Omentin inhibits osteoblastic differentiation of calcifying vascular smooth muscle cells through the PI3K/Akt pathway

Omentin-General Overview of Its Role in Obesity, Metabolic Syndrome and Other Diseases; Problem of Current Research State

Background: Omentin (omentin-1, intelectin-1, ITLN-1) is an adipokine considered to be a novel substance. Many chronic, inflammatory, or civilization diseases are linked to obesity, in which omentin plays a significant role. Methods: MEDLINE and SCOPUS databases were searched using the keywords "omentin" or "intelectin-1". Then the most recent articles providing new perspectives on the matter and the most important studies, which revealed crucial insight, were selected to summarize the current knowledge on the role of omentin in a literature review. Results and Conclusions: The valid role of this adipokine is evident in the course of metabolic syndrome. In most cases, elevated omentin expression is correlated with the better course of diseases, including: type 2 diabetes mellitus, polycystic ovary syndrome, rheumatoid arthritis, metabolic dysfunction-associated steatotic liver disease, Crohn's disease, ulcerative colitis, atherosclerosis, or ischemic stroke, for some of which it can be a better marker than the currently used ones. However, results of omentin studies are not completely one-sided. It was proven to participate in the development of asthma and atopic dermatitis and to have different concentration dynamics in various types of tumors. All of omentin's effects and properties make it an attractive subject of research, considering still unexplored inflammation mechanisms, in which it may play an important role. Omentin was proven to prevent osteoarthritis, hepatocirrhosis, and atherosclerosis in mouse models. All of the above places omentin among potential therapeutic products, and not only as a biomarker. However, the main problems with the omentin's research state are the lack of standardization, which causes many contradictions and disagreements in this field.

Omentin-1 and diabetes: more evidence but far from enough

AIMS AND BACKGROUND

Omentin-1 (oment-1) is a type of adipokines that is mainly expressed in visceral fat tissue. Based on accumulating evidence, oment-1 is closely related to diabetes and its complications. However, so far data about oment-1 and diabetes is fragmented. In this review, we focus on the role of oment-1 on diabetes, including its possible signalling pathways, the correlation of circulating omens-1 levels with diabetes and its complications.

METHODS

The web of PubMed was searched for articles of relevant studies published until February, 2023.

RESULTS AND CONCLUSIONS

Oment-1 might exert its effects by inhibiting the NF-κB pathway and activating the Akt and AMPK-dependent pathways. The level of circulating oment-1 is negatively correlated with the occurrence of type 2 diabetes and some complications, including diabetic vascular disease, cardiomyopathy, and retinopathy, which can be affected by anti-diabetic therapies. Oment-1 could be a promising marker for screening and targeted therapy for diabetes and its complications; however, more studies are still needed.

Omentin reduces venous neointimal hyperplasia in arteriovenous fistula through hypoxia-inducible factor-1 alpha inhibition

Arteriovenous fistula (AVF) failure often involves venous neointimal hyperplasia (VNH) driven by elevated hypoxia-inducible factor-1 alpha (HIF-1α) in the venous wall. Omentin, known for its anti-inflammatory and anti-hyperplasia properties, has an uncertain role in early AVF failure. This study investigates omentin's impact on VNH using a chronic renal failure (CRF) rabbit model. The CRF rabbit model of AVF received omentin-expressing adenoviral vector or control β-gal vector to assess omentin's effects on VNH. Human vascular smooth muscle cells (HVSMCs), stimulated with tumor necrosis factor-α (TNF-α), were exposed to recombinant human omentin (Rh-OMT) to study its influence on cell proliferation and migration. The AMP-activated protein kinase (AMPK) inhibitor compound C and the mammalian target of rapamycin (mTOR) activator MHY1485 were employed to explore omentin's mechanisms in VNH reduction through HIF-1α inhibition. Omentin treatment reduced VNH in CRF rabbits, concomitant with HIF-1α down-regulation and the suppression of downstream factors, including vascular endothelial growth factor and matrix metalloproteinases. Rh-OMT inhibited TNF-α-induced HVSMC proliferation and migration by modulating both cell cycle and cell adhesion proteins. Additionally, omentin reduced HIF-1α expression through the AMPK/mTOR pathway activation. Notably, the blockade of AMPK/mTOR signaling reversed omentin-mediated inhibition of VNH, cell proliferation, and migration, both in vivo and in vitro. In conclusion, omentin mitigates VNH post-AVF creation by restraining HIF-1α via AMPK/mTOR signaling. Strategies boosting circulating omentin levels may offer promise in averting AVF failure.

Regulation of cardiovascular health and disease by visceral adipose tissue-derived metabolic hormones

Visceral adipose tissue (VAT) is a metabolic organ known to regulate fat mass, and glucose and nutrient homeostasis. VAT is an active endocrine gland that synthesizes and secretes numerous bioactive mediators called 'adipocytokines/adipokines' into systemic circulation. These adipocytokines act on organs of metabolic importance like the liver and skeletal muscle. Multiple preclinical and in vitro studies showed strong evidence of the roles of adipocytokines in the regulation of metabolic disorders like diabetes, obesity and insulin resistance. Adipocytokines, such as adiponectin and omentin, are anti-inflammatory and have been shown to prevent atherogenesis by increasing nitric oxide (NO) production by the endothelium, suppressing endothelium-derived inflammation and decreasing foam cell formation. By inhibiting differentiation of vascular smooth muscle cells (VSMC) into osteoblasts, adiponectin and omentin prevent vascular calcification. On the other hand, adipocytokines like leptin and resistin induce inflammation and endothelial dysfunction that leads to vasoconstriction. By promoting VSMC migration and proliferation, extracellular matrix degradation and inflammatory polarization of macrophages, leptin and resistin increase the risk of atherosclerotic plaque vulnerability and rupture. Additionally, the plasma concentrations of these adipocytokines alter in ageing, rendering older humans vulnerable to cardiovascular disease. The disturbances in the normal physiological concentrations of these adipocytokines secreted by VAT under pathological conditions impede the normal functions of various organs and affect cardiovascular health. These adipokines could be used for both diagnostic and therapeutic purposes in cardiovascular disease.

A Role of IL-17 in Rheumatoid Arthritis Patients Complicated With Atherosclerosis

Rheumatoid arthritis (RA) is mainly caused by joint inflammation. RA significantly increases the probability of cardiovascular disease. Although the progress of RA has been well controlled recently, the mortality of patients with RA complicated with cardiovascular disease is 1.5–3 times higher than that of patients with RA alone. The number of people with atherosclerosis in patients with RA is much higher than that in the general population, and atherosclerotic lesions develop more rapidly in patients with RA, which has become one of the primary factors resulting in the death of patients with RA. The rapid development of atherosclerosis in RA is induced by inflammation-related factors. Recent studies have reported that the expression of IL-17 is significantly upregulated in patients with RA and atherosclerosis. Simultaneously, there is evidence that IL-17 can regulate the proliferation, migration, and apoptosis of vascular endothelial cells and vascular smooth muscle cells through various ways and promote the secretion of several cytokines leading to the occurrence and development of atherosclerosis. Presently, there is no clear prevention or treatment plan for atherosclerosis in patients with RA. Therefore, this paper explores the mechanism of IL-17 in RA complicated with atherosclerosis and shows the reasons for the high incidence of atherosclerosis in patients with RA. It is hoped that the occurrence and development of atherosclerosis in patients with RA can be diagnosed or prevented in time in the early stage of lesions, and the prevention and treatment of cardiovascular complications in patients with RA can be enhanced to reduce mortality.

Omentin‑1 induces osteoblast viability and differentiation via the TGF‑β/Smad signaling pathway in osteoporosis

Osteoporosis is a bone-related disease that results from impaired bone formation and excessive bone resorption. The potential value of adipokines has been investigated previously, due to their influence on osteogenesis. However, the osteogenic effects induced by omentin-1 remain unclear. The aim of the present study was to determine the regulatory effects of omentin-1 on osteoblast viability and differentiation, as well as to explore the underlying molecular mechanism. The present study investigated the effects of omentin-1 on the viability and differentiation of mouse pre-osteoblast cells (MC3T3-E1) using quantitative and qualitative measures. A Cell Counting Kit-8 assay was used to assess the viability of MC3T3-E1 cells following treatment with different doses of omentin-1. Omentin-1 and bone morphogenetic protein (BMP) inhibitor were added to osteogenic induction mediums in different ways to assess their effect. The alkaline phosphatase (ALP) activity and Alizarin Red S (ARS) staining of MC3T3-E1 cells treated with omentin-1 and/or BMP inhibitor were used to examine the effects of omentin-1 on differentiation and mineralization. Western blotting was used to further explore its potential mechanism, and to study the role of omentin-1 on the viability and differentiation of osteoblasts. The results showed that omentin-1 altered the viability of MC3T3-E1 cells in a dose-dependent manner. Omentin-1 treatment significantly increased the expression of members of the TGF-β/Smad signaling pathway. In the omentin-1 group, the ALP activity of the MC3T3-E1 cells was increased, and the ARS staining area was also increased. The mRNA and protein expression levels of BMP2, Runt-related transcription factor 2, collagen1, osteopontin, osteocalcin and osterix in the omentin-1 group were also significantly upregulated. All these effects were reversed following treatment with SIS3 HCl. These results demonstrated that omentin-1 can significantly promote osteoblast viability and differentiation via the TGF-β/Smad signaling pathway, thereby promoting bone formation and preventing osteoporosis.

Omentin-1: A newly discovered warrior against metabolic related diseases

INTRODUCTION

: Chronic metabolism-related diseases are challenging clinical problems. Omentin-1 is mainly expressed in stromal vascular cells of adipose tissue and can also be expressed in airway goblet cells, mesothelial cells, and vascular cells. Omentin-1 has been found to exert important anti-inflammatory, antioxidative and anti-apoptotic roles and to regulate endothelial dysfunction. Moreover, omentin-1 also has protective effects against cancer, atherosclerosis, type 2 diabetes mellitus, and bone metabolic diseases. The current review will discuss the therapeutic potential of omentin-1.

AREAS COVERED

: This review summarizes the biological actions of omentin-1 and provides an overview of omentin-1 in metabolic-related diseases. The relevant literature was derived from a PubMed search spanning 1998-2021 using these search terms: omentin-1, atherosclerosis, diabetes mellitus, bone, cancer, inflammation, and oxidative stress.

EXPERT OPINION

: As a novel adipocytokine, omentin-1 is a promising therapeutic target in metabolic-related diseases. Preclinical animal studies have shown encouraging results. Moreover, circulating omentin-1 has excellent potential as a noninvasive biomarker. In the future, strategies for regulating omentin-1 need to be investigated further in clinical trials in a large cohort.

Disturbances of the Gut Microbiota, Sleep Architecture, and mTOR Signaling Pathway in Patients with Severe Obstructive Sleep Apnea-Associated Hypertension

Intermittent hypoxia and sleep fragmentation are pathophysiological processes involved in obstructive sleep apnea (OSA) which affect gut microbiota, sleep architecture, and mTOR signaling pathway. However, the involvement of these elements in the pathogenesis mechanism of OSA-associated hypertension remains unclear. Therefore, this study investigated whether the OSA-associated hypertension mechanism is regulated by the gut microbiota and mTOR signaling pathway. Patients were diagnosed by polysomnography; their fecal samples were obtained and analyzed for their microbiome composition by 16S ribosomal RNA pyrosequencing and bioinformatics analysis. Transcript genes on fasting peripheral blood mononuclear cells (PBMCs) were examined using Illumina RNA-sequencing analysis. Totally, we enrolled 60 patients with severe OSA [without hypertension (n = 27) and with hypertension (n = 33)] and 12 controls (neither OSA nor hypertension). Results revealed that severe-OSA patients with hypertension had an altered gut microbiome, decreased short-chain fatty acid-producing bacteria (P < 0.05), and reduced arginine and proline metabolism pathways (P=0.001), compared with controls; also, they had increased stage N1 sleep and reduced stages N2 and N3 sleep accompanied by repeated arousals (P < 0.05). Analysis of PBMCs using the Kyoto Encyclopedia of Genes and Genomes database showed that the mTOR signaling pathway (P=0.006) was the most important differential gene-enriched pathway in severe-OSA patients with hypertension. Our findings extend prior work and suggest a possibility that the regulation of the mTOR signaling pathway is involved in developing OSA-associated hypertension through its interaction with the disturbance of the gut microbiome and sleep architecture.

Omentin attenuates angiotensin II-induced abdominal aortic aneurysm formation in apolipoprotein-E knockout mice

AIMS

Abdominal aortic aneurysm (AAA) is an increasing and life-threatening disease. Obesity contributes to an increased risk of AAA. Omentin is a circulating adipokine, which is downregulated in obese complications. Here we examined whether omentin could modulate angiotensin (Ang) II-induced AAA formation in apolipoprotein-E knockout (apoE-KO) mice.

METHODS AND RESULTS

ApoE-KO mice were crossed with transgenic mice expressing the human omentin gene in fat tissue (OMT-Tg mice) to generate ApoE-KO/OMT-Tg mice. ApoE-KO/OMT-Tg and apoE-KO mice were subjected to continuous Ang II infusion by using osmotic mini pumps. ApoE-KO/OMT-Tg mice exhibited a lower incidence of AAA formation and a reduced maximal diameter of AAA compared with apo-E KO mice. ApoE-KO/OMT-Tg mice showed attenuated disruption of medial elastic fibers in response to Ang II compared with apo-E KO mice. ApoE-KO/OMT-Tg mice also displayed reduced expression levels of matrix metalloproteinase (MMP) 9, MMP2 and pro-inflammatory genes in aortic walls compared with apo-E KO mice. Furthermore, systemic administration of omentin also attenuated AAA formation and disruption of medial elastic fibers in response to Ang II in apoE-KO mice. Treatment of human monocyte-derived macrophages with omentin protein attenuated expression of MMP9 and pro-inflammatory mediators, and MMP9 activation after stimulation with lipopolysaccharide (LPS). Treatment of human vascular smooth muscle cells with omentin protein reduced expression and activation of MMP2 after stimulation with tumor necrosis factor α. Omentin treatment increased phosphorylation levels of Akt in human macrophages and vascular smooth muscle cells. The suppressive effects of omentin on MMP9 and MMP2 expression were reversed by inhibition of integrin-αVβ3/PI3-kinase/Akt signaling in macrophages and vascular smooth muscle cells, respectively.

CONCLUSION

These data suggest that omentin acts as an adipokine that can attenuate Ang II-induced development of AAA through suppression of MMP9 and MMP2 expression and inflammatory response in the vascular wall.

Omentin-1: Protective impact on ischemic stroke via ameliorating atherosclerosis

Omentin-1, a newly identified adipokine, has recently been revealed as a novel biomarker for ischemic stroke (IS). Low circulating omentin-1 levels could indicate a high risk of IS, and elevated omentin-1 levels exert a favorable impact on cerebral ischemia. Furthermore, omentin-1 has anti-atherosclerotic, anti-inflammatory, and cardiovascular protective capabilities through the intracellular Akt/AMP-activated protein kinase (AMPK)/ nuclear factor-κB (NF-κB) and certain protein kinase (ERK, JNK, and p38) signaling pathways. Omentin-1 also alleviates endothelial cell dysfunction, improves revascularization via the Akt-endothelial nitric-oxide synthase (eNOS) regulatory axis, promotes endothelium-dependent vasodilation through endothelium-derived NO in an eNOS fashion, and inhibits VSMC proliferation by means of AMPK/ERK signaling pathways, VSMC migration via inactivation of the NADPH oxidase (NOX)/ROS/p38/HSP27 pathways and artery calcification via the PI3K-Akt pathway. These findings indicate that omentin-1 may be a negative mediator of IS. Pharmacologically, several lines of clinical evidence indicate that metformin and statins could elevate omentin-1 levels, although the specific mechanism has not been precisely delineated until now. This study is the first to summarize the comprehensive mechanisms between omentin-1 and atherosclerosis and to review the shielding effect of omentin-1 on IS. We shed light on omentin-1 as a novel therapeutic target for combating IS.

Adipokines in vascular calcification

Adipose tissue (AT), a critical endocrine gland, is capable of producing and secreting abundant adipokines. Adipokines act on distant or adjacent organ tissues via paracrine, autocrine, and endocrine mechanism, which play attractive roles in the regulation of glycolipid metabolism and inflammatory response. Increasing evidence shows that adipokines can connect obesity with cardiovascular diseases by serving as promoters or inhibitors in vascular calcification. The chronic hypoxia in AT, caused by the adipocyte hypertrophy, is able to trigger imbalanced adipokine generation, which leads to apoptosis, osteogenic differentiation of vascular smooth muscle cells (VSMCs), vascular inflammation, and abnormal deposition of calcium and phosphorus in the vessel wall. The objectives of this review aim at providing a brief summary of the crucial influence of major adipokines on the formation and development of vascular calcification, which may contribute to better understanding these adipokines for establishing the appropriate therapeutic strategies to counteract obesity-associated vascular calcification.

Adipokines: New Potential Therapeutic Target for Obesity and Metabolic, Rheumatic, and Cardiovascular Diseases

Besides its role as an energy storage organ, adipose tissue can be viewed as a dynamic and complex endocrine organ, which produces and secretes several adipokines, including hormones, cytokines, extracellular matrix (ECM) proteins, and growth and vasoactive factors. A wide body of evidence showed that adipokines play a critical role in various biological and physiological functions, among which feeding modulation, inflammatory and immune function, glucose and lipid metabolism, and blood pressure control. The aim of this review is to summarize the effects of several adipokines, including leptin, diponectin, resistin, chemerin, lipocalin-2 (LCN2), vaspin, omentin, follistatin-like 1 (FSTL1), secreted protein acidic and rich in cysteine (SPARC), secreted frizzled-related protein 5 (SFRP5), C1q/TNF-related proteins (CTRPs), family with sequence similarity to 19 member A5 (FAM19A5), wingless-type inducible signaling pathway protein-1 (WISP1), progranulin (PGRN), nesfatin-1 (nesfatin), visfatin/PBEF/NAMPT, apelin, retinol binding protein 4 (RPB4), and plasminogen activator inhibitor-1 (PAI-1) in the regulation of insulin resistance and vascular function, as well as many aspects of inflammation and immunity and their potential role in managing obesity-associated diseases, including metabolic, osteoarticular, and cardiovascular diseases.

Insight into adipokines to optimize therapeutic effects of stem cell for tissue regeneration

Stem cell therapy is considered as a promising regenerative medicine for repairing and treating damaged tissues and/or preventing various diseases. But there are still some obstacles such as low cell migration, poor stem cell engraftment and decreased cell survival that need to be overcome before transplantation. Therefore, a large body of studies has focused on improving the efficiency of stem cell therapy. For instance, preconditioning of stem cells has emerged as an effective strategy to reinforce therapeutic efficacy. Adipokines are signaling molecules, secreted by adipose tissue, which regulate a variety of biological processes in adipose tissue and other organs including the brain, liver, and muscle. In this review article, we shed light on the biological effects of some adipokines including apelin, oncostatin M, omentin-1 and vaspin on stem cell therapy and the most recent preclinical advances in our understanding of how these functions ameliorate stem cell therapy outcome.

The Relation of Omentin-1 Levels and Some Trace Elements as a Potential Markers for Diagnosis of Prediabetic Obese Patients

The obesity is one of the most common physiological disorders, also it is linked with a variety of circumstances like hypertension, dyslipidemia, T2DM, non-alcoholic fatty liver disease, and cardiovascular diseases. The aim of this study was to check the changes and compare serum omentin-1, lipid profile (TC, TG, VLDL-C, LDL-C, and HDL-C), trace elements (Mg, Zn, Cu, Fe) and insulin resistance between the prediabetic obese patients, healthy obese, and control subjects and assess the correlation between omentin-1, lipid profile, trace elements (Mg, Zn, Cu, Fe) levels and insulin resistance in prediabetic obese patients. Correlation analysis between omentin-1 levels with the biochemical parameters in the prediabetic obese patients with WC, body mass index, FBG, Insulin, HOMA-IR, HbA1c, TG, TC, LDL-C, VLDL-C, and copper was found to be negative; while significant positive correlation of omentin-1 with HDL-C, Mg, Zn, and Fe was noticed. Omentin-1 serum concentration level decrease and insulin resistance increased in prediabetic obese patients compared to healthy obese and control individuals. Omentin-1 inversely associated with obesity and insulin resistance, therefore can be used as a biomarker for obesity related metabolic disorders.

Adipose tissue-derived omentin-1 attenuates arterial calcification via AMPK/Akt signaling pathway

Adipose tissue-derived adipokines mediate various kind of crosstalk between adipose tissue and other organs and thus regulate metabolism balance, inflammation state as well as disease progression. In particular, omentin-1, a newly found adipokine, has been reported to exhibit anti-calcification effects in vitro and in vivo. However, little is known about the function of endogenous adipose tissue-derived omentin-1 in arterial calcification and the detailed mechanism involved. Here, we demonstrated that global omentin-1 knockout (omentin-1^-/-) resulted in more obvious arterial calcification in 5/6-nephrectomy plus high phosphate diet treated (5/6 NTP) mice while overexpression of omentin-1 attenuated attenuates osteoblastic differentiation and mineralisation of VSMCs in vitro and 5/6 NTP-induced mice arterial calcification in vivo. Moreover, we found that omentin-1 induced AMPK and Akt activation while inhibition of AMP-activated protein kinase (AMPK) and Akt signaling reversed the anti-calcification effect induced by omentin-1 both in vitro and in vivo. Our results suggest that adipose tissue-derived omentin-1 serves as a potential therapeutic target for arterial calcification and cardiovascular disease.

Tanshinone IIA Promotes Macrophage Cholesterol Efflux and Attenuates Atherosclerosis of apoE-/- Mice by Omentin-1/ABCA1 Pathway

BACKGROUND

Tanshinone IIA (Tan IIA) and Omentin-1 have a protective role in the cardiovascular system. However, if and how Tan IIA and Omentin-1 regulate cholesterol metabolism in macrophages has not been fully elucidated.

OBJECTIVE

To investigate the possible mechanisms of Tan IIA and Omentin-1 on preventing macrophage cholesterol accumulation and atherosclerosis development.

METHODS

The effect of Tan IIA on the protein and mRNA levels of Omentin-1 and ATP-binding cassette transporter A1 (ABCA1) in macrophages was examined by Western blot and qRT-PCR assay, respectively. Cholesterol efflux was assessed by liquid scintillation counting (LSC). Cellular lipid droplet was measured by Oil Red O staining, and intracellular lipid content was detected by high performance liquid chromatography (HPLC). In addition, the serum lipid profile of apoE-/- mice was measured by enzymatic method. The size of atherosclerotic lesion areas and content of lipids and collagen in the aortic of apoE-/- mice were examined by Sudan IV, Oil-red O, and Masson staining, respectively.

RESULTS

Tan IIA up-regulated expression of Omentin-1 and ABCA1 in THP-1 macrophages, promoting ABCA1-mediated cholesterol efflux and consequently decreasing cellular lipid content. Consistently, Tan IIA increased reverse cholesterol transport in apoE-/- mice. Plasma levels of high-density lipoprotein cholesterol (HDL-C), ABCA1 expression and atherosclerotic plaque collagen content were increased while plasma levels of low-density lipoprotein cholesterol (LDL-C) and atherosclerotic plaque sizes were reduced in Tan IIA-treated apoE-/- mice. These beneficial effects were, however, essentially blocked by knockdown of Omentin-1.

CONCLUSION

Our results revealed that Tan IIA promotes cholesterol efflux and ameliorates lipid accumulation in macrophages most likely via the Omentin-1/ABCA1 pathway, reducing the development of aortic atherosclerosis.

Serum omentin-1 levels in type 2 diabetic obese women in relation to glycemic control, insulin resistance and metabolic parameters

Background

Omentin-1 a new anti-inflammatory adipokine has been identified as a major visceral (omental) secretory adipokine which plays important roles in glucose homeostasis, lipid metabolism, insulin resistance and diabetes. The aim of our study was to evaluate serum omentin-1 levels in type 2 diabetic obese females and assess its relation with glycemic control, insulin resistance and metabolic parameters.

Methods

The study included 60 obese type 2 diabetic females and 30 healthy female subjects formed the control group. They subjected to full clinical examination, weight, height, waist and hip circumference. Fasting (blood glucose, insulin, lipid profile, omentin-1) and HbA1c were measured. BMI and HOMA-IR were calculated. Our data analyzed and expressed in terms of mean ± SD. Pearson correlation performed to study the correlation of serum omentin-1 in relation to glycemic control, insulin resistance and metabolic parameters in the studied groups.

Results

We found significant decrease in serum omentin-1 levels in cases with mean ± SD (16.5 ± 2.6 pg/ml) compared to controls (25.3 ± 1.0 pg/ml) (P < 0.001). We also found strong significant negative correlations between serum omentin-1 and (BMI, fasting insulin, HOMA-IR) (r = −0.909, −0.853, −0.511) respectively (P < 0.001) and systolic blood pressure (r = −0.274, p = 0.031). The best cut off point of serum omentin-1 was 22.2 pg/ml to differentiate cases from controls using ROC curve analysis.

Conclusion

Our study has shown significant low levels of serum omentin-1 in obese type 2 diabetic females in comparison to healthy subjects. Omentin-1 inversely related to obesity, insulin resistance and SBP. No significant associations with glycemic control and fasting lipids. Serum omentin-1 can be used as a biomarker for obesity related metabolic disorders.

Omentin-1 ameliorates the attachment of the leukocyte THP-1 cells to HUVECs by targeting the transcriptional factor KLF2

Oxidation of low-density lipoproteins (ox-LDL) plays a critical role in endothelial dysfunction and the pathological progression of atherosclerosis by causing leukocyte attachment to endothelial surfaces. Omentin-1, an important adipokine primarily secreted by stromal vascular cells, has displayed various biological functions in diverse tissues. However, little information regarding the effects of omentin-1 on ox-LDL- induced endothelial dysfunction has been reported before. In the current study, we found that omentin-1 significantly reduced the attachment of the leukocyte THP-1 cells to human umbilical vein endothelial cells (HUVECs) in a dose dependent manner. Additionally, omentin-1 treatment prevented the expression of cell adhesion molecules such as VCAM-1 and E-selectin at both the mRNA level and the protein level. Notably, we found that omentin-1 significantly restored ox-LDL-induced reduction of KLF2, an important transcriptional factor and regulator of endothelial function. Also, omentin-1 promoted the expression of KLF2 target genes eNOS and PAI-1. Mechanistically, our results indicate that the effects of omentin-1 on KLF2 expression are mediated by p53. These results highlight the potential of omentin-1 in preventing endothelial dysfunction and atherosclerosis.

Omentin-A Novel Adipokine in Respiratory Diseases

Adipokines, secreted by the adipose tissue, are extensively involved in the regulation and maintenance of various physiological and pathological processes, including insulin sensitivity, energy expenditure, glucose and lipid metabolism, inflammatory activity, neuroendocrine activity, immunity, cancer, homeostasis, angiogenesis, cardiovascular function, breeding and bone metabolism, and all functions of the endocrine-reproductive system axis. Omentin is a recently identified adipokine, which has become a research hotspot due to its pleiotropic effects on various diseases. However, the specific receptor for omentin has not been identified so far. In this study, we report that omentin levels fluctuate in various diseases. In addition, we have focused on the pleiotropic roles of omentin in pulmonary diseases, as it may act as a biomarker for malignant pleural mesothelioma (MPM) and is related to disease severity. Omentin may play significant roles in other pulmonary diseases, such as asthma, obstructive sleep apnea syndrome (OSAS), pulmonary arterial hypertension (PAH), acute respiratory distress syndrome (ARDS), and chronic obstructive pulmonary disease (COPD). This review summarizes the advances in current knowledge and future trends, which may provide a concise and general view on omentin and its effects on pulmonary biology.

Metabolic syndrome, inflammation and atherothrombosis

Extensive research of the past decades altered our traditional concept about the genesis of atherosclerosis fundamentally. Today, the crucial role of inflammation in the formation and progression of atherosclerotic plaques is indisputable. Patients at high risk for developing cardiovascular disease, owing to poor diet, obesity and low physical activity have been shown to exhibit a particular inflammatory pattern.

Therefore, the present review highlights the crosslink between the metabolic syndrome (MetS), adipose tissue, adipokines and selected inflammatory cytokines in the context of atherothrombosis and cardiovascular disease.

Role of Perivascular Adipose Tissue in Health and Disease

Perivascular adipose tissue (PVAT) is cushion of fat tissue surrounding blood vessels, which is phenotypically different from other adipose tissue depots. PVAT is composed of adipocytes and stromal vascular fraction, constituted by different populations of immune cells, endothelial cells, and adipose-derived stromal cells. It expresses and releases an important number of vasoactive factors with paracrine effects on vascular structure and function. In healthy individuals, these factors elicit a net anticontractile and anti-inflammatory paracrine effect aimed at meeting hemodynamic and metabolic demands of specific organs and regions of the body. Pathophysiological situations, such as obesity, diabetes or hypertension, induce changes in its amount and in the expression pattern of vasoactive factors leading to a PVAT dysfunction in which the beneficial paracrine influence of PVAT is shifted to a pro-oxidant, proinflammatory, contractile, and trophic environment leading to functional and structural cardiovascular alterations and cardiovascular disease. Many different PVATs surrounding a variety of blood vessels have been described and exhibit regional differences. Both protective and deleterious influence of PVAT differs regionally depending on the specific vascular bed contributing to variations in the susceptibility of arteries and veins to vascular disease. PVAT therefore, might represent a novel target for pharmacological intervention in cardiovascular disease. © 2018 American Physiological Society. Compr Physiol 8:23-59, 2018.

Omentin-1 effects on mesenchymal stem cells: proliferation, apoptosis, and angiogenesis in vitro

Background

Mesenchymal stem cells (MSCs) are emerging as an extremely promising therapeutic agent for tissue repair. However, limitations exist such as the low numbers of MSCs obtained from donors, and the poor survival and function of donor cells. Omentin-1, a new fat depot-specific secretory adipokine, exerts proproliferation, prosurvival, and proangiogenic functions in certain cells via an Akt-dependent mechanism; however, little is known about the influence of omentin-1 on MSCs.

Methods

MSCs were isolated from 60–80 g donor rats. Cell proliferation was assessed with CCK-8 and EdU assay. Cell cycle, apoptosis ratio, reactive oxygen species concentration, and mitochondrial membrane potential were detected by flow cytometry. Hoechst 33342 dye was used to assess morphological changes of apoptosis. Expression levels of Akt, FoxO3a, GSK-3β, and apoptosis- and cell cycle-associated proteins were detected by Western blotting. Tube formation assay was used to test the angiogenesis role of conditioned medium from MSCs in vitro. The cytokine secretion was assessed by ELISA.

Results

After treatment with omentin-1 (100–800 ng/ml), MSCs displayed a higher proliferative capacity with an increasing number of cells in the S and G2 phase of the cell cycle. Moreover, omentin-1 preconditioning for 1 h could protect MSCs against H₂O₂-induced apoptosis in a concentration-dependent manner. Furthermore, omentin-1 pretreatment reduced the excessive reactive oxygen species. Western blots revealed that increased Bcl-2 and decreased Bax appeared in MSCs after omentin-1 incubation, which inhibited the mitochondrial apoptosis pathways with evidence showing inhibition of caspase-3 cleavage and preservation of mitochondrial membrane potential. Omentin-1 could enhance angiogenic growth factor secretion and elevate the ability of MSCs to stimulate tube formation by human umbilical vein endothelial cells (HUVECs). Furthermore, omentin-1 enhanced Akt phosphorylation; however, blockade of the PI3K/Akt pathway with an inhibitor, LY294002 (20 μM), suppressed the above beneficial effects of omentin-1.

Conclusion

Omentin-1 can exert beneficial effects on MSCs by promoting proliferation, inhibiting apoptosis, increasing secretion of angiogenic cytokines, and enhancing the ability for stimulating tube formation by HUVECs via the PI3K/Akt signaling pathway. Thus, omentin-1 may be considered a candidate for optimizing MSC-based cell therapy.

Adipose Tissue-Derived Omentin-1 Function and Regulation

Omentin-1, also known as intelectin-1, is a recently identified novel adipocytokine of 313 amino acids, which is expressed in visceral (omental and epicardial) fat as well as mesothelial cells, vascular cells, airway goblet cells, small intestine, colon, ovary, and plasma. The level of omentin-1 expression in (pre)adipocytes is decreased by glucose/insulin and stimulated by fibroblast growth factor-21 and dexamethasone. Several lines of experimental evidence have shown that omentin-1 plays crucial roles in the maintenance of body metabolism and insulin sensitivity, and has anti-inflammatory, anti-atherosclerotic, and cardiovascular protective effects via AMP-activated protein kinase/Akt/nuclear factor-κB/mitogen-activated protein kinase (ERK, JNK, and p38) signaling. Clinical studies have indicated the usage of circulating omentin-1 as a biomarker of obesity, metabolic disorders including insulin resistance, diabetes, and metabolic syndrome, and atherosclerotic cardiovascular diseases. It is also possible to use circulating omentin-1 as a biomarker of bone metabolism, inflammatory diseases, cancers, sleep apnea syndrome, preeclampsia, and polycystic ovary syndrome. Decreased omentin-1 levels are generally associated with these diseases. However, omentin-1 increases to counteract the acute phase after onset of these diseases. These findings indicate that omentin-1 may be a negative risk factor for these diseases, and also act as an acute-phase reactant by its anti-inflammatory and atheroprotective effects. Therapeutic strategies to restore omentin-1 levels may be valuable for the prevention or treatment of these diseases. Weight loss, olive oil-rich diet, aerobic training, and treatment with atorvastatin and antidiabetic drugs (metformin, pioglitazone, and exenatide) are effective means of increasing circulating omentin-1 levels. This review provides insights into the potential use of omentin-1 as a biomarker and therapeutic target for these diseases. © 2017 American Physiological Society. Compr Physiol 7:765-781, 2017.

MicroRNA-32 promotes calcification in vascular smooth muscle cells: Implications as a novel marker for coronary artery calcification

Cardiovascular calcification is one of the most severe outcomes associated with cardiovascular disease and often results in significant morbidity and mortality. Previous reports indicated that epigenomic regulation of microRNAs (miRNAs) might play important roles in vascular smooth muscle cell (VSMC) calcification. Here, we identified potential key miRNAs involved in vascular calcification in vivo and investigated the role of miR-32-5p (miR-32). According to microarray analysis, we observed increased expression of miR-125b, miR-30a, and miR-32 and decreased expression of miR-29a, miR-210, and miR-320 during the progression of vascularcalcification. Additionally, gain- and loss-of-function studies of miR-32 confirmed promotion of VSMC calcification in mice through the enhanced expression of bonemorphogenetic protein-2, runt-related transcription factor-2(RUNX2), osteopontin, and the bone-specific phosphoprotein matrix GLA protein in vitro. Moreover, miR-32 modulated vascularcalcification progression by activating phosphoinositide 3-kinase (PI3K)signaling and increasing RUNX2 expression and phosphorylation by targeting the 3'-untranslated region of phosphatase and tensin homolog Mrna (PTEN) in mouse VSMCs. Furthermore, we detected higher miR-32 levels in plasmafrom patients with coronary artery disease with coronary artery calcification (CAC) as compared with levels observed in non-CAC patients (P = 0.016), further confirming miR-32 as a critical modulator and potential diagnostic marker for CAC.

Adipokines: Potential Therapeutic Targets for Vascular Dysfunction in Type II Diabetes Mellitus and Obesity

Adipokines are bioactive molecules that regulate several physiological functions such as energy balance, insulin sensitization, appetite regulation, inflammatory response, and vascular homeostasis. They include proinflammatory cytokines such as adipocyte fatty acid binding protein (A-FABP) and anti-inflammatory cytokines such as adiponectin, as well as vasodilator and vasoconstrictor molecules. In obesity and type II diabetes mellitus (DM), insulin resistance causes impairment of the endocrine function of the perivascular adipose tissue, an imbalance in the secretion of vasoconstrictor and vasodilator molecules, and an increased production of reactive oxygen species. Recent studies have shown that targeting plasma levels of adipokines or the expression of their receptors can increase insulin sensitivity, improve vascular function, and reduce the risk of cardiovascular morbidity and mortality. Several reviews have discussed the potential of adipokines as therapeutic targets for type II DM and obesity; however, this review is the first to focus on their therapeutic potential for vascular dysfunction in type II DM and obesity.

Molecular Mechanisms of Obesity-Induced Osteoporosis and Muscle Atrophy

Obesity and osteoporosis are two alarming health disorders prominent among middle and old age populations, and the numbers of those affected by these two disorders are increasing. It is estimated that more than 600 million adults are obese and over 200 million people have osteoporosis worldwide. Interestingly, both of these abnormalities share some common features including a genetic predisposition, and a common origin: bone marrow mesenchymal stromal cells. Obesity is characterized by the expression of leptin, adiponectin, interleukin 6 (IL-6), interleukin 10 (IL-10), monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor-alpha (TNF-α), macrophage colony stimulating factor (M-CSF), growth hormone (GH), parathyroid hormone (PTH), angiotensin II (Ang II), 5-hydroxy-tryptamine (5-HT), Advance glycation end products (AGE), and myostatin, which exert their effects by modulating the signaling pathways within bone and muscle. Chemical messengers (e.g., TNF-α, IL-6, AGE, leptins) that are upregulated or downregulated as a result of obesity have been shown to act as negative regulators of osteoblasts, osteocytes and muscles, as well as positive regulators of osteoclasts. These additive effects of obesity ultimately increase the risk for osteoporosis and muscle atrophy. The aim of this review is to identify the potential cellular mechanisms through which obesity may facilitate osteoporosis, muscle atrophy and bone fractures.

Omentin protects against LPS-induced ARDS through suppressing pulmonary inflammation and promoting endothelial barrier via an Akt/eNOS-dependent mechanism

Acute respiratory distress syndrome (ARDS) is characterized by increased pulmonary inflammation and endothelial barrier permeability. Omentin has been shown to benefit obesity-related systemic vascular diseases; however, its effects on ARDS are unknown. In the present study, the level of circulating omentin in patients with ARDS was assessed to appraise its clinical significance in ARDS. Mice were subjected to systemic administration of adenoviral vector expressing omentin (Ad-omentin) and one-shot treatment of recombinant human omentin (rh-omentin) to examine omentin's effects on lipopolysaccharide (LPS)-induced ARDS. Pulmonary endothelial cells (ECs) were treated with rh-omentin to further investigate its underlying mechanism. We found that a decreased level of circulating omentin negatively correlated with white blood cells and procalcitonin in patients with ARDS. Ad-omentin protected against LPS-induced ARDS by alleviating the pulmonary inflammatory response and endothelial barrier injury in mice, accompanied by Akt/eNOS pathway activation. Treatment of pulmonary ECs with rh-omentin attenuated inflammatory response and restored adherens junctions (AJs), and cytoskeleton organization promoted endothelial barrier after LPS insult. Moreover, the omentin-mediated enhancement of EC survival and differentiation was blocked by the Akt/eNOS pathway inactivation. Therapeutic rh-omentin treatment also effectively protected against LPS-induced ARDS via the Akt/eNOS pathway. Collectively, these data indicated that omentin protects against LPS-induced ARDS by suppressing inflammation and promoting the pulmonary endothelial barrier, at least partially, through an Akt/eNOS-dependent mechanism. Therapeutic strategies aiming to restore omentin levels may be valuable for the prevention or treatment of ARDS.

Adipokines in psoriasis: An important link between skin inflammation and metabolic alterations

Psoriasis is a chronic inflammatory skin disease most common in Europe, North America, and Australia. The etiology and pathomechanisms underlying the evolution and persistence of the skin alterations are increasingly being understood and have led to the development of effective anti-psoriatic therapies. Apart from the skin manifestations, psoriasis is associated with the metabolic syndrome (MetS), known to increase the risk of type 2 diabetes mellitus and cardiovascular disorders. Research of the last years demonstrated a dysregulated adipokine balance as an important link between inflammation, MetS, and consequential disorders. This article describes selected adipokines and their potential role in both metabolic comorbidity and skin inflammation in psoriasis.

Relationships between serum Omentin-1 levels and bone mineral density in older men with osteoporosis

OBJECTIVE

To investigate the correlation between serum Omentin-1 levels and the presence of osteoporosis in older men.

METHODS

Serum Omentin-1, bone turnover biochemical markers, and bone mineral density (BMD) were determined in 45 older men with osteoporosis or 45 older men without osteoporosis (65-70 years old).

RESULTS

Omentin-1 levels were increased in older men with osteoporosis, and the differences remained significant after controlling for fat mass. Omentin-1 was negatively correlated with BMD. In a multiple linear stepwise regression analysis, Omentin-1, lean mass, but not fat mass, were independent predictors of BMD for the combined group. Significant negative correlations between Omentin-1 and bone-specific alkaline phosphatase (BAP) and bone cross-linked N-telopeptides of type Ⅰ collagen (NTX) were found. Omentin-1 was also independently associated with BMD and bone turnover markers in older men with osteoporosis and control groups that were considered separately.

CONCLUSIONS

Omentin-1 is an independent predictor of BMD in older men with osteoporosis, and it is negatively correlated with bone turnover biochemical markers. It is suggested that Omentin-1 may exert a negative effect on bone mass through the regulation of the osteoblast differentiation in the older men with osteoporosis.

Counteractive effects of omentin-1 against atherogenesis†

AIMS

Omentin-1, a novel adipocytokine expressed in visceral fat tissue, is negatively correlated with obesity, insulin resistance, and stable coronary artery disease (CAD). However, there have been no previous reports regarding the effects of omentin-1 on atherogenesis.

METHODS AND RESULTS

This study was performed to evaluate the atheroprotective effects of omentin-1 on human monocyte-derived macrophages, human aortic smooth muscle cells (HASMCs) in vitro, and aortic lesions in Apoe(-/-) mice in vivo. The histological expression of omentin-1 in coronary artery lesions and epicardial adipose tissues and its plasma levels were compared between CAD and non-CAD patients. Omentin-1 was abundantly expressed in human umbilical vein endothelial cells, macrophages, HASMCs, and human coronary artery SMCs in vitro. Omentin-1 promoted anti-inflammatory M2 phenotype during differentiation of human monocytes into macrophages. Omentin-1 suppressed oxidized low-density lipoprotein-induced foam cell formation associated with down-regulation of CD36, scavenger receptor class A, and acyl-CoA:cholesterol acyltransferase-1 and up-regulation of neutral cholesterol ester hydrolase in human macrophages. Omentin-1 suppressed angiotensin II-induced migration and platelet-derived growth factor-BB-induced proliferation, and collagen-1 and -3 expression in HASMCs. Four-week infusion of omentin-1 into Apoe(-/-) mice retarded the development of aortic atherosclerotic lesions with reduced contents of monocytes/macrophages, SMCs, and collagen fibres along with peritoneal M2-activated macrophages with inflammasome down-regulation and lowered plasma total cholesterol levels. Omentin-1 levels were markedly reduced in coronary endothelium and epicardial fat but increased in plasma and atheromatous plaques (macrophages/SMCs) in CAD patients compared with non-CAD patients.

CONCLUSION

This study provided the first evidence that omentin-1 may serve as a novel therapeutic target for atherosclerosis and CAD.

[Omentin: Role in insulin resistance, inflammation and cardiovascular protection]

The omentin is an adipokine, which role is due to the capacity of regulate metabolic (insulin sensitivity) and anti-inflammatory activities, thus conferring vascular protection during obesity and diabetes mellitus type 2. By this, it is important to know the mechanisms by which omentin confers cardiovascular protection, with the purpose of establish omentin a possible therapeutic target or molecule on this scenario.

Omentin-1 plasma levels and cholesterol metabolism in obese patients with diabetes mellitus type 1: impact of weight reduction

Background:

Omentin-1 is an anti-inflammatory adipokine produced preferentially by visceral adipose tissue. Plasma levels of omentin-1 are decreased in obesity and other insulin-resistant states. Insulin resistance contributes to the changes of cholesterol synthesis and absorption as well. The aim of this study was to characterise omentin-1 plasma levels in obese patients with diabetes mellitus type 1 during weight reduction, and to elucidate the relationship between cholesterol metabolism and omentin-1.

Methods:

Plasma levels of omentin-1 were measured in obese type 1 diabetics (n=14, body mass index >30 kg m⁻², age 29–62 years) by enzyme-linked immunosorbent assay (BioVendor). Gas chromatography with flame ionisation detector (Fisons Plc.,) was used to measure squalene and non-cholesterol sterols—markers of cholesterol synthesis and absorption (phase I). Measurements were repeated after 1 month (phase II; 1 week of fasting in the hospital setting and 3 weeks on a diet containing 150 g saccharides per day) and after 1 year (phase III) on a diet with 225 g saccharides per day.

Results:

Omentin-1 plasma levels were stable during phases I and II, but significantly increased (P<0.001) during phase III. Omentin-1 plasma dynamics were significantly associated with plasma levels of high-density lipoprotein (P=0.005) and triacylglycerols (P=0.01), as well as with lathosterol (P=0.03).

Conclusion:

Omentin-1 plasma levels significantly increased during the weight reduction programme. Omentin-1 plasma dynamics suggest a close relationship with cholesterol metabolism.

The protective functions of omentin in cardiovascular diseases

Adipose tissue is considered as a large gland that can produce paracrine and endocrine hormones. Growing evidence suggests that adipocytes may link obesity to cardiovascular diseases (CVD). Adipose tissue produces a large number of mediators, which affect metabolism, inflammation and coagulation. Omentin, a novel adipocytokine, has come into the center of interest due to its favorable effects on inflammation, glucose homeostasis and CVD. The present review provides a concise and general overview on the roles of omentin in CVD. The knowledge of these concepts may provide a new strategy to reduce disease risks on CVD in the future.

The protective effect of GLP-1 analogue in arterial calcification through attenuating osteoblastic differentiation of human VSMCs

BACKGROUND

Arterial calcification is a common event in cardiovascular pathogenesis. Osteoblastic differentiation of vascular smooth muscle cells (VSMCs) is the most important cytopathologic foundation of arterial calcification. Glucagon-like peptide-1 (GLP-1) exerts multiple cardioprotective actions beyond insulinotropic effects through GLP-1 receptor (GLP-1R). However, whether GLP-1 regulates osteoblastic differentiation of VSMCs and associated molecular mechanisms has not been clarified.

METHODS

The human VSMC differentiation model was established by beta-glycerophosphate (β-GP) induction. The mineralization was measured by Alizarin Red S staining. Protein expression and phosphorylation were detected by Western blot or immunofluorescence. GLP-1R gene expression was silenced by siRNA.

RESULTS

The GLP-1 analogue liraglutide dose- and time-dependently inhibited the protein expression of osteoblastic differentiation markers alkaline phosphatase (ALP), osteocalcin (OC), and Runt-related transcription factor 2 (Runx2), phosphorylation of PI3K, Akt, mTOR, and S6K1. Silencing of GLP-1R gene expression by siRNA significantly blocked the effects of liraglutide in ALP protein expression and PI3K/Akt phosphorylation.

CONCLUSION

GLP-1 analogue liraglutide attenuates the osteoblastic differentiation and calcification of human VSMCs through its receptor and subsequent activation of PI3K/Akt/mTOR/S6K1 signaling. GLP-1 analogues may be potential agents for the treatment of cardiovascular diseases.

Adipokines, vascular wall, and cardiovascular disease: a focused overview of the role of adipokines in the pathophysiology of cardiovascular disease

Epidemiological evidence has shown that abdominal obesity is closely associated with the development of cardiovascular (CV) disease, suggesting that it might be considered as an independent CV risk factor. However, the pathophysiological mechanisms responsible for the association between these 2 clinical entities remain largely unknown. Adipocytes are considered able to produce and secrete chemical mediators known as "adipokines" that may exert several biological actions, including those on heart and vessels. Of interest, a different adipokine profile can be observed in the plasma of patients with obesity or metabolic syndrome compared with healthy controls. We consider the main adipokines, focusing on their effects on the vascular wall and analyzing their role in CV pathophysiology.

Omentin-1 promotes the growth of neural stem cells via activation of Akt signaling

Omentin is a novel adipokine, which is expressed in and released from omental adipose tissue. In the present study, the effect of omentin on neural stem cells (NSCs) was investigated. NSCs are a subtype of stem cell in the nervous system, which are able to self‑renew and generate neurons and glia for repairing neural lesions. Mouse NSCs were isolated and cultured in vitro. Treatment with recombinant omentin for 3 and 5 days significantly increased the size of NSC neurospheres (P<0.01) and enhanced NSC cell viability in normal conditions. In addition, omentin protected against the decrease in cell viability induced by the pro‑inflammatory cytokine tumor necrosis factor‑α. In the NSCs, incubation of omentin for 2, 4, 6, 8 and 16 h enhanced the phosphorylation of Akt at the Thr308 site and of AS160 at the Ser318 site, peaking 6 h after treatment. Additionally, treatment with LY294002 (10 µM), a specific inhibitor of phosphatidylinositol 3‑kinase/Akt signaling, eliminated the omentin‑induced increase in neurosphere size and cell viability. Overall, the present study provided the first evidence, to the best of our knowledge, that omentin promotes the growth and survival of NSCs in vitro through activation of the Akt signaling pathway. These results may contribute to the understanding of the role of omentin in the nervous system.

Puerarin attenuates calcification of vascular smooth muscle cells

Several studies demonstrate that estradiol can prevent arterial calcification. However, little is known regarding the effect of puerarin, a phytoestrogen extracted from Radix Puerariae, on arterial calcification. The aim of the present study was to determine whether puerarin reduced osteoblastic differentiation of calcifying vascular smooth muscle cells (CVSMCs). The CVSMCs were isolated from mice aorta and treated with different concentrations of puerarin. The alkaline phosphatase (ALP) activity, osteocalcin secretion and Runx2 expression were determined. To examine whether estrogen receptors (ERs) PI3K and Akt play a role in this effect, ICI182789, phosphoinositide 3-kinase (PI3K) inhibitor, LY294002, or the Akt inhibitor, 1L-6-hydroxymethyl-chiro-inositol 2-(R)-2-O-methyl-3-O-octadecylcarbonate (HIMO) was used. Our results showed puerarin could inhibit ALP activity, osteocalcin secretion and Runx2 expression in CVSMCs. Puerarin could induce the activation of Akt. Furthermore, pretreatment of ICI182780, LY294002, HIMO could abolish the effect of puerarin on ALP activity in CVSMCs. Our experiment demonstrated that puerain could attenuate the osteoblastic differentiation of VSMCs through the ER/PI3K-Akt signal pathway.

Relationships between serum omentin-1, body fat mass and bone mineral density in healthy Chinese male adults in Changsha area

PURPOSE

The present study is firstly designed to identify the relationship between serum omentin-1 concentration, body fat mass and bone mineral density in healthy Chinese male adults in Changsha city.

METHODS

A total of 219 (20-80 years old) healthy subjects were enrolled in this cross-sectional study. Serum omentin-1, adiponectin, leptin, resistin and bone turn over biochemical markers were measured with enzyme-linked immunosorbent assay. Bone mineral density (BMD) and fat body composition were determined using dual-energy-X-ray absorptiometry.

RESULTS

Serum omentin-1 levels in the overweight subjects were significantly lower than those of the subjects with normal weight (p < 0.05). Omentin-1 was negatively correlated with weight (r = -0.418), body mass index (BMI, r = -0.419), waist circumference (r = -0.402), waist-to-hip ratio (WHR, r = -0.355), fat body mass (FBM, r = -0.430), fat % (r = -0.408), trunk fat (-0.431). However, after controlling for age, BMI and FBM, no significant correlation was noticed between omentin-1 and BMD at different skeletal sites. Pearson's correlation coefficients and partial correlation coefficients after adjustment showed no significant correlations between omentin-1 and bone turn over biochemical markers, including bone-specific alkaline phosphatase and bone cross-linked N-terminal telopeptides of type I collagen. Multiple line stepwise regression analysis revealed that FBM, WHR, adiponectin were important variables affecting omentin-1. Moreover, lean tissue mass was the most important factor affecting BMD and explained 10.5-14.7 % of the variance. Omentin-1, leptin and resistin were not the predictors of BMD.

CONCLUSIONS

Serum omentin-1 was negatively correlated with FBM and BMI in healthy Chinese male adults, It was not significantly correlated with bone turnover biochemical markers. Omentin-1 may exert ambiguous effects on BMD, which maybe caused by the complex interactions among adipokines, hormonal activity, and body composition and bone metabolism.

Plasma levels of omentin-1 and visfatin in senile patients with coronary heart disease and heart failure

OBJECTIVE

To investigate the alteration of plasma levels of omentin-1 and visfatin in elderly patients with coronary heart disease (CHD) and heart failure.

METHODS

Plasma omentin-1 and visfatin levels were measured in 90 subjects (29 stable angina pectoris (SAP) cases, 30 unstable angina pectoris (UAP) cases and 31 age- and sex-matched healthy controls (age ≥ 60 years) by enzyme-linked immunosorbent assay methods. According to the New York Heart Association classification, 59 CHDs were divided into three groups: functional I class, 11 cases; functional II/III class, 36 cases; and functional IV class, 12 cases.

RESULTS

The plasma level of omentin-1 in CHD patients was significantly lower than that of the control group. Omentin-1in SAP group and UAP group were significantly lower compared to the control group (there was no statistical significance between UAP group and SAP group; P >0.05). The plasma level of visfatin in CHD patients was significantly higher than that of the control group. Similarly, visfatin in SAP group and UAP group were all significantly higher compared to the control group, while there was no statistical significance between UAP group, and SAP group. The plasma omentin-1 level was negatively correlated with SBP (r=-0.264, P<0.05), positively correlated with HDL-c level (r=0.271, P<0.05); the plasma visfatin level was positively correlated with TC (r=0.292,P<0.05), negatively correlated with HDL-c level (r=-0.266,P<0.05). There was a negative correlation between plasma omentin-1 and visfatin levels (r=-0.280, P<0.05). Moreover, multiple linear stepwise regression analysis showed that omentin-1 and visfatin levels might be affected by HDL-c level. Logistic regression analysis showed that visfatin could be an independent risk factor of CHD.

CONCLUSIONS

Decreased levels of omentin-1 and increased levels of visfatin may be involved in the occurrence and development of CHD. Omentin-1 and visfatin, independently, may be protective and pro-inflammatory cytokines. Additionally, both omentin-1 and visfatin may be related to lipid metabolism. Visfatin may be an independent risk factor of CHD.

Adipokines as a novel link between obesity and atherosclerosis

The traditional perception of adipose tissue as a storage organ of fatty acids has been replaced by the notion that adipose tissue is an active endocrine organ, releasing various adipokines that are involved in the pathogenesis of obesity-related metabolic disturbances. Obesity is a well-known risk factor for atherosclerosis, and accelerates atherosclerosis by many mechanisms such as increase in blood pressure and glucose level, abnormal lipid profiles, and systemic inflammation. Furthermore, growing evidence suggests that some adipokines directly mediate the process of atherosclerosis by influencing the function of endothelial cells, arterial smooth muscle cells, and macrophages in vessel walls. In obese patients, the secretion and coordination of such adipokines is abnormal, and the secretion of specific adipokines increases or decreases. Accordingly, the discovery of new adipokines and elucidation of their functions might lead to a new treatment strategy for metabolic disorders related to obesity, including cardiovascular diseases.

Overexpression of C1q/Tumor Necrosis Factor–Related Protein-3 Promotes Phosphate-Induced Vascular Smooth Muscle Cell Calcification Both In Vivo and In Vitro

Objective—

Vascular calcification is highly correlated with increased cardiovascular morbidity and mortality. C1q/tumor necrosis factor–related protein-3 (CTRP3) is a newly identified adipokine that plays important roles in cardiovascular system. Here, we investigated the role of CTRP3 in vascular calcification and its underlying mechanism.

Approach and Results—

Adenine-induced chronic renal failure rat model was used to mimic the process of arterial medial calcification. The level of CTRP3 was elevated in serum and abdominal aorta of chronic renal failure rats. Periadventitial gene delivery of CTRP3 significantly accelerated the calcification of abdominal aorta and arterial ring. In cultured vascular smooth muscle cells (VSMCs), CTRP3 increased β-glycerophosphate–induced calcium deposition and alkaline phosphatase activity. Although CTRP3 alone was not sufficient to induce calcification in VSMCs, it upregulated the expression of osteogenic marker genes including runt-related transcription factor 2 ( Runx2 ), bone morphogenetic protein 2, and osteopontin. CTRP3 further enhanced β-glycerophosphate–induced downregulation of smooth muscle α-actin and smooth muscle 22α, while augmenting osteogenic marker expression in VSMCs induced by β-glycerophosphate. In contrast, knockdown of CTRP3 in VSMCs potently suppressed β-glycerophosphate–induced calcification. Mechanistically, knockdown of Runx2 inhibited CTRP3-promoted VSMC calcification. CTRP3 increased extracellular signal–regulated kinase 1/2 phosphorylation and reactive oxygen species production. Preincubation with U0126, an extracellular signal–regulated kinase 1/2 upstream kinase inhibitor, had no effect on CTRP3-induced reactive oxygen species production. However, pretreatment with N-acetyl- l -cysteine, a reactive oxygen species scavenger, suppressed CTRP3-induced extracellular signal–regulated kinase 1/2 phosphorylation. Both N-acetyl- l -cysteine and U0126 significantly inhibited CTRP3-induced upregulation of Runx2 and calcified nodule formation.

Conclusions—

CTRP3 promotes vascular calcification by enhancing phosphate-induced osteogenic transition of VSMC through reactive oxygen species–extracellular signal–regulated kinase 1/2–Runx2 pathway.

Implication of circulating omentin-1 level on the arterial stiffening in type 2 diabetes mellitus

Omentin-1 is an adipokine implicated in diabetes, inflammation, and cardiovascular disease. However, no prospective studies have examined the impact of circulating omentin-1 levels on arterial stiffening in patients with type 2 diabetes mellitus. For the purpose of this study, we recruited 120 patients with type 2 diabetes mellitus and measured serum omentin-1, adiponectin, and high-sensitivity C-reactive protein levels as well as other cardiovascular risk factors. Arterial stiffness was assessed by brachial ankle pulse wave velocity (baPWV). An increase in the level of circulating omentin-1 over a period of 1 year was positively correlated with changes in levels of HbA1c and serum adiponectin as well as baPWV. Subjects with higher baseline serum omentin-1 levels tended to have a reduced arterial stiffness after 1 year (P for linear trend = 0.03). In the group with increased baPWV after 1 year, the magnitude of increase of circulating omentin-1 levels was significantly higher than in the group with a lower baPWV after 1 year (134.3 [16.6, 277.1] ng/mL vs. 15.9 [-67.6, 145.7] ng/mL, P < 0.01). Multiple stepwise logistic regression analysis revealed that an increase in systolic blood pressure and an increase in serum omentin-1 level were independently correlated with arterial stiffening, even after adjusting for other cardiovascular risk factors and medication history. Baseline serum omentin-1 levels can predict arterial stiffness changes occurring within a year. Furthermore, changes in serum omentin-1 levels after a year can function as independent markers of arterial stiffening in patients with type 2 diabetes mellitus.

Adipocytokines in relation to cardiovascular disease

Adipose tissue can be considered as a huge gland producing paracrine and endocrine hormones, the adipo(cyto)kines. There is growing evidence that these adipo(cyto)kines may link obesity to cardiovascular diseases. The excessive adipocyte hypertrophy in obesity induces hypoxia in adipose tissue. This leads to adiposopathy, the process that converts "healthy" adipose tissue to "sick" adipose tissue. This is accompanied by a change in profile of adipo(cyto)kines released, with less production of the "healthy" adipo(cyto)kines such as adiponectin and omentin and more release of the "unhealthy" adipo(cyto)kines, ultimately leading to the development of cardiovascular diseases. The present review provides a concise and general overview of the actual concepts of the role of adipo(cyto)kines in endothelial dysfunction, hypertension, atherosclerosis and heart diseases. The knowledge of these concepts may lead to new tools to improve health in the next generations.

Connective tissue growth factor induces osteogenic differentiation of vascular smooth muscle cells through ERK signaling

Connective tissue growth factor (CTGF) plays an important role in the pathogenesis of atherosclerosis by promoting vascular smooth muscle cell (VSMC) growth, migration, apoptosis, adhesion and the secretion of matrix components. The osteogenic differentiation of VSMCs is essential in the development of vascular calcification. However, the role of CTGF in the transdifferentiation and calcification of VSMCs is unclear. In the present study, we examined whether CTGF stimulates VSMC transdifferentiation. Primary VSMCs were obtained from mouse thoracic aortas by enzymatic digestion and identified by immunostaining for smooth muscle specific α-actin antibody (α-SMA). VSMC calcification was induced by the addition of CTGF to the osteogenic mediaum containing 5-10% FBS in the presence of 0.25 mM ascorbic acid and 10 mM β-glycerophosphate for 14 days. Calcified cells were determined by Alizarin Red S staining. Our results revealed that CTGF induced the expression of several bone markers, including alkaline phosphatase (ALP), osteocalcin (OC), osteoprotegerin (OPG) and core-binding factor subunit α1 (Cbfα1)/runt-related transcription factor 2 (Runx2), as well as calcification. However, the inhibition of extracellular signal-regulated kinase (ERK) activity using the ERK-specific inhibitor, PD98059, blocked the induction of these proteins and VSMC calcification. Based on these data, we conclude that CTGF stimulates the transdifferentiation of VSMCs into osteoblasts and that the ERK signaling pathway appears to play a critical role in this process.

Cardioprotective properties of omentin-1 in type 2 diabetes: evidence from clinical and in vitro studies

Context

Adipokines are linked to the development of cardiovascular dysfunction in type 2 diabetes (DM2). In DM2-patients, circulating levels of omentin-1, an adipokine preferentially expressed in epicardial adipose tissue, are decreased. This study investigated whether omentin-1 has a cardioprotective function.

Methods

Omentin-1 levels in plasma and cardiac fat depots were determined in DM2-patients versus controls. Moreover, the relation between omentin-1 levels and cardiac function was examined in men with uncomplicated DM2. Finally, we determined whether omentin-1 could reverse the induction of cardiomyocyte dysfunction by conditioned media derived from epicardial adipose tissue from patients with DM2.

Results

Omentin-1 was highly expressed and secreted by epicardial adipose tissue, and reduced in DM2. Circulating omentin-1 levels were lower in DM2 versus controls, and positively correlated with the diastolic parameters early peak filling rate, early deceleration peak and early deceleration mean (all P<0.05). The improved diastolic function following pioglitazone treatment associated with increases in omentin-1 levels (P<0.05). In vitro, exposure of cardiomyocytes to conditioned media derived from epicardial adipose tissue from patients with DM2 induced contractile dysfunction and insulin resistance, which was prevented by the addition of recombinant omentin.

Conclusion

These data identify omentin-1 as a cardioprotective adipokine, and indicate that decreases in omentin-1 levels could contribute to the induction of cardiovascular dysfunction in DM2.

Relationship between serum omentin-1 level and bone mineral density in girls with anorexia nervosa

BACKGROUND

Adolescents with anorexia nervosa (AN) have low bone mineral density (BMD). Omentin- 1, the main circulating adipocytokine, plays an important role in bone metabolism in healthy individuals. However, their association with bone metabolism in AN is unknown.

METHODS

Serum omentin-1, bone turnover biochemical markers, and BMD were determined in 26 girls with AN and 24 healthy girls (15-18 years old).

RESULTS

Omentin-1 levels increased in AN subjects, and the differences became greater after controlling for fat mass. Omentin-1 was negatively correlated with BMD. In the multiple linear stepwise regression analysis, omentin-1, body mass index and lean mass, but not fat mass, were independent predictors of BMD for the combined group. Significant negative correlations were found between omentin-1 and bone-specific alkaline phosphatase, bone cross-linked N-telopeptides of type I collagen. Omentin-1 was also independently associated with BMD and bone turnover markers in the AN and control groups considered separately.

CONCLUSIONS

Omentin-1 was an independent predictor of BMD in adolescents with AN, and negatively correlated with bone turnover markers. This suggested that omentin-1 may exert a negative effect on bone mass by inhibiting bone formation in girls with AN.

Omentin-1 Stimulates Human Osteoblast Proliferation through PI3K/Akt Signal Pathway

It has been presumed that adipokines deriving from adipose tissue may play important roles in bone metabolism. Omentin-1, a novel adipokine, which is selectively expressed in visceral adipose tissue, has been reported to stimulate proliferation and inhibit differentiation of mouse osteoblast. However, little information refers to the effect of omentin-1 on human osteoblast (hOB) proliferation. The current study examined the potential effects of omentin-1 on proliferation in hOB and the signal pathway involved. Omentin-1 promoted hOB proliferation in a dose-dependent manner as determined by [(3)H]thymidine incorporation. Western blot analysis revealed that omentin-1 induced activation of Akt (phosphatidylinositol-3 kinase downstream effector) and such effect was impeded by transfection of hOB with Akt-siRNA. Furthermore, LY294002 (a selective PI3K inhibitor) and HIMO (a selective Akt inhibitor) abolished the omentin-1-induced hOB proliferation. These findings indicate that omentin-1 induces hOB proliferation via the PI3K/Akt signaling pathway and suggest that osteoblast is a direct target of omentin-1.