Insulin/insulin-like Growth Factor Research Articles

Identification of functional rare coding variants in IGF-1 gene in humans with exceptional longevity.

Diminished signaling via insulin/insulin-like growth factor-1 (IGF-1) axis is associated with longevity in different model organisms. IGF-1 gene is highly conserved across species, with only few evolutionary changes identified in it. Despite its potential role in regulating life span, no coding variants in IGF-1 have been reported in human longevity cohorts to date. This study investigated the whole exome sequencing data from 2,487 individuals in a cohort of Ashkenazi Jewish centenarians, their offspring, and controls without familial longevity to identify functional IGF-1 coding variants. We identified two likely functional coding variants IGF-1 :p.Ile91Leu and IGF-1 :p.Ala118Thr in our longevity cohort. Notably, a centenarian specific novel variant IGF-1:p .Ile91Leu was located at the binding interface of IGF-1 - IGF-1R, whereas IGF-1 :p.Ala118Thr was significantly associated with lower circulating levels of IGF-1. We performed extended all-atom molecular dynamics simulations to evaluate the impact of Ile91Leu on stability, binding dynamics and energetics of IGF-1 bound to IGF-1R. The IGF-1 :p.Ile91Leu formed less stable interactions with IGF-1R's critical binding pocket residues and demonstrated lower binding affinity at the extracellular binding site compared to wild-type IGF-1. Our findings suggest that IGF-1 :p.Ile91Leu and IGF-1 :p.Ala118Thr variants attenuate IGF-1R activity by impairing IGF-1 binding and diminishing the circulatory levels of IGF-1, respectively. Consequently, diminished IGF-1 signaling resulting from these variants may contribute to exceptional longevity in humans.

7942 Evolution of Insulin, Insulin-like Growth Factor and Their Cognate Receptors in Vertebrates, Invertebrates and Viruses

Abstract Disclosure: M. Chrudinova: None. Y.D. Dogru: None. R. Huang: None. R. Reiners: None. P. De Meyts: None. J. DaCosta: None. E. Altindis: None. The insulin/insulin-like growth factor (IGF) signaling system is an evolutionarily conserved system and controls central processes including metabolism, cellular growth, proliferation, and differentiation in vertebrates. On the other hand, invertebrate insulin-like peptides (ILPs) regulate growth, stress responses, longevity and sex-related functions. In addition, we recently showed that six viruses possess viral insulin-like peptides (VILPs) that can bind to the receptors and stimulate post-receptor signaling. The evolution of these hormones and the origin of VILPs are not completely understood. Here, we collected vertebrate and invertebrate insulin, IGF and their cognate receptor sequences to analyze their evolutionary relations. We analyzed 177 vertebrate insulins, 119 vertebrate IGF-1s, 127 vertebrate IGF-2s, 197 invertebrate ILPs and 6 viral insulin/IGF-1 like peptides. We also analyzed 214 insulin receptor (IR), 160 IGF receptor (IGF1R) and 39 invertebrate receptor sequences to identify conservation and the evolutionary trajectory to reveal conserved motifs. Through phylogenetic analyses, we observed a separate branching of invertebrate ILPs and vertebrate insulins, IGF-1s and IGF-2s with notable exceptions including VILPs. IGF-1 and IGF-2 ligands were evolutionally better conserved compared to insulin ligands. Insulin C-peptide which is processed and cleaved was not well conserved compared to the functional A- and B-chain residues. In contrast, C-peptide of IGF-1 that plays an important role in receptor binding was very well conserved. IGF-1 C-domain showed higher variability in IGF1R binding residues compared to the A and B-domains, while residues important for binding of IGF-2 to IGF1R were well conserved. Insulin residues interacting with IR binding Site 1 were more conserved than those interacting with IR binding Site 2, while residues important for insulin dimerization and hexamerization residues are well conserved across species. We also showed that VILPs contain 14 amino acids that are conserved in insulin and IGFs, indicating their functional importance. Phylogenetic relationships of the receptor sequences suggest vertebrate IRs and IGF1Rs evolved from a common ancestor during early vertebrate evolution. Interestingly, receptor subunits revealed a closer relation of amphibian IR α-subunits to Mammalia IR α-subunits than Aves and Reptilians. The conservation rate of receptor residues essential for ligand-receptor interaction revealed that these residues are best conserved in the L1 domain for IR and IGF1R, with a higher rate of variation in other domains for both receptors. Taken together, our study provides a comprehensive analysis of insulin, IGFs, VILPs and their cognate receptors’ evolution, and opens new avenues to better understand the evolution, function, and structure relations of this complex signaling system. Presentation: 6/3/2024

Evaluating Fibroblast Growth Factor 21 (FGF21) Levels Post-Gastric Sleeve Surgery in Obese Patients.

Background and objectives Obesity is a major global health concern linked with increased risk of chronic diseases. This study aimed to assess the levels of fibroblast growth factor 21 (FGF21) insubjects with obesity after gastric sleeve surgery and explore its correlation with lipid and glycemic parameters. Methods This retrospective cohort study included 28 obese male subjects aged 25 to 50 years, undergoing gastric sleeve surgery. Plasma levels of FGF21 were measured by enzyme-linked immunosorbent assay (ELISA) before and six to 12 months after surgery. Other parameters including body mass index (BMI), fasting glucose, lipid profile, and insulin were also assessedand homeostatic model assessment (HOMA) was used to estimate insulin resistance. Results There was a significant increase in systemic FGF21 levels after surgery (45.12 vs. 126.16 pg/mL, p = 0.007). There was also a notable reduction in BMI (51.55 vs. 39.14, p < 0.001), insulin levels (20.06 vs. 8.85 mIU/L, p < 0.001), HOMA scores (6.94 to 2.49, p < 0.001), and glucose levels (7.33 vs. 6.08, p = 0.039). Lipid profile analysis post-surgery showed an increase in total cholesterol (4.38 vs. 5.09 mmol/L, p < 0.001) and high-density lipoprotein (HDL) (0.88 vs. 1.52 mmol/L, p < 0.001), with a decrease in triglycerides (1.75 vs. 1.01 mmol/L, p = 0.007). FGF21 positively correlated with growth hormone (GH), p = 0.0015, r = 0.59, and with insulin like growth factor 1 (IGF-1), p = 0.03, r = 0.431. Conclusion FGF21 levels were increased following gastric sleeve surgery in obese male patients and were positively correlated with growth hormone and insulin IGF-1. These findings provide insights into the metabolic alterations following bariatric surgery and highlight the potential role of FGF21 as an important molecule in obesity management and treatment.

Inhibition of a cyclic nucleotide-gated channel on neuronal cilia activates unfolded protein response in intestinal cells to promote longevity

Ciliary defects are linked to ciliopathies, but impairments in the sensory cilia of Caenorhabditis elegans neurons extend lifespan, a phenomenon with previously unclear mechanisms. Our study reveals that neuronal cilia defects trigger the unfolded protein response of the endoplasmic reticulum (UPR ER ) within intestinal cells, a process dependent on the insulin/insulin-like growth factor 1 (IGF-1) signaling transcription factor and the release of neuronal signaling molecules. While inhibiting UPR ER doesn’t alter the lifespan of wild-type worms, it normalizes the extended lifespan of ciliary mutants. Notably, deactivating the cyclic nucleotide-gated (CNG) channel TAX-4 on the ciliary membrane promotes lifespan extension through a UPR ER -dependent mechanism. Conversely, constitutive activation of TAX-4 attenuates intestinal UPR ER in ciliary mutants. Administering a CNG channel blocker to worm larvae activates intestinal UPR ER and increases adult longevity. These findings suggest that ciliary dysfunction in sensory neurons triggers intestinal UPR ER , contributing to lifespan extension and implying that transiently inhibiting ciliary channel activity may effectively prolong lifespan.

Association of cigarette smoking with cerebrospinal fluid biomarkers of insulin sensitivity and neurodegeneration.

Cigarette smoking increases both the risk for insulin resistance and amyloid-β (Aβ) aggregation, and impaired brain insulin/insulin-like growth factor 1 (IGF1) signaling might increase risk factors for Alzheimer's disease (AD). We aimed to investigate the association among cerebrospinal fluid (CSF) insulin sensitivity/IGF1, glucose/lactate, and Aβ42 and further explore whether insulin sensitivity contributed to the risk for AD in active smokers. In this cross-sectional study, levels of insulin, IGF1, and lactate/glucose of 75 active smokers and 78 nonsmokers in CSF were measured. Three polymorphisms regulating IGF1 were genotyped. Analysis of variance was used to compare differences of variables between groups. Partial correlation was performed to test the relationship between CSF biomarkers and smoking status. General linear models were applied to test the interaction of the effect of single nucleotide polymorphisms and cigarette smoking on CSF IGF1 levels. In the CSF from active smokers, IGF1 and lactate levels were significantly lower (p=.016 and p=.010, respectively), whereas Aβ42 (derived from our earlier research) and insulin levels were significantly higher (p<.001 and p=.022, respectively) as compared to the CSF from nonsmokers. The AG+GG genotype of rs6218 in active smokers had a significant effect on lower CSF IGF1 levels (p=.004) and lower CSF insulin levels in nonsmokers (p=.016). Cigarette smoking as the "at-risk" factor for AD might be due to lower cerebral insulin sensitivity in CSF, and the subjects with rs6218G allele seem to be more susceptible to the neurodegenerative risks for cigarette smoking.

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.

The Role of mRNA Quality Control in the Aging of Caenorhabditis elegans.

The proper maintenance of mRNA quality that is regulated by diverse surveillance pathways is essential for cellular homeostasis and is highly conserved among eukaryotes. Here, we review findings regarding the role of mRNA quality control in the aging and longevity of Caenorhabditis elegans, an outstanding model for aging research. We discuss the recently discovered functions of the proper regulation of nonsense-mediated mRNA decay, ribosome-associated quality control, and mRNA splicing in the aging of C. elegans. We describe how mRNA quality control contributes to longevity conferred by various regimens, including inhibition of insulin/insulin-like growth factor 1 (IGF-1) signaling, dietary restriction, and reduced mechanistic target of rapamycin signaling. This review provides valuable information regarding the relationship between the mRNA quality control and aging in C. elegans, which may lead to insights into healthy longevity in complex organisms, including humans.

APPA Increases Lifespan and Stress Resistance via Lipid Metabolism and Insulin/IGF-1 Signal Pathway in Caenorhabditis elegans.

Animal studies have proven that 1-acetyl-5-phenyl-1H-pyrrol-3-yl acetate (APPA) is a powerful antioxidant as a novel aldose reductase inhibitor independently synthesized by our laboratory; however, there is no current information on APPA's anti-aging mechanism. Therefore, this study examined the impact and mechanism of APPA's anti-aging and anti-oxidation capacity using the Caenorhabditis elegans model. The results demonstrated that APPA increases C. elegans' longevity without affecting the typical metabolism of Escherichia coli OP50 (OP50). APPA also had a non-toxic effect on C. elegans, increased locomotor ability, decreased the levels of reactive oxygen species, lipofuscin, and fat, and increased anti-stress capacity. QRT-PCR analysis further revealed that APPA upregulated the expression of antioxidant genes, including sod-3, gst-4, and hsp-16.2, and the critical downstream transcription factors, daf-16, skn-1, and hsf-1 of the insulin/insulin-like growth factor (IGF) receptor, daf-2. In addition, fat-6 and nhr-80 were upregulated. However, the APPA's life-prolonging effects were absent on the daf-2, daf-16, skn-1, and hsf-1 mutants implying that the APPA's life-prolonging mechanism depends on the insulin/IGF-1 signaling system. The transcriptome sequencing also revealed that the mitochondrial route was also strongly associated with the APPA life extension, consistent with mev-1 and isp-1 mutant life assays. These findings aid in the investigation of APPA's longevity extension mechanism.

Glucose-lowering effects of a synbiotic combination containing Pediococcus acidilactici in C. elegans and mice

Aims/hypothesisModulation of gut microbiota has emerged as a promising strategy to treat or prevent the development of different metabolic diseases, including type 2 diabetes and obesity. Previous data from our group suggest that the strain Pediococcus acidilactici CECT9879 (pA1c) could be an effective probiotic for regulating glucose metabolism. Hence, the objectives of this study were to verify the effectiveness of pA1c on glycaemic regulation in diet-induced obese mice and to evaluate whether the combination of pA1c with other normoglycaemic ingredients, such as chromium picolinate (PC) and oat β-glucans (BGC), could increase the efficacy of this probiotic on the regulation of glucose and lipid metabolism.MethodsCaenorhabditis elegans was used as a screening model to describe the potential synbiotic activities, together with the underlying mechanisms of action. In addition, 4-week-old male C57BL/6J mice were fed with a high-fat/high-sucrose diet (HFS) for 6 weeks to induce hyperglycaemia and obesity. Mice were then divided into eight groups (n=12 mice/group) according to dietary supplementation: control-diet group; HFS group; pA1c group (1010 colony-forming units/day); PC; BGC; pA1c+PC+BGC; pA1c+PC; and pA1c+BGC. Supplementations were maintained for 10 weeks. Fasting blood glucose was determined and an IPGTT was performed prior to euthanasia. Fat depots, liver and other organs were weighed, and serum biochemical variables were analysed. Gene expression analyses were conducted by real-time quantitative PCR. Sequencing of the V3–V4 region of the 16S rRNA gene from faecal samples of each group was performed, and differential abundance for family, genera and species was analysed by ALDEx2R package.ResultsSupplementation with the synbiotic (pA1c+PC+BGC) counteracted the effect of the high glucose by modulating the insulin–IGF-1 signalling pathway in C. elegans, through the reversal of the glucose nuclear localisation of daf-16. In diet-induced obese mice, all groups supplemented with the probiotic significantly ameliorated glucose tolerance after an IPGTT, demonstrating the glycaemia-regulating effect of pA1c. Further, mice supplemented with pA1c+PC+BGC exhibited lower fasting blood glucose, a reduced proportion of visceral adiposity and a higher proportion of muscle tissue, together with an improvement in the brown adipose tissue in comparison with the HFS group. Besides, the effect of the HFS diet on steatosis and liver damage was normalised by the synbiotic. Gene expression analyses demonstrated that the synbiotic activity was mediated not only by modulation of the insulin–IGF-1 signalling pathway, through the overexpression of GLUT-1 and GLUT-4 mediators, but also by a decreased expression of proinflammatory cytokines such as monocyte chemotactic protein-1. 16S metagenomics demonstrated that the synbiotic combinations allowed an increase in the concentration of P. acidilactici, together with improvements in the intestinal microbiota such as a reduction in Prevotella and an increase in Akkermansia muciniphila.Conclusions/interpretationOur data suggest that the combination of pA1c with PC and BGC could be a potential synbiotic for blood glucose regulation and may help to fight insulin resistance, diabetes and obesity.Graphical

Repositioning of Anti-Diabetic Drugs against Dementia: Insight from Molecular Perspectives to Clinical Trials.

Insulin resistance as a hallmark of type 2 DM (T2DM) plays a role in dementia by promoting pathological lesions or enhancing the vulnerability of the brain. Numerous studies related to insulin/insulin-like growth factor 1 (IGF-1) signaling are linked with various types of dementia. Brain insulin resistance in dementia is linked to disturbances in Aβ production and clearance, Tau hyperphosphorylation, microglial activation causing increased neuroinflammation, and the breakdown of tight junctions in the blood-brain barrier (BBB). These mechanisms have been studied primarily in Alzheimer's disease (AD), but research on other forms of dementia like vascular dementia (VaD), Lewy body dementia (LBD), and frontotemporal dementia (FTD) has also explored overlapping mechanisms. Researchers are currently trying to repurpose anti-diabetic drugs to treat dementia, which are dominated by insulin sensitizers and insulin substrates. Although it seems promising and feasible, none of the trials have succeeded in ameliorating cognitive decline in late-onset dementia. We highlight the possibility of repositioning anti-diabetic drugs as a strategy for dementia therapy by reflecting on current and previous clinical trials. We also describe the molecular perspectives of various types of dementia through the insulin/IGF-1 signaling pathway.

Ethyl caffeate attefnuates Aβ-induced toxicity in Caenorhabditis elegans AD models via the insulin/insulin-like growth factor-1 signaling pathway

The pathogenesis of Alzheimer's disease (AD), a multifactorial progressive neurodegenerative disease associated with aging, is unclear. Ethyl caffeate is a plant polyphenol that has been reported to have neuroprotective effects, but the mechanisms by which it acts are unclear. In this study, for the first time, we investigated the molecular mechanism of its anti-AD properties using the Caernorhabditis elegans model. The results of our experiments showed that ethyl caffeate delayed the paralysis symptoms of CL4176 to a different extent and reduced the exogenous 5-hydroxytryptophan-induced paralysis phenotype. Further studies revealed that ethyl caffeate lowered Aβ plaques and depressed the expression of Aβ monomers and oligomers, but did not influence the mRNA levels of Aβ. Moreover, it was able to bring paraquat-induced ROS levels down to near-standard conditions. Real-time quantitative PCR experiment showed a significant upregulation of the transcript abundance of daf-16, skn-1 and hsf-1, key factors associated with the insulin/insulin-like growth factor 1 (IGF-1) signaling pathway (IIS), and their downstream genes sod-3, gst-4 and hsp-16.2. It was further shown that ethyl caffeate activated the translocation of DAF-16 and SKN-1 from the cytoplasm to the nucleus and enhanced the expression of sod-3::GFP, gst-4::GFP and hsp-16.2::GFP in transgenic nematodes. This meant that the protection against Aβ toxicity by ethyl caffeate may be partly through the IIS signaling pathway. In addition, ethyl caffeate suppressed the aggregation of polyglutamine proteins in AM141, which indicated a potential protective effect against neurodegenerative diseases based on abnormal folding and aggregation of amyloid proteins. Taken together, ethyl caffeate is expected to develop as a potential drug for the management of AD.

Starvation-induced changes in somatic insulin/IGF-1R signaling drive metabolic programming across generations

Exposure to adverse nutritional and metabolic environments during critical periods of development can exert long-lasting effects on health outcomes of an individual and its descendants. Although such metabolic programming has been observed in multiple species and in response to distinct nutritional stressors, conclusive insights into signaling pathways and mechanisms responsible for initiating, mediating, and manifesting changes to metabolism and behavior across generations remain scarce. By using a starvation paradigm in Caenorhabditis elegans, we show that starvation-induced changes in dauer formation-16/forkhead box transcription factor class O (DAF-16/FoxO) activity, the main downstream target of insulin/insulin-like growth factor 1 (IGF-1) receptor signaling, are responsible for metabolic programming phenotypes. Tissue-specific depletion of DAF-16/FoxO during distinct developmental time points demonstrates that DAF-16/FoxO acts in somatic tissues, but not directly in the germline, to both initiate and manifest metabolic programming. In conclusion, our study deciphers multifaceted and critical roles of highly conserved insulin/IGF-1 receptor signaling in determining health outcomes and behavior across generations.

Inceptor correlates with markers of prostate cancer progression and modulates insulin/IGF1 signaling and cancer cell migration

ObjectiveThe insulin/insulin-like growth factor 1 (IGF1) pathway is emerging as a crucial component of prostate cancer progression. Therefore, we investigated the role of the novel insulin/IGF1 signaling modulator inceptor in prostate cancer. MethodsWe analyzed the expression of inceptor in human samples of benign prostate epithelium and prostate cancer. Further, we performed signaling and functional assays using prostate cancer cell lines. ResultsWe found that inceptor was expressed in human benign and malignant prostate tissue and its expression positively correlated with various genes of interest, including genes involved in androgen signaling. In vitro, total levels of inceptor were increased upon androgen deprivation and correlated with high levels of androgen receptor in the nucleus. Inceptor overexpression was associated with increased cell migration, altered IGF1R trafficking and higher IGF1R activation. ConclusionsOur in vitro results showed that inceptor expression was associated with androgen status, increased migration, and IGF1R signaling. In human samples, inceptor expression was significantly correlated with markers of prostate cancer progression. Taken together, these data provide a basis for investigation of inceptor in the context of prostate cancer.

Regulation of germline proteostasis by HSF1 and insulin/IGF-1 signaling.

Protein homeostasis (proteostasis) is essential for cellular function and organismal health and requires the concerted actions of protein synthesis, folding, transport, and turnover. In sexually reproducing organisms, the immortal germline lineage passes genetic information across generations. Accumulating evidence indicates the importance of proteome integrity for germ cells as genome stability. As gametogenesis involves very active protein synthesis and is highly energy-demanding, it has unique requirements for proteostasis regulation and is sensitive to stress and nutrient availability. The heat shock factor 1 (HSF1), a key transcriptional regulator of cellular response to cytosolic and nuclear protein misfolding has evolutionarily conserved roles in germline development. Similarly, insulin/insulin-like growth factor-1 (IGF-1) signaling, a major nutrient-sensing pathway, impacts many aspects of gametogenesis. Here, we focus on HSF1 and IIS to review insights into their roles in germline proteostasis and discuss the implications on gamete quality control during stress and aging.

Isolation of a novel missense mutation in insulin receptor as a spontaneous revertant in ImpL2 mutants in Drosophila.

Evolutionarily conserved insulin/insulin-like growth factor (IGF) signaling (IIS) correlates nutrient levels to metabolism and growth, thereby playing crucial roles in development and adult fitness. In the fruit fly Drosophila, ImpL2, an ortholog of IGFBP7, binds to and inhibits the function of Drosophila insulin-like peptides. In this study, we isolated a temperature-sensitive mutation in the insulin receptor (InR) gene as a spontaneous revertant in ImpL2 null mutants. The p.Y902C missense mutation is located at the functionally conserved amino acid residue of the first fibronectin type III domain of InR. The hypomorphic InR mutant animals showed a temperature-dependent reduction in IIS and body size. The mutant animals also exhibited metabolic defects, such as increased triglyceride and carbohydrate levels. Metabolomic analysis further revealed that defects in InR caused dysregulation of amino acid and ribonucleotide metabolism. We also observed that InR mutant females produced tiny irregular-shaped embryos with reduced fecundity. In summary, this novel allele of InR is a valuable tool for the Drosophila genetic model of insulin resistance and type 2 diabetes.

Cremastra appendiculata polysaccharides improve stress resistance and prolong the lifespan of Caenorhabditis elegans via daf-16 in the insulin signaling pathway

Cremastra appendiculata polysaccharide (CAP) exhibits potential anti-aging and stress resistance effects. In this study, we investigated the structure, antioxidant properties, and mechanism of action of CAP in Caenorhabditis elegans. The results showed that CAP primarily comprises mannose and glucose and exerts antioxidant activity in vitro. In vivo, CAP prolonged the lifespan of C. elegans in a concentration-dependent manner, with 2.0 mg/mL CAP prolonging the lifespan by 39.97 %. Compared with the control, the activities of superoxide dismutase (SOD) and catalase (CAT) antioxidant enzymes increased by 46 % and 57 %, respectively. However, the reactive oxygen species (ROS) and malondialdehyde (MDA) contents decreased by 38 % and 19.92 %, respectively, at the same CAP concentration, oxidative and heat stress resistance increased. The target genes of the insulin/insulin-like growth factor (IGF) signaling pathway, daf-16, sod-3, ctl-1, and hsp-16.2, were activated by CAP; their mRNA expression levels were upregulated by 7.23 %, 69.78 %, 43.62 %, and 58.62 %, respectively. A transgenic worm assay indicated that CAP regulates the lifespan of C. elegans through daf-16. These results suggest that CAP improves stress resistance and prolongs the lifespan of C. elegans through daf-16 in the insulin/IGF signaling pathway.

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.

Insulin/IGF-dependent Wnt signaling promotes formation of germline tumors and other developmental abnormalities following early-life starvation in Caenorhabditis elegans.

The Developmental Origins of Health and Disease hypothesis postulates that early-life stressors can predispose people to disease later in life. In the roundworm Caenorhabditis elegans, prolonged early-life starvation causes germline tumors, uterine masses, and other gonad abnormalities to develop in well-fed adults. Reduction of insulin/insulin-like growth factor (IGF) signaling (IIS) during larval development suppresses these starvation-induced abnormalities. However, molecular mechanisms at play in formation and suppression of starvation-induced abnormalities are unclear. Here we describe mechanisms through which early-life starvation and reduced IIS affect starvation-induced abnormalities. Transcriptome sequencing revealed that expression of genes in the Wnt signaling pathway is upregulated in adults starved as young larvae, and that knockdown of the insulin/IGF receptor daf-2/InsR decreases their expression. Reduction of Wnt signaling through RNAi or mutation reduced starvation-induced abnormalities, and hyperactivation of Wnt signaling produced gonad abnormalities in worms that had not been starved. Genetic and reporter-gene analyses suggest that Wnt signaling acts downstream of IIS in the soma to cell-nonautonomously promote germline hyperproliferation. In summary, this work reveals that IIS-dependent transcriptional regulation of Wnt signaling promotes starvation-induced gonad abnormalities, illuminating signaling mechanisms that contribute to adult pathology following early-life starvation.

Further Extension of Lifespan by Unc-43/CaMKII and Egl-8/PLCβ Mutations in Germline-Deficient Caenorhabditis elegans.

Reduction of insulin/insulin-like growth factor 1 (IGF1) signaling (IIS) promotes longevity across species. In the nematode Caenorhabditis elegans, ablation of germline stem cells (GSCs) and activity changes of the conserved signaling mediators unc-43/CaMKII (calcium/calmodulin-dependent kinase type II) and egl-8/PLCβ (phospholipase Cβ) also increase lifespan. Like IIS, these pathways depend on the conserved transcription factor daf-16/FOXO for lifespan extension, but how they functionally interact is unknown. Here, we show that altered unc-43/egl-8 activity further increases the lifespan of long-lived GSC-deficient worms, but not of worms that are long-lived due to a strong reduction-of-function mutation in the insulin/IGF1-like receptor daf-2. Additionally, we provide evidence for unc-43 and, to a lesser extent, egl-8 modulating the expression of certain collagen genes, which were reported to be dispensable for longevity of these particular daf-2 mutant worms, but not for other forms of longevity. Together, these results provide new insights into the conditions and potential mechanisms by which CaMKII- and PLCβ-signals modulate C. elegans lifespan.

Insulin/IGF signaling regulates presynaptic glutamate release in aversive olfactory learning.

Insulin/insulin-like growth factor (IGF) receptor signaling (IIS) supports context-dependent learning in vertebrates and invertebrates. Here, we identify cell-specific mechanisms of IIS that integrate sensory information with food context to drive synaptic plasticity and learning. In the nematode Caenorhabditis elegans, pairing food deprivation with an odor such as butanone suppresses attraction to that odor. We find that aversive olfactory learning requires the insulin receptor substrate (IRS) protein IST-1 and atypical signaling through the insulin/IGF-1 receptor DAF-2. Cell-specific knockout and rescue demonstrate that DAF-2 acts in the AWCON sensory neuron, which detects butanone, and that learning preferentially depends upon the axonally localized DAF-2c isoform. Acute food deprivation increases DAF-2 levels in AWCON post-transcriptionally through an insulin- and insulin receptor substrate-1 (ist-1)-dependent process. Aversive learning alters the synaptic output of AWCON by suppressing odor-regulated glutamate release in wild-type animals, but not in ist-1 mutants, suggesting that axonal insulin signaling regulates synaptic transmission to support aversive memory.