Protective Effect Of IGF-1 Research Articles

Carbonic Anhydrase 12 Protects Endplate Cartilage From Degeneration Regulated by IGF-1/PI3K/CREB Signaling Pathway.

Lumbar intervertebral disc degeneration (IVDD) is the most common cause of low back pain (LBP). Among all the factors leading to IVDD, lumbar cartilage endplate (LCE) degeneration is considered a key factor. In the present study, we investigate the effect and regulation of carbonic anhydrase 12 (CA12) in LCE, which catalyzes hydration of CO2 and participates in a variety of biological processes, including acid–base balance and calcification. Our results show that CA12, downregulated in degenerated LCE, could maintain anabolism and prevent calcification in the endplate. Furthermore, CA12 is regulated by the IGF-1/IGF-1R/PI3K/CREB signaling pathway. When we overexpressed CA12 in LCE, the decreased anabolism induced by inflammatory cytokine could be rescued. In contrast, reducing CA12 expression, either with siRNA, PI3Kinhibitor, or CREB inhibitor, could downregulate anabolism and cause apoptosis and then calcification in LCE. The protective effects of IGF-1 are even diminished with low-expressed CA12. Similar results are also obtained in an ex vivo model. Consequently, our results reveal a novel pathway, IGF-1/IGF-1R/PI3K/CREB/CA12, that takes a protective role in LCE degeneration by maintaining anabolism and preventing calcification and apoptosis. This study proposes a novel molecular target, CA12, to delay LCE degeneration.

The role of insulin-like growth factor 1 in ALS cell and mouse models: A mitochondrial protector

Amyotrophic lateral sclerosis (ALS) is a common neurodegenerative disorder, but little is known about the exact causes and pathophysiology of this disease. In transgenic mouse models of ALS, mitochondrial abnormalities develop during the disease and might contribute to the progression of ALS. Gene therapy was recently shown to induce beneficial effects. For example, the delivery of human insulin-like growth factor-1 (hIGF-1) by self-complementary adeno-associated virus (AAV) vectors has been shown to prolong the lifespan of ALS transgenic mice. However, the function of IGF-1 in mitochondria has not been systematically studied in ALS models. In this study, scAAV9-hIGF-1 was intramuscularly injected into transgenic SOD1G93A mice and administered to cell lines expressing the ∼25-kDa C-terminal fragment of transactive response DNA-binding protein (TDP-25). The mitochondrial electrical transmembrane potential was hyperpolarized, and electron microscopy findings revealed that the abnormal mitochondria were transformed. Moreover, the intrinsic mitochondrial apoptotic process was modified through the upregulation of anti-apoptotic proteins (B-cell lymphoma-extra large (Bcl-xl) and B-cell lymphoma-2 (Bcl-2)), the downregulation of pro-apoptotic proteins (Bcl-2-associated x protein (Bax) and Bcl-2 homologous antagonist killer (Bak)) and a reduction in mitochondrial cytochrome c release. Mitophagy was also increased after scAAV9-hIGF-1 treatment, as evidenced by a decrease in the p62 level and an increase in the LC3-II level. Furthermore, the clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (Cas9) system was used to delete the IGF-1 gene in SOD1G93A model mice via an intrathecal injection of scAAV9-sgRNA-IGF1-Cas9 to confirm these findings. The protective effect of IGF-1 on the mitochondria decreased after genetic deletion. These novel findings demonstrate that IGF-1 strongly protects mitochondria from apoptosis and upregulates mitophagy in mouse and cell models of ALS. Therefore, therapies that specifically protect mitochondrial function might be promising strategies for treating ALS.

IGF-1 protects SH-SY5Y cells against MPP+-induced apoptosis via PI3K/PDK-1/Akt pathway.

Insulin-like growth factor (IGF)-1 is a well-known anti-apoptotic pro-survival factor and phosphatidylinositol-3-kinase (PI3K)/Akt pathway is linked to cell survival induced by IGF-1. It is also reported that Akt signaling is modulated by 3-phosphoinositide-dependent kinase-1 (PDK1). In the current study, we investigated whether the anti-apoptotic effect of IGF-1 in SH-SY5Y cells exposed to 1-methyl-4-phenylpyridinium (MPP+) is associated with the activity of PI3K/PDK1/Akt pathway. Treatment of cells with IGF-1 inhibited MPP+-induced apoptotic cell death. IGF-1-induced activation of Akt and the protective effect of IGF-1 on MPP+-induced apoptosis were abolished by chemical inhibition of PDK1 (GSK2334470) or PI3K (LY294002). The phosphorylated levels of Akt and PDK1 were significantly suppressed after MPP+ exposure, while IGF-1 treatment completely restored MPP+-induced reductions in phosphorylation. IGF-1 protected cells from MPP+ insult by suppressing intracellular reactive oxygen species (ROS) production and malondialdehyde levels and increasing superoxide dismutase activity. Mitochondrial ROS levels were also increased during MPP+ exposure, which were attenuated by IGF-1 treatment. In addition, IGF-1-treated cells showed increased activities of succinate dehydrogenase and citrate synthase, stabilization of mitochondrial transmembrane potential, increased ratio of Bcl-2 to Bax, prevention of cytochrome c release and inhibition of caspase-3 activation with PARP cleavage. Furthermore, the protective effects of IGF-1 on oxidative stress and mitochondrial dysfunction were attenuated when cells were preincubated with GSK2334470 or LY294002. Our data suggest that IGF-1 protects SH-SY5Y cells against MPP+-associated oxidative stress by preserving mitochondrial integrity and inhibiting mitochondrial apoptotic cascades via the activation of PI3K/PDK1/Akt pathway.

The protective effects of IGF1 on the cochlear damage during the insertion of cochlear implant electrodes

The protective effects of IGF1 on the cochlear damage during the insertion of cochlear implant electrodes

IGF-1 prevents simvastatin-induced myotoxicity in C2C12 myotubes.

Statins are generally well tolerated, but treatment with these drugs may be associated with myopathy. The mechanisms of statin-associated myopathy are not completely understood. Statins inhibit AKT phosphorylation by an unclear mechanism, whereas insulin-like growth factor (IGF-1) activates the IGF-1/AKT signaling pathway and promotes muscle growth. The aims of the study were to investigate mechanisms of impaired AKT phosphorylation by simvastatin and to assess effects of IGF-1 on simvastatin-induced myotoxicity in C2C12 myotubes. C2C12 mouse myotubes were exposed to 10μM simvastatin and/or 10ng/mL IGF-1 for 18h. Simvastatin inhibited the IGF-1/AKT signaling pathway, resulting in increased breakdown of myofibrillar proteins, impaired protein synthesis and increased apoptosis. Simvastatin inhibited AKT S473 phosphorylation, indicating reduced activity of mTORC2. In addition, simvastatin impaired stimulation of AKT T308 phosphorylation by IGF-1, indicating reduced activation of the IGF-1R/PI3K pathway by IGF-1. Nevertheless, simvastatin-induced myotoxicity could be at least partially prevented by IGF-1. The protective effects of IGF-1 were mediated by activation of the IGF-1R/AKT signaling cascade. Treatment with IGF-1 also suppressed muscle atrophy markers, restored protein synthesis and inhibited apoptosis. These results were confirmed by normalization of myotube morphology and protein content of C2C12 cells exposed to simvastatin and treated with IGF-1. In conclusion, impaired activity of AKT can be explained by reduced function of mTORC2 and of the IGF-1R/PI3K pathway. IGF-1 can prevent simvastatin-associated cytotoxicity and metabolic effects on C2C12 cells. The study gives insight into mechanisms of simvastatin-associated myotoxicity and provides potential targets for therapeutic intervention.

ω-3 fatty acid differentially modulated serum levels of IGF1 and IGFBP3 in men with CVD: A randomized, double-blind placebo-controlled study

ObjectiveStudies have reported elevated serum insulin-like growth factor (IGF)-1 levels followed by ω-3 supplementation in various groups. Considering decreased level of IGF1 in patients with cardiovascular disease (CVD) and protective effects of IGF1 against CVD progression and myocardial infarctions mortality, this study was performed with the aim of determining effects of ω-3 supplementation on serum levels and gene expression of IGF1 and IGF binding protein-3 (IGFBP3) in men with CVD. MethodsSixty-two middle-aged (55.9 ± 6.5 y) non-obese men with CVD followed the study protocol in two groups of ω-3 (n = 31) or placebo (n = 31) supplementation. Participants took ω-3 supplement or placebo (edible paraffin) for 8 wk and were asked not to change their diet or physical activity plan. Anthropometric and lipid profile characteristics, serum IGF1, serum IGFBP3 and also IGF1 and IGFBP3 gene expression in peripheral blood mononuclear cells (PBMCs) were measured in all participants before and after the intervention. Statistical analyses were performed using SPSS software. ResultsThere were no significant differences between the two study groups in age and body mass index at baseline. The groups also had no difference in baseline serum low-density lipoprotein, high-density lipoprotein, very low-density lipoprotein, triacylglycerols, and IGF1. Compared with placebo, ω-3 supplementation increased serum IGF1 levels (P = 0.01), and decreased serum level of IGFBP3 (P = 0.02). There was a trending toward an increase in IGF1 expression and nonsignificant decrease in IGFBP3 expression. Conclusionsω-3 supplementation in patients with CVD increases serum IGF1 levels and decreases serum IGFBP3. Further research is warranted to investigate the underlying mechanisms.

Adipose Tissue-Derived Stem Cell Secreted IGF-1 Protects Myoblasts from the Negative Effect of Myostatin

Myostatin, a TGF-β family member, is associated with inhibition of muscle growth and differentiation and might interact with the IGF-1 signaling pathway. Since IGF-1 is secreted at a bioactive level by adipose tissue-derived mesenchymal stem cells (ASCs), these cells (ASCs) provide a therapeutic option for Duchenne Muscular Dystrophy (DMD). But the protective effect of stem cell secreted IGF-1 on myoblast under high level of myostatin remains unclear. In the present study murine myoblasts were exposed to myostatin under presence of ASCs conditioned medium and investigated for proliferation and apoptosis. The protective effect of IGF-1 was further examined by using IGF-1 neutralizing and receptor antibodies as well as gene silencing RNAi technology. MyoD expression was detected to identify impact of IGF-1 on myoblasts differentiation when exposed to myostatin. IGF-1 was accountable for 43.6% of the antiapoptotic impact and 48.8% for the proliferative effect of ASCs conditioned medium. Furthermore, IGF-1 restored mRNA and protein MyoD expression of myoblasts under risk. Beside fusion and transdifferentiation the beneficial effect of ASCs is mediated by paracrine secreted cytokines, particularly IGF-1. The present study underlines the potential of ASCs as a therapeutic option for Duchenne muscular dystrophy and other dystrophic muscle diseases.

Phosphatidylinositol-3,4,5-trisphosphate is required for insulin-like growth factor 1-mediated survival of 3T3-L1 preadipocytes.

Adipocyte number, a determinant of adipose tissue mass, reflects the balance between the rates of proliferation/differentiation vs. apoptosis of preadipocytes. The percentage of 3T3-L1 preadipocytes undergoing cell death following serum deprivation was reduced by 10 nM insulin-like growth factor (IGF)-1 (from 50.0 +/- 0.7% for control starved cells to 27.5 +/- 3.1%). TUNEL staining confirmed the apoptotic nature of the cell death. The protective effect of IGF-1 was blocked by phosphoinositide 3-kinase (PI3K) inhibitors, wortmannin, and LY294002, but was unaffected by rapamycin, PD98059, or SB203580, which inhibit mammalian target of rapamycin (mTOR), ERK kinase (MEK1), and p38 MAPK respectively. Exogenous PI(3,4,5)P3 (10 microM), the principal product of IGF-1-stimulated PI3K in 3T3-L1 preadipocytes, had a modest survival effect on its own, reducing cell death from 47.9 +/- 3.4% to 35.6 +/- 3.5%. When added to the combination of IGF-1 and LY294002, PI(3,4,5)P3 reversed most of the inhibitory effect of LY294002 on IGF-1-dependent cell survival, protein kinase B/Akt phosphorylation, and caspase-3 activity. Taken together, these results implicate PI(3,4,5)P3 as a necessary signal for the anti-apoptotic action of IGF-1 on 3T3-L1 preadipocytes.

Insulin-Like Growth Factor-1 Inhibition of Apoptosis Is Associated with Increased Expression of the bcl-xL Gene Product

Differentiated PC12 cells, which become dependent on the presence of growth factors in the media and die by apoptosis after several hours of serum deprivation, were used to test the ability of IGF-1 to regulate the endogenous levels of the death-suppressing protein Bcl-xl. IGF-1 was capable of preventing apoptosis of serum-deprived differentiated PC12 cells at physiological concentrations, with optimal results seen at 10−8 M. Incubation with the hormone resulted in a significant increase of Bcl-x mRNA after 3–6 h incubation and a doubling of Bcl-xl protein levels by 24 h incubation. Our results show that the protective effect of IGF-1 in PC12 cells is associated with an up-regulation of Bcl-xl mRNA and protein levels.

Insulin-like growth factor-1 inhibition of apoptosis is associated with increased expression of the bcl-xL gene product.

Differentiated PC12 cells, which become dependent on the presence of growth factors in the media and die by apoptosis after several hours of serum deprivation, were used to test the ability of IGF-1 to regulate the endogenous levels of the death-suppressing protein Bcl-xL, IGF-1 was capable of preventing apoptosis of serum-deprived differentiated PC12 cells at physiological concentrations, with optimal results seen at 10(-8) M. Incubation with the hormone resulted in a significant increase of Bcl-x mRNA after 3-6 h incubation and a doubling of Bcl-xL protein levels by 24 h incubation. Our results show that the protective effect of IGF-1 in PC12 cells is associated with an up-regulation of Bcl-xL mRNA and protein levels.

NEURONAL RESCUE AFTER HYPOXIC ISCHEMIC INJURY (HI) USING INSULIN-LIKE GROWTH FACTOR-1

Many potential therapies are aimed at mechanisms operative during the HI insult and are likely to be relatively ineffective when administered after the event - the usual therapeutic situation. Using in situ hybridisation we have shown that insulinlike growth factor 1 (IGF-I) is induced in astrocytes in the area of neuronal death within 72 h of unilateral HI in 21 day rats. In contrast IGF-2 is not induced until 10 days. Two of the IGF binding proteins (IGFDPs), IGFBP-2 and IGFBP-3 are also induced within 72 h; IGFDP-4, a potent inhibitor of IGF action, is inhibited. IGF-1 was injected via the lateral ventricle 2 hour alter III. There was a dose dependent reduction (p<0.01) in neuronal loss in all damaged areas between 0 find 50 ug IGF-1 (n= 16/group). The infarction rate was reduced (p<0.01) from 87% to 16%. Behavioural testing showed somatosensory function to be protected (p<0.05). IGF-2 and insulin did not cause neural protection suggesting a type I IGF receptor mediated effect. Des 1-3 IGF-1, which has lower affinity for IGFBPs was not neuroprotective compared to IGF-1 (p<0.05) suggesting the role of IGFHP-2 or 3 in the protective effect of IGF-1. Treatment with IGF-1 prior to III was not neuroprotective suggesting that IGF-1 acts on an active mechanism, possibly apoplosis, initiated by the HI. These data show that endogenous IGF-1 production is a specific response to HI and that post-asphyxial IGF-1 therapy is potently neuroprotective and must be considered as a potential neuronal rescue therapy.