Pioglitazone: an anti-diabetic compound with anti-aging properties

Anti-diabetic drug pioglitazone reduces Islet amyloid aggregation overload in the Drosophila neuronal cells

Amyloid-proteinopathy is observed in type 2 diabetes, where Islet amyloid polypeptide is secreted atypically and impedes cellular homeostasis. The thiazolidinediones family is reported to influence amyloid-beta aggregations. However, research on drug-based stimulation of insulin signaling to alleviate Islet amyloid aggregations is lacking. To understand the impact of pioglitazone on islet amyloid aggregation, we conducted an in vivo and in silico analysis. For in vivo analysis, we generated a transgenic Drosophila harboring the preproform of human Islet amyloid polypeptide (IAPP) that can be ectopically expressed in a spatio-temporal manner. We show that the unprocessed form of IAPP also has the propensity to form aggregates and cause degeneration. Pioglitazone feeding effectively reduces the burden of Islet amyloid aggregations in the larval brain. In silico analysis shows that there is a higher protein-ligand binding energy for IAPP with pioglitazone than amyloid-beta. These results suggests that pioglitazone might be repurposed as a drug to cure islet amyloidogenesis.

Glipizide ameliorates human poly(Q) mediated neurotoxicity by upregulating insulin signalling in Drosophila disease models

Increasing reports suggest insulin signalling pathway as a putative drug target against polyglutamine [poly(Q)] disorders, such as Huntington's disease (HD), Spinocerebellar ataxias (SCA) 1, 2, 3 etc. However, studies on drug-based stimulation of insulin signalling cascade to mitigate poly(Q) pathogenesis are lacking. In our study, we adopted an evidence-based approach to examine if some established insulin stimulating drug can be utilized to restrict poly(Q) aetiology in Drosophila disease models. For the first time, we report that glipizide, an FDA approved anti-diabetic drug upregulates insulin signalling in poly(Q) expressing tissues and restricts formation of inclusion bodies and neurodegeneration. Moreover, it reinstates the chromatin architecture by improving histone acetylation, which is otherwise abrogated due to poly(Q) toxicity. In view of the functional conservation of insulin signalling pathway in Drosophila and humans, our finding strongly suggests that glipizide can be repurposed as an effective treatment strategy against the neurodegenerative poly(Q) disorders. Also, with appropriate validation studies in mammalian disease models, glipizide could be subsequently considered for the clinical trials in human patients.

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.

Bell H, Tower J. A screen of small molecule and genetic modulators of life span in female Drosophila identifies etomoxir, RH5849 and unanticipated temperature effects

Mifepristone increases life span in female Drosophila melanogaster, and its molecular target(s) remain unclear. Here small molecule and genetic interventions were tested for ability to mimic mifepristone, or to decrease life span in a way that can be rescued by mifepristone. Etomoxir inhibits lipid metabolism, and significantly increased life span in virgin and mated females, but not males, at 50 µM concentration. Pioglitazone is reported to activate both mammalian PPARγ and its Drosophila homolog Eip75B. Pioglitazone produced minor and inconsistent benefits for female Drosophila life span, and only at the lowest concentrations tested. Ecdysone is a Drosophila steroid hormone reported to regulate responses to mating, and RH5849 is a potent mimic of ecdysone. RH5849 reduced virgin female life span, and this was partly rescued by mifepristone. Mifepristone did not compete with RH5849 for activation of an ecdysone receptor (EcR)-responsive transgenic reporter, indicating that the relevant target for mifepristone is not EcR. The conditional GAL4/GAL80ts system was used in attempt to test the effect of an Eip75B RNAi construct on female life span. However, the 29°C temperature used for induction reduced or eliminated mating-induced midgut hypertrophy, the negative life span effects of mating, and the positive life span effects of mifepristone. Even when applied after mating was complete, a shift to 29°C temperature reduced mating-induced midgut hypertrophy by half, and the life span effects of mating by 4.8-fold. Taken together, these results identify promising small molecules for further analysis, and inform the design of experiments involving the GAL4/GAL80ts system.

Aqueous extract from Astragalus membranaceus can improve the function degradation and delay aging on Drosophila melanogaster through antioxidant mechanism

Astragali radix is the dry root of the leguminous plants Astragalus membranaceus (Fisch.) Bge. Var. mongholicus (Bge.) Hsiao and Astragalus membranaceus (Fisch.) Bge. Astragali radix is mostly used clinically as a decoction. A number of pharmacological studies shows that Astragalus extract can increase telomerase activity, and has anti-oxidation, anti-inflammatory, immune regulation, anti-cancer, lowering blood lipid, lowering blood sugar and other effects. However, the anti-aging mechanism of aqueous extract from Astragali Radix (ARE) is still unclear. In this study, we evaluated the anti-aging effect of ARE on Drosophila melanogaster (D. melanogaster) and investigated the underlying mechanism. The results of lifespan assay showed that 1.25 mg/mL of ARE can significantly prolong the lifespan of D. melanogaster in a natural aging model, and protect against H2O2 and paraquat. Meanwhile, ARE can improve flies climbing ability and food intake. Metabolomics and the glutamate content assay suggested that ARE prevented an age-dependent increase in glutamate levels in D. melanogaster. Furthermore, ARE showed a dose-dependent effect on the scavenging ability of DPPH in vitro. Superoxide dismutase and catalase activities in the aging group also increased after the intervention of ARE. The data and the findings described here support the notion that ARE may play a preventive role in aging by improving the climbing ability, eliminating harmful free radicals accumulated in D. melanogaster and triggering antioxidant responses.

Pioglitazone Hydrochloride Extends the Lifespan of Caenorhabditis elegans by Activating DAF-16/FOXO- and SKN-1/NRF2-Related Signaling Pathways

Pioglitazone hydrochloride (PGZ), a nuclear receptor peroxisome proliferator-activated receptor gamma (PPAR-γ) agonist, is a universally adopted oral agent for the treatment of type 2 diabetes (T2D). Previous studies reported that PGZ could ameliorate the symptoms of aging-related diseases and Alzheimer's disease. However, whether PGZ participates in aging regulation and the underlying mechanism remain undetermined. Here, we found that PGZ significantly prolonged the lifespan and healthspan of Caenorhabditis elegans (C. elegans). We found that a variety of age-related pathways and age-related genes are required for PGZ-induced lifespan extension. The transcription factors DAF-16/FOXO, HSF-1, and SKN-1/NRF2, as well as the nuclear receptors DAF-12 and NHR-49, all functioned in the survival advantage conferred by PGZ. Moreover, our results demonstrated that PGZ induced lifespan extension through the inhibition of insulin/insulin-like signaling (IIS) and reproductive signaling pathways, as well as the activation of dietary restriction- (DR-) related pathways. Additionally, our results also indicated that beneficial longevity mediated by PGZ is linked to its antioxidative activity. Our research may provide a basis for further research on PGZ, as an anti-T2D drug, to interfere with aging and reduce the incidence of age-related diseases in diabetic patients.

Evolution of reproductive traits have no apparent life-history associated cost in populations of Drosophila melanogaster selected for cold shock resistance

Background

In insect species like Drosophila melanogaster, evolution of increased resistance or evolution of particular traits under specific environmental conditions can lead to energy trade-offs with other crucial life-history traits. Adaptation to cold stress can, in principle, involve modification of reproductive traits and physiological responses. Reproductive traits carry a substantial cost; and therefore, the evolution of reproductive traits in response to cold stress could potentially lead to trade-offs with other life-history traits. We have successfully selected replicate populations of Drosophila melanogaster for increased resistance to cold shock for over 33 generations. In these populations, the ability to recover from cold shock, mate, and lay fertile eggs 24 h post cold shock is under selection. These populations have evolved a suite of reproductive traits including increased egg viability, male mating ability, and siring ability post cold shock. These populations also show elevated mating rate both with and without cold shock. In the present study, we quantified a suite of life-history related traits in these populations to assess if evolution of cold shock resistance in these populations comes at a cost of other life-history traits.

Results

To assess life-history cost, we measured egg viability, mating frequency, longevity, lifetime fecundity, adult mortality, larva to adult development time, larvae to adults survival, and body weight in the cold shock selected populations and their controls under two treatments (a) post cold chock and (b) without cold shock. Twenty-four hours post cold shock, the selected population had significantly higher egg viability and mating frequency compared to control populations indicating that they have higher cold shock resistance. Selected populations had significantly longer pre-adult development time compared to their control populations. Females from the selected populations had higher body weight compared to their control populations. However, we did not find any significant difference between the selected and control populations in longevity, lifetime fecundity, adult mortality, larvae to adults survival, and male body weight under the cold chock or no cold shock treatments.

Conclusions

These findings suggest that cold shock selected populations have evolved higher mating frequency and egg viability. However, there is no apparent life-history associated cost with the evolution of egg viability and reproductive performances under the cold stress condition.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12862-021-01934-2.

Ecdysone steroid hormone remote controls intestinal stem cell fate decisions via the PPARγ-homolog Eip75B in Drosophila

Developmental studies revealed fundamental principles on how organ size and function is achieved, but less is known about organ adaptation to new physiological demands. In fruit flies, juvenile hormone (JH) induces intestinal stem cell (ISC) driven absorptive epithelial expansion balancing energy uptake with increased energy demands of pregnancy. Here, we show 20-Hydroxy-Ecdysone (20HE)-signaling controlling organ homeostasis with physiological and pathological implications. Upon mating, 20HE titer in ovaries and hemolymph are increased and act on nearby midgut progenitors inducing Ecdysone-induced-protein-75B (Eip75B). Strikingly, the PPARγ-homologue Eip75B drives ISC daughter cells towards absorptive enterocyte lineage ensuring epithelial growth. To our knowledge, this is the first time a systemic hormone is shown to direct local stem cell fate decisions. Given the protective, but mechanistically unclear role of steroid hormones in female colorectal cancer patients, our findings suggest a tumor-suppressive role for steroidal signaling by promoting postmitotic fate when local signaling is deteriorated.

Targeting Mitochondrial Network Architecture in Down Syndrome and Aging

Mitochondria are organelles that mainly control energy conversion in the cell. In addition, they also participate in many relevant activities, such as the regulation of apoptosis and calcium levels, and other metabolic tasks, all closely linked to cell viability. Functionality of mitochondria appears to depend upon their network architecture that may dynamically pass from an interconnected structure with long tubular units, to a fragmented one with short separate fragments. A decline in mitochondrial quality, which presents itself as an altered structural organization and a function of mitochondria, has been observed in Down syndrome (DS), as well as in aging and in age-related pathologies. This review provides a basic overview of mitochondrial dynamics, from fission/fusion mechanisms to mitochondrial homeostasis. Molecular mechanisms determining the disruption of the mitochondrial phenotype in DS and aging are discussed. The impaired activity of the transcriptional co-activator PGC-1α/PPARGC1A and the hyperactivation of the mammalian target of rapamycin (mTOR) kinase are emerging as molecular underlying causes of these mitochondrial alterations. It is, therefore, likely that either stimulating the PGC-1α activity or inhibiting mTOR signaling could reverse mitochondrial dysfunction. Evidence is summarized suggesting that drugs targeting either these pathways or other factors affecting the mitochondrial network may represent therapeutic approaches to improve and/or prevent the effects of altered mitochondrial function. Overall, from all these studies it emerges that the implementation of such strategies may exert protective effects in DS and age-related diseases.

Human geroprotector discovery by targeting the converging subnetworks of aging and age-related diseases

A key goal of geroscience research is to identify effective interventions to extend human healthspan, the years of healthy life. Currently, majority of the geroprotectors are found by screening compounds in model organisms; whether they will be effective in humans is largely unknown. Here we present a new strategy called ANDRU (aging network based drug discovery) to help the discovery of human geroprotectors. It first identifies human aging subnetworks that putatively function at the interface between aging and age-related diseases; it then screens for pharmacological interventions that may "reverse" the age-associated transcriptional changes occurred in these subnetworks. We applied ANDRU to human adipose gene expression data from the Genotype Tissue Expression (GTEx) project. For the top 31 identified compounds, 19 of them showed at least some evidence supporting their function in improving metabolic traits or lifespan, which include type 2 diabetes drugs such as pioglitazone. As the query aging genes were refined to the ones with more intimate links to diseases, ANDRU identified more meaningful drug hits than the general approach without considering the underlying network structures. In summary, ANDRU represents a promising human data-driven strategy that may speed up the discovery of interventions to extend human healthspan.

Experimental Models for Aging and their Potential for Novel Drug Discovery

Background:

An interesting area of scientific research is the development of potential antiaging drugs. In order to pursue this goal, it is necessary to gather the specific knowledge about the adequate preclinical models that are available to evaluate the beneficial effects of new potential drugs. This review is focused on invertebrate and vertebrate preclinical models used to evaluate the efficacy of antiaging compounds, with the objective to extend life span and health span.

Methods:

Research and online content related to aging, antiaging drugs, experimental aging models is reviewed. Moreover, in this review, the main experimental preclinical models of organisms that have contributed to the research in the pharmacol-ogy of lifespan extension and the understanding of the aging process are discussed.

Results:

Dietary restriction (DR) constitutes a common experimental process to extend life span in all organisms. Besides, classical antiaging drugs such as resveratrol, rapamycin and metformin denominated as DR mimetics are also discussed. Likewise, the main therapeutic targets of these drugs include sirtuins, IGF-1, and mTOR, all of them being modulated by DR.

Conclusion:

Advances in molecular biology have uncovered the potential molecular pathways involved in the aging process. Due to their characteristics, invertebrate models are mainly used for drug screening. The National Institute on Aging (NIA) developed the Interventions Testing Program (ITP). At the pre-clinical level, the ITP uses Heterogeneous mouse model (HET) which is probably the most suitable rodent model to study potential drugs against aging prevention. The accelerated-senescence mouse P8 is also a mammalian rodent model for aging research. However, when evaluating the effect of drugs on a preclinical level, the evaluation must be done in non-human primates since it is the mammalian specie closest to humans. Research is needed to investigate the impact of new potential drugs for the increase of human quality of

Modeling dietary influences on offspring metabolic programming in Drosophila melanogaster

The influence of nutrition on offspring metabolism has become a hot topic in recent years owing to the growing prevalence of maternal and childhood obesity. Studies in mammals have identified several factors correlating with parental and early offspring dietary influences on progeny health; however, the molecular mechanisms that underlie these factors remain undiscovered. Mammalian metabolic tissues and pathways are heavily conserved in Drosophila melanogaster, making the fly an invaluable genetic model organism for studying metabolism. In this review, we discuss the metabolic similarities between mammals and Drosophila and present evidence supporting its use as an emerging model of metabolic programming.

The antidepressant-like effects of pioglitazone in a chronic mild stress mouse model are associated with PPARγ-mediated alteration of microglial activation phenotypes

BACKGROUND

Discoveries that microglia-mediated neuroinflammation is involved in the pathological process of depression provided a new strategy for novel antidepressant therapy. Peroxisome proliferator-activated receptor γ (PPARγ) is a nuclear receptor regulating inflammation and microglial polarization and, therefore, a potential target for resolving depressive disorders. Our hypothesis was that antidepressant effects could be achieved through anti-inflammatory and neuroprotective activities by PPARγ-dependent microglia-modulating agents.

METHODS

Chronic mild stress (CMS) treatment was performed on C57BL/6 mice for 6 weeks. After 3 weeks with the CMS procedure, depressive-like behaviors were evaluated by sucrose preference (SP), tail suspension test (TST), forced swimming test (FST), and locomotor activity. Pioglitazone was administered intragastrically once per day for 3 weeks at different doses. Neuroinflammatory cytokines were determined by real time-PCR (RT-PCR), enzyme-linked immunosorbent assay (ELISA), and western blot. The activated microglial state was confirmed by immunohistochemistry. N9 microglial cells were subjected to lipopolysaccharide, pioglitazone, and GW9662 to discuss the phenotype of activated microglia by RT-PCR, ELISA, and western blot.

RESULTS

It was demonstrated that the PPARγ agonist pioglitazone (2.5 mg/kg) ameliorated depression-like behaviors in CMS-treated mice, as indicated by body weight (BW), the SP test, the FST, and the TST. The amelioration of the depression was blocked by the PPARγ antagonist GW9662. The expression of M1 markers (IL-1β, IL-6, TNFα, iNOS, and CCL2) increased, and the gene expression of M2 markers (Ym1, Arg1, IL-4, IL-10, and TGFβ) decreased in the hippocampus of the stress-treated mice. Pioglitazone significantly inhibited the increased numbers and morphological alterations of microglia in the hippocampus, reduced the elevated expression of microglial M1 markers, and increased the downgraded expression of microglial M2 markers in C57BL/6 mice exposed to CMS. In an in vitro experiment, pioglitazone reversed the imbalance of M1 and M2 inflammatory cytokines, which is correlated with the inhibition of nuclear factor kB activation and is expressed in LPS-stimulated N9 microglial cells.

CONCLUSIONS

We showed that pioglitazone administration induce the neuroprotective phenotype of microglia and ameliorate depression-like behaviors in CMS-treated C57BL/6 mice. These data suggested that the microglia-modulating agent pioglitazone present a beneficial choice for depression.

Effect of semolina-jaggery diet on survival and development of Drosophila melanogaster

Drosophila melanogaster is an ideal model organism for developmental studies. This study tests the potential of semolina-jaggery (SJ) diet as a new formulation for bulk rearing of flies. Semolina and jaggery are organic products obtained from wheat endosperm and cane sugar, respectively. Semolina is a rich source of carbohydrates and protein. Jaggery has a high content of dietary sugars. Moreover, preparation of semolina jaggery diet is cost-effective and easy. Thus, the current study aimed to compare survival and developmental parameters of flies fed the SJ diet to flies fed the standard cornmeal-sugar-yeast (CSY) diet. SJ diet enhanced survival of flies without affecting fecundity; male flies showed increased resistance to starvation. A higher number of flies emerged at F2 and F3 generation when fed the SJ diet than when fed the control CSY diet. SJ diet did not increase fly body weight and lipid percentage. Therefore, SJ diet can be used for bulk rearing of healthy flies at par with the standard cornmeal-sugar-yeast diet.

Finding Ponce de Leon's Pill: Challenges in Screening for Anti-Aging Molecules

Aging is characterized by the progressive accumulation of degenerative changes, culminating in impaired function and increased probability of death. It is the major risk factor for many human pathologies - including cancer, type 2 diabetes, and cardiovascular and neurodegenerative diseases - and consequently exerts an enormous social and economic toll. The major goal of aging research is to develop interventions that can delay the onset of multiple age-related diseases and prolong healthy lifespan (healthspan). The observation that enhanced longevity and health can be achieved in model organisms by dietary restriction or simple genetic manipulations has prompted the hunt for chemical compounds that can increase lifespan. Most of the pathways that modulate the rate of aging in mammals have homologs in yeast, flies, and worms, suggesting that initial screening to identify such pharmacological interventions may be possible using invertebrate models. In recent years, several compounds have been identified that can extend lifespan in invertebrates, and even in rodents. Here, we summarize the strategies employed, and the progress made, in identifying compounds capable of extending lifespan in organisms ranging from invertebrates to mice and discuss the formidable challenges in translating this work to human therapies.

Metformin: A Hopeful Promise in Aging Research

Even though the inevitable process of aging by itself cannot be considered a disease, it is directly linked to life span and is the driving force behind all age-related diseases. It is an undisputable fact that age-associated diseases are among the leading causes of death in the world, primarily in industrialized countries. During the last several years, an intensive search of antiaging treatments has led to the discovery of a variety of drugs that promote health span and/or life extension. The biguanide compound metformin is widely used for treating people with type 2 diabetes and appears to show protection against cancer, inflammation, and age-related pathologies. Here, we summarize the recent developments about metformin use in translational aging research and discuss its role as a potential geroprotector.

Evolution of increased adult longevity in Drosophila melanogaster populations selected for adaptation to larval crowding

In holometabolous animals such as Drosophila melanogaster, larval crowding can affect a wide range of larval and adult traits. Adults emerging from high larval density cultures have smaller body size and increased mean life span compared to flies emerging from low larval density cultures. Therefore, adaptation to larval crowding could potentially affect adult longevity as a correlated response. We addressed this issue by studying a set of large, outbred populations of D. melanogaster, experimentally evolved for adaptation to larval crowding for 83 generations. We assayed longevity of adult flies from both selected (MCUs) and control populations (MBs) after growing them at different larval densities. We found that MCUs have evolved increased mean longevity compared to MBs at all larval densities. The interaction between selection regime and larval density was not significant, indicating that the density dependence of mean longevity had not evolved in the MCU populations. The increase in longevity in MCUs can be partially attributed to their lower rates of ageing. It is also noteworthy that reaction norm of dry body weight, a trait probably under direct selection in our populations, has indeed evolved in MCU populations. To the best of our knowledge, this is the first report of the evolution of adult longevity as a correlated response of adaptation to larval crowding.

Green tea polyphenols extend the lifespan of male drosophila melanogaster while impairing reproductive fitness

Green tea is a popular beverage believed to have many health benefits, including a reduction in the risks of heart disease and cancer. Rich in polyphenolic compounds known as catechins, green tea and its components have been shown to increase the lifespan of various animal models, including Drosophila melanogaster. Here, we investigated the gender-specific effects of green tea on the lifespan of fruit flies and observed that green tea extended the lifespan of male flies only. This effect was found to be independent of typical aging interventions, such as dietary restriction, modulation of oxidative energy metabolism, and improved tolerance to environmental stresses. The one exception was that green tea did protect male flies against iron toxicity. Since there is an inverse correlation between lifespan and reproduction, the impact of green tea on male reproductive fitness was also investigated. We found that green tea negatively impacted male fertility as shown by a reduced number of offspring produced and increased mating latency. We further identified that the lifespan extension properties of green tea was only observed in the presence of females which alludes to a reproductive (or mating) dependent mechanism. Our findings suggest that green tea extends the lifespan of male flies by inhibiting reproductive potential, possibly by limiting iron uptake. To our knowledge, our study is the first to report the negative impact of green tea on Drosophila male reproduction. Our results also support previous studies that suggest that green tea might have a negative effect on reproductive fitness in humans.

Activation of PPAR-γ by pioglitazone attenuates oxidative stress in aging rat cerebral arteries through upregulating UCP2

Increasing amounts of evidence implicate oxidative stress as having a pivotal role in age-related cerebrovascular dysfunction, which is an important risk factor for the development of cerebrovascular disease. Previous studies have shown that the activation of the expression of peroxisome proliferator-activated receptor gamma (PPAR-γ) in vascular endothelial cells results in an improvement of vascular function. Pioglitazone, a well-known PPAR-γ agonist, protects against oxidative stress in the rostral ventrolateral medulla by the upregulation of mitochondrial uncoupling protein 2 (UCP2). In this study, we sought to explore the effects and the underlying mechanisms of pioglitazone on age-related oxidative stress elevation and cerebrovascular dysfunction in aging rat cerebral arteries. A natural aging model was constructed and used in these experiments. One-month oral administration of pioglitazone (20 mg·kg·d) ameliorated the production of reactive oxygen species, promoted endothelial nitric oxide synthase phosphorylation and increased the nitric oxide available, thus improving endothelium-dependent relaxation in aging rat cerebral arteries. One-month pioglitazone administration also restored PPAR-γ expression and increased the levels of UCP2 in aging rat cerebral arteries. Using in vitro studies, we demonstrated that pioglitazone attenuated reactive oxygen species levels in aging human umbilical vein endothelial cells through PPAR-γ activation. Furthermore, we found that this occurs in an UCP2-dependent manner. Our study demonstrated that the activation of PPAR-γ by pioglitazone protected against oxidative stress damage in aging cerebral arteries by upregulating UCP2. PPAR-γ may be a new target in treating age-related cerebrovascular dysfunction.

Metformin: do we finally have an anti-aging drug?

Studies in mammals have demonstrated that hyperglycemia and hyperinsulinemia are important factors in aging and cancer. Inactivation of insulin/insulin-like signaling increases lifespan in nematodes, fruit flies, and mice. Life-prolonging effects of caloric restriction are in part due to reduction in IGF-1, insulin, and glucose levels. Antidiabetic biguanides such as metformin, which reduce hyperglycemia and hyperinsulinemia by decreasing insulin resistance, extend lifespan, and inhibit carcinogenesis in rodents. Will antidiabetic biguanides increase lifespan in humans?

Pharmacological lifespan extension of invertebrates

There is considerable interest in identifying small, drug-like compounds that slow aging in multiple species, particularly in mammals. Such compounds may prove to be useful in treating and retarding age-related disease in humans. Just as invertebrate models have been essential in helping us understand the genetic pathways that control aging, these model organisms are also proving valuable in discovering chemical compounds that influence longevity. The nematode Caenorhabditis elegans has numerous advantages for such studies including its short lifespan and has been exploited by a number of investigators to find compounds that impact aging. Here, we summarize the progress being made in identifying compounds that extend the lifespan of invertebrates, and introduce the challenges we face in translating this research into human therapies.

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.

Activation of AMPK by the putative dietary restriction mimetic metformin is insufficient to extend lifespan in Drosophila

The biguanide drug, metformin, commonly used to treat type-2 diabetes, has been shown to extend lifespan and reduce fecundity in C. elegans through a dietary restriction-like mechanism via the AMP-activated protein kinase (AMPK) and the AMPK-activating kinase, LKB1. We have investigated whether the longevity-promoting effects of metformin are evolutionarily conserved using the fruit fly, Drosophila melanogaster. We show here that while feeding metformin to adult Drosophila resulted in a robust activation of AMPK and reduced lipid stores, it did not increase lifespan in either male or female flies. In fact, we found that when administered at high concentrations, metformin is toxic to flies. Furthermore, no decreases in female fecundity were observed except at the most toxic dose. Analysis of intestinal physiology after metformin treatment suggests that these deleterious effects may result from disruptions to intestinal fluid homeostasis. Thus, metformin appears to have evolutionarily conserved effects on metabolism but not on fecundity or lifespan.

In silico drug screen in mouse liver identifies candidate calorie restriction mimetics

Calorie restriction (CR) extends life span in mammals and delays the onset of age-related diseases, including cancer and diabetes. Drugs that target the same genes and pathways as CR may have enormous therapeutic potential. Recently, genome-scale data on the responses of human cell lines to over 1,000 drug treatments have become available. Here we integrate these data with gene expression signatures of CR in mouse liver to generate a prioritized list of candidate CR mimetics. We identify 14 drugs that reproduce the effects of CR at the transcriptional level.

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.

Long-term functional side-effects of stimulants and sedatives in Drosophila melanogaster

BACKGROUND

Small invertebrate animals, such as nematodes and fruit flies, are increasingly being used to test candidate drugs both for specific therapeutic purposes and for long-term health effects. Some of the protocols used in these experiments feature such experimental design features as lifelong virginity and very low densities. By contrast, the ability of both fruit flies and nematodes to resist stress is frequently correlated with their longevity and other functional measures, suggesting that low-stress assays are not necessarily the only useful protocol for testing the long-term effects of drugs.

METHODOLOGY/PRINCIPAL FINDINGS

Here we report an alternative protocol for fruit fly drug-testing that maximizes reproductive opportunities and other types of interaction, with moderately high population densities. We validate this protocol using two types of experimental tests: 1. We show that this protocol detects previously well-established genetic differences between outbred fruit fly populations. 2. We show that this protocol is able to distinguish among the long-term effects of similar types of drugs within two broad categories, stimulants and tranquilizers.

CONCLUSIONS

Large-scale fly drug testing can be conducted using mixed-sex high-density cage assays. We find that the commonly-used stimulants caffeine and theobromine differ dramatically in their chronic functional effects, theobromine being more benign. Likewise, we find that two generic pharmaceutical tranquilizers, lithium carbonate and valproic acid, differ dramatically in their chronic effects, lithium being more benign. However, these findings do not necessarily apply to human subjects, and we thus do not recommend the use of any one substance over any other.

Can Drosophila melanogaster represent a model system for the detection of reproductive adverse drug reactions?

Once a molecule is identified as a potential drug, the detection of adverse drug reactions is one of the key components of its development and the FDA approval process. We propose using Drosophila melanogaster to screen for reproductive adverse drug reactions in the early stages of drug development. Compared with other non-mammalian models, D. melanogaster has many similarities to the mammalian reproductive system, including putative sex hormones and conserved proteins involved in genitourinary development. Furthermore, the D. melanogaster model would present significant advantages in time efficiency and cost-effectiveness compared with mammalian models. We present data on methotrexate (MTX) reproductive adverse events in multiple animal models, including fruit flies, as proof-of-concept for the use of the D. melanogaster model.

Lamotrigine extends lifespan but compromises health span in Drosophila melanogaster

The discovery of life extension in Caenorhabditis elegans treated with anticonvulsant medications has raised the question whether these drugs are prospective anti-aging candidate compounds. The impact of these compounds on neural modulation suggests that they might influence the chronic diseases of aging as well. Lamotrigine is a commonly used anticonvulsant with a relatively good adverse-effects profile. In this study, we evaluated the interaction between the impacts of lamotrigine on mortality rate, lifespan, metabolic rate and locomotion. It has been proposed in a wide range of animal models that there is an inverse relationship between longevity, metabolic rate, and locomotion. We hypothesized that the survival benefits displayed by this compound would be associated with deleterious effects on health span, such as depression of locomotion. Using Drosophila as our model system, we found that lamotrigine decreased mortality and increased lifespan in parallel with a reduction in locomotor activity and a trend towards metabolic rate depression. Our findings underscore the view that assessing health span is critical in the pursuit of useful anti-aging compounds.

Rosa damascena decreased mortality in adult Drosophila

The effects of a rose-flower extract, Rosa damascena, on the mortality rate of Drosophila melanogaster was evaluated in this study. R. damascena is a potent antioxidant that has many therapeutic uses in addition to its perfuming effects. Supplementing Drosophila with this rose extract resulted in a statistically significant decrease in mortality rate in male and female flies. Moreover, the observed anti-aging effects were not associated with common confounds of anti-aging properties, such as a decrease in fecundity or metabolic rate.