Human IGF-1 Research Articles

Characterization of Viral Insulin-Like Peptides Reveals Unique White Adipose Tissue Specific Characteristics

The members of the insulin superfamily are well conserved across the evolution tree. We recently showed that four viruses in the Iridoviridae family possess genes that share high similarity with human insulin and IGF-1. By chemically synthesizing single chain (sc, IGF-1 like) forms of these viral insulin/IGF-1 like peptides (VILPs), we previously showed that sc VILPs have insulin/IGF properties in vitro and in vivo. However, characteristics of double chain (dc, insulin-like) VILPs remain unknown. In this study, we characterized dc forms of VILPs for Grouper iridovirus (GIV), Singapore grouper iridovirus (SGIV) and Lymphocystis disease virus-1 (LCDV-1). We showed that GIV and SGIV dcVILPs bind to both isoforms of human insulin receptor (IR-A, IR-B) and they bind to IGF-1R with a higher affinity than human insulin. These dcVILPs stimulate receptor phosphorylation and post-receptor signaling in vitro and in vivo. LCDV-1 dcVILP stimulated a weak response in in vitro signaling experiments, although we could not determine binding competition. Both GIV and SGIV dcVILPs stimulated glucose uptake in mice. In vivo infusion experiments in awake mice revealed that while insulin (2.5 mU/kg/min) and GIV dcVILP (125 mU/kg/min) stimulate a comparable glucose uptake in heart, skeletal muscle and brown adipose tissue, GIV dcVILP stimulates ~2 fold higher glucose uptake in white adipose tissue (WAT) compared to insulin. This is due to increased Akt phosphorylation and glucose transporter type 4 (GLUT4) expression compared to insulin specifically in WAT. Taken together, these results show that dc GIV and SGIV dcVILPs are active members of the insulin superfamily with unique characteristics. This observation evokes questions about their potential roles in human disease including diabetes and cancer. Elucidating the mechanism of tissue specificity for GIV dcVILP will help us to better understand insulin action and design new analogues that specifically target the tissues.

Insulin‐like growth factor I reduces atherosclerosis in Rapacz pigs

Cardiovascular disease is the leading cause of mortality in the Western world and its manifestations result in large part from atherosclerotic lesion development and destabilization. We have reported previously that administration of insulin-like growth factor I (IGF-1) reduced atherosclerosis in the murine model. To test the effect of IGF-1 on human-like atherosclerosis we injected 50 ug/kg recombinant human IGF-1 or saline (control) (n=9/group) into high-fat diet fed Rapacz familial hypercholesterolemic (FH) swine for 6 months. We quantified vessel volume, atherosclerotic burden (% of volume of atherosclerotic plaque + media per vessel volume), lumen volume and assessed plaque phenotype in coronary arteries using intravascular ultrasound (IVUS) at time 0 and after 3 and 6 months on the diet. IGF-1-injected pigs had on average 2.6-fold increase in total plasma IGF-1 (ELISA, p<0.001 vs. control pigs). Pigs in the IGF-1 and control group gradually gained weight over the time of experiment, however pigs in the IGF-1 group had a larger increase in BW compared to controls at 6 months (IGF-1, 60.6±7.4% increase vs. saline, 44.3±4.0% increase, p<0.05) consistent with growth-stimulating effects of IGF-1. Pigs in both groups had a gradual increase in vessel volume in the right coronary artery (RCA), left anterior descending artery (LAD) and left circumflex artery (LCX) with time as quantified by serial IVUS. However, IGF-1-injected pigs had a larger increase in vessel volume after 3 and 6 months compared to controls suggesting vascular hypertrophy. The atherosclerotic burden was increased in RCA, LAD and LCX in both groups after 3 and 6 months of injections compared to the pre-injection time point. We found a significant reduction in atherosclerotic burden in RCA and LAD in IGF-1 group compared to control at 6 months’ time-point (RCA: IGF-1, 203±13%, vs. control, 244±8; LAD: IGF-1, 200±6%, vs. control, 228±11%). The lumen volume of coronaries was decreased in both groups, however, coronaries in IGF-1-injected pigs had on average 24±3% larger lumen volume compared to control pigs at 6 months’ time-point. We used virtual histology (VH) post-IVUS image processing to assess plaque composition and to classify plaque sub-types. Pigs in both groups had a progressive increase in plaque calcification, necrotic core area, fibrous plaque and fibro-fatty plaque area. IGF-1 did not significantly change plaque composition. In summary, we report that IGF-1 increased pig BW, and total volume of coronaries suggesting hypertrophy and these data are consistent with growth-stimulating effects of IGF-1. We found a significant reduction in atherosclerotic burden and increase in lumen volume in coronaries in the IGF-1 group after 6 months of injections consistent with an anti-atherosclerotic effect of IGF-1. Our data support the feasibility of using IGF-1 as an anti-atherogenic therapy.

P5: EFFECT OF VITAMIN C AND COLD ON GROWTH FACTOR RELEASE FROM PLATELET-RICH PLASMA

Abstract Introduction Platelet-rich plasma (PRP) has gathered great momentum in surgery. The main outcome of the study was to assess whether there was a difference in growth factor release from PRP with addition of vitamin C, cooling, or both vitamin C and cooling. Method Blood samples from 10 volunteers were centrifuged to produce PRP. Activated autologous thrombin was produced from platelet-poor plasma (PPP), which was added to PRP to activate it. PRP from each participant was then divided by activation method into three groups: A) cold pack only; B) vitamin C only; C) cold pack/vitamin C. Growth factor quantification was performed for human VEGF, IGF-1 and PDGF-AB using enzyme-linked immunosorbent assays. Result At 24 hours, VEGF concentration in the cold group was significantly higher cf. the vitamin C group (p=0.02) and the cold/vit C group (p&amp;lt;0.01), whereas IGF concentration in the cold group was significantly higher cf. the vitamin C group (p=0.02) but not the cold/vit C group. At 1 hour and 24 hours, PDGF concentration in the cold group was significantly higher cf. both the vitamin C group (p&amp;lt;0.01) and the cold/vit C group (p=0.02 and p&amp;lt;0.0001 respectively). Conclusion Cooling lead to increased growth factor release at 24 hours, indicating that cooling may lead to sustained release of growth factors. There was a trend for PRP treated with vitamin C to remain in a gel-like consistency rather than clot. This may prove useful in clinical practice where currently activated PRP is constrained to topical application only due to its consistency. Take-home message Cooling may lead to sustained release of growth factors from platelet-rich plasma, whereas the addition of vitamin C may provide opportunity for injectable activated PRP.

RNA m6A reader IMP2/IGF2BP2 promotes pancreatic β-cell proliferation and insulin secretion by enhancing PDX1 expression

BackgroundType 2 diabetes (T2D) is a common metabolic disease. Variants in human IGF2 mRNA binding protein 2 (IMP2/IGF2BP2) are associated with increased risk of T2D. IMP2 contributes to T2D susceptibility primarily through effects on insulin secretion. However, the underlying mechanism is not known. MethodsTo understand the role of IMP2 in insulin secretion and T2D pathophysiology, we generated Imp2 pancreatic β-cell specific knockout mice (βIMP2KO) by recombining the Imp2flox allele with Cre recombinase driven by the rat insulin 2 promoter. We further characterized metabolic phenotypes of βIMP2KO mice and assessed their β-cell functions. ResultsThe deletion of IMP2 in pancreatic β-cells leads to reduced compensatory β-cell proliferation and function. Mechanically, IMP2 directly binds to Pdx1 mRNA and stimulates its translation in an m6A dependent manner. Moreover, IMP2 orchestrates IGF2-AKT-GSK3β-PDX1 signaling to stable PDX1 polypeptides. In human EndoC-βH1 cells, the over-expression of IMP2 is capable to enhance cell proliferation, PDX1 protein level and insulin secretion. ConclusionOur work therefore reveals IMP2 as a critical regulator of pancreatic β-cell proliferation and function; highlights the importance of posttranscriptional gene expression in T2D pathology.

Supplemental Insulin-Like Growth Factor-1 and Necrotizing Enterocolitis in Preterm Pigs.

Background: Recombinant human IGF-1/binding protein-3 (rhIGF-1/BP-3) is currently tested as a therapy in preterm infants but possible effects on the gut, including necrotizing enterocolitis (NEC), have not been tested. The aim of this study was to evaluate if rhIGF-1/BP-3 supplementation in the first days after birth negatively affects clinical variables like growth, physical activity, blood chemistry and hematology and gut maturation (e.g., intestinal permeability, morphology, enzyme activities, cytokine levels, enterocyte proliferation, NEC lesions), using NEC-sensitive preterm pigs as a model for preterm infants.Methods: Preterm pigs were given twice daily subcutaneous injections of rhIGF-1/BP-3 or vehicle. Blood was collected for IGF-1 measurements and gut tissue for NEC evaluation and biochemical analyses on day 5.Results: Baseline circulating IGF-1 levels were low in preterm pigs compared with near-term pigs reared by their mother (<20 vs. 70 ng/ml). Injection with rhIGF-1/BP-3 resulted in increased plasma IGF-1 levels for up to 6 h after injection (>40 ng/mL). rhIGF-1/BP-3 treatment reduced the incidence of severe NEC lesions (7/24 vs.16/24, p = 0.01) and overall NEC severity (1.8 ± 0.2 vs. 2.6 ± 0.3, p < 0.05, with most lesions occurring in colon). In the small intestine, villi length (405 ± 25 vs. 345 ± 33 μm) and activities of the brush border peptidases aminopeptidase N and dipeptidylpeptidase IV were increased in rhIGF-1/BP-3 treated pigs, relative to control pigs (+31–44%, both p < 0.05). The treatment had no effects on body weight, blood chemistry or hematology, except for an increase in blood leucocyte and neutrophil counts (p < 0.05, i.e., reduced neonatal neutropenia). Likewise, rhIGF-1/BP-3 treatment did not affect intestinal tissue cytokine levels (IL-1β, IL-6, IL-8, TNFα,), enterocyte proliferation, goblet cell density, permeability or bacterial translocation to the bone marrow.Conclusion: Supplemental rhIGF-1/BP-3 did not negatively affect any of the measured variables of clinical status or gut maturation in preterm pigs. Longer-term safety and efficacy of exogenous rhIGF-1/BP-3 to support maturation of the gut and other critical organs in preterm newborns remain to be investigated in both pigs and infants.

Insulin-like growth factor 2 is produced by antral follicles and promotes preantral follicle development in macaques†.

Insulin-like growth factors (IGFs) are known for their involvement in endocrine and paracrine regulation of ovarian function. Although IGF2 is the predominant circulating and intraovarian form of IGFs in primate species, the stage-specific follicular expression, action, and regulation of IGF2 are not well defined. Therefore, experiments were conducted to investigate the follicular IGF production in response to steroid hormone regulation and the direct IGF actions on follicular development and function in vitro. Preantral follicles were isolated from rhesus macaque ovaries and cultured to the antral stage in media supplemented with follicle-stimulating hormone and insulin. Follicles were randomly assigned to treatment groups: (a) control, (b) trilostane (a steroid synthesis inhibitor), (c) trilostane + estradiol, (d) trilostane + progesterone, and (e) trilostane + dihydrotestosterone. Media was analyzed for IGF concentrations, which were correlated to follicle growth. Follicles produced IGF2, but not IGF1, at the antral stage. Steroid depletion decreased, whereas steroid replacement increased, IGF2 production by antral follicles. Media IGF2 levels correlated positively with antral follicle diameters. Macaque preantral follicles and granulosa cells were subsequently cultured without (control) and with recombinant human IGF2 supplementation. Follicle survival, growth, and paracrine factor production, as well as granulosa cell proliferation and gonadotropin receptor gene expression, were assessed. IGF2 addition increased follicle survival rates, diameters and inhibin B production, as well as granulosa cell proliferation. These data demonstrate that IGF2 produced by antral follicles, in response to steroid hormone regulation, could act as a paracrine factor that positively impacts preantral follicle development and function in primates.

The effects of recombinant human insulin-like growth factor-1/insulin-like growth factor binding protein-3 administration on lipid and carbohydrate metabolism in recreational athletes.

Previous studies suggested that recombinant human IGF-1 (rhIGF-1) administration affects carbohydrate and lipid metabolism in healthy people and in people with diabetes. This study aimed to determine the effects of rhIGF-1/rhIGF binding protein-3 (rhIGFBP-3) administration on glucose homeostasis and lipid metabolism in healthy recreational athletes. Randomized, double-blind, placebo-controlled rhIGF-1/rhIGFBP-3 administration study at Southampton General Hospital, UK. 56 recreational athletes (30 men, 26 women). Participants were randomly assigned to receive placebo, low-dose rhIGF-1/rhIGFBP-3 (30mg/day) or high-dose rhIGF-1/rhIGFBP-3 (60mg/day) for 28days. The following variables were measured before and immediately after the treatment period: fasting lipids, glucose, insulin, C-peptide and glycated haemoglobin. The homeostatic model assessment (HOMA-IR) was used to estimate insulin sensitivity and indirect calorimetry to assess substrate oxidation rates. The general linear model approach was used to compare treatment group changes with the placebo group. Compared with the placebo group, there was a significant reduction in fasting triglycerides in participants treated with high-dose rhIGF-1/rhIGFBP-3 (p=.030), but not in the low-dose group (p=.390). In women, but not in men, there were significant increases in total cholesterol (p=.003), HDL cholesterol (p=.001) and LDL cholesterol (p=.008). These lipid changes were associated with reduced fasting insulin (p=.010), C-peptide (p=.001) and HOMA-IR (p=.018) in women and reduced C-peptide (p=.046) in men. rhIGF-1/rhIGFBP-3 administration for 28days reduced insulin concentration, improved insulin sensitivity and had significant effects on lipid profile including decreased fasting triglycerides.

Randomized Control Trial of Postnatal rhIGF-1/rhIGFBP-3 Replacement in Preterm Infants: Post-hoc Analysis of Its Effect on Brain Injury.

Background: Postnatal insulin-like growth factor-1 (IGF-1) replacement with recombinant human (rh)IGF-1 and IGF binding protein-3 (rhIGF-1/rhIGFBP-3) is being studied as a potential treatment to reduce comorbidities of prematurity. We have recently reported on a phase II, multicenter, randomized, controlled trial comparing postnatal rhIGF-1/rhIGFBP-3 replacement with standard of care (SOC) in extremely preterm infants (NCT01096784). Maximum severity of retinopathy of prematurity was the primary endpoint of the trial and presence of GMH-IVH/PHI one of the pre-specified secondary endpoints. Infants therefore received serial cranial ultrasound scans (CUS) between birth and term age. In this post-hoc analysis we present a detailed analysis of the CUS data of this trial and evaluate the effect of postnatal rhIGF-1/rhIGFBP-3 replacement on the incidence of different kinds of brain injury in extremely preterm infants.Methods: This report is an exploratory post-hoc analysis of a phase II trial in which infants <28 weeks gestational age were randomly allocated to rhIGF-1/rhIGFBP-3 or SOC. Serial cranial ultrasounds were performed between birth and term-equivalent age. Presence of germinal matrix hemorrhage and intraventricular hemorrhage (GMH-IVH), periventricular hemorrhagic infarction (PHI), post-hemorrhagic ventricular dilatation, and white matter injury (WMI) were scored by two independent masked readers.Results: The analysis included 117 infants; 58 received rhIGF-1/rhIGFBP-3 and 59 received SOC. A trend toward less grade II–III GMH-IVH and PHI was observed in treated infants vs. SOC. A subanalysis of infants without evidence of GMH-IVH at study entry (n = 104) showed reduced progression to GMH-IVH in treated infants (25.0% [13/52] vs. 40.4% [21/52]; not significant). No effects of rhIGF-1/rhIGFBP-3 on WMI were observed.Conclusion: The potential protective effect of rhIGF-1/rhIGFBP-3 on the occurrence of GMH-IVH/PHI appeared most pronounced in infants with no evidence of GMH-IVH at treatment start.

IGF1, serum glucose, and retinopathy of prematurity in extremely preterm infants.

BACKGROUNDHyperglycemia, insulin insensitivity, and low IGF1 levels in extremely preterm infants are associated with an increased risk of retinopathy of prematurity (ROP), but the interactions are incompletely understood.METHODSIn 117 extremely preterm infants, serum glucose levels and parenteral glucose intake were recoded daily in the first postnatal week. Serum IGF1 levels were measured weekly. Mice with oxygen-induced retinopathy alone versus oxygen-induced retinopathy plus streptozotocin-induced hyperglycemia/hypoinsulinemia were assessed for glucose, insulin, IGF1, IGFBP1, and IGFBP3 in blood and liver. Recombinant human IGF1 was injected to assess the effect on glucose and retinopathy.RESULTSThe highest mean plasma glucose tertile of infants positively correlated with parenteral glucose intake [r(39) = 0.67, P < 0.0001]. IGF1 plasma levels were lower in the high tertile compared with those in low and intermediate tertiles at day 28 (P = 0.038 and P = 0.03). In high versus lower glucose tertiles, ROP was more prevalent (34 of 39 versus 19 of 39) and more severe (ROP stage 3 or higher; 71% versus 32%). In oxygen-induced retinopathy, hyperglycemia/hypoinsulinemia decreased liver IGF1 expression (P < 0.0001); rh-IGF1 treatment improved normal vascular regrowth (P = 0.027) and reduced neovascularization (P < 0.0001).CONCLUSIONIn extremely preterm infants, high early postnatal plasma glucose levels and signs of insulin insensitivity were associated with lower IGF1 levels and increased ROP severity. In a hyperglycemia retinopathy mouse model, decreased insulin signaling suppressed liver IGF1 production, lowered serum IGF1 levels, and increased neovascularization. IGF1 supplementation improved retinal revascularization and decreased pathological neovascularization. The data support IGF1 as a potential treatment for prevention of ROP.TRIAL REGISTRATIONClinicalTrials.gov NCT02760472 (Donna Mega).FUNDINGThis study has been supported by the Swedish Medical Research Council (14940, 4732, 20144-01-3, and 21144-01-3), a Swedish government grant (ALFGB2770), Lund medical faculty grants (ALFL, 11615 and 11601), the Skåne Council Foundation for Research and Development, the Linnéa and Josef Carlsson Foundation, the Knut and Alice Wallenberg Foundation, the NIH/National Eye Institute (EY022275, EY017017, EY017017-13S1, and P01 HD18655), European Commission FP7 project 305485 PREVENT-ROP, Deutsche Forschungsgemeinschaft (CA-1940/1-1), and Stiftelsen De Blindas Vänner.

Growth Factor Concentrations in Human Milk Are Associated With Infant Weight and BMI From Birth to 5 Years.

Background: Human milk bioactives may play a role in infant health and development. Although the variability in their concentrations in milk is well-established, the impact of differential milk profiles on infant growth outcomes remains unclear. Thus, the aim of the present study was to investigate whether different concentrations of metabolic hormones are associated with different weight and BMI in infants beyond the first year of life.Methods: Milk samples at 2.6 (±0.4) months after birth and anthropometric measures at 13 months, 2, 3, and 5 years were collected as part of the Finnish STEPS cohort study from 501 mothers and the respective 507 infants. Leptin, adiponectin, insulin-like growth factor (IGF)-1 and cyclic glycine-proline (cGP) in milk were analyzed. Multiple regression models and a repeated measures mixed model were used to examine associations between milk hormone concentrations and weight and BMI z-scores across time, at each time-point, and weight gain from birth to each follow-up visit. All models were corrected for birth weight, infant sex, duration of exclusive and total breastfeeding, time of introduction of solid foods and maternal pre-pregnancy BMI.Results: Higher milk IGF-1 was associated with higher weight at 13 months (p = 0.004) but lower weight at 3 (p = 0.011) and 5 years of age (p = 0.049). Higher cGP was associated with lower weight across the 5 years (p = 0.019) but with higher BMI at 5 years (p = 0.021). Leptin and adiponectin did not display associations with infant growth at this time. Sex interactions were also absent.Conclusions: Our results suggest that the interplay between human milk-borne IGF-1 and cGP is similar to that reported in other mammals and may have an important role in defining infant growth trajectories beyond the first year of life. Further research should explore the determinants and origins of these milk-borne compounds and evaluate their effect on infant growth and metabolism.

1725-P: Viral Insulins as Agonists and Antagonists on Insulin/IGF-1 Receptors

Recently, we identified four insulin/IGF-1 like peptides (VILPs) in the sequence of viruses belonging to the Iridoviridae family. These VILPs show up to 50% homology with the sequence of the human insulin/IGF-1. Moreover, the predicted tertiary structures and major receptor binding residues are conserved between the VILPs and insulin/IGF-1. Although these viruses are known to infect primarily fish, sequences of VILPs have been found in human blood and feces. VILPs can interact with the human and murine insulin and IGF-1 receptors and induce the activation of their downstream signaling. Functionally, VILPs are able to induce glucose uptake and cell proliferation. VILPs can be synthesized as a single-chain (SC) or double-chain (DC) peptides, i.e., more IGF-1 like or more insulin like structures. In the present study, we show that SC and DC forms of lymphocystis disease virus (LCDV-1) VILP interact differently with the human insulin and IGF-1 receptor. Competition binding assay reveals that SC is more potent than DC in binding to the IGF-1 receptor. In vivo, following i.p. injection in mice both LCDV-1 SC and DC produced similar mild decreases in blood glucose compared to insulin, even at a 166-fold excess. In vitro, however, DC LCDV1-VILP acts as a weak agonist to stimulation of IGF1R, whereas SC LCDV-VILP serves as a strong antagonism effect on the IGF-1 receptor. Thus, the activation of the IGF1R by IGF-1 is strongly repressed by the SC LCDV-1 VILP, even at equal concentrations. This antagonistic action of SC VILP is restricted to the IGF1R and does not affect insulin receptor. As a functional consequence of IGF1R blockade, SC LCDV-1 VILP inhibits IGF-1 stimulated migration of a cervical cancer cell line. In summary, we have shown that SC VILP may provide a novel inhibitor of IGF1R signaling and IGF-1 action on tumor cell migration, with minimal effects on glucose metabolism, thus providing a potentially unique reagent for treatment of IGF-1 sensitive tumors. Disclosure F. Moreau: None. B. Brandao: None. C. Cederquist: None. T.M. Batista: None. R. DiMarchi: Employee; Self; Novo Nordisk Inc. E. Altindis: None. C. Kahn: Advisory Panel; Self; ERX Pharmaceuticals, Kaleido Biosciences. Consultant; Self; AntriaBio, Flagship Pioneering, Sana-Cobalt.

Tart Cherry Increases Lifespan in Caenorhabditis elegans by Altering Metabolic Signaling Pathways.

Aging and healthspan are determined by both environmental and genetic factors. The insulin/insulin-like growth factor-1(IGF-1) pathway is a key mediator of aging in Caenorhabditis elegans and mammals. Specifically, DAF-2 signaling, an ortholog of human IGF, controls DAF-16/FOXO transcription factor, a master regulator of metabolism and longevity. Moreover, mitochondrial dysfunction and oxidative stress are both linked to aging. We propose that daily supplementation of tart cherry extract (TCE), rich in anthocyanins with antioxidant properties may exert dual benefits for mitochondrial function and oxidative stress, resulting in beneficial effects on aging in C. elegans. We found that TCE supplementation at 6 μg or 12 μg/mL, increased (p < 0.05) the mean lifespan of wild type N2 worms, respectively, when compared to untreated control worms. Consistent with these findings, TCE upregulated (p < 0.05) expression of longevity-related genes such as daf-16 and aak-2 (but not daf-2 or akt-1 genes) and genes related to oxidative stress such as sod-2. Further, we showed that TCE supplementation increased spare respiration in N2 worms. However, TCE did not change the mean lifespan of daf-16 and aak-2 mutant worms. In conclusion, our findings indicate that TCE confers healthspan benefits in C. elegans through enhanced mitochondrial function and reduced oxidative stress, mainly via the DAF-16 pathway.

Visualization of Ligand-Bound Ectodomain Assembly in the Full-Length Human IGF-1 Receptor by Cryo-EM Single-Particle Analysis

Tyrosine kinase receptor of insulin-like growth factor 1 receptor (IGF-1R) and insulin receptor (IR) bind to hormones, such as insulin, IGF-1, and IGF-2, and transduces the signals across the cell membrane. However, the complete structure of the receptor and the signal transduction mechanism remains unclear. Here, we report the cryo-EM structure of the ligand-bound ectodomain in the full-length human IGF-1R. We reconstructed the IGF-1R/insulin complex at 4.7Å and the IGF-1R/IGF-1 complex at 7.7Å. Our structures reveal that only one insulin or one IGF-1 molecule binds to and activates the full-length human IGF-1R receptor.

SUN-027 Delivery of MSCs with a Hybrid β-sheet Peptide Hydrogel Consisting IGF-1C Domain and D-form Peptide for Acute Kidney Injury Therapy

By providing an appropriate microenvironment, synthetic biomaterials have been progressively successful in stem cell-based tissue regeneration by enhancing the engraftment and survival of transplanted cells. The designs with bioactive motifs to influence cell behavior and with D-form amino acid to modulate scaffold stability will be critical for the development and optimization of self-assembling biomimetic hydrogel scaffolds for stem cell therapy. In this study, we linked naphthalene (Nap) covalently conjugated a short D-form peptide (Nap-DFDFG) to C domain of insulin-like growth factor-1 (IGF-1C) as a functional peptide-based scaffold. Our purpose is to provide a functional self-assembling peptide hydrogel with encapsulated human placenta derived mesenchymal stem cells (hP-MSCs) and thereby to enhance the therapeutic efficiency of hP-MSCs in murine acute kidney injury (AKI) model. Our results revealed that a typical β-sheet conformation was confirmed and this self-assembling peptide hydrogel exhibited higher affinity with IGF-1 receptor. Furthermore, this hydrogel could provide a favorable niche for hP-MSCs and thereby ameliorate renal function in an AKI model by promoting cell survival and angiogenesis. In conclusion, by covalently linking the desired functional group to D-form peptide to create a functional hydrogel, this self-assembling β-sheet peptide hydrogel will serve as a promising platform for future tissue-engineering and stem cell therapy. We prepared a supramolecular self-assembly peptide Nap-DFDFG-IGF-1C by standard solid phase peptide synthesis (SPPS), and profiled the characteristics by circular dichroism (CD) analysis, surface plasmon resonance (SPR), transmission electron microscope (TEM) and rheological analysis. For real-time tracing the cell fate post transplantation, we introduced dual fusion MSCs which express firefly luciferase and GFP simultaneously. Also we utilized the bioluminescence imaging (BLI) to longitudinally monitor the dynamics of cell retention and renal angiogenesis. Serial experiments have bee done to evaluate the putative therapeutic effect for AKI. We here reported a hybrid self-assembly peptide Nap-DFDFG-IGF-1C. CD analysis revealed the peptide was constrained to a typical β-sheet conformation via a heating-cooling pathway, leading to an enhanced affinity with recombinant human IGF-1 receptor (rhIGF-1R) comfirmed by SPR. A cross-linked nanofibrous structure was observed by TEM and the rheological analysis evidenced its hydrogel property. Our BLI results showed that delivery of MSCs with the IGF-1C hydrogel contribute to an enhanced cell retention and renal angiogenesis, which rsulted in repair and regeneration post AKI. In summary, we reported a cell enhancement strategy with a hybrid β-sheet peptide hydrogel which holds bioactive motif IGF-1C as functional backbone for the first time. This hydrogel favors cell retention, provides a pro-angiogenesis niche for the transplanted cells, and thereby restored the renal architecture and function post AKI. This study introduced a brand-new strategy for integration of self-assembly peptide and stem cell therapy and might shed light into the development of tissue engineering as well as regeneration medicine.

Therapy with recombinant human IGF-1 for children with primary insulin-like growth factor-I deficiency

The efficacy and safety of IGF-1 therapy in patients with severe primary IGF-I deficiency has been evaluated for more than two decades. Most of the therapeutic experience comes from treating the more severe IGF-I deficient patients, who usually present with a phenotype characteristic of growth hormone receptor deficiency or Laron syndrome. Although most of these patients do not experience enough catchup growth to bring their height into normal range, many individuals achieve an adult height significantly greater than what would have been predicted in the absence of IGF-1 therapy. In the last couple of years a few reports on the benefit of IGF-1 therapy for patients with milder types of IGF-I deficiency have also been published, with variable height outcomes. More short children with prior diagnosis of idiopathic short stature are now being diagnosed with specific molecular defects of the growth hormone/IGF-I axis. Because of this, the clinical spectrum of primary IGF-I deficiency is widening to include many patients with such a milder phenotype, creating a need for well-designed long-term clinical studies evaluating the growth response to growth promoting agents such as rhIGF-1 in these individuals.

IGF-1 is associated with estimated bone strength in anorexia nervosa.

Women with anorexia nervosa, a psychiatric disorder characterized by self-induced starvation and low body weight, have impaired bone formation, low bone mass, and an increased risk of fracture. IGF-1 and leptin are two nutritionally dependent hormones that have been associated with low bone mass in women with anorexia nervosa. We hypothesized that IGF-1 and leptin would also be positively associated with estimated bone strength in women with anorexia nervosa. In this cross-sectional study of 38 women (19 with anorexia nervosa and 19 normal-weight controls), we measured serum IGF-1 and leptin and performed finite element analysis of high-resolution peripheral quantitative CT images to measure stiffness and failure load of the distal radius and tibia. IGF-1 was strongly correlated with estimated bone strength in the radius (R = 0.52, p = 0.02 for both stiffness and failure load) and tibia (R = 0.55, p = 0.01 for stiffness and R = 0.58, p = 0.01 for failure load) in the women with anorexia nervosa but not in normal-weight controls. In contrast, leptin was not associated with estimated bone strength in the group of women with anorexia nervosa or normal-weight controls. IGF-1 is strongly associated with estimated bone strength in the radius and tibia in women with anorexia nervosa. Further studies are needed to assess whether treatment with recombinant human IGF-1 will further improve bone strength and reduce fracture risk in this population.

Neurotropic and modulatory effects of insulin-like growth factor II in Aplysia

Insulin-like growth factor II (IGF2) enhances memory in rodents via the mannose-6-phosphate receptor (M6PR), but the underlying mechanisms remain poorly understood. We found that human IGF2 produces an enhancement of both synaptic transmission and neurite outgrowth in the marine mollusk Aplysia californica. These findings were unexpected since Aplysia lack the mammal-specific affinity between insulin-like ligands and M6PR. Surprisingly, this effect was observed in parallel with a suppression of neuronal excitability in a well-understood circuit that supports several temporally and mechanistically distinct forms of memory in the defensive withdrawal reflex, suggesting functional coordination between excitability and memory formation. We hypothesize that these effects represent behavioral adaptations to feeding that are mediated by the endogenous Aplysia insulin-like system. Indeed, the exogenous application of a single recombinant insulin-like peptide cloned from the Aplysia CNS cDNA replicated both the enhancement of synaptic transmission, the reduction of excitability, and promoted clearance of glucose from the hemolymph, a hallmark of bona fide insulin action.

Insulin-like growth factor-1 short-period therapy improves cardiomyopathy stimulating cardiac progenitor cells survival in obese mice

Background and aimsCardiovascular diseases are the main cause of mortality in obesity. Despite advanced understanding, the mechanisms that regulate cardiac progenitor cells (CPC) survival in pathological conditions are not clear. Low IGF-1 plasma levels are correlated to obesity, cardiomyopathy and CPC death, so this work aimed to investigate IGF-1 therapeutic potential on cardiomyopathy and its relationship with the survival, proliferation and differentiation of CPC in Western diet-induced obesity. Methods and resultsMale Swiss mice were divided into control group (CG, n = 8), fed with standard diet; and obese group (OG, n = 16), fed with Western diet, for 12 weeks. At 11th week, OG was subdivided to receive a daily subcutaneous injection of human recombinant IGF-1 (100 μg.Kg−1) for seven consecutive days (OG + IGF1, n = 8). Results showed that IGF-1 therapy improved the metabolic parameters negatively impacted by western diet in OG, reaching levels similar to CG. OG + IGF-1 also demonstrated restored heart energetic metabolism, fibrosis resolution, decreased apoptosis level, restored cardiac gap junctions and intracellular calcium balance. Cardiomyopathy improvement was accompanied by increased CPC survival, proliferation and newly cardiomyocytes formation related to increased pAkt/Akt ratio. ConclusionThese results suggest that only one week of IGF-1 therapy has cardioprotective effects through Akt pathway upregulation, ensuring CPC survival and differentiation, contributing to heart failure rescue.

A novel epitope-presenting thermostable scaffold for the development of highly specific insulin-like growth factor-1/2 antibodies

High sequence and structural homology between mature human insulin-like growth factors IGF-1 and IGF-2 makes serological discrimination by immunodiagnostic IGF tests a challenging task. There is an urgent need for highly specific IGF-1 and IGF-2 antibodies, yet only a short sequence element, i.e. the IGF loop, provides enough difference in sequence to discriminate between the two molecules. We sought to address this unmet demand by investigating novel chimeric immunogens as carriers for recombinant peptide motif grafting. We found Thermus thermophilus sensitive to lysis D (SlyD) and Thermococcus gammatolerans SlyD FK-506–binding protein (FKBP) domains suitable for presentation of the predefined epitopes, namely the IGF-1 and IGF-2 loops. Chimeric SlyD-IGF proteins allowed for the development of exceptionally specific IGF-1 and IGF-2 monoclonal antibodies. The selected antibodies bound with high affinity to the distinct IGF epitopes displayed on the protein scaffolds, as well as on the mature human IGF isoforms. The respective SlyD scaffolds display favorable engineering properties in that they are small, monomeric, and cysteine-free and can be produced in high yields in a prokaryotic host, such as Escherichia coli. In conclusion, FKBP domains from thermostable SlyD proteins are highly suitable as a generic scaffold platform for epitope grafting.

IGF2 enhanced the osteo-/dentinogenic and neurogenic differentiation potentials of stem cells from apical papilla.

In dental tissue engineering, niche is important for maintaining stem cell function and regenerating the dental tissues. However, there is limited knowledge for the growth factors in niche to maintain the function of stem cells. In this study, we investigated the effect of IGF2, a growth factor in stem cells from apical papilla (SCAPs) niche, on differentiation and proliferation potentials of SCAPs. Recombinant human IGF2 protein (rhIGF2) was used. Cell counting kit-8 assay, Carboxyfluorescein succinimidyl ester assay, alkaline phosphatase (ALP) activity, Alizarin Red staining, quantitative calcium analysis, immunofluorescence staining and real-time RT-PCR were performed to investigate the cell proliferation and differentiation potentials of SCAPs. And proteomic analysis was used to identify the differential secreted proteins. By ALP activity assay, we found that 5ng/mL rhIGF2 might be the optimal concentration for treatment. Then, Alizarin Red staining, quantitative calcium analysis and osteogenesis-related gene expression results showed that 5ng/mL rhIGF2 could enhance the osteo-/dentinogenic differentiation potentials in SCAPs. Immunofluorescence staining and real-time RT-PCR results showed that neurogenic markers were significantly induced by 5ng/mL rhIGF2 in SCAPs. Then, CCK-8 assay and CFSE assay results showed that 5ng/mL rhIGF2 could enhance the cell proliferation in SCAPs. Furthermore, proteomic analysis showed that IGF2 could induce some secreted proteins which function related to the osteogenesis, neurogenesis and cell proliferation. Our results identified that IGF2 might be the potential mediator in niche to promote SCAP function and dental tissue regeneration.