Towards an integrative approach to understanding the role of chemerin in human health and disease

The adipokine chemerin amplifies electrical field-stimulated contraction in the isolated rat superior mesenteric artery

The adipokine chemerin causes arterial contraction and is implicated in blood pressure regulation, especially in obese subjects with elevated levels of circulating chemerin. Because chemerin is expressed in the perivascular adipose tissue (PVAT) that surrounds the sympathetic innervation of the blood vessel, we tested the hypothesis that chemerin (endogenous and exogenous) amplifies the sympathetic nervous system in mediating electrical field-stimulated (EFS) contraction. The superior mesenteric artery, with or without PVAT and with endothelium and sympathetic nerve intact, was mounted into isolated tissue baths and used for isometric contraction and stimulation. Immunohistochemistry validated a robust expression of chemerin in the PVAT surrounding the superior mesenteric artery. EFS (0.3-20 Hz) caused a frequency-dependent contraction in isolated arteries that was reduced by the chemerin receptor ChemR23 antagonist CCX832 alone (100 nM; with, but not without, PVAT), but not by the inactive congener CCX826 (100 nM). Exogenous chemerin-9 (1 μM)-amplified EFS-induced contraction in arteries (with and without PVAT) was blocked by CCX832 and the α-adrenergic receptor antagonist prazosin. CCX832 did not directly inhibit, nor did chemerin directly amplify, norepinephrine-induced contraction. Whole mount immunohistochemical experiments support colocalization of ChemR23 with the sympathetic nerve marker tyrosine hydroxylase in superior mesenteric PVAT and, to a lesser extent, in arteries and veins. These studies support the idea that exogenous chemerin modifies sympathetic nerve-mediated contraction through ChemR23 and that ChemR23 may be endogenously activated. This is significant because of the well-appreciated role of the sympathetic nervous system in blood pressure control.

The role of adipokines in chronic inflammation

Adipose tissue has traditionally been defined as connective tissue that stores excess calories in the form of triacylglycerol. However, the physiologic functions attributed to adipose tissue are expanding, and it is now well established that adipose tissue is an endocrine gland. Among the endocrine factors elaborated by adipose tissue are the adipokines; hormones, similar in structure to cytokines, produced by adipose tissue in response to changes in adipocyte triacylglycerol storage and local and systemic inflammation. They inform the host regarding long-term energy storage and have a profound influence on reproductive function, blood pressure regulation, energy homeostasis, the immune response, and many other physiologic processes. The adipokines possess pro- and anti-inflammatory properties and play a critical role in integrating systemic metabolism with immune function. In calorie restriction and starvation, proinflammatory adipokines decline and anti-inflammatory adipokines increase, which informs the host of energy deficits and contributes to the suppression of immune function. In individuals with normal metabolic status, there is a balance of pro- and anti-inflammatory adipokines. This balance shifts to favor proinflammatory mediators as adipose tissue expands during the development of obesity. As a consequence, the proinflammatory status of adipose tissue contributes to a chronic low-grade state of inflammation and metabolic disorders associated with obesity. These disturbances are associated with an increased risk of metabolic disease, type 2 diabetes, cardiovascular disease, and many other pathological conditions. This review focuses on the impact of energy homeostasis on the adipokines in immune function.

A role for novel adipose tissue-secreted factors in obesity-related carcinogenesis

Obesity, a pandemic disease, is caused by an excessive accumulation of fat that can have detrimental effects on health. Adipose tissue plays a very important endocrine role, secreting different molecules that affect body physiology. In obesity, this function is altered, leading to a dysfunctional production of several factors, known as adipocytokines. This process has been linked to various comorbidities associated with obesity, such as carcinogenesis. In fact, several classical adipocytokines with increased levels in obesity have been demonstrated to exert a pro-carcinogenic role, including leptin, TNF-α, IL-6 and resistin, whereas others like adiponectin, with decreased levels in obesity, might have an anti-carcinogenic function. In this expanding field, new proteomic techniques and approaches have allowed the identification of novel adipocytokines, a number of which exhibit an altered production in obesity and type 2 diabetes and thus are related to adiposity. Many of these novel adipocytokines have also been identified in various tumour types, such as that of the breast, liver or endometrium, thereby increasing the list of potential contributors to carcinogenesis. This review is focused on the regulation of these novel adipocytokines by obesity, including apelin, endotrophin, FABP4, lipocalin 2, omentin-1, visfatin, chemerin, ANGPTL2 or osteopontin, emphasizing its involvement in tumorigenesis.

CMKLR1 deficiency influences glucose tolerance and thermogenesis in mice on high fat diet

Obesity has become a global epidemic disease, contributing to increases in the prevalence of type 2 diabetes. CMKLR1, one of the receptors for chemerin, has a wide range of functions in physiological and pathological activity, including innate and adaptive immunity, inflammation, metabolism and reproduction. In our study, CMKLR1 deficiency did not influence the gain of body weight but did exacerbate glucose intolerance, increase serum insulin level, and promote insulin resistance in mice on high fat diets. The expression of thermogenesis related genes was examined and indicated to decrease in CMKLR1 knockout (KO) mice in both normal and cold environments, which indicated CMKLR1 influence the thermogenesis process. Cold exposure induced significant body mass decrease and improved glucose tolerance and insulin resistance in wild type HFD mice but had no obvious effect on CMKLR1 KO HFD mice. In vitro, loss of CMKLR1 did not significantly influence the differentiation of stromal vascular fibroblasts (SVFs) derived from adipose tissue, but did suppress the expression of thermogenesis related genes. Collectively, these data demonstrate that CMKLR1 deficiency induces inbalance of glucose metabolism and impairs the cold induced-thermogenesis process in high diet models.

CMKLR1 and GPR1 mediate chemerin signaling through the RhoA/ROCK pathway

Chemerin is an adipose-derived hormone that regulates immunity and energy homesotasis. To date, all known chemerin functions have been attributed to activation of the G protein-coupled receptor chemokine-like receptor-1 (CMKLR1). Chemerin is also the only known ligand for a second receptor, G protein-coupled receptor-1 (GPR1), whose signaling and function remains unknown. This study investigated the in vitro signal transduction mechanisms of CMKLR1 and GPR1 using a panel of luciferase-reporters and pathway-specific inhibitors. Herein we report the novel finding that chemerin signals through a RhoA and rho-associated protein kinase (ROCK)-dependent pathway for activation of the transcriptional regulator serum-response factor (SRF). Despite similarities in RhoA/ROCK, Gαi/o, and MAPK signaling, we also demonstrate species-specific and receptor-dependent variations in GPR1 and CMKLR1 signaling and expression of the SRF target genes EGR1, FOS and VCL. Moreover, we demonstrate that signaling through p38, Gαi/o, RhoA, and ROCK is required for chemerin-mediated chemotaxis of L1.2 lymphocytes and AGS gastric adenocarcinoma cells. These results provide, to our knowledge, the first empirical evidence that GPR1 is a functional chemerin receptor and identify RhoA/SRF as a novel chemerin-signaling axis via both CMKLR1 and GPR1.

Crosstalk between intestinal microbiota, adipose tissue and skeletal muscle as an early event in systemic low-grade inflammation and the development of obesity and diabetes

Obesity is associated with a systemic chronic low-grade inflammation that contributes to the development of metabolic disorders such as cardiovascular diseases and type 2 diabetes. However, the etiology of this obesity-related pro-inflammatory process remains unclear. Most studies have focused on adipose tissue dysfunctions and/or insulin resistance in skeletal muscle cells as well as changes in adipokine profile and macrophage recruitment as potential sources of inflammation. However, low-grade systemic inflammation probably involves a complex network of signals interconnecting several organs. Recent evidences have suggested that disturbances in the composition of the gut microbial flora and alterations in levels of gut peptides following the ingestion of a high-fat diet may be a cause of low-grade systemic inflammation that may even precede and predispose to obesity, metabolic disorders or type 2 diabetes. This hypothesis is appealing because the gastrointestinal system is first exposed to nutrients and may thereby represent the first link in the chain of events leading to the development of obesity-associated systemic inflammation. Therefore, the present review will summarize the latest advances interconnecting intestinal mucosal bacteria-mediated inflammation, adipose tissue and skeletal muscle in a coordinated circuitry favouring the onset of a high-fat diet-related systemic low-grade inflammation preceding obesity and predisposing to metabolic disorders and/or type 2 diabetes. A particular emphasis will be given to high-fat diet-induced alterations of gut homeostasis as an early initiator event of mucosal inflammation and adverse consequences contributing to the promotion of extended systemic inflammation, especially in adipose and muscular tissues.

Local chemerin levels are positively associated with DSS-induced colitis but constitutive loss of CMKLR1 does not protect against development of colitis

Inflammatory bowel disease (IBD) is a family of disorders including ulcerative colitis and Crohn's disease that are characterized by chronic and relapsing intestinal inflammation. Increased production of proinflammatory mediators, possibly combined with low expression of anti-inflammatory mediators, is thought to promote the development and progression of IBD. In the current study, we demonstrate that expression, secretion, and processing of chemerin, a potent chemoattractant for cells expressing chemokine-like receptor 1 (CMKLR1), increased in the cecum and colon along a gradient positively associated with the severity of inflammation in dextran sodium sulfate (DSS)-induced colitis. We also show that levels of circulating bioactive chemerin increased following DSS treatment. At both 6-8 and 14-16 weeks of age, CMKLR1 knockout mice developed signs of clinical illness more slowly than wild type and had changes in circulating cytokine levels, increased spleen weight, and increased local chemerin secretion following DSS treatment. However, knockout mice ultimately developed similar levels of clinical illness and local inflammation as wild type. Finally, contrary to previous reports, intraperitoneal injection of bioactive chemerin had no effect on the severity of DSS-induced colitis. This suggests that local chemerin levels have a greater impact than circulating levels in the pathogenesis of colitis. Considered altogether, bioactive chemerin represents a novel biomarker for IBD severity, although strategies to modulate endogenous chemerin signaling other than chronic CMKLR1 loss are necessary in order to exploit chemerin as a therapeutic target for the treatment of IBD.

Chemerin15-Ameliorated Cardiac Ischemia-Reperfusion Injury Is Associated with the Induction of Alternatively Activated Macrophages

Chemerin15 (C15), an endogenous anti-inflammatory component, inhibits the activity of neutrophils and macrophages through G protein-coupled receptor ChemR23; however, its role as well as functional mechanism in mouse myocardial ischemia/reperfusion (I/R) injury remains unknown. Methods. Sham or I/R operations were performed on C57BL/6J mice. The I/R mice received an injection of C15 immediately before reperfusion. Serum troponin T levels, infarct size, cardiomyocyte apoptosis, reactive oxygen species (ROS) production, and infiltration of neutrophils were assessed 24 h after reperfusion, while the macrophage phenotypes, macrophage infiltration, and inflammatory cytokine levels were assessed 48 h after reperfusion. Results. Compared with the control group, the C15-treated mice showed an obvious amelioration of I/R injury and displayed less ROS, accompanied by reduced neutrophil recruitment. C15 decreased the tumor necrosis factor- (TNF-) α and interleukin- (IL-) 6 levels and increased the IL-10 levels in the serum of the I/R mice, which suggested a suppressed inflammatory response that could be related to elevated alternatively activated M2 macrophages with characteristic skewed expression of M2 markers and inhibition of classically activated M1 marker expression. Conclusion. C15 may induce alternatively activated M2 macrophage polarization and suppress the inflammatory response to protect against myocardial I/R injury in mice.

Biomarkers of insulin sensitivity and insulin resistance: Past, present and future

Insulin resistance in insulin target tissues including liver, skeletal muscle and adipose tissue is an early step in the progression towards type 2 diabetes. Accurate diagnostic parameters reflective of insulin resistance are essential. Longstanding tests for fasting blood glucose and HbA1c are useful and although the hyperinsulinemic euglycemic clamp remains a "gold standard" for accurately determining insulin resistance, it cannot be implemented on a routine basis. The study of adipokines, and more recently myokines and hepatokines, as potential biomarkers for insulin sensitivity is now an attractive and relatively straightforward approach. This review discusses potential biomarkers including adiponectin, RBP4, chemerin, A-FABP, FGF21, fetuin-A, myostatin, IL-6, and irisin, all of which may play significant roles in determining insulin sensitivity. We also review potential future directions of new biological markers for measuring insulin resistance, including metabolomics and gut microbiome. Collectively, these approaches will provide clinicians with the tools for more accurate, and perhaps personalized, diagnosis of insulin resistance.

Biliopancreatic diversion with duodenal switch modifies plasma chemerin in early and late post-operative periods

OBJECTIVE

Bariatric surgery remains the most effective treatment for obesity and metabolic syndrome. Surgical benefit arises from early-phase resolution of hyperglycemia and late-phase weight loss. The adipokine chemerin is of interest given its roles in immunity, adipogenesis, and metabolism. The study objective was to examine the effects of biliopancreatic diversion with duodenal switch (BPD-DS) on plasma chemerin in the early and late post-operative stages.

METHODS

83 adults with obesity undergoing BPD-DS, 45 obese non-surgical controls, and 9 lean surgical controls were enrolled. Plasma parameters and anthropometric measures were obtained at baseline and at, early (24 h, 5 D) and late (6 months and 12 months) post-operative stages.

RESULTS

Plasma chemerin dropped from 176±49 ng/mL at baseline to 132±52 ng/mL 24 h after BPD-DS, rebounded to 200±66 ng/mL after 5 D, and declined to 124±51 and 110±34 ng/mL after 6 and 12 months. Plasma chemerin correlated negatively with measures of inflammation and hepatic injury and positively with measures of obesity, metabolic syndrome, and inflammation in the early and late post-operative periods, respectively.

CONCLUSIONS

Chemerin has a novel role in surgical injury but not hyperglycemia resolution early after BPD-DS. Over the long term, plasma chemerin declines to a new set point that is partially determined by body fat reductions.

Protective effect of liraglutide against ER stress in the liver of high-fat diet-induced insulin-resistant rats

The purpose of this study was to investigate whether the glucagon-like peptide-1 (GLP-1) analog liraglutide can alleviate endoplasmic reticulum (ER) stress and insulin resistance (IR) in the liver of high-fat diet-induced insulin-resistant rats. Eighty-five male Sprague-Dawley rats were fed with normal chow or a high-fat diet for 12 weeks. The IR was evaluated using the hyperinsulinemic-euglycemic clamp technique. The rats in the HF group were further divided into four groups and were treated with or without liraglutide by subcutaneous injection. Body weight (BW), fasting blood glucose (FBG), fasting insulin (FINS), and insulin sensitivity were measured. The expression of ER stress marker GRP78 and its signaling mediators, such as IRE1α, PERK, and ATF6, in the liver were examined. The ultrastructure of the ER in the liver was examined by transmission electron microscopy. The expression levels of chemerin in the liver and the serum were also measured. After 4 weeks of liraglutide treatment, the BW, FBG, and FINS levels were significantly reduced, and the insulin sensitivity was increased compared with the HF only rats. Liraglutide reduced the expression of GRP78 and chemerin in liver tissue at both the mRNA and protein levels. Interestingly, the chemerin mRNA was closely correlated with the level of GRP78 mRNA, while the level of chemerin in serum was also associated with the FINS level. As a representative GLP-1 analog, liraglutide can suppress ER stress and reduce chemerin expression in the liver of rats exposed to a high-fat diet.

The predictive value of the first-trimester maternal serum chemerin level for pre-eclampsia

Chemerin is a novel adipokine linked to inflammation. The cross-sectional studies have reported that maternal chemerin serum concentrations are significantly increased in pre-eclampsia. However, limited data are available regarding the cause-effect relationship between chemerin and pre-eclampsia. The aim of this prospective observational study was to evaluate predictive significance of the first-trimester maternal serum chemerin levels for pre-eclampsia and to further confirm the hypothesis that chemerin is an important causative factor in the pathogenesis of pre-eclampsia. 518 pregnancy women were recruited. The first-trimester maternal serum chemerin levels were determined using enzyme-linked immunosorbent assay. The first-trimester maternal serum chemerin levels were statistically significantly elevated in women with pre-eclampsia compared with those without pre-eclampsia and in severe pre-eclampsia women compared with mild pre-eclampsia women. Serum chemerin levels remained positively associated with plasma C-reactive protein levels using a linear regression model. A logistic-regression analysis demonstrated that body mass index and serum chemerin levels appeared to be the independent predictors of pre-eclampsia. A receiver–operating characteristic curve analysis identified that serum chemerin levels predicted pre-eclampsia with high predictive value. The predictive value of the chemerin concentrations was similar to that of body mass index. Chemerin improved the predictive value of body mass index statistically significantly. Thus, our results suggest that high serum chemerin levels are associated with inflammation and pre-eclampsia independently, as well as chemerin may play a role as predictive biomarker for pre-eclampsia and be an important causative factor in the pathogenesis of pre-eclampsia.

Prognostic significance of plasma chemerin levels in patients with gastric cancer

Chemerin is a novel adipokine, which is linked to adipogenesis and chemotaxis of the innate immune system. This study aimed to evaluate the relationship between preoperative plasma chemerin level and prognosis of gastric cancers. One hundred ninety-six patients and 196 age- and gender-matched healthy individuals were recruited. Fasting venous blood samples were collected 2 days prior to surgery for the gastric cancer patients and at the physical examination day for the healthy volunteers. Recorded clinicopathological information included invasion depth, lymph node metastasis, distant metastasis, peritoneal dissemination, tumor size and tumor-node metastasis stage. Plasma chemerin levels were determined using enzyme-linked immunosorbent assay. Plasma chemerin levels were statistically significantly in all patients than in healthy controls (53.1 ± 19.0 ng/mL vs. 31.3 ± 11.3 ng/mL; P < 0.001). And it was identified as an independent predictor for 5-year mortality [odds ratio (OR), 2.718; 95% confidence interval (CI), 1.201-4.229; P = 0.005) and adverse event (OR, 2.982; 95% CI, 1.223-4.879; P = 0.003) of gastric cancer, and had high area under receiver operating characteristic curve (AUC) for prediction of 5-year mortality (AUC, 0.808; 95% CI, 0.745-0.860) and adverse event (AUC, 0.787; 95% CI, 0.723-0.842). It also emerged as an independent predictor for overall survival (Hazard ratios, 1.788; 95% CI, 1.200-2.663; P = 0.002) and disease-free survival (Hazard ratios, 2.016; 95% CI, 1.312-3.125; P = 0.004). Thus, our results suggest that high plasma chemerin levels are associated with long-term poor prognosis and survival of gastric cancer as well as may play a role as prognostic biomarker in gastric cancer survival.

Recently discovered adipokines and cardio-metabolic comorbidities in childhood obesity

White adipose tissue (WAT) asset, in terms of cell number, fat storage capacity and endocrine function, is largely determined in early stages of life and is pivotal for shaping the WAT pro-inflammatory behavior. WAT derived adipokines have been shown to play a main role in several cardio-metabolic abnormalities of obesity. This review focuses on the most recently identified adipokines, namely adipocyte-fatty acid-binding protein, chemerin, fibroblast growth factor-21, lipocalin-2, omentin-1 and vaspin; their role in the pathogenesis of obesity and associated cardio-metabolic abnormalities; and on their adaptive response to body weight change. Evidence consistently suggests a pathogenic role for A-FABP, chemerin and FGF-21. Nevertheless, large population studies are needed to verify whether they can be useful to predict the risk of cardio-metabolic abnormalities in adulthood and/or monitor the clinical response to therapeutic interventions.

Gpr1 is an active chemerin receptor influencing glucose homeostasis in obese mice

Chemerin is an adipose-derived signaling protein (adipokine) that regulates adipocyte differentiation and function, immune function, metabolism, and glucose homeostasis through activation of chemokine-like receptor 1 (CMKLR1). A second chemerin receptor, G protein-coupled receptor 1 (GPR1) in mammals, binds chemerin with an affinity similar to CMKLR1; however, the function of GPR1 in mammals is essentially unknown. Herein, we report that expression of murine Gpr1 mRNA is high in brown adipose tissue and white adipose tissue (WAT) and skeletal muscle. In contrast to chemerin (Rarres2) and Cmklr1, Gpr1 expression predominates in the non-adipocyte stromal vascular fraction of WAT. Heterozygous and homozygous Gpr1-knockout mice fed on a high-fat diet developed more severe glucose intolerance than WT mice despite having no difference in body weight, adiposity, or energy expenditure. Moreover, mice lacking Gpr1 exhibited reduced glucose-stimulated insulin levels and elevated glucose levels in a pyruvate tolerance test. This study is the first, to our knowledge, to report the effects of Gpr1 deficiency on adiposity, energy balance, and glucose homeostasis in vivo. Moreover, these novel results demonstrate that GPR1 is an active chemerin receptor that contributes to the regulation of glucose homeostasis during obesity.

Cardiovascular disease risk amongst African black patients with rheumatoid arthritis: the need for population specific stratification

Rheumatoid arthritis (RA) enhances the risk of cardiovascular disease to a similar extent as diabetes. Whereas atherogenesis remains poorly elucidated in RA, traditional and nontraditional risk factors associate similarly and additively with CVD in RA. Current recommendations on CVD risk stratification reportedly have important limitations. Further, reported data on CVD and its risk factors derive mostly from data obtained in the developed world. An earlier epidemiological health transition is intrinsic to persons living in rural areas and those undergoing urbanization. It is therefore conceivable that optimal CVD risk stratification differs amongst patients with RA from developing populations compared to those from developed populations. Herein, we briefly describe current CVD and its risk factor profiles in the African black population at large. Against this background, we review reported data on CVD risk and its potential stratification amongst African black compared to white patients with RA. Routinely assessed traditional and nontraditional CVD risk factors were consistently and independently related to atherosclerosis in African white but not black patients with RA. Circulating concentrations of novel CVD risk biomarkers including interleukin-6 and interleukin-5 adipokines were mostly similarly associated with both endothelial activation and atherosclerosis amongst African black and white RA patients.

Circulating concentrations of the novel adipokine chemerin are associated with cardiovascular disease risk in rheumatoid arthritis

OBJECTIVE

Depending on physiological context, the adipokine chemerin can reduce or enhance cardiovascular risk. We investigated whether chemerin concentrations represent cardiovascular disease risk in rheumatoid arthritis (RA).

METHODS

We assessed ELISA-determined chemerin concentrations and those of 4 early endothelial activation molecules as well as angiopoietin 2, which mediates angiogenesis and thereby contributes to advanced atherosclerosis, the common carotid artery intima-media thickness (cIMT), and carotid artery plaque by ultrasound in 236 patients (114 black and 122 white) with RA. Relationships were identified in potential confounder and mediator-adjusted mixed regression models.

RESULTS

Mean (SD) chemerin and median (interquartile range) angiopoietin 2 concentrations were 114 (35) ng/ml and 2560 (2044-3341) pg/ml, respectively; the mean (SD) cIMT was 0.708 (0.110) mm, and 40.3% of patients had plaque. Chemerin concentrations were not related to those of early endothelial activation molecules, but associated with those of angiopoietin 2 [β SE = 0.002 (0.0004), p < 0.0001] and plaque [OR 1.006 (95% CI 1.00-1.013), p = 0.05] in all patients. The presence of major conventional cardiovascular risk factors, generalized and abdominal obesity, and RA severity markers modified the independent chemerin-cardiovascular risk relations (interaction p < 0.05). Consequently, chemerin concentrations were associated with cIMT in those with but not without overweight or generalized obesity and abdominal obesity [β SE = 0.001 (0.0003), p = 0.005 and 0.001 (0.0001), p = 0.001 vs -0.001 (0.0004), p = 0.2 and -0.0002 (0.0004), p = 0.6, respectively], and with plaque in those without but not with generalized obesity [OR 1.008 (95% CI) 1.000-1.016, p = 0.03 vs 1.003 (0.990-1.017), p = 0.6, respectively]. The β (SE) for the chemerin-intima-media thickness relations in patients with overweight or generalized obesity and abdominal obesity were larger than in those without these characteristics (p < 0.0001 and = 0.04, respectively).

CONCLUSION

Chemerin is associated with endothelial activation and atherosclerosis in RA. Adiposity influences the chemerin-atherosclerotic phenotype relations in RA.

Impact of serum chemerin levels on liver functional reserves and platelet counts in patients with hepatocellular carcinoma

Obesity-related metabolic abnormalities, including adipokine imbalance and chronic inflammation, are involved in liver carcinogenesis. Chemerin, a novel adipokine, plays a critical role in adipogenesis, energy metabolism, and inflammation. We evaluated the impact of serum chemerin levels on liver functional reserves in hepatocellular carcinoma (HCC) patients and on the recurrence and prognosis of HCC. This study included 44 patients with any stage of HCC who underwent curative treatment at Gifu Municipal Hospital (Gifu, Japan) between 2006 and 2007. Recurrence-free survival and overall survival were estimated using the Kaplan-Meier method. Serum albumin levels (Pearson’s correlation coefficient; r = 0.3110, p = 0.0399), platelet counts (r = 0.4159, p = 0.0050), and prothrombin times (r = 0.3775, p = 0.0115) were significantly correlated with serum chemerin levels in patients with HCC, and they were inversely correlated with Child-Pugh scores (r = −0.3732, p = 0.0126), serum alanine aminotransferase levels (r = −0.3864, p = 0.0105), and total bilirubin levels (r = −0.4023, p = 0.0068). Among these variables, a multiple comparison test identified that platelet counts and total bilirubin levels were associated with serum chemerin levels (p < 0.0083). No significant correlation was found between serum chemerin levels and recurrence-free survival (p = 0.3691) or overall survival (p = 0.7916). In HCC patients, serum chemerin concentrations were correlated with liver functional reserves and platelet counts, but not with recurrence or prognosis.

Adiponectin and atherosclerosis in rheumatoid arthritis

In the present study, we examined the potential impact of adiponectin on carotid ultrasound determined atherosclerosis in 210 (119 black and 91 white) RA patients in mixed regression models. Total adiponectin concentrations were smaller in patients with compared to those without the metabolic syndrome (MetS) defined waist criterion (median (range) = 6.47 (1.23–34.54) versus 8.38 (0.82–85.30) ng/mL, P = 0.02, resp.); both total and high molecular weight (HMW) adiponectin concentrations were larger in patients with compared to those without joint deformities (7.97 (0.82–85.30) and 3.51 (0.01–35.40) versus 5.36 (1.29–19.49) and 2.34 (0.01–19.49) ng/mL, P = 0.003 and 0.02, resp.). Total and HMW adiponectin concentrations were associated with carotid artery plaque in patients with MetS waist (odds ratio (95% CI) = 0.87 (0.76–0.99) and 0.92 (0.85–0.99) per 1-standard deviation increment, P = 0.02 for both) and those without joint deformities (odds ratio (95% CI) = 0.94 (0.88–0.99) and 0.94 (0.89–0.99), P = 0.03 for both). Plaque prevalence was lower in patients without compared to those with joint deformities (23.4% versus 42.6, P = 0.004 in multivariable analysis). In RA patients with abdominal obesity or no clinically evident joint damage, adiponectin concentrations are reduced but nevertheless associated with decreased carotid atherosclerosis.

Irisin in patients with nonalcoholic fatty liver disease

OBJECTIVE

Irisin is a recently discovered myokine proposed to increase thermogenesis-related energy expenditure and improve metabolism. We aimed to comparatively evaluate serum irisin levels in patients with biopsy-proven nonalcoholic fatty liver disease (NAFLD) vs. controls and study their association with disease severity.

METHODS

Fifteen and 16 consecutively enrolled patients with biopsy-proven nonalcoholic simple steatosis (NAFL) and steatohepatitis (NASH), respectively, and 24 lean and 28 obese controls without NAFLD were recruited. Irisin, established adipokines and biochemical tests were measured.

RESULTS

Serum irisin levels were statistically different in obese controls (33.7±2.7 ng/mL; p<0.001) and patients with NAFL (30.5±1.5 ng/mL; p<0.001) and NASH (35.8±1.9 ng/mL; p=0.001) compared with lean controls (47.7±2.0 ng/mL), but were similar among patients with NAFL, NASH and obese controls. This difference remained significant after adjustment for body mass index (or waist circumference), gender, age, insulin resistance (assessed by HOMA-IR or QUICKI), exercise and time since blood collection. Serum leptin and adiponectin, but not irisin, levels were independently from BMI correlated with insulin resistance and cardiometabolic factors. Serum irisin tended to be higher in patients with (36.7±2.4 ng/mL) than without (30.8±1.2 ng/mL; p=0.02) portal inflammation and independently associated with the latter; these data need to be confirmed by future studies.

CONCLUSIONS

Serum irisin levels differ between lean controls and obese controls or NAFLD patients. Despite similar circulating irisin levels between NAFL and NASH groups, irisin may be independently and positively associated with the presence of portal inflammation. Future clinical and mechanistic studies are needed to confirm and extend these data.

Increased chemerin and decreased omentin-1 levels in morbidly obese patients are correlated with insulin resistance, oxidative stress and chronic inflammation

Background and aim

Morbid obesity represents a proinflammatory and pro-oxidative state associated with dysregulation of adipokines. We aimed to evaluate the circulating levels of chemerin and omentin-1 in morbidly obese (MO) patients and to investigate the relationship between these two adipokines and between each of them and anthropometric, metabolic, oxidative stress and chronic inflammatory parameters.

Material and methods

32 MO patients and 20 controls were investigated in this study. Anthropometric, metabolism parameters, inflammatory markers, oxidative stress indicators as well as chemerin and omentin-1 were measured.

Results

Serum levels of chemerin were increased while omentin-1 levels were decreased in MO patients when compared with controls. Chemerin correlated positively with insulin, HOMA-IR, LDL cholesterol and negatively with total antioxidant response. Omentin-1 correlated negatively with tumor necrosis factor alpha and total cholesterol. In a multiple linear stepwise regression analysis we learnt that only HOMA-IR (β=0.70, p<0.001), total cholesterol (β=0.42, p<0.001) and triglycerides (β=0.31, p<0.05) remained significantly associated with chemerin changes. Using the same analysis we noticed that total cholesterol (β=−0.71, p<0.001), fasting glucose (β= −0.40, p<0.05) and body mass index (BMI) (β= −0.38, p<0.05) were considered to be significant predictors for omentin-1 changes.

Conclusions

Chemerin and omentin-1 synthesis was dysregulated in MO patients. Chemerin might play a role in insulin resistance and oxidative stress. Chemerin changes seemed to be predicted mainly by insulin resistance. Omentin-1 levels were inversely associated with chronic inflammation and dyslipidemia while the main modulating factors seemed to be dyslipidemia, hyperglycemia and BMI.

Adiponectin, chemerin, cytokines, and dipeptidyl peptidase 4 are released from human adipose tissue in a depot-dependent manner: an in vitro system including human serum albumin

BACKGROUND

Adipose tissue (AT) contributes to metabolic dysfunction through imbalanced production of adipokines, including cytokines. Visceral AT in particular is associated with metabolic disorders, indicating a specific secretory status. The relative significance of different human AT depots in adipokine release is not fully known. Further, previous in vitro systems usually included medium containing bovine serum albumin (BSA), which may induce cytokine release. Our aim was to compare release of a number of adipokines/cytokines - all implicated in insulin resistance - from human subcutaneous and visceral AT in a short-term incubation system minimizing cytokine induction and including repeated measurements during 24 h. A prerequisite was to evaluate a potential alternative to BSA in the incubation medium.

METHODS

Subcutaneous and/or visceral AT from 17 patients (age 20-68 years; BMI 22.6-56.7 kg/m2) undergoing elective surgery was incubated for 2, 4, 6, 8, and 24 h in medium with or without 1% BSA or human serum albumin (HSA). Medium concentrations of adiponectin, chemerin, nine cytokines, dipeptidyl peptidase 4 (DPP4), and omentin were analyzed by multiplex immunoassay or ELISA. Adipocyte size, AT macrophage density, and medium concentrations of endotoxin were determined.

RESULTS

Cytokine release was induced by BSA but not by HSA. In evaluation of the final incubation protocol including 1% HSA, and as expected, adiponectin release was higher from subcutaneous biopsies of nonobese than of obese subjects and inversely associated with adipocyte size; omentin was released almost exclusively from visceral AT. Exploratory incubations revealed more abundant release of chemerin, cytokines (except IL-6), and DPP4 from the visceral depot, while adiponectin release was higher from subcutaneous than visceral AT. Release was linear for a maximum of 2-6 h. Macrophage density was higher in visceral than subcutaneous AT. Levels of endotoxin in the medium were negligible.

CONCLUSIONS

Adiponectin, chemerin, many cytokines, and DPP4 are released from human AT in a depot-dependent manner. These results highlight functional differences between visceral and subcutaneous AT, and a mechanistic link between regional fat accumulation and metabolic disorders. Supplementation of human AT incubation medium with HSA rather than BSA is recommended to minimize induction of cytokine release.

Circulating Adipokines in Healthy versus Unhealthy Overweight and Obese Subjects

It is now well established that not all obese subjects are at increased risk of cardiometabolic complications; such patients are termed the metabolically healthy obese. Despite their higher-than-normal body fat mass, they are still insulin sensitive, with a favorable inflammatory and lipid profile and no signs of hypertension. It remains unclear which factors determine an individual's metabolic health. Adipose tissue is known to secrete multiple bioactive substances, called adipokines, that can contribute to the development of obesity-associated complications. The goal of this study was to determine whether the circulating adipokine profiles differs between metabolically healthy and metabolically unhealthy overweight and obese subjects, thereby obtaining data that could help to explain the link between obesity and its related cardiometabolic complications. We defined metabolic health in terms of several metabolic and inflammatory risk factors. The serum adiponectin levels were higher in the healthy group and showed a positive correlation with HDL cholesterol levels in the unhealthy group. There were no differences between the two groups in the levels of serum leptin, chemerin and orosomucoid. Accordingly, adiponectin might play a role in protecting against obesity-associated cardiometabolic derangements. More studies are needed to clarify the role of different chemerin isoforms in this system.

Diabetes mellitus and inflammation

Type 2 diabetes mellitus (T2DM) is increasingly common worldwide. Related complications account for increased morbidity and mortality, and enormous healthcare spending. Knowledge of the pathophysiological derangements involved in the occurrence of diabetes and related complications is critical for successful prevention and control solutions. Epidemiologic studies have established an association between inflammatory biomarkers and the occurrence of T2DM and complications. Adipose tissue appears to be a major site of production of those inflammatory biomarkers, as a result of the cross-talk between adipose cells, macrophages, and other immune cells that infiltrate the expanding adipose tissue. The triggering mechanisms of the inflammation in T2DM are still ill-understood. Inflammatory response likely contributes to T2DM occurrence by causing insulin resistance, and is in turn intensified in the presence of hyperglycemia to promote long-term complications of diabetes. Targeting inflammatory pathways could possibly be a component of the strategies to prevent and control diabetes and related complications.