Acute Dietary Restriction Acts via TOR, PP2A, and Myc Signaling to Boost Innate Immunity in Drosophila

Interactions between innate immunity and insulin signaling affect resistance to infection in insects

An active immune response is energetically demanding and requires reallocation of nutrients to support resistance to and tolerance of infection. Insulin signaling is a critical global regulator of metabolism and whole-body homeostasis in response to nutrient availability and energetic needs, including those required for mobilization of energy in support of the immune system. In this review, we share findings that demonstrate interactions between innate immune activity and insulin signaling primarily in the insect model Drosophila melanogaster as well as other insects like Bombyx mori and Anopheles mosquitos. These studies indicate that insulin signaling and innate immune activation have reciprocal effects on each other, but that those effects vary depending on the type of pathogen, route of infection, and nutritional status of the host. Future research will be required to further understand the detailed mechanisms by which innate immunity and insulin signaling activity impact each other.

Longevity through diet restriction and immunity

The share of the population that is aging is growing rapidly. In an aging society, technologies and interventions that delay the aging process are of great interest. Dietary restriction (DR) is the most reproducible and effective nutritional intervention tested to date for delaying the aging process and prolonging the health span in animal models. Preventive effects of DR on age-related diseases have also been reported in human. In addition, highly conserved signaling pathways from small animal models to human mediate the effects of DR. Recent evidence has shown that the immune system is closely related to the effects of DR, and functions as a major mechanism of DR in healthy aging. This review discusses the effects of DR in delaying aging and preventing age-related diseases in animal, including human, and introduces the molecular mechanisms that mediate these effects. In addition, it reports scientific findings on the relationship between the immune system and DRinduced longevity. The review highlights the role of immunity as a potential mediator of the effects of DR on longevity, and provides insights into healthy aging in human. [BMB Reports 2023; 56(10): 537-544].

Regulating metabolism to shape immune function: Lessons from Drosophila

Infection with pathogenic microbes is a severe threat that hosts manage by activating the innate immune response. In Drosophila melanogaster, the Toll and Imd signaling pathways are activated by pathogen-associated molecular patterns to initiate cellular and humoral immune processes that neutralize and kill invaders. The Toll and Imd signaling pathways operate in organs such as fat body and gut that control host nutrient metabolism, and infections or genetic activation of Toll and Imd signaling also induce wide-ranging changes in host lipid, carbohydrate and protein metabolism. Metabolic regulation by immune signaling can confer resistance to or tolerance of infection, but it can also lead to pathology and susceptibility to infection. These immunometabolic phenotypes are described in this review, as are changes in endocrine signaling and gene regulation that mediate survival during infection. Future work in the field is anticipated to determine key variables such as sex, dietary nutrients, life stage, and pathogen characteristics that modify immunometabolic phenotypes and, importantly, to uncover the mechanisms used by the immune system to regulate metabolism.

The innate immune signaling component FBXC-58 mediates dietary restriction effects on healthy aging in Caenorhabditis elegans

Dietary restriction (DR) is a highly effective and reproducible intervention that prolongs longevity in many organisms. The molecular mechanism of action of DR is tightly connected with the immune system; however, the detailed mechanisms and effective downstream factors of immunity that mediate the beneficial effects of DR on aging remain unknown. Here, to investigate the immune signaling that mediates DR effects, we used Caenorhabditis elegans, which has been widely used in research, to understand the underlying molecular mechanisms of aging and immunity. We found that the F-box gene, fbxc-58, a regulator of the innate immune response, is a novel mediator of DR effects on extending the health span of C. elegans. fbxc-58 is upregulated by DR and is necessary for DR-induced lifespan extension and physical health improvement in C. elegans. Furthermore, through DR, fbxc-58 prevents disintegration of the mitochondrial network in body wall muscle during aging. We found that fbxc-58 is a downstream target of the ZIP-2 and PHA-4 transcription factors, the well-known DR mediator, and fbxc-58 extends longevity in DR through an S6 kinase-dependent pathway. We propose that the novel DR effector, fbxc-58, could provide a new mechanistic understanding of the effects of DR on healthy aging and elucidate the signaling mechanisms that link immunity and DR effects with aging.

Constitutively-expressed and induced immune effectors in the house fly (Musca domestica) and the transcription factors that may regulate them

Insects possess both infection-induced and constitutively expressed innate immune defences. Some effectors, such as lysozymes and antimicrobial peptides (AMPs), are constitutively expressed in flies, but expression patterns vary across tissues and species. The house fly (Musca domestica L.) has an impressive immune repertoire, with more effector genes than any other flies. We used RNA-seq to explore both constitutive and induced expression of immune effectors in flies. House flies were fed either Pseudomonas aeruginosa or Escherichia coli, or sterile control broth, and gene expression in the gut and carcass was analysed 4 h post-feeding. Flies fed either bacterium did not induce AMP expression, but some lysozyme and AMP genes were constitutively expressed. Prior transcriptome data from flies injected with bacteria also were analysed, and these constitutively expressed genes differed from those induced by bacterial injection. Binding sites for the transcription factor Myc were enriched upstream of constitutively expressed AMP genes, while upstream regions of induced AMPs were enriched for NF-κB binding sites resembling those of the Imd-responsive transcription factor Relish. Therefore, we identified at least two expression repertoires for AMPs in the house fly: constitutively expressed genes that may be regulated by Myc, and induced AMPs likely regulated by Relish.

SlMYC2 interacted with the SlTOR promoter and mediated JA signaling to regulate growth and fruit quality in tomato

Tomato (Solanum lycopersicum) is a major vegetable crop cultivated worldwide. The regulation of tomato growth and fruit quality has long been a popular research topic. MYC2 is a key regulator of the interaction between jasmonic acid (JA) signaling and other signaling pathways, and MYC2 can integrate the interaction between JA signaling and other hormone signals to regulate plant growth and development. TOR signaling is also an essential regulator of plant growth and development. However, it is unclear whether MYC2 can integrate JA signaling and TOR signaling during growth and development in tomato. Here, MeJA treatment and SlMYC2 overexpression inhibited the growth and development of tomato seedlings and photosynthesis, but increased the sugar-acid ratio and the contents of lycopene, carotenoid, soluble sugar, total phenol and flavonoids, indicating that JA signaling inhibited the growth of tomato seedlings and altered fruit quality. When TOR signaling was inhibited by RAP, the JA content increased, and the growth and photosynthesis of tomato seedlings decreased, indicating that TOR signaling positively regulated the growth and development of tomato seedlings. Further yeast one-hybrid assays showed that SlMYC2 could bind directly to the SlTOR promoter. Based on GUS staining analysis, SlMYC2 regulated the transcription of SlTOR, indicating that SlMYC2 mediated the interaction between JA and TOR signaling by acting on the promoter of SlTOR. This study provides a new strategy and some theoretical basis for tomato breeding.

Dietary restriction ameliorates TBI-induced phenotypes in Drosophila melanogaster

Traumatic brain injury (TBI) affects millions annually and is associated with long-term health decline. TBI also shares molecular and cellular hallmarks with neurodegenerative diseases (NDs), typically increasing in prevalence with age, and is a major risk factor for developing neurodegeneration later in life. While our understanding of genes and pathways that underlie neurotoxicity in specific NDs has advanced, we still lack a complete understanding of early molecular and physiological changes that drive neurodegeneration, particularly as an individual ages following a TBI. Recently Drosophila has been introduced as a model organism for studying closed-head TBI. In this paper, we deliver a TBI to flies early in adult life, and then measure molecular and physiological phenotypes at short-, mid-, and long-term timepoints following the injury. We aim to identify the timing of changes that contribute to neurodegeneration. Here we confirm prior work demonstrating a TBI-induced decline in lifespan, and present evidence of a progressive decline in locomotor function, robust acute and modest chronic neuroinflammation, and a late-onset increase in protein aggregation. We also present evidence of metabolic dysfunction, in the form of starvation sensitivity and decreased lipids, that persists beyond the immediate injury response, but does not differ long-term. An intervention of dietary restriction (DR) partially ameliorates some TBI-induced phenotypes, including lifespan and locomotor function, though it does not alter the pattern of starvation sensitivity of injured flies. In the future, molecular pathways identified as altered following TBI—particularly in the short-, or mid-term—could present potential therapeutic targets.

TOR signalling is required for host lipid metabolic remodelling and survival following enteric infection in Drosophila

When infected by enteric pathogenic bacteria, animals need to initiate local and whole-body defence strategies. Although most attention has focused on the role of innate immune anti-bacterial responses, less is known about how changes in host metabolism contribute to host defence. Using Drosophila as a model system, we identify induction of intestinal target-of-rapamycin (TOR) kinase signalling as a key adaptive metabolic response to enteric infection. We find that enteric infection induces both local and systemic induction of TOR independently of the Immune deficiency (IMD) innate immune pathway, and we see that TOR functions together with IMD signalling to promote infection survival. These protective effects of TOR signalling are associated with remodelling of host lipid metabolism. Thus, we see that TOR is required to limit excessive infection-mediated wasting of host lipid stores by promoting an increase in the levels of gut- and fat body-expressed lipid synthesis genes. Our data support a model in which induction of TOR represents a host tolerance response to counteract infection-mediated lipid wasting in order to promote survival. This article has an associated First Person interview with the first author of the paper.

Role of cell competition in ageing

Recent advances in rapid medical detection and diagnostic technology have extended both human health and life expectancy. However, ageing remains one of the critical risk factors in contributing to major incapacitating and fatal conditions, including cancer and neurodegeneration. Therefore, it is vital to study how ageing attributes to (or participates in) endangering human health via infliction of age-related diseases and what must be done to tackle this intractable process. This review encompasses the most recent literature elaborating the role of cell competition (CC) during ageing. CC is a process that occurs between two heterogeneous populations, where the cells with higher fitness levels have a competitive advantage over the neighbouring cells that have comparatively lower fitness levels. This interaction results in the selection of the fit cells, within a population, and elimination of the viable yet suboptimal cells. Therefore, it is tempting to speculate that, if this quality control mechanism works efficiently throughout life, can it ultimately lead to a healthier ageing and extended lifespan. Furthermore, the review aims to collate all the important state of the art publications that provides evidence of the relevance of CC in dietary restriction, stem cell dynamics, and cell senescence, thus, prompting us to advocate its contribution and in exploring new avenues and opportunities in fighting age-related conditions.

Rapamycin inhibits pathogen transmission in mosquitoes by promoting immune activation

Repeated blood meals provide essential nutrients for mosquito egg development and routes for pathogen transmission. The target of rapamycin, the TOR pathway, is essential for vitellogenesis. However, its influence on pathogen transmission remains to be elucidated. Here, we show that rapamycin, an inhibitor of the TOR pathway, effectively suppresses Plasmodium berghei infection in Anopheles stephensi. An. stephensi injected with rapamycin or feeding on rapamycin-treated mice showed increased resistance to P. berghei infection. Exposing An. stephensi to a rapamycin-coated surface not only decreased the numbers of both oocysts and sporozoites but also impaired mosquito survival and fecundity. Transcriptome analysis revealed that the inhibitory effect of rapamycin on parasite infection was through the enhanced activation of immune responses, especially the NF-κB transcription factor REL2, a regulator of the immune pathway and complement system. Knockdown of REL2 in rapamycin-treated mosquitoes abrogated the induction of the complement-like proteins TEP1 and SPCLIP1 and abolished rapamycin-mediated refractoriness to Plasmodium infection. Together, these findings demonstrate a key role of the TOR pathway in regulating mosquito immune responses, thereby influencing vector competence.

Anautogenous mosquitoes must consume vertebrate blood meals to complete oogenesis. Repeated blood feeding makes the mosquitoes efficient disease-transmitting vectors. The TOR pathway activated by ingested blood is known as an important regulator for vitellogenesis in mosquitoes. Herein, we show that the protein kinase TOR is involved in the regulation of mosquitoes’ susceptibility to Plasmodium infection. Inhibition of the TOR pathway by rapamycin upregulates the expression of REL2, a transcription factor controlling the expression of a variety of immune effectors. The enhanced immune responses in turn promote parasite elimination. Therefore, the TOR pathway plays a dual role in not only regulating mosquito reproduction but also in their vector potential.

Metabolic Factors Affecting Tumor Immunogenicity: What Is Happening at the Cellular Level?

Immunotherapy has changed the treatment paradigm in multiple solid and hematologic malignancies. However, response remains limited in a significant number of cases, with tumors developing innate or acquired resistance to checkpoint inhibition. Certain "hot" or "immune-sensitive" tumors become "cold" or "immune-resistant", with resultant tumor growth and disease progression. Multiple factors are at play both at the cellular and host levels. The tumor microenvironment (TME) contributes the most to immune-resistance, with nutrient deficiency, hypoxia, acidity and different secreted inflammatory markers, all contributing to modulation of immune-metabolism and reprogramming of immune cells towards pro- or anti-inflammatory phenotypes. Both the tumor and surrounding immune cells require high amounts of glucose, amino acids and fatty acids to fulfill their energy demands. Thus, both compete over one pool of nutrients that falls short on needs, obliging cells to resort to alternative adaptive metabolic mechanisms that take part in shaping their inflammatory phenotypes. Aerobic or anaerobic glycolysis, oxidative phosphorylation, tryptophan catabolism, glutaminolysis, fatty acid synthesis or fatty acid oxidation, etc. are all mechanisms that contribute to immune modulation. Different pathways are triggered leading to genetic and epigenetic modulation with consequent reprogramming of immune cells such as T-cells (effector, memory or regulatory), tumor-associated macrophages (TAMs) (M1 or M2), natural killers (NK) cells (active or senescent), and dendritic cells (DC) (effector or tolerogenic), etc. Even host factors such as inflammatory conditions, obesity, caloric deficit, gender, infections, microbiota and smoking status, may be as well contributory to immune modulation, anti-tumor immunity and response to immune checkpoint inhibition. Given the complex and delicate metabolic networks within the tumor microenvironment controlling immune response, targeting key metabolic modulators may represent a valid therapeutic option to be combined with checkpoint inhibitors in an attempt to regain immune function.

How insects protect themselves against combined starvation and pathogen challenges, and the implications for reductionism

An explosion of data has provided detailed information about organisms at the molecular level. For some traits, this information can accurately predict phenotype. However, knowledge of the underlying molecular networks often cannot be used to accurately predict higher order phenomena, such as the response to multiple stressors. This failure raises the question of whether methodological reductionism is sufficient to uncover predictable connections between molecules and phenotype. This question is explored in this paper by examining whether our understanding of the molecular responses to food limitation and pathogens in insects can be used to predict their combined effects. The molecular pathways underlying the response to starvation and pathogen attack in insects demonstrates the complexity of real-world physiological networks. Although known intracellular signaling pathways suggest that food restriction should enhance immune function, a reduction in food availability leads to an increase in some immune components, a decrease in others, and a complex effect on disease resistance in insects such as the caterpillar Manduca sexta. However, our inability to predict the effects of food restriction on disease resistance is likely due to our incomplete knowledge of the intra- and extracellular signaling pathways mediating the response to single or multiple stressors. Moving from molecules to organisms will require novel quantitative, integrative and experimental approaches (e.g. single cell RNAseq). Physiological networks are non-linear, dynamic, highly interconnected and replete with alternative pathways. However, that does not make them impossible to predict, given the appropriate experimental and analytical tools. Such tools are still under development. Therefore, given that molecular data sets are incomplete and analytical tools are still under development, it is premature to conclude that methodological reductionism cannot be used to predict phenotype.

Testing evolutionary explanations for the lifespan benefit of dietary restriction in fruit flies (Drosophila melanogaster)

Dietary restriction (DR), limiting calories or specific nutrients without malnutrition, extends lifespan across diverse taxa. Traditionally, this lifespan extension has been explained as a result of diet-mediated changes in the trade-off between lifespan and reproduction, with survival favored when resources are scarce. However, a recently proposed alternative suggests that the selective benefit of the response to DR is the maintenance of reproduction. This hypothesis predicts that lifespan extension is a side effect of benign laboratory conditions, and DR individuals would be frailer and unable to deal with additional stressors, and thus lifespan extension should disappear under more stressful conditions. We tested this by rearing outbred female fruit flies (Drosophila melanogaster) on 10 different protein:carbohydrate diets. Flies were either infected with a bacterial pathogen (Pseudomonas entomophila), injured with a sterile pinprick, or unstressed. We monitored lifespan, fecundity, and measures of aging. DR extended lifespan and reduced reproduction irrespective of injury and infection. Infected flies on lower protein diets had particularly poor survival. Exposure to infection and injury did not substantially alter the relationship between diet and aging patterns. These results do not provide support for lifespan extension under DR being a side effect of benign laboratory conditions.

Resisting Resistance to Immune Checkpoint Therapy: A Systematic Review

The treatment landscape in oncology has witnessed a major revolution with the introduction of checkpoint inhibitors: anti-PD1, anti-PDL1 and anti-CTLA-4. These agents enhance the immune response towards cancer cells instead of targeting the tumor itself, contrary to standard chemotherapy. Although long-lasting durable responses have been observed with immune checkpoints inhibitors, the response rate remains relatively low in many cases. Some patients respond in the beginning but then eventually develop acquired resistance to treatment and progress. Other patients having primary resistance never respond. Multiple studies have been conducted to further elucidate these variations in response in different tumor types and different individuals. This paper provides an overview of the mechanisms of resistance to immune checkpoint inhibitors and highlights the possible therapeutic approaches under investigation aiming to overcome such resistance in order to improve the clinical outcomes of cancer patients.

Protein and calorie restriction may improve outcomes in living kidney donors and kidney transplant recipients

Previously, we and others showed that dietary restriction protects against renal ischemia-reperfusion injury in animals. However, clinical translation of preoperative diets is scarce, and in the setting of kidney transplantation these data are lacking. In this pilot study, we investigated the effects of five days of a preoperative protein and caloric dietary restriction (PCR) diet in living kidney donors on the perioperative effects in donors, recipients and transplanted kidneys. Thirty-five kidney donors were randomized into either the PCR, 30% calorie and 80% protein reduction, or control group without restrictions. Adherence to the diet and kidney function in donors and their kidney recipients were analyzed. Perioperative kidney biopsies were taken in a selected group of transplanted kidneys for gene expression analysis. All donors adhered to the diet. From postoperative day 2 up until month 1, kidney function of donors was significantly better in the PCR-group. PCR-donor kidney recipients showed significantly improved kidney function and lower incidence of slow graft function and acute rejection. PCR inhibited cellular immune response pathways and activated stress-resistance signaling. These observations are the first to show that preoperative dietary restriction induces postoperative recovery benefits in humans and may be beneficial in clinical settings involving ischemia-reperfusion injury.

Cell Intrinsic and Systemic Metabolism in Tumor Immunity and Immunotherapy

Immune checkpoint inhibitor (ICI) therapy has shown extraordinary promise at treating cancers otherwise resistant to treatment. However, for ICI therapy to be effective, it must overcome the metabolic limitations of the tumor microenvironment. Tumor metabolism has long been understood to be highly dysregulated, with potent immunosuppressive effects. Moreover, T cell activation and longevity within the tumor microenvironment are intimately tied to T cell metabolism and are required for the long-term efficacy of ICI therapy. We discuss in this review the intersection of metabolic competition in the tumor microenvironment, T cell activation and metabolism, the roles of tumor cell metabolism in immune evasion, and the impact of host metabolism in determining immune surveillance and ICI therapy outcomes. We also discussed the effects of obesity and calorie restriction—two important systemic metabolic perturbations that impact intrinsic metabolic pathways in T cells as well as cancer cells.

The Genetic Basis of Natural Variation in Drosophila melanogaster Immune Defense against Enterococcus faecalis

Dissecting the genetic basis of natural variation in disease response in hosts provides insights into the coevolutionary dynamics of host-pathogen interactions. Here, a genome-wide association study of Drosophila melanogaster survival after infection with the Gram-positive entomopathogenic bacterium Enterococcus faecalis is reported. There was considerable variation in defense against E. faecalis infection among inbred lines of the Drosophila Genetics Reference Panel. We identified single nucleotide polymorphisms associated with six genes with a significant (p < 10^-08, corresponding to a false discovery rate of 2.4%) association with survival, none of which were canonical immune genes. To validate the role of these genes in immune defense, their expression was knocked-down using RNAi and survival of infected hosts was followed, which confirmed a role for the genes krishah and S6k in immune defense. We further identified a putative role for the Bomanin gene BomBc1 (also known as IM23), in E. faecalis infection response. This study adds to the growing set of association studies for infection in Drosophila melanogaster and suggests that the genetic causes of variation in immune defense differ for different pathogens.

Factors that affect the translation of dietary restriction into a longer life

Nutritional interventions, such as dietary or calorie restriction, are known to have a variety of health-promoting effects. The most impressive are the direct effects on life expectancy, which have been reproduced in many animal models. A variety of dietary restriction protocols have been described, which differ either in their macronutrient composition or in the time window for consumption. Mechanistically, the effects of dietary restriction are mediated mainly through signaling pathways that have central roles in the maintenance of cellular energy balance. Among these, target of rapamycin and insulin signaling appear to be the most important. Such nutritional interventions can have their effects in two different ways: either by direct interaction with the metabolism of the host organism, or by modulating the composition and performance of its endogenous microbiome. Various dietary restriction regimens have been identified that significantly alter the microbiome and thus profoundly modulate host metabolism. This review aims to discuss the mechanisms by which dietary restriction can affect life expectancy, and in particular the role of the microbiome.

Macronutrients modulate survival to infection and immunity in Drosophila

Immunity and nutrition are two essential modulators of individual fitness. However, while the implications of immune function and nutrition on an individual's lifespan and reproduction are well established, the interplay between feeding behaviour, infection and immune function remains poorly understood. Asking how ecological and physiological factors affect immune responses and resistance to infections is a central theme of eco‐immunology.

In this study, we used the fruit fly, Drosophila melanogaster, to investigate how infection through septic injury modulates nutritional intake and how macronutrient balance affects survival to infection by the pathogenic Gram‐positive bacterium Micrococcus luteus.

Our results show that infected flies maintain carbohydrate intake, but reduce protein intake, thereby shifting from a protein‐to‐carbohydrate (P:C) ratio of ~1:4 to ~1:10 relative to non‐infected and sham‐infected flies. Strikingly, the proportion of flies dying after M. luteus infection was significantly lower when flies were fed a low‐P high‐C diet, revealing that flies shift their macronutrient intake as means of nutritional self‐medication against bacterial infection.

These results are likely due to the effects of the macronutrient balance on the regulation of the constitutive expression of innate immune genes, as a low‐P high‐C diet was linked to an upregulation in the expression of key antimicrobial peptides.

Together, our results reveal the intricate relationship between macronutrient intake and resistance to infection and integrate the molecular cross‐talk between metabolic and immune pathways into the framework of nutritional immunology.

Diet restriction-induced healthy aging is mediated through the immune signaling component ZIP-2 in Caenorhabditis elegans

Dietary restriction (DR) robustly delays the aging process in all animals tested so far. DR slows aging by negatively regulating the target of rapamycin (TOR) and S6 kinase (S6K) signaling pathway and thus inhibiting translation. Translation inhibition in C. elegans is known to activate the innate immune signal ZIP-2. Here, we show that ZIP-2 is activated in response to DR and in feeding-defective eat-2 mutants. Importantly, ZIP-2 contributes to the improvements in longevity and healthy aging, including mitochondrial integrity and physical ability, mediated by DR in C. elegans. We further show that ZIP-2 is activated upon inhibition of TOR/S6K signaling. However, DR-mediated activation of ZIP-2 does not require the TOR/S6K effector PHA-4/FOXA. Furthermore, zip-2 was not activated or required for longevity in daf-2 mutants, which mimic a low nutrition status. Thus, DR appears to activate ZIP-2 independently of PHA-4/FOXA and DAF-2. The link between DR, aging, and immune activation provides practical insight into the DR-induced benefits on health span and longevity.

Immunometabolism: Insights from the Drosophila model

Multicellular organisms inhabit an environment that includes a mix of essential nutrients and large numbers of potentially harmful microbes. Germline-encoded receptors scan the environment for microbe associated molecular patterns, and, upon engagement, activate powerful defenses to protect the host from infection. At the same time, digestive enzymes and transporter molecules sieve through ingested material for building blocks and energy sources necessary for survival, growth, and reproduction. We tend to view immune responses as a potent array of destructive forces that overwhelm potentially harmful agents. In contrast, we view metabolic processes as essential, constructive elements in the maintenance and propagation of life. However, there is considerable evidence of functional overlap between the two processes, and disruptions to one frequently modify outputs of the other. Studies of immunometabolism, or interactions between immunity and metabolism, have increased in prominence with the discovery of inflammatory components to metabolic diseases such as type two diabetes. In this review, we will focus on contributions of studies with the fruit fly, Drosophila melanogaster, to our understanding of immunometabolism. Drosophila is widely used to study immune signaling, and to understand the regulation of metabolism in vivo, and this insect has considerable potential as a tool to build our understanding of the molecular and cellular bridges that connect immune and metabolic pathways.

Perturbation of IIS/TOR signaling alters the landscape of sex-differential gene expression in Drosophila

Background

The core functions of the insulin/insulin-like signaling and target of rapamycin (IIS/TOR) pathway are nutrient sensing, energy homeostasis, growth, and regulation of stress responses. This pathway is also known to interact directly and indirectly with the sex determination regulatory hierarchy. The IIS/TOR pathway plays a role in directing sexually dimorphic traits, including dimorphism of growth, metabolism, stress and behavior. Previous studies of sexually dimorphic gene expression in the adult head, which includes both nervous system and endocrine tissues, have revealed variation in sex-differential expression, depending in part on genotype and environment. To understand the degree to which the environmentally responsive insulin signaling pathway contributes to sexual dimorphism of gene expression, we examined the effect of perturbation of the pathway on gene expression in male and female Drosophila heads.

Results

Our data reveal a large effect of insulin signaling on gene expression, with greater than 50% of genes examined changing expression. Males and females have a shared gene expression response to knock-down of InR function, with significant enrichment for pathways involved in metabolism. Perturbation of insulin signaling has a greater impact on gene expression in males, with more genes changing expression and with gene expression differences of larger magnitude. Primarily as a consequence of the response in males, we find that reduced insulin signaling results in a striking increase in sex-differential expression. This includes sex-differences in expression of immune, defense and stress response genes, genes involved in modulating reproductive behavior, genes linking insulin signaling and ageing, and in the insulin signaling pathway itself.

Conclusions

Our results demonstrate that perturbation of insulin signaling results in thousands of genes displaying sex differences in expression that are not differentially expressed in control conditions. Thus, insulin signaling may play a role in variability of somatic, sex-differential expression. The finding that perturbation of the IIS/TOR pathway results in an altered landscape of sex-differential expression suggests a role of insulin signaling in the physiological underpinnings of trade-offs, sexual conflict and sex differences in expression variability.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5308-3) contains supplementary material, which is available to authorized users.

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.

Identification of differentially expressed genes in cervical cancer by bioinformatics analysis

Cervical cancer is the most common gynecological malignancy. In recent years, the incidence of cervical cancer has had a younger trend. Cervical cancer morbidity and mortality rates have been significantly reduced due to recent decades of cervical cytology screening leading to the early detection and treatment of cervical cancer and precancerous lesions. There are a number of methods used to treat cervical cancer and improve the survival rate. However, the prevalence and recurrence rates of cervical cancer are increasing every year. There is an urgent requirement for a better understanding of the molecular mechanism cervical cancer development. The present study used scientific information retrieval from the Gene Expression Omnibus database to download the GSE26511 dataset, which contained 39 samples, including 19 cervical cancer lymph node-positive samples and 20 cervical cancer lymph node-negative samples. Using Gene Ontology analysis, Kyoto Encyclopedia of Genes and Genomes analysis, and weighted gene co-expression network analysis, 1,263 differentially expressed genes were found that affected the biological processes, including 'cell cycle process', 'signaling pathways', 'immune response', 'cell activation', 'regulation of immune system process' and 'inflammatory response'. These areas should be the focus of study for cervical cancer in the future.

Nuclear-cytoplasmic shuttling protein PP2AB56 contributes to mTORC1-dependent dephosphorylation of FOXK1

Mammalian target of rapamycin complex 1 (mTORC1) kinase is a master regulator of the cellular response to nutrition-related signals such as insulin and amino acids. mTORC1 is activated on the lysosomal membrane and induces phosphorylation of a variety of downstream molecules. We previously showed that activated mTORC1 induces protein phosphatase 2A (PP2A)-mediated dephosphorylation of the transcription factor forkhead box K1 (FOXK1). The mechanism underlying the signal transduction from the cytoplasmic mTORC1 to the nuclear FOXK1 has remained unclear, however, we now show that a nuclear-cytoplasmic transport system is necessary for the mTORC1-FOXK1 signal transduction. This reaction is mediated by a shuttling protein B56, which is a regulatory subunit of PP2A and plays an essential role in the mTORC1-dependent dephosphorylation of FOXK1. These results suggest that PP2A^B56 phosphatase contributes to the signaling for mTORC1-dependent transcriptional regulation.

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.

KIF17 mediates the learning and memory impairment in offspring induced by maternal exposure to propofol during middle pregnancy

Preclinical studies suggest that propofol may cause neuronal injury to the developing brain. A previous study demonstrated that, in a rat model, maternal exposure to propofol during early or late pregnancy caused learning and memory impairment in the offspring. However, whether propofol exposure during middle pregnancy can cause long‑term behavioral deficits in the offspring remains to be elucidated. N‑methyl‑D‑aspartate receptor 2B subunit (NR2B) serves a critical role in memory modulation. To exert its function, NR2B must be transported to the neuronal membrane by kinesin family member 17 (KIF17). The aim of the present study was to investigate the role of KIF17 in learning and memory impairment in rat offspring caused by propofol exposure during middle pregnancy. Pregnant rats were exposed to propofol on gestational day 14 (G14) for 4 and 8 h, with control pregnant rats receiving an equal volume of normal saline. The learning and memory of the offspring was assessed using Morris water maze tests from postnatal day 30 (P30) to P36. The levels of KIF17 protein, total NR2B (T‑NR2B) and membrane NR2B (M‑NR2B) in the hippocampus were detected using western blotting. The results demonstrated that propofol exposure caused learning and memory deficits and decreased KIF17 and M‑NR2B protein levels in the hippocampus; however, no but changes in the expression of T‑NR2B were observed. These results indicate that maternal propofol exposure during middle pregnancy impairs learning and memory in offspring rats by suppressing the expression of KIF17 and inhibiting the translocation of NR2B to the neuronal membrane.

Can Protein Restriction Set Up T Lymphocytes Favorably For Their Activation Against Pathogens Through Myc?

One area that presents a significant threat to global health is infectious diseases. With increasing prevalence of antibiotic-resistant bacteria [1], opportunistic infections are a growing concern for human societies. In 2009, there were 89,000 deaths caused by pneumonia, septicemia, and influenza virus in the United States alone [2]. Antibiotic-resistant bacteria increase the risk of secondary infection that is associated with many standard medical procedures such as organ transplantation, chemotherapy, dialysis, and elective surgery [1]. The deceleration of new drug discovery suggests that acute preventative strategies strengthening host immunity prior to such procedures are of strong interest. In this mini review, I will suggest a protein restriction-Myc signaling as a potential pharmacological target to boost the survival outcome following pathogenic bacterial infection.