JAK/STAT mediated insulin resistance in muscles is essential for effective immune response.

BACKGROUND: The metabolically demanding nature of immune response requires nutrients to be preferentially directed towards the immune system at the expense of peripheral tissues. We study the mechanisms by which this metabolic reprograming occurs using the parasitoid infection of Drosophila larvae. To overcome such an immune challenge hemocytes differentiate into lamellocytes, which encapsulate and melanize the parasitoid egg. Hemocytes acquire the energy for this process by expressing JAK/STAT ligands upd2 and upd3, which activates JAK/STAT signaling in muscles and redirects carbohydrates away from muscles in favor of immune cells. METHODS: Immune response of Drosophila larvae was induced by parasitoid wasp infestation. Carbohydrate levels, larval locomotion and gene expression of key proteins were compared between control and infected animals. Efficacy of lamellocyte production and resistance to wasp infection was observed for RNAi and mutant animals. RESULTS: Absence of upd/JAK/STAT signaling leads to an impaired immune response and increased mortality. We demonstrate how JAK/STAT signaling in muscles leads to suppression of insulin signaling through activation of ImpL2, the inhibitor of Drosophila insulin like peptides. CONCLUSIONS: Our findings reveal cross-talk between immune cells and muscles mediates a metabolic shift, redirecting carbohydrates towards immune cells. We emphasize the crucial function of muscles during immune response and show the benefits of insulin resistance as an adaptive mechanism that is necessary for survival.

Role of the Insulin-like Growth Factor System in Neurodegenerative Disease.

The insulin-like growth factor (IGF) system has paracrine and endocrine roles in the central nervous system. There is evidence that IGF signalling pathways have roles in the pathophysiology of neurodegenerative disease. This review focusses on Alzheimer's disease and Parkinson's disease, the two most common neurodegenerative disorders that are increasing in prevalence globally in relation to the aging population and the increasing prevalence of obesity and type 2 diabetes. Rodent models used in the study of the molecular pathways involved in neurodegeneration are described. However, currently, no animal model fully replicates these diseases. Mice with triple mutations in APP, PSEN and MAPT show promise as models for the testing of novel Alzheimer's therapies. While a causal relationship is not proven, the fact that age, obesity and T2D are risk factors in both strengthens the case for the involvement of the IGF system in these disorders. The IGF system is an attractive target for new approaches to management; however, there are gaps in our understanding that first need to be addressed. These include a focus beyond IGF-I on other members of the IGF system, including IGF-II, IGF-binding proteins and the type 2 IGF receptor.

Mitochondrial fusion and altered beta-oxidation drive muscle wasting in a Drosophila cachexia model.

Cancer cachexia is a tumour-induced wasting syndrome, characterised by extreme loss of skeletal muscle. Defective mitochondria can contribute to muscle wasting; however, the underlying mechanisms remain unclear. Using a Drosophila larval model of cancer cachexia, we observed enlarged and dysfunctional muscle mitochondria. Morphological changes were accompanied by upregulation of beta-oxidation proteins and depletion of muscle glycogen and lipid stores. Muscle lipid stores were also decreased in Colon-26 adenocarcinoma mouse muscle samples, and expression of the beta-oxidation gene CPT1A was negatively associated with muscle quality in cachectic patients. Mechanistically, mitochondrial defects result from reduced muscle insulin signalling, downstream of tumour-secreted insulin growth factor binding protein (IGFBP) homologue ImpL2. Strikingly, muscle-specific inhibition of Forkhead box O (FOXO), mitochondrial fusion, or beta-oxidation in tumour-bearing animals preserved muscle integrity. Finally, dietary supplementation with nicotinamide or lipids, improved muscle health in tumour-bearing animals. Overall, our work demonstrates that muscle FOXO, mitochondria dynamics/beta-oxidation and lipid utilisation are key regulators of muscle wasting in cancer cachexia.

Antisense Oligonucleotide-Mediated Downregulation of IGFBPs Enhances IGF-1 Signaling.

Insulin-like growth factor-1 (IGF-1) has been considered as a therapeutic agent for muscle wasting conditions including Duchenne muscular dystrophy as it stimulates muscle regeneration, growth and function. Several preclinical and clinical studies have been conducted to show the therapeutic potential of IGF-1, however, delivery issues, short half-life and isoform complexity have impose challenges. Antisense oligonucleotides (AONs) are able to downregulate target proteins by interfering with their transcripts. Here, we investigated the feasibility of enhancing IGF-1 signaling by downregulation of IGF-binding proteins. We observed that out of frame exon skipping of Igfbp1 and Igfbp3 downregulated their protein expression, which increased Akt phosphorylation on the downstream IGF-1 signaling in vitro. 3'RNA sequencing analysis revealed the related transcriptome in C2C12 cells in response to IGFBP3 downregulation. The AONs did however not induce any exon skipping or protein knockdown in mdx mice after 6 weeks of systemic treatment. We conclude that IGFBP downregulation could be a good strategy to increase IGF-1 signaling but alternative tools are needed for efficient delivery and knockdown in vivo.

Role of the Insulin-like Growth Factor (IGF) Axis in Diseases.

The insulin-like growth factor axis is a multifaceted, complex system that comprises two ligands, IGF-I and IGF-II, receptors (IGF-1R, IGF-IIR, insulin receptor isoforms IR-A and B, and hybrid receptors) six high affinity IGF-binding proteins (IGFBPs 1-6), and IGFBP proteases [...].

Insulin-like growth factor (IGF) performance in ovarian function and applications in reproductive biotechnologies.

The role of the insulin-like growth factor (IGF) system has attracted close attention. The activity of IGF binding proteins (IGFBPs) within the ovary has not been fully elucidated to date. These proteins bind to IGF with an equal, or greater, affinity than to the IGF1 receptor, thus being in the main position to regulate IGF signalling, in addition to extending the half-life of IGFs within the bloodstream and promoting IGF storage in specific tissue niches. IGF1 has an important part in cell proliferation, differentiation and apoptosis. Considering the importance of IGFs in oocyte maturation, this review sought to elucidate aspects including: IGF production mechanisms; constituent members of their family and their respective functions; the role that these factors play during folliculogenesis, together with their functions during oocyte maturation and apoptosis, and their performance during luteal development. This review also explores the role of IGFs in biotechnological applications, focusing specifically on animal genetic gain.

IGFBPL1 inhibits macrophage lipid accumulation by enhancing the activation of IGR1R/LXRα/ABCG1 pathway.

Lipid accumulation in macrophages plays an important role in atherosclerosis and is the major cause of atherosclerotic cardiovascular disease. Reducing lipid accumulation in macrophages is an effective therapeutic target for atherosclerosis. Insulin-like growth factor 1 (IGF-1) exerts the anti-atherosclerotic effects by inhibiting lipid accumulation in macrophages. Furthermore, almost all circulating IGF-1 combines with IGF binding proteins (IGFBPs) to activate or inhibit the IGF signaling. However, the mechanism of IGFBPs in macrophage lipid accumulation is still unknown. GEO database analysis showed that among IGFBPS family members, IGFBPL1 has the largest expression change in unstable plaque. We found that IGFBPL1 was decreased in lipid-laden THP-1 macrophages. Through oil red O staining, NBD-cholesterol efflux, liver X receptor α (LXRα) transcription factor and IGR-1 receptor blocking experiments, our results showed that IGFBPL1 inhibits lipid accumulation in THP-1 macrophages through promoting ABCG1-meditated cholesterol efflux, and IGFBPL1 regulates ABCG1 expression and macrophage lipid metabolism through IGF-1R/LXRα pathway. Our results provide a theoretical basis of IGFBPL1 in the alternative or adjunct treatment options for atherosclerosis by reducing lipid accumulation in macrophages.

Macrophage-derived insulin antagonist ImpL2 induces lipoprotein mobilization upon bacterial infection.

The immune response is an energy-demanding process that must be coordinated with systemic metabolic changes redirecting nutrients from stores to the immune system. Although this interplay is fundamental for the function of the immune system, the underlying mechanisms remain elusive. Our data show that the pro-inflammatory polarization of Drosophila macrophages is coupled to the production of the insulin antagonist ImpL2 through the activity of the transcription factor HIF1α. ImpL2 production, reflecting nutritional demands of activated macrophages, subsequently impairs insulin signaling in the fat body, thereby triggering FOXO-driven mobilization of lipoproteins. This metabolic adaptation is fundamental for the function of the immune system and an individual's resistance to infection. We demonstrated that analogically to Drosophila, mammalian immune-activated macrophages produce ImpL2 homolog IGFBP7 in a HIF1α-dependent manner and that enhanced IGFBP7 production by these cells induces mobilization of lipoproteins from hepatocytes. Hence, the production of ImpL2/IGFBP7 by macrophages represents an evolutionarily conserved mechanism by which macrophages alleviate insulin signaling in the central metabolic organ to secure nutrients necessary for their function upon bacterial infection.

IGFBPL1 is a master driver of microglia homeostasis and resolution of neuroinflammation in glaucoma and brain tauopathy.

Microglia shift toward an inflammatory phenotype during aging that is thought to exacerbate age-related neurodegeneration. The molecular and cellular signals that resolve neuroinflammation post-injury are largely undefined. Here, we exploit systems genetics methods based on the extended BXD murine reference family and identify IGFBPL1 as an upstream cis-regulator of microglia-specific genes to switch off inflammation. IGFBPL1 is expressed by mouse and human microglia, and higher levels of its expression resolve lipopolysaccharide-induced neuroinflammation by resetting the transcriptome signature back to a homeostatic state via IGF1R signaling. Conversely, IGFBPL1 deficiency or selective deletion of IGF1R in microglia shifts these cells to an inflammatory landscape and induces early manifestation of brain tauopathy and retinal neurodegeneration. Therapeutic administration of IGFBPL1 drives pro-homeostatic microglia and prevents glaucomatous neurodegeneration and vision loss in mice. These results identify IGFBPL1 as a master driver of the counter-inflammatory microglial modulator that presents an endogenous resolution of neuroinflammation to prevent neurodegeneration in eye and brain.

IGFBP1 Sustains Cell Survival during Spatially-Confined Migration and Promotes Tumor Metastasis.

Cell migration is a pivotal step in metastatic process, which requires cancer cells to navigate a complex spatially-confined environment, including tracks within blood vessels and in the vasculature of target organs. Here it is shown that during spatially-confined migration, the expression of insulin-like growth factor-binding protein 1 (IGFBP1) is upregulated in tumor cells. Secreted IGFBP1 inhibits AKT1-mediated phosphorylation of mitochondrial superoxide dismutase (SOD2) serine (S) 27 and enhances SOD2 activity. Enhanced SOD2 attenuates mitochondrial reactive oxygen species (ROS) accumulation in confined cells, which supports tumor cell survival in blood vessels of lung tissues, thereby accelerating tumor metastasis in mice. The levels of blood IGFBP1 correlate with metastatic recurrence of lung cancer patients. This finding reveals a unique mechanism by which IGFBP1 sustains cell survival during confined migration by enhancing mitochondrial ROS detoxification, thereby promoting tumor metastasis.

Pan-cancer analysis of oncogenic role of insulin-like growth factor-binding proteins and validation in ovarian cancer.

BACKGROUND: Numerous studies have shown that the insulin-like growth factor (IGF) pathway is highly associated with tumor initial and progression in several tumors. However, compared with IGF1/1R and IGF2/2R, insufficient studies have focused on IGF-binding proteins (IGFBPs). METHODS: The GDC TCGA and GTEx data of 33 cancers, TCGA pan-cancer immune phenotypes, tumor mutation burdens, and the copy number alterations of IGFBPs were extracted. Next, the prognostic value of IGFBPs was analyzed based on a univariate Cox analysis. Additionally, the ESTIMATE algorithm was used to calculate stromal and immune scores and tumor purity, and the CIBERSORT algorithm was used to estimate tumor-infiltrating immunocyte levels. Ultimately, the correlation between IGFBP expression and cancer hallmark pathways was estimated with a Spearman analysis. RESULTS: The expression of IGFBPs was differentially expressed and correlated with prognosis in specific cancers. IGFBPs may operate as biological markers for carcinogenesis and progression and as prognostic biomarkers. Additionally, IGFBP5 has been proved that promotes the invasion and migration of ovarian cancer. CONCLUSIONS: In general, IGFBPs can serve as predictable biomarkers and potential therapeutic targets for specific tumors. Our results could provide underlying targets for the design of laboratory experiments to elucidate the mechanism of IGFBPs in cancers and identify IGFBP5 as a prognostic factor in ovarian cancers.

Development of a time-resolved fluoroimmunoassay for salmonid insulin-like growth factor binding protein-2b.

Insulin-like growth factor (IGF)-1 promotes the growth of vertebrates, and its binding proteins (IGFBPs) regulate the activity of circulating IGF-1. Three IGFBPs, IGFBP-2b, -1a, and -1b, were consistently detected in the circulatory system of salmonids. IGFBP-2b is thought to be the main carrier of IGFs and promoter of IGF-1-mediated growth in salmonids. Currently, there are no immunoassays for detecting IGFBP-2b. In this study, we developed a time-resolved fluoroimmunoassay (TR-FIA) for IGFBP-2b detection in salmonid fishes. To establish TR-FIA, we produced two recombinant trout (rt) IGFBP-2bs expressed, one with thioredoxin (Trx) and a histidine (His) tag, and the other with His-tag only. We labeled both recombinant proteins with europium (Eu). Only Eu-Trx.His.rtIGFBP-2b cross-reacted with anti-IGFBP-2b, and the addition of increasing amounts of Trx.His.rtIGFBP-2b replaced the binding, indicating its utility as a tracer and assay standard. The addition of unlabeled salmon IGF-1 did not affect the binding of the standard or sample. Serial dilution curves of sera from rainbow trout, Chinook salmon, and chum salmon were parallel to those of the standard. The assay range (ED80-ED20) of the TR-FIA was 60.4 to 251.3 ng/ml, and its minimum detection limit of this assay was 21 ng/ml. The intra- and inter-assay coefficients of variation were 5.68% and 5.65%, respectively. Circulating IGFBP-2b levels in fed rainbow trout were higher than those in fasted fish and were correlated with individual growth rates. This TR-FIA is useful for further exploring the physiological responses of circulating IGFBP-2b and evaluating the growth status of salmonids.

Expression characteristics and their functional role of IGFBP gene family in pan-cancer.

BACKGROUND: Insulin-like growth factor binding proteins (IGFBPs) are critical regulators of the biological activities of insulin-like growth factors. The IGFBP family plays diverse roles in different types of cancer, which we still lack comprehensive and pleiotropic understandings so far. METHODS: Multi-source and multi-dimensional data, extracted from The Cancer Genome Atlas (TCGA), Oncomine, Cancer Cell Line Encyclopedia (CCLE), and the Human Protein Atlas (HPA) was used for bioinformatics analysis by R language. Immunohistochemistry and qRT-PCR were performed to validate the results of the database analysis results. Bibliometrics and literature review were used for summarizing the research progress of IGFBPs in the field of tumor. RESULTS: The members of IGFBP gene family are differentially expressed in various cancer types. IGFBPs expression can affect prognosis of different cancers. The expression of IGFBPs expression is associated with multiple signal transduction pathways. The expression of IGFBPs is significantly correlated with tumor mutational burden, microsatellite instability, tumor stemness and tumor immune microenvironment. The qRT-PCR experiments verified the lower expression of IGFBP2 and IGFBP6 in gastric cancer and the lower expression of IGFBP6 in colorectal cancer. Immunohistochemistry validated a marked downregulation of IGFBP2 protein in gastric cancer tissues. The keywords co-occurrence analysis of IGFBP related publications in cancer showed relative research have been more concentrating on the potential of IGFBPs as tumor diagnostic and prognostic markers and developing cancer therapies. CONCLUSIONS: These findings provide frontier trend of IGFBPs related research and new clues for identifying novel therapeutic targets for various cancers.

IGF-Binding Proteins and Their Proteolysis as a Mechanism of Regulated IGF Release in the Nervous Tissue.

Insulin-like growth factors 1 and 2 (IGF-1 and IGF-2) play a key role in the maintenance of the nervous tissue viability. IGF-1 and IGF-2 exhibit the neuroprotective effects by stimulating migration and proliferation of nervous cells, activating cellular metabolism, inducing regeneration of damaged cells, and regulating various stages of prenatal and postnatal development of the nervous system. The availability of IGFs for the cells is controlled via their interaction with the IGF-binding proteins (IGFBPs) that inhibit their activity. On the contrary, the cleavage of IGFBPs by specific proteases leads to the IGF release and activation of its cellular effects. The viability of neurons in the nervous tissue is controlled by a complex system of trophic factors secreted by auxiliary glial cells. The main source of IGF for the neurons are astrocytes. IGFs can accumulate as an extracellular free ligand near the neuronal membranes as a result of proteolytic degradation of IGFBPs by proteases secreted by astrocytes. This mechanism promotes interaction of IGFs with their genuine receptors and triggers intracellular signaling cascades. Therefore, the release of IGF by proteolytic cleavage of IGFBPs is an important mechanism of neuronal protection. This review summarizes the published data on the role of IGFs and IGFBPs as the key players in the neuroprotective regulation with a special focus on the specific proteolysis of IGFBPs as a mechanism for the regulation of IGF bioavailability and viability of neurons.

Signaling Pathways of the Insulin-like Growth Factor Binding Proteins.

The 6 high-affinity insulin-like growth factor binding proteins (IGFBPs) are multifunctional proteins that modulate cell signaling through multiple pathways. Their canonical function at the cellular level is to impede access of insulin-like growth factor (IGF)-1 and IGF-2 to their principal receptor IGF1R, but IGFBPs can also inhibit, or sometimes enhance, IGF1R signaling either through their own post-translational modifications, such as phosphorylation or limited proteolysis, or by their interactions with other regulatory proteins. Beyond the regulation of IGF1R activity, IGFBPs have been shown to modulate cell survival, migration, metabolism, and other functions through mechanisms that do not appear to involve the IGF-IGF1R system. This is achieved by interacting directly or functionally with integrins, transforming growth factor ß family receptors, and other cell-surface proteins as well as intracellular ligands that are intermediates in a wide range of pathways. Within the nucleus, IGFBPs can regulate the diverse range of functions of class II nuclear hormone receptors and have roles in both cell senescence and DNA damage repair by the nonhomologous end-joining pathway, thus potentially modifying the efficacy of certain cancer therapeutics. They also modulate some immune functions and may have a role in autoimmune conditions such as rheumatoid arthritis. IGFBPs have been proposed as attractive therapeutic targets, but their ubiquity in the circulation and at the cellular level raises many challenges. By understanding the diversity of regulatory pathways with which IGFBPs interact, there may still be therapeutic opportunities based on modulation of IGFBP-dependent signaling.

Potent antitumor effects of the conditioned medium of bone marrow-derived mesenchymal stem cells via IGFBP-4.

Cell transfer therapy using mesenchymal stem cells (MSCs) has pronounced therapeutic potential, but concerns remain about immune rejection, emboli formation, and promotion of tumor progression. Because the mode of action of MSCs highly relies on their paracrine effects through secretion of bioactive molecules, cell-free therapy using the conditioned medium (CM) of MSCs is an attractive option. However, the effects of MSC-CM on tumor progression have not been fully elucidated. Herein, we addressed this issue and investigated the possible underlying molecular mechanisms. The CM of MSCs derived from human bone marrow greatly inhibited the in vitro growth of several human tumor cell lines and the in vivo growth of the SCCVII murine squamous cell carcinoma cell line with reduced neovascularization. Exosomes in the MSC-CM were only partially involved in the inhibitory effects. The CM contained a variety of cytokines including insulin-like growth factor binding proteins (IGFBPs). Among them, IGFBP-4 greatly inhibited the in vitro growth of these tumors and angiogenesis, and immunodepletion of IGFBP-4 from the CM significantly reversed these effects. Of note, the CM greatly reduced the phosphorylation of AKT, ERK, IGF-1 receptor beta, and p38 MAPK in a partly IGFBP4-dependent manner, possibly through its binding to IGF-1/2 and blocking the signaling. The CM depleted of IGFBP-4 also reversed the inhibitory effects on in vivo tumor growth and neovascularization. Thus, MSC-CM has potent inhibitory effects on tumor growth and neovascularization in an IGFBP4-dependent manner, suggesting that cell-free therapy using MSC-CM could be a safer promising alternative for even cancer patients.

Novel studies on Drosophila melanogaster model reveal the roles of JNK-Jak/STAT axis and intestinal microbiota in insulin resistance.

The JNK pathway play a critical role in insulin resistance induced by a long-term high-sugar diet. However, the roles of up- and downstream molecules of the JNK pathway in insulin resistance are less known in vertebrates and invertebrates. As a classical organism in biological research, Drosophila melanogaster (D. melanogaster) has been widely applied to the studies of mechanism of insulin resistance. Based on previous studies, we found a novel predictive mechanism of the formation of insulin resistance in D. melanogaster. We found that JNK activated by high-sugar diet and dysregulated intestinal microbiota could mediate inflammation, and then the activated JNK released Upd3, which in turn stimulated Jak/STAT pathway to release ImpL2. ImpL2 can compete with Drosophila insulin-like peptides (Dilps) for binding with the insulin receptor and inhibit the activation of insulin pathway. In this study, we reviewed novel studies on the insulin signalling pathway based on the D. melanogaster model. The findings support our hypothesis. We, therefore, described how a long-term high-sugar diet disrupts intestinal microbiota to induce inflammation and the disruption of JNK-Jak/STAT axis. This description may offer some new clues to the formation of insulin resistance.

Association between gestational diabetes mellitus and bioavailability of insulin-like growth factors and role of their binding proteins.

OBJECTIVE: Insulin-like growth factors (IGFs) are involved in regulating growth and metabolism and increase insulin sensitivity, improve glucose metabolism, and are potentially related to gestational diabetes mellitus (GDM) and its complications for mothers and fetuses. DESIGN: This study aimed to assess serum levels and cord blood levels of IGF system components in pregnant women with (39 participants) and without GDM (22 participants). Blood samples were obtained at 28-32 and 36-38 weeks of gestation and 6-12 months after delivery. Cord blood samples were obtained during delivery. Results between both groups as well as between single visits were statistically compared. RESULTS: Both IGF1 and IGF2 maternal serum levels did not differ between the GDM and non-GDM groups. However, levels of IGF-binding proteins (IGFBPs) were different. IGFBP4 levels were decreased during pregnancy and after delivery in women with GDM, while IGFBP7 levels were increased during pregnancy in women with GDM. Cord blood IGFBP3 and IGFBP7 levels were increased (p < 0.001 for IGFBP3, p = 0.003 for IGFBP7), while IGFBP4 levels were decreased (p < 0.001) in the GDM group compared with the non-GDM group. CONCLUSIONS: Although IGF levels did not differ, changes in their function level could still persist possibly because of the effects of the binding proteins, especially their promoting or inhibitory effects on IGFs. These results should be considered in interpretation of IGF levels.

Biological effects and regulation of IGFBP5 in breast cancer.

The insulin-like growth factor receptor (IGF1R) pathway plays an important role in cancer progression. In breast cancer, the IGF1R pathway is linked to estrogen-dependent signaling. Regulation of IGF1R activity is complex and involves the actions of its ligands IGF1 and IGF2 and those of IGF-binding proteins (IGFBPs). Six IGFBPs are known that share the ability to form complexes with the IGFs, by which they control the bioavailability of these ligands. Besides, each of the IGFBPs have specific features. In this review, the focus lies on the biological effects and regulation of IGFBP5 in breast cancer. In breast cancer, estrogen is a critical regulator of IGFBP5 transcription. It exerts its effect through an intergenic enhancer loop that is part of the chromosomal breast cancer susceptibility region 2q35. The biological effects of IGFBP5 depend upon the cellular context. By inhibiting or promoting IGF1R signaling, IGFBP5 can either act as a tumor suppressor or promoter. Additionally, IGFBP5 possesses IGF-independent activities, which contribute to the complexity by which IGFBP5 interferes with cancer cell behavior.