Insulin/insulin-like Growth Factor Signaling Research Articles

Sulforaphane Exposure Prevents Cadmium-Induced Toxicity and Mitochondrial Dysfunction in the Nematode Caenorhabditis elegans by Regulating the Insulin/Insulin-like Growth Factor Signaling (IIS) Pathway.

Cadmium (Cd) is a heavy metal that is highly toxic to humans and animals. Its adverse effects have been widely associated with mitochondrial alterations. However, there are not many treatments that target mitochondria. This study aimed to evaluate the impact of sulforaphane (SFN) pre-exposure against cadmium chloride (CdCl2)-induced toxicity and mitochondrial alterations in the nematode Caenorhabditis elegans (C. elegans), by exploring the role of the insulin/insulin-like growth factor signaling pathway (IIS). The results revealed that prior exposure to SFN protected against CdCl2-induced mortality and increased lifespan, body length, and mobility while reducing lipofuscin levels. Furthermore, SFN prevented mitochondrial alterations by increasing mitochondrial membrane potential (Δψm) and restoring mitochondrial oxygen consumption rate, thereby decreasing mitochondrial reactive oxygen species (ROS) production. The improvement in mitochondrial function was associated with increased mitochondrial mass and the involvement of the daf-16 and skn-1c genes of the IIS signaling pathway. In conclusion, exposure to SFN before exposure to CdCl2 mitigates toxic effects and mitochondrial alterations, possibly by increasing mitochondrial mass, which may be related to the regulation of the IIS pathway. These discoveries open new possibilities for developing therapies to reduce the damage caused by Cd toxicity and oxidative stress in biological systems, highlighting antioxidants with mitochondrial action as promising tools.

Mulberrin extends lifespan in Caenorhabditis elegans through detoxification function.

Mulberrin, a naturally occurring flavone found in mulberry and Romulus Mori, exhibits diverse biological functions. Here, we showed that mulberrin extended both the lifespan and healthspan in C. elegans. Moreover, mulberrin increased the worms' resistance to toxicants and activated the expression of detoxification genes. The longevity-promoting effect of mulberrin was attenuated in nuclear hormone receptor (NHR) homologous nhr-8 and daf-12 mutants, indicating that the lifespan extending effects of mulberrin in C. elegans may depend on nuclear hormone receptors NHR-8/DAF-12. Further analyses revealed the potential associations between the longevity effects of mulberrin and the insulin/insulin-like growth factor signaling (IIS) and adenosine 5'-monophosphate-activated protein kinase (AMPK) pathways. Together, our findings suggest that mulberrin may prolong lifespan and healthspan by activating detoxification functions mediated by nuclear receptors.

Piwi expressed in Drosophila adipose tissues regulates systemic IGF signaling and growth via IGF-binding protein

Piwi and its partner, Piwi-interacting RNA (piRNA), are pivotal in suppressing the harmful effects of transposable elements (TEs) linked to genomic insertional mutagenesis. While primarily active in Drosophila's adult gonadal tissues, causing sterility in its absence, Piwi's role in post-embryonic development remains unclear. Our study reveals Piwi's functional presence in the larval fat body, where it governs developmental growth through systemic insulin/insulin-like growth factor (IGF) signaling (IIS). Piwi knockdown in the fat body resulted in dysregulated TE expression, reduced developmental rate and body growth, and diminished systemic IIS activity. Notably, Piwi knockdown increased Imaginal Morphogenic Protein Late 2 (Imp-L2) expression, akin to insulin-like growth factor-binding protein 7 (IGFBP7), reducing systemic IIS and inhibiting body growth. This unveils a novel role for Piwi in larval adipose tissues, emphasizing its importance in regulating systemic IIS and overall organismal growth.

Sustained Nrf2 Overexpression-Induced Metabolic Deregulation Can Be Attenuated by Modulating Insulin/Insulin-like Growth Factor Signaling.

The modulation of insulin/insulin-like growth factor signaling (IIS) is associated with altered nutritional and metabolic states. The Drosophila genome encodes eight insulin-like peptides, whose activity is regulated by a group of secreted factors, including Ecdysone-inducible gene L2 (ImpL2), which acts as a potent IIS inhibitor. We recently reported that cncC (cncC/Nrf2), the fly ortholog of Nrf2, is a positive transcriptional regulator of ImpL2, as part of a negative feedback loop aiming to suppress cncC/Nrf2 activity. This finding correlated with our observation that sustained cncC/Nrf2 overexpression/activation (cncCOE; a condition that signals organismal stress) deregulates IIS, causing hyperglycemia, the exhaustion of energy stores in flies' tissues, and accelerated aging. Here, we extend these studies in Drosophila by assaying the functional implication of ImpL2 in cncCOE-mediated metabolic deregulation. We found that ImpL2 knockdown (KD) in cncCOE flies partially reactivated IIS, attenuated hyperglycemia and restored tissue energetics. Moreover, ImpL2 KD largely suppressed cncCOE-mediated premature aging. In support, pharmacological treatment of cncCOE flies with Metformin, a first-line medication for type 2 diabetes, restored (dose-dependently) IIS functionality and extended cncCOE flies' longevity. These findings exemplify the effect of chronic stress in predisposition to diabetic phenotypes, indicating the potential prophylactic role of maintaining normal IIS functionality.

Insight into phenotypic plasticity in planthoppers.

Planthoppers possess an impressive ability to exhibit phenotypic plasticity, which allows them to adjust their morphology for migration, overwintering, and adaptation to different environmental conditions. The wing and color polyphenism are the two most outward morphologies. Wing polyphenism serves as a classic illustration of a life history trade-off between reproduction and migration, while color polyphenism is potentially correlated with the insect development and immunity. In this review, we present the important contributions that link environment cues to wing and color polyphenism, and highlight recent advances in insulin/insulin-like growth factor signaling-forkhead transcription factor subgroup O (FoxO) pathway-mediated wing development and tyrosine-melanin pathway-mediated coloration. Further work, particularly in the identification of the genes that FoxO regulates and in the elucidation of the intracellular signals that link the stimuli to the tyrosine-melanin pathway, is required.

D-pinitol ameliorated H2O2-induced oxidative damage in PC12 cells and prolonged the lifespan by IIS pathway in Caenorhabditis elegans

D-pinitol (DP) has been extensively regarded as the main active component of legumes for anti-aging. In this study, we intended to explore the anti-aging mechanism of DP, utilizing computer modeling techniques. The results demonstrated that DP significantly delayed H2O2-induced cellular senescence. Model PC12 cells treated with DP exhibited increased cell viability, increased antioxidant enzyme activity (SOD, CAT), and reduced ROS and MDA levels. Furthermore, DP was discovered to have a positive effect on healthy longevity. In C. elegans, DP treatment enhanced lifespan, stress capacity, antioxidant capacity (T-SOD/CAT/GSH-Px/MDA/ROS), and altered aging-related indicators of lipofuscin accumulation, pharyngeal pump rate, motility, and reproduction. Moreover, DP could reduce the toxicity Aβ in transgenic C. elegans CL4176, CL2355, and CL2331. Further mechanistic studies indicated DP increased transcription factor (daf-16, skn-1, hsf-1) expression of insulin/insulin-like growth factor-1 signaling (IIS) pathway. As expected, DP also extended the downstream target genes of the three transcription factors (sod-3, ctl-1, ctl-2, gst-4, hsp-16.1, and hsp-16.2). Further mutant lifespan experiments, network pharmacology, and molecular docking revealed that DP might be life-extending through the IIS pathway. DP deserves extensive investigation and development as a potential anti-aging drug in the future.

Reduced insulin signaling in neurons induces sex-specific health benefits.

Reduced activity of insulin/insulin-like growth factor signaling (IIS) extends health and life span in mammals. Loss of the insulin receptor substrate 1 (Irs1) gene increases survival in mice and causes tissue-specific changes in gene expression. However, the tissues underlying IIS-mediated longevity are currently unknown. Here, we measured survival and health span in mice lacking IRS1 specifically in liver, muscle, fat, and brain. Tissue-specific loss of IRS1 did not increase survival, suggesting that lack of IRS1 in more than one tissue is required for life-span extension. Loss of IRS1 in liver, muscle, and fat did not improve health. In contrast, loss of neuronal IRS1 increased energy expenditure, locomotion, and insulin sensitivity, specifically in old males. Neuronal loss of IRS1 also caused male-specific mitochondrial dysfunction, activation of Atf4, and metabolic adaptations consistent with an activated integrated stress response at old age. Thus, we identified a male-specific brain signature of aging in response to reduced IIS associated with improved health at old age.

A novel peptide derived from Haematococcus pluvialis residue exhibits anti-aging activity in Caenorhabditis elegans via the insulin/IGF-1 signaling pathway.

To explore the value of Haematococcus pluvialis (H. pluvialis) residue remaining after astaxanthin extraction and being discarded uneconomically, in our previous study, we discovered a novel peptide (HPp) as a potential bioactive component. However, the possible anti-aging activity in vivo was not illuminated. In this study, the capacity of extending the lifespan and the mechanism based on Caenorhabditis elegans (C. elegans) were determined. The results showed that 100 μM HPp not only enhanced the lifespan of C. elegans in normal environments by 20.96% but also strengthened the lifespan in oxidative and thermal conditions effectively. Moreover, HPp succeeded in lessening the decline in physiological functions of aging worms. In terms of antioxidant efficacy, SOD and CAT enzyme activity were promoted, but the level of MDA was diminished significantly after HPp treatment. Subsequent analysis directly reflected the relationship between higher stress resistance and up-regulation of skn-1 and hsp-16.2, and between greater antioxidant ability and up-regulation of sod-3 and ctl-2. Further studies illustrated that HPp up-graded the mRNA transcription of the genes associated with the insulin/insulin-like growth factor signaling (IIS) pathway and some co-factors, including daf-16, daf-2, ins-18, and sir-2.1. Particularly, the activation of the IIS pathway required the regulation of subcellular localization of DAF-16/FOXO. Taken together, HPp could promote longevity with improved stress resistance and antioxidant properties in vivo through the IIS pathway. These data suggested that HPp might serve as a good source of anti-aging actives, and in particular, laid a foundation for the high value-added application of marine microalgae.

The insulin and IGF signaling pathway sustains breast cancer stem cells by IRS2/PI3K-mediated regulation of MYC.

Despite the strong association of the insulin/insulin-like growth factor (IGF) signaling (IIS) pathway with tumor initiation, recurrence, and metastasis, the mechanism by which this pathway regulates cancer progression is not well understood. Here, we report that IIS supports breast cancer stem cell (CSC) self-renewal in an IRS2-phosphatidylinositol 3-kinase (PI3K)-dependent manner that involves the activation and stabilization of MYC. IRS2-PI3K signaling enhances MYC expression through the inhibition of GSK3β activity and suppression of MYC phosphorylation on threonine 58, thus reducing proteasome-mediated degradation of MYC and sustaining active pS62-MYC function. A stable T58A-Myc mutant rescues CSC function in Irs2-/- cells, supporting the role of this MYC stabilization in IRS2-dependent CSC regulation. These findings establish a mechanistic connection between the IIS pathway and MYC and highlight a role for IRS2-dependent signaling in breast cancer progression.

Mitochondria dysfunction impairs Tribolium castaneum wing development during metamorphosis

The disproportionate growth of insect appendages such as facultative growth of wings and exaggeration of beetle horns are examples of phenotypic plasticity. Insect metamorphosis is the critical stage for development of pupal and adult structures and degeneration of the larval cells. How the disproportionate growth of external appendages is regulated during tissue remodeling remains unanswered. Tribolium castaneum is used as a model to study the function of mitochondria in metamorphosis. Mitochondrial dysfunction is achieved by the knockdown of key mitochondrial regulators. Here we show that mitochondrial function is not required for metamorphosis except that severe mitochondrial dysfunction blocks ecdysis. Surprisingly, various abnormal wing growth, including short and wingless phenotypes, are induced after knocking down mitochondrial regulators. Mitochondrial activity is regulated by IIS (insulin/insulin-like growth factor signaling)/FOXO (forkhead box, sub-group O) pathway through TFAM (transcription factor A, mitochondrial). RNA sequencing and differential gene expression analysis show that wing-patterning and insect hormone response genes are downregulated, while programmed cell death and immune response genes are upregulated in insect wing discs with mitochondrial dysfunction. These studies reveal that mitochondria play critical roles in regulating insect wing growth by targeting wing development during metamorphosis, thus showing a novel molecular mechanism underlying developmental plasticity.

Functional evaluation of the insulin/insulin-like growth factor signaling pathway in determination of wing polyphenism in pea aphid.

Wing polyphenism is a common phenomenon that plays key roles in environmental adaptation of insects. Insulin/insulin-like growth factor signaling (IIS) pathway is a highly conserved pathway in regulation of metabolism, development, and growth in metazoans. It has been reported that IIS is required for switching of wing morph in brown planthopper via regulating the development of the wing pad. However, it remains elusive whether and how IIS pathway regulates transgenerational wing dimorphism in aphid. In this study, we found that pairing and solitary treatments can induce pea aphids to produce high and low percentage winged offspring, respectively. The expression level of ILP5 (insulin-like peptide 5) in maternal head was significantly higher upon solitary treatment in comparison with pairing, while silencing of ILP5 caused no obvious change in the winged offspring ratio. RNA interference-mediated knockdown of FoxO (Forkhead transcription factor subgroup O) in stage 20 embryos significantly increased the winged offspring ratio. The results of pharmacological and quantitative polymerase chain reaction experiments showed that the embryonic insulin receptors may not be involved in wing polyphenism. Additionally, ILP4 and ILP11 exhibited higher expression levels in 1st wingless offspring than in winged offspring. We demonstrate that FoxO negatively regulates the wing morph development in embryos. ILPs may regulate aphid wing polyphenism in a developmental stage-specific manner. However, the regulation may be not mediated by the canonical IIS pathway. The findings advance our understanding of IIS pathway in insect transgenerational wing polyphenism.

Responses of bitter melon saponins to oxidative stress and aging via the IIS pathway linked with sir-2.1 and hlh-30.

Saponins from bitter melon (BMS) exert potential bioactivities and pharmacological activities, including anti-oxidation and lifespan extension. However, the exact mechanisms of BMS in response to oxidative stress remain unknown. Results demonstrated that bitter melon saponins could strengthen locomotive activities (body bend and head thrashing) accompanied by delaying the muscle fiber damage with age in Caenorhabditis elegans. In addition, BMS inhibited the ROS accumulation, improved the activities of antioxidant enzymes like SOD (by 57.90% and 94.34% for 100 μg/ml and 200 μg/ml BMS, respectively) and CAT (by 51.45% and 56.91% for 100 μg/ml and 200 μg/ml BMS, respectively), and extend the lifespan of N2 and CL2006 worms under paraquat-induced oxidative stress. Mechanism study suggested that BMS modulated the mRNA expressions of oxidation-related regulators, like the upregulation of cat-1, hsf-1, sir-2.1, and hlh-30. Furthermore, gene-deficient mutants verified that IIS (insulin/insulin-like growth factor-1 signaling) pathway linked with sir-2.1 and hlh-30 factors were involved in the BMS's lifespan-extension effects under oxidative stress. In general, this study supplemented the explanation of BMS in promoting oxidation-resistance and lifespan-extension activities, which could be served as a potential candidate for anti-aging. PRACTICAL APPLICATIONS: Our previous studies have suggested that saponins from bitter melon exhibited fat-lowering activity in C. elegans. However, little was known about the mechanism underlying the anti-oxidation effects of BMS in C. elegans. Current results indicated that the IIS pathway linked with sir-2.1 and hlh-30 transcriptional factors jointly to increase the lifespan in BMS' responses to oxidative stress. Our findings are beneficial to understand the main nutritional ingredients in bitter melon, which are ideal and expected in functional foods for aging.

RNA interference knockdown of insulin receptor inhibits ovarian development in Chilo suppressalis.

The nutritional signaling pathway regulates an insect's size, development, and lifespan, as well as playing a vital role in reproduction. The insulin/insulin-like growth factor signaling (IIS) pathway plays a key role in the nutrition signaling pathway. As an integral component of the IIS pathway, insulin receptor (InR), a receptor tyrosine kinase, plays a role in the insulin pathway by controlling reproduction in many insect species. However, the precise molecular function of InR in non-model insect reproduction is poorly understood. In our study, Chilo suppressalis, a well-known rice pest, was used as a molecular system to determine the role of InR in insect reproduction. Sequencing the InR gene of C. suppressalis, comparing the amino acid sequence-specific structure, and constructing a phylogenetic tree revealed that this gene has four main domains: ligand binding L domain, Furin-like region, fibronectin type III domains, and Tyrosine kinase catalytic domain, which were all highly conserved in insects. By characterizing the spatiotemporal expression profile of InR in different developmental stages and tissues, we found that InR gene expression was highest on the 3-day old in female pupae, 6th instar larvae, and fat body on the 6-day old in female pupae. InR gene expression may promote the molting and pupation of larvae and play a role in reproduction in the fat body. Furthermore, the RNA interference knockdown of InR dramatically reduced yolk deposition and blocked oocyte maturation. After suppression of InR, the expression of several other genes fluctuated to varying degrees. In conclusion, InR is vital to reproduction and is expected to become a new target for pest management.

Examination of the potential roles of insulin-like peptide receptor in regulating the growth of Manila clam Ruditapes philippinarum

The role of insulin/insulin-like growth factor (IGF) signaling pathway in the growth regulation of marine invertebrates has not been fully studied. In this study, the economically important species Ruditapes philippinarum was sacrificed to clarify the role of IGF system in the growth regulation of R. philippinarum by real-time quantitative PCR. Systematic bioinformatics analysis can identify the major genes of IGF signaling pathway and insulin-like peptide receptor (ILPR) - mediated signaling pathway in R. philippinarum. The expression levels of IGF and its downstream signaling pathway genes in larger clams were significantly higher than those in small clams, indicating that they were involved in the growth regulation of R. philippinarum. These results suggest that IGF signaling pathway and ILPR mediated signaling pathway to regulate the growth of R. philippinarum.

Parasite reliance on its host gut microbiota for nutrition and survival

Studying the microbial symbionts of eukaryotic hosts has revealed a range of interactions that benefit host biology. Most eukaryotes are also infected by parasites that adversely affect host biology for their own benefit. However, it is largely unclear whether the ability of parasites to develop in hosts also depends on host-associated symbionts, e.g., the gut microbiota. Here, we studied the parasitic wasp Leptopilina boulardi (Lb) and its host Drosophila melanogaster. Results showed that Lb successfully develops in conventional hosts (CN) with a gut microbiota but fails to develop in axenic hosts (AX) without a gut microbiota. We determined that developing Lb larvae consume fat body cells that store lipids. We also determined that much larger amounts of lipid accumulate in fat body cells of parasitized CN hosts than parasitized AX hosts. CN hosts parasitized by Lb exhibited large increases in the abundance of the bacterium Acetobacter pomorum in the gut, but did not affect the abundance of Lactobacillus fructivorans which is another common member of the host gut microbiota. However, AX hosts inoculated with A. pomorum and/or L. fructivorans did not rescue development of Lb. In contrast, AX larvae inoculated with A. pomorum plus other identified gut community members including a Bacillus sp. substantially rescued Lb development. Rescue was further associated with increased lipid accumulation in host fat body cells. Insulin-like peptides increased in brain neurosecretory cells of parasitized CN larvae. Lipid accumulation in the fat body of CN hosts was further associated with reduced Bmm lipase activity mediated by insulin/insulin-like growth factor signaling (IIS). Altogether, our results identify a previously unknown role for the gut microbiota in defining host permissiveness for a parasite. Our findings also identify a new paradigm for parasite manipulation of host metabolism that depends on insulin signaling and the gut microbiota.

Sonneradon A Extends Lifespan of Caenorhabditis elegans by Modulating Mitochondrial and IIS Signaling Pathways.

Aging is related to the lowered overall functioning and increased risk for various age-related diseases in humans. Sonneradon A (SDA), a new compound first extracted from the edible fruits of mangrove Sonneratia apetala, showed remarkable antiaging activity. However, the role of SDA in antiaging remains unclear. In this article, we studied the function of SDA in antiaging by using the animal model Caenorhabditis elegans. Results showed that SDA inhibited production of reactive oxygen species (ROS) by 53%, and reduced the accumulation of aging markers such as lipids and lipofuscins. Moreover, SDA also enhanced the innate immune response to Pseudomonas aeruginosa infection. Genetic analysis of a series of mutants showed that SDA extended the lifespan of the mutants of eat-2 and glp-1. Together, this effect may be related to the enhanced resistance to oxidative stress via mitochondrial and insulin/insulin-like growth factor-1 signaling (IIS) pathways. The results of this study provided new evidence for an antiaging effect of SDA in C. elegans, as well as insights into the implication of antiaging activity of SDA in higher organisms.

Tris(1,3-dichloro-2-propyl) phosphate reduces longevity through a specific microRNA-mediated DAF-16/FoxO in an unconventional insulin/insulin-like growth factor‑1 signaling pathway

Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) has received concerns due to its frequent detection in environmental media and biological samples. Our previous study has indicated TDCPP reduced the lifespan of Caenorhabditis elegans (C. elegans) by triggering an unconventional insulin/insulin-like growth factor signaling (IIS) pathway. This study continued to investigate the possible deleterious effects of TDCPP relating to longevity regulation signal pathways and biological processes. Specifically, this study uniquely performed small RNA transcriptome sequencing (RNA-seq), focusing on the underlying mechanisms of TDCPP-reduced the longevity of C. elegans in-depth in microRNAs (miRNAs). Based on Small RNA-seq results and transcript levels of mRNA involved in the unconventional IIS pathway, a small interaction network of miRNAs-mRNAs following TDCPP exposure in C. elegans was preliminarily established. Among them, up-regulated miR-48 and miR-84 (let-7 family members) silence the mRNA of daf-16 (the crucial member of the FoxO family and pivotal regulator in longevity) via post-transcription and translation dampening abilities, further inhibit its downstream target metallothionein-1 (mtl-1), and ultimately contributed to the reduction of nematode longevity and locomotion behaviors. Meanwhile, the high binding affinities of TDCPP with miRNAs cel-miR-48–5p and cel-miR-84–5p strongly support their participation in the regulation of nematode mobility and longevity. These findings provide a comprehensive analysis of TDCPP-reduced longevity from the perspective of miRNAs.

The transcription factor dFOXO controls the expression of insulin pathway genes and lipids content under heat stress in <i>Drosophila melanogaster</i>

The insulin/insulin-like growth factor signaling (IIS) pathway is one of the key elements in an organism’s response to unfavourable conditions. The deep homology of this pathway and its evolutionary conservative role in controlling the carbohydrate and lipid metabolism make it possible to use Drosophila melanogaster for studying its functioning. To identify the properties of interaction of two key IIS pathway components under heat stress in D. melanogaster (the forkhead box O transcription factor (dFOXO) and insulin-like peptide 6 (DILP6), which intermediates the dFOXO signal sent from the fat body to the insulin-producing cells of the brain where DILPs1–5 are synthesized), we analysed the expression of the genes dilp6, dfoxo and insulin-like receptor gene (dInR) in females of strains carrying the hypomorphic mutation dilp641 and hypofunctional mutation foxoBG01018. We found that neither mutation influenced dfoxo expression and its uprise under short-term heat stress, but both of them disrupted the stress response of the dilp6 and dInR genes. To reveal the role of identified disruptions in metabolism control and feeding behaviour, we analysed the effect of the dilp641 and foxoBG01018 mutations on total lipids content and capillary feeding intensity in imago under normal conditions and under short-term heat stress. Both mutations caused an increase in these parameters under normal conditions and prevented decrease in total lipids content following heat stress observed in the control strain. In mutants, feeding intensity was increased under normal conditions; and decreased following short-term heat stress in all studied strains for the first 24 h of observation, and in dilp641 strain, for 48 h. Thus, we may conclude that dFOXO takes part in regulating the IIS pathway response to heat stress as well as the changes in lipids content caused by heat stress, and this regulation is mediated by DILP6. At the same time, the feeding behaviour of imago might be controlled by dFOXO and DILP6 under normal conditions, but not under heat stress.

Insulin-Like Peptide and FoxO Mediate the Trehalose Catabolism Enhancement during the Diapause Termination Period in the Chinese Oak Silkworm (Antheraea pernyi)

Simple SummaryIn insects, the insulin/insulin-like growth factor signalling (IIS) pathway regulates the carbohydrate and lipid metabolisms, and plays important roles in diapause regulation. Trehalose accumulates in many diapausing insects, as it is a major carbohydrate reserve and a stress protectant. Because of metabolism depression, the trehalose concentration is maintained at relatively high levels over the diapause phase. In the present study, bovine insulin injection triggered diapause termination and synchronous eclosion in Antheraea pernyi pupae. Moreover, treatment with bovine insulin elevated the trehalose catabolism in diapausing pupae. As a homologue of vertebrate insulin, insulin-like peptide (ApILP) enhances the trehalose catabolism during the diapause termination process. The transcription factor forkhead box O (ApFoxO)—the downstream target of the IIS pathway—exhibited a contrasting effect on the trehalose catabolism to that of ApILP. These results suggest that ApILP and ApFoxO are involved in the regulation of trehalose catabolism during diapause termination in A. pernyi pupae.In insects, trehalose accumulation is associated with the insulin/insulin-like growth factor signalling (IIS) pathway. However, whether insulin-like peptide is involved in the regulation of the trehalose metabolism during diapause termination remains largely unknown. This study assessed whether insulin-like peptide (ApILP) enhances the trehalose catabolism in the pupae of Antheraea pernyi during their diapause termination process. Injection of 10 μg of bovine insulin triggered diapause termination and synchronous adult eclosion in diapausing pupae. Moreover, treatment with bovine insulin increased the expression of trehalase 1A (ApTre-1A) and trehalase 2 (ApTre-2), as well as the activity of soluble and membrane-bound trehalase, resulting in a decline in trehalose levels in the haemolymph. Silencing ApILP via RNA interference significantly suppressed the expression of ApTre-1A and ApTre-2, thus leading to an increase in the trehalose concentration during diapause termination. However, neither injection with bovine insulin nor ApILP knockdown directly affected trehalase 1B (ApTre-1B) expression. Moreover, overexpression of the transcription factor forkhead box O (ApFoxO) induced an increase in trehalose levels during diapause termination; however, depletion of ApFoxO accelerated the breakdown of trehalose in diapausing pupae by increasing the expression of ApTre-1A and ApTre-2. The results of this study help to understand the contributions of ApILP and ApFoxO to the trehalose metabolism during diapause termination.

The transcription factor dfoxo controls the expression of insulin pathway genes and lipids content under heat stress in Drosophila melanogaster.

The insulin/insulin-like growth factor signaling (IIS) pathway is one of the key elements in an organism’s response to unfavourable conditions. The deep homology of this pathway and its evolutionary conservative role in controlling the carbohydrate and lipid metabolism make it possible to use Drosophila melanogaster for studying its functioning. To identify the properties of interaction of two key IIS pathway components under heat stress in D. melanogaster (the forkhead box O transcription factor (dfoxo) and insulin-like peptide 6 (dilp6), which intermediates the dfoxo signal sent from the fat body to the insulin-producing cells of the brain where DILPs1–5 are synthesized), we analysed the expression of the genes dilp6, dfoxo and insulin-like receptor gene (dInR) in females of strains carrying the hypomorphic mutation dilp641and hypofunctional mutation foxoBG01018. We found that neither mutation inf luenced dfoxo expression and its uprise under short-term heat stress, but both of them disrupted the stress response of the dilp6 and dInR genes. To reveal the role of identif ied disruptions in metabolism control and feeding behaviour, we analysed the effect of the dilp641 and foxoBG01018 mutations on total lipids content and capillary feeding intensity in imago under normal conditions and under short-term heat stress. Both mutations caused an increase in these parameters under normal conditions and prevented decrease in total lipids content following heat stress observed in the control strain. In mutants, feeding intensity was increased under normal conditions; and decreased following short-term heat stress in all studied strains for the f irst 24 h of observation, and in dilp641 strain, for 48 h. Thus, we may conclude that dfoxo takes part in regulating the IIS pathway response to heat stress as well as the changes in lipids content caused by heat stress, and this regulation is mediated by dilp6. At the same time, the feeding behaviour of imago might be controlled by dfoxo and dilp6 under normal conditions, but not under heat stress.