Modifications of insulin-like growth factor binding proteins and their role in controlling IGF actions

Integrated single-cell and spatial transcriptomics reveals heterogeneity of fibroblast and pivotal genes in psoriasis

Psoriasis, which is one of the most common skin diseases, involves an array of complex immune constituents including T cells, dendritic cells and monocytes. Particularly, the cytokine IL17A, primarily generated by TH17 cells, assumes a crucial function in the etiology of psoriasis. In this study, a comprehensive investigation utilizing bulk RNA analysis, single-cell RNA sequencing, and spatial transcriptomics was employed to elucidate the underlying mechanisms of psoriasis. Our study revealed that there is an overlap between the genes that are differentially expressed in psoriasis patients receiving three anti-IL17A monoclonal antibody drugs and the genes that are differentially expressed in lesion versus non-lesion samples in these patients. Further analysis using single-cell and spatial data from psoriasis samples confirmed the expression of hub genes that had low expressions in psoriasis tissue but were up-regulated after anti-IL17A treatments. These genes were found to be associated with the treatment effects of brodalumab and methotrexate, but not adalimumab, etanercept, and ustekinumab. Additionally, these genes were predominantly expressed in fibroblasts. In our study, fibroblasts were categorized into five clusters. Notably, hub genes exhibited predominant expression in cluster 3 fibroblasts, which were primarily engaged in the regulation of the extracellular matrix and were predominantly located in the reticular dermis. Subsequent analysis unveiled that cluster 3 fibroblasts also established communication with epithelial cells and monocytes via the ANGPTL-SDC4 ligand-receptor configuration, and their regulation was governed by the transcription factor TWIST1. Conversely, cluster 4 fibroblasts, responsible for vascular endothelial regulation, were predominantly distributed in the papillary dermis. Cluster 4 predominantly engaged in interactions with endothelial cells via MDK signals and was governed by the distinctive transcription factor, ERG. By means of an integrated analysis encompassing bulk transcriptomics, single-cell RNA sequencing, and spatial transcriptomics, we have discerned genes and clusters of fibroblasts that potentially contribute to the pathogenesis of psoriasis.

Effect of Four Functional Feed Additives on Growth, Serum Biochemistry, Antioxidant Capacity, Gene Expressions, Histomorphology, Digestive Enzyme Activities and Disease Resistance in Juvenile Olive Flounder, Paralichthys olivaceus

An 8-week feeding trial was executed to evaluate the efficacy of four functional feed additives in replacing antibiotics in juvenile olive flounder, Paralichthys olivaceus, fed with a low-fish-meal diet. A basal diet without feed additives was used as a control (CON); other diets were formulated by supplementing 0.50% taurine (TW), 0.30% peptide (PT), 0.23% mineral water (MW), 0.35% yeast-extracted nucleotides (GRO), 0.35% GRO + 0.50% taurine (GROTW), 0.35% GRO + 0.30% peptide (GROPT) and 0.35% GRO + 0.23% mineral water (GROMW) into the basal diet; in addition, one diet was supplemented with oxytetracycline (OTC) at 0.5% as a positive control. Triplicate groups of 25 fish with an average weight of 5.15 ± 0.06 g (mean ± SD) were fed one of the nine experimental diets. At the end of the feeding trial, the weight gain, specific growth rate and protein efficiency ratio of fish fed the GRO, GROMW, GROPT and GROTW diets were significantly higher than those of fish fed the CON diet (p < 0.05). The feed efficiency of fish fed the GRO, GROMW, GROPT and GROTW diets was significantly higher than that of fish fed the TW and OTC diets. However, the survival, hepatosomatic index, viscerosomatic index and condition factor of fish, as well as their whole-body proximate composition, were not significantly affected by the experimental diets (p > 0.05). The serum glutamic pyruvic transaminase of fish fed the GROPT diet was significantly lower than that of fish fed the CON diet. However, glutamic oxaloacetic transaminase, glucose and total protein were not significantly affected by the experimental diets (p > 0.05). The serum superoxide dismutase activity of fish fed the PT, TW, GRO, GROMW, GROPT and GROTW diets was significantly higher than that of fish fed the CON diet. The lysozyme activity of fish fed the PT, GRO, GROMW, GROPT and GROTW diets was significantly higher than that of fish fed the CON and OTC diets. The myeloperoxidase activity of fish fed the TW, GRO, GROMW, GROPT and GROTW diets was significantly higher than that of fish fed the CON, PT and MW diets (p < 0.05). The flounder growth hormone gene expression of fish fed the TW, GRO, GROMW, GROPT, GROTW and OTC diets was significantly higher than that of fish fed the CON, PT and MW diets (p < 0.05). The interleukin 1β and interleukin 10 gene expressions of fish fed the GRO, GROMW, GROPT and GROTW diets were significantly higher than those of fish fed the CON, PT, TW and MW diets (p < 0.05). Intestinal histology showed a significantly higher villi length for fish fed the GRO, GROMW, GROPT and GROTW diets compared to that of fish fed the CON diet (p < 0.05). Digestive enzyme activities such as trypsin activity were significantly higher in fish fed the GROMW, GROPT and GROTW diets than those in the rest of the diet groups (p < 0.05). Amylase activity in fish fed the MW, GRO, GROMW, GROPT, GROTW and OTC diets was significantly higher than that of fish fed the PT, TW and CON diets (p < 0.05). On the other hand, the lipase activity of fish fed the TW, GRO, GROMW, GROPT and GROTW diets was significantly higher than that of fish fed the CON, PT, MW and OTC diets (p < 0.05). The cumulative survival rate of fish fed the PT, GROTW, GROPT and GROMW diets was significantly higher than that of fish fed the CON, TW and MW diets after thirteen days of the challenge testing. Overall, the results demonstrate that the GRO, GROMW, GROPT and GROTW diets could be beneficial feed additives to replace antibiotics in juvenile olive flounder fed low-fish-meal diets.

Insulin-like growth factor signalling and its significance as a biomarker in fish and shellfish research

The insulin-like growth factor signalling system comprises insulin-like growth factors, insulin-like growth factor receptors and insulin-like growth factor-binding proteins. Along with the growth hormones, insulin-like growth factor signalling is very pivotal in the growth and development of all vertebrates. In fishes, insulin-like growth factors play an important role in osmoregulation, besides the neuroendocrine regulation of growth. Insulin-like growth factor concentration in plasma can assess the growth in fishes and shellfishes and therefore widely applied in nutritional research as an indicator to evaluate the performance of selected nutrients. The present review summarizes the role of insulin-like growth factor signalling in fishes and shellfishes, its significance in aquaculture and in evaluating growth, reproduction and development, and discusses the utility of this system as biomarkers for early indication of growth in aquaculture.

IGF-binding proteins 3 and 4 are regulators of sprouting angiogenesis

PURPOSE

We have previously identified insulin-like growth factor 2 (IGF2) and insulin-like growth factor 1 receptor (IGF1R) as essential proteins for tip cell maintenance and sprouting angiogenesis. In this study, we aim to identify other IGF family members involved in endothelial sprouting angiogenesis.

METHODS

Effects on sprouting were analyzed in human umbilical vein endothelial cells (HUVECs) using the spheroid-based sprouting model, and were quantified as mean number of sprouts per spheroid and average sprout length. RNA silencing technology was used to knockdown gene expression. Recombinant forms of the ligands (IGF1 and IGF2, insulin) and the IGF-binding proteins (IGFBP) 3 and 4 were used to induce excess effects. Effects on the tip cell phenotype were analyzed by measuring the fraction of CD34⁺ tip cells using flow cytometry and immunohistochemistry in a 3D angiogenesis model. Experiments were performed in the presence and absence of serum.

RESULTS

Knockdown of IGF2 inhibited sprouting in HUVECs, in particular when cultured in the absence of serum, suggesting that components in serum influence the signaling of IGF2 in angiogenesis in vitro. We then determined the effects of IGFBP3 and IGFBP4, which are both present in serum, on IGF2-IGF1R signaling in sprouting angiogenesis in the absence of serum: knockdown of IGFBP3 significantly reduced sprouting angiogenesis, whereas knockdown of IGFBP4 resulted in increased sprouting angiogenesis in both flow cytometry analysis and immunohistochemical analysis of the 3D angiogenesis model. Other IGF family members except INSR did not affect IGF2-IGF1R signaling.

CONCLUSIONS

Serum components and IGF binding proteins regulate IGF2 effects on sprouting angiogenesis. Whereas IGFBP3 acts as co-factor for IGF2-IGF1R binding, IGFBP4 inhibits IGF2 signaling.

Insulin-like growth factor binding protein-1 predicts preterm premature rupture of membranes in twin pregnancies

PURPOSE

Mechanisms leading to preterm premature rupture of membranes (PPROM) remain incompletely defined. Based on the elevated occurrence of PPROM in twin gestations and recent studies of the involvement of insulin-like growth factor binding protein-1 (IGFBP-1) in the inhibition of collagen production we hypothesized that serum IGFBP-1 levels might be predictive of susceptibility to PPROM in women with twins.

METHODS

In this prospective study peripheral blood was obtained from 58 women with twin gestations prior to 20 weeks gestation and sera analyzed by ELISA for concentrations of IGFBP-1. Demographic and clinical outcome data were subsequently obtained and associations between IGFBP-1 and PPROM were analyzed by the Mann-Whitney test and receiver operator curve (ROC) analysis.

RESULTS

Eight of our subjects developed PPROM. They did not differ from the other women in demographics, medical history or current pregnancy outcome parameters. However, median IGFBP-1 levels were higher in women who subsequently developed PPROM (59.3 ng/ml) than in the other women (46.6 ng/ml) (p = 0.042). Using a cutoff value of 53.9 ng/ml the circulating IGFBP-1 level predicted development of PPROM with a sensitivity of 74%, specificity of 75%, a negative predictive value of 97% and a positive predictive value of 20%.

CONCLUSIONS

Pending validation in larger studies the findings suggest that determination of serum IGFBP-1 levels in women with twin pregnancies may predict the later development of PPROM.

Unique Associations between Insulin-Like Growth Factor Binding Protein-1, Insulin-Like Growth Factor-1 and T Cell Immunoglobulin Mucin 3 in Successful Twin Pregnancies Conceived with Donor Oocytes

Background and Objectives: To investigate if pregnancies conceived using an oocyte donor necessitate an alteration in immune regulation, we compared concentrations of insulin-like growth factor binding protein (IGFBP)-1, insulin-like growth factor (IGF)-1 and T cell immunoglobulin mucin-3 (Tim-3) in women with ongoing successful twin pregnancies conceived spontaneously, using assisted reproductive technologies that utilized homologous oocytes or with donor oocytes. Differences in levels of these immune modulatory proteins may be magnified and easier to detect in twin as compared to singleton pregnancies. Methods: In this prospective study IGFBP-1 and IGF-1 were measured in sera and Tim-3 in lysates of peripheral blood mononuclear cells (PBMCs) by ELISA. Results: Median IGFBP-1 levels were lower in women with donor oocytes (41.4 ng/ml) as compared to those with a spontaneous conception (51.2 ng/mL) or who conceived with various assisted reproduction protocols using homologous oocytes (52.4 ng/mL) (p < 0.001). IGF-1 and Tim-3 levels were comparable in each group. The IGFBP-1 level was inversely correlated to the IGF-1 concentration only in women with donor oocytes (p = 0.032). IGFBP-1 and Tim-3 levels were similarly negatively correlated in the donor oocyte group (p = 0. 012). Women in the assisted reproduction group who conceived following intracytoplasmic sperm injection were the only other group in which IGFBP-1 and Tim-3 were negatively correlated (p = 0.018). Conclusions: Down-regulation of IGFBP-1 production in pregnancies conceived with donor oocytes may reduce the extent of pro-inflammatory immunity and contribute to successful outcome in totally allogeneic pregnancies.

Ca2+ concentration-dependent premature death of igfbp5a-/- fish reveals a critical role of IGF signaling in adaptive epithelial growth

The phenotype gap is a challenge for genetically dissecting redundant endocrine signaling pathways, such as the six isoforms in the insulin-like growth factor binding protein (IGFBP) family. Although overexpressed IGFBPs can inhibit or potentiate IGF actions or have IGF-independent actions, mutant mice lacking IGFBP-encoding genes do not exhibit major phenotypes. We found that although zebrafish deficient in igfbp5a did not show overt phenotypes when raised in Ca²⁺-rich solutions, they died prematurely in low Ca²⁺ conditions. A group of epithelial cells expressing igfbp5a take up Ca²⁺ and proliferate under low Ca²⁺ conditions because of activation of IGF signaling. Deletion of igfbp5a blunted low Ca²⁺ stress-induced IGF signaling and impaired adaptive proliferation. Reintroducing zebrafish Igfbp5a, but not its ligand binding-deficient mutant, restored adaptive proliferation. Similarly, adaptive proliferation was restored in zebrafish lacking igfbp5a by expression of human IGFBP5, but not two cancer-associated IGFBP5 mutants. Knockdown of IGFBP5 in human colon carcinoma cells resulted in reduced IGF-stimulated cell proliferation. These results reveal a conserved mechanism by which a locally expressed Igfbp regulates organismal Ca²⁺ homeostasis and survival by activating IGF signaling in epithelial cells and promoting their proliferation in Ca²⁺-deficient states. These findings underscore the importance of physiological context when analyzing loss-of-function phenotypes of endocrine factors.

Increased Concentrations of Insulin-Like Growth Factor Binding Protein (IGFBP)-2, IGFBP-3, and IGFBP-4 Are Associated With Fetal Mortality in Pregnant Cows

Insulin-like growth factors (IGFs) play a critical role in fetal growth, and components of the IGF system have been associated with fetal growth restriction in women. In human pregnancy, the proteolytic cleavage of insulin-like growth factor binding proteins (IGFBPs), particularly IGFBP-4, releases free IGF for respective action at the tissue level. The aim of the present study was to determine IGFBP-2, IGFBP-3, and IGFBP-4 concentrations by Western ligand blotting during pregnancy until day 100 in cows and to compare these concentrations with those of non-pregnant cows and cows undergoing embryonic/fetal mortality. Therefore, two study trials (I and II) and an in vitro study were conducted. In study I, 43 cows were not pregnant, 34 cows were pregnant, and 4 cows were undergoing fm. In study II, 500 cows were examined, and 7 cases of pregnancy loss between days 24-27 and 34-37 after artificial insemination (AI, late embryonic mortality; em) and 8 cases of pregnancy loss between days 34-37 and 54-57 after AI (late embryonic mortality and early fetal mortality; em/fm) were defined from the analyses of 30 pregnant and 20 non-pregnant cows randomly selected for insulin-like growth factor 1 and IGFBP analyses. In vitro serum from pregnant (n = 3) and non-pregnant (n = 3) cows spiked after incubation with recombinant human (rh) IGFBP-4 for 24 h, and IGFBP-4 levels were analyzed before and after incubation to detect proteolytic degradation. The IGFBP-2, -3, and -4 concentrations did not decline during early pregnancy in cows, while IGFBP-4 concentrations were comparable between pregnant and non-pregnant cows, irrespective of low proteolytic activity, which was also demonstrated in cows. Interestingly, cows with em or fm showed distinct IGFBP patterns. The IGFBP-2 and -3 concentrations were higher (P < 0.05) in cows with fm compared to pregnant. The IGFBP-4 levels were significantly higher in cows developing fm. Thus, distinct differences in the circulating IGFBP concentrations could be associated with late embryonic and early fetal losses in cattle.

IGF-1 modulates gene expression of proteins involved in inflammation, cytoskeleton, and liver architecture

Even though the liver synthesizes most of circulating IGF-1, it lacks its receptor under physiological conditions. However, according to previous studies, a damaged liver expresses the receptor. For this reason, herein, we examine hepatic histology and expression of genes encoding proteins of the cytoskeleton, extracellular matrix, and cell-cell molecules and inflammation-related proteins. A partial IGF-1 deficiency murine model was used to investigate IGF-1's effects on liver by comparing wild-type controls, heterozygous igf1^+/-, and heterozygous mice treated with IGF-1 for 10 days. Histology, microarray for mRNA gene expression, RT-qPCR, and lipid peroxidation were assessed. Microarray analyses revealed significant underexpression of igf1 in heterozygous mice compared to control mice, restoring normal liver expression after treatment, which then normalized its circulating levels. IGF-1 receptor mRNA was overexpressed in Hz mice liver, while treated mice displayed a similar expression to that of the controls. Heterozygous mice showed overexpression of several genes encoding proteins related to inflammatory and acute-phase proteins and underexpression or overexpression of genes which coded for extracellular matrix, cytoskeleton, and cell junction components. Histology revealed an altered hepatic architecture. In addition, liver oxidative damage was found increased in the heterozygous group. The mere IGF-1 partial deficiency is associated with relevant alterations of the hepatic architecture and expression of genes involved in cytoskeleton, hepatocyte polarity, cell junctions, and extracellular matrix proteins. Moreover, it induces hepatic expression of the IGF-1 receptor and elevated acute-phase and inflammation mediators, which all resulted in liver oxidative damage.

Effects of Growth Hormone on Bone

PURPOSE

Describe the effects of growth hormone (GH) and insulin-like growth factor 1 (IGF-1) on the skeleton.

FINDINGS

The GH and IGF-1 axis has pleiotropic effects on the skeleton throughout the lifespan by influencing bone formation and resorption. GH deficiency leads to decreased bone turnover, delayed statural growth in children, low bone mass, and increased fracture risk in adults. GH replacement improves adult stature in GH deficient children, increases bone mineral density (BMD) in adults, and helps to optimize peak bone acquisition in patients, during the transition from adolescence to adulthood, who have persistent GH deficiency. Observational studies suggest that GH replacement may mitigate the excessive fracture risk associated with GH deficiency. Acromegaly, a state of GH and IGF-1 excess, is associated with increased bone turnover and decreased BMD in the lumbar spine observed in some studies, particularly in patients with hypogonadism. In addition, patients with acromegaly appear to be at an increased risk of morphometric-vertebral fractures, especially in the presence of active disease or concurrent hypogonadism. GH therapy also has beneficial effects on statural growth in several conditions characterized by GH insensitivity, including chronic renal failure, Turner syndrome, Prader-Willi syndrome, postnatal growth delay in patients with intrauterine growth retardation who do not demonstrate catchup growth, idiopathic short stature, short stature homeobox-containing (SHOX) gene mutations, and Noonan syndrome.

SUMMARY

GH and IGF-1 have important roles in skeletal physiology, and GH has an important therapeutic role in both GH deficiency and insensitivity states.

Proteomic analysis of human vitreous humor

Background

The vitreous humor is a transparent, gelatinous mass whose main constituent is water. It plays an important role in providing metabolic nutrient requirements of the lens, coordinating eye growth and providing support to the retina. It is in close proximity to the retina and reflects many of the changes occurring in this tissue. The biochemical changes occurring in the vitreous could provide a better understanding about the pathophysiological processes that occur in vitreoretinopathy. In this study, we investigated the proteome of normal human vitreous humor using high resolution Fourier transform mass spectrometry.

Results

The vitreous humor was subjected to multiple fractionation techniques followed by LC-MS/MS analysis. We identified 1,205 proteins, 682 of which have not been described previously in the vitreous humor. Most proteins were localized to the extracellular space (24%), cytoplasm (20%) or plasma membrane (14%). Classification based on molecular function showed that 27% had catalytic activity, 10% structural activity, 10% binding activity, 4% cell and 4% transporter activity. Categorization for biological processes showed 28% participate in metabolism, 20% in cell communication and 13% in cell growth. The data have been deposited to the ProteomeXchange with identifier PXD000957.

Conclusion

This large catalog of vitreous proteins should facilitate biomedical research into pathological conditions of the eye including diabetic retinopathy, retinal detachment and cataract.

Regulation of skeletal muscle growth in fish by the growth hormone--insulin-like growth factor system

The growth hormone (GH)-insulin-like growth factor (IGF) system is the key promoter of growth in vertebrates; however, how this system modulates muscle mass in fish is just recently becoming elucidated. In fish, the GH induces muscle growth by modulating the expression of several genes belonging to the myostatin (MSTN), atrophy, GH, and IGF systems as well as myogenic regulatory factors (MRFs). The GH controls the expression of igf1 via Janus kinase 2 (JAK2)/signal transducers and activators of the transcription 5 (STAT5) signaling pathway, but it seems that it is not the major regulator. These mild effects of the GH on igf1 expression in fish muscle seem to be related with the presence of higher contents of truncated GH receptor1 (tGHR1) than full length GHR (flGHR1). IGFs in fish stimulate myogenic cell proliferation, differentiation, and protein synthesis through the MAPK/ERK and PI3K/AKT/TOR signaling pathways, concomitant with abolishing protein degradation and atrophy via the PI3K/AKT/FOXO signaling pathway. Besides these signaling pathways control the expression of several genes belonging to the atrophy and IGF systems. Particularly, IGFs and amino acid control the expression of igf1, thus, suggesting other of alternative signaling pathways regulating the transcription of this growth factor. The possible role of IGF binding proteins (IGFBPs) and the contribution of muscle-derived versus hepatic-produced IGF1 on fish muscle growth is also addressed. Thus, a comprehensive overview on the GH-IGF system regulating fish skeletal muscle growth is presented, as well as perspectives for future research in this field.

A twenty-first century cancer epidemic caused by obesity: the involvement of insulin, diabetes, and insulin-like growth factors

Obesity has reached epidemic proportions in the developed world. The progression from obesity to diabetes mellitus type 2, via metabolic syndrome, is recognised, and the significant associated increase in the risk of major human cancers acknowledged. We review the molecular basis of the involvement of morbidly high concentrations of endogenous or therapeutic insulin and of insulin-like growth factors in the progression from obesity to diabetes and finally to cancer. Epidemiological and biochemical studies establish the role of insulin and hyperinsulinaemia in cancer risk and progression. Insulin-like growth factors, IGF-1 and IGF-2, secreted by visceral or mammary adipose tissue have significant paracrine and endocrine effects. These effects can be exacerbated by increased steroid hormone production. Structural studies elucidate how each of the three ligands, insulin, IGF-1, and IGF-2, interacts differently with isoforms A and B of the insulin receptor and with type I IGF receptor and explain how these protagonists contribute to diabetes-associated cancer. The above should inform appropriate treatment of cancers that arise in obese individuals and in those with diabetes mellitus type 2. Novel drugs that target the insulin and insulin-like growth factor signal transduction pathways are in clinical trial and should be effective if appropriate biomarker-informed patient stratification is implemented.

Human conditions of insulin-like growth factor-I (IGF-I) deficiency

Insulin-like growth factor I (IGF-I) is a polypeptide hormone produced mainly by the liver in response to the endocrine GH stimulus, but it is also secreted by multiple tissues for autocrine/paracrine purposes. IGF-I is partly responsible for systemic GH activities although it possesses a wide number of own properties (anabolic, antioxidant, anti-inflammatory and cytoprotective actions). IGF-I is a closely regulated hormone. Consequently, its logical therapeutical applications seems to be limited to restore physiological circulating levels in order to recover the clinical consequences of IGF-I deficiency, conditions where, despite continuous discrepancies, IGF-I treatment has never been related to oncogenesis. Currently the best characterized conditions of IGF-I deficiency are Laron Syndrome, in children; liver cirrhosis, in adults; aging including age-related-cardiovascular and neurological diseases; and more recently, intrauterine growth restriction. The aim of this review is to summarize the increasing list of roles of IGF-I, both in physiological and pathological conditions, underlying that its potential therapeutical options seem to be limited to those proven states of local or systemic IGF-I deficiency as a replacement treatment, rather than increasing its level upper the normal range.

Differences in gene expression between strabismic and normal human extraocular muscles

PURPOSE

Strabismic extraocular muscles (EOMs) differ from normal EOMs in structural and functional properties, but the gene expression profile of these two types of EOM has not been examined. Differences in gene expression may inform about causes and effects of the strabismic condition in humans.

METHODS

EOM samples were obtained during corrective surgery from patients with horizontal strabismus and from deceased organ donors with normal EOMs. Microarrays and quantitative PCR identified significantly up- and down-regulated genes in EOM samples. Analysis was performed on probe sets with more than 3-fold differential expression between normal and strabismic samples, with an adjusted P value of ≤ 0.05.

RESULTS

Microarray analysis showed that 604 genes in these samples had significantly different expression. Expression predominantly was upregulated in genes involved in extracellular matrix structure, and down-regulated in genes related to contractility. Expression of genes associated with signaling, calcium handling, mitochondria function and biogenesis, and energy homeostasis also was significantly different between normal and strabismic EOM. Skeletal muscle PCR array identified 22 (25%) of 87 muscle-specific genes that were significantly down-regulated in strabismic EOMs; none was significantly upregulated.

CONCLUSIONS

Differences in gene expression between strabismic and normal human EOMs point to a relevant contribution of the peripheral oculomotor system to the strabismic condition. Decreases in expression of contractility genes and increases of extracellular matrix-associated genes indicate imbalances in EOM structure. We conclude that gene regulation of proteins fundamental to contractile mechanics and extracellular matrix structure is involved in pathogenesis and/or consequences of strabismus, suggesting potential novel therapeutic targets.

Expression of a protease-resistant insulin-like growth factor-binding protein-4 inhibits tumour growth in a murine model of breast cancer

Background:

Insulin-like growth factor 1 (IGF1) promotes breast cancer and disease progression. Bioavailability of IGF1 is modulated by IGF-binding proteins (IGFBPs). IGFBP4 inhibits IGF1 activity but cleavage by pregnancy-associated plasma protein-A (PAPP-A) protease releases active IGF1.

Methods:

Expression of IGF pathway components and PAPP-A was assessed by western blot or RT–PCR. IGFBP4 (dBP4) resistant to PAPP-A cleavage, but retaining IGF-binding capacity, was used to block IGF activity in vivo. 4T1.2 mouse mammary adenocarcinoma cells transfected with empty vector, vector expressing wild-type IGFBP4 or vector expressing dBP4 were implanted in the mammary fat pad of BALB/c mice and tumour growth was assessed. Tumour angiogenesis and endothelial cell apoptosis were assessed by immunohistochemistry.

Results:

4T1.2 cells expressed the IGF1R receptor and IGFBP4. PAPP-A was expressed within mammary tumours but not by 4T1.2 cells. Proliferation and vascular endothelial growth factor (VEGF) production by 4T1.2 cells was increased by IGF1(E3R) (recombinant IGF1 resistant to binding by IGFBPs) but not by wild-type IGF1. IGF1-stimulated microvascular endothelial cell proliferation was blocked by recombinant IGFBP4. 4T1.2 tumours expressing dBP4 grew significantly more slowly than controls or tumours expressing wild-type IGFBP4. Inhibition of tumour growth by dBP4 was accompanied by the increased endothelial cell apoptosis.

Conclusion:

Protease-resistant IGFBP4 blocks IGF activity, tumour growth and angiogenesis .

Temporal and spatial expression of IGF-I and IGFBP-1 during acute-phase response induced by localized inflammation in rats

OBJECTIVE

The acute-phase response (APR), a cytokine-induced defense reaction of the body that enhances the innate immunity mechanisms directed to eliminate the noxious agent and restrict the area of damage, is accompanied by numerous alterations of the IGF axis. The liver is a central organ of both the IGF system and the APR because it releases most of IGF-I and IGFBP-1 in the circulation and is the main target organ for acute-phase-cytokines such as IL-6.

METHODS

In the current work the expression of IGF-I and IGFBP-1 was studied in the liver and extrahepatic tissues in a rat model of localized inflammation induced by intramuscular injection of turpentine oil (TO). The mRNA expression of IGF-I and IGFBP-1 was determined by Northern blot analysis and quantitative RT-PCR. Circulating levels of IGF-I and IGFBP-1 were evaluated by radioimmunoassay and [(125)I]-IGF-I ligand blotting, respectively.

RESULTS

Administration of TO to the rats led to a significant reduction of IGF-I gene expression in the liver and spleen. These changes were accompanied by a reduction of serum IGF-I concentrations to approximately 50% of levels observed in control rats. In contrast to IGF-I, IGFBP-1 mRNA expression was rapidly elevated in the livers of TO-treated rats. IGFBP-1 transcripts were already detectable at 30 min after TO injection and reached their maximal levels by 6h. IGFBP-1 gene expression was also increased in the kidneys. This elevation, however, was delayed and less prominent than in the liver.

CONCLUSIONS

Our data demonstrate that localized inflammation induced by intramuscular TO injection is accompanied not only by decreased IGF-I but also by increased IGFBP-1 gene expression explaining at least in part the catabolic changes of metabolism observed during the acute-phase response.

Multifunctional roles of insulin-like growth factor binding protein 5 in breast cancer

The insulin-like growth factor axis, which has been shown to protect cells from apoptosis, plays an essential role in normal cell physiology and in cancer development. The family of insulin-like growth factor binding proteins (IGFBPs) has been shown to have a diverse spectrum of functions in cell growth, death, motility, and tissue remodeling. Among the six IGFBP family members, IGFBP-5 has recently been shown to play an important role in the biology of breast cancer, especially in breast cancer metastasis; however, the exact mechanisms of action remain obscure and sometimes paradoxical. An in-depth understanding of IGFBP-5 would shed light on its potential role as a target for breast cancer therapeutics.

Diminished growth and enhanced glucose metabolism in triple knockout mice containing mutations of insulin-like growth factor binding protein-3, -4, and -5

IGF-I and IGF-II are essential regulators of mammalian growth, development and metabolism, whose actions are modified by six high-affinity IGF binding proteins (IGFBPs). New lines of knockout (KO) mice lacking either IGFBP-3, -4, or -5 had no apparent deficiencies in growth or metabolism beyond a modest growth impairment (approximately 85-90% of wild type) when IGFBP-4 was eliminated. To continue to address the roles of these proteins in whole animal physiology, we generated combinational IGFBP KO mice. Mice homozygous for targeted defects in IGFBP-3, -4, and -5 remain viable and at birth were the same size as IGFBP-4 KO mice. Unlike IGFBP-4 KO mice, however, the triple KO mice became significantly smaller by adulthood (78% wild type) and had significant reductions in fat pad accumulation (P < 0.05), circulating levels of total IGF-I (45% of wild type; P < 0.05) and IGF-I bioactivity (37% of wild type; P < 0.05). Metabolically, triple KO mice showed normal insulin tolerance, but a 37% expansion (P < 0.05) of beta-cell number and significantly increased insulin secretion after glucose challenge, which leads to enhanced glucose disposal. Finally, triple KO mice demonstrated a tissue-specific decline in activation of the Erk signaling pathway as well as weight of the quadriceps muscle. Taken together, these data provide direct evidence for combinatorial effects of IGFBP-3, -4, and -5 in both metabolism and at least some soft tissues and strongly suggest overlapping roles for IGFBP-3 and -5 in maintaining IGF-I-mediated postnatal growth in mice.

Insulin-like growth factor signaling in fish

The insulin-like growth factor (IGF) system plays a central role in the neuroendocrine regulation of growth in all vertebrates. Evidence from studies in a variety of vertebrate species suggest that this growth factor complex, composed of ligands, receptors, and high-affinity binding proteins, evolved early during vertebrate evolution. Among nonmammalian vertebrates, IGF signaling has been studied most extensively in fish, particularly teleosts of commercial importance. The unique life history characteristics associated with their primarily aquatic existence has fortuitously led to the identification of novel functions of the IGF system that are not evident from studies in mammals and other tetrapod vertebrates. Furthermore, the emergence of the zebrafish as a preferred model for development genetics has spawned progress in determining the requirements for IGF signaling during vertebrate embryonic development. This review is intended as a summary of our understanding of IGF signaling, as revealed through research into the expression, function, and evolution of IGF ligands, receptors, and binding proteins in fish.

Global uterine genomics in vivo: microarray evaluation of the estrogen receptor alpha-growth factor cross-talk mechanism

Cross-talk between growth factor receptors and the estrogen receptor (ER) has been proposed as a signaling mechanism in estrogen target tissues, with ER(alpha) as a direct target of growth factor receptor-activated signals, leading to regulation of estrogen target genes and estrogen-like biological responses to growth factors. We evaluated whether global genomic changes in the mouse uterus in response to epidermal growth factor or IGF-I mimic those of estradiol (E2), reflecting the cross-talk mechanism. Overlapping responses to growth factors and E2 were expected in the wild type (WT) whereas no response was expected in mice lacking ER(alpha) (ER(alpha) knockout). Surprisingly, although most of the E2 response in the WT also occurred after growth factor treatment, some genes were induced only by E2. Second, although E2 did not induce gene changes in the ER(alpha) knockout, the growth factor response was almost indistinguishable from that of the WT. Differences in response of some genes to IGF-I or epidermal growth factor indicated selective regulation mechanisms, such as phosphatidylinositol 3-kinase or MAPK-dependent responses. The robust ER(alpha)-independent genomic response to growth factor observed here is surprising considering that the biological growth response is ER(alpha) dependent. We propose two mechanisms as alternatives to the cross-talk mechanism for uterine gene regulation. First, E2 increases uterine growth factors, which activate downstream signaling cascades, resulting in gene regulation. Second, growth factors and estrogen regulate similar genes. Our results suggest that the estrogen response in the uterus involves E2-specific ER(alpha)-mediated responses as well as responses resulting from convergence of growth factor and ER-initiated activities.

Skeletal muscle cell hypertrophy induced by inhibitors of metalloproteases; myostatin as a potential mediator

Cell growth and differentiation are controlled in many tissues by paracrine factors, which often require proteolytic processing for activation. Metalloproteases of the metzincin family, such as matrix metalloproteases and ADAMs, recently have been shown to be involved in the shedding of growth factors, cytokines, and receptors. In the present study, we show that hydroxamate-based inhibitors of metalloproteases (HIMPs), such as TAPI and BB-3103, increase the fusion of C(2)C(12) myoblasts and provoke myotube hypertrophy. HIMPs did not seem to effect hypertrophy via proteins that have previously been shown to regulate muscle growth in vitro, such as insulin-like growth factor-I, calcineurin, and tumor necrosis factor-alpha. Instead, the proteolytic maturation of myostatin (growth differentiation factor-8) seemed to be reduced in C(2)C(12) cells treated with HIMPs, as suggested by the presence of nonprocessed myostatin precursor only in hypertrophic myotubes. Myostatin is a known negative regulator of skeletal muscle growth, belonging to the transforming growth factor-beta/bone morphogenetic protein superfamily. These results indicate that metalloproteases are involved in the regulation of skeletal muscle growth and differentiation, that the proteolytic maturation of myostatin in C(2)C(12) cells may be directly or indirectly linked to the activity of some unidentified HIMP-sensitive metalloproteases, and that the lack of myostatin processing on HIMP treatment may be a mediator of myotube hypertrophy in this in vitro model.

Serum insulin-like growth factor binding proteins (IGFBPs) as markers for anabolic/catabolic condition in fishes

In fishes as well as in all vertebrates in which it has been assessed, physiological shifts toward catabolism (e.g. such as during food deprivation) are consistently associated with elevations in the serum levels of at least one (often two in fishes) IGFBP in the < or =31-kDa size range. In mammals, 30-kDa IGFBP-1 is strongly up-regulated under catabolic circumstances, and it plays an important physiological role by sequestering IGF peptides to inhibit energy-expensive growth until conditions are more favorable (e.g. with resumed feeding). Similarly in fishes, it has been found that when the < or =31-kDa IGFBPs are elevated in serum, somatic growth is inhibited, suggesting a similar growth-inhibitory role of these proteins to that of mammalian IGFBP-1. Three different experimentally-induced catabolic states in fishes are compared in this paper: fasting; insulin-dependent diabetes mellitus (IDDM); and stress. A strong relationship between elevated serum cortisol concentrations and the presence of IGFBPs in each case is noted, and the utility of serum IGFBP measurement to serve as an effective indicator (marker) of catabolic condition in fishes is discussed.

Primate mammary gland insulin-like growth factor system: cellular localization and regulation by sex steroids

BACKGROUND

Insulin-like growth factor 1 (IGF1) plays a critical role in estrogen-induced uterine proliferation, but it is unclear whether this estromedin function occurs in other estrogen-sensitive tissues such as the mammary gland. To elucidate this possibility, we investigated the cellular localization and hormonal regulation of mRNAs for IGF1 and 2, their cognate receptors (IGF1R, IGF2R), and IGF binding proteins 2-5 (BPs 2-5) in the rhesus monkey mammary gland.

METHODS

Ovariectomized monkeys were treated with placebo, estradiol (E2), and E2 plus progesterone (E2/P4) for 3 days, after which mammary tissue was harvested for in situ hybridization and immunohistochemical analyses.

RESULTS

IGF1 and IGF2 mRNA levels were significantly increased and BP2 mRNA decreased by E2 and by E2/P4 treatment. IGF1R mRNA was increased by combined E2/P treatment but not by E2 alone. BP5 mRNA was decreased by E2/P4. No differences in IGF2R, BP3, and BP4 mRNA levels were detected in any treatment group. Mammary IGF1 and IGF2 mRNA levels were both positively correlated with local epithelial proliferation, assessed by immunodetection of the proliferation-specific antigen, Ki67.IGF1 and IGF1R expression were negatively correlated with local programmed cell death, as assessed by the in situ TUNEL method. In contrast, BP2 expression was negatively correlated with epithelial proliferation and positively correlated with programmed cell death. IGF2R, BP3, BP4, and BP5 levels were not significantly correlated with either proliferation or death.

CONCLUSIONS

Thus, E2-induced proliferation is associated with upregulation of both IGF1 and IGF2 expression and downregulation of BP2 expression. These data suggest that the local mammary IGF system is involved in sex steroid-induced mammary epithelial cell hyperplasia.

Myofibroblasts. I. Paracrine cells important in health and disease

Myofibroblasts are a unique group of smooth-muscle-like fibroblasts that have a similar appearance and function regardless of their tissue of residence. Through the secretion of inflammatory and anti-inflammatory cytokines, chemokines, growth factors, both lipid and gaseous inflammatory mediators, as well as extracellular matrix proteins and proteases, they play an important role in organogenesis and oncogenesis, inflammation, repair, and fibrosis in most organs and tissues. Platelet-derived growth factor (PDGF) and stem cell factor are two secreted proteins responsible for differentiating myofibroblasts from embryological stem cells. These and other growth factors cause proliferation of myofibroblasts, and myofibroblast secretion of extracellular matrix (ECM) molecules and various cytokines and growth factors causes mobility, proliferation, and differentiation of epithelial or parenchymal cells. Repeated cycles of injury and repair lead to organ or tissue fibrosis through secretion of ECM by the myofibroblasts. Transforming growth factor-beta and the PDGF family of growth factors are the key factors in the fibrotic response. Because of their ubiquitous presence in all tissues, myofibroblasts play important roles in various organ diseases and perhaps in multisystem diseases as well.