Visceral adipose tissue-derived serine proteinase inhibitor inhibits apoptosis of endothelial cells as a ligand for the cell-surface GRP78/voltage-dependent anion channel complex

Genetic Determination of Serum Levels of Diabetes-Associated Adipokines

Adipose tissue secretes an abundance of proteins. Some of these proteins are known as adipokines and adipose-derived hormones which have been linked with metabolic disorders, including type 2 diabetes, and even with cancer. Variance in serum adipokine concentration is often closely associated with an increase (obesity) or decrease (lipodystrophy) in fat tissue mass, and it is affected by age, gender, and localization of the adipose tissue. However, there may be genetic variants which, in consequence, influence the serum concentration of a certain adipokine, and thereby promote metabolic disturbances or, with regard to the "protective" allele, exert beneficial effects. This review focuses on the genetic determination of serum levels of the following adipokines: adiponectin, chemerin, leptin, progranulin, resistin, retinol binding protein 4, vaspin, adipsin, apelin, and omentin. The article reports on the latest findings from genome-wide association studies (GWAS) and candidate gene studies, showing variants located in/nearby the adipokine genes and other (non-receptor) genes. An extra chapter highlights adipokine-receptor variants. Epigenetic studies on adipokines are also addressed.

Vaspin attenuates the progression of atherosclerosis by inhibiting ER stress-induced macrophage apoptosis in apoE‑/‑ mice

Visceral adipose tissue-derived serine protease inhibitor (vaspin) is a novel adipokine with potential insulin-sensitizing properties, which was initially detected in the visceral adipose tissue of genetically obese rats. Previous studies have demonstrated that vaspin exerts a protective effect on arteries undergoing atherosclerosis in vitro, and it has been shown to exert anti-inflammatory and antimigratory effects on vascular smooth muscle cells. Vaspin promotes proliferation and inhibits apoptosis in endothelial cells, and decreases proliferation of the arterial intima under diabetic conditions. In addition, macrophage apoptosis is an important characteristic of atherosclerotic plaque development. In vivo experiments were performed by histological analysis, including Oil Red O, hematoxylin and eosin and Masson's trichrome staining. Mice were injected with lentivirus via the tail vein and tissues were obtained for histological analysis. Cell apoptosis was determined by flow cytometry of Annexin-V/propidium iodide dual staining and terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling assay. Total proteins were extracted and protein expression levels were detected by western blot analysis. The present study aimed to investigate whether vaspin was able to protect against atherosclerotic development in vivo, and to explore the underlying mechanisms of the potential antiatherogenic effects. The results of the current study indicated that vaspin inhibited the progression of atherosclerotic plaques in apoE(‑/‑) mice by inhibiting endoplasmic reticulum stress-induced macrophage apoptosis.

The role of vaspin in the development of metabolic and glucose tolerance disorders and atherosclerosis

In recent years, most research efforts have been focused on studying insulin-sensitizing adipokines. One of the most recently discovered adipokines is vaspin, a visceral adipose tissue-derived serine protease inhibitor. Vaspin levels have been found significantly increased in mice with obesity and insulin resistance. It has been assumed that vaspin serves as an insulin sensitizer with anti-inflammatory effects and might act as a compensatory mechanism in response to decreased insulin sensitivity. Most studies in humans have shown a positive correlation between vaspin gene expression and serum levels, and metabolic syndrome parameters. Vaspin gene expression is influenced by age and gender, and the administration of insulin sensitizers enhances it in mice, whereas the use of metformin decreases serum vaspin levels in humans, probably due to different regulatory mechanisms. Presumably vaspin plays local and endocrine role in the development of initial and advanced atherosclerosis in obese subjects and might be used as a predictor of coronary and cerebrovascular disease. It is believed that vaspin could be regarded as a new link between obesity and related metabolic disorders, including glucose intolerance. The entire understanding of vaspin intimate mechanism of action might enable the development of novel etiology-based treatment strategies, targeting metabolic and glucose tolerance disorders.

Serum vaspin levels: A possible correlation with digital ulcers in patients with systemic sclerosis

Vaspin is an adipokine implicated in vascular inflammation and remodeling. We herein evaluated the clinical correlation of serum vaspin levels in systemic sclerosis (SSc). Consistent with previous reports, 12% of subjects exhibited serum vaspin levels over 10 ng/mL, likely due to genetic effects. Excluding these subjects, despite no difference between SSc and control subjects, serum vaspin levels were significantly decreased in SSc patients with digital ulcers compared with those without, suggesting the potential contribution of vaspin to digital ulcers of this disease.

The unfolded protein response in retinal vascular diseases: implications and therapeutic potential beyond protein folding

Angiogenesis is a complex, step-wise process of new vessel formation that is involved in both normal embryonic development as well as postnatal pathological processes, such as cancer, cardiovascular disease, and diabetes. Aberrant blood vessel growth, also known as neovascularization, in the retina and the choroid is a major cause of vision loss in severe eye diseases, such as diabetic retinopathy, age-related macular degeneration, retinopathy of prematurity, and central and branch retinal vein occlusion. Yet, retinal neovascularization is causally and dynamically associated with vasodegeneration, ischemia, and vascular remodeling in retinal tissues. Understanding the mechanisms of retinal neovascularization is an urgent unmet need for developing new treatments for these devastating diseases. Accumulating evidence suggests a vital role for the unfolded protein response (UPR) in regulation of angiogenesis, in part through coordinating the secretion of pro-angiogenic growth factors, such as VEGF, and modulating endothelial cell survival and activity. Herein, we summarize current research in the context of endoplasmic reticulum (ER) stress and UPR signaling in retinal angiogenesis and vascular remodeling, highlighting potential implications of targeting these stress response pathways in the prevention and treatment of retinal vascular diseases that result in visual deficits and blindness.

Increased vaspin levels are associated with beneficial metabolic outcome pre- and post-bariatric surgery

Purpose

Vaspin (visceral-adipose-tissue-derived-serine-protease-inhibitor) is a recently identified adipokine with putative insulin-sensitizing properties. Plasma vaspin responses to surgery-induced weight loss are sparse and contradictory.

Design and Participants

We evaluated changes in vaspin levels and relationship to post-operative outcomes in men (n = 22) and women (n = 55) undergoing biliopancreatic-diversion/duodenal-switch bariatric surgery. Body composition and plasma parameters were measured at baseline, acutely (1 and 5 days) and medium-term (6 and 12 months) post-surgery.

Results

Fasting preoperative vaspin concentrations were comparable in men vs women. The distribution was biphasic (both men and women) with a nadir of 2.5 ng/ml. Subjects were divided into high (≥2.5 ng/mL, HI-group) and low (<2.5 ng/mL, LO-group) vaspin level. Both groups had comparable sex distribution, age and BMI, but the HI-vaspin group had lower insulin, HOMA, and triglyceride and higher HDL-cholesterol, acylation stimulating protein (ASP) and IL-6 levels (all p<0.05). Post-operatively, both groups decreased BMI comparably over 12 months; the HI-vaspin group maintained high vaspin levels, while the LO-vaspin group gradually increased their levels with weight loss over 12 months. The HI-vaspin group maintained a better glucose, insulin, HOMA, fructosamine, HDL-cholesterol, and triglyceride profile throughout. The HI-vaspin group also had higher gamma-glutamyltransferase and ASP profiles. Finally, baseline vaspin level inversely correlated significantly with baseline and 12-month insulin, HOMA, triglyceride and positively correlated with HDL and ASP. Twelve-month vaspin also correlated similarly, including an inverse correlation with BMI.

Conclusion

Globally, this study supports the concept of vaspin as a beneficial adipokine in obesity, which may potentially lead to possible therapeutic targets.

Voltage dependent anion channel is redistributed during Japanese encephalitis virus infection of insect cells

Despite the availability of an effective vaccine, Japanese encephalitis remains a significant cause of morbidity and mortality in many parts of Asia. Japanese encephalitis is caused by the Japanese encephalitis virus (JEV), a mosquito transmitted flavivirus. Many of the details of the virus replication cycle in mosquito cells remain unknown. This study sought to determine whether GRP78, a well-characterized flavivirus E protein interacting protein, interacted with JEV E protein in insect cells, and whether this interaction was mediated at the cell surface. GRP78 was shown to interact with JEV E protein by coimmunoprecipitation, and was additionally shown to interact with voltage dependent anion protein (VDAC) through the same methodology. Antibody inhibition experiments showed that neither GRP78 nor VDAC played a role in JEV internalization to insect cells. Interestingly, VDAC was shown to be significantly relocalized in response to JEV infection, and significant levels of colocalization between VDAC and GRP78 and VDAC and ribosomal L28 protein were seen in JEV infected but not uninfected cells. This is the first report of relocalization of VDAC in response to JEV infection and suggests that this may be a part of the JEV replication strategy in insect cells.

Vaspin (serpinA12) in obesity, insulin resistance, and inflammation

While genome-wide association studies as well as candidate gene studies have revealed a great deal of insight into the contribution of genetics to obesity development and susceptibility, advances in adipose tissue research have substantially changed the understanding of adipose tissue function. Its perception has changed from passive lipid storage tissue to active endocrine organ regulating and modulating whole-body energy homeostasis and metabolism and inflammatory and immune responses by secreting a multitude of bioactive molecules, termed adipokines. The expression of human vaspin (serpinA12) is positively correlated to body mass index and insulin sensitivity and increases glucose tolerance in vivo, suggesting a compensatory role in response to diminished insulin signaling in obesity. Recently, considerable insight has been gained into vaspin structure, function, and specific target tissue-dependent effects, and several lines of evidence suggest vaspin as a promising candidate for drug development for the treatment of obesity-related insulin resistance and inflammation. These will be summarized in this review with a focus on molecular mechanisms and pathways.

Vaspin inhibited proinflammatory cytokine induced activation of nuclear factor-kappa B and its downstream molecules in human endothelial EA.hy926 cells

AIMS

In this study, we investigated the effects of visceral adipose tissue-derived serpin (vaspin), a newly discovered adipocytokine, on nuclear factor-kappa B (NF-κB) and its downstream molecules in proinflammatory cytokines, tumor necrosis factor-α (TNF-α) and interleukine-1 (IL-1), stimulated human endothelial EA.hy926 cells to elucidate the role of vaspin in the inflammatory states of endothelium.

METHODS

A NF-κB luciferase reporter system was constructed and stably transfected into human endothelial cell line EA.hy926. Following transfection, EA.hy926 cells were pretreated with various concentrations of vaspin (0-320 ng/ml) before TNF-α and IL-1 stimulation. The transcription activity of NF-κB was determined using luciferase reporter assay. Expression levels of NF-κB downstream inflammatory cytokines, TNF-α, IL-1 and IL-6 were measured by enzyme-linked immunosorbent assay (ELISA). Expressions of adhesion molecules and chemokines, intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemotactic protein-1 (MCP-1) were determined by quantitative real-time PCR (RT-PCR) and western blot in mRNA and protein levels, respectively.

RESULTS

Results showed that vaspin inhibited TNF-α and IL-1 mediated activation of NF-κB and its downstream molecules in a concentration-dependent manner (P<0.05).

CONCLUSIONS

We conclude that vaspin protected endothelial cells from proinflammatory cytokines induced inflammation by inhibition of NF-κB and its downstream molecules.

Vaspin inhibits cytokine-induced nuclear factor-kappa B activation and adhesion molecule expression via AMP-activated protein kinase activation in vascular endothelial cells

Background

Vaspin is an adipocytokine that was recently identified in the visceral adipose tissue of diabetic rats and has anti-diabetic and anti-atherogenic effects. We hypothesized that vaspin prevents inflammatory cytokine-induced nuclear factor-kappa B (NF-κB) activation by activating AMP-activated protein kinase (AMPK) in vascular endothelial cells.

Methods

We examined the effects of vaspin on NF-κB activation and the expression of the NF-κB-mediated genes intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-selectin, and monocyte chemoattractant protein-1 (MCP-1). Human aortic endothelial cells (HAECS) were used. Tumor necrosis factor alpha (TNFα) was used as a representative proinflammatory cytokine.

Results

Treatment with vaspin significantly increased the phosphorylation of AMPK and acetyl-CoA carboxylase, the down-stream target of AMPK. Furthermore, treatment with vaspin significantly decreased TNFα-induced activation of NF-κB, as well as the expression of the adhesion molecules ICAM-1, VCAM-1, E-selectin, and MCP-1. These effects were abolished following transfection of AMPKα1-specific small interfering RNA. In an adhesion assay using THP-1 cells, vaspin reduced TNFα-induced adhesion of monocytes to HAECS in an AMPK-dependent manner.

Conclusions

Vaspin might attenuate the cytokine-induced expression of adhesion molecule genes by inhibiting NF-κB following AMPK activation.

Serum vaspin levels are positively associated with carotid atherosclerosis in a general population

OBJECTIVES

Vaspin is a novel adipocytokine with potential insulin-sensitizing properties. Insulin resistance (IR) plays a role in the development and progression of atherosclerosis. However, the relationship between serum vaspin levels and atherosclerosis remains unknown. Therefore, we investigated whether vaspin was correlated with carotid intima-media thickness (c-IMT).

METHODS

Data for fasting vaspin levels of 201 subjects (78 men and 123 women aged over 40 years) were obtained from a general population in Japan. We obtained anthropometric parameters and blood chemistries, and calculated homeostasis model assessment-IR (HOMA-IR) index. C-IMT was measured by B-mode ultrasonography. The mean values of each parameter by tertiles of vaspin were compared with analysis of variance, and the associations of vaspin with IR and c-IMT were evaluated by multiple stepwise regression analysis.

RESULTS

Univariate analysis revealed that vaspin levels were positively correlated with BMI, insulin, HOMA-IR index, estimated glomerular filtration rate (eGFR), c-IMT and hypertensive medication. Multiple stepwise regression analysis revealed that HOMA-IR index, c-IMT and eGFR were significantly and independently associated with vaspin. We performed multivariate analyses with c-IMT as the dependent variable. Age, hypertensive medication and vaspin were significant for c-IMT. Moreover, a mediation analysis demonstrated that vaspin was significantly related to c-IMT, independently of IR.

CONCLUSIONS

The present study not only confirmed the previous finding of the positive association of vaspin with IR but also demonstrated that serum vaspin level was positively associated with c-IMT, independently of IR in a general population. Our results may suggest a role of vaspin in atherosclerosis in humans.

Vaspin prevents methylglyoxal-induced apoptosis in human vascular endothelial cells by inhibiting reactive oxygen species generation

AIM

Vaspin (visceral adipose tissue-derived serine protease inhibitor) is a novel adipocytokine found in visceral white adipose tissues of obese type 2 diabetic rats. We have previously shown that vaspin has anti-inflammatory and antimigratory effects in vascular smooth muscle cells. Methylglyoxal (MGO) is an active metabolite of glucose and mediates diabetic vascular complications including endothelial cell (EC) apoptosis. Nonetheless, effects of vaspin on MGO-induced apoptosis of vascular EC remain to be determined. We investigated the effects of vaspin on MGO-induced apoptosis of human umbilical vein ECs (HUVECs).

METHODS

Human umbilical vein ECs were treated with MGO (560 μm, 12 h) in the absence or presence of vaspin (1 ng mL(-1), pre-treatment for 2 h). Cell death was evaluated by a cell counting assay. Apoptosis was determined by a terminal deoxyribonucleotide transferase-mediated deoxyuridine triphosphate nick-end labelling (TUNEL) assay. Cleaved caspase-3 expression was determined by Western blotting. Reactive oxygen species (ROS) generation was fluorometrically measured using 2', 7'-dichlorodihydrofluorescein diacetate. NADPH oxidase (NOX) activity was determined by a lucigenin assay.

RESULTS

Vaspin significantly inhibited MGO-induced HUVEC death. Vaspin significantly attenuated MGO-increased TUNEL-positive ECs. Moreover, vaspin significantly inhibited MGO-induced caspase-3 cleavage. Vaspin significantly inhibited MGO-induced ROS generation as well as NOX activation.

CONCLUSIONS

The present results for the first time demonstrate that vaspin inhibits MGO-induced EC apoptosis by preventing caspase-3 activation via the inhibition of NOX-derived ROS generation.

Association between serum vaspin level and metabolic syndrome in healthy Korean subjects

BACKGROUND

Visceral obesity is associated with insulin resistance, diabetes, and cardiovascular diseases. Vaspin [visceral adipose tissue (VAT)-derived serpin] may be a novel adipokine related to obesity and its metabolic consequences.

OBJECTIVE

The aim of this study was to investigate the relationships among serum vaspin levels and VAT and the components of metabolic syndrome.

METHODS

A cross-sectional analysis of healthy men (n=97) and women (n=156) for clinical, laboratory, and anthropometric factors was undertaken. Serum vaspin levels were measured. Abdominal VAT and subcutaneous adipose tissue were measured by computed tomography.

RESULTS

Of 253 subjects, 47 (18%) had metabolic syndrome: 33 men (34%) and 14 women (9%). Serum vaspin concentration was significantly lower in men than in women and significantly lower in men with metabolic syndrome than in men without metabolic syndrome. Serum vaspin level tended to decrease with increasing number of metabolic syndrome components, and was negatively correlated with waist circumference, systolic and diastolic blood pressure, serum triglyceride level, and abdominal VAT, but positively correlated with high-density lipoprotein cholesterol level. However, after adjustment for sex, this correlation disappeared.

CONCLUSIONS

Low serum vaspin levels are associated with male gender and metabolic syndrome, particularly in men, and with the majority of metabolic syndrome components.