Vaspin--a link of obesity and psoriasis?

The role of adipokines in the pathogenesis of psoriasis - a focus on resistin, omentin-1 and vaspin

BACKGROUND

Psoriasis is a chronic immune-mediated skin condition with several types of manifestation, including psoriatic arthritis. In recent years, studies have demonstrated multiple molecules and mechanisms that play important roles in the pathophysiology of psoriasis. Studies have been conducted to determine the role of adipokines, bioactive peptides secreted by the adipose tissue, in the pathogenesis of inflammatory diseases. These studies have shown that adipokines are dysregulated in psoriasis and their abnormal expression profile could contribute to the inflammatory mechanisms observed in psoriasis.

AREAS COVERED

In this review, we discuss the immunomodulatory features of resistin, omentin-1, and vaspin, and discuss their potential involvement in the pathogenesis of psoriasis.

EXPERT OPINION

The adipokines resistin, omentin, and vaspin appear to be promising therapeutic targets in psoriasis. It is important to seek to block the action of resistin, either by blocking its receptors or by blocking its systemic effects with antibodies. In the case of omentin and vaspin, substances that are receptor mimetics of these adipokines should be sought and studies conducted of their analogues for the treatment of psoriasis. To introduce these therapies into clinical practice, multicentre clinical trials are required to confirm their efficacy and safety after initial studies in animal models.

New Aspects of Corpus Luteum Regulation in Physiological and Pathological Conditions: Involvement of Adipokines and Neuropeptides

The corpus luteum is a small gland of great importance because its proper functioning determines not only the appropriate course of the estrous/menstrual cycle and embryo implantation, but also the subsequent maintenance of pregnancy. Among the well-known regulators of luteal tissue functions, increasing attention is focused on the role of neuropeptides and adipose tissue hormones-adipokines. Growing evidence points to the expression of these factors in the corpus luteum of women and different animal species, and their involvement in corpus luteum formation, endocrine function, angiogenesis, cells proliferation, apoptosis, and finally, regression. In the present review, we summarize the current knowledge about the expression and role of adipokines, such as adiponectin, leptin, apelin, vaspin, visfatin, chemerin, and neuropeptides like ghrelin, orexins, kisspeptin, and phoenixin in the physiological regulation of the corpus luteum function, as well as their potential involvement in pathologies affecting the luteal cells that disrupt the estrous cycle.

Review: Vaspin (SERPINA12) Expression and Function in Endocrine Cells

Proper functioning of the body depends on hormonal homeostasis. White adipose tissue is now known as an endocrine organ due to the secretion of multiple molecules called adipokines. These proteins exert direct effects on whole body functions, including lipid metabolism, angiogenesis, inflammation, and reproduction, whereas changes in their level are linked with pathological events, such as infertility, diabetes, and increased food intake. Vaspin-visceral adipose tissue-derived serine protease inhibitor, or SERPINA12 according to serpin nomenclature, is an adipokine discovered in 2005 that is connected to the development of insulin resistance, obesity, and inflammation. A significantly higher amount of vaspin was observed in obese patients. The objective of this review was to summarize the latest findings about vaspin expression and action in endocrine tissues, such as the hypothalamus, pituitary gland, adipose tissue, thyroid, ovary, placenta, and testis, as well as discuss the link between vaspin and pathologies connected with hormonal imbalance.

Adipokines change the balance of proliferation/apoptosis in the ovarian cells of human and domestic animals: A comparative review

Adipose tissue secretes multiple hormones termed adipokines, which are important regulators of many processes. There are four types of evidence supporting an association between adipokines and female fertility which are effects that occur: centrally at the pituitary; peripherally and locally at the ovary and reproductive tract; directly on the oocyte/embryo and during pregnancy. In this review, there was a focus on the description of adipokines (leptin, apelin, resistin, chemerin, adiponectin, vaspin and visfatin) on ovarian cell proliferation, cell cycle progression and apoptosis in comparison to effects on human and domestic animal ovaries including pigs, cattle and chickens. Knowledge about molecules which regulate the balance between proliferation and apoptosis so that these processes are optimal for ovarian function is essential for understanding the physiology and reducing the incidence of infertility. Furthermore, oogenesis, folliculogenesis, oocyte loss/selection and atresia are important processes for optimal ovarian physiological functions. There, however, is ovulation from only a few follicles, while the majority undergo atresia that is induced by apoptosis.

Association between Vaspin rs2236242 Gene Polymorphism and Psoriasis Vulgaris

BACKGROUND

Psoriasis known as a chronic inflammatory skin disease is accompanied by metabolic disorders such as obesity, diabetes, and dyslipidemia. Vaspin (a serine protease inhibitor derived from visceral adipose tissue) is a newly identified adipokine and a link between inflammation and obesity has been reported. We aimed to determine whether vaspin gene polymorphism is associated with the development and/or clinical features of psoriasis vulgaris.

METHODS

Our study group consisted of 96 psoriasis vulgaris patients and 100 matched controls. Vaspin rs2236242 gene was genotyped using PCR.

RESULTS

The vaspin genotypes showed a meaningful difference between psoriasis and control groups (p = 0.02). The frequency of the vaspin rs2236242 TT genotype was lower in psoriasis patients than in control participants (p < 0.05). The TA genotype was associated with a 2.38-fold increased risk of psoriasis compared to the TT genotype (p = 0.007, odds ratio: 2.38; 95% confidence interval: 1.25-4.55), but not the AA genotype. All subjects were the Turkish population, the study in other populations is needed and the sample size was small in number.

CONCLUSION

Our study demonstrated that vaspin rs2236242 polymorphism is related to psoriasis in the Turkish population. Polymorphisms of the vaspin gene might serve as diagnostic biomarkers of psoriasis.

Adipokines in the Skin and in Dermatological Diseases

Adipokines are the primary mediators of adipose tissue-induced and regulated systemic inflammatory diseases; however, recent findings revealed that serum levels of various adipokines correlate also with the onset and the severity of dermatological diseases. Importantly, further data confirmed that the skin serves not only as a target for adipokine signaling, but may serve as a source too. In this review, we aim to provide a complex overview on how adipokines may integrate into the (patho) physiological conditions of the skin by introducing the cell types, such as keratinocytes, fibroblasts, and sebocytes, which are known to produce adipokines as well as the signals that target them. Moreover, we discuss data from in vivo and in vitro murine and human studies as well as genetic data on how adipokines may contribute to various aspects of the homeostasis of the skin, e.g., melanogenesis, hair growth, or wound healing, just as to the pathogenesis of dermatological diseases such as psoriasis, atopic dermatitis, acne, rosacea, and melanoma.

Adipokines as Biomarkers of Atopic Dermatitis in Adults

Atopic dermatitis (AD) is characterized by chronic, relapsing, pruritic skin inflammation and does not have a well-understood pathogenesis. In this study, we addressed the contribution of adipokines to AD eczema based on the assessment of blood levels of adiponectin, resistin, leptin, lipocalin-2, and vaspin in adult non-obese patients suffering from chronic extrinsic childhood-onset AD. We investigated 49 AD patients with a median age of 37 years. The control group consisted of 30 age-matched healthy subjects. Adipokines were assessed in the serum by ELISA assays and the severity of AD with the SCORing Atopic Dermatitis (SCORAD) index. We found that adiponectin and resistin decreased and leptin appreciably increased in AD patients when compared to those in healthy subjects. Further, the levels of adiponectin and resistin were inversely related to the intensity of eczema. In conclusion, apart from the formerly investigated role of leptin in AD, this study points to adiponectin and resistin as the potential candidate adipokine biomarkers involved in shaping eczema intensity and severity, which may help predict disease exacerbations and enable the development of effective targeted therapeutic interventions.

Association of vaspin rs2236242 gene variants with type 2 diabetes and obesity in a Chinese population: A prospective, single-center study

AIM

Vaspin is an adipokine separated from visceral fat tissues of obese diabetic rats. This study was to investigate the association between vaspin rs2236242 gene polymorphism and type 2 diabetes mellitus (T2DM) or obesity in a Chinese population.

MATERIALS AND METHODS

T2DM patients and nondiabetic controls were recruited from Qingpu Branch of Zhongshan Hospital Affiliated to Fudan University (Shanghai, China) from May 1, 2015 to June 30, 2017. Clinicopathologic characteristics were recorded and their blood samples were collected. Serum vaspin levels were detected by enzyme-linked immunosorbent assay and vaspin rs2236242 genotypes by tetra-amplification refractory mutation system-polymerase chain reaction.

RESULTS

Two hundred and ninety-nine patients with T2DM and 311 controls were recruited at last. The vaspin genotypes of diabetic patients were distinct from nondiabetic controls (χ ²  = 54.611, p < 0.0001). Genotyping revealed that T2DM patients have a greater prevalence of A allele compared with controls (61.9% vs. 42.1%, p < 0.0001). A allele was associated with an increased risk of T2DM (odds ratio = 2.23, 95% confidence interval = 1.773-2.804, p < 0.0001) compared with T allele. The genotype distribution did not differ among nondiabetic subjects with or without obesity. The serum vaspin levels were higher in T2DM patients and obese controls than the nonobese controls, however, the rs2236242 was not found to be significantly related to serum vaspin levels.

CONCLUSIONS

Our findings showed the association between vaspin rs2236242 gene variants with obesity and T2DM in a Chinese population. People with rs2236242 A allele had a 2.23-fold increased risk of T2DM. These findings suggest that vaspin rs2236242 may serve as a potential diagnostic and/or therapeutic targets for T2DM.

Molecular Mechanisms of Vaspin Action - From Adipose Tissue to Skin and Bone, from Blood Vessels to the Brain

Visceral adipose tissue-derived serine protease inhibitor (vaspin) or SERPINA12 according to the serpin nomenclature was identified together with other genes and gene products that were specifically expressed or overexpressed in the intra-abdominal or visceral adipose tissue (AT) of the Otsuka Long-Evans Tokushima fatty rat. These rats spontaneously develop visceral obesity, insulin resistance, hyperinsulinemia and -glycemia, as well as hypertension and thus represent a well suited animal model of obesity and related metabolic disorders such as type 2 diabetes.The follow-up study reporting the cloning, expression and functional characterization of vaspin suggested the great and promising potential of this molecule to counteract obesity induced insulin resistance and inflammation and has since initiated over 300 publications, clinical and experimental, that have contributed to uncover the multifaceted functions and molecular mechanisms of vaspin action not only in the adipose, but in many different cells, tissues and organs. This review will give an update on mechanistic and structural aspects of vaspin with a focus on its serpin function, the physiology and regulation of vaspin expression, and will summarize the latest on vaspin function in various tissues such as the different adipose tissue depots as well as the vasculature, skin, bone and the brain.

Tissue-engineered human psoriatic skin supplemented with cytokines as an in vitro model to study plaque psoriasis

AIM

Psoriasis is a chronic inflammatory skin disease. To study its complex etiology, a psoriatic skin substitute model supplemented with a cytokine cocktail has been used.

MATERIALS & METHODS

Reconstructed psoriatic skin substitutes were supplemented with a cocktail of four cytokines: TNF-α, IL-1α, IL-6 and IL-17A, to monitor their impact on gene expression by DNA microarray.

RESULTS

Gene profiling analyses identified several deregulated genes reported as being also deregulated in psoriasis skin in vivo (S100A12, IL-8, DEFB4A and KYNU). The expression of those genes was dramatically increased compared with basal levels of controls (p < 0.005 to < 0.05).

CONCLUSION

Psoriatic substitutes supplemented with a cocktail of TNF-α, IL-1α, IL-6 and IL-17A showed similar transcriptome alterations to those found in psoriasis.

The triad psoriasis-obesity-adipokine profile

Psoriasis is a chronic inflammatory skin disease, often associated with overweight/obesity. The adipose tissue is a complex organ that secretes several adipokines, involved in the regulation of some metabolic processes, such as lipid metabolism, glucose homeostasis, angiogenesis, blood pressure and inflammation. In obesity, the distribution and function of adipose tissue, and the adipokine profile are altered. The unbalanced production of pro- and anti-inflammatory adipokines in obesity, contributes to the development of a chronic low-grade inflammation state, which seems to favour worsening of psoriasis lesion and a poorer response to treatment. In this review, we will debate published data concerning the current knowledge about the triad psoriasis-obesity-adipokine profile.

Association of Adipokines, Insulin Resistance, Hypertension and Dyslipidemia in Patients with Psoriasis Vulgaris

Background

Systemic inflammation in psoriasis causes insulin resistance and cardiovascular diseases. Adipokines are adipose-tissue-derived factors that are involved in metabolic processes. It is thought that these adipokines are associated with the development of psoriasis.

Objective

The purpose of this study was to determine the changes in adipokine levels, insulin resistance, hypertension, and dyslipidemia over a 12-week period.

Methods

The study comprised 35 psoriasis patients and 50 controls. Blood samples were obtained twice from the patients, one sample at the start and one at the end of a 12-week follow-up period. The following parameters were assessed in both groups: serum fasting glucose, fasting insulin, homeostasis model assessment-estimated insulin resistance (HOMA-IR) index, serum lipids, adiponectin, leptin, resistin, chemerin, omentin, vaspin, visfatin, retinol-binding protein 4, and high-sensitivity C-reactive protein (hs-CRP) levels; blood pressure; body mass index; and the psoriasis area severity index (PASI) scores.

Results

The patients showed an improvement in the PASI score and a significant decrease in serum hs-CRP, omentin, and chemerin values. Moreover, at the start of the follow-up, the psoriasis patients had significantly lower levels of adiponectin and visfatin and significantly higher levels of vaspin and resistin than those of the control group. Visfatin levels correlated negatively with low-density lipoprotein (LDL) and cholesterol, while vaspin and omentin levels correlated positively with diastolic blood pressure. Decreased adiponectin levels correlated negatively with diastolic blood pressure and LDL.

Conclusion

Plasma levels of adipokines might be useful for evaluating the disease activity of psoriasis and its comorbidities.

A unique serpin P1' glutamate and a conserved β-sheet C arginine are key residues for activity, protease recognition and stability of serpinA12 (vaspin)

SerpinA12 (vaspin) is thought to be mainly expressed in adipose tissue and has multiple beneficial effects on metabolic, inflammatory and atherogenic processes related to obesity. KLK7 (kallikrein 7) is the only known protease target of vaspin to date and is inhibited with a moderate inhibition rate. In the crystal structure, the cleavage site (P1-P1') of the vaspin reactive centre loop is fairly rigid compared with the flexible residues before P2, possibly supported by an ionic interaction of P1' glutamate (Glu(379)) with an arginine residue (Arg(302)) of the β-sheet C. A P1' glutamate seems highly unusual and unfavourable for the protease KLK7. We characterized vaspin mutants to investigate the roles of these two residues in protease inhibition and recognition by vaspin. Reactive centre loop mutations changing the P1' residue or altering the reactive centre loop conformation significantly increased inhibition parameters, whereas removal of the positive charge within β-sheet C impeded the serpin-protease interaction. Arg(302) is a crucial contact to enable vaspin recognition by KLK7 and it supports moderate inhibition of the serpin despite the presence of the detrimental P1' Glu(379), which clearly represents a major limiting factor for vaspin-inhibitory activity. We also show that the vaspin-inhibition rate for KLK7 can be modestly increased by heparin and demonstrate that vaspin is a heparin-binding serpin. Noteworthily, we observed vaspin as a remarkably thermostable serpin and found that Glu(379) and Arg(302) influence heat-induced polymerization. These structural and functional results reveal the mechanistic basis of how reactive centre loop sequence and exosite interaction in vaspin enable KLK7 recognition and regulate protease inhibition as well as stability of this adipose tissue-derived serpin.

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.

High serum vaspin concentrations in patients with ulcerative colitis

BACKGROUND

Adipocytokines are associated with energy homeostasis and mediate various immune responses and inflammatory processes. Vaspin is a novel adipocytokine that is thought to exhibit anti-inflammatory effects.

AIM

We aimed to evaluate serum vaspin levels in inflammatory bowel disease (IBD) and determine its possible associations with the course and to clarify its intestinal localization.

METHODS

Serum samples were obtained from patients with Crohn's disease (CD; n = 30) and ulcerative colitis (UC; n = 33) and from healthy volunteers (controls; n = 26). Enzyme-linked immunosorbent assays were performed for all patients. Vaspin immunohistochemical staining was performed for intestines affected with IBD.

RESULTS

Serum vaspin concentrations were significantly higher in patients with UC than in patients with CD and controls (422.9 ± 361.9 vs. 163.4 ± 116.2 vs. 147.5 ± 89.4 pg/mL, respectively; P < 0.01). There was no difference in the serum vaspin concentrations between the patients with CD and controls. There was also no difference in the serum vaspin concentrations between the patients with active IBD and those with inactive IBD. However, the serum vaspin concentrations of most patients with UC increased after remission induction. Vaspin was expressed in the adipocytes of the mesenteric adipose tissues but not in the epithelial or inflammatory cells of large intestines of the patients with IBD.

CONCLUSIONS

Serum vaspin concentrations are elevated in patients with UC and increase further after remission induction, suggesting that vaspin may aid the auxiliary diagnosis of UC and may be useful for assessing disease activity in patients.

Adipocytokines and psoriasis: Insights into mechanisms linking obesity and inflammation to psoriasis

Psoriasis has been lately seen as a potential systemic inflammatory disease associated with a range of co-morbidities exhibiting an overlapping pathology and presenting a great social health impact such as cardiovascular disease and metabolic diseases, including obesity. Adipose tissue is considered a genuine endocrine organ producing a variety of bioactive adipocytokines, like leptin, adiponectin, resistin and visfatin, participating in physiological and pathological processes, such as energy balance, insulin sensitivity and resistance, immunity, inflammation, hematopoiesis and angiogenesis. Adipocytokines could serve as a missing link in the association between psoriasis, obesity and metabolic co-morbidities. In chronic inflammatory disease states such as psoriasis, adipocytokines may be implicated in psoriasis onset, progression, severity as well as in the pathogenesis of co-morbidities. Measuring serum adipocytokine levels in the future may be useful in predicting psoriasis severity, progression, treatment outcome and risk of any co-morbidities. Interventions to decrease pro-inflammatory adipocytokine levels could offer preventive and therapeutic options for improving psoriasis severity and protecting against its co-morbidities. Candidate strategic interventions incorporate increased physical activity, weight control and pharmacologic approaches such as metformin. However, the mechanisms underlying the actions of adipocytokines in psoriasis as well as their potential diagnostic, prognostic and/or therapeutic utility require further investigation with larger prospective, longitudinal and mechanistic studies.

Proteolytic activation of prochemerin by kallikrein 7 breaks an ionic linkage and results in C-terminal rearrangement

The excessive accumulation of adipose tissue in obesity is associated with multiple inflammatory dermatological diseases. Chemerin, a chemoattractant adipokine, dependent on proteolytical activation, is highly expressed in skin. Different proteases have been reported to activate prochemerin, but none is inherently expressed in human skin. In the present study, we identified a tissue-specific protease and investigated the underlying mechanism of activation at the molecular level. We characterized human KLK7 (kallikrein 7) as a prochemerin processing protease in vitro converting prochemerin into active chemerinF(156). The activating truncation by the protease might trigger a structural rearrangement leading to an increased affinity of chemerin to CMKLR1 (chemokine-like receptor 1). Molecular modelling and experimental data suggest an underlying ionic interaction in prochemerin C-terminal domains. These findings provide a general molecular basis for the necessity of C-terminal processing of prochemerin. Moreover, immunohistochemistry was used to investigate prochemerin, KLK7 and the recently identified KLK7 inhibitor vaspin expression in human skin biopsies, and distinct co-localization in psoriatic biopsies was observed. On the basis of these results, it is hypothesized that KLK7 activity may contribute to the development of psoriatic lesions as a consequence of excessive chemerin activation and impaired protease activity regulation by vaspin. Therefore this interaction represents an interesting target for psoriasis therapy and treatment of other obesity-related diseases.

Vaspin attenuates RANKL-induced osteoclast formation in RAW264.7 cells

Visceral adipose tissue-derived serine protease inhibitor (vaspin), an adipokine that was recently identified in a rat model of type 2 diabetes, has been suggested to have an insulin-sensitizing effect. In this study, we investigated whether vaspin inhibits receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis using two types of osteoclast precursors: RAW264.7 cells and bone marrow cells (BMCs). Vaspin inhibited RANKL-induced osteoclastogenesis in RAW264.7 cells and BMCs. Interestingly, vaspin also inhibited the RANKL-induced expression of nuclear factor of activated T cells c1 (NFATc1) in RAW264.7 cells and BMCs. Furthermore, it inhibited the RANKL-induced upregulation of matrix metalloproteinase-9 and cathepsin K in RAW264.7 cells. Thus, we suggest that vaspin downregulates osteoclastogenesis in part by inhibiting expression of the transcription factor NFATc1.

Vaspin inhibits kallikrein 7 by serpin mechanism

The molecular target of the adipokine vaspin (visceral adipose tissue-derived serpin; serpinA12) and its mode of action are unknown. Here, we provide the vaspin crystal structure and identify human kallikrein 7 (hK7) as a first protease target of vaspin inhibited by classical serpin mechanism with high specificity in vitro. We detect vaspin-hK7 complexes in human plasma and find co-expression of both proteins in murine pancreatic β-cells. We further demonstrate that hK7 cleaves human insulin in the A- and B-chain. Vaspin treatment of isolated pancreatic islets leads to increased insulin concentration in the media upon glucose stimulation without influencing insulin secretion. By application of vaspin and generated inactive mutants, we find the significantly improved glucose tolerance in C57BL/6NTac and db/db mice treated with recombinant vaspin fully dependent on the vaspin serpin activity and not related to vaspin-mediated changes in insulin sensitivity as determined by euglycemic-hyperinsulinemic clamp studies. Improved glucose metabolism could be mediated by increased insulin plasma concentrations 150 min after a glucose challenge in db/db mice, supporting the hypothesis that vaspin may inhibit insulin degradation by hK7 in the circulation. In conclusion, we demonstrate the inhibitory serpin nature and the first protease target of the adipose tissue-derived serpin vaspin, and our findings suggest hK7 inhibition by vaspin as an underlying physiological mechanism for its compensatory actions on obesity-induced insulin resistance.

Chemerin and vaspin: possible targets to treat obesity?

Obesity is one of the main human epidemics today. The increase in fat accumulation, which is associated with obesity, may significantly change the expression of several bioactive molecules known as adipokines. These adipokines interact not only with adipose tissue, but also with metabolically relevant organs such as liver and muscle. Understanding the molecular basics of potential novel targets might help to improve the therapeutic treatment of people who suffer from obesity. Herein we summarize the state of the art of two novel adipokines and their impaired or protective action in obesity: chemerin and vaspin. Their expression patterns, signal transduction activity, and resulting functions within the human body are introduced. We also discuss various possibilities to target these adipokines, which may represent promising new targets for the treatment of obesity by small and synthetic compounds.