Insulin-like Growth Factor Binding Protein-3 mRNA Research Articles

Lysophosphatidic acid enhanced the angiogenic capability of human chondrocytes by regulating Gi/NF-kB-dependent angiogenic factor expression.

Lysophosphatidic acid (LPA) has been found to mediate myeloid differentiation, stimulate osteogenesis, alter cell proliferation and migration, and inhibit apoptosis in chondrocytes. The effect of LPA on the angiogenic capability of chondrocytes is not clear. This study aimed to investigate its effect on the angiogenic capability of human chondrocytes and the underlying mechanism of these effects. Human chondrocyte cell line, CHON-001, commercialized human chondrocytes (HC) derived from normal human articular cartilage, and human vascular endothelial cells (HUVECs) were used as cell models in this study. The angiogenic capability of chondrocytes was determined by capillary tube formation, monolayer permeability, cell migration, and cell proliferation. An angiogenesis protein array kit was used to evaluate the secretion of angiogenic factors in conditioned medium. Angiogenin, insulin-like growth factor-binding protein 1 (IGFBP-1), interleukin (IL)-8, monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinase (MMP)-9, and vascular endothelial growth factor (VEGF) mRNA and protein expressions were evaluated by Q-RT-PCR and EIA, respectively. LPA receptor (LPAR) expression was determined by RT-PCR. Signaling pathways were clarified using inhibitors, Western blot analysis, and reporter assays. The LPA treatment promoted the angiogenic capability of CHON-001 cells and HC, resulting in enhanced HUVEC capillary tube formation, monolayer permeability, migration, and cell growth. Angiogenin, IGFBP-1, IL-8, MCP-1, MMP-9, and VEGF mRNA and protein expressions were significantly enhanced in LPA-treated chondrocytes. LPA2, 3, 4 and 6 were expressed in CHON-001 and HC cells. Pretreatment with the Gi/o type G protein inhibitor, pertussis toxin (PTX), and the NF-kB inhibitor, PDTC, significantly inhibited LPA-induced angiogenin, IGFBP-1, IL-8, MCP-1, MMP-9, and VEGF expressions in chondrocytes. The PTX pretreatment also inhibited LPA-mediated NF-kB activation, suggesting the presence of active Gi/NF-kB signaling in CHON-001 and HC cells. The effect of LPA on the angiogenesis-inducing capacity of chondrocytes may be due to the increased angiogenesis factor expression via the Gi/NF-kB signaling pathway.

Leptin Enhances Insulin Sensitivity by Direct and Sympathetic Nervous System Regulation of Muscle IGFBP-2 Expression: Evidence From Nonrodent Models

Leptin is produced from white adipose tissue and acts primarily to regulate energy balance. Obesity is associated with leptin resistance and increased circulating levels of leptin. Leptin has recently been shown to influence levels of IGF binding protein-2 (IGFBP-2), a protein that is reduced in obesity and type 2 diabetes. Overexpression of IGFBP-2 protects against obesity and type 2 diabetes. As such, IGFBP-2 signaling may represent a novel pathway by which leptin regulates insulin sensitivity. We sought to investigate how leptin regulates skeletal muscle IGFBP-2 levels and to assess the impact of this on insulin signaling and glucose uptake. In vitro experiments were undertaken in cultured human skeletal myotubes, whereas in vivo experiments assessed the effect of intracerebroventricular leptin on peripheral skeletal muscle IGFBP-2 expression and insulin sensitivity in sheep. Leptin directly increased IGFBP-2 mRNA and protein in human skeletal muscle through both signal transducer and activator of transcription-3 and phosphatidylinositol 3-kinase signaling, in parallel with enhanced insulin signaling. Silencing IGFBP-2 lowered leptin- and insulin-stimulated protein kinase B phosphorylation and glucose uptake. In in vivo experiments, intracerebroventricular leptin significantly increased hind-limb skeletal muscle IGFBP-2, an effect completely blocked by concurrent peripheral infusion of a β-adrenergic blocking agent. Sheep receiving central leptin showed improvements in glucose tolerance and circulating insulin levels after an iv glucose load. In summary, leptin regulates skeletal muscle IGFBP-2 by both direct peripheral and central (via the sympathetic nervous system) mechanisms, and these likely impact on peripheral insulin sensitivity and glucose metabolism.

Insulin like growth factor binding protein 4 promotes GBM progression and regulates key factors involved in EMT and invasion

Insulin like growth factor binding protein 4 (IGFBP4) regulates growth and development of tissues and organs by negatively regulating IGF signaling. Among most cancers, IGFBP4 has growth inhibitory role and reported as a down-regulated gene, except for renal cell carcinoma, wherein IGFBP4 promotes tumor progression. IGFBP4 expression has been shown to be higher in increasing grades of astrocytoma. However, the functional role of IGFBP4 in gliomas has not been explored. Surgical biopsies of 20 normal brain and 198 astrocytoma samples were analyzed for IGFBP4 expression by qRT-PCR. Highest expression of IGFBP4 mRNA was seen in GBM tumors compared to control brain tissues (median log2 of 2.035, p<0.0001). Immunohistochemical analysis of 53 tissue samples revealed predominant nuclear staining of IGFBP4, seen maximally in GBMs when compared to DA and AA tumors (median LI=29.12±16.943, p<0.001). Over expression of IGFBP4 in U343 glioma cells resulted in up-regulation of molecules involved in tumor growth, EMT and invasion such as pAkt, pErk, Vimentin, and N-cadherin and down-regulation of E-cadherin. Functionally, IGFBP4 over expression in these cells resulted in increased proliferation, migration and invasion as assessed by MTT, transwell migration, and Matrigel invasion assays. These findings were confirmed upon IGFBP4 knockdown in U251 glioma cells. Our data suggest a pro-tumorigenic role for IGFBP4 in glioma.

Effects of Exogenous Growth Hormone on Growth Hormone-Insulin-Like Growth Factor Axis of Human Gastric Cancer Cell

Aim: To study effects of recombinant human growth hormone (rhGH) on growth hormone-insulin-like growth factor axis (GH-IGFs) of human gastric cancer cell in vivo in order to reveal part mechanism of growth effects of rhGH on gastric cancer. Methods: Nude mice were randomly divided into control group, cisplatin (DDP) group, rhGH group and DDP + rhGH group after human gastric cancer xenograft model of node mice was successfully founded and drugs were used for 6 days. We investigated volume of tumor, inhibitory rate of tumor and cell cycle by slide gauge and flow cytometry. In addition, We also respectively investigated insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-3 (IGFBP-3) of blood serum of nude mice, IGF-ImRNA, insulin-like growth factor-I receptor (IGF-IR) mRNA and IGFBP-3 mRNA of xenograft of nude mice by enzyme linked immunosorbent assay (ELISA) and semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) on the first day of completing use of drugs later. Results: Tumor grew obviously slowly and tumor inhibitory rate obviously rose in DDP group and DDP + rhGH group compared with control group and rhGH group (p p p < 0.05). Expressions of IGF-I mRNA and IGF-IR mRNA were not obviously different in all groups. But expression of IGFBP-3 mRNA obviously increased in rhGH group, DDP group and DDP + rhGH group compared with control group; meanwhile, expression of IGFBP-3 mRNA also obviously increased in DDP + rhGH group compared with control group, DDP group and rhGH group. Conclusion: Our results indicated rhGH in short-time use did not improve proliferation of human gastric cancer cells and its mechanism was possible that rhGH in short-time use raised simultaneously IGF-I and IGFBP-3 of blood serum and increased IGFBP-3 mRNA, but degraded ratio of IGF-I and IGFBP-3 of blood serum in human gastric cancer cells.

Downregulation of Insulin-like growth factor binding protein 6 is associated with ACTH-secreting pituitary adenoma growth

Adrenocorticotrophic hormone (ACTH)-dependent Cushing's syndrome, called Cushing disease, is caused by a corticotroph tumor of the pituitary gland. Insulin-like growth factor binding protein 6 (IGFBP6), which regulates insulin-like growth factor (IGF) activity and inhibits several IGF2-dependent cancer growths, plays a pivotal role in the tumorigenesis of malignancy, but its roles in ACTH-secreting pituitary adenomas remain unclear. To investigate IGFBP6 expression in ACTH-secreting pituitary adenomas, and its involvement in tumor growth. Sporadic ACTH-secreting pituitary adenomas specimens (n = 41) and adjacent non-tumorous pituitary tissues (n = 9) were collected by transphenoidal surgery. IGFBP6 expression was assessed by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and validated by Western blotting. Associations of IGFBP6 expression with maximum tumor diameter or Ki-67 labeling index were evaluated in ACTH-secreting pituitary adenomas. IGFBP6 mRNA and protein expression were both decreased in ACTH-secreting pituitary adenomas, compared to adjacent non-tumorous pituitary tissues (P < 0.01). IGFBP6 expression was correlated inversely with maximum tumor diameter (Rho = -0.53, P < 0.0001) and Ki-67 levels (Rho = -0.52, P < 0.05). Moreover, IGFBP6 downregulation activated PI3 K-AKT-mTOR pathway in ACTH-secreting pituitary adenomas. IGFBP6 attenuation in ACTH-secreting pituitary adenomas is associated with tumor growth, through activation of PI3K-AKT-mTOR pathway. The finding underlies IGFBP6 roles in Cushing disease and would potentially provide a novel target of medical therapies.

Importance of C/EBPβ Binding and Histone Acetylation Status in the Promoter Regions for Induction of IGFBP-1, PRL, and Mn-SOD by cAMP in Human Endometrial Stromal Cells

Dynamic changes of gene expressions occur in human endometrial stromal cells (ESCs) during decidualization. CCAAT/enhancer-binding proteinβ (C/EBPβ) regulates the expression of a number of decidualization-related genes. In addition to transcription factors, it is important to know the role of epigenetic mechanisms, such as histone modifications in the regulation of decidualization-related genes. This study investigated the molecular and epigenetic mechanisms by which cAMP up-regulates the expression of IGF-binding protein-1 (IGFBP-1), prolactin (PRL), and manganese superoxide dismutase (Mn-SOD) in ESC. ESCs isolated from proliferative phase endometrium were incubated with cAMP to induce decidualization. IGFBP-1, PRL, and Mn-SOD mRNA expressions were determined by real-time RT-PCR. The C/EBPβ binding and histone modification status (acetylation of histone-H3 lysine-27 [H3K27ac]) in the promoter were examined by chromatin immunoprecipitation assay. Knockdowns of C/EBPβ were performed using the small interfering RNA method. cAMP induced mRNA expressions of IGFBP-1 and PRL accompanied by the increases in both C/EBPβ binding activities and H3K27ac levels in the promoters. The stimulatory effects of cAMP on mRNA levels and H3K27ac levels were completely abolished by C/EBPβ knockdown. cAMP increased Mn-SOD mRNA levels and C/EBPβ binding activities in the enhancer region. C/EBPβ knockdown inhibited Mn-SOD mRNA levels. The H3K27ac levels in the enhancer were high before cAMP stimulus but were not further increased by cAMP and were not inhibited by C/EBPβ knockdown. These results show that C/EBPβ regulates the expression of IGFBP-1 and PRL by altering the histone acetylation status of their promoters but differently regulates Mn-SOD gene expression in human ESC during decidualization.

High concentrations of pyridoxal stimulate the expression of IGFBP1 in HepG2 cells through upregulation of the ERK/c-Jun pathway

Increasing evidence suggests that dietary vitamin B6 is linked to the prevention of cancer and cardiovascular disease. However, the molecular mechanisms involved in this process are not yet understood. Preliminary results in the current study indicated, following DNA microarray analysis and quantitative PCR, that insulin‑like growth factor‑binding protein 1 (IGFBP1) mRNA is upregulated in HT29 colon carcinoma cells exposed to pyridoxal (PL, 500 µM). IGFBP1 is secreted from the liver and is hypothesized to exert a protective role in the development of cancer and cardiovascular disease. Thus, further experiments were performed to investigate the effect of PL on the expression of IGFBP1 in HepG2 hepatocellular carcinoma cells. The addition of PL (500 µM) markedly increased the expression of IGFBP1 mRNA in HepG2 cells at 6, 12 and 24 h (P<0.01), whereas other vitamers (500 µM), including pyridoxal 5'‑phosphate (PLP), pyridoxine (PN) and pyridoxamine (PM), caused no such effect. The expression of the IGFBP1 protein in the cell lysate and culture medium was elevated in the presence of PL. PL elevated expression of the active form of ERK1 protein, p‑ERK1, and the p‑c‑Jun protein, a downstream factor of ERK. Furthermore, IGFBP1 expression, elevated by PL, was suppressed by PD98059, an ERK inhibitor. Higher expression of IGFBP1 protein by PL was suppressed by cycloheximide. These results suggest that PL may induce the expression of IGFBP1 in hepatoma cells via a mechanism involving the ERK/c‑Jun pathway.

Abstract 089: Response Gene To Complement 32 Is Involved In Glucose Metabolism Disorder In Endothelial Cells And Mediated By P53

Response gene to complement 32 (RGC-32) was considered as an apoptosis-promoting factor. To explore the novel functions of RGC-32, a DNA array analysis was performed in Human Microvascular Endothelial Cells (HMEC) treated with SiRNA, which showed that glucose metabolism was one of most dramatically changed biological process. qPCR analysis also proved that many glucose metabolism related genes were changed dramatically in RGC32 o/e HMEC, one of which was Insulin-like growth factor binding protein 4(IGFBP4). We propose that RGC-32 may be a potential factor involved in the cycle of endothelial glucose metabolism besides glucose induced apoptosis. Then we found that expression of RGC-32 was dramatically increased in mice hearts and adipose tissue after high fat diet treatment, as well as in HMEC after high glucose (30mM) treatment. In high fat diet treated endothelial specific RGC-32 transgenic mice (VE-Cad/RGC-32), decreases in area under the curve (AUC) of glucose tolerance test were observed when compared to their wild type littermates. Upregulated P53 and downregulated IGFBP4 mRNA expression level were also observed in the heart of VE-Cad/RGC-32 mice.Furthermore, we found that P53 was upregulated in RGC-32 o/e HMEC and blocking of p53 was able to decrease the RGC-32-related induction of apoptotic cells. We also observed that RGC-32 can not only decrease IGFBP4 but also reverse the decrease of IGFBP4 in high glucose or insulin condition. Interestingly, after treated the cells with pifithrin-a, a specific P53 inhibitor, decreased IGFBP4 by RGC-32 was rescued. These results demonstrate that RGC-32 may have some kind of connections with glucose metabolism besides its well-known apoptosis-promoting characters and P53 may be a mediator of RGC-32 related glucose metabolism disorder as well as apoptosis.These findings will provide some clues for novel insights into the functions of RGC-32.

DOG1 Regulates Growth and IGFBP5 in Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GIST) are characterized by activating mutations of KIT or platelet-derived growth factor receptor α(PDGFRA), which can be therapeutically targeted by tyrosine kinase inhibitors (TKI) such as imatinib. Despite long-lasting responses, most patients eventually progress after TKI therapy. The calcium-dependent chloride channel DOG1 (ANO1/TMEM16A), which is strongly and specifically expressed in GIST, is used as a diagnostic marker to differentiate GIST from other sarcomas. Here, we report that loss of DOG1 expression occurs together with loss of KIT expression in a subset of GIST resistant to KIT inhibitors, and we illustrate the functional role of DOG1 in tumor growth, KIT expression, and imatinib response. Although DOG1 is a crucial regulator of chloride balance in GIST cells, we found that RNAi-mediated silencing or pharmacologic inhibition of DOG1 did not alter cell growth or KIT signaling in vitro. In contrast, DOG1 silencing delayed the growth of GIST xenografts in vivo. Expression profiling of explanted tumors after DOG1 blockade revealed a strong upregulation in the expression of insulin-like growth factor-binding protein 5 (IGFBP5), a potent antiangiogenic factor implicated in tumor suppression. Similar results were obtained after selection of imatinib-resistant DOG1- and KIT-negative cells derived from parental DOG1 and KIT-positive GIST cells, where a 5,000-fold increase in IGFBP5 mRNA transcripts were documented. In summary, our findings establish the oncogenic activity of DOG1 in GIST involving modulation of IGF/IGF receptor signaling in the tumor microenvironment through the antiangiogenic factor IGFBP5.

TCDD induces the expression of insulin-like growth factor binding protein 4 in 5L rat hepatoma cells: A cautionary tale of the use of this cell line in studies on dioxin toxicity

Previous quantitative proteomic studies on the actions of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in 5L rat hepatoma cells, a cell model frequently used for investigating the mechanisms of TCDD toxicity, had indicated that dioxin exposure reduced the abundance of numerous proteins which are regulated at the level of protein synthesis initiation. In the present study, we have analysed the mechanism mediating this inhibition. TCDD treatment of the cells largely prevented the activation of eukaryotic translation initiation factor 4E-binding protein 1, a regulator of translation initiation and substrate of the mammalian target of rapamycin (mTOR). By “working upwards” from mTOR, we observed that TCDD inhibited endogenous and IGF-I-induced AKT and ERK activation by interfering with tyrosine phosphorylation of insulin receptor substrate 1. This inhibition was mediated by a TCDD-induced secreted factor which was identified as insulin-like growth factor binding protein 4 (IGFBP-4). The induction of IGFBP-4 protein was dependent on a functional aryl hydrocarbon receptor and was preceded by a rapid increase in the level of IGFBP-4 mRNA indicating that IGFBP-4 is a previously unknown transcriptional target of TCDD in 5L cells. IGFBP-4 was not induced by TCDD in the parental cell line of 5L cells, Fao, and in various closely related rat hepatoma cell lines as well as in other unrelated cell types. Analysis of 5L cell chromosomes by multicolour spectral karyotyping (SKY) revealed that the cells carry several hitherto uncharacterised chromosomal translocations. The observations suggest that in 5L cells the Igfbp-4 gene may have got under the control of a promoter containing dioxin responsive element(s) leading to the induction of IGFBP-4 by TCDD. These findings emphasise a particular caution when interpreting and extrapolating results on the action mechanisms of TCDD obtained in studies using 5L cells as a model system.

POLYMORPHISMS IN THE 5´ FLANKING REGION AND FIRST EXON OF INSULIN-LIKE GROWTH FACTOR 1 GENE IN SOUTHERN POPULATIONS OF BUFFALO

The Insulin-like Growth Factor 1 (IGF-1) system plays a critical endocrine role controlling nutrient metabolism in animals and it is a group of structurally-related polypeptides that regulate the growth of many types of mammalian cells. In liver, IGF-1 is dynamically regulated by lactation and energy balance. Less is known about the regulation of IGF-1 and IGF-binding protein mRNA in reproductive tissues and plays an important role in bovine follicular growth, acquisition of oocyte competence and embryo viability. The present study describes Polymorphisms in the IGF-1 Gene of Buffalo population in south of Iran. In order to characterization polymorphism, blood sample were collected from 95 buffalos from Ahvaz, Dezful, Shushtar, Shadegan and Susangerd cities. DNA extraction was based on Boom method and exon 1 of the IGF-1 gene was amplified to produce a 250 bp fragment. The amplified fragment were digested with Eco105I (SnaBI) restriction endonuclease. Also, the 265 bp of IGF-1 promoter in the 5’ Flanking Region was amplified and subsequently subjected to Single Strand Conformation Polymorphism (SSCP). The results were revealed one pattern (B) in digestion and all the five populations were monomorph. But, the populations exhibited three different SSCP patterns. It is possible that this gene has not exposed to selection and inbreeding is estimated high.

POLYMORPHISM OF INSULIN-LIKE GROWTH FACTOR 1 GENE IN NAJDI CATTLE POPULATIONS

The Insulin-like Growth Factor 1 (IGF-1) system plays a critical endocrine role controlling nutrient metabolism in dairy cattle and it is a group of structurally-related polypeptides that regulate the growth of many types of mammalian cells. In liver, IGF-1 is dynamically regulated by lactation and energy balance. Less is known about the regulation of IGF-1 and IGF-binding protein mRNA in reproductive tissues and plays an important role in bovine follicular growth, acquisition of oocyte competence and embryo viability. The present study describes polymorphism of IGF-1 gene in Najdi cattle populations. In order to characterization polymorphism, blood sample were collected from 84 Najdi cattles from Shadegan, Mahshar cities and Shushtar station. DNA extraction was based on Boom method and exons 1 of the IGF-1 gene were amplified to produce a 249 bp fragment. The amplified fragment were digested with Eco105I (SnaBI) restriction endonuclease and then subjected to electrophoretic separation in ethidium bromide-stained 2% agarose gel. The results were revealed two alleles, A and B. Three genotypes were observed, Frequencies were 2.38, 14.28 and 83.33% for AA, AB and BB, respectively. This gives frequencies of 0/0952 and 0/9048 for A and B alleles. The populations were in hardy-weinberg equilibrium. It is possible that this gene has not exposed to selection. The heterozygosity is low and inbreeding is estimated high.

Evolution of Ancient Functions in the Vertebrate Insulin-Like Growth Factor System Uncovered by Study of Duplicated Salmonid Fish Genomes

Whole-genome duplication (WGD) was experienced twice by the vertebrate ancestor (2 rounds; 2R), again by the teleost fish ancestor (3R) and most recently in certain teleost lineages (4R). Consequently, vertebrate gene families are often expanded in 3R and 4R genomes. Arguably, many types of “functional divergence” present across 2R gene families will exceed that between 3R/4R paralogs of genes comprising 2R families. Accordingly, 4R offers a form of replication of 2R. Examining whether this concept has implications for molecular evolutionary research, we studied insulin-like growth factor (IGF) binding proteins (IGFBPs), whose six 2R family members carry IGF hormones and regulate interactions between IGFs and IGF1-receptors (IGF1Rs). Using phylogenomic approaches, we resolved the complete IGFBP repertoire of 4R-derived salmonid fishes (19 genes; 13 more than human) and established evolutionary relationships/nomenclature with respect to WGDs. Traits central to IGFBP action were determined for all genes, including atomic interactions in IGFBP–IGF1/IGF2 complexes regulating IGF–IGF1R binding. Using statistical methods, we demonstrate that attributes of these protein interfaces are overwhelming a product of 2R IGFBP family membership, explain 49–68% of variation in IGFBP mRNA concentration in several different tissues, and strongly predict the strength and direction of IGFBP transcriptional regulation under differing nutritional states. The results support a model where vertebrate IGFBP family members evolved divergent structural attributes to provide distinct competition for IGFs with IGF1Rs, predisposing different functions in the regulation of IGF signaling. Evolution of gene expression then acted to ensure the appropriate physiological production of IGFBPs according to their structural specializations, leading to optimal IGF-signaling according to nutritional-status and the endocrine/local mode of action. This study demonstrates that relatively recent gene family expansion can facilitate inference of functional evolution within ancient genetic systems.

Regulation of decidualization in human endometrial stromal cells through exchange protein directly activated by cyclic AMP (Epac)

IntroductionHuman endometrial stromal cells (ESCs) undergo differentiation during the decidualization process. Decidualization is characterized by their enhanced production of IGF binding protein-1 (IGFBP-1), prolactin (PRL), and the forkhead transcriptional factor FOXO1, and transformation into more rounded cells, during the secretory phase of the menstrual cycle and subsequent pregnancy. Protein kinase A (PKA)-mediated cAMP signaling is crucial for this process. The present study was undertaken to examine the involvement of a mediator of cAMP signaling, exchange protein directly activated by cAMP (Epac), in decidualization of cultured ESCs. ResultsTreatment of ESCs with the Epac-selective cAMP analog 8-CPT-2-OMe-cAMP (CPT) had no effect on IGFBP-1, PRL, and FOXO1 mRNA expression. However, CPT potentiated IGFBP-1 and PRL expression stimulated by the PKA-selective cAMP analog N6-Phe-cAMP (Phe) and activated Rap1, a downstream regulator of Epac signaling. Knock-down of Epac1, Epac2, or Rap1 significantly inhibited the Phe- or Phe/CPT-induced increase in IGFBP-1 and PRL expression, as well as Rap1 activation. Furthermore, CPT enhanced IGFBP-1 and PRL expression and the morphological differentiation induced by ovarian steroids, whereas Epac1, Epac2, or Rap1 knock-down suppressed these events. ConclusionThese data provide evidence for the involvement of the Epac/Rap1 signaling pathway in cAMP-mediated decidualization of human ESCs.

Expression of insulin-like growth factor binding protein-6 in the vitreous and serum in a proliferative vitreoretinopathy rat model

Background Proliferative vitreoretinopathy (PVR) is one of the major causes of retinal detachment surgery failure.Based on proteomic studies of PVR vitreous,the insulin-like growth factor binding protein-6 (IGFBP-6) protein was specifically expressed in the vitreous and serum of PVR patients.Furthermore,its expression level is higher in the vitreous and serum in severe PVR patients than that in mild PVR patients.Objective This experiment was to detect the expression of IGFBP-6 in a PVR rat model.Methods Seventy 7-week old male SPF Wistar rats were included and were randomized into the PVR model group and control group.A mixture of RPE-J cell suspension(5 μl) and platelet-rich plasma (5 μl) was intravitreally injected in the left eyes of adult Wistar rats to establish the PVR model,and normal saline solution was administered in the same way in the control group.The rat eyes were clinically examined 1 week,2,3 and 4 weeks after injection,and PVR was graded based on the criteria of Francine.The animals were sacrificed after 1 week,2,4 or 8 weeks for the preparation of retinal sections and liver extraction.Expression levels of IGFBP-6 mRNA in the rat retina and liver were assayed by real-time Q-PCR.The expression of IGFBP-6 protein in the rat serum and vitreous was detected by ELISA.The use of animals complied with the Regulations for the Administration of Affairs Concerning Experimental Animals by State Science and Technology Commission.Results Purified IGFBP-6 RNA was extracted from the liver and retina of Wistar rat and quantified by real-time Q-PCR.The expression level of IGFBP-6 mRNA in retina was (3.79± 1.33) × 10-4 in the PVR model rats,showing a significant decline in comparison with the control rats with a level of(8.32±2.96) × 10 4,4 weeks after injection (t =3.42,P＜0.01).The expression of IGFBP-6 mRNA in the 4th week was significantly lower than that of 1 week,2 or 8 weeks after the establishment of the PVR model(P＜0.05).No significant difference was found in the IGFBP-6 mRNA level in the liver between the PVR group and control group(27.60± 14.01 × 10 4 vs.25.01 ± 12.04 ×10-4,respectively),as well as among the different time points(P＞0.05).IGFBP-6 mRNA content in the retina was significantly reduced in grades 1,2 or 3 of the PVR groups compared with the control group(P＞0.05),but there was no significant difference among the different grades of PVR groups (P＞0.05).Concentrations of IGFBP-6 protein in grades 1,2 and 3 of the PVR model group were (221.00 ± 19.32),(229.63 ± 18.89) and (225.70 ± 26.71) μg/L,with a significant elevation in comparison with (173.25 ±21.11) μg/L of the control group (t =2.14,P＜0.05).However,there was no significant change among the different grades of PVR groups(t=1.24,1.46,P＞0.05).The concentrations of IGFBP-6 protein in the vitreous and serum were higher in PVR rat samples (vitreous:225.44±19.36 μg/L;serum:108.48 ± 15.78 μg/L) than in control rats (vitreous:173.25 ± 21.11 μg/L,serum:95.96 ±17.40 μg/L)(P＜0.05).Conclusions The concentrations of IGFBP-6 protein in the vitreous and serum increase in PVR rats.The results indicate that the increased IGFBP-6 in the vitreous might be a localized autocrine secretion of the eye. Key words: Insulin-like growth factor binding protein; Proliferative vitreoretinopathy; Rat/ model; Retina

Role of Insulin-Like Growth Factor Binding Protein-3 in 1, 25-Dihydroxyvitamin-D3-Induced Breast Cancer Cell Apoptosis

Insulin-like growth factor I (IGF-I) is implicated in breast cancer development and 1, 25-dihydroxyvitamin D3 (1, 25-D3) has been shown to attenuate prosurvival effects of IGF-I on breast cancer cells. In this study the role of IGF binding protein-3 (IGFBP-3) in 1, 25-D3-induced apoptosis was investigated using parental MCF-7 breast cancer cells and MCF-7/VDR cells, which are resistant to the growth inhibitory effects of 1, 25-D3. Treatment with 1, 25-D3 increased IGFBP-3 mRNA expression in both cell lines but increases in intracellular IGFBP-3 protein and its secretion were observed only in MCF-7. 1, 25-D3-induced apoptosis was not associated with activation of any caspase but PARP-1 cleavage was detected in parental cells. IGFBP-3 treatment alone produced cleavage of caspases 7, 8, and 9 and PARP-1 in MCF-7 cells. IGFBP-3 failed to activate caspases in MCF-7/VDR cells; however PARP-1 cleavage was detected. 1, 25-D3 treatment inhibited IGF-I/Akt survival signalling in MCF-7 but not in MCF-7/VDR cells. In contrast, IGFBP-3 treatment was effective in inhibiting IGF-I/Akt pathways in both breast cancer lines. These results suggest a role for IGFBP-3 in 1, 25-D3 apoptotic signalling and that impaired secretion of IGFBP-3 may be involved in acquired resistance to vitamin D in breast cancer.

Molecular characterization and expression pattern of insulin-like growth factor binding protein-3 (IGFBP-3) in common carp, Cyprinus carpio

A full-length cDNA encoding the insulin-like growth factor binding protein-3 (IGFBP-3) was cloned from the liver of common carp (Cyprinus carpio) by RT-PCR. The IGFBP-3 cDNA sequence is 1,680 bp long and has an open reading frame of 882 bp encoding a predicted polypeptide of 293 amino acid residues. The deduced amino acid sequence contains a putative signal peptide of 25 amino acid residues resulting in a mature protein of 268 amino acids. A single band of approximate 1.9 kb was found in liver by Northern blot analysis. IGFBP-3 mRNA was observed in all regions of brain with high levels. In peripheral tissues, high levels of IGFBP-3 mRNA were found in retina, red muscle, liver, heart, posterior intestine, spleen, and testis. Relatively lower levels were found in white muscle, kidney, thymus gland, and ovary, while in head kidney, blood, skin, gill, middle intestine, and anterior intestine, the IGFBP-3 mRNA levels were much lower. IGFBP-3 mRNA was first detected in the blastula stage with significantly high level. The level sharply decreased in gastrula stage, and it became to increase in the following stages. During the reproductive cycle, the abundance of IGFBP-3 mRNA significantly decreased between the recrudescing stage and the matured stage in ovary, although in testis, IGFBP-3 mRNA expression level did not exhibit a significant change. The mRNA expression profiles in the present study imply that the IGFBP-3 may play important physiological functions in common carp development and reproduction.

Interleukin 1β Regulation of FoxO1 Protein Content and Localization: EVIDENCE FOR A NOVEL CERAMIDE-DEPENDENT MECHANISM

FoxO1 transcription factor controls the glucose and lipid metabolism, as well as cell proliferation and stress response. Akt, activated by insulin and other growth factors, phosphorylates FoxO1 causing its nuclear export and activity suppression. In this manuscript, we show that IL-1β, a pro-inflammatory cytokine, has the opposite effects on FoxO1. IL-1β stimulation of primary rat hepatocytes and HEK293 cells overexpressing the IL-1β receptor (293-IL-1RI) results in increased nuclear and cytosolic FoxO1 protein but not mRNA levels. IL-1β stimulation also elevates the levels of a mutant FoxO1 that is resistant to Akt phosphorylation. This suggests that an Akt-independent mechanism is involved. Co-stimulation with insulin does not affect the IL-1β induction of FoxO1. The IL-1β effects on FoxO1 are counteracted, however, by the silencing or inhibition of neutral sphingomyelinase 2 (nSMase-2) using shRNAi, scyphostatin, or GW4869, as well as by the pharmacological inhibition of JNK and ERK. Reversely, the overexpression of nSMase-2 through adenovirus-mediated gene transfer potentiates, in a JNK- and ERK-dependent manner, the IL-1β effects. We also show that transcription of insulin-like growth factor-binding protein-1 mRNA, which requires active FoxO1, is stimulated by IL-1β and is suppressed by the inhibition of nSMase-2 and JNK. In conclusion, we propose that IL-1β regulates FoxO1 activity through a novel nSMase-2-dependent pathway.

Effect of alternative lipids and temperature on growth factor gene expression in yellowtail kingfish (Seriola lalandi)

This study was undertaken to assess the efficacy of utilizing insulin-like growth factor 1 (IGF-I) and insulin-like growth factor binding protein 1 (IGFBP-1) as endocrine biomarkers to provide a rapid indication of yellowtail kingfish growth using real-time, reverse-transcriptase quantitative PCR (RT-qPCR). Two experiments were conducted separately (5 weeks each) at an optimal water temperature (22°C) using fish weighing 95.6 ± 0.1 g (mean ± standard deviation, n = 3) and at a sub-optimal water temperature (18°C) using similar-sized fish (101 ± 0.1 g, n = 3). Four experimental diets were formulated to contain poultry oil (PO) or canola oil (CO) at 50% or 100% inclusion as a substitute for fish oil (FO). A diet containing 100% FO was used as a control. Irrespective of diet, fish grew faster at 22°C than at 18°C. The 100% replacement of FO by CO resulted in the poorest fish growth at both temperatures. IGF-I expression correlated with growth rate at 22°C, but the same trend was not seen at 18°C. Hepatic IGF-I and IGFBP-1 mRNA expression were also positively correlated. This study suggests that hepatic IGF-I mRNA assessed by RT-qPCR with additional methodological development may be used to accurately assess the influence of diet on growth of some fish species used in aquaculture.

Roles of α-linolenic acid on IGF-I secretion and GH/IGF system gene expression in porcine primary hepatocytes

The main purposes of this study were to investigate the effects of α-linolenic acid (ALA) on the insulin-like growth factor (IGF) system of porcine primary hepatocytes with or without growth hormone (GH) or insulin and the potential role of peroxisome proliferator-activated receptor α and -γ (PPARα/γ) pathway. We found that 1 μM ALA increased IGF-I secretion from hepatocytes at 48 and 72 h. Expression of hepatocytes IGF-I, IGF-II, GH receptor (GHR), insulin receptor (IR), IGF-binding protein 3 (IGFBP3), and IGFBP4 mRNAs was up-regulated by ALA treatment. GH (15 nM) alone or co-treated with ALA increased hepatocytes IGF-I secretion and the expression of GHR and IGFBP1 mRNAs, but down-regulated IGFBP5 mRNA compared with appropriate control across ALA. GH also enhanced the ALA-induced increase in the transcript levels of IGF-II and GHR, but tended to attenuate that of IGFBP4. Insulin (1 μM) alone or co-treated with ALA improved IGF-I secretion and the expression of IGFBP3 mRNA, but decreased IGFBP1 mRNA versus appropriate control across ALA. Insulin also up-regulated the expression of GHR, IR, IGFBP3, and IGFBP4 mRNAs, and tended to prevent the transcript levels of IGF-I and IGFBP4 improved by ALA. Both PPARγ agonist rosiglitazone and its antagonist GW9662 could elevated the IGF-I secretion in dose-dependent manner but they had no interaction with ALA. However, GW7647, a PPARα agonist, increased IGF-I secretion dose-dependently, but the antagonist GW6471 was without effect. Moreover, GW6471 prevented the IGF-I promoting effect of ALA. This suggests that the IGF-I promoting effect of ALA may be mediated by the PPARα pathway.