Implication of insulin receptor A isoform and IRA/IGF-IR hybrid receptors in the aortic vascular smooth muscle cell proliferation: role of TNF-α and IGF-II

Identifying antisense oligonucleotides for targeted inhibition of insulin receptor isoform A

Introduction

The insulin receptor (IR) is alternatively spliced into two isoforms, IR-A and IR-B. IR-B is primarily associated with metabolic signaling, whereas IR-A is highly expressed during embryogenesis. IR-A specifically has been associated with several aggressive cancers; however, selective targeting of IR-A has proven difficult due to its homology with IR-B.

Methods

We generated several antisense oligonucleotides (ASOs) that target the exon 10-12 splice junction site present in IR-A, but not IR-B, mRNA. To test the efficacy of the ASOs, we performed lipofectamine transfections of MDA-MB-231 breast cancer, 22Rv1 prostate carcinoma, and Hs822.T Ewing sarcoma cell lines. We also incubated the MDA-MB-231 cell line with the ASOs in the absence of lipofectamine to determine if they are taken into cells unassisted.

Results

One ASO variant selectively reduced IR-A mRNA levels with minimal impact on IR-B mRNA and significantly reduced total IR protein. The IR-A ASO successfully induced selective IR-A knockdown in MDA-MB-231 breast cancer cells, which was maintained after a one-week incubation with the ASO. The ASO selectively reduced IR-A mRNA when administered to cells in high doses without the use of a vehicle (i.e. gymnotic delivery). The ASO was also effective at reducing IR-A mRNA in Hs822.T Ewing Sarcoma and 22Rv1 prostate carcinoma cells.

Discussion

We have developed an ASO that targets IR-A with minimal off-target knockdown of IR-B. We hypothesize that the IR-A ASO will be a useful research tool and may have therapeutic value by inhibiting the oncogenic functions of IR-A in cancer cells.

Potential protective role of let-7d-5p in atherosclerosis progression reducing the inflammatory pathway regulated by NF-κB and vascular smooth muscle cells proliferation

The prevalence of cardiovascular diseases (CVDs) is increasing in the last decades, even is the main cause of death in first world countries being atherosclerosis one of the principal triggers. Therefore, there is an urgent need to decipher the underlying mechanisms involved in atherosclerosis progression. In this respect, microRNAs dysregulation is frequently involved in the progression of multiple diseases including CVDs. Our aim was to demonstrate that let-7d-5p unbalance could contribute to the pathophysiology of atherosclerosis and serve as a potential diagnostic biomarker. We evaluated let-7d-5p levels in vascular biopsies and exosome-enriched extracellular vesicles (EVs) from patients with carotid atherosclerosis and healthy donors. Moreover, we overexpressed let-7d-5p in vitro in vascular smooth muscle cells (VSMCs) to decipher the targets and the underlying mechanisms regulated by let-7d-5p in atherosclerosis. Our results demonstrate that let-7d-5p was significantly upregulated in carotid plaques from overweight patients with carotid atherosclerosis. Moreover, in EVs isolated from plasma, we found that let-7d-5p levels were increased in carotid atherosclerosis patients compared to control subjects specially in overweight patients. Receiver Operating Characteristic (ROC) analyses confirmed its utility as a diagnostic biomarker for atherosclerosis. In VSMCs, we demonstrated that increased let-7d-5p levels impairs cell proliferation and could serve as a protective mechanism against inflammation by impairing NF-κB pathway without affecting insulin resistance. In summary, our results highlight the role of let-7d-5p as a potential therapeutic target for atherosclerosis since its overexpression induce a decrease in inflammation and VSMCs proliferation, and also, as a novel non-invasive diagnostic biomarker for atherosclerosis in overweight patients.

Implication of miR-155-5p and miR-143-3p in the Vascular Insulin Resistance and Instability of Human and Experimental Atherosclerotic Plaque

(1) Background: Cardiovascular diseases (CVDs) are the main cause of death in developed countries, being atherosclerosis, a recurring process underlying their apparition. MicroRNAs (miRNAs) modulate the expression of their targets and have emerged as key players in CVDs; (2) Methods: 18 miRNAs were selected (Pubmed and GEO database) for their possible role in promoting atherosclerosis and were analysed by RT-qPCR in the aorta from apolipoprotein E-deficient (ApoE^−/−) mice. Afterwards, the altered miRNAs in the aorta from 18 weeks-ApoE^−/− mice were studied in human aortic and carotid samples; (3) Results: miR-155-5p was overexpressed and miR-143-3p was downregulated in mouse and human atherosclerotic lesions. In addition, a significant decrease in protein kinase B (AKT), target of miR-155-5p, and an increase in insulin-like growth factor type II receptor (IGF-IIR), target of miR-143-3p, were noted in aortic roots from ApoE^−/− mice and in carotid plaques from patients with advanced carotid atherosclerosis (ACA). Finally, the overexpression of miR-155-5p reduced AKT levels and its phosphorylation in vascular smooth muscle cells, while miR-143-3p overexpression decreased IGF-IIR reducing apoptosis in vascular cells; (4) Conclusions: Our results suggest that miR-155-5p and miR-143-3p may be implicated in insulin resistance and plaque instability by the modulation of their targets AKT and IGF-IIR, contributing to the progression of atherosclerosis.

Concerted regulation of non-alcoholic fatty liver disease progression by microRNAs in apolipoprotein E-deficient mice

The prevalence of non-alcoholic fatty liver disease (NAFLD) is constantly increasing, and altered expression of microRNAs (miRNAs) fosters the development and progression of many pathologies, including NAFLD. Therefore, we explored the role of new miRNAs involved in the molecular mechanisms that trigger NAFLD progression and evaluated them as biomarkers for diagnosis. As a NAFLD model, we used apolipoprotein E-deficient mice administered a high-fat diet for 8 or 18 weeks. We demonstrated that insulin resistance and decreased lipogenesis and autophagy observed after 18 weeks on the diet are related to a concerted regulation carried out by miR-26b-5p, miR-34a-5p, miR-149-5p and miR-375-3p. We also propose circulating let-7d-5p and miR-146b-5p as potential biomarkers of early stages of NAFLD. Finally, we confirmed that circulating miR-34a-5p and miR-375-3p are elevated in the late stages of NAFLD and that miR-27b-3p and miR-122-5p are increased with disease progression. Our results reveal a synergistic regulation of key processes in NAFLD development and progression by miRNAs. Further investigation is needed to unravel the roles of these miRNAs for developing new strategies for NAFLD treatment.

This article has an associated First Person interview with the joint first authors of the paper.

Summary:Apoe^−/− mice administered a high-fat diet represent a model of non-alcoholic fatty liver disease, revealing the synergistic regulation of key processes in disease progression by miRNAs and indicating some miRNAs as biomarkers for diagnosis.

Insulin signaling is an essential regulator of endometrial proliferation and implantation in mice

Insulin signaling is critical for the development of preovulatory follicles and progression through the antral stage. Using a conditional knockout model that escapes this blockage, we recently described the role of insulin signaling in granulosa cells during the periovulatory window in mice lacking Insr and Igf1r driven by Pgr-Cre. These mice were infertile, exhibiting defects in ovulation, luteinization, steroidogenesis, and early embryo development. Herein, we demonstrate that while these mice exhibit normal uterine receptivity, uterine cell proliferation and decidualization are compromised resulting in complete absence of embryo implantation in uteri lacking both receptors. While the histological organization of double knockout mice appeared normal, the thickness of their endometrium was significantly reduced. This was supported by the reduced proliferation of both epithelial and stromal cells during the preimplantation stages of pregnancy. Expression and localization of the main drivers of uterine proliferation, ESR1 and PGR, was normal in knockouts, suggesting that insulin signaling acts downstream of these two receptors. While AKT/PI3K signaling was unaffected by insulin receptor ablation, activation of p44/42 MAPK was significantly reduced in both single and double knockout uteri at 3.5 dpc. Overall, we conclude that both INSR and IGF1R are necessary for optimal endometrial proliferation and implantation.

Insulin-Like Growth Factor 2 (IGF2) Signaling in Colorectal Cancer-From Basic Research to Potential Clinical Applications

Colorectal cancer (CRC) is one of the most common cancers in men and women worldwide as well as is the leading cause of death in the western world. Almost a third of the patients has or will develop liver metastases. While genetic as well as epigenetic mechanisms are important in CRC pathogenesis, the basis of the most cases of cancer is unknown. High spatial and inter-patient variability of the molecular alterations qualifies this cancer in the group of highly heterogeneous tumors, which makes it harder to elucidate the mechanisms underlying CRC progression. Determination of highly sensitive and specific early diagnosis markers and understanding the cellular and molecular mechanism(s) of cancer progression are still a challenge of the current era in oncology of solid tumors. One of the accepted risk factors for CRC development is overexpression of insulin-like growth factor 2 (IGF2), a 7.5-kDa peptide produced by liver and many other tissues. IGF2 is the first gene discovered to be parentally imprinted. Loss of imprinting (LOI) or aberrant imprinting of IGF2 could lead to IGF2 overexpression, increased cell proliferation, and CRC development. IGF2 as a mitogen is associated with increased risk of developing colorectal neoplasia. Higher serum IGF2 concentration as well as its tissue overexpression in CRC compared to control are associated with metastasis. IGF2 protein was one of the three candidates for a selective marker of CRC progression and staging. Recent research indicates dysregulation of different micro- and long non-coding RNAs (miRNAs and lncRNAs, respectively) embedded within the IGF2 gene in CRC carcinogenesis, with some of them indicated as potential diagnostic and prognostic CRC biomarkers. This review systematises the knowledge on the role of genetic and epigenetic instabilities of IGF2 gene, free (active form of IGF2) and IGF-binding protein (IGFBP) bound (inactive form), paracrine/autocrine secretion of IGF2, as well as mechanisms of inducing dysplasia in vitro and tumorigenicity in vivo. We have tried to answer which molecular changes of the IGF2 gene and its regulatory mechanisms have the most significance in initiation, progression (including liver metastasis), prognosis, and potential anti-IGF2 therapy in CRC patients.

Chronic Exercise Improves Mitochondrial Function and Insulin Sensitivity in Brown Adipose Tissue

The aim of the present work was to study the consequences of chronic exercise training on factors involved in the regulation of mitochondrial remodeling and biogenesis, as well as the ability to produce energy and improve insulin sensitivity and glucose uptake in rat brown adipose tissue (BAT). Male Wistar rats were divided into two groups: (1) control group (C; n = 10) and (2) exercise-trained rats (ET; n = 10) for 8 weeks on a motor treadmill (five times per week for 50 min). Exercise training reduced body weight, plasma insulin, and oxidized LDL concentrations. Protein expression of ATP-independent metalloprotease (OMA1), short optic atrophy 1 (S-OPA1), and dynamin-related protein 1 (DRP1) in BAT increased in trained rats, and long optic atrophy 1 (L-OPA1) and mitofusin 1 (MFN1) expression decreased. BAT expression of nuclear respiratory factor type 1 (NRF1) and mitochondrial transcription factor A (TFAM), the main factors involved in mitochondrial biogenesis, was higher in trained rats compared to controls. Exercise training increased protein expression of sirtuin 1 (SIRT1), peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α) and AMP-activated protein kinase (pAMPK/AMPK ratio) in BAT. In addition, training increased carnitine palmitoyltransferase II (CPT II), mitochondrial F1 ATP synthase α-chain, mitochondrial malate dehydrogenase 2 (mMDH) and uncoupling protein (UCP) 1,2,3 expression in BAT. Moreover, exercise increased insulin receptor (IR) ratio (IRA/IRB ratio), IRA-insulin-like growth factor 1 receptor (IGF-1R) hybrids and p42/44 activation, and decreased IGF-1R expression and IR substrate 1 (p-IRS-1) (S307) indicating higher insulin sensitivity and favoring glucose uptake in BAT in response to chronic exercise training. In summary, the present study indicates that chronic exercise is able to improve the energetic profile of BAT in terms of increased mitochondrial function and insulin sensitivity.

Diabetes and hepatocellular carcinoma: A pathophysiological link and pharmacological management

Both diabetes mellitus (DM) and cancer are multifarious, dissimilar, and long-lasting, fatal diseases with a remarkable influence on health worldwide. DM is not only related to cardiovascular diseases, neuropathy, nephropathy, and retinopathy, but also related to a number of liver diseases such as nonalcoholic fatty liver disease, steatohepatitis, and liver cirrhosis. Recently, it is hypothesized that DM has a greater risk for many forms of cancer, such as breast, colorectal, endometrial, pancreatic, gallbladder, renal, and liver cancer including hepatocellular carcinoma (HCC). Both DM and cancer have many common risk factors, but the association between these two is poorly stated. Several epidemiologic studies have revealed the association between pathogenic and prognostic characteristics of DM and a higher incidence of HCC, thus representing DM as an independent risk factor for HCC development. The etiological and pathophysiological relationship between DM and HCC has been presented in this review by linking hyperglycemia, hyperinsulinemia, insulin resistance, and activation of insulin-like growth factor signaling pathways and pharmacological management of HCC associated with DM.

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

BACKGROUND

Clinical 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.

METHODS

We 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.

RESULTS

We 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.

CONCLUSIONS

In 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.

Insulin Receptor Isoforms in Physiology and Disease: An Updated View

The insulin receptor (IR) gene undergoes differential splicing that generates two IR isoforms, IR-A and IR-B. The physiological roles of IR isoforms are incompletely understood and appear to be determined by their different binding affinities for insulin-like growth factors (IGFs), particularly for IGF-2. Predominant roles of IR-A in prenatal growth and development and of IR-B in metabolic regulation are well established. However, emerging evidence indicates that the differential expression of IR isoforms may also help explain the diversification of insulin and IGF signaling and actions in various organs and tissues by involving not only different ligand-binding affinities but also different membrane partitioning and trafficking and possibly different abilities to interact with a variety of molecular partners. Of note, dysregulation of the IR-A/IR-B ratio is associated with insulin resistance, aging, and increased proliferative activity of normal and neoplastic tissues and appears to sustain detrimental effects. This review discusses novel information that has generated remarkable progress in our understanding of the physiology of IR isoforms and their role in disease. We also focus on novel IR ligands and modulators that should now be considered as an important strategy for better and safer treatment of diabetes and cancer and possibly other IR-related diseases.

Insulin promotes proliferation and migration of breast cancer cells through the extracellular regulated kinase pathway

The present study was undertaken to determine the roles of insulin in the growth of transplanted breast cancer in nude mice, and the proliferation and migration of MCF-7 human breast cancer cells and assess its influence on downstream signaling pathways. In a xenograft mouse model with injection of MCF-7 human breast cancer cells, tumor size was measured every other day. The insulin level and insulin receptor (IR) were increased in the breast cancer patient tissues. Insulin injected subcutaneously around the tumor site in mice caused increase in the size and weight of tumor masses, and promoted proliferation and migration of MCF-7 cells. The effects of insulin on the increase in the proliferation and migration of MCF-7 human breast cancer cells were abolished by pretreatment with the extracellular regulated kinase (ERK) inhibitor PD98059. Insulin increased the phosphorylation of ERK in the MCF-7 cells. These results indicate that insulin promotes the growth of breast cancer in nude mice, and increases the proliferation and migration of MCF-7 human breast cancer cells via the ERK pathway.

The Role of Insulin Receptor Isoforms in Diabetes and Its Metabolic and Vascular Complications

The insulin receptor (IR) presents by alternative splicing two isoforms: IRA and IRB. The differential physiological and pathological role of both isoforms is not completely known, and it is determinant the different binding affinity for insulin-like growth factor. IRB is more abundant in adult tissues and it exerts mainly the metabolic actions of insulin, whereas IRA is mainly expressed in fetal and prenatal period and exerts mitogenic actions. However, the change in the expression profile of both IR isoforms and its dysregulation are associated with the development of different pathologies, such as cancer, insulin resistance, diabetes, obesity, and atherosclerosis. In some of them, there is a significant increase of IRA/IRB ratio conferring a proliferative and migratory advantage to different cell types and favouring IGF-II actions with a sustained detriment in the metabolic effects of insulin. This review discussed specifically the role of IR isoforms as well as IGF-IR in diabetes and its associated complications as obesity and atherosclerosis. Future research with new IR modulators might be considered as possible targets to improve the treatment of diabetes and its associated complications.

Expression of insulin receptor (IR) A and B isoforms, IGF-IR, and IR/IGF-IR hybrid receptors in vascular smooth muscle cells and their role in cell migration in atherosclerosis

Background

Abnormal proliferation and migration of vascular smooth muscle cells (VSMCs) is a major contributor to the development of atherosclerotic process. In a previous work, we demonstrated that the insulin receptor isoform A (IRA) and its association with the insulin-like growth factor-I receptor (IGF-IR) confer a proliferative advantage to VSMCs. However, the role of IR and IGF-IR in VSMC migration remains poorly understood.

Methods

Wound healing assays were performed in VSMCs bearing IR (IRLoxP^+/+ VSMCs), or not (IR^−/− VSMCs), expressing IRA (IRA VSMCs) or expressing IRB (IRB VSMCs). To study the role of IR isoforms and IGF-IR in experimental atherosclerosis, we used ApoE^−/− mice at 8, 12, 18 and 24 weeks of age. Finally, we analyzed the mRNA expression of total IR, IRB isoform, IGF-IR and IGFs by qRT-PCR in the medial layer of human aortas.

Results

IGF-I strongly induced migration of the four cell lines through IGF-IR. In contrast, insulin and IGF-II only caused a significant increase of IRA VSMC migration which might be favored by the formation of IRA/IGF-IR receptors. Additionally, a specific IGF-IR inhibitor, picropodophyllin, completely abolished insulin- and IGF-II-induced migration in IRB, but not in IRA VSMCs. A significant increase of IRA and IGF-IR, and VSMC migration were observed in fibrous plaques from 24-week-old ApoE^−/− mice. Finally, we observed a marked increase of IGF-IR, IGF-I and IGF-II in media from fatty streaks as compared with both healthy aortas and fibrolipidic lesions, favoring the ability of medial VSMCs to migrate into the intima.

Conclusions

Our data suggest that overexpression of IGF-IR or IRA isoform, as homodimers or as part of IRA/IGF-IR hybrid receptors, confers a stronger migratory capability to VSMCs as might occur in early stages of atherosclerotic process.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0477-3) contains supplementary material, which is available to authorized users.

Ox-LDL Upregulates IL-6 Expression by Enhancing NF-κB in an IGF2-Dependent Manner in THP-1 Macrophages

Interleukin 6 (IL-6) is a pro-inflammatory cytokine that is well established as a vital factor in determining the risk of coronary heart disease and pathogenesis of atherosclerosis. Moreover, accumulating evidences have shown that oxidized low-density lipoprotein (ox-LDL) can promote IL-6 expression in macrophages. Nevertheless, the underlying mechanism of how ox-LDL upregulates IL-6 expression remains largely unexplained. We found that the expression of insulin-like growth factor 2 (IGF2), nuclear factor kappa B (NF-κB), and IL-6 was upregulated at both the messenger RNA (mRNA) and protein levels in a dose-dependent manner when treated with 0, 25, 50, or 100 μg/mL of ox-LDL for 48 h in THP-1 macrophages. Moreover, overexpression of IGF2 significantly upregulated NF-κB and IL-6 expressions in THP-1 macrophages. However, the upregulation of NF-κB and IL-6 expressions induced by ox-LDL were significantly abolished by IGF2 small interfering RNA (siRNA) in THP-1 macrophages. Further studies indicated the upregulation of IL-6 induced by ox-LDL could be abolished when treated with NF-κB siRNA in THP-1 macrophages. Ox-LDL might upregulate IL-6 in the cell and its secretion via enhancing NF-κB in an IGF2-dependent manner in THP-1 macrophages.

Differential Expression of IR-A, IR-B and IGF-1R in Endometrial Physiology and Distinct Signature in Adenocarcinoma

CONTEXT

Type 2 diabetes and obesity are risk factors for endometrial hyperplasia and cancer, suggesting that hyperinsulinemia contributes to pathogenesis. Insulin action through insulin receptor (IR) splice variants IR-A and IR-B regulates cellular mitogenesis and metabolism, respectively.

OBJECTIVE

We hypothesized that IR-A and IR-B are differentially regulated in normal endometrium, according to mitogenic and metabolic requirements through the menstrual cycle, as well as in endometrial hyperplasia and cancer.

DESIGN

IR-A, IR-B, and IGF-1 receptor (IGF-1R) mRNA was quantified in endometrium, endometrial epithelial and stromal cells, and in vitro after hormone stimulation.

SETTING

Academic center.

PATIENTS

Endometrium was collected from women with regular cycles (n = 71), complex hyperplasia (n = 5), or endometrioid adenocarcinoma (n = 11).

INTERVENTION(S)

In vitro sex-steroid treatment.

MAIN OUTCOME MEASURE(S)

IR-A and IR-B expression Results: IR-A increased dramatically during the early proliferative phase, 20-fold more than IR-B. In early secretory phase, IR-B and IGF-1R expression increased, reaching maximal expression, whereas IR-A decreased. In adenocarcinoma, IR-B and IGF-1R expression was 5- to 6-fold higher than normal endometrium, whereas IR-A expression was similar to IR-B. Receptor expression was unrelated to body mass index.

CONCLUSION

IR-A was elevated during the normal proliferative phase, and in endometrial hyperplasia and adenocarcinoma. The dramatic early rise of IR-A in normal endometrium indicates IR-A is the predominant isoform responsible for initial estrogen-independent endometrial proliferation as well as that of cancer. IR-B is elevated during the normal secretory phase when glucose uptake and glycogen synthesis support embryo development. Differing from other cancers, IR-B expression equals mitogenic IR-A in endometrial adenocarcinoma. Differential IR isoform expression suggests a distinct role for each in endometrial physiology and cancer.

Insulin receptor isoforms: an integrated view focused on gestational diabetes mellitus

The human insulin receptor (IR) exists in two isoforms that differ by the absence (IR-A) or the presence (IR-B) of a 12-amino acid segment encoded by exon 11. Both isoforms are functionally distinct regarding their binding affinities and intracellular signalling. However, the underlying mechanisms related to their cellular functions in several tissues are only partially understood. In this review, we summarize the current knowledge in this field regarding the alternative splicing of IR isoform, tissue-specific distribution and signalling both in physiology and disease, with an emphasis on the human placenta in gestational diabetes mellitus (GDM). Furthermore, we discuss the clinical relevance of IR isoforms highlighted by findings that show altered insulin signalling due to differential IR-A and IR-B expression in human placental endothelium in GDM pregnancies. Future research and clinical studies focused on the role of IR isoform signalling might provide novel therapeutic targets for treating GDM to improve the adverse maternal and neonatal outcomes.

Protective role of oleic acid against cardiovascular insulin resistance and in the early and late cellular atherosclerotic process

BACKGROUND

Several translational studies have identified the differential role between saturated and unsaturated fatty acids at cardiovascular level. However, the molecular mechanisms that support the protective role of oleate in cardiovascular cells are poorly known. For these reasons, we studied the protective role of oleate in the insulin resistance and in the atherosclerotic process at cellular level such as in cardiomyocytes (CMs), vascular smooth muscle cells (VSMCs) and endothelial cells (ECs).

METHODS

The effect of oleate in the cardiovascular insulin resistance, vascular dysfunction, inflammation, proliferation and apoptosis of VSMCs were analyzed by Western blot, qRT-PCR, BrdU incorporation and cell cycle analysis.

RESULTS

Palmitate induced insulin resistance. However, oleate not only did not induce cardiovascular insulin resistance but also had a protective effect against insulin resistance induced by palmitate or TNFα. One mechanism involved might be the prevention by oleate of JNK-1/2 or NF-κB activation in response to TNF-α or palmitate. Oleate reduced MCP-1 and ICAM-1 and increased eNOS expression induced by proinflammatory cytokines in ECs. Furthermore, oleate impaired the proliferation induced by TNF-α, angiotensin II or palmitate and the apoptosis induced by TNF-α or thapsigargin in VSMCs.

CONCLUSIONS

Our data suggest a differential role between oleate and palmitate and support the concept of the cardioprotector role of oleate as the main lipid component of virgin olive oil. Thus, oleate protects against cardiovascular insulin resistance, improves endothelial dysfunction in response to proinflammatory signals and finally, reduces proliferation and apoptosis in VSMCs that may contribute to an ameliorated atherosclerotic process and plaque stability.

Inhibition of microRNA-25 by tumor necrosis factor α is critical in the modulation of vascular smooth muscle cell proliferation

Atherosclerosis and coronary heart disease are characterized by a hyperplastic neointima and inflammation involving cytokines, such as tumor necrosis factor‑α (TNF‑α). TNF‑α is pleiotropic and mediates inflammation and proliferation in various cell types, such as vascular smooth muscle cells (VSMCs). The molecular mechanism for the pleiotropic effects of TNF‑α has not previously been fully elucidated. The current study identified that the expression of microRNA‑25 (miR‑25), a small noncoding RNA, was reduced in response to TNF‑α signaling in VSMCs. Restored miR‑25 expression inhibited cell proliferation and Ki‑67 expression. The present study indicated that cyclin‑dependent kinase 6 (CDK6) was the direct target gene of miR‑25 using mRNA and protein expression analysis, and luciferase assays. It was also observed that restored CDK6 expression in the miR‑25 mimic‑treated VSMCs partly reduced miR‑25‑mediated VSMC proliferation. In conclusion, miR‑25 is suggested to be important in TNF‑α‑induced abnormal proliferation of VSMCs.

The Insulin-Like Growth Factor System in Obesity, Insulin Resistance and Type 2 Diabetes Mellitus

The insulin-like growth factor (IGF) system, acting in concert with other hormone axes, is important in normal metabolism. In obesity, the hyperinsulinaemia that accompanies peripheral insulin resistance leads to reduced growth hormone (GH) secretion, while total IGF-I levels are relatively unchanged due to increased hepatic GH sensitivity. IGF-binding protein (IGFBP)-1 levels are suppressed in relation to the increase in insulin levels in obesity and low levels predict the development of type 2 diabetes several years later. Visceral adiposity and hepatic steatosis, along with a chronic inflammation, contribute to the IGF system phenotype in individuals with metabolic syndrome and type 2 diabetes mellitus, including changes in the normal inverse relationship between IGFBP-1 and insulin, with IGFBP-1 concentrations that are inappropriately normal or elevated. The IGF system is implicated in the vascular and other complications of these disorders and is therefore a potential therapeutic target.

Short hairpin RNA-mediated silencing of insulin-like growth factor-Ⅰ receptor inhibits proliferation of hepatoma cells

AIM: To investigate the effect of short hairpin RNA (shRNA)-mediated silencing of insulin-like growth factor-Ⅰ  receptor (IGF-ⅠR) gene transcription on cell proliferation, cell cycle progression, apoptosis and sensitivity to targeted therapy and chemotherapy in hepatocellular carcinoma (HCC) cell lines PLC/PRF/5 and Bel-7404.

METHODS: Pairs of IGF-ⅠR shRNAs were designed and synthesized based on the IGF-ⅠR sequence, and inserted into the pGPU6/GFP/Neo vector to screen the most effective one. IGF-ⅠR expression was then down-regulated with the shRNA to observe its inhibitory effect on hepatoma cell proliferation.

RESULTS: After screening, the IGF-ⅠR-shRNA4 was found to be the most efficient one for interfering IGF-ⅠR gene transcription among the 4 pairs of successfully constructed plasmids, with a transfection efficiency of 71% in PLC/PRF/5 cells and 90% in Bel-7404 cells. The expression of IGF-ⅠR mRNA was down-regulated by 59.6% ± 2.8% in PLC/PRF/5 cells and 54.9% ± 2.6% in Bel-7404 cells. After the cells was transfected with shRNA4 for 72 h, the reduced rate of cell proliferation was 61.47% ± 1.70% in Bel-7404 cells (t = 5.493, P < 0.005) and 63.87 ± 3.90% (t = 19.244, P < 0.001) in PLC/PRF/5 cells. Meanwhile, the cell cycle was arrested in the G1 phase, and the expression of Cyclin D1 was significantly down-regulated with increasing cell apoptosis. Besides, the combination of shRNA4 with sorafenib or oxaliplatin showed higher inhibitory effects on cell survival than shRNA4 alone.

CONCLUSION: Silencing IGF-ⅠR gene transcription can inhibit hepatoma cell proliferation, induce apoptosis and enhance the sensitivity to targeted therapy and chemotherapy. IGF-ⅠR may be a potential target gene for HCC gene therapy.

Antagonistic effect of TNF-alpha and insulin on uncoupling protein 2 (UCP-2) expression and vascular damage

Background

It has been reported that increased expression of UCP-2 in the vasculature may prevent the development of atherosclerosis in patients with increased production of reactive oxygen species, as in the diabetes, obesity or hypertension. Thus, a greater understanding in the modulation of UCP-2 could improve the atherosclerotic process. However, the effect of TNF-α or insulin modulating UCP-2 in the vascular wall is completely unknown. In this context, we propose to study new molecular mechanisms that help to explain whether the moderate hyperinsulinemia or lowering TNF-α levels might have a protective role against vascular damage mediated by UCP-2 expression levels.

Methods

We analyzed the effect of insulin or oleic acid in presence or not of TNF-α on UCP-2 expression in murine endothelial and vascular smooth muscle cells. At this step, we wondered if some mechanisms studied in vitro could be of any relevance in vivo. We used the following experimental models: ApoE^−/− mice under Western type diet for 2, 6, 12 or 18 weeks, BATIRKO mice under high-fat diet for 16 weeks and 52-week-old BATIRKO mice with o without anti-TNF-α antibody pre-treatment.

Results

Firstly, we found that TNF-α pre-treatment reduced UCP-2 expression induced by insulin in vascular cells. Secondly, we observed a progressive reduction of UCP-2 levels together with an increase of lipid depots and lesion area in aorta from ApoE^−/− mice. In vivo, we also observed that moderate hyperinsulinemic obese BATIRKO mice have lower TNF-α and ROS levels and increased UCP-2 expression levels within the aorta, lower lipid accumulation, vascular dysfunction and macrovascular damage. We also observed that the anti-TNF-α antibody pre-treatment impaired the loss of UCP-2 expression within the aorta and relieved vascular damage observed in 52-week-old BATIRKO mice. Finally, we observed that the pretreatment with iNOS inhibitor prevented UCP-2 reduction induced by TNF-α in vascular cells. Moreover, iNOS levels are augmented in aorta from mice with lower UCP-2 levels and higher TNF-α levels.

Conclusions

Our data suggest that moderate hyperinsulinemia in response to insulin resistance or lowering of TNF-α levels within the aorta attenuates vascular damage, this protective effect being mediated by UCP-2 expression levels through iNOS.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-014-0108-9) contains supplementary material, which is available to authorized users.