Ability Of Insulin-like Growth Factor-1 Research Articles

Insulin-like growth factor-1 improves diabetic cardiomyopathy through antioxidative and anti-inflammatory processes along with modulation of Akt/GSK-3β signaling in rats.

Diabetic cardiomyopathy (DCM), a serious complication of diabetes mellitus, is associated with changes in myocardial structure and function. This study sought to explore the ability of insulin-like growth factor-1 (IGF-1) to modulate DCM and its related mechanisms. Twenty-four male Wistar rats were injected with streptozotocin (STZ, 60 mg/kg) to mimic diabetes mellitus. Myocardial fibrosis and apoptosis were evaluated by histopathologic analyses, and relevant proteins were analyzed by Western blotting. Inflammatory factors were assessed by ELISA. Markers of oxidative stress were tested by colorimetric analysis. Rats with DCM displayed decreased body weight, metabolic abnormalities, elevated apoptosis (as assessed by the bcl-2/bax ratio and TUNEL assays), increased fibrosis, increased markers of oxidative stress (MDA and SOD) and inflammatory factors (TNF-α and IL-1β), and decreased phosphorylation of Akt and glycogen synthase kinase (GSK-3β). IGF-1 treatment, however, attenuated the metabolic abnormalities and myocardial apoptosis, interstitial fibrosis, oxidative stress and inflammation seen in diabetic rats, while also increasing the phosphorylation levels of Akt and GSK-3β. These findings suggest that IGF-1 ameliorates the pathophysiological progress of DCM along with an activation of the Akt/GSK-3β signaling pathway. Our findings suggest that IGF-1 could be a potential therapeutic choice for controlling DCM.

Abstract 11552: The α5β1 Integrin Mediates Insulin-like Growth Factor-1 Induction of Aortic Smooth Muscle Alpha-Actin Expression Through a PI3K/mTORC2/eIF4E Translational Mechanism

In arterial remodeling, smooth muscle cell (SMC) loss of contractile phenotype and increased proliferation may result in vessel stenosis or a greater propensity for aneurysm formation and rupture. Here, we show that insulin-like growth factor-1 (IGF-1) induces contractile phenotype of human aortic SMCs in culture, and we investigate the signal transduction mechanisms responsible using Western blot. IGF-1 induced a dose-dependent increase in protein expression of the contractile marker alpha-actin (αSMA) (2.4-fold-increase, 18hr serum-free vs. 100ng/mL IGF-1, p<0.001), without affecting ACTA2 mRNA levels (real time RT-PCR, 4-18 hrs, p=NS). Moreover, IGF-1 upregulation of αSMA expression was not blocked by actinomycin D but was inhibited by cycloheximide (p<0.01), thereby demonstrating posttranscriptional and translation-dependent regulation by IGF-1, respectively. Furthermore, IGF-1-induced αSMA expression was not blocked with PD98059 or rapamycin (50 or 100 nM), but was completely inhibited with LY294002 (p<0.001), 500 nM rapamycin (p<0.01), and Torin 1, thereby indicating that the ability of IGF-1 to induce SMC differentiation was independent of Erk1/2 and mTORC1, but dependent on PI3K- and mTORC2-signaling. A prolyl-hydroxylase-inhibitor (EDHB) or a function-blocking antibody against the α2β1 integrin (BHA2.1) had no effect on IGF-1-upregulation of αSMA expression. However, both EDHB and BHA2.1 significantly attenuated IGF-1-induced expression of the proliferation marker PCNA, thereby suggesting that collagen and the α2β1 integrin promote IGF-1-induced proliferation. Conversely, a blocking antibody against the α5β1 integrin (JBS5) did not block IGF-1-induced PCNA expression but completely inhibited IGF-1 induction of αSMA expression (p<0.01) and abolished IGF-1-induced phosphorylation of a master regulator of cap-dependent protein translation, eukaryotic initiation factor-4E (eIF4E) (p<0.001). Therefore, we concluded that IGF-1 induced αSMA expression via a PI3K/mTORC2/eIF4E translational mechanism that is dependent on the α5β1 integrin. Overall, these findings provide evidence that the α5β1 and α2β1 integrins mediate IGF-1-signaling to govern IGF-1-induced translational regulation of SMC phenotype.

Abstract 1540: Effect of IGF1 on cancer and stromal cells of human pancreatic tumors

Abstract Background: Insulin-like growth factor 1 (IGF1) exerts a broad anti-apoptotic function, and IGF1/IGF1-receptor (IGF-1R) signaling pathway plays a crucial role in human cancer development and progression. Stromal cells associated with cancer cells are considered an important component of tumor microenvironment, including pancreatic cancers. Previously we have shown an increased expression of IGF1 in pancreatic ductal adenocarcinoma stroma. The goal of our study was to investigate the effect of IGF1 on expression of important for tumor progression genes that regulate epithelial-mesenchymal transition (EMT) in cancer and stromal cells of pancreatic tumors. Methods: The effect of IGF1 was tested on five pancreatic cancer cell lines (AsPC-1, BxPC-3, Capan-2, MiaPaCa-2 and Panc1), all cultivated on cell medium with reduced levels of serum. Also, we used primary cultures of pancreatic ductal adenocarcinoma stromal cells on early passages. Gene expression was analyzed via Western Blotting and qRT-PCR. Results: In reduced serum medium IGF1 has been shown to stimulate proliferation in all cell lines and primary cultures. In cancer cell lines MiaPaCa-2 and Panc1 incubation with IGF1 lead to an increase in levels of SNAIL and Zeb1 proteins after 120 hours of incubation. There was an elevation in expression of Twist protein in all cancer cell lines after 120 hours of incubation. However, we have not detected a decrease in levels of epithelial differentiation marker E-cadherin, nor a notable increase in levels of mesenchymal differentiation markers N-cadherin and Vimentin in IGF1-treated cancer cell lines. Only a slight decrease in E-cadherin expression was shown in IGF1-treated AsPC-1 and Panc1 cells. Treatment of primary stromal cells of pancreatic ductal adenocarcinoma with IGF1 results in a slight elevation of N-cadherin and Vimentin expression, as well as a significant increase in anti-apoptotic protein survivin levels. Incubation of stromal cells with specific low-molecular weight inhibitor of IGF-1R was shown to significantly increase levels of SNAI1 gene expression and increase SNAIL protein levels. Conclusions: Analysis of EMT markers and transcription factors in pancreatic cancer cell lines does not allow us to draw conclusions about the ability of IGF1 to cause EMT. Despite increased levels of SNAIL, Zeb1 and Twist proteins, epithelial cancer cells retained stable expression of E-cadherin and did not show an increase in mesenchymal marker expression. In pancreatic tumor stromal cultures IGF1 increases mesenchymal cell phenotype and, evidently, increases cell survival rate by stimulating survivin expression. The effect of IGF-1R inhibitor on the activation of SNAIL expression, as we assume, was caused by interactions between signaling pathways of IGF1 and SHH in stromal cell cultures. The work is supported by grant of Russian Foundation of Basic Research 13-04-40171-KOMFI Note: This abstract was not presented at the meeting. Citation Format: Marina R. Kopantseva, Eugenia Usova, Arsen Mikaelyan, Maria Kostina, Olga Melekhina, Vyacheslav Egorov, Eugene P. Kopantzev. Effect of IGF1 on cancer and stromal cells of human pancreatic tumors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1540. doi:10.1158/1538-7445.AM2015-1540

Dystroglycan modulates the ability of insulin-like growth factor-1 to promote oligodendrocyte differentiation

The adhesion receptor dystroglycan positively regulates terminal differentiation of oligodendrocytes, but the mechanism by which this occurs remains unclear. Using primary oligodendrocyte cultures, we identified and examined a connection between dystroglycan and the ability of insulin-like growth factor-1 (IGF-1) to promote oligodendrocyte differentiation. Consistent with previous reports, treatment with exogenous IGF-1 caused an increase in MBP protein that was preceded by activation of PI3K (AKT) and MAPK (ERK) signaling pathways. The extracellular matrix protein laminin was further shown to potentiate the effect of IGF-1 on oligodendrocyte differentiation. Depletion of the laminin receptor dystroglycan using siRNA, however, blocked the ability of IGF-1 to promote oligodendrocyte differentiation of cells grown on laminin, suggesting a role for dystroglycan in IGF-1-mediated differentiation. Indeed, loss of dystroglycan led to a reduction in the ability of IGF-1 to activate MAPK, but not PI3K, signaling pathways. Pharmacological inhibition of MAPK signaling also prevented IGF-1-induced increases in myelin basic protein (MBP), indicating that MAPK signaling was necessary to drive IGF-1-mediated enhancement of oligodendrocyte differentiation. Using immunoprecipitation, we found that dystroglycan, the adaptor protein Grb2, and insulin receptor substrate-1 (IRS-1), were associated in a protein complex. Taken together, our results suggest that the positive regulatory effect of laminin on oligodendrocyte differentiation may be attributed, at least in part, to dystroglycan's ability to promote IGF-1-induced differentiation.

Correlation of insulin-like growth factor 1 (IGF-1) expression and clinical outcome in K-RAS wild-type colorectal cancer patients treated with cetuximab-irinotecan

4017 Background: K-RAS wild type colorectal tumors show an improved response rate to anti-EGFR monoclonal antibodies. Nevertheless 70% to 40% of these patients still does not seem to benefit from this therapeutic approach. Recent data suggested that in presence of IGF-1 system altered activation colorectal cancer cells may escape anti-EGFR mediated cell death. The interaction between IGF-1 expression and K-RAS mutational analysis was tested in order to verify the ability of IGF-1 to identify a sub-group of patients more likely to benefit from EGFR-targeted antibodies treatment. Methods: IGF-1 expression and K-RAS mutational status was assessed in advanced colorectal cancer patients receiving irinotecan/cetuximab. Results: Sixty-two patients were analyzed. IGF-1 was negative in 21 patients (34%). and overexpressed in the remaining 41 cases (66%). In IGF-1 negative and IGF-1 positive tumors we observed progressive disease in 6 (29%) and 26 (63%) patients respectively (p = 0.01). Median time to progression was 7.7 months in patients showing IGF-1 negative tumors and 2.3 months for IGF-1 expressing tumors (p = 0.005). Among K-RAS wild type patients, IGF-1 negative and positive tumors showed a partial response to cetuximab-irinotecan in 7 (50%) and 1 (5%) cases respectively (p = 0.004). Median time to progression in IGF-1 negative tumors was 11 months and 3.2 months in IGF-1 positive colorectal cancers (p = 0.03). Conclusions: IGF-1 proved to be a reliable predictive factor for resistance to anti-EGFR monoclonal antibodies in K-RAS wild type colorectal cancer. Combined IGF-1 and K-RAS analysis may represent an effective strategy for a better selection of responding colorectal tumors in this setting. No significant financial relationships to disclose.

Insulin-like growth factor I slows the rate of denervation induced skeletal muscle atrophy

Loss of the nerve supply to skeletal muscle results in a relentless loss of muscle mass (atrophy) over time. The ability of insulin-like growth factor-1 to reduce atrophy resulting from denervation was examined after transection of the sciatic nerve in transgenic MLC/mIGF-1 mice that over-express mIGF-1 specifically in differentiated myofibres. The cross sectional area (CSA) of all types of myofibres and specifically type IIB myofibres was measured in tibialis anterior muscles from transgenic and wild-type mice at 28 days after denervation. There was a marked myofibre atrophy (∼60%) in the muscles of wild-type mice over this time with increased numbers of myofibres with small CSA. In the muscles of MLC/mIGF-1 mice, over-expression of mIGF-1 reduced the rate of denervation induced myofibre atrophy by ∼30% and preserved myofibres with larger CSA, compared to wild-type muscles. It is proposed that the protective effect of mIGF-1 on denervated myofibres might be due to reduced protein breakdown.

IGF-1 down-regulates IFN-γR2 chain surface expression and desensitizes IFN-γ/STAT-1 signaling in human T lymphocytes

AbstractThe ability of insulin-like growth factor-1 (IGF-1) to regulate surface expression of the interferon-γ receptor 2 (IFN-γR2) transducing chain and activation of IFN-γ–induced signal transducer and activator of transcription-1 (STAT-1) in human T cells was analyzed. We show that, especially in the absence of serum (which contains IGF-1), IGF-1 down-regulated surface expression of the IFN-γR2 chain and inhibited both IFN-γ–dependent STAT-1 activation and apoptosis in T-cell lines ST4, Jurkat, and Molt-4. IFN-γR2 down-regulation resulted from its enhanced internalization since IGF-1 completely restored the uptake of anti–IFN-γR2 monoclonal antibody (mAb) in serum-deprived T-cell lines. When the interaction between IGF-1 and its receptor was blocked by anti–IGF-1R mAb, enhancement of IFN-γR2 surface expression, STAT-1 activation, and reinstatement of IFN-γ–induced apoptosis were observed. Enhanced expression of IFN-γR2 was also observed in phytohemagglutinin (PHA)–activated T lymphoblasts cultured in the presence of anti–IGF-1R mAb, whereas IGF-1 or anti–IGF-1R mAb did not modify the high IFN-γR2 expression in B and myeloid cell lines. Both IGF-1 and anti–IGF-1R mAb did not modify the constitutive expression of IFN-γR2 mRNA in T cells as well as the high IFN-γR1 binding chain surface expression in T, B, and myeloid cells. These data indicate that IGF-1 plays a critical role in the desensitization of IFN-γ/STAT-1 signaling in T lymphocytes by delivering a signal for IFN-γR2 internalization.

Effect of Insulin and Insulin-Like Growth Factor 1 (IGF-1) on Activity of Glycogen Synthase in Skeletal Muscles of the Lamprey Lampetra fluviatilis

Activity of glycogen synthase (GS) in the muscle tissue of the lamprey Lampetra fluviatilis is studied in dynamics of the pre-spawning period as well as under effects of insulin and IGF-1. It is shown that GS exists in the muscles in two forms, the active (I-form) and inactive (D-form), the I-form prevailing during all studied time periods. With approaching the spawning, the GS activity fell 1.5–2 times due to a decrease of the I-form activity. From October to January, both insulin and IGF-1 stimulated GS at concentrations of 10−10–10−8 M and 10−9–10−8 M, respectively. The maximally effective concentrations (10−9 M insulin, 10−8 M IGF-1) produced a 2.5–3-fold rise of the I-form activity of GS at the period from October to December. In January the stimulating effect of these peptides decreased. In March the GS was insensitive both to insulin and to IGF-1. The obtained data indicate participation of insulin and IGF-1 in regulation of glycogen synthesis in lamprey skeletal muscles, the ability of IGF-1 to stimulate the enzyme activity being shown in the lower vertebrates for the first time. It is concluded that IGF-1 takes part in regulation of the carbohydrate metabolism already at early stages of evolution of vertebrates.