Chemerin and vaspin: possible targets to treat obesity?

Interaction between Selected Adipokines and Musculoskeletal and Cardiovascular Systems: A Review of Current Knowledge

Adipokines are substances secreted by adipose tissue that are receiving increasing attention. The approach to adipose tissue has changed in recent years, and it is no longer looked at as just a storage organ but its secretion and how it influences systems in the human body are also looked at. The role of adipokine seems crucial in developing future therapies for pathologies of selected systems. In this study, we look at selected adipokines, leptin, adiponectin, chemerin, resistin, omentin-1, nesfatin, irisin-1, visfatin, apelin, vaspin, heparin-binding EGF-like growth factor (HB-EGF), and TGF-β2, and how they affect systems in the human body related to physical activity such as the musculoskeletal and cardiovascular systems.

AMP-activated protein kinase is a key regulator of obesity-associated factors

An imbalance between caloric intake and energy expenditure leads to obesity. Obesity is an important risk factor for the development of several metabolic diseases including insulin resistance, metabolic syndrome, type 2 diabetes mellitus, and cardiovascular disease. So, controlling obesity could be effective in the improvement of obesity-related diseases. Various factors are involved in obesity, such as AMP-activated protein kinases (AMPK), silent information regulators, inflammatory mediators, oxidative stress parameters, gastrointestinal hormones, adipokines, angiopoietin-like proteins, and microRNAs. These factors play an important role in obesity by controlling fat metabolism, energy homeostasis, food intake, and insulin sensitivity. AMPK is a heterotrimeric serine/threonine protein kinase known as a fuel-sensing enzyme. The central role of AMPK in obesity makes it an attractive molecule to target obesity and related metabolic diseases. In this review, the critical role of AMPK in obesity and the interplay between AMPK and obesity-associated factors were elaborated.

Crosstalk between skin inflammation and adipose tissue-derived products: pathogenic evidence linking psoriasis to increased adiposity

INTRODUCTION

Psoriasis is a chronic skin disorder associated with several comorbid conditions. In psoriasis pathogenesis, the role of some cytokines, including TNF-α and IL-17, has been elucidated. Beside their pro-inflammatory activity, they may also affect glucose and lipid metabolism, possibly promoting insulin resistance and obesity. On the other hand, adipose tissue, secreting adipokines such as chemerin, visfatin, leptin, and adiponectin, not only regulates glucose and lipid metabolism, and endothelial cell function regulation, but it may contribute to inflammation. Areas covered: This review provides an updated 'state-of-the-art' about the reciprocal contribution of a small subset of conventional cytokines and adipokines involved in chronic inflammatory pathways, upregulated in both psoriasis and increased adiposity. A systematic search was conducted using the PubMed Medline database for primary articles. Expert commentary: Because psoriasis is associated with increased adiposity, it would be important to define the contribution of chronic skin inflammation to the onset of obesity and vice versa. Clarifying the pathogenic mechanism underlying this association, a therapeutic strategy having favorable effects on both psoriasis and increased adiposity could be identified.

Chemerin: A comprehensive review elucidating the need for cardiovascular research

When chemerin was discovered in 1997, it was relegated to being a protein associated with the normal skin function contrasting the setting of psoriasis. However, with the discovery of multiple receptors for the chemerin protein and a vast collection of associations with various pathologies, chemerin has global influence capable of regulating chemotactic, adipokine, autocrine/paracrine, adipogenic, angiogenic, and reproductive functions. These individual abilities of chemerin are important for understanding its basic pharmacology and physiology, but application of these principles to human pathology relies on the ability of scientists and physicians to view this protein from a much wider, all-encompassing angle. A global participant in the action of chemerin is the cardiovascular system (CVS). Although the CVS may not have as many direct interactions (e.g. smooth muscle in endothelium) with chemerin as it does indirect (e.g. chemerin activation in the lumen by proteases), our basic understanding of the CVS and its relation to chemerin is necessary to form a proper grasp of its individual actions and make the applications to pathology. This review provides a fundamental, yet comprehensive review of chemerin that inherently identifies the CVS as a necessary link between chemerin and its associated pathologies, but also calls for basic cardiovascular research as the solution to this chasm between knowledge and application.

Chemerin/chemR23 axis in inflammation onset and resolution

Chemerin is an adipokine secreted by adipocytes and associated with obesity, insulin resistance and metabolic syndrome. Different chemerin fragments with pro- or anti-inflammatory action can be produced, depending on the class of proteases predominating in the microenvironment. Chemerin binds to three receptors, especially to chemR23, expressed on various cells, as dendritic cells, macrophages and natural killer cells, regulating chemotaxis towards the site of inflammation and activation status. Recently, the chemerin/chemR23 axis has attracted particular attention for the multiple roles related to the control of inflammation, metabolism and cancerogenesis in different organs and systems as lung (allergy and cancer), skin (psoriasis, lupus, cancer, wound repair), cardiovascular system (lipid profile and atherosclerosis), reproductive apparatus (polycystic ovary syndrome, follicular homoeostasis), and digestive tract (inflammatory bowel diseases and cancer). This pathway may regulate immune responses by contributing both to the pathogenesis of inflammatory diseases and to the resolution of acute inflammation. Thus, chemerin-derived peptides or other substances that may affect the chemerin/chemR23 axis could be used in the future for the treatment of many diseases, including cancer at different sites.

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.

Obesity, inflammation, and lung injury (OILI): the good

Obesity becomes pandemic, predisposing these individuals to great risk for lung injury. In this review, we focused on the anti-inflammatories and addressed the following aspects: adipocytokines and obesity, inflammation and other mechanisms, adipocytokines and lung injury in obesity bridged by inflammation, and potential therapeutic targets. To sum up, the majority of evidence supported that adiponectin, omentin, and secreted frizzled-related protein 5 (SFRP5) were reduced significantly in obesity, which is associated with increased inflammation, indicated by increase of TNFα and IL-6, through activation of toll-like receptor (TLR4) and nuclear factor light chain κB (NF-κB) signaling pathways. Administration of these adipocytokines promotes weight loss and reduces inflammation. Zinc-α2-glycoprotein (ZAG), vaspin, IL-10, interleukin-1 receptor antagonist (IL-1RA), transforming growth factor β (TGF-β1), and growth differentiation factor 15 (GDF15) are also regarded as anti-inflammatories. There were controversial reports. Furthermore, there is a huge lack of studies for obesity related lung injury. The effects of adiponectin on lung transplantation, asthma, chronic obstructive pulmonary diseases (COPD), and pneumonia were anti-inflammatory and protective in lung injury. Administration of IL-10 agonist reduces mortality of acute lung injury in rabbits with acute necrotizing pancreatitis, possibly through inhibiting proinflammation and strengthening host immunity. Very limited information is available for other adipocytokines.

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.

Chemerin connects fat to arterial contraction

OBJECTIVE

Obesity and hypertension are comorbid in epidemic proportion, yet their biological connection is largely a mystery. The peptide chemerin is a candidate for connecting fat deposits around the blood vessel (perivascular adipose tissue) to arterial contraction. We presently tested the hypothesis that chemerin is expressed in perivascular adipose tissue and is vasoactive, supporting the existence of a chemerin axis in the vasculature.

APPROACH AND RESULTS

Real-time polymerase chain reaction, immunohistochemistry, and Western analyses supported the synthesis and expression of chemerin in perivascular adipose tissue, whereas the primary chemerin receptor ChemR23 was expressed both in the tunica media and endothelial layer. The ChemR23 agonist chemerin-9 caused receptor, concentration-dependent contraction in the isolated rat thoracic aorta, superior mesenteric artery, and mesenteric resistance artery, and contraction was significantly amplified (more than 100%) when nitric oxide synthase was inhibited and the endothelial cell mechanically removed or tone was placed on the arteries. The novel ChemR23 antagonist CCX832 inhibited phenylephrine-induced and prostaglandin F2α-induced contraction (+perivascular adipose tissue), suggesting that endogenous chemerin contributes to contraction. Arteries from animals with dysfunctional endothelium (obese or hypertensive) demonstrated a pronounced contraction to chemerin-9. Finally, mesenteric arteries from obese humans demonstrate amplified contraction to chemerin-9.

CONCLUSIONS

These data support a new role for chemerin as an endogenous vasoconstrictor that operates through a receptor typically attributed to function only in immune cells.