Specific IGF-1 Research Articles

Unlocking the potential of exercise: harnessing myokines to delay musculoskeletal aging and improve cognitive health.

This review aims to summarize the common physiological mechanisms associated with both mild cognitive impairment (MCI) and musculoskeletal aging while also examining the relevant literature on how exercise regulation influences the levels of shared myokines in these conditions. The literature search was conducted via databases such as PubMed (including MEDLINE), EMBASE, and the Cochrane Library of Systematic Reviews. The searches were limited to full-text articles published in English, with the most recent search conducted on 16 July 2024. The inclusion criteria for this review focused on the role of exercise and myokines in delaying musculoskeletal aging and enhancing cognitive health. The Newcastle‒Ottawa Scale (NOS) was utilized to assess the quality of nonrandomized studies, and only those studies with moderate to high quality scores, as per these criteria, were included in the final analysis. Data analysis was performed through narrative synthesis. The primary outcome of this study was the evaluation of myokine expression, which included IL-6, IGF-1, BDNF, CTSB, irisin, and LIF. A total of 16 studies involving 633 older adults met the inclusion criteria. The current exercise modalities utilized in these studies primarily consisted of resistance training and moderate-to high-intensity cardiovascular exercise. The types of interventions included treadmill training, elastic band training, aquatic training, and Nordic walking training. The results indicated that both cardiovascular exercise and resistance exercise could delay musculoskeletal aging and enhance the cognitive functions of the brain. Additionally, different types and intensities of exercise exhibited varying effects on myokine expression. Current evidence suggests that exercise mediates the secretion of specific myokines, including IL-6, IGF-1, BDNF, CTSB, irisin, and LIF, which establish self-regulatory circuits between the brain and muscle. This interaction enhances cognitive function in the brain and improves skeletal muscle function. Future research should focus on elucidating the exact mechanisms that govern the release of myokines, the correlation between the intensity of exercise and the secretion of these myokines, and the distinct processes by which myokines influence the interaction between muscle and the brain.

FRI671 Association Of Insulin-like Growth Factor-1 (igf-1) With Bone Mineral Density (bmd) In Survivors Of Childhood Acute Leukemia

Abstract Disclosure: S. Kim: None. S. Park: None. S. Sim: None. S. Kim: None. M. Ahn: None. K. Shin Hee: None. W. Cho: None. C. Kyung Soon: None. M. Jung: None. B. Suh: None. Purpose: To investigate bone mineral deficit in children survivors of childhood acute leukemia and analyze the association of IGF-1 with BMD status Methods : A total 214 patients (aged 8.47±4.42 for girls and 8.31±4.09 for boys at diagnosis) who were treated for acute leukemia were retrospectively reviewed. Types of leukemia, transplantation, and radiation therapy were investigated. Standard deviation scores (SDSs) of height, weight, body mass index (BMI), and lumbar spine BMD were measured at the end of treatment. Lumbar spine BMD was measured using dual-energy x-ray absorptiometry (DXA). Its relationships with calcium, phosphorus, alkaline phosphatase, bone specific alkaline phosphatase, calcitriol, parathyroid hormone, growth hormone, IGF-1, and insulin-like growth factor-binding protein-3 (IGFBP-3) were analyzed. Low BMD was defined lumbar spine BMD SDS less than -2.0 according to International Society for Clinical Densitometry guideline. Results: The overall prevalence of low BMD was found to be 15% (32/214). Age at diagnosis, transplantation, and radiation therapy were not significantly different between low BMD and normal BMD groups, however, BMI SDS and IGF-1 SDS were different between those two groups (-0.84±1.94 vs. 0.17±2.09, P = 0.012; -1.23 ±0.82 vs. -0.72 ± 0.78, P = 0.001, respectively). Correlation analysis showed that IGF-1 SDS is associated with BMI SDS and lumbar spine BMD SDS (rho=0.19, P=0.006; rho=0.248, P=0.001, respectively). Lumbar spine BMD SDS was related to BMI SDS and IGF-1 SDS by multivariate linear regression analysis (β = 0.15, P = 0.003; β = 0.31, P = 0.021, respectively). Multivariate logistic regression analysis showed that higher IGF-1 SDS was associated with a decreased of prevalence of low BMD (odds ratio: 0.42, 95% confidence interval: 0.24-0.75, P = 0.003). Conclusion: IGF-1 SDS was related to BMD, especially lumbar spine BMD, and a risk of prevalence of low BMD in children and adolescents. IGF-1 SDS seems to be a good tool for evaluating and predicting osteoporosis in children and adolescents. Presentation: Friday, June 16, 2023

Sheep recombinant IGF-1 promotes organ-specific growth in fetal sheep.

IGF-1 is a critical fetal growth-promoting hormone. Experimental infusion of an IGF-1 analog, human recombinant LR3 IGF-1, into late gestation fetal sheep increased fetal organ growth and skeletal muscle myoblast proliferation. However, LR3 IGF-1 has a low affinity for IGF binding proteins (IGFBP), thus reducing physiologic regulation of IGF-1 bioavailability. The peptide sequences for LR3 IGF-1 and sheep IGF-1 also differ. To overcome these limitations with LR3 IGF-1, we developed an ovine (sheep) specific recombinant IGF-1 (oIGF-1) and tested its effect on growth in fetal sheep. First, we measured in vitro myoblast proliferation in response to oIGF-1. Second, we examined anabolic signaling pathways from serial skeletal muscle biopsies in fetal sheep that received oIGF-1 or saline infusion for 2 hours. Finally, we measured the effect of fetal oIGF-1 infusion versus saline infusion (SAL) for 1 week on fetal body and organ growth, in vivo myoblast proliferation, skeletal muscle fractional protein synthetic rate, IGFBP expression in skeletal muscle and liver, and IGF-1 signaling pathways in skeletal muscle. Using this approach, we showed that oIGF-1 stimulated myoblast proliferation in vitro. When infused for 1 week, oIGF-1 increased organ growth of the heart, kidney, spleen, and adrenal glands and stimulated skeletal myoblast proliferation compared to SAL without increasing muscle fractional synthetic rate or hindlimb muscle mass. Hepatic and muscular gene expression of IGFBPs one to three was similar between oIGF-1 and SAL. We conclude that oIGF-1 promotes tissue and organ-specific growth in the normal sheep fetus.

High-fat diet-fed ovariectomized mice are susceptible to accelerated subcutaneous tumor growth potentially through adipose tissue inflammation, local insulin-like growth factor release, and tumor associated macrophages.

Background: The association between obesity and colorectal cancer (CRC) risk has been well established. This relationship appears to be more significant in men than in women, which may be attributable to sex hormones. However, controlled animal studies to substantiate these claims and the mechanisms involved are lacking.Materials and Methods: MC38 murine colon adenocarcinoma cells were injected subcutaneously into high-fat diet (HFD) fed male, female and ovariectomized (OVX) female C57BL/6 mice.Results: HFD increased tumor growth (main effect) that was consistent with metabolic perturbations (P < 0.01). HFD OVX mice exhibited the most significant tumor growth compared to HFD male and female mice (p < 0.05) and this was associated with increased subcutaneous adipose tissue (p < 0.05). Further, the subcutaneous adipose tissue depots within HFD OVX mice exhibited more severe macrophage associated inflammation compared to female (P < 0.01), but not male mice. Conditioned media from subcutaneous adipose tissue of HFD OVX contained higher IGF-1 levels compared to male (P < 0.01), but not female mice. Finally, HFD OVX mice had increased M2-like gene expression in their tumor-associated macrophages (TAMs) compared to female mice (P < 0.01).Conclusions: This work provides evidences suggesting adiposity, adipose specific IGF-1, macrophage associated adipose inflammation, and TAMs as potential mechanisms driving obesity-enhanced CRC in females lacking ovarian hormones.

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.

SlyD: A novel epitope-presenting thermostable scaffold for the development of highly specific IGF-1/-2 antibodies

SlyD: A novel epitope-presenting thermostable scaffold for the development of highly specific IGF-1/-2 antibodies

Skeletal Muscle Fiber Size and Gene Expression in the Oldest-Old With Differing Degrees of Mobility.

The oldest-old, in the ninth and tenth decades of their life, represent a population characterized by neuromuscular impairment, which often implies a loss of mobility and independence. As recently documented by us and others, muscle atrophy and weakness are accompanied by an unexpected preservation of the size and contractile function of skeletal muscle fibers. This suggests that, while most fibers are likely lost with their respective motoneurons, the surviving fibers are well preserved. Here, we investigated the mechanisms behind this fiber preservation and the relevance of physical activity, by comparing a group of 6 young healthy controls (YG: 22–28 years) with two groups of oldest-old (81–96 years), one able to walk (OW: n = 6, average 86 years) and one confined to a wheelchair (ONW n = 9, average 88 years). We confirmed previous results of fiber preservation and, additionally, observed a shift in fiber type, toward slow predominance in OW and fast predominance in ONW. Myonuclear density was increased in muscles of ONW, compared to YG and OW, potentially indicative of an ongoing atrophy process. We analyzed, by RT-qPCR, the expression of genes relevant for fiber size and type regulation in a biopsy sample from the vastus lateralis. In all oldest-old both myostatin and IGF-1 expression were attenuated compared to YG, however, in ONW two specific IGF-1 isoforms, IGF-1EA and MGF, demonstrated a further significant decrease compared to OW. Surprisingly, atrogenes (MURF1 and atrogin) expression was also significantly reduced compared to YG and this was accompanied by a close to statistically significantly attenuated marker of autophagy, LC3. Among the determinants of the metabolic fiber type, PGC1α was significantly reduced in both OW and ONW compared to YG, while AMPK was down-regulated only in ONW. We conclude that, in contrast to the shift of the balance in favor of pro-atrophy factors found by other studies in older adults (decreased IGF-1, increase of myostatin, increase of atrogenes), in the oldest-old the pro-atrophy factors also appear to be down-regulated, allowing a partial recovery of the proteostasis balance. Furthermore, the impact of muscle activity, as a consequence of lost or preserved walking ability, is limited.

Cross-species reactive monoclonal antibodies against the extracellular domains of the insulin receptor and IGF1 receptor

Translation across species of immunoassay results is often challenging due to the lack of cross-species reactivity of antibodies. In order to investigate the biology of insulin and IGF1 receptors, we generated new versatile monoclonal assay antibodies using the extracellular domain of the insulin/IGF1 hybrid receptor as the bait protein in the Adimab yeast antibody discovery platform and as the antigen in a rabbit monoclonal antibody platform. The resulting antibody clones were screened for receptor specificity as well as cross-species reactivity to both tissue and cell line derived samples. Using these strategies, we were able to identify highly specific insulin receptor monoclonal antibodies that lack cross-reactivity to the IGF1 receptor using the Adimab platform and a highly specific IGF1 receptor monoclonal antibody that lacks cross-reactivity to the insulin receptor using the rabbit antibody platform. Unlike earlier monoclonal antibodies reported in the literature, these antibodies show cross-species reactivity to the extracellular domains of mouse, rat, pig, and human receptors, indicating that they bind conserved epitopes. Furthermore, the antibodies work well in several different assay formats, including ELISA, flow cytometry, and immunoprecipitation, and therefore provide new tools to study insulin and IGF1 receptor biology with translation across several species and experimental model systems.

Lack of Brain Insulin Receptor Substrate-1 (IRS1) Causes Growth Retardation via Growth Hormone Releasing Hormone

Background and Purpose: We previously revealed that systemic Irs1 deficient mice showed growth retardation, indicating that Irs1 plays an important role in growth. Irs1 is main substrate of not only insulin receptor (IR) but also IGF-1 receptor (IGF-1R) tyrosine kinase. Recently, brain specific IGF-1 receptor knockout mice were reported to become growth impairment. We hypothesized that brain Irs1 may regulate growth via IGF-1. Methods: We generated NIrs1KO mice and analyzed growth related parameter and immunohistochemistry (IHC) study. Result: The body weight of NIrs1KO mice was significantly smaller than control mice. NIrs1KO mice also showed shorter body length and bone length. On the other hand food intake and gene expression of appetite-related neuropeptides (POMC, AgRP and NPY) were not different between two groups. We next confirmed that plasma IGF-1 and growth hormone (GH) levels of NIrs1KO mice were lower than control mice. Hypothalamic GHRH mRNA expression levels of NIrs1KO mice were also lower than those of control mice although hypothalamic somatostatin mRNA expression was not different between two groups. These data strongly suggest that lack of brain Irs1 causes growth retardation via GHRH. IHC study indicated that Irs1 colocalized with GHRH neuron in hypothalamus. We next investigated the IGF-1-induced proliferation in hypothalamic neural cells by using siIrs1. Downregulation of Irs1 significantly inhibited IGF-1-induced neural cell proliferation. Conclusion: Our results suggest that IGF-1-Irs1 pathway promotes the proliferation of GHRH neurons and regulate growth. Disclosure T. Hayashi: None. N. Kubota: None. T. Kubota: None. T. Kadowaki: Consultant; Self; Novo Nordisk A/S, AstraZeneca, Merck Sharp &amp; Dohme Corp.. Research Support; Self; Kissei Pharmaceutical Co., Ltd., Taisho Pharmaceutical Co., Ltd., Sanofi, Kyowa Hakko Kirin Co., Ltd., Novo Nordisk A/S, Astellas Pharma, Daiichi Sankyo Company, Limited, Takeda, Mitsubishi Tanabe Pharma Corporation, Ono Pharmaceutical Co., Ltd., Merck Sharp &amp; Dohme Corp., Nippon Boehringer Ingelheim Co. Ltd.. Speaker's Bureau; Self; Astellas Pharma, AstraZeneca, Merck Sharp &amp; Dohme Corp., Ono Pharmaceutical Co., Ltd., Takeda, Eli Lilly and Company, Nippon Boehringer Ingelheim Co. Ltd., Novo Nordisk A/S.

Synthetic Advances in Insulin-like Peptides Enable Novel Bioactivity.

Insulin is a miraculous hormone that has served a seminal role in the treatment of insulin-dependent diabetes for nearly a century. Insulin resides within in a superfamily of structurally related peptides that are distinguished by three invariant disulfide bonds that anchor the three-dimensional conformation of the hormone. The additional family members include the insulin-like growth factors (IGF) and the relaxin-related set of peptides that includes the so-called insulin-like peptides. Advances in peptide chemistry and rDNA-based synthesis have enabled the preparation of multiple insulin analogues. The translation of these methods from insulin to related peptides has presented unique challenges that pertain to differing biophysical properties and unique amino acid compositions. This Account presents a historical context for the advances in the chemical synthesis of insulin and the related peptides, with division into two general categories where disulfide bond formation is facilitated by native conformational folding or alternatively orthogonal chemical reactivity. The inherent differences in biophysical properties of insulin-like peptides, and in particular within synthetic intermediates, have constituted a central limitation to achieving high yield synthesis of properly folded peptides. Various synthetic approaches have been advanced in the past decade to successfully address this challenge. The use of chemical ligation and metastable amide bond surrogates are two of the more important synthetic advances in the preparation of high quality synthetic precursors to high potency peptides. The discovery and application of biomimetic connecting peptides simplifies proper disulfide formation and the subsequent traceless removal by chemical methods dramatically simplifies the total synthesis of virtually any two-chain insulin-like peptide. We report the application of these higher synthetic yield methodologies to the preparation of insulin-like peptides in support of exploratory in vivo studies requiring a large quantity of peptide. Tangentially, we demonstrate the use of these methods to study the relative importance of the IGF-1 connecting peptide to its biological activity. We report the translation of these finding in search of an insulin analog that might be comparably enhanced by a suitable connecting peptide for interaction with the insulin receptor, as occurs with IGF-1 and its receptor. The results identify a unique receptor site in the IGF-1 receptor from which this enhancement derives. The selective substitution of this specific IGF-1 receptor sequence into the homologous site in the insulin receptor generated a chimeric receptor that was equally capable of signaling with insulin or IGF-1. This novel receptor proved to enhance the potency of lower affinity insulin ligands when they were supplemented with the IGF-1 connecting peptide that similarly enhanced IGF-1 activity at its receptor. The chimeric insulin receptor demonstrated no further enhancement of potency for native insulin when it was similarly prepared as a single-chain analogue with a native IGF-1 connecting peptide. These results suggest a more highly evolved insulin receptor structure where the requirement for an additional structural element to achieve high potency interaction as demonstrated for IGF-1 is no longer required.

Kushenin induces the apoptosis of HCV-infected cells by blocking the PI3K-Akt-mTOR pathway via inhibiting NS5A

With the increased burden induced by HCV, there is an urgent need to develop better-tolerated agents with good safety. In this study, we evaluated the anti-HCV capability of kushenin, as well as the possible mechanism to Huh7.5-HCV cells. The results demonstrated that kushenin significantly inhibited the HCV-RNA level. Similarly, the expression of HCV-specific protein NS5A was also decreased. Molecular docking results displayed that kushenin bonded well to the active pockets of HCV NS5A, further confirming the effects of kushenin on HCV replication. Coimmunoprecipitation assay determined that kushenin suppressed the interaction between PI3K and NS5A in HCV-replicon cells. Furthermore, kushenin exerted an obviously induced function on HCV-replicon cells apoptosis by inhibiting PI3K-Akt-mTOR pathway, which could be ameliorated by the specific activator IGF-1 addition. Taken together, kushenin possesses the ability to inhibit HCV replication, and contributes to the increased apoptosis of HCV-infected cells by blocking the PI3K-Akt-mTOR pathway via inhibiting NS5A. Our results provide important evidence for a better understanding of the pathogenesis of HCV infection, and suggest that kushenin has the potential to treat HCV disease.

Prednisolone reduces the ability of serum to activate the IGF1 receptor in vitro without affecting circulating total or free IGF1

End-point bioassays based on thymidine or sulfate incorporation have demonstrated that glucocorticoid (GC) treatment inhibits serum IGF1 action, but the mechanism is unknown as serum IGF1 concentrations have been reported to either increase or remain unchanged. To investigate whether GC treatment affects the ability of serum to activate the IGF1 receptor (IGF1R) in vitro (i.e. bioactive IGF1), using a specific cell-based IGF1 kinase receptor activation assay. Twenty children with stable asthma (age 7.7-13.8 years) treated for 1 week with 5 mg prednisolone in a randomized, double-blind, placebo-controlled crossover study. Non-fasting serum samples were collected in the afternoon after each 7-day period and assayed for bioactive IGF1, free IGF1, total IGFs, IGF-binding proteins (IGFBPs), and insulin. Prednisolone treatment reduced IGF1 bioactivity by 12.6% from 2.22±0.18 to 1.94±0.15 μg/l (P=0.01) compared with placebo. In contrast, no changes were observed for (μg/l; placebo vs prednisolone) total IGF1 (215±27 vs 212±24), free IGF1 (1.50±0.16 vs 1.43±0.17), total IGF2 (815±26 vs 800±31), IGFBP3 (3140±101 vs 3107±95), IGFBP2 (238±21 vs 220±19), IGFBP1 (32±6 vs 42±10), or IGFBP1-bound IGF1 (24±5 vs 26±7). Insulin remained unchanged as did IGFBP levels as estimated by western ligand blotting. Prednisolone had no direct effects on IGF1R phosphorylation. Our study gives evidence that GC treatment induces a circulating substance that is able to inhibit IGF1R activation in vitro without affecting circulating free or total IGF1. This may be one of the mechanisms by which GC inhibits IGF1 action in vivo. However, the nature of this circulating substance remains to be identified.

Heart Smart Insulin-Like Growth Factor 1

See related article, pp 680–693 The prevalence of obesity, metabolic syndrome, and type 2 diabetes mellitus, and the associated cardiac pathologies are rising to alarming levels. Conventional medical therapies for the prevention and treatment of cardiomyopathy are less effective in patients with these metabolic disorders, and this is attributed, at least in part, to a limited understanding of the cellular and genetic mechanisms responsible for the pathology in the heart. The cause(s) underlying the development of obesity and metabolic syndrome have been attributed to several factors including, but not limited to, consumption of a high-fat diet and are often associated with myocardial contractile and metabolic dysfunction.1 The detrimental effects of high-fat diets on the heart are likely to be multifactorial and include lipotoxicity, abnormal fatty acid metabolism, endothelial dysfunction, impaired calcium handling, mitochondrial dysfunction, and disruption of the insulin signaling pathway. Recent evidence also suggests that a high-fat diet induces epigenetic defects in the heart,2 which could potentially result in an increased risk of cardiac pathologies in offspring. A better understanding of the mechanisms underlying the increased propensity for high-fat diets to induce cardiac dysfunction is necessary to develop treatment strategies. Insulin-like growth factor-1 (IGF-1) plays a role in regulating cell proliferation, differentiation, survival, and metabolism and is produced in many tissues, including the heart. Reduced IGF-1 levels are associated with obesity, cardiovascular disease, atherosclerosis, and diabetes mellitus, whereas elevated IGF-1 has been associated with longevity in humans.3 …

Abstract A93: Correlates of total testosterone and testosterone deficiency in African American men

Abstract Introduction: Elevated serum total testosterone (TT) levels have been associated with increased prostate cancer incidence and mortality faced by African American (AA) men. Testosterone deficiency (TD) is linked to several health outcomes including increased cancer and all-cause mortality. Several studies have examined the relationships between TT levels and biochemical and environmental factors, but few have examined these correlates in AA men. This study evaluated TT levels, TD and their correlates in AA men. Methods: Blood samples were collected from 191 controls recruited from 2000–2003 from the Urology clinic at the Howard University Hospital, along with demographic data, reported alcohol use, and BMI. Measurements of testosterone (total and free), prostate specific antigen (PSA), triglycerides (TG), total cholesterol, HDL, VLDL, LDL, IGF1 and IGFBP3 levels were obtained from the blood. Percentage west African genetic ancestry was determined using a panel of 100 ancestry informative markers. Results: On linear regression, age, HDL, LDL and IGFBP3 levels were associated with TT levels (p&amp;lt; 0.05). However, TT levels were not associated with degree of West African ancestry (p = 0.52). Using multivariate analysis, TD deficiency (TT &amp;lt; 300 ng/dL) was positively associated with TG levels (p &amp;lt; 0.05), alcohol use and elevated BMI (p = 0.018 for both). The highest quartile BMI (BMI &amp;gt; 31) was at 2.48 times higher risk for TD than the lowest quartile (&amp;lt; 25). The correlates of TT levels and risk factors for TD in AA men are similar to the established risk factors in European American men. Citation Information: Cancer Epidemiol Biomarkers Prev 2011;20(10 Suppl):A93.

IGF1-Mediated Osteoblastic Niche Expansion After Marrow Ablation Enhances Long-Term Hematopoietic Stem Cell Engraftment and Hematopoietic Reconstitution After Bone Marrow Transplantation

AbstractAbstract 557The capacity for hematopoietic stem cells (HSCs) to engraft in bone marrow (BM) and reconstitute long-term multilineage hematopoiesis after transplantation depends on their interaction with a specific microenvironment, the stem cell niche. We previously demonstrated a profound reorganization of the marrow endosteal microenvironment after lethal total body irradiation (TBI) of mice that leads to a rapid restoration of the osteoblastic HSC niche, followed by a transient, reversible expansion of this niche. Here, we show that the niche restoration and expansion is driven by a small number of highly proliferative osteoprogenitors via an IGF1 dependent mechanism, that directly facilities long-term hematopoietic stem cell homing and engraftment. At homeostasis, BM osteoblasts (OB) are organized as a single layer of flattened cells at the endosteal surface. Within 3 h of TBI administered to C57BL6 mice, few OB were identified at the endosteal surface. However, by 6 h post-TBI, a new single layer of OB was evident, followed by a marked increase in OB proliferation resulting in multiple layers of cells at the endosteum. The OB proliferation showed half maximal expansion at 24 h post-TBI and maximal expansion at 48 h, at which time the expanded OB constituted significantly more cell tiers than in unirradiated controls (p<0.005). BrdU incorporation/Ki67 expression dual marker studies, conducted over 48 h post-TBI, revealed clusters of highly proliferative cells that expand to repopulate the endosteum and to drive the osteoblastic niche expansion, suggesting a pool of radioresistant osteoprogenitors as the source of the niche restoration and expansion. Real-time qPCR of BM cells harvested after TBI showed an increased gene expression of Sdf1, Pdgfβ, TGFβ, Fgf2, and notably, Igf1, that peaks at 48 h. Using an ELISA, we, similarly, found an increase in protein expression, relative to unirradiated controls, that also peaks at 48 h (SDF1, 2.3-fold increase, p<0.005; PDGFβ, 6.1-fold, p<0.005; TGFβ, 4.4-fold, p<0.005; FGF2, 3.2-fold, p=0.05; IGF1, 5.3-fold, p<0.005). We propose that this extensive niche remodeling, closely correlated with increased expression of highly relevant cytokines, serves to optimize the osteoblastic niche for homing and engraftment of HSCs. To test the hypothesis, we used competitive repopulation secondary transplantation assays to assess the capacity of the osteoblastic niche to foster HSC engraftment. Primary recipients were transplanted with GFP-transgenic BM (3×106 cells/mouse) at 0.5 h, 24 h, or 48 h (maximal niche expansion) after TBI. At 24 h after transplantation, BM cells (representing 12.5% of the total marrow population) harvested from the primary recipients were transplanted into lethally irradiated secondary recipients with 2×105 competitor (unlabeled) BM cells. Secondary recipients, receiving marrow from primary recipients transplanted at 48 h post TBI, showed greater engraftment at 3 (p<0.05), 6 (p<0.001), and 18 (p<0.05) weeks after BMT compared with the 0.5 h and 24 h groups, indicating that 48 h of niche expansion facilitates homing/early engraftment of short- and long-term hematopoietic repopulating cells. To further define the importance of niche expansion and to determine the contribution of IGF1 signaling, we performed a competitive repopulation secondary transplantation assay with and without picropodophyllin (PPP), a specific IGF1 receptor tyrosine kinase inhibitor. Treated mice were either sacrificed for evaluation of niche expansion or transplanted with GFP-transgenic BM cells at 48 h post TBI. The short half-life of PPP (3 h) indicates that the drug will be eliminated prior to transplantation, 36 h after the last PPP dose. Histological analysis of irradiated, PPP-treated mice revealed that the osteoblastic niche was restored but did not expand to multiple layers at 48 h. Secondary recipients, receiving marrow from PPP-treated primary recipients, showed no evidence of short-term or long-term hematopoiesis in contrast to untreated controls (p<0.05). These data indicate that IGF1 mediated effects on the BM stem cell niche are essential for niche expansion and for engraftment of transplanted HSCs. Collectively, our data indicate that IGF1 mediated osteoblastic niche expansion is a pivotal component of HSC homing and engraftment. Targeting niche expansion may enhance HSC engraftment after clinical BMT, especially if HSC dose is limiting. Disclosures:No relevant conflicts of interest to declare.

Targeting the IGF1 axis in cancer proliferation

The IGF network of ligands, cell-surface receptors and IGF-binding proteins has important roles at multiple levels, including the cellular, organ and organism levels. The IGF system mediates growth, differentiation and developmental processes, and is also involved in various metabolic activities. Dysregulation of IGF system expression and action is linked to diverse pathologies, ranging from growth deficits to cancer development. Targeting of the IGF axis emerged in recent years as a promising therapeutic approach in conditions in which the IGF system is involved. Specific IGF1 receptor (IGF1R) targeting, in particular, produced the best experimental and clinical results so far, and generated significant optimism in the field. This review provides a basic analysis of the role of the IGF1R in cancer biology and explores the functional interactions between the IGF signaling pathways and various cancer genes (e.g., oncogenes, tumor suppressors). In addition, we review a number of specific malignancies in which the IGF system is involved and summarize recent data on preclinical and clinical studies employing IGF1R-targeted modalities.

Genetic Mapping of Fixed Phenotypes: Disease Frequency as a Breed Characteristic

Traits that have been stringently selected to conform to specific criteria in a closed population are phenotypic stereotypes. In dogs, Canis familiaris, such stereotypes have been produced by breeding for conformation, performance (behaviors), etc. We measured phenotypes on a representative sample to establish breed stereotypes. DNA samples from 147 dog breeds were used to characterize single nucleotide polymorphism allele frequencies for association mapping of breed stereotypes. We identified significant size loci (quantitative trait loci [QTLs]), implicating candidate genes appropriate to regulation of size (e.g., IGF1, IGF2BP2 SMAD2, etc.). Analysis of other morphological stereotypes, also under extreme selection, identified many additional significant loci. Behavioral loci for herding, pointing, and boldness implicated candidate genes appropriate to behavior (e.g., MC2R, DRD1, and PCDH9). Significant loci for longevity, a breed characteristic inversely correlated with breed size, were identified. The power of this approach to identify loci regulating the incidence of specific polygenic diseases is demonstrated by the association of a specific IGF1 haplotype with hip dysplasia, patella luxation, and pancreatitis.

IGF-1, IGFBP-1, and IGFBP-3 Polymorphisms Predict Circulating IGF Levels but Not Breast Cancer Risk: Findings from the Breast and Prostate Cancer Cohort Consortium (BPC3)

IGF-1 has been shown to promote proliferation of normal epithelial breast cells, and the IGF pathway has also been linked to mammary carcinogenesis in animal models. We comprehensively examined the association between common genetic variation in the IGF1, IGFBP1, and IGFBP3 genes in relation to circulating IGF-I and IGFBP-3 levels and breast cancer risk within the NCI Breast and Prostate Cancer Cohort Consortium (BPC3). This analysis included 6,912 breast cancer cases and 8,891 matched controls (n = 6,410 for circulating IGF-I and 6,275 for circulating IGFBP-3 analyses) comprised primarily of Caucasian women drawn from six large cohorts. Linkage disequilibrium and haplotype patterns were characterized in the regions surrounding IGF1 and the genes coding for two of its binding proteins, IGFBP1 and IGFBP3. In total, thirty haplotype-tagging single nucleotide polymorphisms (htSNP) were selected to provide high coverage of common haplotypes; the haplotype structure was defined across four haplotype blocks for IGF1 and three for IGFBP1 and IGFBP3. Specific IGF1 SNPs individually accounted for up to 5% change in circulating IGF-I levels and individual IGFBP3 SNPs were associated up to 12% change in circulating IGFBP-3 levels, but no associations were observed between these polymorphisms and breast cancer risk. Logistic regression analyses found no associations between breast cancer and any htSNPs or haplotypes in IGF1, IGFBP1, or IGFBP3. No effect modification was observed in analyses stratified by menopausal status, family history of breast cancer, body mass index, or postmenopausal hormone therapy, or for analyses stratified by stage at diagnosis or hormone receptor status. In summary, the impact of genetic variation in IGF1 and IGFBP3 on circulating IGF levels does not appear to substantially influence breast cancer risk substantially among primarily Caucasian postmenopausal women.

Cytokine profiling and in vitro studies of murine bone growth using biological fluids from children with juvenile idiopathic arthritis

Growth retardation in children with chronic inflammatory disease may be partly due to direct effects of pro-inflammatory cytokines on the growth plate and requires further investigation. This study assessed the cytokine concentrations in serum and synovial fluid (SF) in juvenile idiopathic arthritis (JIA), and determined the effect of the biological fluid on cultured murine metatarsal growth. Serum and SF were obtained from four children attending for arthrocentesis (child A, systemic; children B, C and D, oligoarticular). In addition, serum samples were obtained from four more children (children E and F, polyarticular; child G, oligoarticular). Anthropometry, cytokine levels and longitudinal bone growth were assessed. Cytokines were elevated to a variable extent in the samples. Although all serum samples were associated with reduced metatarsal growth, only SF from child A and child B reduced metatarsal growth. Metatarsals treated with child A's SF showed reduced proliferation, reduced proliferative and mineralizing zone width, and increased hypertrophic zone width. Tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta and IL-6 concentrations were elevated in child A's SF. However, SF exposure with neutralizing antibodies to these cytokines or IGF-1 did not improve metatarsal growth. SF and serum JIA samples can impair bone growth at the growth plate. In synovial fluid, the effect is variable but resistant to treatment with IL-1beta, IL-6 and TNF-alpha specific antibodies and IGF-1, suggesting that other factors in this biological fluid may also have an effect on longitudinal growth through IGF-1-independent mechanisms.

Neuroprotective effects of short peptides derived from the Insulin-like growth factor 1

Insulin-like growth factor I (IGF-1) is a peptide synthesized in response to growth hormone stimulation. While most of the circulating IGF-1 comes from the liver, it can also be produced in other tissues and both its expression and processing undergo tissue-specific regulation. The predominant form, IGF-1Ea is a circulating factor while two others, IGF-1Eb and IGF-1Ec (MGF), are mostly expressed in different tissues or in response to various stimuli and show some preferences with respect to the signal transduction pathways they activate. In skeletal muscle specific forms of IGF-1 play a role in development and growth and in addition to these physiological roles IGF-1 functions in the damaged muscle. IGF-1 is also important for the developing and adult brain and can reduce neuronal death caused by different types of injuries. Like many other peptide hormones IGF-1 originates from a precursor pro-hormone that undergoes extensive post-translational modifications. Processing liberates the mature peptide, which acts via the specific IGF-1 receptor but additional short peptides can arise from both N- and C-termini of various IGF-1 isoforms. These derivatives function as autonomous biologically active peptides and extremely potent neuroprotective agents. Their biological effects are independent of the activation of the IGF-1 receptor. Unfortunately, little is known about their mechanism(s) of action. Likewise, the existence of the endogenous production and wider biological effects of these short peptides are uncertain. However, considering the difference in the modes of action it might be possible to dissociate the unwanted and potentially dangerous mitogenic activity of the full-length IGF-1 exerted via its receptor from the neuroprotective effects of short derivatives mediated through different pathways. Such small molecules show good penetration through the blood brain barrier, can be inexpensively manufactured and modified to increase their stability. Therefore, they are good candidates for development into a neuroprotective therapeutic modality.