An insulin-like signaling pathway affects both longevity and reproduction in Caenorhabditis elegans

Activated SKN-1 alters the aging trajectories of long-lived Caenorhabditis elegans mutants

In the presence of stressful environments, the SKN-1 cytoprotective transcription factor is activated to induce the expression of gene targets that can restore homeostasis. However, chronic activation of SKN-1 results in diminished health and a reduction of lifespan. Here, we demonstrate the necessity of modulating SKN-1 activity to maintain the longevity-promoting effects associated with genetic mutations that impair daf-2/insulin receptor signaling, the eat-2 model of dietary restriction, and glp-1-dependent loss of germ cell proliferation. A hallmark of animals with constitutive SKN-1 activation is the age-dependent loss of somatic lipids, and this phenotype is linked to a general reduction in survival in animals harboring the skn-1gf allele. Surprisingly, daf-2lf; skn-1gf double mutant animals do not redistribute somatic lipids, which suggests the insulin signaling pathway functions downstream of SKN-1 in the maintenance of lipid distribution. As expected, the eat-2lf allele, which independently activates SKN-1, continues to display somatic lipid depletion in older ages with and without the skn-1gf activating mutation. In contrast, the presence of the skn-1gf allele does not lead to somatic lipid redistribution in glp-1lf animals that lack a proliferating germline. Taken together, these studies support a genetic model where SKN-1 activity is an important regulator of lipid mobilization in response to nutrient availability that fuels the developing germline by engaging the daf-2/insulin receptor pathway.

Harnessing the Potential of Walnut Leaves from Nerpio: Unveiling Extraction Techniques and Bioactivity Through Caenorhabditis elegans Studies

This study used Juglans regia leaves from the Gran Jefe variety; this indigenous cultivar from Nerpio is highly valued for its quality and distinct characteristics. This type of walnut is traditionally cultivated in the region and is noted for its organoleptic properties and adaptation to local climatic conditions. Two solvents were tested to determine the optimal extraction conditions for phenolic compounds: 80% ethanol and water. Direct homogenization with an Ultra-Turrax, direct ultrasound, and indirect ultrasound treatments were compared for ethanol extraction. Water extractions were conducted using direct and indirect ultrasound, infusion, and decoction. Compared to water extraction, 80% ethanol proved to be more efficient. Extracting phenolic compounds from 'Gran Jefe' walnut leaves was most effective when using direct extraction methods without either ultrasound assistance or indirect ultrasound treatment. The main compounds identified were trans-3-caffeoylquinic acid and quercetin-3-hexoside isomer 1. The ethanolic extract obtained through direct extraction was selected to study further the bioactivities of 'Gran Jefe' walnut leaves using C. elegans as an in vivo model. Results indicated that the leaf extract enhanced thermal and oxidative stress resistance, promoted fertility, and exhibited neuroprotective effects in models of Alzheimer's and Parkinson's diseases. The observed bioactivities were attributed to the free phenolics present in the ethanolic extract.

Phosphorylation of an RNA-Binding Protein Rck/Me31b by Hippo Is Essential for Adipose Tissue Aging

The metazoan lifespan is determined in part by a complex signaling network that regulates energy metabolism and stress responses. Key signaling hubs in this network include insulin/IGF-1, AMPK, mTOR, and sirtuins. The Hippo/Mammalian Ste20-like Kinase1 (MST1) pathway has been reported to maintain lifespan in Caenorhabditis elegans, but its role has not been studied in higher metazoans. In this study, we report that overexpression of Hpo, the MST1 homolog in Drosophila melanogaster, decreased lifespan with concomitant changes in lipid metabolism and aging-associated gene expression, while RNAi Hpo depletion increased lifespan. These effects were mediated primarily by Hpo-induced transcriptional activation of the RNA-binding protein maternal expression at 31B (Me31b)/RCK, resulting in stabilization of mRNA-encoding a lipolytic hormone, Akh. In mouse adipocytes, Hpo/Mst1 mediated adipocyte differentiation, phosphorylation of RNA-binding proteins such as Rck, decapping MRNA 2 (Dcp2), enhancer Of MRNA decapping 3 (Edc3), nucleolin (NCL), and glucagon mRNA stability by interacting with Rck. Decreased lifespan in Hpo-overexpressing Drosophila lines required expression of Me31b, but not DCP2, which was potentially mediated by recovering expression of lipid metabolic genes and formation of lipid droplets. Taken together, our findings suggest that Hpo/Mst1 plays a conserved role in longevity by regulating adipogenesis and fatty acid metabolism.

Mitochondrial Proteome Reveals Metabolic Tuning by Restricted Insulin Signaling to Promote Longevity in Caenorhabditis elegans

Aging is a time-dependent process of functional decline influenced by genetic and environmental factors. Age-related mitochondrial changes remain incompletely understood. Here, we found that compared to the wild type, the mitochondria of long-lived daf-2 C. elegans maintain youthful morphology and function. Through quantitative proteomic analysis on isolated mitochondria, we identified 257 differentially expressed candidates. Analysis of these changed mitochondrial proteins reveals a significant upregulation of five key mitochondrial metabolic pathways in daf-2 mutants, including branched-chain amino acids (BCAA), reactive oxygen species (ROS), propionate, β-alanine, and fatty acids (FA), all of which are related to daf-2-mediated longevity. In addition, mitochondrial ribosome protein abundance slightly decreased in daf-2 mutants. A mild reduction in mitochondrial elongation factor G (gfm-1) by RNAi extends the lifespan of wild type while decreasing lipid metabolic process and cytoplasmic fatty acid metabolism, suggesting that proper inhibition of mitochondrial translation activity might be important for lifespan extension. Overall, our findings indicate that mitochondrial metabolic modulation contributes to the longevity of daf-2 mutants and further highlights the crucial role of mitochondria in aging.

Developmental disruption of the mitochondrial fission gene drp-1 extends the longevity of daf-2 insulin/IGF-1 receptor mutant

The dynamic nature of the mitochondrial network is regulated by mitochondrial fission and fusion, allowing for re-organization of mitochondria to adapt to the cell's ever-changing needs. As organisms age, mitochondrial fission and fusion become dysregulated and mitochondrial networks become increasingly fragmented. Modulation of mitochondrial dynamics has been shown to affect longevity in fungi, yeast, Drosophila and C. elegans. Disruption of the mitochondrial fission gene drp-1 drastically increases the already long lifespan of daf-2 insulin/IGF-1 signaling (IIS) mutants. In this work, we determined the conditions required for drp-1 disruption to extend daf-2 longevity and explored the molecular mechanisms involved. We found that knockdown of drp-1 during development is sufficient to extend daf-2 lifespan, while tissue-specific knockdown of drp-1 in neurons, intestine or muscle failed to increase daf-2 longevity. Disruption of other genes involved in mitochondrial fission also increased daf-2 lifespan as did treatment with RNA interference clones that decrease mitochondrial fragmentation. In exploring potential mechanisms involved, we found that deletion of drp-1 increases resistance to chronic stresses. In addition, we found that disruption of drp-1 increased mitochondrial and peroxisomal connectedness in daf-2 worms, increased oxidative phosphorylation and ATP levels, and increased mitophagy in daf-2 worms, but did not affect their ROS levels, food consumption or mitochondrial membrane potential. Disruption of mitophagy through RNA interference targeting pink-1 decreased the lifespan of daf-2;drp-1 worms suggesting that increased mitophagy contributes to their extended lifespan. Overall, this work defined the conditions under which drp-1 disruption increases daf-2 lifespan and has identified multiple changes in daf-2;drp-1 mutants that may contribute to their lifespan extension.

Characterizing the Role of daf-16/C. elegans FOXO in Lifespan and Healthspan

In Caenorhabditis elegans (C. elegans), there is a single FOXO transcription factor homolog, encoded by the gene, daf-16. As a central regulator for multiple pathways, DAF-16 integrates these signals to result in changes in longevity, development, fat storage, stress resistance, innate immunity, and reproduction. One of the main advantages of using C. elegans is the ability to study FOXO in the context of the whole animal. Therefore, manipulating the levels or the activity of daf-16 results in visible, scorable phenotypic changes. DAF-16 is the downstream target of the conserved insulin/IGF-1 signaling (IIS) pathway, a PI 3-kinase signaling cascade that ultimately controls its nuclear localization. Since the IIS pathway is a major regulator of lifespan, almost all studies of lifespan modulation examine the requirement of daf-16. More recently, lifespan analysis has been accompanied by healthspan analysis, referring to the time an animal is healthy. In this chapter, I will focus on the assays to assess lifespan and healthspan of C. elegans FOXO/daf-16, in the context of a whole animal.

Catalytic activities of wild-type C. elegans DAF-2 kinase and dauer-associated mutants

DAF-2, the Caenorhabditis elegans insulin-like receptor homolog, regulates larval development, metabolism, stress response, and lifespan. The availability of numerous daf-2 mutant alleles has made it possible to elucidate the genetic mechanisms underlying these physiological processes. The DAF-2 pathway is significantly conserved with the human insulin/IGF-1 signaling pathway; it includes proteins homologous to human IRS, GRB-2, and PI3K, making it an important model to investigate human pathological conditions. We expressed and purified the kinase domain of wild-type DAF-2 to examine the catalytic activity and substrate specificity of the enzyme. Like the human insulin receptor kinase, DAF-2 kinase phosphorylates tyrosines within specific YxN or YxxM motifs, which are important for recruiting downstream effectors. DAF-2 kinase phosphorylated peptides derived from the YxxM and YxN motifs located in the C-terminal extension of the receptor tyrosine kinase, consistent with the idea that the DAF-2 receptor may possess independent signaling capacity. Unlike the human insulin or IGF-1 receptor kinases, DAF-2 kinase was poorly inhibited by the small-molecule inhibitor linsitinib. We also expressed and purified mutant kinases corresponding to daf-2 alleles that result in partial loss-of-function phenotypes in C. elegans. These mutations caused a complete loss of kinase function in vitro. Our biochemical investigations provide new insights into DAF-2 kinase function, and the approach should be useful for studying other mutations to shed light on DAF-2 signaling in C. elegans physiology.

Can the reduced GH, IGF-1, and ovarian steroids concentrations be considered as suspected biomarkers of age-associated functional deficit in mares?

In humans' and experimental animals' components of the somatotropic axis, such as growth hormone (GH) and insulin-like growth factor 1 (IGF-1) concentrations, decrease with advancing age. Although there is evidence regarding IGF-1, the effect of age on GH in mares, as well as the relationships between both parameters, have not yet been elucidated. On the other hand, although GH and IGF-1 are related to follicular development, it is unknown if they could be correlated with the circulating concentrations of ovarian steroids in mares, as occurs in other species. The hypothesis of this study was that both GH and IGF-1 could experience physiological changes with advancing age also in mares, and that both GH/IGF-1 could be correlated with oestradiol-17β (E2) and progesterone (P4), as recorded for other species. Hence, the objective of this study was to evaluate the concentrations of GH, IGF-1, E2, and P4 in mares, according to the different ages. Blood samples were drawn from 56 healthy cyclic Spanish Purebred mares belonging to four different age groups: 6-9 years, 10-13 years, 14-16 years and >16 years. Mares aged 6-9 years and 10-13 years showed higher GH concentrations (P < 0.05) than mares of 14-16 and >16 years; and mares aged 14-16 showed higher GH concentrations (P < 0.05) than >16 years (P < 0.05). Mares aged >16 years showed lower IGF-1 concentrations (P < 0.05) than mares of 6-9, 10-13 and 14-16 years (P < 0.05). The concentrations of E2 and P4 showed no significant differences among different age groups. Both GH and IGF-1 were not correlated with each other or with E2 and P4. The concentrations of E2 and P4 did not change with age. Advancing age leads to a decrease in the activity of the somatotropic axis in physiological cyclic mares, represented by a significant GH reduction, which, however, was ascribed for IGF-1 exclusively to mares over 16 years of age, without alterations in steroid hormone patterns.

Activated SKN-1 alters the aging trajectories of long-lived C. elegans mutants

In the presence of stressful environments, the SKN-1 cytoprotective transcription factor is activated to induce the expression of gene targets that can restore homeostasis. However, chronic activation of SKN-1 results in diminished health and a reduction of lifespan. Here we demonstrate the necessity of modulating SKN-1 activity to maintain the longevity-promoting effects associated with genetic mutations that impair daf-2/insulin receptor signaling, the eat-2 model of caloric restriction, and glp-1-dependent loss of germ cell proliferation. A hallmark of animals with constitutive SKN-1 activation is the age-dependent loss of somatic lipids and this phenotype is linked to a general reduction in survival in animals harboring the skn-1gf allele, but surprisingly, daf-2lf; skn-1gf double mutant animals do not redistribute somatic lipids which suggests the insulin signaling pathway functions downstream of SKN-1 in the maintenance of lipid distribution. As expected, the eat-2lf allele, which independently activates SKN-1, continues to display somatic lipid depletion in older ages with and without the skn-1gf activating mutation. In contrast, the presence of the skn-1gf allele does not lead to somatic lipid redistribution in glp-1lf animals that lack a proliferating germline. Taken together, these studies support a genetic model where SKN-1 activity is an important regulator of lipid mobilization in response to nutrient availability that fuels the developing germline by engaging the daf-2/insulin receptor pathway.

Patterning, regulation, and role of FoxO/DAF-16 in the early embryo

Insulin resistance and diabetes are associated with many health issues including higher rates of birth defects and miscarriage during pregnancy. Because insulin resistance and diabetes are both associated with obesity, which also affects fertility, the role of insulin signaling itself in embryo development is not well understood. A key downstream target of the insulin/insulin-like growth factor signaling (IIS) pathway is the forkhead family transcription factor FoxO (DAF-16 in C. elegans ). Here, we used quantitative live imaging to measure the patterning of endogenously tagged FoxO/DAF-16 in the early worm embryo. In 2-4-cell stage embryos, FoxO/DAF-16 initially localized uniformly to all cell nuclei, then became dramatically enriched in germ precursor cell nuclei beginning at the 8-cell stage. This nuclear enrichment in early germ precursor cells required germ fate specification, PI3K (AGE-1)- and PTEN (DAF-18)-mediated phospholipid regulation, and the deubiquitylase USP7 (MATH-33), yet was unexpectedly insulin receptor (DAF-2)- and AKT-independent. Functional analysis revealed that FoxO/DAF-16 acts as a cell cycle pacer for early cleavage divisions-without FoxO/DAF-16 cell cycles were shorter than in controls, especially in germ lineage cells. These results reveal the germ lineage specific patterning, upstream regulation, and cell cycle role for FoxO/DAF-16 during early C. elegans embryogenesis.

FOXO transcription factors as mediators of stress adaptation

The forkhead box protein O (FOXO, consisting of FOXO1, FOXO3, FOXO4 and FOXO6) transcription factors are the mammalian orthologues of Caenorhabditis elegans DAF-16, which gained notoriety for its capability to double lifespan in the absence of daf-2 (the gene encoding the worm insulin receptor homologue). Since then, research has provided many mechanistic details on FOXO regulation and FOXO activity. Furthermore, conditional knockout experiments have provided a wealth of data as to how FOXOs control development and homeostasis at the organ and organism levels. The lifespan-extending capabilities of DAF-16/FOXO are highly correlated with their ability to induce stress response pathways. Exogenous and endogenous stress, such as cellular redox stress, are considered the main drivers of the functional decline that characterizes ageing. Functional decline often manifests as disease, and decrease in FOXO activity indeed negatively impacts on major age-related diseases such as cancer and diabetes. In this context, the main function of FOXOs is considered to preserve cellular and organismal homeostasis, through regulation of stress response pathways. Paradoxically, the same FOXO-mediated responses can also aid the survival of dysfunctional cells once these eventually emerge. This general property to control stress responses may underlie the complex and less-evident roles of FOXOs in human lifespan as opposed to model organisms such as C. elegans.

[Molecular and cellular mechanisms of ageing: modern knowledge (literature review)]

Ageing (as known as eldering, senescence) is a genetically and epigenetically programmed pathophysiological process. Velocity of biological ageing is defined as balance between alteration and reparation of body structures. According to last World Health Organization (WHO) highlights ageing still stays an extremely actual scientific, social and demographic problem: in 2020 total number of people older than 60 years and older was 1 billion people; in 2030 future number may be 1,4 billion people, in 2050 - 2,1 billion people. Absence of single universal theory of aging nowadays is reason for scientifical and clinical collaboration between biologists and doctors, including endocrinologists. Designing of potentially effective newest anti-ageing strategies (such as natural/synthetic telomerase regulators, mesenchymal stem cells etc.) is of interest to scientific community. The aim of present article is a review of modern omics (genomic, proteomic, metabolomic) ageing mechanisms, potential ways of targeted prevention and treatment of age-related disease according to conception of personalized medicine. Present review is narrative, it does not lead to systematic review, meta-analysis and does not aim to commercial advertisement. Review has been provided via PubMed article that have been published since 1979 until 2022.

Environmental microbes promote phenotypic plasticity in reproduction and sleep behaviour

The microbiome has been hypothesized as a driving force of phenotypic variation in host organisms that is capable of extending metabolic processes, altering development and in some cases, conferring novel functions that are critical for survival. Only a few studies have directly shown a causal role for the environmental microbiome in altering host phenotypic features. To assess the extent to which environmental microbes induce variation in host life-history traits and behaviour, we inoculated axenic Drosophila melanogaster with microbes isolated from drosophilid populations collected from two different field sites and generated two populations with distinct bacterial and fungal profiles. We show that microbes isolated from environmental sites with modest abiotic differences induce large variation in host reproduction, fatty acid levels, stress tolerance and sleep behaviour. Importantly, clearing microbes from each experimental population removed the phenotypic differences. The results support the causal role of environmental microbes as drivers of host phenotypic plasticity and potentially, rapid adaptation and evolution.

Programmed ageing: decline of stem cell renewal, immunosenescence, and Alzheimer's disease

The characteristic maximum lifespan varies enormously across animal species from a few hours to hundreds of years. This argues that maximum lifespan, and the ageing process that itself dictates lifespan, are to a large extent genetically determined. Although controversial, this is supported by firm evidence that semelparous species display evolutionarily programmed ageing in response to reproductive and environmental cues. Parabiosis experiments reveal that ageing is orchestrated systemically through the circulation, accompanied by programmed changes in hormone levels across a lifetime. This implies that, like the circadian and circannual clocks, there is a master 'clock of age' (circavital clock) located in the limbic brain of mammals that modulates systemic changes in growth factor and hormone secretion over the lifespan, as well as systemic alterations in gene expression as revealed by genomic methylation analysis. Studies on accelerated ageing in mice, as well as human longevity genes, converge on evolutionarily conserved fibroblast growth factors (FGFs) and their receptors, including KLOTHO, as well as insulin-like growth factors (IGFs) and steroid hormones, as key players mediating the systemic effects of ageing. Age-related changes in these and multiple other factors are inferred to cause a progressive decline in tissue maintenance through failure of stem cell replenishment. This most severely affects the immune system, which requires constant renewal from bone marrow stem cells. Age-related immune decline increases risk of infection whereas lifespan can be extended in germfree animals. This and other evidence suggests that infection is the major cause of death in higher organisms. Immune decline is also associated with age-related diseases. Taking the example of Alzheimer's disease (AD), we assess the evidence that AD is caused by immunosenescence and infection. The signature protein of AD brain, Aβ, is now known to be an antimicrobial peptide, and Aβ deposits in AD brain may be a response to infection rather than a cause of disease. Because some cognitively normal elderly individuals show extensive neuropathology, we argue that the location of the pathology is crucial - specifically, lesions to limbic brain are likely to accentuate immunosenescence, and could thus underlie a vicious cycle of accelerated immune decline and microbial proliferation that culminates in AD. This general model may extend to other age-related diseases, and we propose a general paradigm of organismal senescence in which declining stem cell proliferation leads to programmed immunosenescence and mortality.

Increased alcohol dehydrogenase 1 activity promotes longevity

Several molecules can extend healthspan and lifespan across organisms. However, most are upstream signaling hubs or transcription factors orchestrating complex anti-aging programs. Therefore, these molecules point to but do not reveal the fundamental mechanisms driving longevity. Instead, downstream effectors that are necessary and sufficient to promote longevity across conditions or organisms may reveal the fundamental anti-aging drivers. Toward this goal, we searched for effectors acting downstream of the transcription factor EB (TFEB), known as HLH-30 in C. elegans, because TFEB/HLH-30 is necessary across anti-aging interventions and its overexpression is sufficient to extend C. elegans lifespan and reduce biomarkers of aging in mammals including humans. As a result, we present an alcohol-dehydrogenase-mediated anti-aging response (AMAR) that is essential for C. elegans longevity driven by HLH-30 overexpression, caloric restriction, mTOR inhibition, and insulin-signaling deficiency. The sole overexpression of ADH-1 is sufficient to activate AMAR, which extends healthspan and lifespan by reducing the levels of glycerol-an age-associated and aging-promoting alcohol. Adh1 overexpression is also sufficient to promote longevity in yeast, and adh-1 orthologs are induced in calorically restricted mice and humans, hinting at ADH-1 acting as an anti-aging effector across phyla.

Asparagus Fructans as Emerging Prebiotics

Commercial fructans (inulin and oligofructose) are generally obtained from crops such as chicory, Jerusalem artichoke or agave. However, there are agricultural by-products, namely asparagus roots, which could be considered potential sources of fructans. In this work, the fructans extracted from asparagus roots and three commercial ones from chicory and agave were studied in order to compare their composition, physicochemical characteristics, and potential health effects. Asparagus fructans had similar chemical composition to the others, especially in moisture, simple sugars and total fructan contents. However, its contents of ash, protein and phenolic compounds were higher. FTIR analysis confirmed these differences in composition. Orafti^®GR showed the highest degree of polymerization (DP) of up to 40, with asparagus fructans (up to 25) falling between Orafti^®GR and the others (DP 10-11). Although asparagus fructan powder had a lower fructan content and lower DP than Orafti^®GR, its viscosity was higher, probably due to the presence of proteins. The existence of phenolic compounds lent antioxidant activity to asparagus fructans. The prebiotic activity in vitro of the four samples was similar and, in preliminary assays, asparagus fructan extract presented health effects related to infertility and diabetes diseases. All these characteristics confer a great potential for asparagus fructans to be included in the prebiotics market.

One-day thermal regime extends the lifespan in Caenorhabditis elegans

Environmental factors, including temperature, can modulate an animal's lifespan. However, their underlying mechanisms remain largely undefined. We observed a profound effect of temperature on the aging of Caenorhabditis elegans (C. elegans) by performing proteomic analysis at different time points (young adult, middle age, and old age) and temperature conditions (20 °C and 25 °C). Importantly, although at the higher temperature, animals had short life spans, the shift from 20 °C to 25 °C for one day during early adulthood was beneficial for protein homeostasis since; it decreased protein synthesis and increased degradation. Consistent with our findings, animals who lived longer in the 25 °C shift were also more resistant to high temperatures along with oxidative and UV stresses. Furthermore, the lifespan extension by the 25 °C shift was mediated by three important transcription factors, namely FOXO/DAF-16, HSF-1, and HIF-1. We revealed an unexpected and complicated mechanism underlying the effects of temperature on aging, which could potentially aid in developing strategies to treat age-related diseases. Our data are available in ProteomeXchange with the identifier PXD024916.

Control of aging by the renin–angiotensin system: a review of C. elegans, Drosophila, and mammals

The free-living, non-parasitic nematode Caenorhabditis elegans is a premier model organism for the study of aging and longevity due to its short lifespan, powerful genetic tools, and conservation of fundamental mechanisms with mammals. Approximately 70 percent of human genes have homologs in C. elegans, including many that encode proteins in pathways that influence aging. Numerous genetic pathways have been identified in C. elegans that affect lifespan, including the dietary restriction pathway, the insulin/insulin-like growth factor (IGF) signaling pathway, and the disruption of components of the mitochondrial electron transport chain. C. elegans is also a powerful system for performing drug screens, and many lifespan-extending compounds have been reported; notably, several FDA-approved medications extend the lifespan in C. elegans, raising the possibility that they can also extend the lifespan in humans. The renin–angiotensin system (RAS) in mammals is an endocrine system that regulates blood pressure and a paracrine system that acts in a wide range of tissues to control physiological processes; it is a popular target for drugs that reduce blood pressure, including angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs). Emerging evidence indicates that this system influences aging. In C. elegans, decreasing the activity of the ACE homolog acn-1 or treatment with the ACE-inhibitor Captopril significantly extends the lifespan. In Drosophila, treatment with ACE inhibitors extends the lifespan. In rodents, manipulating the RAS with genetic or pharmacological interventions can extend the lifespan. In humans, polymorphisms in the ACE gene are associated with extreme longevity. These results suggest the RAS plays a conserved role in controlling longevity. Here, we review studies of the RAS and aging, emphasizing the potential of C. elegans as a model for understanding the mechanism of lifespan control.

Chromosome-level genome assembly of Monochamus saltuarius reveals its adaptation and interaction mechanism with pine wood nematode

Monochamus saltuarius (Coleoptera: Cerambycidae) was reported as the vector beetle of the pine wood nematode (PWN, Bursaphelenchus xylophilus) in Japan and Europe. It was first reported to transmitted the PWN to native Pinus species in 2018 in Liaoning Province, China. However, the lack of genomic resources has limited the in-depth understanding of its interspecific relationship with PWN. Here, we obtained a chromosome-level reference genome of M. saltuarius combining Illumina, Nanopore and Hi-C sequencing technologies. We assembled the scaffolds into ten chromosomes (including an X chromosome) and obtained a 682.23 Mb chromosome-level genome with a N50 of 73.69 Mb. In total, 427.67 Mb (62.69 %) repeat sequences were identified and 14, 492 protein-coding genes were predicted, of which 93.06 % were annotated. We described the mth/mthl, P450, OBP and OR gene families associated with the vector beetle's development and resistance, as well as the host selection and adaptation, which serve as a valuable resource for understanding the host adaptation in insects during evolution. This high quality reference genome of M. saltuarius also provide new avenues for researching the mechanism of this synergistic damage between vector beetles and PWN.

C. elegans as an Animal Model to Study the Intersection of DNA Repair, Aging and Neurodegeneration

Since its introduction as a genetic model organism, Caenorhabditis elegans has yielded insights into the causes of aging. In addition, it has provided a molecular understanding of mechanisms of neurodegeneration, one of the devastating effects of aging. However, C. elegans has been less popular as an animal model to investigate DNA repair and genomic instability, which is a major hallmark of aging and also a cause of many rare neurological disorders. This article provides an overview of DNA repair pathways in C. elegans and the impact of DNA repair on aging hallmarks, such as mitochondrial dysfunction, telomere maintenance, and autophagy. In addition, we discuss how the combination of biological characteristics, new technical tools, and the potential of following precise phenotypic assays through a natural life-course make C. elegans an ideal model organism to study how DNA repair impact neurodegeneration in models of common age-related neurodegenerative diseases.

The Intestine as a Lifespan- and Proteostasis-Promoting Signaling Tissue

In multicellular organisms such as Caenorhabditis elegans, cellular stress stimuli and responses are communicated between tissues to promote organismal health- and lifespan. The nervous system is the predominant regulator of cell nonautonomous proteostasis that orchestrates systemic stress responses to integrate both internal and external stimuli. This review highlights the role of the intestine in mediating cell nonautonomous stress responses and explores recent findings that suggest a central role for the intestine to regulate organismal proteostasis. As a tissue that receives and further transduces signals from the nervous system in response to dietary restriction, heat- and oxidative stress, and hypoxia, we explore evidence suggesting the intestine is a key regulatory organ itself. From the perspective of naturally occurring stressors such as dietary restriction and pathogen infection we highlight how the intestine can function as a key regulator of organismal proteostasis by integrating insulin/IGF-like signaling, miRNA-, neuropeptide- and metabolic signaling to alter distal tissue functions in promoting survival, health- and lifespan.

C. elegans as a model organism to study female reproductive health

Female reproductive health has been historically understudied and underfunded. Here, we present the advantages of using a free-living nematode, Caenorhabditis elegans, as an animal system to study fundamental aspects of female reproductive health. C. elegans is a powerful high-throughput model organism that shares key genetic and physiological similarities with humans. In this review, we highlight areas of pressing medical and biological importance in the 21st century within the context of female reproductive health. These include the decline in female reproductive capacity with increasing chronological age, reproductive dysfunction arising from toxic environmental insults, and cancers of the reproductive system. C. elegans has been instrumental in uncovering mechanistic insights underlying these processes, and has been valuable for developing and testing therapeutics to combat them. Adopting a convenient model organism such as C. elegans for studying reproductive health will encourage further research into this field, and broaden opportunities for making advancements into evolutionarily conserved mechanisms that control reproductive function.

New Directions in Research on Aging

Biology of aging is an active and rapidly expanding area of biomedical research. Over the years, focus of work in this field has been gradually shifting from studying the effects and symptoms of aging to searching for mechanisms of the aging process. Progress of this work led to an additional shift from looking for "the mechanism" of aging and formulating the corresponding "theories of aging" to appreciation that aging represents a net result of multiple physiological changes and their intricate interactions. It was also shown that mechanisms of aging include nutrient-dependent signaling pathways which have been remarkably conserved in the course of the evolution. Another important development in this field is increased emphasis on searching for pharmacological and environmental interventions that can extend healthspan or influence other aspects of aging. Progress in understanding the key role of aging as a risk factor for chronic disease provides impetus for these studies. Data from the recent pandemic provided additional evidence for the impact of age on resilience. Progress of work in this area also was influenced by major analytical and technological advances, including greatly improved methods for the study of gene expression, protein, lipids, and metabolites profiles, enhanced ability to produce various genetic modifications and novel approaches to assessment of biological age. Progress in research on the biology of aging provides reasons for optimism about the chances that safe and widely applicable anti-aging interventions with significant benefits for both individual and public health will be developed in the not too distant future.

An engineered, orthogonal auxin analog/AtTIR1(F79G) pairing improves both specificity and efficacy of the auxin degradation system in Caenorhabditis elegans

The auxin-inducible degradation system in C. elegans allows for spatial and temporal control of protein degradation via heterologous expression of a single Arabidopsis thaliana F-box protein, transport inhibitor response 1 (AtTIR1). In this system, exogenous auxin (Indole-3-acetic acid; IAA) enhances the ability of AtTIR1 to function as a substrate recognition component that adapts engineered degron-tagged proteins to the endogenous C. elegans E3 ubiquitin ligases complex [SKR-1/2-CUL-1-F-box (SCF)], targeting them for degradation by the proteosome. While this system has been employed to dissect the developmental functions of many C. elegans proteins, we have found that several auxin-inducible degron (AID)-tagged proteins are constitutively degraded by AtTIR1 in the absence of auxin, leading to undesired loss-of-function phenotypes. In this manuscript, we adapt an orthogonal auxin derivative/mutant AtTIR1 pair [C. elegans AID version 2 (C.e.AIDv2)] that transforms the specificity of allosteric regulation of TIR1 from IAA to one that is dependent on an auxin derivative harboring a bulky aryl group (5-Ph-IAA). We find that a mutant AtTIR1(F79G) allele that alters the ligand-binding interface of TIR1 dramatically reduces ligand-independent degradation of multiple AID*-tagged proteins. In addition to solving the ectopic degradation problem for some AID-targets, the addition of 5-Ph-IAA to culture media of animals expressing AtTIR1(F79G) leads to more penetrant loss-of-function phenotypes for AID*-tagged proteins than those elicited by the AtTIR1-IAA pairing at similar auxin analog concentrations. The improved specificity and efficacy afforded by the mutant AtTIR1(F79G) allele expand the utility of the AID system and broaden the number of proteins that can be effectively targeted with it.

Sperm-Guiding Unconventional Prostaglandins in C. elegans: Synthesis and Signaling

Prostaglandins comprise a family of lipid signaling molecules derived from polyunsaturated fatty acids and are involved in a wide array of biological processes, including fertilization. Prostaglandin-endoperoxide synthase (a.k.a. cyclooxygenase or Cox) initiates prostaglandin synthesis from 20-carbon polyunsaturated fatty acids, such as arachidonic acid. Oocytes of Caenorhabditis elegans (C. elegans) have been shown to secrete sperm-guidance cues prostaglandins, independent of Cox enzymes. Both prostaglandin synthesis and signal transduction in C. elegans are environmentally modulated pathways that regulate sperm guidance to the fertilization site. Environmental factors such as food triggers insulin and TGF-β secretion and their levels regulate tissue-specific prostaglandin synthesis in C. elegans. This novel PG pathway is abundant in mouse and human ovarian follicular fluid, where their functions, mechanism of synthesis and pathways remain to be established. Given the importance of prostaglandins in reproductive processes, a better understanding of how diets and other environmental factors influence their synthesis and function may lead to new strategies towards improving fertility in mammals.

Gene bookmarking by the heat shock transcription factor programs the insulin-like signaling pathway

Maternal stress can have long-lasting epigenetic effects on offspring. To examine how epigenetic changes are triggered by stress, we examined the effects of activating the universal stress-responsive heat shock transcription factor HSF-1 in the germline of Caenorhabditis elegans. We show that, when activated in germ cells, HSF-1 recruits MET-2, the putative histone 3 lysine 9 (H3K9) methyltransferase responsible for repressive H3K9me2 (H3K9 dimethyl) marks in chromatin, and negatively bookmarks the insulin receptor daf-2 and other HSF-1 target genes. Increased H3K9me2 at these genes persists in adult progeny and shifts their stress response strategy away from inducible chaperone expression as a mechanism to survive stress and instead rely on decreased insulin/insulin growth factor (IGF-1)-like signaling (IIS). Depending on the duration of maternal heat stress exposure, this epigenetic memory is inherited by the next generation. Thus, paradoxically, HSF-1 recruits the germline machinery normally responsible for erasing transcriptional memory but, instead, establishes a heritable epigenetic memory of prior stress exposure.

Context-specific regulation of lysosomal lipolysis through network-level diverting of transcription factor interactions

Plasticity in multicellular organisms involves signaling pathways converting contexts-either natural environmental challenges or laboratory perturbations-into context-specific changes in gene expression. Congruently, the interactions between the signaling molecules and transcription factors (TF) regulating these responses are also context specific. However, when a target gene responds across contexts, the upstream TF identified in one context is often inferred to regulate it across contexts. Reconciling these stable TF-target gene pair inferences with the context-specific nature of homeostatic responses is therefore needed. The induction of the Caenorhabditis elegans genes lipl-3 and lipl-4 is observed in many genetic contexts and is essential to survival during fasting. We find DAF-16/FOXO mediating lipl-4 induction in all contexts tested; hence, lipl-4 regulation seems context independent and compatible with across-context inferences. In contrast, DAF-16-mediated regulation of lipl-3 is context specific. DAF-16 reduces the induction of lipl-3 during fasting, yet it promotes it during oxidative stress. Through discrete dynamic modeling and genetic epistasis, we define that DAF-16 represses HLH-30/TFEB-the main TF activating lipl-3 during fasting. Contrastingly, DAF-16 activates the stress-responsive TF HSF-1 during oxidative stress, which promotes C. elegans survival through induction of lipl-3 Furthermore, the TF MXL-3 contributes to the dominance of HSF-1 at the expense of HLH-30 during oxidative stress but not during fasting. This study shows how context-specific diverting of functional interactions within a molecular network allows cells to specifically respond to a large number of contexts with a limited number of molecular players, a mode of transcriptional regulation we name "contextualized transcription."

BMP pathway regulation of insulin signaling components promotes lipid storage in Caenorhabditis elegans

A small number of peptide growth factor ligands are used repeatedly in development and homeostasis to drive programs of cell differentiation and function. Cells and tissues must integrate inputs from these diverse signals correctly, while failure to do so leads to pathology, reduced fitness, or death. Previous work using the nematode C. elegans identified an interaction between the bone morphogenetic protein (BMP) and insulin/IGF-1-like signaling (IIS) pathways in the regulation of lipid homeostasis. The molecular components required for this interaction, however, were not fully understood. Here we report that INS-4, one of 40 insulin-like peptides (ILPs), is regulated by BMP signaling to modulate fat accumulation. Furthermore, we find that the IIS transcription factor DAF-16/FoxO, but not SKN-1/Nrf, acts downstream of BMP signaling in lipid homeostasis. Interestingly, BMP activity alters sensitivity of these two transcription factors to IIS-promoted cytoplasmic retention in opposite ways. Finally, we probe the extent of BMP and IIS interactions by testing additional IIS functions including dauer formation, aging, and autophagy induction. Coupled with our previous work and that of other groups, we conclude that BMP and IIS pathways have at least three modes of interaction: independent, epistatic, and antagonistic. The molecular interactions we identify provide new insight into mechanisms of signaling crosstalk and potential therapeutic targets for IIS-related pathologies such as diabetes and metabolic syndrome.

Evaluation of the Effect of rs13217795 Genotype and Minor Allele (C) on Clinical Chemistry and Genetic Risk of Diabetes Among the Elderly Individuals from Northern India

The forkhead box O family (FOXO) is expressed ubiquitously in a spatio-temporal manner and plays a key role in cellular metabolism, senescence, and aging. Genetic mutations in FOXO lead to metabolic diseases and cancer,and affect the longevity of individuals. Our study investigated how the genetic risk of type 2 diabetes mellitus (T2DM) altered due to an intronic variant rs13217795 of the longevity-associated <i>FOXO3</i> gene in the geriatric population of North India. Genotypic characteristics of rs13217795 were determined among 347 age sex-matched (177 diabetic cases, 170 healthy controls) elderly individuals by TaqMan SNP assays after clinical assessment. Clinical chemistry and circulating cytokines level were assessed by biochemical and immunoassays. Genotype frequencies were not significantly (<i>p</i> = 0.526) different between cases and controls. The minor allele (C) frequency in diabetic cases and controls was 0.47 and 0.49, respectively (OR = 0.94, 95% CI = 0.69–1.26, <i>p</i> &#x3e; 0.05). The minor allele was associated with lower fasting plasma glucose (FPG), fasting insulin, HOMA-IR, CRP, TNF-α, and IL-6 (<i>p</i> &#x3c; 0.05). The homozygous minor allele carriers showed significantly lower levels of FPG, HOMA-IR, and TNF-α in T2DM patients. The minor allele (C) of intronic polymorphism in <i>FOXO3</i> (rs13217795: T/C) confers the protective role characterized by its association with a decrease in glycemic and insulin resistance and proinflammatory markers.

Genes in human obesity loci are causal obesity genes in C. elegans

Obesity and its associated metabolic syndrome are a leading cause of morbidity and mortality. Given the disease's heavy burden on patients and the healthcare system, there has been increased interest in identifying pharmacological targets for the treatment and prevention of obesity. Towards this end, genome-wide association studies (GWAS) have identified hundreds of human genetic variants associated with obesity. The next challenge is to experimentally define which of these variants are causally linked to obesity, and could therefore become targets for the treatment or prevention of obesity. Here we employ high-throughput in vivo RNAi screening to test for causality 293 C. elegans orthologs of human obesity-candidate genes reported in GWAS. We RNAi screened these 293 genes in C. elegans subject to two different feeding regimens: (1) regular diet, and (2) high-fructose diet, which we developed and present here as an invertebrate model of diet-induced obesity (DIO). We report 14 genes that promote obesity and 3 genes that prevent DIO when silenced in C. elegans. Further, we show that knock-down of the 3 DIO genes not only prevents excessive fat accumulation in primary and ectopic fat depots but also improves the health and extends the lifespan of C. elegans overconsuming fructose. Importantly, the direction of the association between expression variants in these loci and obesity in mice and humans matches the phenotypic outcome of the loss-of-function of the C. elegans ortholog genes, supporting the notion that some of these genes would be causally linked to obesity across phylogeny. Therefore, in addition to defining causality for several genes so far merely correlated with obesity, this study demonstrates the value of model systems compatible with in vivo high-throughput genetic screening to causally link GWAS gene candidates to human diseases.

Epigenetic age prediction

Advanced age is the main common risk factor for cancer, cardiovascular disease and neurodegeneration. Yet, more is known about the molecular basis of any of these groups of diseases than the changes that accompany ageing itself. Progress in molecular ageing research was slow because the tools predicting whether someone aged slowly or fast (biological age) were unreliable. To understand ageing as a risk factor for disease and to develop interventions, the molecular ageing field needed a quantitative measure; a clock for biological age. Over the past decade, a number of age predictors utilising DNA methylation have been developed, referred to as epigenetic clocks. While they appear to estimate biological age, it remains unclear whether the methylation changes used to train the clocks are a reflection of other underlying cellular or molecular processes, or whether methylation itself is involved in the ageing process. The precise aspects of ageing that the epigenetic clocks capture remain hidden and seem to vary between predictors. Nonetheless, the use of epigenetic clocks has opened the door towards studying biological ageing quantitatively, and new clocks and applications, such as forensics, appear frequently. In this review, we will discuss the range of epigenetic clocks available, their strengths and weaknesses, and their applicability to various scientific queries.

MHY2013 Modulates Age-related Inflammation and Insulin Resistance by Suppressing the Akt/FOXO1/IL-1β Axis and MAPK-mediated NF-κB Signaling in Aged Rat Liver

Chronic inflammation is a major risk factor underlying aging and age-associated diseases. It impairs normal lipid accumulation, adipose tissue function, and mitochondrial function, which eventually lead to insulin resistance. Peroxisome proliferator-activated receptors (PPARs) critically regulate gluconeogenesis, lipid metabolism, and the lipid absorption and breakdown process, and PPAR activity decreases in the liver during aging. In the present study, we investigated the ability of 2-(4-(5,6-methylenedioxybenzo[d]thiazol-2-yl)-2-methylphenoxy)-2-methylpropanoic acid (MHY2013), synthesized PPARα/PPARβ/PPARγ pan agonist, to suppress the inflammatory response and attenuate insulin resistance in aged rat liver. Six- and 20-month-old rats were divided into 4 groups: young and old rats fed ad libitum; and old rats fed ad libitum supplemented with MHY2013 (1 mg and 5 mg/kg/d for 4 wk). We found that MHY2013 supplementation efficiently downregulated the activity of nuclear factor-κB through JNK/ERK/p38 mitogen-activated protein kinase signaling in the liver of aged rats. In addition, MHY2013 treatment increased hepatic insulin signaling, and the downstream signaling activity of FOXO1, which is negatively regulated by Akt. Downregulation of Akt increases expression of FOXO1, which acts as a transcription factor and increases transcription of interleukin-1β, leading to hepatic inflammation. The major finding of this study is that MHY2013 acts as a therapeutic agent against age-related inflammation associated with insulin resistance by activating PPARα, PPARβ, and PPARγ. Thus, the study provides evidence for the anti-inflammatory properties of MHY2013, and the role it plays in the regulation of age-related alterations in signal transduction pathways.

Population Density Modulates the Duration of Reproduction of C. elegans

Population density can modulate the developmental trajectory of Caenorhabditis elegans larvae by promoting entry into dauer diapause, which is characterized by metabolic and anatomical remodeling and stress resistance [1, 2]. Genetic analysis of dauer formation has identified the involvement of evolutionarily conserved endocrine signaling pathways, including the DAF-2/insulin-like receptor signaling pathway [3-7]. Chemical and metabolomic analysis of dauer-inducing pheromone has identified a family of small molecules, ascarosides, which act potently to communicate increased population density and promote dauer formation [1, 8-10]. Here, we show that adult animals respond to ascarosides produced under conditions of increased population density by increasing the duration of reproduction. We observe that the ascarosides that promote dauer entry of larvae also act on adult animals to attenuate expression of the insulin peptide INS-6 from the ASI chemosensory neurons, resulting in diminished neuroendocrine insulin signaling that extends the duration of reproduction. Genetic analysis of ins-6 and corresponding insulin-signaling pathway mutants showed that the effect of increased population density on reproductive span was mimicked by ins-6 loss of function that exerted effects on duration of reproduction through the canonical DAF-2-DAF-16 pathway. We further observed that the effect of population density on reproductive span acted through DAF-16-dependent and DAF-16-independent pathways upstream of DAF-12, paralleling in adults what has been observed for the dauer developmental decision of larvae. Our data suggest that, under conditions of increased population density, C. elegans animals prolong the duration of reproductive egg laying, which may enable the subsequent development of progeny under more favorable conditions.

Genetic Basis of Increased Lifespan and Postponed Senescence in Drosophila melanogaster

Limited lifespan and senescence are near-universal phenomena. These quantitative traits exhibit variation in natural populations due to the segregation of many interacting loci and from environmental effects. Due to the complexity of the genetic control of lifespan and senescence, our understanding of the genetic basis of variation in these traits is incomplete. Here, we analyzed the pattern of genetic divergence between long-lived (O) Drosophila melanogaster lines selected for postponed reproductive senescence and unselected control (B) lines. We quantified the productivity of the O and B lines and found that reproductive senescence is maternally controlled. We therefore chose 57 candidate genes that are expressed in ovaries, 49 of which have human orthologs, and assessed the effects of RNA interference in ovaries and accessary glands on lifespan and reproduction. All but one candidate gene affected at least one life history trait in one sex or productivity week. In addition, 23 genes had antagonistic pleiotropic effects on lifespan and productivity. Identifying evolutionarily conserved genes affecting increased lifespan and delayed reproductive senescence is the first step toward understanding the evolutionary forces that maintain segregating variation at these loci in nature and may provide potential targets for therapeutic intervention to delay senescence while increasing lifespan.

A Conserved Mito-Cytosolic Translational Balance Links Two Longevity Pathways

Slowing down translation in either the cytosol or the mitochondria is a conserved longevity mechanism. Here, we found a non-interventional natural correlation of mitochondrial and cytosolic ribosomal proteins (RPs) in mouse population genetics, suggesting a translational balance. Inhibiting mitochondrial translation in C. elegans through mrps-5 RNAi repressed cytosolic translation. Transcriptomics integrated with proteomics revealed that this inhibition specifically reduced translational efficiency of mRNAs required in growth pathways while increasing stress response mRNAs. The repression of cytosolic translation and extension of lifespan from mrps-5 RNAi were dependent on atf-5/ATF4 and independent from metabolic phenotypes. We found the translational balance to be conserved in mammalian cells upon inhibiting mitochondrial translation pharmacologically with doxycycline. Lastly, extending this in vivo, doxycycline repressed cytosolic translation in the livers of germ-free mice. These data demonstrate that inhibiting mitochondrial translation initiates an atf-5/ATF4-dependent cascade leading to coordinated repression of cytosolic translation, which could be targeted to promote longevity.

The Mechanism of Programmed Aging: The Way to Create a Real Remedy for Senescence

BACKGROUND

Accumulation of various damages is considered the primary cause of aging throughout the history of gerontology. No progress has been made in extending animal lifespan under the guidance of this concept. This concept denies the existence of longevity genes, but it has been experimentally shown that manipulating genes that affect cell division rates can increase the maximum lifespan of animals. These methods of prolonging life are unsuitable for humans because of dangerous side effects, but they undoubtedly indicate the programmed nature of aging.

OBJECTIVE

The objective was to understand the mechanism of programmed aging to determine how to solve the problem of longevity.

METHODS

Fundamental research has already explored key details relating to the mechanism of programmed aging, but they are scattered across different fields of knowledge. The way was to recognize and combine them into a uniform mechanism.

RESULTS

Only a decrease in bioenergetics is under direct genetic control. This causes many different harmful processes that serve as the execution mechanism of the aging program. The aging rate and, therefore, lifespan are determined by the rate of cell proliferation and the magnitude of the decrease in bioenergetics per cell division in critical tissues.

CONCLUSION

The mechanism of programmed aging points the way to achieving an unlimited healthy life; it is necessary to develop a means for managing bioenergetics. It has already been substantially studied by molecular biologists and is now waiting for researchers from gerontology.

Release of insulin produced by the choroid plexis is regulated by serotonergic signaling

The choroid plexus (ChP) is a highly vascularized tissue found in the brain ventricles, with an apical epithelial cell layer surrounding fenestrated capillaries. It is responsible for the production of most of the cerebrospinal fluid (CSF) in the ventricular system, subarachnoid space, and central canal of the spinal cord, while also constituting the blood-CSF barrier (BCSFB). In addition, epithelial cells of the ChP (EChP) synthesize neurotrophic factors and other signaling molecules that are released into the CSF. Here, we show that insulin is produced in EChP of mice and humans, and its expression and release are regulated by serotonin. Insulin mRNA and immune-reactive protein, including C-peptide, are present in EChP, as detected by several experimental approaches, and appear in much higher levels than any other brain region. Moreover, insulin is produced in primary cultured mouse EChP, and its release, albeit Ca2+ sensitive, is not regulated by glucose. Instead, activation of the 5HT2C receptor by serotonin treatment led to activation of IP3-sensitive channels and Ca2+ mobilization from intracellular storage, leading to insulin secretion. In vivo depletion of brain serotonin in the dorsal raphe nucleus negatively affected insulin expression in the ChP, suggesting an endogenous modulation of ChP insulin by serotonin. Here, we show for the first time to our knowledge that insulin is produced by EChP in the brain, and its release is modulated at least by serotonin but not glucose.

Pleiotropic Effects of mTOR and Autophagy During Development and Aging

Autophagy as a ubiquitous catabolic process causes degradation of cytoplasmic components and is generally considered to have beneficial effects on health and lifespan. In contrast, inefficient autophagy has been linked with detrimental effects on the organism and various diseases, such as Parkinson's disease. Previous research, however, showed that this paradigm is far from being black and white. For instance, it has been reported that increased levels of autophagy during development can be harmful, but become advantageous in the aging cell or organism, causing enhanced healthspan and even longevity. The antagonistic pleiotropy hypothesis postulates that genes, which control various traits in an organism, can be fitness-promoting in early life, but subsequently trigger aging processes later. Autophagy is controlled by the mechanistic target of rapamycin (mTOR), a key player of nutrient sensing and signaling and classic example of a pleiotropic gene. mTOR acts upstream of transcription factors such as FOXO, NRF, and TFEB, controlling protein synthesis, degradation, and cellular growth, thereby regulating fertility as well as aging. Here, we review recent findings about the pleiotropic role of autophagy during development and aging, examine the upstream factors, and contemplate specific mechanisms leading to disease, especially neurodegeneration.

IGF signalling in germ cells and testicular germ cell tumours: roles and therapeutic approaches

The insulin-like growth factor (IGF) axis plays key roles in normal tissue growth and development as well as in the progression of several tumour types and their subsequent growth and progression to a metastatic phenotype. This review explores the role of IGF system in normal germ cell development and function in addition to examining the evidence for deregulation of IGF signalling in cancer, with particular relevance to evidence supporting a role in testicular germ cell tumours (TGCTs). Despite the clear preclinical rationale for targeting the IGF axis in cancer, there has been a lack of progress in identifying which patients may benefit from such therapy. Future employment of agents targeting the IGF pathway is expected to concentrate on their use in combination with other treatments to prevent resistance and exploit their potential as chemo- and radiosensitizers.

Using Bacterial Transcriptomics to Investigate Targets of Host-Bacterial Interactions in Caenorhabditis elegans

The interactions between a host and its resident microbes form complicated networks that can affect host physiology. Disentangling these host-microbe interactions can help us better understand mechanisms by which bacteria affect hosts, while also defining the integral commensal protection that host-associated microbiota offer to promote health. Here we utilize a tractable genetic model organism, Caenorhabditis elegans, to study the effects of host environments on bacterial gene expression and metabolic pathways. First, we compared the transcriptomic profiles of E. coli OP50 in vitro (on agar plates) versus in vivo (fed to C. elegans host). Our data revealed that 110 biosynthetic genes were enriched in host-associated E. coli. Several of these expressed genes code for the precursors and products needed for the synthesis of lipopolysaccharides (LPS), which are important for innate immune and stress responses, as well as pathogenicity. Secondly, we compared the transcriptomic profiles of E. coli fed to hosts with different genetic backgrounds, including the long-lived daf-2/insulin like growth factor (IGF) receptor and short lived daf-16/FOXO transcription factor mutants. We find that hosts genetics also alters bacterial metabolic pathways. Given that bacteria influence host health, this transcriptomics approach can elucidate genes mediating host aging.

Effect of starvation and high-carbohydrate diet on learning ability of Caenorhabditis elegans

Starvation and high-carbohydrate diet have a big impact on our health, while their effects on the learning ability are not so clear. Here, we used C. elegans as the model organism to investigate it. We starved the worms for 24 h or fed them with glucose since hatching, and then measured their learning ability at L4 stage using mechanosensory stimulation assay. The results showed that the learning ability was significantly decreased by starvation, while could be gradually recovered after 3 h normal feeding. After glucose treatment, the length-width ratio of worm was reduced and the learning ability was also significantly decreased. Interestingly, this effect could be passed down two generations probably through epigenetic inheritance. To understand the mechanism of these effects, age-1 and mec-3 mutants were used and they affected the learning ability differently under normal or adverse conditions. Therefore, we concluded that starvation and high-carbohydrate diet could modulate the learning ability of C. elegans, and they were regulated by different gene networks.

Uptake of nanopolystyrene particles induces distinct metabolic profiles and toxic effects in Caenorhabditis elegans

Nanoplastics are widely used in modern life, for example, in cosmetics and daily use products, and are attracting concern due to their potential toxic effects on environments. In this study, the uptake of nanopolystyrene particles by Caenorhabditis elegans (C. elegans) and their toxic effects were evaluated. Nanopolystyrene particles with sizes of 50 and 200 nm were prepared, and the L4 stage of C. elegans was exposed to these particles for 24 h. Their uptake was monitored by confocal microscopy, and various phenotypic alterations of the exposed nematode such as locomotion, reproduction and oxidative stress were measured. In addition, a metabolomics study was performed to determine the significantly affected metabolites in the exposed C. elegans group. Exposure to nanopolystyrene particles caused the perturbation of metabolites related to energy metabolism, such as TCA cycle intermediates, glucose and lactic acid. Nanopolystyrene also resulted in toxic effect including induction of oxidative stress and reduction of locomotion and reproduction. Collectively, these findings provide new insights into the toxic effects of nanopolystyrene particles.

The Mouse Microbiome Is Required for Sex-Specific Diurnal Rhythms of Gene Expression and Metabolism

The circadian clock and associated feeding rhythms have a profound impact on metabolism and the gut microbiome. To what extent microbiota reciprocally affect daily rhythms of physiology in the host remains elusive. Here, we analyzed transcriptome and metabolome profiles of male and female germ-free mice. While mRNA expression of circadian clock genes revealed subtle changes in liver, intestine, and white adipose tissue, germ-free mice showed considerably altered expression of genes associated with rhythmic physiology. Strikingly, the absence of the microbiome attenuated liver sexual dimorphism and sex-specific rhythmicity. The resulting feminization of male and masculinization of female germ-free animals is likely caused by altered sexual development and growth hormone secretion, associated with differential activation of xenobiotic receptors. This defines a novel mechanism by which the microbiome regulates host metabolism.

Matricidal hatching can induce multi-generational effects in nematode Caenorhabditis elegans after dietary exposure to nanoparticles

In this study, we investigated multi-generational effects and generation particle transfer in Caenorhabditis elegans following maternal food exposure to core-shell quantum dots. We found that that the Bag of Worms (BOW) phenotype in aged worms induces changes in quantum dot distribution in the parental body, which is related to the inter-generation transfer of these nanoparticles and to their effects in the offspring. To confirm these results we examined a variety of endpoints, namely, survival, reproduction, aging phenotype, oxidative stress, and intestinal fat metabolism. We show that worms born to parents at different times after exposure show different phenotypic effects as a consequence of quantum dot transfer. This evidence of trans-generational transfer and the effects of nanoparticles highlights the complex multi-generational effects and potential safety hazards that can occur under real environmental conditions.

Impact of Growth Hormone-Related Mutations on Mammalian Aging

Mutations of a single gene can lead to a major increase in longevity in organisms ranging from yeast and worms to insects and mammals. Discovering these mutations (sometimes referred to as “longevity genes”) led to identification of evolutionarily conserved molecular, cellular, and organismal mechanisms of aging. Studies in mice provided evidence for the important role of growth hormone (GH) signaling in mammalian aging. Mice with mutations or gene deletions leading to GH deficiency or GH resistance have reduced body size and delayed maturation, but are healthier and more resistant to stress, age slower, and live longer than their normal (wild type) siblings. Mutations of the same genes in people can provide remarkable protection from age-related disease, but have no consistent impact on lifespan. Ongoing research indicates that genetic defects in GH signaling are linked to extension of healthspan and lifespan via a variety of interlocking mechanism, including improvements in genome and stem cell maintenance, stress resistance, glucose homeostasis, and thermogenesis, along with reductions in the mechanistic target of rapamycin (mTOR) C1 complex signaling and in chronic low grade inflammation.

Prolonged exposure of di(2-ethylhexyl) phthalate induces multigenerational toxic effects in Caenorhabditis elegans

The plasticizer di(2-ethylhexyl) phthalate (DEHP) is an emerging organic contaminant that has represented a risk for organisms present in the environment. However, there is still limited information regarding DEHP-induced multigenerational toxicity and the underlying mechanisms. In this study we investigated the multigenerational toxic effects including locomotive behaviors and reproduction upon prolonged DEHP exposure (from larval L1 to adult) and the underlying mechanisms in the nematode Caenorhabditis elegans. The multigenerational effects were examined over 6 generations (F0-F5) with only parental C. elegans (F0) was exposed to DEHP from larval L1 to adults (72h), and the subsequent offsprings (F1-F5) were grown under DEHP-free conditions. The results showed that prolonged exposure (72h) to various concentrations of DEHP caused dose-dependent locomotive impairments and reproduction defects in C. elegans and that a concentration of 0.2mg/L DEHP was enough to cause such sublethal effects. The results showed that after prolonged exposure to DEHP in the F0 generation, abnormal locomotive behaviors such as reduced body bends and head thrashes were observed from generations F0 to F5. Additionally, prolonged exposure to DEHP (20mg/L) in F0 significantly reduced total brood size in F0, and this parental exposure was sufficient to cause multigenerational reproductive toxicity in the offspring generations (F1-F5) as well. Furthermore, the expressions of reproduction-related genes such as vit-2 and vit-6 were down-regulated by about 20% until F3, and the expression of H3Kme2 demethylase, spr-5, was downregulated in F1 by about 40%. Results from this study demonstrate that prolonged exposure to DEHP only at F0 adversely affected reproduction and locomotive behaviors in C. elegans across generations and might be associated with inadequate vitellogenin production and malfunction of H3Kme2 demethylase. This study implies that parentally prolonged exposure to DEHP caused multigenerational defects in both reproduction and locomotive behaviors raising the potential health and ecological risk.

Mitochondrial ubiquinone-mediated longevity is marked by reduced cytoplasmic mRNA translation

This study uses polysomal RNA sequencing to show that the translational efficiency of specific mRNA changes in long-lived Caenorhabditis elegans with reduced ubiquinone synthesis.

Mutations in the clk-1 gene impair mitochondrial ubiquinone biosynthesis and extend the lifespan in Caenorhabditis elegans. We demonstrate here that this life extension is linked to the repression of cytoplasmic mRNA translation, independent of the alleged nuclear form of CLK-1. Clk-1 mutations inhibit polyribosome formation similarly to daf-2 mutations that dampen insulin signaling. Comparisons of total versus polysomal RNAs in clk-1(qm30) mutants reveal a reduction in the translational efficiencies of mRNAs coding for elements of the translation machinery and an increase in those coding for the oxidative phosphorylation and autophagy pathways. Knocking down the transcription initiation factor TATA-binding protein-associated factor 4, a protein that becomes sequestered in the cytoplasm during early embryogenesis to induce transcriptional silencing, ameliorates the clk-1 inhibition of polyribosome formation. These results underscore a prominent role for the repression of cytoplasmic protein synthesis in eukaryotic lifespan extension and suggest that mutations impairing mitochondrial function are able to exploit this repression similarly to reductions of insulin signaling. Moreover, this report reveals an unexpected role for TATA-binding protein-associated factor 4 as a repressor of polyribosome formation when ubiquinone biosynthesis is compromised.

Clonal raider ant brain transcriptomics identifies candidate molecular mechanisms for reproductive division of labor

BACKGROUND

Division of labor between reproductive queens and workers that perform brood care is a hallmark of insect societies. However, studies of the molecular basis of this fundamental dichotomy are limited by the fact that the caste of an individual cannot typically be experimentally manipulated at the adult stage. Here we take advantage of the unique biology of the clonal raider ant, Ooceraea biroi, to study brain gene expression dynamics during experimentally induced transitions between reproductive and brood care behavior.

RESULTS

Introducing larvae that inhibit reproduction and induce brood care behavior causes much faster changes in adult gene expression than removing larvae. In addition, the general patterns of gene expression differ depending on whether ants transition from reproduction to brood care or vice versa, indicating that gene expression changes between phases are cyclic rather than pendular. Finally, we identify genes that could play upstream roles in regulating reproduction and behavior because they show large and early expression changes in one or both transitions.

CONCLUSIONS

Our analyses reveal that the nature and timing of gene expression changes differ substantially depending on the direction of the transition, and identify a suite of promising candidate molecular regulators of reproductive division of labor that can now be characterized further in both social and solitary animal models. This study contributes to understanding the molecular regulation of reproduction and behavior, as well as the organization and evolution of insect societies.