IGF-II Receptor Research Articles

Enhanced IGF-IIRα Expression Exacerbates Lipopolysaccharide-Induced Cardiac Inflammation, Hypertrophy, and Apoptosis Through Calcineurin Activation.

Cardiovascular disease is one of the leading causes of death worldwide and has a high prevalence. Insulin-like growth factor-II receptor α (IGF-IIRα) acts as a stress-inducible negative regulator. This study focused on the substantial impact of heightened expression of IGF-IIRα in cardiac myoblasts and its association with the exacerbation of cardiac dysfunction. Using lipopolysaccharide (LPS)-induced H9c2 cardiac myoblasts as a model for sepsis, we aimed to elucidate the molecular interactions between IGF-IIRα and LPS in exacerbating cardiac injury. Our findings demonstrated a synergistic induction of cardiac inflammation and hypertrophy by LPS stimulation and IGF-IIRα overexpression, leading to decreased cell survival. Excessive calcineurin activity, triggered by this combined condition, was identified as a key factor exacerbating the negative effects on cell survival. Cellular changes such as cell enlargement, disrupted actin filaments, and upregulation of hypertrophy-related and inflammation-related proteins contributed to the overall hypertrophic and inflammatory responses. Overexpression of IGF-IIRα also exacerbated apoptosis induced by LPS in H9c2 cardiac myoblasts. Inhibiting calcineurin in LPS-treated H9c2 cardiac myoblasts with IGF-IIRα overexpression effectively reversed the detrimental effects, reducing cell damage and mitigating apoptosis-related cardiac mechanisms. Our study suggests that under sepsis-like conditions in the heart with IGF-IIRα overexpression, hyperactivation of calcineurin worsens cardiac damage. Suppressing IGF-IIRα and calcineurin expression could be a potential intervention to alleviate the impact of the illness and improve cardiac function.

Ohwia caudata inhibits doxorubicin-induced cardiotoxicity by regulating mitochondrial dynamics via the IGF-IIR/p-Drp1/PARP signaling pathway.

The most effective drug, doxorubicin (DOX), is widely used worldwide for clinical application as an anticancer drug. DOX-induced cytotoxicity is characterized by mitochondrial dysfunction. There is no alternative treatment against DOX-induced cardiac damage despite intensive research in the present decades. Ohwia caudata has emerged as a potential herbal remedy that prevents from DOX-induced cytotoxicity owing to its pharmacological action of sustaining mitochondrial dynamics by attenuating oxidative stress and inducing cellular longevity. However, its underlying mechanisms are unknown. The novel treatment provided here depends on new evidence from DOX-treated H9c2 cells, which significantly enhanced insulin-like growth factor (IGF) II receptor (IGF-IIR) pathways that activated calcineurin and phosphorylated dynamin-related protein 1 (p-Drp1) at ser616 (p-Drp1[ser616]); cells undergo apoptosis due to these factors, which translocate to mitochondria and disrupt their function and integrity, and in terms of herbal medicine treatment, which significantly blocked these phenomena. Thus, our findings indicate that maintaining integrity of mitochondria is an essential element in lowering DOX-induced cytotoxicity, which further emphasizes that our herbal medicine can successfully block IGF-IIR pathways and could potentially act as an alternative mechanism in terms of cardioprotective against doxorubicin.

The associations of IGF2, IGF2R and IGF2BP2 gene polymorphisms with gestational diabetes mellitus: A case-control study.

To investigate the associations of Insulin-like growth factor-II (IGF2) gene, Insulin-like growth factor-II receptor (IGF2R) gene and Insulin-like growth factor-II binding protein 2 (IGF2BP2) gene polymorphisms with the susceptibility to gestational diabetes mellitus (GDM) in Chinese population. A total of 1703 pregnant women (835 GDM and 868 Non-GDM) were recruited in this case-control study. All participants underwent prenatal 75 g oral glucose tolerance test (OGTT) examinations during 24-28 gestational weeks at the Maternal and Child Health Hospital of Hubei Province from January 15, 2018 to March 31, 2019. Genotyping of candidate SNPs (IGF2 rs680, IGF2R rs416572, IGF2BP2 rs4402960, rs1470579, rs1374910, rs11705701, rs6777038, rs16860234, rs7651090) was performed on Sequenom MassARRAY platform. Logistic regression analysis was conducted to investigate the associations between candidate SNPs and risk of GDM. In addition, multifactor dimensionality reduction (MDR) method was applied to explore the effects of gene-gene interactions on GDM risk. There were significant distribution differences between GDM group and non-GDM group in age, pre-pregnancy BMI, education level and family history of diabetes (P < 0.05). After adjusted for age, pre-pregnancy BMI, education level and family history of diabetes, there were no significant associations of the candidate SNPs polymorphisms and GDM risk (P > 0.05). Furthermore, there were no gene-gene interactions on the GDM risk among the candidate SNPs (P > 0.05). However, the fasting blood glucose (FBG) levels of rs6777038 CT carriers were significantly lower than TT carriers (4.69±0.69 vs. 5.03±1.57 mmol/L, P < 0.01), and the OGTT-2h levels of rs6777038 CC and CT genotype carriers were significantly lower than TT genotype carriers (8.10±1.91 and 8.08±1.87 vs. 8.99±2.90 mmol/L, P < 0.01). IGF2 rs680, IGF2R rs416572, IGF2BP2 rs4402960, rs1470579, rs11705701, rs6777038, rs16860234, rs7651090 polymorphisms were not significantly associated with GDM risk in Wuhan, China. Further lager multicenter researches are needed to confirm these results.

Insulin-like growth factor family and prostate cancer: new insights and emerging opportunities.

Prostate cancer is the second most commonly diagnosed cancer in men. The mammalian insulin-like growth factor (IGF) family is made up of three ligands (IGF-I, IGF-II, and insulin), three receptors (IGF-I receptor (IGF-1R), insulin receptor (IR), and IGF-II receptor (IGF-2R)), and six IGF-binding proteins (IGFBPs). IGF-I and IGF-II were identified as potent mitogens and were previously associated with an increased risk of cancer development including prostate cancer. Several reports showed controversy about the expression of the IGF family and their connection to prostate cancer risk due to the high degree of heterogeneity among prostate tumors, sampling bias, and evaluation techniques. Despite that, it is clear that several IGF family members play a role in prostate cancer development, metastasis, and androgen-independent progression. In this review, we aim to expand our understanding of prostate tumorigenesis and regulation through the IGF system. Further understanding of the role of IGF signaling in PCa shows promise and needs to be considered in the context of a comprehensive treatment strategy.

Fisetin attenuates doxorubicin-induced cardiotoxicity by inhibiting the insulin-like growth factor II receptor apoptotic pathway through estrogen receptor-α/-β activation.

Doxorubicin (DOX), an effective chemotherapeutic drug, has been used to treat various cancers; however, its cardiotoxic side effects restrict its therapeutic efficacy. Fisetin, a flavonoid phytoestrogen derived from a range of fruits and vegetables, has been reported to exert cardioprotective effects against DOX-induced cardiotoxicity; however, the underlying mechanisms remain unclear. This study investigated fisetin's cardioprotective role and mechanism against DOX-induced cardiotoxicity in H9c2 cardiomyoblasts and ovariectomized (OVX) rat models. MTT assay revealed that fisetin treatment noticeably rescued DOX-induced cell death in a dose-dependent manner. Moreover, western blotting and TUNEL-DAPI staining showed that fisetin significantly attenuated DOX-induced cardiotoxicity in vitro and in vivo by inhibiting the insulin-like growth factor II receptor (IGF-IIR) apoptotic pathway through estrogen receptor (ER)-α/-β activation. The echocardiography, biochemical assay, and H&E staining results demonstrated that fisetin reduced DOX-induced cardiotoxicity by alleviating cardiac dysfunction, myocardial injury, oxidative stress, and histopathological damage. These findings imply that fisetin has a significant therapeutic potential against DOX-induced cardiotoxicity.

Embryonic growth retardation and altered expression of IGF-II is reciprocal induced by phytocompounds during early gestation in mice

Methanolic crude extract of Scoparia dulcis (CESD) was orally administered to female mice during the early gestation (day 4–day 8) at a dose of 500 mg/kg/day. It induces embryo resorption and morphological changes of fetal maternal tissue. Histomorphology was studied by routine hematoxylin eosin stain. In situ immunofluorescence localization of IGF-II using Texas red showed an ordered expression of the growth factor in the maternal decidual cells, trophoblast cells and the embryo. Western blot analysis showed a gradual increase of IGF-II from D4 to D8 of control females. In contrast, the CESD-treated females showed resorption of embryo on D8 with disorganized in situ expression and lowered IGF-II in fetal maternal tissue. The phytocompounds present in the CESD could modulate either the ER or IGF-II receptors causing reduced IGF-II expression in the target tissues which lead to the failure of embryonic growth during periimplantation.

Overexpression of cardiac‐specific IGF‐IIRα accelerates the development of liver dysfunction through STZ‐induced diabetic hepatocyte damage in transgenic rats

This study reports the effect of cardiac-specific insulin-like growth factor-II receptor α (IGF-IIRα) overexpression on the development of liver dysfunction in transgenic rats via STZ-induced diabetic hepatocyte damage. The cardio-hepatic syndrome comprises a number of heart and liver illnesses in which an acute or chronic disease in one organ can lead to acute or chronic disease in the other. However, the molecular mechanism involved in such a set of conditions is unclear. In this study, we developed a transgenic rat model with cardiac-specific overexpression of IGF-IIRα, which is a supplementary splicing variant of insulin-like growth factor-II receptor (IGF-IIR), expressed in pathological hearts, to investigate the relationship between late fetal gene expression in diabetic hearts and their influence on diabetic hepatopathy. STZ (55 mg/kg) was intraperitoneally delivered into IGF-IIR overexpressed transgenic (TG) and non-transgenic (NTG) animal models developed in Sprague-Dawley (SD) rats after an overnight fast. The relationship among IGF-IIRα overexpression and hepatocyte damages have been determined based on the complexity of damage in the liver. Our findings revealed that overexpression of the cardiac-specific IGF-IIRα enhances diabetes-induced morphological alterations and hepatic inflammation in the livers. The diabetic transgenic rats demonstrated the development of pathological conditions such as thick collagen fiber deposition, bridging fibrosis, and elevation of α-SMA and MMP1 related liver fibrosis mechanisms. Our data suggest that IGF-IIRα overexpression in the heart during a pathological state may worsen diabetic hepatopathy in rats.

Transcytosis of tanycytes in the circumventricular organs of adult mouse brain

Tanycytes are specialized ependymal cells lining the ventricular spaces of the adult brain and thereby provide an interface between the cerebrospinal fluid (CSF) and brain parenchyma. They act as energy homeostasis, neuroendocrine regulation, and CSF-brain barrier; however, their functional significance in CSF-brain communication currently remains unknown. In the present study, we investigated the presence of tanycytic transcytosis using fluorescent tracers; a GM1 ligand, cholera toxin B (CTB), and a mannose-6-phosphate/insulin-like growth factor-Ⅱ receptor ligand, wheat germ agglutinin (WGA). Both CTB and WGA were incorporated by tanycytes and then released into brain parenchyma in the circumventricular organs such as the organum vasculosum laminae terminalis, subfornical organ, and median eminence, arcuate nucleus, and medullary central canal. Incorporated fluorescent CTB and WGA were released from tanycytes to distribute at neuronal somata. These results indicate that tanycytes of all examined brain regions possess the transport capability of macromolecules from CSF to brain neurons.

Leu27 IGF-II-induced hypertrophy in H9c2 cardiomyoblasts is ameliorated by saffron by regulation of calcineurin/NFAT and CaMKIIδ signaling.

The insulin-like growth factor II receptor (IGF-IIR) induces myocardial hypertrophy under various pathological conditions like diabetes and hypertension via G protein receptors like Gαq or Gαs. Increased expression of the ligand IGF II and IGF-IIR induces pathological hypertrophy through downstream signaling mediators such as calcineurin, nuclear factor of activated T cells 3 and calcium-calmodulin (CaM)-dependent kinase II (CaMKII)-histone deacetylase 4 (HDAC4). The dried stigma of Crocus sativus L. (saffron) has a long repute as a traditional medicine against various disorders. In the present study, we have investigated whether C. sativus extract (CSE) canameliorate Leu27 IGF-II triggered hypertrophy and have elucidated the underlying mechanism of protection. Additionally, the effects of oleic acid (OA), an activator of calcineurin and CaMKII was investigated thereof. The results demonstrate that CSE can ameliorate Leu27 IGF-II-induced hypertrophy seemingly through regulation of calcineurin-NFAT3 and CaMKII-HDAC4 signaling cascade.

Insulin-like growth factor II prevents oxidative and neuronal damage in cellular and mice models of Parkinson's disease

Oxidative distress and mitochondrial dysfunction, are key factors involved in the pathophysiology of Parkinson's disease (PD). The pleiotropic hormone insulin-like growth factor II (IGF-II) has shown neuroprotective and antioxidant effects in some neurodegenerative diseases. In this work, we demonstrate the protective effect of IGF-II against the damage induced by 1-methyl-4-phenylpyridinium (MPP+) in neuronal dopaminergic cell cultures and a mouse model of progressive PD. In the neuronal model, IGF-II counteracts the oxidative distress produced by MPP + protecting dopaminergic neurons. Improved mitochondrial function, increased nuclear factor (erythroid-derived 2)-like2 (NRF2) nuclear translocation along with NRF2-dependent upregulation of antioxidative enzymes, and modulation of mammalian target of rapamycin (mTOR) signalling pathway were identified as mechanisms leading to neuroprotection and the survival of dopaminergic cells. The neuroprotective effect of IGF-II against MPP + -neurotoxicity on dopaminergic neurons depends on the specific IGF-II receptor (IGF-IIr). In the mouse model, IGF-II prevents behavioural dysfunction and dopaminergic nigrostriatal pathway degeneration and mitigates neuroinflammation induced by MPP+. Our work demonstrates that hampering oxidative stress and normalising mitochondrial function through the interaction of IGF-II with its specific IGF-IIr are neuroprotective in both neuronal and mouse models. Thus, the modulation of the IGF-II/IGF-IIr signalling pathway may be a useful therapeutic approach for the prevention and treatment of PD.

Investigating IGF-II and IGF2R serum markers as predictors of body weight loss following an 8-week acute weight loss intervention: PREVIEW sub-study

BackgroundWeight reduction is effective in preventing T2D however, weight reduction and maintenance is difficult to achieve on a population scale. Serum insulin-like growth factor II (IGF-II) and IGF-II receptor (IGF2R) have been associated with diabetic status and body weight in prior studies and, in addition, IGF-II has been indicated as predictive of future weight change. We measured these serum markers in participants with obesity/overweight and prediabetes from the New Zealand arm of the PREVIEW lifestyle intervention randomised trial before and after an 8-week low energy diet (LED). MethodsTotal IGF-II (n = 223) and soluble IGF2R (n = 151) were measured using commercial ELISA kits on fasted serum samples taken prior to an 8-week LED and also from participants completing the LED. ResultsIGF-II levels were not correlated with baseline body weight although mean levels did significantly decrease following the LED. Change in IGF-II serum level was correlated to fasting glucose change (p = 0.04) but not to weight change. Baseline serum IGF2R was correlated with BMI (p = 0.007) and was significantly higher in Māori compared to European Caucasian participants independent of body weight (p = 0.0016). Following LED, IGF2R change was positively associated with weight change (p = 0.02) when corrected for ethnicity. Pre-LED levels of these serum markers were not predictive of the magnitude of weight loss over the 8 weeks. ConclusionNeither marker was useful in predicting magnitude of short-term weight loss. IGF2R is positively associated with BMI and is higher in Māori compared to European Caucasian individuals.

LPS-enhanced IGF-IIR pathway to induce H9c2 cardiomyoblast cell hypertrophy was attenuated by Carthamus tinctorius extract via IGF-IR activation.

The use of herbs as alternative cardiovascular disease treatment has attracted a great deal of attention owing to their lower toxicity. Whether Carthamus tinctorius extract prevent cardiomyoblast cell hypertrophy remains unclear. The present study was performed to investigate the effect of C tinctorius extract (CTF) on rat cardiomyoblast cell H9c2 and the possible molecular mechanisms. H9c2 cells were treated with lipopolysaccharide (LPS; 2 μg/mL) for 12 hours, subsequently treated with CTF (1-25 μg/mL) The incubation continued for another 24 hours, and the cells were analyzed with actin staining assay, western blot analysis, and siRNA transfection assays. In the present study, the increased cell size induced by LPS was significantly decreased by pretreating at a concentration of 1-25 μg/mL CTF. It was found that CTF could inhibit cardiac hypertrophy induced by LPS and decrease hypertrophic proteins calcineurin, p-GATA-4, GATA-4, atrial natriuretic peptide, and B-type natriuretic peptide levels in H9c2 cells. Additionally, LPS-induced insulin-like growth factor-II receptor (IGF-IIR) hypertrophy pathway was downregulated by CTF. Moreover, IGF-IR siRNA or inhibitors both reversed the CTF effects, confirming that CTF activates IGF-1R to prevent LPS-induced H9c2 cardiomyoblast cell hypertrophy. The current findings indicate that CTF activates IGF-IR to inhibit IGF-IIR signaling pathway which resulted in reducing H9c2 cardiomyoblast cell hypertrophy induced by LPS.

The Neglected Insulin: IGF-II, a Metabolic Regulator with Implications for Diabetes, Obesity, and Cancer.

When originally discovered, one of the initial observations was that, when all of the insulin peptide was depleted from serum, the vast majority of the insulin activity remained and this was due to a single additional peptide, IGF-II. The IGF-II gene is adjacent to the insulin gene, which is a result of gene duplication, but has evolved to be considerably more complicated. It was one of the first genes recognised to be imprinted and expressed in a parent-of-origin specific manner. The gene codes for IGF-II mRNA, but, in addition, also codes for antisense RNA, long non-coding RNA, and several micro RNA. Recent evidence suggests that each of these have important independent roles in metabolic regulation. It has also become clear that an alternatively spliced form of the insulin receptor may be the principle IGF-II receptor. These recent discoveries have important implications for metabolic disorders and also for cancer, for which there is renewed acknowledgement of the importance of metabolic reprogramming.

Synergistic cardiac pathological hypertrophy induced by high-salt diet in IGF-IIRα cardiac-specific transgenic rats.

Stress-induced cardiac hypertrophy leads to heart failure. Our previous studies demonstrate that insulin-like growth factor—II receptor (IGF-IIR) signaling is pivotal to hypertrophy regulation. In this study, we show a novel IGF-IIR alternative spliced transcript, IGF-IIRα (150 kDa) play a key role in high-salt induced hypertrophy mechanisms. Cardiac overexpression of IGF-IIRα and high-salt diet influenced cardiac dysfunction by increasing pathophysiological changes with up-regulation of hypertrophy markers, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP). We found that, cardiac hypertrophy under high-salt conditions were amplified in the presence of IGF-IIRα overexpression. Importantly, high-salt induced angiotensin II type I receptor (AT1R) up regulation mediated IGF-IIR expressions via upstream mitogen activated protein kinase (MAPK)/silent mating type information regulation 2 homolog 1 (SIRT1)/heat shock factor 1 (HSF1) pathway. Further, G-coupled receptors (Gαq) activated calcineurin/nuclear factor of activated T-cells, cytoplasmic 3 (NFATc3)/protein kinase C (PKC) signaling was significantly up regulated under high-salt conditions. All these effects were observed to be dramatically over-regulated in IGF-IIRα transgenic rats fed with a high-salt diet. Altogether, from the findings, we demonstrate that IGF-IIRα plays a crucial role during high-salt conditions leading to synergistic cardiac hypertrophy.

IGF-Mediated Hypoglycemia as the First Manifestation of Huge Hepatocellular Carcinoma (HCC) in a Chronic Hepatitis B Infected Patient

Paraneoplastic hypoglycemia is a rare presentation of HCC1. Treatment for such episode has not been standardized2. Most patients do not respond to intravenous glucose infusion.A 54-year-old male presented with alteration of consciousness. He had anorexia and 20-kilograms weight lost within 4 months, recurrent dizziness and palpitations which improved with food intake for 2 weeks. Physical examination revealed enlarged liver. No sign of chronic liver stigmata was noted. Others were unremarkable. Hypoglycemia was diagnosed by plasma glucose of 21 mg/dL. Serum insulin and C-peptide level was <2 μIU/mL (8.9-28.4) and 0.3 ng/mL (0.9-7.1), respectively, suggestive of insulin-like growth factor (IGF)-mediated hypoglycemia. CT scan showed 16 cm-arterial enhancing and delayed wash-out mass with central necrosis, occupying almost entire right lobe on non-cirrhotic liver (pic 1). The mass abutted right portal vein, no metastatic foci was seen. Alpha-fetoprotein was 52,300 IU/mL. Diagnosis of HCC was made. The etiology of HCC was chronic hepatitis B infection. HBV DNA was 319 IU/mL. Initially, continuous intravenous glucose infusion of 8 gm/h was given, but hypoglycemia persisted. Continuous glucose infusion of 10 gm/hr with frequent meals was required to maintain blood glucose level above 80 mg/dL. On admission day 3, TACE was done to reduce tumor burden. The need for glucose infusion was rapidly decreased and can be stopped within 3 days after TACE procedure (pic 2). Hepatectomy was successfully performed 1 month after diagnosis. Pathologic examination showed bizarre multinucleated giant tumor cell compatible with moderately differentiated HCC grade III-IV (pic 3).2449_A Figure 1. Picture1.CT abdomen revealed 16 cm hypo-density mass occupying right hepatic lobe with arterial enhancing, delayed wash-out rim and central necrosis.2449_B Figure 2. Level of capillary glucose and amount of glucose infusion during hospitalization2449_C Figure 3. Picture 3. Bizarre multinucleated giant tumor cell compatible with moderately differentiated hepatocellular carcinoma grade III-IVHypoglycemia presenting as the first manifestation of HCC, particularly in non-cirrhotic patients is very rare1. It is caused by production of HCC peptides with insulin-like structure and bioactivity, e.g. IGF-II. IGF-II binds to the IGF-I, IGF-II, and insulin receptors, resulting in dramatic increasing glucose uptake.2 The mainstay of HCC treatment is to reduce tumor burden. Our patient had dramatic response to TACE, followed by surgical resection. After resection for 4 months, the patient was doing well without signs of HCC recurrence.

Interactive effects of salinity and complete fishmeal replacement on growth, food consumption, and gene expression of hepatic IGF-I, IGF-II and growth hormone receptors in Nile tilapia,Oreochromis niloticus(L.)

A 12-week feeding trial was conducted using Nile tilapia, Oreochromis niloticus (L.) to evaluate the interactive effects of fishmeal replacement and salinity on growth, feed utilization efficiencies and relative expression of growth related genes. Two iso-nitrogenous and iso-energetic diets were prepared (32% protein). The control diet included 15% fishmeal (FM diet) and fishmeal component in non-fishmeal diet (NFM) was eliminated by a mixture of poultry by-product meal, high protein distillers dried grains and distillers dried grains with soluble. The NFM diet was supplemented with DL-methionine and L-lysine. Duplicated group of fish with initial mean weight of 6 g, reared in four salinity levels (0, 4, 8 and 12 g/L) were fed one of the two diets twice a day to near satiety. At the end of the experiment, growth, feed utilization efficiency and expression of growth related genes were compared. The specific growth rate (SGR), mean feed intake (MFI) and feed conversion ratio (FCR) were not affected by the diets while salinity effects were significant. The fish in the 4 g/L salinity showed the highest SGR and MFI while fish in the 0 g/L treatment showed the lowest FCR. Relative expression of hepatic IGF-I and IGF-II was regulated by salinity but not by the diet. Expression of growth hormone receptor gene was not affected by either diet or salinity. The present findings provide evidence for the possibility of total fishmeal replacement in saline waters (0–12 g/L) without compromising growth, feed utilization and body composition of Nile tilapia.

Deficiency of liver-derived insulin-like growth factor-I (IGF-I) does not interfere with the skin wound healing rate.

ObjectiveIGF-I is a growth factor, which is expressed in virtually all tissues. The circulating IGF-I is however derived mainly from the liver. IGF-I promotes wound healing and its levels are decreased in wounds with low regenerative potential such as diabetic wounds. However, the contribution of circulating IGF-I to wound healing is unknown.Here we investigated the role of systemic IGF-I on wound healing rate in mice with deficiency of liver-derived IGF-I (LI-IGF-I-/- mice) during normal (normoglycemic) and impaired wound healing (diabetes).MethodsLI-IGF-I-/- mice with complete inactivation of the IGF-I gene in the hepatocytes were generated using the Cre/loxP recombination system. This resulted in a 75% reduction of circulating IGF-I. Diabetes was induced with streptozocin in both LI-IGF-I-/- and control mice. Wounds were made on the dorsum of the mice, and the wound healing rate and histology were evaluated. Serum IGF-I and GH were measured by RIA and ELISA respectively. The expression of IGF-I, IGF-II and the IGF-I receptor in the skin were evaluated by qRT-PCR. The local IGF-I protein expression in different cell types of the wounds during wound healing process was analyzed using immunohistochemistry.ResultsThe wound healing rate was similar in LI-IGF-I-/- mice to that in controls. Diabetes significantly delayed the wound healing rate in both LI-IGF-I-/- and control mice. However, no significant difference was observed between diabetic animals with normal or reduced hepatic IGF-I production. The gene expression of IGF-I, IGF-II and IGF-I receptor in skin was not different between any group of animals tested. Local IGF-I levels in the wounds were similar between of LI-IGF-I-/- and WT mice although a transient reduction of IGF-I expression in leukocytes in the wounds of LI-IGF-I-/- was observed seven days post wounding.ConclusionDeficiency in the liver-derived IGF-I does not affect wound healing in mice, neither in normoglycemic conditions nor in diabetes.

Potential role of insulin receptor isoforms and IGF receptors in plaque instability of human and experimental atherosclerosis

BackgroundClinical complications associated with atherosclerotic plaques arise from luminal obstruction due to plaque growth or destabilization leading to rupture. We previously demonstrated that overexpression of insulin receptor isoform A (IRA) and insulin-like growth factor-I receptor (IGF-IR) confers a proliferative and migratory advantage to vascular smooth muscle cells (VSMCs) promoting plaque growth in early stages of atherosclerosis. However, the role of insulin receptor (IR) isoforms, IGF-IR or insulin-like growth factor-II receptor (IGF-IIR) in VSMCs apoptosis during advanced atherosclerosis remains unclear.MethodsWe evaluated IR isoforms expression in human carotid atherosclerotic plaques by consecutive immunoprecipitations of insulin receptor isoform B (IRB) and IRA. Western blot analysis was performed to measure IGF-IR, IGF-IIR, and α-smooth muscle actin (α-SMA) expression in human plaques. The expression of those proteins, as well as the presence of apoptotic cells, was analyzed by immunohistochemistry in experimental atherosclerosis using BATIRKO; ApoE−/− mice, a model showing more aggravated vascular damage than ApoE−/− mice. Finally, apoptosis of VSMCs bearing IR (IRLoxP+/+ VSMCs), or not (IR−/− VSMCs), expressing IRA (IRA VSMCs) or expressing IRB (IRB VSMCs), was assessed by Western blot against cleaved caspase 3.ResultsWe observed a significant decrease of IRA/IRB ratio in human complicated plaques as compared to non-complicated regions. Moreover, complicated plaques showed a reduced IGF-IR expression, an increased IGF-IIR expression, and lower levels of α-SMA indicating a loss of VSMCs. In experimental atherosclerosis, we found a significant decrease of IRA with an increased IRB expression in aorta from 24-week-old BATIRKO; ApoE−/− mice. Furthermore, atherosclerotic plaques from BATIRKO; ApoE−/− mice had less VSMCs content and higher number of apoptotic cells. In vitro experiments showed that IGF-IR inhibition by picropodophyllin induced apoptosis in VSMCs. Apoptosis induced by thapsigargin was lower in IR−/− VSMCs expressing higher IGF-IR levels as compared to IRLoxP+/+ VSMCs. Finally, IRB VSMCs are more prone to thapsigargin-induced apoptosis than IRA or IRLoxP+/+ VSMCs.ConclusionsIn advanced human atherosclerosis, a reduction of IRA/IRB ratio, decreased IGF-IR expression, or increased IGF-IIR may contribute to VSMCs apoptosis, promoting plaque instability and increasing the risk of plaque rupture and its clinical consequences.

Takifugu rubripes cation independent mannose 6-phosphate receptor: Cloning, expression and functional characterization of the IGF-II binding domain

Mannose 6-phosphate/IGF-II receptor mediated lysosomal clearance of insulin-like growth factor-II is significantly associated with the evolution of placental mammals. The protein is also referred to as the IGF-II receptor. Earlier studies suggested relatively low binding affinity between the receptor and ligand in prototherian and metatherian mammals. In the present study, we cloned the IGF-II binding domain of the early vertebrate fugu fish and expressed it in bacteria. A 72000Da truncated receptor containing the IGF-II binding domain was obtained. Analysis of this protein (covering domains 11–13 of the CIMPR) for its affinity to fish and human IGF-II by ligand blot assays and ELISA showed that the expressed receptor can specifically bind to both fish and human IGF-II. Additionally, a peptide-specific antibody raised against the region of the IGF-II binding domain also was able to recognize the IGF-II binding regions of mammalian and non-mammalian cation independent MPR protein. These interactions were further characterized by Surface Plasma resonance support that the receptor binds to fish IGF-II, with a dissociation constant of 548nM. Preliminary analysis suggests that the binding mechanism as well as the affinity of the fish and human receptor for IGF-II may have varied according to different evolutionary pressures.

Serum from Chronic Hepatitis B Patients Promotes Growth and Proliferation via the IGF-II/IGF-IR/MEK/ERK Signaling Pathway in Hepatocellular Carcinoma Cells

Background/Aims: Chronic hepatitis B virus (HBV) infection (CHB) plays a central role in the etiology of hepatocellular carcinoma (HCC). Emerging evidence implicates insulin-like growth factor (IGF)-II as a major risk factor for the growth and development of HCC. However, the relationship between HBV infection and IGF-II functions remains to be elucidated. Methods: Levels of circulating IGF-II and IGF-I receptor (IGF-IR) in healthy donors (HDs) and CHB patients were tested by ELISA. Human HCC cell lines (HepG-2, SMMC-7721, MHCC97-H) were incubated with serum from HDs and CHB patients at various concentrations for 24, 48, and 72 h. MTT and plate colony formation assays, BrdU ELISA, ELISA, small-interfering RNA (siRNA) transfection, quantitative real-time PCR, and western blot were applied to assess the functional and molecular mechanisms in HCC cell lines. Results: Serum levels of IGF-II and IGF-IR were significantly higher in CHB patients than in HDs. Additionally, serum from CHB patients directly induced cell growth, proliferation, IGF-II secretion, and HDGF-related protein-2 (HRP-2) and nuclear protein 1 (NUPR1) mRNA and protein expression in HCC cells. Moreover, serum from CHB patients increased IGF-II–induced cell growth, proliferation, and HRP-2 and NUPR1 mRNA and protein expression in HCC cells. Blockade of IGF-IR clearly inhibited the above effects. Most importantly, interference with IGF-II function markedly repressed the cell proliferation and HRP-2 and NUPR1 mRNA and protein expression induced by serum from CHB patients. Furthermore, serum from CHB patients induced ERK phosphorylation via IGF-IR, with the MEK inhibitor PD98059 significantly decreasing CHB patient serum-induced IGF-II secretion, cell proliferation, and HRP-2 and NUPR1 mRNA and protein expression. Conclusion: Serum from CHB patients increases cell growth and proliferation and enhances HRP-2 and NUPR1 expression in HCC cells via the IGF-II/IGF-IR/MEK/ERK signaling pathway. These findings help to explain the molecular mechanisms underlying HBV-related HCC and may lead to the development of effective therapies.