Some highlights of research on aging with invertebrates, 2010

Cross-Species and Human Inter-Tissue Network Analysis of Genes Implicated in Longevity and Aging Reveal Strong Support for Nutrient Sensing

Intensive research efforts have been undertaken to slow human aging and therefore potentially delay the onset of age-related diseases. These efforts have generated an enormous amount of high-throughput data covering different levels in the physiologic hierarchy, e.g., genetic, epigenetic, transcriptomic, proteomic, and metabolomic, etc. We gathered 15 independent sources of information about genes potentially involved in human longevity and lifespan (N = 5836) and subjected them to various integrated analyses. Many of these genes were initially identified in non-human species, and we investigated their orthologs in three non-human species [i.e., mice (N = 967), fruit fly (N = 449), and worm (N = 411)] for further analysis. We characterized experimentally determined protein-protein interaction networks (PPIN) involving each species' genes from 9 known protein databases and studied the enriched biological pathways among the individually constructed PPINs. We observed three important signaling pathways: FoxO signaling, mTOR signaling, and autophagy to be common and highly enriched in all four species (p-value ≤ 0.001). Our study implies that the interaction of proteins involved in the mechanistic target of rapamycin (mTOR) signaling pathway is somewhat limited to each species or that a "rewiring" of specific networks has taken place over time. To corroborate our findings, we repeated our analysis in 43 different human tissues. We investigated conserved modules in various tissue-specific PPINs of the longevity-associated genes based upon their protein expression. This analysis also revealed mTOR signaling as shared biological processes across four different human tissue-specific PPINs for liver, heart, skeletal muscle, and adipose tissue. Further, we explored our results' translational potential by assessing the protein interactions with all the reported drugs and compounds that have been experimentally verified to promote longevity in the three-comparator species. We observed that the target proteins of the FDA-approved drug rapamycin (a known inhibitor of mTOR) were conserved across all four species. Drugs like melatonin and metformin exhibited shared targets with rapamycin in the human PPIN. The detailed information about the curated gene list, cross-species orthologs, PPIN, and pathways was assembled in an interactive data visualization portal using RStudio's Shiny framework (https://agingnetwork.shinyapps.io/frontiers/).

Dietary restriction improves intestinal cellular fitness to enhance gut barrier function and lifespan in D. melanogaster

Loss of gut integrity is linked to various human diseases including inflammatory bowel disease. However, the mechanisms that lead to loss of barrier function remain poorly understood. Using D. melanogaster, we demonstrate that dietary restriction (DR) slows the age-related decline in intestinal integrity by enhancing enterocyte cellular fitness through up-regulation of dMyc in the intestinal epithelium. Reduction of dMyc in enterocytes induced cell death, which leads to increased gut permeability and reduced lifespan upon DR. Genetic mosaic and epistasis analyses suggest that cell competition, whereby neighboring cells eliminate unfit cells by apoptosis, mediates cell death in enterocytes with reduced levels of dMyc. We observed that enterocyte apoptosis was necessary for the increased gut permeability and shortened lifespan upon loss of dMyc. Furthermore, moderate activation of dMyc in the post-mitotic enteroblasts and enterocytes was sufficient to extend health-span on rich nutrient diets. We propose that dMyc acts as a barometer of enterocyte cell fitness impacting intestinal barrier function in response to changes in diet and age.

Drosophila melanogaster as a Model for Diabetes Type 2 Progression

Drosophila melanogaster has been used as a very versatile and potent model in the past few years for studies in metabolism and metabolic disorders, including diabetes types 1 and 2. Drosophila insulin signaling, despite having seven insulin-like peptides with partially redundant functions, is very similar to the human insulin pathway and has served to study many different aspects of diabetes and the diabetic state. Yet, very few studies have addressed the chronic nature of diabetes, key for understanding the full-blown disease, which most studies normally explore. One of the advantages of having Drosophila mutant viable combinations at different levels of the insulin pathway, with significantly reduced insulin pathway signaling, is that the abnormal metabolic state can be studied from the onset of the life cycle and followed throughout. In this review, we look at the chronic nature of impaired insulin signaling. We also compare these results to the results gleaned from vertebrate model studies.

The Contribution of Oxidative Stress and Inflamm-Aging in Human and Equine Asthma

Aging is associated with a dysregulation of the immune system, leading to a general pro-inflammatory state of the organism, a process that has been named inflamm-aging. Oxidative stress has an important role in aging and in the regulation of immune responses, probably playing a role in the development of age-related diseases. The respiratory system function physiologically declines with the advancement of age. In elderly asthmatic patients, this may contribute to disease expression. In this review, we will focus on age-related changes affecting the immune system and in respiratory structure and function that could contribute to asthma occurrence, and/or clinical presentation in the elderly. Also, naturally occurring equine asthma will be discussed as a possible model for studying the importance of oxidative stress and immun-aging/inflamm-aging in humans.

Modulation of telomere protection by the PI3K/AKT pathway

Telomeres and the insulin/PI3K pathway are considered hallmarks of aging and cancer. Here, we describe a role for PI3K/AKT in the regulation of TRF1, an essential component of the shelterin complex. PI3K and AKT chemical inhibitors reduce TRF1 telomeric foci and lead to increased telomeric DNA damage and fragility. We identify the PI3Kα isoform as responsible for this TRF1 inhibition. TRF1 is phosphorylated at different residues by AKT and these modifications regulate TRF1 protein stability and TRF1 binding to telomeric DNA in vitro and are important for in vivo TRF1 telomere location and cell viability. Patient-derived breast cancer PDX mouse models that effectively respond to a PI3Kα specific inhibitor, BYL719, show decreased TRF1 levels and increased DNA damage. These findings functionally connect two of the major pathways for cancer and aging, telomeres and the PI3K pathway, and pinpoint PI3K and AKT as novel targets for chemical modulation of telomere protection.

Regulation of telomeres and the insulin/PI3K pathway both have roles in aging and cancer development but have not been functionally linked. Here the authors demonstrate that PI3K, via downstream targets, regulates TRF1 via phosphorylation.

Age-Dependent Protein Aggregation Initiates Amyloid-β Aggregation

Aging is the most important risk factor for neurodegenerative diseases associated with pathological protein aggregation such as Alzheimer's disease. Although aging is an important player, it remains unknown which molecular changes are relevant for disease initiation. Recently, it has become apparent that widespread protein aggregation is a common feature of aging. Indeed, several studies demonstrate that 100s of proteins become highly insoluble with age, in the absence of obvious disease processes. Yet it remains unclear how these misfolded proteins aggregating with age affect neurodegenerative diseases. Importantly, several of these aggregation-prone proteins are found as minor components in disease-associated hallmark aggregates such as amyloid-β plaques or neurofibrillary tangles. This co-localization raises the possibility that age-dependent protein aggregation directly contributes to pathological aggregation. Here, we show for the first time that highly insoluble proteins from aged Caenorhabditis elegans or aged mouse brains, but not from young individuals, can initiate amyloid-β aggregation in vitro. We tested the seeding potential at four different ages across the adult lifespan of C. elegans. Significantly, protein aggregates formed during the early stages of aging did not act as seeds for amyloid-β aggregation. Instead, we found that changes in protein aggregation occurring during middle-age initiated amyloid-β aggregation. Mass spectrometry analysis revealed several late-aggregating proteins that were previously identified as minor components of amyloid-β plaques and neurofibrillary tangles such as 14-3-3, Ubiquitin-like modifier-activating enzyme 1 and Lamin A/C, highlighting these as strong candidates for cross-seeding. Overall, we demonstrate that widespread protein misfolding and aggregation with age could be critical for the initiation of pathogenesis, and thus should be targeted by therapeutic strategies to alleviate neurodegenerative diseases.

The roles of the nuclear pore complex in cellular dysfunction, aging and disease

The study of the Nuclear Pore Complex (NPC), the proteins that compose it (nucleoporins), and the nucleocytoplasmic transport that it controls have revealed an unexpected layer to pathogenic disease onset and progression. Recent advances in the study of the regulation of NPC composition and function suggest that the precise control of this structure is necessary to prevent diseases from arising or progressing. Here we discuss the role of nucleoporins in a diverse set of diseases, many of which directly or indirectly increase in occurrence and severity as we age, and often shorten the human lifespan. NPC biology has been shown to play a direct role in these diseases and therefore in the process of healthy aging.

AxGxE: Using Flies to Interrogate the Complex Etiology of Neurodegenerative Disease

Progressive and late-onset neurological disorders such as Parkinson's disease and Alzheimer's disease affect up to 50 million people globally-a number postulated to double every 20 years in a continually aging population. While predisposing allelic variants in several genes clearly confer risk, individual age and specific environmental influences are equally important discriminators of disease onset age and progression. However, none of these factors can independently predict disease with significant precision. Therefore, we must actively develop models that accommodate contributions from all factors, potentially resulting in an A × G × E (age-gene-environment) metric that reflects individual cumulative risk and reliably forecasts disease outcomes. This effort can only be enabled by a deep quantitative understanding of the contribution of these factors to neurodegenerative disease, both individually and in combination. This is also an important consideration because neuronal loss typically precedes clinical presentation and disease-modifying therapies are contingent on early diagnosis that is likely to be informed by an accurate estimation of individual risk. Although epidemiological studies continue to make strong advances in these areas with the advent of powerful "omics"-based approaches, systematic phenotypic modeling of AxGxE interactions is currently more feasible in model organisms such as Drosophila melanogaster where all three parameters can be manipulated with manageable experimental burden. Here, we outline the advantages of using fruit flies for investigating these complex interactions and highlight potential approaches that might help synthesize existing information from diverse fields into a cogent description of age-dependent, environmental, and genetic risk factors in the pathophysiology of neurological disorders.

New perspectives on dietary-derived treatments and food safety-antinomy in a new era

Despite the advances in science and technology and wide use of chemical drugs, dietary intervention (or food therapy) remains useful in preventing or treating many human diseases. A huge body of evidence shows that the dietary pattern or habit is also an important contributing factor to the development of chronic diseases such as hypertension, type 2 diabetes, hyperlipidemia, and cancers. In recent years, over-the-counter health foods, nutraceuticals, and plant-derived medicinal products have been gaining popularity all over the world, particularly in developed countries. Unfortunately, owing to the contamination with various harmful substances in foods and the presence of toxic food components, food-borne diseases have also become increasingly problematic. Incidents of food poisonings or tainted food have been increasing worldwide, particularly in China and other developing countries. Therefore, the government should put in a greater effort in enforcing food safety by improving the surveillance mechanism and exerting highest standards of quality control for foods.

Gut microbiota lipopolysaccharide accelerates inflamm-aging in mice

BACKGROUND

The constitutive inflammation that characterizes advanced age is termed inflamm-aging. This process is associated with age-related changes to immune homeostasis and gut microbiota. We investigated the relationship between aging and gut microbiota lipopolysaccharide (LPS)-inducible inflammation.

RESULTS

A taxonomy-based analysis showed that aging resulted in increased prevalence of the phyla Firmicutes and Actinobacteria and a reduced prevalence of Bacteroidetes and Tenericutes, resulting in an increase in the Firmicutes to Bacteroidetes ratio. The levels of plasmatic and fecal lipopolysaccharides were higher in aged mice. Aging induced the expression of p16 and the activation of nuclear factor-kappa B (NF-κB) in the colon of aged mice. Interestingly, the expression level of sterile α-motif domain- and HD domain-containing protein 1 (SAMHD1) in the colon was higher in aged mice than in young mice, while cyclin-dependent kinase-2 and cyclin E levels were lower in aged mice than in young mice. The lipopolysaccharide fraction of fecal lysates (LFL) from young or aged mice increased p16 and SAMHD1 expression and NF-κB activation in peritoneal macrophages from wild-type mice, in a TLR4-dependent manner. However, LFLs did not induce NF-κB activation and SAMHD1 expression in peritoneal macrophages from TLR4-deificent mice, whereas they significantly induced p16 expression. Nevertheless, p16 expression was induced more potently in macrophages from WT mice than in macrophages from TLR4-deficient mice.

CONCLUSION

Aging increased p16 and SAMHD1 expression, gut microbiota LPS production, and NF-κB activation; thereby, signifying that gut microbiota LPS may accelerate inflamm-aging and SAMHD1 may be an inflamm-aging marker.

The Interplay Between Respiratory Supercomplexes and ROS in Aging

SIGNIFICANCE

The molecular mechanism of aging is still vigorously debated, although a general consensus exists that mitochondria are significantly involved in this process. However, the previously postulated role of mitochondrial-derived reactive oxygen species (ROS) as the damaging agents inducing functional loss in aging has fallen out of favor in the recent past. In this review, we critically examine the role of ROS in aging in the light of recent advances on the relationship between mitochondrial structure and function.

RECENT ADVANCES

The functional mitochondrial respiratory chain is now recognized as a reflection of the dynamic association of respiratory complexes in the form of supercomplexes (SCs). Besides providing kinetic advantage (channeling), SCs control ROS generation by the respiratory chain, thus providing a means to regulate ROS levels in the cell. Depending on their concentration, these ROS are either physiological signals essential for the life of the cell or toxic species that damage cell structure and functions.

CRITICAL ISSUES

We propose that under physiological conditions the dynamic nature of SCs reversibly controls the generation of ROS as signals involved in mitochondrial-nuclear communication. During aging, there is a progressive loss of control of ROS generation so that their production is irreversibly enhanced, inducing a vicious circle in which signaling is altered and structural damage takes place.

FUTURE DIRECTIONS

A better understanding on the forces affecting SC association would allow the manipulation of ROS generation, directing these species to their physiological signaling role.

Role of Toll-like receptor 2 and 4 signaling pathways on the inflammatory response to resistance training in elderly subjects

This study assessed the effects of a resistance exercise training program on the inflammatory response associated with Toll-like receptor (TLR) 2 and TLR4 signaling pathways in senior participants. Twenty-six healthy subjects (age, 69.5 ± 1.3) were randomized to a training (TG; n = 16) or a control (CG; n = 10) group. TG performed an 8-week resistance training program, while CG followed their daily routines. Peripheral blood mononuclear cells were isolated from blood samples obtained before and after the intervention, and levels of proteins involved in the TLR2, TLR4, and myeloid differentiation primary response gene 88 (MyD88)-dependent and MyD88-independent pathways were analyzed. The inflammatory status was evaluated through messenger RNA (mRNA) and protein content of interleukin (IL)-10 and tumor necrosis factor alpha (TNF-α) and plasma levels of C-reactive protein (CRP). After the 8-week resistance training, TLR2 and TLR4 protein expression was reduced in TG. MyD88, p65, phospho-p38, TIR domain-containing adaptor inducing interferon (TRIF), IKKi/IKKε, phospho-interferon regulatory factor (IRF) 3, and phosho-IRF7 were also downregulated in TG after the intervention. The training program induced an increase of phospho-extracellular signal-regulated kinases 1 and 2 (ERK1/2) and Hsp70 and a reduction of Hsp60. While TNF-α mRNA and protein values remained unchanged in both TG and CG, IL-10 mRNA and protein content were upregulated in TG after the intervention. CRP values decreased in TG only. The increase in Hsp70 negatively correlated with TLR2 and TLR4 downregulation. These data suggest that resistance exercise may represent an effective tool to ameliorate the pro-inflammatory status of old participants through an attenuation of MyD88-dependent and MyD88-independent TLR2 and TLR4 signaling pathways.

Do we age because we have mitochondria?

The process of aging remains a great riddle. Production of reactive oxygen species (ROS) by mitochondria is an inevitable by-product of respiration, which has led to a hypothesis proposing the oxidative impairment of mitochondrial components (e.g., mtDNA, proteins, lipids) that initiates a vicious cycle of dysfunctional respiratory complexes producing more ROS, which again impairs function. This does not exclude other processes acting in parallel or targets for ROS action in other organelles than mitochondria. Given that aging is defined as the process leading to death, the role of mitochondria-based impairments in those organ systems responsible for human death (e.g., the cardiovascular system, cerebral dysfunction, and cancer) is described within the context of "garbage" accumulation and increasing insulin resistance, type 2 diabetes, and glycation of proteins. Mitochondrial mass, fusion, and fission are important factors in coping with impaired function. Both biogenesis of mitochondria and their degradation are important regulatory mechanisms stimulated by physical exercise and contribute to healthy aging. The hypothesis of mitochondria-related aging should be revised to account for the limitations of the degradative capacity of the lysosomal system. The processes involved in mitochondria-based impairments are very similar across a large range of organisms. Therefore, studies on model organisms from yeast, fungi, nematodes, flies to vertebrates, and from cells to organisms also add considerably to the understanding of human aging.

Dramatic fertility decline in aging C. elegans males is associated with mating execution deficits rather than diminished sperm quality

Although much is known about female reproductive aging, fairly little is known about the causes of male reproductive senescence. We developed a method that facilitates culture maintenance of Caenorhabditis elegans adult males, which enabled us to measure male fertility as populations age, without profound loss of males from the growth plate. We find that the ability of males to sire progeny declines rapidly in the first half of adult lifespan and we examined potential factors that contribute towards reproductive success, including physical vigor, sperm quality, mating apparatus morphology, and mating ability. Of these, we find little evidence of general physical decline in males or changes in sperm number, morphology, or capacity for activation, at time points when reproductive senescence is markedly evident. Rather, it is the loss of efficient mating ability that correlates most strongly with reproductive senescence. Low insulin signaling can extend male ability to sire progeny later in life, although insulin impact on individual facets of mating behavior is complex. Overall, we suggest that combined modest deficits, predominantly affecting the complex mating behavior rather than sperm quality, sum up to block effective C. elegans male reproduction in middle adult life.

Dietary restriction extends lifespan in wild-derived populations of Drosophila melanogaster

Dietary restriction (DR) can result in lifespan-extension and improved function and health during ageing. Although the impact of DR on lifespan and health has been established in a variety of organisms, most DR experiments are carried out on laboratory strains that have often undergone adaptation to laboratory conditions. The effect of DR on animals recently derived from wild populations is rarely assessed. We measured the DR response of four populations of Drosophila melanogaster within two generations of collection from the wild. All populations responded to DR with an increase in lifespan and a decrease in female fecundity, similarly to a control, laboratory-adapted strain. These effects of DR are thus not a result of adaptation to laboratory conditions, and reflect the characteristics of natural populations.

The Saccharomyces cerevisiae W303-K6001 cross-platform genome sequence: insights into ancestry and physiology of a laboratory mutt

Saccharomyces cerevisiae strain W303 is a widely used model organism. However, little is known about its genetic origins, as it was created in the 1970s from crossing yeast strains of uncertain genealogy. To obtain insights into its ancestry and physiology, we sequenced the genome of its variant W303-K6001, a yeast model of ageing research. The combination of two next-generation sequencing (NGS) technologies (Illumina and Roche/454 sequencing) yielded an 11.8 Mb genome assembly at an N50 contig length of 262 kb. Although sequencing was substantially more precise and sensitive than whole-genome tiling arrays, both NGS platforms produced a number of false positives. At a 378× average coverage, only 74 per cent of called differences to the S288c reference genome were confirmed by both techniques. The consensus W303-K6001 genome differs in 8133 positions from S288c, predicting altered amino acid sequence in 799 proteins, including factors of ageing and stress resistance. The W303-K6001 (85.4%) genome is virtually identical (less than equal to 0.5 variations per kb) to S288c, and thus originates in the same ancestor. Non-S288c regions distribute unequally over the genome, with chromosome XVI the most (99.6%) and chromosome XI the least (54.5%) S288c-like. Several of these clusters are shared with Σ1278B, another widely used S288c-related model, indicating that these strains share a second ancestor. Thus, the W303-K6001 genome pictures details of complex genetic relationships between the model strains that date back to the early days of experimental yeast genetics. Moreover, this study underlines the necessity of combining multiple NGS and genome-assembling techniques for achieving accurate variant calling in genomic studies.

mTOR Inhibition: From Aging to Autism and Beyond

The mechanistic target of rapamycin (mTOR) is a highly conserved protein that regulates growth and proliferation in response to environmental and hormonal cues. Broadly speaking, organisms are constantly faced with the challenge of interpreting their environment and making a decision between "grow or do not grow." mTOR is a major component of the network that makes this decision at the cellular level and, to some extent, the tissue and organismal level as well. Although overly simplistic, this framework can be useful when considering the myriad functions ascribed to mTOR and the pleiotropic phenotypes associated with genetic or pharmacological modulation of mTOR signaling. In this review, I will consider mTOR function in this context and attempt to summarize and interpret the growing body of literature demonstrating interesting and varied effects of mTOR inhibitors. These include robust effects on a multitude of age-related parameters and pathologies, as well as several other processes not obviously linked to aging or age-related disease.

Epidemiological, genetic and epigenetic aspects of the research on healthy ageing and longevity

Healthy ageing and longevity in humans result from a number of factors, including genetic background, favorable environmental and social factors and chance.

In this article we aimed to overview the research on the biological basis of human healthy ageing and longevity, discussing the role of epidemiological, genetic and epigenetic factors in the variation of quality of ageing and lifespan, including the most promising candidate genes investigated so far. Moreover, we reported the methodologies applied for their identification, discussing advantages and disadvantages of the different approaches and possible solutions that can be taken to overcome them. Finally, we illustrated the recent approaches to define healthy ageing and underlined the role that the emerging field of epigenetics is gaining in the search for the determinants of healthy ageing and longevity.

Linkage of cardiac gene expression profiles and ETS2 with lifespan variability in rats

Longevity variability is a common feature of aging in mammals, but the mechanisms responsible for this remain largely unknown. Using microarray datasets coupled with prediction analysis of microarrays (PAM), we identified a set of 252 cardiac transcripts predictive of relative lifespan in Wistar and Fisher 344 rats. Prediction analysis of microarrays 'tests' of rat heart transcriptomes from a third longer lived Fisher × Norway Brown rat strain validated the predictive value of this gene subset. The expression patterns of these genes were highly conserved, and corresponding promoter regions were employed to identify common cis-elements and trans-activating factors implicated in their control. Specifically, four transcription factors (Max, Ets2, Erg, and Msx2) present in heart displayed longevity-dependent, strain-independent changes in abundance, but only ETS2 had an expression profile that directly correlated with the relative lifespan gene set. In heart, ETS2 was prevalent in cardiomyocytes (CMs) and showed a high degree of myocyte-to-myocyte variability predominantly in adult rat hearts prior to the exponential increase in the rate of mortality. Exclusively in this group, elevated ETS2 significantly overlapped with TUNEL staining in heart myocytes. In response to sympathetic stimuli, ETS2 is also up-regulated, and functionally, adenovirus-mediated over-expression of ETS2 promotes apoptosis-inducing factor-mediated, caspase-independent programmed necrosis exclusively in CMs that can be fully inhibited by the PARP-1 inhibitor DPQ. We conclude that variations in ETS2 abundance in hearts of adult rodents and the associated loss of CMs contribute at least partially, to the longevity variability observed during normal aging of rats through activation of programmed necrosis.

Functional analyses of human DNA repair proteins important for aging and genomic stability using yeast genetics

Model systems have been extremely useful for studying various theories of aging. Studies of yeast have been particularly helpful to explore the molecular mechanisms and pathways that affect aging at the cellular level in the simple eukaryote. Although genetic analysis has been useful to interrogate the aging process, there has been both interest and debate over how functionally conserved the mechanisms of aging are between yeast and higher eukaryotes, especially mammalian cells. One area of interest has been the importance of genomic stability for age-related processes, and the potential conservation of proteins and pathways between yeast and human. Translational genetics have been employed to examine the functional roles of mammalian proteins using yeast as a pliable model system. In the current review recent advancements made in this area are discussed, highlighting work which shows that the cellular functions of human proteins in DNA repair and maintenance of genomic stability can be elucidated by genetic rescue experiments performed in yeast.

Ischemic preconditioning: the role of mitochondria and aging

Aging represents a triple threat for myocardial infarction (MI). Not only does the incidence of MI increase with age, but the heart becomes more susceptible to MI induced damage and protective interventions such as ischemic preconditioning (IPC) become less effective. Therefore, any rational therapeutic strategy must be built around the ability to combat the detrimental effects of ischemia in aged individuals. To accomplish this, we need to develop a better understanding of how ischemic damage, protection, and aging are linked. In this regard, mitochondria have emerged as a common theme. First, mitochondria contribute to cell damage during ischemia-reperfusion (IR) and are central to cell death. Second, the protective signaling pathways activated by IPC converge on mitochondria, and the opening of mitochondrial ion channels alone is sufficient to elicit protection. Finally, mitochondria clearly influence the aging process, and specific defects in mitochondrial activity are associated with age-related functional decline. This review will summarize the effects of aging on myocardial IR injury and discuss relevant and emerging strategies to protect against MI with an emphasis on mitochondrial function.

RNAi screening: new approaches, understandings, and organisms

RNA interference (RNAi) leads to sequence-specific knockdown of gene function. The approach can be used in large-scale screens to interrogate function in various model organisms and an increasing number of other species. Genome-scale RNAi screens are routinely performed in cultured or primary cells or in vivo in organisms such as C. elegans. High-throughput RNAi screening is benefitting from the development of sophisticated new instrumentation and software tools for collecting and analyzing data, including high-content image data. The results of large-scale RNAi screens have already proved useful, leading to new understandings of gene function relevant to topics such as infection, cancer, obesity, and aging. Nevertheless, important caveats apply and should be taken into consideration when developing or interpreting RNAi screens. Some level of false discovery is inherent to high-throughput approaches and specific to RNAi screens, false discovery due to off-target effects (OTEs) of RNAi reagents remains a problem. The need to improve our ability to use RNAi to elucidate gene function at large scale and in additional systems continues to be addressed through improved RNAi library design, development of innovative computational and analysis tools and other approaches.

High glucose diets shorten lifespan of Caenorhabditis elegans via ectopic apoptosis induction

Diets based on carbohydrates increase rapidly the blood glucose level due to the fast conversion of carbohydrates to glucose. High glucose diets have been known to induce many lifestyle diseases. Here, we demonstrated that high glucose diet shortened the lifespan of Caenorhabditis elegans through apoptosis induction. Control adult groups without glucose diet lived for 30 days, whereas animals fed 10 mg/L of D-glucose lived only for 20 days. The reduction of lifespan by glucose diet showed a dose-dependent profile in the concentration range of glucose from 1 to 20 mg/L. Aging effect of high glucose diet was examined by measurement of response time for locomotion after stimulating movement of the animals by touching. Glucose diet decreased the locomotion capacity of the animals during mid-adulthood. High glucose diets also induced ectopic apoptosis in the body of C. elegans, which is a potent mechanism that can explain the shortened lifespan and aging. Apoptotic cell corpses stained with SYTO 12 were found in the worms fed 10 mg/L of glucose. Mutation of core apoptotic regulatory genes, CED-3 and CED-4, inhibited the reduction of viability induced by high glucose diet, which indicates that these regulators were required for glucose-induced apoptosis or lifespan shortening. Thus, we conclude that high glucose diets have potential for inducing ectopic apoptosis in the body, resulting in a shortened lifespan accompanied with loss of locomotion capacity.

Oxidative stress, inflamm-aging and immunosenescence

Immunosenescence is characterized by a decreased ability of the immune system to respond to foreign antigens, as well as a decreased ability to maintain tolerance to self-antigens. This results in an increased susceptibility to infection and cancer and reduced responses to vaccination [1-5]. The mechanisms underlying immunosenescence comprise a series of cellular and molecular events involving alteration of several biochemical pathways and different cellular populations, and for the most part our understanding of these molecular mechanisms is still fragmentary. In this review we will focus on the process of senescence associated with oxidative stress, in particular how protein oxidation alters the functionality of immune cells and how oxidative stress contributes to a chronic inflammatory process often referred as inflamm-aging.