in grasshoppers, despite life extensions and feeding levels that were not significantly different. These data suggest that OVX and DR might extend life span via distinct pathways.

Gender-specific prandial response to dietary restriction and oxidative stress in Drosophila melanogaster

Drosophila melanogaster is ideal for studying lifespan modulated by dietary restriction (DR) and oxidative stress, and also for screening prolongevity compounds. It is critical to measure food intake in the aforementioned studies. Current methods, however, overlook the amount of the food excreted out of the flies as feces or deposited in eggs. Here we describe a feeding method using a radioactive tracer to measure gender-specific food intake, retention and excretion in response to DR and oxidative stress to account for all the ingested food. Flies were fed a full, restricted or paraquat-containing diet. The radioactivity values of the food in fly bodies, feces and eggs were measured separately after a 24-hr feeding. Food intake was calculated as the sum of these measurements. We found that most of the tracer in the ingested food was retained in the fly bodies and < 8% of the tracer was excreted out of the flies as feces and eggs in the case of females during a 24-hr feeding. Under a DR condition, flies increased food intake in volume to compensate for the reduction of calorie content in the diet and also slightly increased excretion. Under an oxidative stress condition, flies reduced both food intake and excretion. Under all the tested dietary conditions, males ingested and excreted 3-5 fold less food than females. This study describes an accurate method to measure food intake and provides a basis to further investigate prandial response to DR and prolongevity interventions in invertebrates.

Aloe vera or resveratrol supplementation in larval diet delays adult aging in the fruit fly, Drosophila melanogaster

Longevity extension in Drosophila melanogaster by feeding diet supplemented with chemicals throughout adulthood can cause harmful side effects. We tested the effect of larval diet supplementation with five different concentrations of resveratrol and one concentration of Aloe vera extract on the adult longevity of short-lived D melanogaster populations. Resveratrol and A vera extract supplementation of larval diet extended adult longevity in both the male and female flies without reducing fecundity but by efficient reactive oxygen species scavenging through increased antioxidant enzymes activity and better neuroprotection as indicated by increased locomotor activity in adult males.