- Email: [email protected]
Chemerin levels as predictor of acute coronary events: A case–control study nested within the veterans affairs normative aging study
M ET ABOL I SM CL IN I CA L A N D E XP E RI ME N TAL 6 3 ( 2 0 14 ) 76 0–7 66
Available online at www.sciencedirect.com
Metabolism www.metabolismjournal.com
Chemerin levels as predictor of acute coronary events: A case–control study nested within the veterans affairs normative aging study☆ Konstantinos N. Aronis a, b, c,⁎, Ayse Sahin-Efe a, b , John P. Chamberland a, b , Avron Spiro III d , Pantel Vokonas e , Christos S. Mantzoros a, b, c a
Section of Endocrinology, VA Boston Healthcare System, Harvard Medical School Division of Endocrinology Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School c Department of Medicine, Boston Medical Center, Boston University School of Medicine d Normative Aging Study, VA Boston Healthcare System and Boston University Schools of Public Health and Medicine e Normative Aging Study, VA Boston Healthcare System and Boston University School of Medicine b
A R T I C LE I N FO Article history:
AB S T R A C T Objective. Chemerin is a recently identified adipocytokine that has been positively
Received 7 December 2013
correlated with the presence and severity of coronary artery disease (CAD). However, no
Accepted 18 February 2014
studies have examined circulating chemerin levels as a predictor of acute coronary syndrome (ACS). The purpose of this study is to evaluate whether chemerin levels predict
Keywords: Chemerin
the onset of ACS. Materials/Methods. We studied 90 men whose serum had been collected at least 2 years
Acute Coronary Events
before the development of ACS, and 162 controls matched with the cases in a 1:2 fashion for
Normative Aging Study
age and year of collection. The mean age of the cohort was 66.3 ± 9.6 years (range 34– 84 years). Serum chemerin levels were measured with a commercially available enzymelinked immunosorbent assay. Results. Age was positively associated with chemerin levels (r = 0.39, p < 0.001). Logistic regression analysis, adjusting for years since blood collection, demonstrated a null association between chemerin levels and the odds ratio for development of ACS (OR: 0.99, 95% CI [0.99–1.001]). This association remained null after adjusting for age (OR: 0.99 95% CI [0.99–1.001]). Conclusions. Although cross-sectional and case–control studies suggest a positive association between chemerin levels and CAD, we demonstrate that chemerin levels do not predict the development of ACS. © 2014 Elsevier Inc. All rights reserved.
Abbreviations: ACS, Acute Coronary Syndrome; BMI, Body Mass Index; CAD, Coronary Artery Disease; CMKLR1, Chemokine-like Receptor 1; CRP, Creactive protein; CT, Computerized Tomography; CV, Coefficient of Variation; HbA1C, A1 Glycosylated Hemoglobin; ICD8, International Classification of Diseases (8th version); OR, Odds Ratio; RARRES2, Retinoid Acid Receptor Responder 2; TIG2, Tazaroteneinduced Gene 2 protein; VA, Veteran’s Affairs; WHR, Waist to Hip Ratio. ☆ Institutions where work was performed: VA Boston Healthcare System, Jamaica Plain, MA, USA and Beth Israel Deaconess Medical Center, Boston, MA. ⁎ Corresponding author at: VA Boston Health Care System, 150 S Huntington Ave, Jamaica Plain, MA 02130-4817. Tel.: + 1 617 667 8630; fax: +1 617 667 8634. E-mail address: [email protected] (K.N. Aronis). http://dx.doi.org/10.1016/j.metabol.2014.02.013 0026-0495/© 2014 Elsevier Inc. All rights reserved.
M ET ABOL I SM CL IN I CA L A N D EX PE RI ME N TA L 6 3 ( 2 0 14 ) 76 0–7 6 6
1.
Introduction
Chemerin, also known as tazarotene-induced gene 2 protein (TIG2) or retinoid acid receptor responder 2 (RARRES2), is a recently identified adipose tissue secreted hormone that activates the chemokine-like receptor 1 (CMKLR-1) and has been traditionally thought to play a role in activation of the adaptive and innate immune systems, primarily based on data derived from in vitro studies [1,2]. CMKLR-1 is expressed on various cells of the innate and adaptive immune systems [3,4] and chemerin has been associated with pro-inflammation and particularly chemo-attraction of various cells of the immune system in vitro [2–6]. Interestingly, in humans CMKLR-1 is primarily expressed in metabolism-associated organs, such as the pancreas, liver, adrenal gland and the kidney [7], as well as in vascular endothelial cells that promote angiogenesis [8,9]. There is strong evidence that chemerin plays a major role in adipocyte differentiation, maturation and metabolism, and is associated with glucose homeostasis, insulin resistance and the metabolic syndrome [10–18]. Chemerin has been shown to be positively correlated with body mass index (BMI), insulin resistance, blood pressure, circulating triglycerides [12,19], as well as with other obesity-related markers such as leptin, resistin, C-reactive protein (CRP) and glycosylated hemoglobin (HbA1C) [20–22]. Chemerin is elevated in individuals with central obesity [23] and has been proposed as a potential link between obesity and development of type 2 diabetes [24]. Chemerin is also associated with the pro-inflammatory state present in patients with adverse metabolic phenotypes [25] and non-alcoholic steatohepatitis [26]. Maladaptation of the immune and inflammatory pathways [27] as well as metabolically obese status [28] has been proposed to be causally related with cardiovascular insulin resistance and disease. Weight loss leads to decreased chemerin expression by the adipose tissue and decreased circulating chemerin levels [29,30]. Furthermore, chemerin levels are inversely associated with exercise intensity [31]. There is increasing interest in the role of chemerin in cardiovascular disease and particularly in the development of atherosclerosis. Cross-sectional studies of human autopsy specimens have demonstrated that aortic and coronary atherosclerosis is positively correlated with chemerin expression in perivascular fat [32]. In cross-sectional studies, chemerin has been associated with peripheral arterial stiffness [33], as well as coronary plaque burden and the number of non-calcified plaques in patients with stable typical or atypical chest pain [34]. Case–control studies in patients with coronary artery disease (CAD) have demonstrated a positive association between circulating chemerin levels and CAD as well as with the severity of coronary lesions [35,36]. Chemerin mRNA expression in the epicardial adipose tissue is significantly higher in patients with CAD compared to non-CAD controls [37]. Although there is emerging evidence that chemerin could be associated with stable CAD, there are no studies to date evaluating the role of chemerin in acute coronary syndromes (ACS). The purpose of this study is to evaluate circulating chemerin levels as a predictor of ACS. We analyzed serum
761
samples from males with ACS (cases), matched for age and year of sample collection with healthy controls, and evaluated for potential associations between chemerin levels and the development of ACS. In addition, we measured and adjusted our results for circulating leptin and adiponectin levels, which constitute markers of energy stored in adipose tissue and insulin sensitivity respectively.
2.
Materials and methods
2.1.
Study design
In order to evaluate whether chemerin is associated with the development of ACS we performed a nested case–control study within the prospective VA Normative Aging Study. This is an ongoing longitudinal cohort study of aging that was established in 1963 [38]. Two thousand two hundred eighty healthy male volunteers, 21–84 years old, from the greater Boston (Massachusetts, USA) area were enrolled after an initial health screening, excluding subjects with chronic diseases. Subjects were reevaluated every 3 to 5 years using detailed questionnaires, on-site physical examinations and anthropometric measurements. Serum samples were collected at baseline and during the follow-up visits. These samples have been kept in − 30 °C freezers until the day of the analysis. For the purposes of our study we analyzed serum samples from 90 male participants collected at least 2, and no longer than 5 years, before the development of ACS. Serum was also analyzed in 162 non-ACS controls that had been matched for age and year of sample collection with the ACS cases in a 1:2 fashion. Serum samples were collected between 1965 and 2008. The mean age of our cohort was 66.3 ± 9.6 years (range 34–84 years). ACS was defined by ICD-8 code 410. Code 410 codes for acute myocardial infarction, including coronary artery embolism, occlusion, rupture or thrombosis, as well as infarction of heart myocardium or ventricular rupture. This study complies with the declaration of Helsinki and has been approved by the Human Studies Subcommittee of the Department of VA Medical Center and the Institutional Review Board of the Brigham and Women’s Hospital. All participants provided written informed consent.
2.2.
Biochemical measurements
Serum chemerin levels were measured with a commercially available enzyme-linked immunosorbent assay (Cat#: RD191136200R; Biovendor, Candler, NC) after extensive evaluation by our laboratory. The manufacturer’s reported sensitivity of 0.1 ng/mL, intra-assay coefficient of variation (CV) of 5.1%–7.0%, and inter-assay CV of 6 .9%–8.3% were confirmed in our laboratory and were determined to be acceptable for the differences that we wanted to detect. Serum leptin and adiponectin levels were measured using commercially available radio-immune-assays (Millipore Co. Billerica, MA) with sensitivities 0.437 ng/mL and 0.9375 ng/mL, intra-assay CV: 3.4%–8.3% and 1.78%–3.59%, and inter-assay CV: 3.0%–6.2% and 6.90%–9.25%, accordingly. The assays were performed in batches of one case followed by two control samples.
762 2.3.
M ET ABOL I SM CL IN I CA L A N D E XP E RI ME N TAL 6 3 ( 2 0 14 ) 76 0–7 66
Power considerations
Table 1 – Baseline characteristics between cases and controls. Variable
Studies in stable CAD have demonstrated that the odds ratio of CAD for the highest chemerin quartile compared with the lowest one was 1.87 (95% CI: 1.07–3.24) [35]. No other study to date has evaluated the effect of chemerin levels on ACS so we do not have any direct estimate of the potential effect size of chemerin levels as predictor of ACS. We calculated that 252 subjects would ensure 80% power and <5% probability to commit type I error (two sided) in detecting an odds ratio of 1.9 for each standard deviation increase in chemerin levels, which we consider clinically relevant.
2.4.
Statistical analysis
Statistical analysis was performed using Stata v.12 (StataCorp, College Station, TX). Continuous variables are summarized as mean ± standard error of the mean and categorical variables as percentages. Normality of the distributions was evaluated with frequency histograms and the Shapiro–Wilk statistic. Skewed variables were analyzed after logarithmic or square root transformation as indicated by the degree of skewness. Comparisons between cases and controls were performed with student’s t-test (continuous variables) and Pearson’s chisquared (categorical variables). Pearson’s partial correlation coefficient analysis was performed to evaluate for baseline correlations between different variables, adjusting for the year of the sample collection. Linear regression analysis was performed on all measured hormones and the year of sample collection to evaluate for potential time-dependent degradation. Unconditional logistic regression analysis was performed to evaluate the effects of circulating chemerin levels on the odds ratio of ACS development. Findings were secondarily confirmed using conditional logistic regression analysis. All p-values are two-sided and the alpha criterion was set at 0.05.
3.
Results
3.1.
Baseline characteristics (Tables 1 and 2)
The average age of cases and controls was 67.25 ± 9.11 and 65.85 ± 9.84 years respectively (p = 0.27). Serum samples were collected on average 18.7 ± 8.5 years prior to the analysis day in cases vs. controls (17.9 ± 8.0 vs. 19.2 ± 8.8 years, p = 0.26). Cases had on average slightly higher BMIs compared to controls (27.86 ± 3.43 vs. 26.70 ± 3.73 kg/m2, p = 0.025). Waist to hip ratio (WHR), chemerin, adiponectin and leptin levels were similar between cases and controls. The percent of subjects who smoked or had exercise intolerance even at minimal exercise was the same between cases and controls (Table 1). Chemerin levels were inversely associated with height (r = − 0.17 for cases and controls, p < 0.05) and positively associated with WHR (0.28 for controls, 0.19 for cases and controls, p < 0.05). Interestingly, chemerin levels were not correlated with weight or BMI. Chemerin levels were the same between smokers and non-smokers (181.6 ± 115.5 vs. 184.4 ± 124.6 ng/mL, p = 0.93). Chemerin levels were positively asso-
Age (years) Height (m) Weight (kg) BMI (kg/m2) WHR Chemerin (ng/mL) Adiponectin (ng/mL) Leptin (ng/mL) Smoker (yes, no) Exercise intolerance even on mild exercise (yes, no)
Cases (n = 90)
Controls (n = 162)
p-value
67.25 ± 9.11 1.75 ± 0.07 85.60 ± 13.28 27.86 ± 3.43 0.98 ± 0.049 178.24 ± 116.51 13.04 ± 8.65 9.37 ± 9.44 8 (5.81%) 17 (19.77)
65.85 ± 9.84 1.74 ± 0.06 81.59 ± 13.60 26.70 ± 3.73 0.98 ± 0.06 183.02 ± 115.53 12.76 ± 7.19 8.50 ± 10.32 5 (5.13%) 32 (20.51)
0.27 0.46 0.03 0.02 0.63 0.75 0.96 0.62 0.78 0.99
Data are shown as mean ± standard deviation for the continuous variables and N (%) for the categorical variables. BMI: body mass index, WHR: waist to hip ratio.
ciated with the year of the sample collection (b = 5.57, p < 0.001) demonstrating slow time-dependent degradation of the molecule after long term storage at − 30 °C. Similar degradation was also observed in adiponectin and leptin levels (b = 0.17, and b = 0.49 accordingly, p < 0.001).
3.2.
Chemerin as a predictor of ACS (Tables 3 and 4)
Logistic regression analysis, adjusting for the year that the sample was collected, demonstrated no association between chemerin levels and the development of ACS (OR: 0.99, 95% CI [0.99–1.001]). This association remained null after adjusting for age, BMI, WHR, circulating leptin and adiponectin levels in sequential logistic regression models (Table 3). Further analysis of the ACS OR across the different tertiles of chemerin levels failed to demonstrate any association between circulating chemerin levels and ACS development, even in the highest chemerin tertile (Table 4). Similar results were obtained using conditional regression analysis and after grouping the 2nd and 3rd tertile of chemerin levels and comparing it against the lowest one (OR: 0.83, 95% CI: [0.26– 2.08] unadjusted model; OR 0.73, 95% CI: [0.25–2.08] fully adjusted model). No other variables in the above models were independent predictors of ACS risk.
4.
Discussion
Adipose tissue, once thought to have a role primarily in energy storage, is now known to be a metabolically active endocrine organ, secreting hormones known as adipocytokines [39–41]. There is growing evidence that these adipocytokines may be a link between obesity and cardiovascular disease [42–46]. Chemerin has been recently identified as an adipocytokine with pro-inflammatory action that has been positively correlated with coronary atherosclerotic plaque burden and arterial stiffness in cross-sectional studies [32–34]. Recent case–control studies suggest that there is a positive association between the presence and severity of CAD, and circulating
763
M ET ABOL I SM CL IN I CA L A N D EX PE RI ME N TA L 6 3 ( 2 0 14 ) 76 0–7 6 6
Table 2 – Pearson’s partial coefficients between continuous variables, adjusting for the year of sample collection.
Age (years) Height (m) Weight (kg) BMI (kg/m2) WHR Chemerin (ng/mL) Adiponectin (ng/mL) Leptin (nl/mL)
Age
Height
Weight
BMI
WHR
Chemerin
Adiponectin
Leptin
1 −0.20 ⁎ −0.21 ⁎ −0.14 ⁎ 0.01 0.10 0.10 <0.01
−0.20 ⁎ 1 0.55 ⁎ 0.08 −0.02 −0.17 ⁎ 0.03 −0.06
−0.21 ⁎ 0.50 ⁎ 1 0.88 ⁎ 0.34 ⁎ <0.01 0.02 0.31 ⁎
−0.14 ⁎ 0.05 0.89 ⁎ 1 0.41 ⁎ 0.10 −0.02 0.41 ⁎
0.01 −0.03 0.31 ⁎ 0.35 ⁎ 1 0.19 ⁎ −0.13 0.33 ⁎
0.10 −0.10 0.05 0.10 0.28 ⁎ 1 0.17 ⁎ 0.63 ⁎
0.10 −0.01 0.05 −0.01 −0.13 0.15 1 0.16 ⁎
0.01 −0.01 0.37 ⁎ 0.41 ⁎ 0.34 ⁎ 0.61 ⁎ 0.17 ⁎ 1
Lower half represents correlations in pooled cases and controls, upper half represents correlations in controls only. BMI: body mass index, WHR: waist to hip ratio. ⁎ p value < 0.05.
chemerin levels [35,36]. However, there are no studies to date evaluating circulating chemerin levels as a predictor of ACS. To the best of our knowledge, this is the first study to demonstrate that chemerin levels are not associated with the development of ACS. We demonstrated that the mean levels of chemerin, collected at least 2 years before the development of ACS, are similar between ACS cases and controls. In addition, logistic regression analysis demonstrates that circulating chemerin levels could not predict the development of ACS. The latter remained true even after analyzing the data in tertiles and after adjusting for potential confounding variables. The results of our study are novel and there is no other study to date evaluating for potential associations between chemerin levels and the development of ACS. Most studies to date are in agreement that chemerin levels are positively associated with atherosclerosis and stable CAD. In a study of 430 subjects that underwent coronary angiography CAD was positively associated with increasing serum chemerin levels and this association remained significant after adjusting for age, gender, and other established risk factors for CAD [35]. A positive association between chemerin levels and CAD is also reported in a more recent study of smaller sample size by Xiaotao et al. [47]. Elevated serum chemerin levels were also found to be an independent predictor of the presence of CAD in a study of 112 patients with the metabolic syndrome [36], as
Table 3 – Logistic regression models calculating the odds ratio of ACS development for one standard deviation change in chemerin circulating levels, adjusting for potential confounders. Variables included in the model Chemerin, year Chemerin, year, age Chemerin, year, age, BMI Chemerin, year, age, WHR Chemerin, year, age, BMI, WHR Chemerin, year, age, leptin Chemerin, year, age, adiponectin Chemerin, year, age, BMI, WHR, leptin, adiponectin
Odds Ratio (95% CI) 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99
(0.99–1.001) (0.99–1.001) (0.99–1.001) (0.99–1.002) (0.99–1.002) (0.99–1.001) (0.99–1.001) (0.99–1.002)
p-value 0.37 0.35 0.19 0.39 0.38 0.19 0.39 0.42
Year: means year of sample collection. 95% CI is the 95% confidence interval of the odds ratio. BMI: body mass index, WHR: waist to hip ratio.
well as a different study of 286 patients with type 2 diabetes [48]. Interestingly, Lehrke et al. in a cross-sectional study of 303 patients with stable typical or atypical chest pain who underwent dual-source multi-slice CT-angiography, demonstrated that chemerin levels were positively correlated with coronary plaque burden and the number of non-calcified plaques [34]. Conversely, Hah et al. in a study of 131 patients with known CAD demonstrated that although chemerin levels were positively correlated with fasting glucose, triglyceride, total cholesterol, low density lipoprotein cholesterol, and high sensitive C-reactive protein levels, they failed to be an independent risk factor of multiple vessel disease in multivariate analysis models [49]. The only in vivo study available to date evaluating the effects of chemerin in CAD has demonstrated that adenoviral-mediated chemerin overexpression in an LDL receptor knockout, high-fat diet mice model had no effect on weight, lipid levels, or extent of atherosclerosis [50]. Given the associations between chemerin and CAD in humans we suggest that rodent models, such as the ones utilized in the study above, might not be the optimal animal model for reverse translational research and the role of chemerin in
Table 4 – Logistic regression models calculating the odds ratio of ACS development across different chemerin tertiles, adjusting for potential confounders. Variables included in the model Chemerin, year
Chemerin, year, age
Chemerin, year, age, BMI
Chemerin, year, age, WHR
Chemerin, year, age, BMI, WHR
Odds Ratio (95% CI) 1st tertile 1 2nd tertile 0.63 (0.32–1.22) 3rd tertile 0.83 (0.42–1.64) 1st tertile 1 2nd tertile 0.62 (0.32–1.21) 3rd tertile 0.83 (0.42–1.63) 1st tertile 1 2nd tertile 0.63 (0.32–1.23) 3rd tertile 0.74 (0.37–1.49) 1st tertile 1 2nd tertile 0.86 (0.27–2.72) 3rd tertile 0.67 (0.22–2.05) 1st tertile 1 2nd tertile 0.81 (0.25–2.64) 3rd tertile 0.66 (0.22–2.00)
p-value
0.17 0.60 0.16 0.58 0.18 0.40 0.80 0.48 0.73 0.46
Year: means year of sample collection. 95% CI is the 95% confidence interval of the odds ratio. BMI: body mass index, WHR: waist to hip ratio.
764
M ET ABOL I SM CL IN I CA L A N D E XP E RI ME N TAL 6 3 ( 2 0 14 ) 76 0–7 66
atherosclerosis should be evaluated in other in vivo animal models as well. Furthermore, there is some evidence, mainly from crosssectional studies, that chemerin has a role in cardiovascular biology, in addition to coronary atherosclerosis. A recent study demonstrated that the degree of aortic atherosclerosis was positively correlated with chemerin expression in the periaortic and pericoronary fat [32]. Gao et al. compared chemerin mRNA expression in epicardial fat tissue from patients with and without CAD, demonstrating that chemerin mRNA expression in epicardial fat is positively associated with the presence and severity of CAD. These associations remained statistically significant even after adjustment for age, gender, BMI and waist circumference [37]. A different study demonstrated that there is a positive association between chemerin levels and arterial stiffness, as evaluated by brachial artery pulse-wave velocity [33]. One of the strengths of our study is that this is the first study to evaluate the associations between circulating chemerin levels and ACS, utilizing a state-of-the-art assay. We analyzed samples under code and assays were performed by experienced personnel who were not aware of the hypothesis of the study. In addition, our subjects were matched to controls for age, eliminating it as a potential confounder. Our subject population spans all age groups and has been collected over the last 50 years providing durability in the interpretation of our results. Chemerin levels do not exhibit any day–night variation and thus its levels are not affected by the time of sample collection [7]. One limitation of our study is the slow time-dependent degradation of chemerin, resulting from the long-term storage of the samples in − 30 °C. However, cases and controls were matched for the year of sample collection and we also analytically adjusted for this, eliminating any potential bias introduced by the long-term storage. In addition, although normative chemerin levels have not been established in the literature, the chemerin levels that we report in our study are similar to the ones observed in different studies [16,51,52]. The subjects analyzed herein were only male veterans and consequently comparisons across genders could not be performed. Furthermore, these results cannot necessarily be generalized to the general population. However, there are no data in the current literature suggesting a potential effect modification of chemerin’s associations by gender. Lastly, we measured chemerin levels at least 2 years prior to the ACS event. Whether chemerin levels at a time closer to the event could predict ACS needs to be examined in future studies. To summarize, this is the first study to date demonstrating that circulating chemerin levels are not associated with the development of ACS. Although some evidence exist that chemerin might have some deleterious effects on vascular homeostasis and could be associated with the development of coronary atherosclerosis, prospective studies demonstrating a causal association between chemerin levels and the development of stable or unstable CAD are completely lacking. Prospective studies evaluating the incidence of stable CAD and ACS in high-risk individuals across different chemerin baseline levels are encouraged. In addition, basic science studies evaluating for the mechanistic role of chemerin in the process of atherosclerosis development, plaque formation,
plaque rupture and thrombus formation are also lacking and are strongly encouraged. Future basic and translational research investigating the role of chemerin in the area of atherosclerosis development, rather than plaque stability, is warranted since chemerin seems to be associated with stable CAD rather than ACS.
Funding The Mantzoros Laboratory is supported by the Award Number 1I01CX000422-01A1 from the Clinical Science Research and Development Service of the VA Office of Research and Development. NAS is supported by Cooperative Studies Program/ERIC, US Department of Veterans Affairs and is a research component of the Massachusetts Veterans Epidemiology Research and Information Center. Dr. Spiro is supported by a Research Career Scientist award from the Clinical Science Research and Development Service, US Department of Veterans’ Affairs.
Acknowledgments KNA designed the study, performed biochemical analysis, performed the statistical analysis and wrote the manuscript. JPC performed biochemical analysis and contributed to data and sample collection. ASE coordinated the study performed biochemical analysis and contributed to data and sample collection. AS-III contributed in the statistical analysis. PV is the director of the VA Normative Ageing Study and oversaw the study cohort data collection and contributed to the manuscript writing. CSM designed the study, oversaw the entire study and the manuscript writing.
Conflict of interest The authors have no conflicts of interest and have nothing to disclose.
REFERENCES
[1] Meder W, Wendland M, Busmann A, et al. Characterization of human circulating TIG2 as a ligand for the orphan receptor ChemR23. FEBS Lett 2003;555:495–9. [2] Ernst MC, Sinal CJ. Chemerin: at the crossroads of inflammation and obesity. Trends Endocrinol Metab 2010;21:660–7. [3] Wittamer V, Franssen JD, Vulcano M, et al. Specific recruitment of antigen-presenting cells by chemerin, a novel processed ligand from human inflammatory fluids. J Exp Med 2003;198:977–85. [4] Wittamer V, Bondue B, Guillabert A, et al. Neutrophil-mediated maturation of chemerin: a link between innate and adaptive immunity. J Immunol 2005;175:487–93. [5] Nagpal S, Patel S, Jacobe H, et al. Tazarotene-induced gene 2 (TIG2), a novel retinoid-responsive gene in skin. J Invest Dermatol 1997;109:91–5. [6] Polyzos SA, Kountouras J, Anastasilakis AD, et al. Irisin in patients with nonalcoholic fatty liver disease. Metabolism 2014;63:207–17.
M ET ABOL I SM CL IN I CA L A N D EX PE RI ME N TA L 6 3 ( 2 0 14 ) 76 0–7 6 6
[7] Chamberland JP, Berman RL, Aronis KN, et al. Chemerin is expressed mainly in pancreas and liver, is regulated by energy deprivation, and lacks day/night variation in humans. Eur J Endocrinol 2013;169:453–62. [8] Bozaoglu K, Curran JE, Stocker CJ, et al. Chemerin, a novel adipokine in the regulation of angiogenesis. J Clin Endocrinol Metab 2010;95:2476–85. [9] Kaur J, Adya R, Tan BK, et al. Identification of chemerin receptor (ChemR23) in human endothelial cells: chemerin-induced endothelial angiogenesis. Biochem Biophys Res Commun 2010;391:1762–8. [10] Goralski KB, McCarthy TC, Hanniman EA, et al. Chemerin, a novel adipokine that regulates adipogenesis and adipocyte metabolism. J Biol Chem 2007;282:28175–88. [11] Roh SG, Song SH, Choi KC, et al. Chemerin—a new adipokine that modulates adipogenesis via its own receptor. Biochem Biophys Res Commun 2007;362:1013–8. [12] Bozaoglu K, Bolton K, McMillan J, et al. Chemerin is a novel adipokine associated with obesity and metabolic syndrome. Endocrinology 2007;148:4687–94. [13] Takahashi M, Takahashi Y, Takahashi K, et al. Chemerin enhances insulin signaling and potentiates insulinstimulated glucose uptake in 3 T3-L1 adipocytes. FEBS Lett 2008;582:573–8. [14] Mussig K, Staiger H, Machicao F, et al. RARRES2, encoding the novel adipokine chemerin, is a genetic determinant of disproportionate regional body fat distribution: a comparative magnetic resonance imaging study. Metabolism 2009;58:519–24. [15] Syed Ikmal SI, Zaman Huri H, Vethakkan SR, et al. Potential biomarkers of insulin resistance and atherosclerosis in type 2 diabetes mellitus patients with coronary artery disease. Int J Endocrinol 2013;2013:698567. [16] Jialal I, Devaraj S, Kaur H, et al. Increased chemerin and decreased omentin-1 in both adipose tissue and plasma in nascent metabolic syndrome. J Clin Endocrinol Metab 2013;98:E514–7. [17] Guzel EC, Celik C, Abali R, et al. Omentin and chemerin and their association with obesity in women with polycystic ovary syndrome. Gynecol Endocrinol 2014. http://dx.doi.org/ 10.3109/09513590.2014.888412 [Epub ahead of print]. [18] Wang D, Yuan GY, Wang XZ, et al. Plasma chemerin level in metabolic syndrome. Genet Mol Res 2013;12:5986–91. [19] Bozaoglu K, Segal D, Shields KA, et al. Chemerin is associated with metabolic syndrome phenotypes in a Mexican–American population. J Clin Endocrinol Metab 2009;94:3085–8. [20] Weigert J, Neumeier M, Wanninger J, et al. Systemic chemerin is related to inflammation rather than obesity in type 2 diabetes. Clin Endocrinol (Oxf) 2010;72:342–8. [21] Sell H, Divoux A, Poitou C, et al. Chemerin correlates with markers for fatty liver in morbidly obese patients and strongly decreases after weight loss induced by bariatric surgery. J Clin Endocrinol Metab 2010;95:2892–6. [22] Tonjes A, Fasshauer M, Kratzsch J, et al. Adipokine pattern in subjects with impaired fasting glucose and impaired glucose tolerance in comparison to normal glucose tolerance and diabetes. PLoS One 2010;9(1–6):e13911. http://dx.doi.org/ 10.1371/journal.pone.0013911. [23] Chen HY, Lin CC, Chiu YL, et al. Serum fetuin a and chemerin levels correlate with hepatic steatosis and regional adiposity in maintenance hemodialysis patients. PLoS One 2012;7(1–9):e38514. http://dx.doi.org/10.1371/ journal.pone.0038415. [24] Roman AA, Parlee SD, Sinal CJ. Chemerin: a potential endocrine link between obesity and type 2 diabetes. Endocrine 2012;42:243–51. [25] Gu P, Jiang W, Lu B, et al. Chemerin is associated with inflammatory markers and metabolic syndrome phenotypes
[26]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
[39] [40]
[41]
[42]
[43]
[44]
[45]
765
in hypertension patients. Clin Exp Hypertens 2013. http://dx. doi.org/10.3109/10641963.2013.827697 [Epub ahead of print]. Docke S, Lock JF, Birkenfeld AL, et al. Elevated hepatic chemerin mRNA expression in human non-alcoholic fatty liver disease. Eur J Endocrinol 2013;169:547–57. Aroor AR, McKarns S, Demarco VG, et al. Maladaptive immune and inflammatory pathways lead to cardiovascular insulin resistance. Metabolism 2013;62:1543–52. Kwon BJ, Kim DW, Her SH, et al. Metabolically obese status with normal weight is associated with both the prevalence and severity of angiographic coronary artery disease. Metabolism 2013;62:952–60. Chakaroun R, Raschpichler M, Kloting N, et al. Effects of weight loss and exercise on chemerin serum concentrations and adipose tissue expression in human obesity. Metabolism 2012;61:706–14. Terra X, Auguet T, Guiu-Jurado E, et al. Long-term changes in leptin, chemerin and ghrelin levels following different bariatric surgery procedures: Roux-en-Y gastric bypass and sleeve gastrectomy. Obes Surg 2013;23:1790–8. Polyzos SA, Kountouras J, Anastasilakis AD, et al. Irisin in patients with nonalcoholic fatty liver disease. Metabolism 2014;63(2):207–17. Spiroglou SG, Kostopoulos CG, Varakis JN, et al. Adipokines in periaortic and epicardial adipose tissue: differential expression and relation to atherosclerosis. J Atheroscler Thromb 2010;17:115–30. Yoo HJ, Choi HY, Yang SJ, et al. Circulating chemerin level is independently correlated with arterial stiffness. J Atheroscler Thromb 2012;19:59–68. Lehrke M, Becker A, Greif M, et al. Chemerin is associated with markers of inflammation and components of the metabolic syndrome but does not predict coronary atherosclerosis. Eur J Endocrinol 2009;161:339–44. Yan Q, Zhang Y, Hong J, et al. The association of serum chemerin level with risk of coronary artery disease in Chinese adults. Endocrine 2011;41:281–8. Dong B, Ji W, Zhang Y. Elevated serum chemerin levels are associated with the presence of coronary artery disease in patients with metabolic syndrome. Intern Med 2011;50:1093–7. Gao X, Mi S, Zhang F, et al. Association of chemerin mRNA expression in human epicardial adipose tissue with coronary atherosclerosis. Cardiovasc Diabetol 2011;10:87. Bell B, Rose CL, Damon A. The Veterans Administration longitudinal study of healthy aging. Gerontologist 1966;6:179–84. Sahin-Efe A, Katsikeris F, Mantzoros CS. Advances in adipokines. Metabolism 2012;61:1659–65. Ko BJ, Park KH, Mantzoros CS. Diet patterns, adipokines, and metabolism: where are we and what is next? Metabolism 2014;63:168–77. El-Mesallamy HO, Kassem DH, El-Demerdash E, et al. Vaspin and visfatin/Nampt are interesting interrelated adipokines playing a role in the pathogenesis of type 2 diabetes mellitus. Metabolism 2011;60:63–70. Van de Voorde J, Pauwels B, Boydens C, et al. Adipocytokines in relation to cardiovascular disease. Metabolism 2013;62:1513–21. Li Q, Lu Y, Sun L, et al. Plasma adiponectin levels in relation to prognosis in patients with angiographic coronary artery disease. Metabolism 1803–1808;2012:61. Giannessi D, Caselli C, Del Ry S, et al. Adiponectin is associated with abnormal lipid profile and coronary microvascular dysfunction in patients with dilated cardiomyopathy without overt heart failure. Metabolism 2011;60:227–33. Hirata A, Kishida K, Nakatsuji H, et al. High serum C1q-adiponectin/total adiponectin ratio correlates with coronary artery disease in Japanese type 2 diabetics. Metabolism 2013;62:578–85.
766
M ET ABOL I SM CL IN I CA L A N D E XP E RI ME N TAL 6 3 ( 2 0 14 ) 76 0–7 66
[46] Piestrzeniewicz K, Luczak K, Komorowski J, et al. Resistin increases with obesity and atherosclerotic risk factors in patients with myocardial infarction. Metabolism 2008;57:488–93. [47] Xiaotao L, Xiaoxia Z, Yue X, et al. Serum chemerin levels are associated with the presence and extent of coronary artery disease. Coron Artery Dis 2012;23:412–6. [48] Lin X, Tang X, Jiang Q, et al. Elevated serum chemerin levels are associated with the presence of coronary artery disease in patients with type 2 diabetes. Clin Lab 2012;58:539–44. [49] Hah YJ, Kim NK, Kim MK, et al. Relationship between chemerin levels and cardiometabolic parameters and degree of coronary stenosis in Korean patients with coronary artery disease. Diabetes Metab J 2011;35:248–54.
[50] Becker M, Rabe K, Lebherz C, et al. Expression of human chemerin induces insulin resistance in the skeletal muscle but does not affect weight, lipid levels, and atherosclerosis in LDL receptor knockout mice on high-fat diet. Diabetes 2010;59:2898–903. [51] Gisondi P, Lora V, Bonauguri C, et al. Serum chemerin is increased in patients with chronic plaque psoriasis and normalizes following treatment with infliximab. Br J Dermatol 2013;168:749–55. [52] Kim SH, Lee SH, Ahn KY, et al. Effect of lifestyle modification on serum chemerin concentration and its association with insulin sensitivity in overweight and obese adults with type 2 diabetes. Clin Endocrinol (Oxf) 2013. http://dx.doi.org/10.1111/ cen.12249.
Available online at www.sciencedirect.com
Metabolism www.metabolismjournal.com
Chemerin levels as predictor of acute coronary events: A case–control study nested within the veterans affairs normative aging study☆ Konstantinos N. Aronis a, b, c,⁎, Ayse Sahin-Efe a, b , John P. Chamberland a, b , Avron Spiro III d , Pantel Vokonas e , Christos S. Mantzoros a, b, c a
Section of Endocrinology, VA Boston Healthcare System, Harvard Medical School Division of Endocrinology Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School c Department of Medicine, Boston Medical Center, Boston University School of Medicine d Normative Aging Study, VA Boston Healthcare System and Boston University Schools of Public Health and Medicine e Normative Aging Study, VA Boston Healthcare System and Boston University School of Medicine b
A R T I C LE I N FO Article history:
AB S T R A C T Objective. Chemerin is a recently identified adipocytokine that has been positively
Received 7 December 2013
correlated with the presence and severity of coronary artery disease (CAD). However, no
Accepted 18 February 2014
studies have examined circulating chemerin levels as a predictor of acute coronary syndrome (ACS). The purpose of this study is to evaluate whether chemerin levels predict
Keywords: Chemerin
the onset of ACS. Materials/Methods. We studied 90 men whose serum had been collected at least 2 years
Acute Coronary Events
before the development of ACS, and 162 controls matched with the cases in a 1:2 fashion for
Normative Aging Study
age and year of collection. The mean age of the cohort was 66.3 ± 9.6 years (range 34– 84 years). Serum chemerin levels were measured with a commercially available enzymelinked immunosorbent assay. Results. Age was positively associated with chemerin levels (r = 0.39, p < 0.001). Logistic regression analysis, adjusting for years since blood collection, demonstrated a null association between chemerin levels and the odds ratio for development of ACS (OR: 0.99, 95% CI [0.99–1.001]). This association remained null after adjusting for age (OR: 0.99 95% CI [0.99–1.001]). Conclusions. Although cross-sectional and case–control studies suggest a positive association between chemerin levels and CAD, we demonstrate that chemerin levels do not predict the development of ACS. © 2014 Elsevier Inc. All rights reserved.
Abbreviations: ACS, Acute Coronary Syndrome; BMI, Body Mass Index; CAD, Coronary Artery Disease; CMKLR1, Chemokine-like Receptor 1; CRP, Creactive protein; CT, Computerized Tomography; CV, Coefficient of Variation; HbA1C, A1 Glycosylated Hemoglobin; ICD8, International Classification of Diseases (8th version); OR, Odds Ratio; RARRES2, Retinoid Acid Receptor Responder 2; TIG2, Tazaroteneinduced Gene 2 protein; VA, Veteran’s Affairs; WHR, Waist to Hip Ratio. ☆ Institutions where work was performed: VA Boston Healthcare System, Jamaica Plain, MA, USA and Beth Israel Deaconess Medical Center, Boston, MA. ⁎ Corresponding author at: VA Boston Health Care System, 150 S Huntington Ave, Jamaica Plain, MA 02130-4817. Tel.: + 1 617 667 8630; fax: +1 617 667 8634. E-mail address: [email protected] (K.N. Aronis). http://dx.doi.org/10.1016/j.metabol.2014.02.013 0026-0495/© 2014 Elsevier Inc. All rights reserved.
M ET ABOL I SM CL IN I CA L A N D EX PE RI ME N TA L 6 3 ( 2 0 14 ) 76 0–7 6 6
1.
Introduction
Chemerin, also known as tazarotene-induced gene 2 protein (TIG2) or retinoid acid receptor responder 2 (RARRES2), is a recently identified adipose tissue secreted hormone that activates the chemokine-like receptor 1 (CMKLR-1) and has been traditionally thought to play a role in activation of the adaptive and innate immune systems, primarily based on data derived from in vitro studies [1,2]. CMKLR-1 is expressed on various cells of the innate and adaptive immune systems [3,4] and chemerin has been associated with pro-inflammation and particularly chemo-attraction of various cells of the immune system in vitro [2–6]. Interestingly, in humans CMKLR-1 is primarily expressed in metabolism-associated organs, such as the pancreas, liver, adrenal gland and the kidney [7], as well as in vascular endothelial cells that promote angiogenesis [8,9]. There is strong evidence that chemerin plays a major role in adipocyte differentiation, maturation and metabolism, and is associated with glucose homeostasis, insulin resistance and the metabolic syndrome [10–18]. Chemerin has been shown to be positively correlated with body mass index (BMI), insulin resistance, blood pressure, circulating triglycerides [12,19], as well as with other obesity-related markers such as leptin, resistin, C-reactive protein (CRP) and glycosylated hemoglobin (HbA1C) [20–22]. Chemerin is elevated in individuals with central obesity [23] and has been proposed as a potential link between obesity and development of type 2 diabetes [24]. Chemerin is also associated with the pro-inflammatory state present in patients with adverse metabolic phenotypes [25] and non-alcoholic steatohepatitis [26]. Maladaptation of the immune and inflammatory pathways [27] as well as metabolically obese status [28] has been proposed to be causally related with cardiovascular insulin resistance and disease. Weight loss leads to decreased chemerin expression by the adipose tissue and decreased circulating chemerin levels [29,30]. Furthermore, chemerin levels are inversely associated with exercise intensity [31]. There is increasing interest in the role of chemerin in cardiovascular disease and particularly in the development of atherosclerosis. Cross-sectional studies of human autopsy specimens have demonstrated that aortic and coronary atherosclerosis is positively correlated with chemerin expression in perivascular fat [32]. In cross-sectional studies, chemerin has been associated with peripheral arterial stiffness [33], as well as coronary plaque burden and the number of non-calcified plaques in patients with stable typical or atypical chest pain [34]. Case–control studies in patients with coronary artery disease (CAD) have demonstrated a positive association between circulating chemerin levels and CAD as well as with the severity of coronary lesions [35,36]. Chemerin mRNA expression in the epicardial adipose tissue is significantly higher in patients with CAD compared to non-CAD controls [37]. Although there is emerging evidence that chemerin could be associated with stable CAD, there are no studies to date evaluating the role of chemerin in acute coronary syndromes (ACS). The purpose of this study is to evaluate circulating chemerin levels as a predictor of ACS. We analyzed serum
761
samples from males with ACS (cases), matched for age and year of sample collection with healthy controls, and evaluated for potential associations between chemerin levels and the development of ACS. In addition, we measured and adjusted our results for circulating leptin and adiponectin levels, which constitute markers of energy stored in adipose tissue and insulin sensitivity respectively.
2.
Materials and methods
2.1.
Study design
In order to evaluate whether chemerin is associated with the development of ACS we performed a nested case–control study within the prospective VA Normative Aging Study. This is an ongoing longitudinal cohort study of aging that was established in 1963 [38]. Two thousand two hundred eighty healthy male volunteers, 21–84 years old, from the greater Boston (Massachusetts, USA) area were enrolled after an initial health screening, excluding subjects with chronic diseases. Subjects were reevaluated every 3 to 5 years using detailed questionnaires, on-site physical examinations and anthropometric measurements. Serum samples were collected at baseline and during the follow-up visits. These samples have been kept in − 30 °C freezers until the day of the analysis. For the purposes of our study we analyzed serum samples from 90 male participants collected at least 2, and no longer than 5 years, before the development of ACS. Serum was also analyzed in 162 non-ACS controls that had been matched for age and year of sample collection with the ACS cases in a 1:2 fashion. Serum samples were collected between 1965 and 2008. The mean age of our cohort was 66.3 ± 9.6 years (range 34–84 years). ACS was defined by ICD-8 code 410. Code 410 codes for acute myocardial infarction, including coronary artery embolism, occlusion, rupture or thrombosis, as well as infarction of heart myocardium or ventricular rupture. This study complies with the declaration of Helsinki and has been approved by the Human Studies Subcommittee of the Department of VA Medical Center and the Institutional Review Board of the Brigham and Women’s Hospital. All participants provided written informed consent.
2.2.
Biochemical measurements
Serum chemerin levels were measured with a commercially available enzyme-linked immunosorbent assay (Cat#: RD191136200R; Biovendor, Candler, NC) after extensive evaluation by our laboratory. The manufacturer’s reported sensitivity of 0.1 ng/mL, intra-assay coefficient of variation (CV) of 5.1%–7.0%, and inter-assay CV of 6 .9%–8.3% were confirmed in our laboratory and were determined to be acceptable for the differences that we wanted to detect. Serum leptin and adiponectin levels were measured using commercially available radio-immune-assays (Millipore Co. Billerica, MA) with sensitivities 0.437 ng/mL and 0.9375 ng/mL, intra-assay CV: 3.4%–8.3% and 1.78%–3.59%, and inter-assay CV: 3.0%–6.2% and 6.90%–9.25%, accordingly. The assays were performed in batches of one case followed by two control samples.
762 2.3.
M ET ABOL I SM CL IN I CA L A N D E XP E RI ME N TAL 6 3 ( 2 0 14 ) 76 0–7 66
Power considerations
Table 1 – Baseline characteristics between cases and controls. Variable
Studies in stable CAD have demonstrated that the odds ratio of CAD for the highest chemerin quartile compared with the lowest one was 1.87 (95% CI: 1.07–3.24) [35]. No other study to date has evaluated the effect of chemerin levels on ACS so we do not have any direct estimate of the potential effect size of chemerin levels as predictor of ACS. We calculated that 252 subjects would ensure 80% power and <5% probability to commit type I error (two sided) in detecting an odds ratio of 1.9 for each standard deviation increase in chemerin levels, which we consider clinically relevant.
2.4.
Statistical analysis
Statistical analysis was performed using Stata v.12 (StataCorp, College Station, TX). Continuous variables are summarized as mean ± standard error of the mean and categorical variables as percentages. Normality of the distributions was evaluated with frequency histograms and the Shapiro–Wilk statistic. Skewed variables were analyzed after logarithmic or square root transformation as indicated by the degree of skewness. Comparisons between cases and controls were performed with student’s t-test (continuous variables) and Pearson’s chisquared (categorical variables). Pearson’s partial correlation coefficient analysis was performed to evaluate for baseline correlations between different variables, adjusting for the year of the sample collection. Linear regression analysis was performed on all measured hormones and the year of sample collection to evaluate for potential time-dependent degradation. Unconditional logistic regression analysis was performed to evaluate the effects of circulating chemerin levels on the odds ratio of ACS development. Findings were secondarily confirmed using conditional logistic regression analysis. All p-values are two-sided and the alpha criterion was set at 0.05.
3.
Results
3.1.
Baseline characteristics (Tables 1 and 2)
The average age of cases and controls was 67.25 ± 9.11 and 65.85 ± 9.84 years respectively (p = 0.27). Serum samples were collected on average 18.7 ± 8.5 years prior to the analysis day in cases vs. controls (17.9 ± 8.0 vs. 19.2 ± 8.8 years, p = 0.26). Cases had on average slightly higher BMIs compared to controls (27.86 ± 3.43 vs. 26.70 ± 3.73 kg/m2, p = 0.025). Waist to hip ratio (WHR), chemerin, adiponectin and leptin levels were similar between cases and controls. The percent of subjects who smoked or had exercise intolerance even at minimal exercise was the same between cases and controls (Table 1). Chemerin levels were inversely associated with height (r = − 0.17 for cases and controls, p < 0.05) and positively associated with WHR (0.28 for controls, 0.19 for cases and controls, p < 0.05). Interestingly, chemerin levels were not correlated with weight or BMI. Chemerin levels were the same between smokers and non-smokers (181.6 ± 115.5 vs. 184.4 ± 124.6 ng/mL, p = 0.93). Chemerin levels were positively asso-
Age (years) Height (m) Weight (kg) BMI (kg/m2) WHR Chemerin (ng/mL) Adiponectin (ng/mL) Leptin (ng/mL) Smoker (yes, no) Exercise intolerance even on mild exercise (yes, no)
Cases (n = 90)
Controls (n = 162)
p-value
67.25 ± 9.11 1.75 ± 0.07 85.60 ± 13.28 27.86 ± 3.43 0.98 ± 0.049 178.24 ± 116.51 13.04 ± 8.65 9.37 ± 9.44 8 (5.81%) 17 (19.77)
65.85 ± 9.84 1.74 ± 0.06 81.59 ± 13.60 26.70 ± 3.73 0.98 ± 0.06 183.02 ± 115.53 12.76 ± 7.19 8.50 ± 10.32 5 (5.13%) 32 (20.51)
0.27 0.46 0.03 0.02 0.63 0.75 0.96 0.62 0.78 0.99
Data are shown as mean ± standard deviation for the continuous variables and N (%) for the categorical variables. BMI: body mass index, WHR: waist to hip ratio.
ciated with the year of the sample collection (b = 5.57, p < 0.001) demonstrating slow time-dependent degradation of the molecule after long term storage at − 30 °C. Similar degradation was also observed in adiponectin and leptin levels (b = 0.17, and b = 0.49 accordingly, p < 0.001).
3.2.
Chemerin as a predictor of ACS (Tables 3 and 4)
Logistic regression analysis, adjusting for the year that the sample was collected, demonstrated no association between chemerin levels and the development of ACS (OR: 0.99, 95% CI [0.99–1.001]). This association remained null after adjusting for age, BMI, WHR, circulating leptin and adiponectin levels in sequential logistic regression models (Table 3). Further analysis of the ACS OR across the different tertiles of chemerin levels failed to demonstrate any association between circulating chemerin levels and ACS development, even in the highest chemerin tertile (Table 4). Similar results were obtained using conditional regression analysis and after grouping the 2nd and 3rd tertile of chemerin levels and comparing it against the lowest one (OR: 0.83, 95% CI: [0.26– 2.08] unadjusted model; OR 0.73, 95% CI: [0.25–2.08] fully adjusted model). No other variables in the above models were independent predictors of ACS risk.
4.
Discussion
Adipose tissue, once thought to have a role primarily in energy storage, is now known to be a metabolically active endocrine organ, secreting hormones known as adipocytokines [39–41]. There is growing evidence that these adipocytokines may be a link between obesity and cardiovascular disease [42–46]. Chemerin has been recently identified as an adipocytokine with pro-inflammatory action that has been positively correlated with coronary atherosclerotic plaque burden and arterial stiffness in cross-sectional studies [32–34]. Recent case–control studies suggest that there is a positive association between the presence and severity of CAD, and circulating
763
M ET ABOL I SM CL IN I CA L A N D EX PE RI ME N TA L 6 3 ( 2 0 14 ) 76 0–7 6 6
Table 2 – Pearson’s partial coefficients between continuous variables, adjusting for the year of sample collection.
Age (years) Height (m) Weight (kg) BMI (kg/m2) WHR Chemerin (ng/mL) Adiponectin (ng/mL) Leptin (nl/mL)
Age
Height
Weight
BMI
WHR
Chemerin
Adiponectin
Leptin
1 −0.20 ⁎ −0.21 ⁎ −0.14 ⁎ 0.01 0.10 0.10 <0.01
−0.20 ⁎ 1 0.55 ⁎ 0.08 −0.02 −0.17 ⁎ 0.03 −0.06
−0.21 ⁎ 0.50 ⁎ 1 0.88 ⁎ 0.34 ⁎ <0.01 0.02 0.31 ⁎
−0.14 ⁎ 0.05 0.89 ⁎ 1 0.41 ⁎ 0.10 −0.02 0.41 ⁎
0.01 −0.03 0.31 ⁎ 0.35 ⁎ 1 0.19 ⁎ −0.13 0.33 ⁎
0.10 −0.10 0.05 0.10 0.28 ⁎ 1 0.17 ⁎ 0.63 ⁎
0.10 −0.01 0.05 −0.01 −0.13 0.15 1 0.16 ⁎
0.01 −0.01 0.37 ⁎ 0.41 ⁎ 0.34 ⁎ 0.61 ⁎ 0.17 ⁎ 1
Lower half represents correlations in pooled cases and controls, upper half represents correlations in controls only. BMI: body mass index, WHR: waist to hip ratio. ⁎ p value < 0.05.
chemerin levels [35,36]. However, there are no studies to date evaluating circulating chemerin levels as a predictor of ACS. To the best of our knowledge, this is the first study to demonstrate that chemerin levels are not associated with the development of ACS. We demonstrated that the mean levels of chemerin, collected at least 2 years before the development of ACS, are similar between ACS cases and controls. In addition, logistic regression analysis demonstrates that circulating chemerin levels could not predict the development of ACS. The latter remained true even after analyzing the data in tertiles and after adjusting for potential confounding variables. The results of our study are novel and there is no other study to date evaluating for potential associations between chemerin levels and the development of ACS. Most studies to date are in agreement that chemerin levels are positively associated with atherosclerosis and stable CAD. In a study of 430 subjects that underwent coronary angiography CAD was positively associated with increasing serum chemerin levels and this association remained significant after adjusting for age, gender, and other established risk factors for CAD [35]. A positive association between chemerin levels and CAD is also reported in a more recent study of smaller sample size by Xiaotao et al. [47]. Elevated serum chemerin levels were also found to be an independent predictor of the presence of CAD in a study of 112 patients with the metabolic syndrome [36], as
Table 3 – Logistic regression models calculating the odds ratio of ACS development for one standard deviation change in chemerin circulating levels, adjusting for potential confounders. Variables included in the model Chemerin, year Chemerin, year, age Chemerin, year, age, BMI Chemerin, year, age, WHR Chemerin, year, age, BMI, WHR Chemerin, year, age, leptin Chemerin, year, age, adiponectin Chemerin, year, age, BMI, WHR, leptin, adiponectin
Odds Ratio (95% CI) 0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99
(0.99–1.001) (0.99–1.001) (0.99–1.001) (0.99–1.002) (0.99–1.002) (0.99–1.001) (0.99–1.001) (0.99–1.002)
p-value 0.37 0.35 0.19 0.39 0.38 0.19 0.39 0.42
Year: means year of sample collection. 95% CI is the 95% confidence interval of the odds ratio. BMI: body mass index, WHR: waist to hip ratio.
well as a different study of 286 patients with type 2 diabetes [48]. Interestingly, Lehrke et al. in a cross-sectional study of 303 patients with stable typical or atypical chest pain who underwent dual-source multi-slice CT-angiography, demonstrated that chemerin levels were positively correlated with coronary plaque burden and the number of non-calcified plaques [34]. Conversely, Hah et al. in a study of 131 patients with known CAD demonstrated that although chemerin levels were positively correlated with fasting glucose, triglyceride, total cholesterol, low density lipoprotein cholesterol, and high sensitive C-reactive protein levels, they failed to be an independent risk factor of multiple vessel disease in multivariate analysis models [49]. The only in vivo study available to date evaluating the effects of chemerin in CAD has demonstrated that adenoviral-mediated chemerin overexpression in an LDL receptor knockout, high-fat diet mice model had no effect on weight, lipid levels, or extent of atherosclerosis [50]. Given the associations between chemerin and CAD in humans we suggest that rodent models, such as the ones utilized in the study above, might not be the optimal animal model for reverse translational research and the role of chemerin in
Table 4 – Logistic regression models calculating the odds ratio of ACS development across different chemerin tertiles, adjusting for potential confounders. Variables included in the model Chemerin, year
Chemerin, year, age
Chemerin, year, age, BMI
Chemerin, year, age, WHR
Chemerin, year, age, BMI, WHR
Odds Ratio (95% CI) 1st tertile 1 2nd tertile 0.63 (0.32–1.22) 3rd tertile 0.83 (0.42–1.64) 1st tertile 1 2nd tertile 0.62 (0.32–1.21) 3rd tertile 0.83 (0.42–1.63) 1st tertile 1 2nd tertile 0.63 (0.32–1.23) 3rd tertile 0.74 (0.37–1.49) 1st tertile 1 2nd tertile 0.86 (0.27–2.72) 3rd tertile 0.67 (0.22–2.05) 1st tertile 1 2nd tertile 0.81 (0.25–2.64) 3rd tertile 0.66 (0.22–2.00)
p-value
0.17 0.60 0.16 0.58 0.18 0.40 0.80 0.48 0.73 0.46
Year: means year of sample collection. 95% CI is the 95% confidence interval of the odds ratio. BMI: body mass index, WHR: waist to hip ratio.
764
M ET ABOL I SM CL IN I CA L A N D E XP E RI ME N TAL 6 3 ( 2 0 14 ) 76 0–7 66
atherosclerosis should be evaluated in other in vivo animal models as well. Furthermore, there is some evidence, mainly from crosssectional studies, that chemerin has a role in cardiovascular biology, in addition to coronary atherosclerosis. A recent study demonstrated that the degree of aortic atherosclerosis was positively correlated with chemerin expression in the periaortic and pericoronary fat [32]. Gao et al. compared chemerin mRNA expression in epicardial fat tissue from patients with and without CAD, demonstrating that chemerin mRNA expression in epicardial fat is positively associated with the presence and severity of CAD. These associations remained statistically significant even after adjustment for age, gender, BMI and waist circumference [37]. A different study demonstrated that there is a positive association between chemerin levels and arterial stiffness, as evaluated by brachial artery pulse-wave velocity [33]. One of the strengths of our study is that this is the first study to evaluate the associations between circulating chemerin levels and ACS, utilizing a state-of-the-art assay. We analyzed samples under code and assays were performed by experienced personnel who were not aware of the hypothesis of the study. In addition, our subjects were matched to controls for age, eliminating it as a potential confounder. Our subject population spans all age groups and has been collected over the last 50 years providing durability in the interpretation of our results. Chemerin levels do not exhibit any day–night variation and thus its levels are not affected by the time of sample collection [7]. One limitation of our study is the slow time-dependent degradation of chemerin, resulting from the long-term storage of the samples in − 30 °C. However, cases and controls were matched for the year of sample collection and we also analytically adjusted for this, eliminating any potential bias introduced by the long-term storage. In addition, although normative chemerin levels have not been established in the literature, the chemerin levels that we report in our study are similar to the ones observed in different studies [16,51,52]. The subjects analyzed herein were only male veterans and consequently comparisons across genders could not be performed. Furthermore, these results cannot necessarily be generalized to the general population. However, there are no data in the current literature suggesting a potential effect modification of chemerin’s associations by gender. Lastly, we measured chemerin levels at least 2 years prior to the ACS event. Whether chemerin levels at a time closer to the event could predict ACS needs to be examined in future studies. To summarize, this is the first study to date demonstrating that circulating chemerin levels are not associated with the development of ACS. Although some evidence exist that chemerin might have some deleterious effects on vascular homeostasis and could be associated with the development of coronary atherosclerosis, prospective studies demonstrating a causal association between chemerin levels and the development of stable or unstable CAD are completely lacking. Prospective studies evaluating the incidence of stable CAD and ACS in high-risk individuals across different chemerin baseline levels are encouraged. In addition, basic science studies evaluating for the mechanistic role of chemerin in the process of atherosclerosis development, plaque formation,
plaque rupture and thrombus formation are also lacking and are strongly encouraged. Future basic and translational research investigating the role of chemerin in the area of atherosclerosis development, rather than plaque stability, is warranted since chemerin seems to be associated with stable CAD rather than ACS.
Funding The Mantzoros Laboratory is supported by the Award Number 1I01CX000422-01A1 from the Clinical Science Research and Development Service of the VA Office of Research and Development. NAS is supported by Cooperative Studies Program/ERIC, US Department of Veterans Affairs and is a research component of the Massachusetts Veterans Epidemiology Research and Information Center. Dr. Spiro is supported by a Research Career Scientist award from the Clinical Science Research and Development Service, US Department of Veterans’ Affairs.
Acknowledgments KNA designed the study, performed biochemical analysis, performed the statistical analysis and wrote the manuscript. JPC performed biochemical analysis and contributed to data and sample collection. ASE coordinated the study performed biochemical analysis and contributed to data and sample collection. AS-III contributed in the statistical analysis. PV is the director of the VA Normative Ageing Study and oversaw the study cohort data collection and contributed to the manuscript writing. CSM designed the study, oversaw the entire study and the manuscript writing.
Conflict of interest The authors have no conflicts of interest and have nothing to disclose.
REFERENCES
[1] Meder W, Wendland M, Busmann A, et al. Characterization of human circulating TIG2 as a ligand for the orphan receptor ChemR23. FEBS Lett 2003;555:495–9. [2] Ernst MC, Sinal CJ. Chemerin: at the crossroads of inflammation and obesity. Trends Endocrinol Metab 2010;21:660–7. [3] Wittamer V, Franssen JD, Vulcano M, et al. Specific recruitment of antigen-presenting cells by chemerin, a novel processed ligand from human inflammatory fluids. J Exp Med 2003;198:977–85. [4] Wittamer V, Bondue B, Guillabert A, et al. Neutrophil-mediated maturation of chemerin: a link between innate and adaptive immunity. J Immunol 2005;175:487–93. [5] Nagpal S, Patel S, Jacobe H, et al. Tazarotene-induced gene 2 (TIG2), a novel retinoid-responsive gene in skin. J Invest Dermatol 1997;109:91–5. [6] Polyzos SA, Kountouras J, Anastasilakis AD, et al. Irisin in patients with nonalcoholic fatty liver disease. Metabolism 2014;63:207–17.
M ET ABOL I SM CL IN I CA L A N D EX PE RI ME N TA L 6 3 ( 2 0 14 ) 76 0–7 6 6
[7] Chamberland JP, Berman RL, Aronis KN, et al. Chemerin is expressed mainly in pancreas and liver, is regulated by energy deprivation, and lacks day/night variation in humans. Eur J Endocrinol 2013;169:453–62. [8] Bozaoglu K, Curran JE, Stocker CJ, et al. Chemerin, a novel adipokine in the regulation of angiogenesis. J Clin Endocrinol Metab 2010;95:2476–85. [9] Kaur J, Adya R, Tan BK, et al. Identification of chemerin receptor (ChemR23) in human endothelial cells: chemerin-induced endothelial angiogenesis. Biochem Biophys Res Commun 2010;391:1762–8. [10] Goralski KB, McCarthy TC, Hanniman EA, et al. Chemerin, a novel adipokine that regulates adipogenesis and adipocyte metabolism. J Biol Chem 2007;282:28175–88. [11] Roh SG, Song SH, Choi KC, et al. Chemerin—a new adipokine that modulates adipogenesis via its own receptor. Biochem Biophys Res Commun 2007;362:1013–8. [12] Bozaoglu K, Bolton K, McMillan J, et al. Chemerin is a novel adipokine associated with obesity and metabolic syndrome. Endocrinology 2007;148:4687–94. [13] Takahashi M, Takahashi Y, Takahashi K, et al. Chemerin enhances insulin signaling and potentiates insulinstimulated glucose uptake in 3 T3-L1 adipocytes. FEBS Lett 2008;582:573–8. [14] Mussig K, Staiger H, Machicao F, et al. RARRES2, encoding the novel adipokine chemerin, is a genetic determinant of disproportionate regional body fat distribution: a comparative magnetic resonance imaging study. Metabolism 2009;58:519–24. [15] Syed Ikmal SI, Zaman Huri H, Vethakkan SR, et al. Potential biomarkers of insulin resistance and atherosclerosis in type 2 diabetes mellitus patients with coronary artery disease. Int J Endocrinol 2013;2013:698567. [16] Jialal I, Devaraj S, Kaur H, et al. Increased chemerin and decreased omentin-1 in both adipose tissue and plasma in nascent metabolic syndrome. J Clin Endocrinol Metab 2013;98:E514–7. [17] Guzel EC, Celik C, Abali R, et al. Omentin and chemerin and their association with obesity in women with polycystic ovary syndrome. Gynecol Endocrinol 2014. http://dx.doi.org/ 10.3109/09513590.2014.888412 [Epub ahead of print]. [18] Wang D, Yuan GY, Wang XZ, et al. Plasma chemerin level in metabolic syndrome. Genet Mol Res 2013;12:5986–91. [19] Bozaoglu K, Segal D, Shields KA, et al. Chemerin is associated with metabolic syndrome phenotypes in a Mexican–American population. J Clin Endocrinol Metab 2009;94:3085–8. [20] Weigert J, Neumeier M, Wanninger J, et al. Systemic chemerin is related to inflammation rather than obesity in type 2 diabetes. Clin Endocrinol (Oxf) 2010;72:342–8. [21] Sell H, Divoux A, Poitou C, et al. Chemerin correlates with markers for fatty liver in morbidly obese patients and strongly decreases after weight loss induced by bariatric surgery. J Clin Endocrinol Metab 2010;95:2892–6. [22] Tonjes A, Fasshauer M, Kratzsch J, et al. Adipokine pattern in subjects with impaired fasting glucose and impaired glucose tolerance in comparison to normal glucose tolerance and diabetes. PLoS One 2010;9(1–6):e13911. http://dx.doi.org/ 10.1371/journal.pone.0013911. [23] Chen HY, Lin CC, Chiu YL, et al. Serum fetuin a and chemerin levels correlate with hepatic steatosis and regional adiposity in maintenance hemodialysis patients. PLoS One 2012;7(1–9):e38514. http://dx.doi.org/10.1371/ journal.pone.0038415. [24] Roman AA, Parlee SD, Sinal CJ. Chemerin: a potential endocrine link between obesity and type 2 diabetes. Endocrine 2012;42:243–51. [25] Gu P, Jiang W, Lu B, et al. Chemerin is associated with inflammatory markers and metabolic syndrome phenotypes
[26]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
[39] [40]
[41]
[42]
[43]
[44]
[45]
765
in hypertension patients. Clin Exp Hypertens 2013. http://dx. doi.org/10.3109/10641963.2013.827697 [Epub ahead of print]. Docke S, Lock JF, Birkenfeld AL, et al. Elevated hepatic chemerin mRNA expression in human non-alcoholic fatty liver disease. Eur J Endocrinol 2013;169:547–57. Aroor AR, McKarns S, Demarco VG, et al. Maladaptive immune and inflammatory pathways lead to cardiovascular insulin resistance. Metabolism 2013;62:1543–52. Kwon BJ, Kim DW, Her SH, et al. Metabolically obese status with normal weight is associated with both the prevalence and severity of angiographic coronary artery disease. Metabolism 2013;62:952–60. Chakaroun R, Raschpichler M, Kloting N, et al. Effects of weight loss and exercise on chemerin serum concentrations and adipose tissue expression in human obesity. Metabolism 2012;61:706–14. Terra X, Auguet T, Guiu-Jurado E, et al. Long-term changes in leptin, chemerin and ghrelin levels following different bariatric surgery procedures: Roux-en-Y gastric bypass and sleeve gastrectomy. Obes Surg 2013;23:1790–8. Polyzos SA, Kountouras J, Anastasilakis AD, et al. Irisin in patients with nonalcoholic fatty liver disease. Metabolism 2014;63(2):207–17. Spiroglou SG, Kostopoulos CG, Varakis JN, et al. Adipokines in periaortic and epicardial adipose tissue: differential expression and relation to atherosclerosis. J Atheroscler Thromb 2010;17:115–30. Yoo HJ, Choi HY, Yang SJ, et al. Circulating chemerin level is independently correlated with arterial stiffness. J Atheroscler Thromb 2012;19:59–68. Lehrke M, Becker A, Greif M, et al. Chemerin is associated with markers of inflammation and components of the metabolic syndrome but does not predict coronary atherosclerosis. Eur J Endocrinol 2009;161:339–44. Yan Q, Zhang Y, Hong J, et al. The association of serum chemerin level with risk of coronary artery disease in Chinese adults. Endocrine 2011;41:281–8. Dong B, Ji W, Zhang Y. Elevated serum chemerin levels are associated with the presence of coronary artery disease in patients with metabolic syndrome. Intern Med 2011;50:1093–7. Gao X, Mi S, Zhang F, et al. Association of chemerin mRNA expression in human epicardial adipose tissue with coronary atherosclerosis. Cardiovasc Diabetol 2011;10:87. Bell B, Rose CL, Damon A. The Veterans Administration longitudinal study of healthy aging. Gerontologist 1966;6:179–84. Sahin-Efe A, Katsikeris F, Mantzoros CS. Advances in adipokines. Metabolism 2012;61:1659–65. Ko BJ, Park KH, Mantzoros CS. Diet patterns, adipokines, and metabolism: where are we and what is next? Metabolism 2014;63:168–77. El-Mesallamy HO, Kassem DH, El-Demerdash E, et al. Vaspin and visfatin/Nampt are interesting interrelated adipokines playing a role in the pathogenesis of type 2 diabetes mellitus. Metabolism 2011;60:63–70. Van de Voorde J, Pauwels B, Boydens C, et al. Adipocytokines in relation to cardiovascular disease. Metabolism 2013;62:1513–21. Li Q, Lu Y, Sun L, et al. Plasma adiponectin levels in relation to prognosis in patients with angiographic coronary artery disease. Metabolism 1803–1808;2012:61. Giannessi D, Caselli C, Del Ry S, et al. Adiponectin is associated with abnormal lipid profile and coronary microvascular dysfunction in patients with dilated cardiomyopathy without overt heart failure. Metabolism 2011;60:227–33. Hirata A, Kishida K, Nakatsuji H, et al. High serum C1q-adiponectin/total adiponectin ratio correlates with coronary artery disease in Japanese type 2 diabetics. Metabolism 2013;62:578–85.
766
M ET ABOL I SM CL IN I CA L A N D E XP E RI ME N TAL 6 3 ( 2 0 14 ) 76 0–7 66
[46] Piestrzeniewicz K, Luczak K, Komorowski J, et al. Resistin increases with obesity and atherosclerotic risk factors in patients with myocardial infarction. Metabolism 2008;57:488–93. [47] Xiaotao L, Xiaoxia Z, Yue X, et al. Serum chemerin levels are associated with the presence and extent of coronary artery disease. Coron Artery Dis 2012;23:412–6. [48] Lin X, Tang X, Jiang Q, et al. Elevated serum chemerin levels are associated with the presence of coronary artery disease in patients with type 2 diabetes. Clin Lab 2012;58:539–44. [49] Hah YJ, Kim NK, Kim MK, et al. Relationship between chemerin levels and cardiometabolic parameters and degree of coronary stenosis in Korean patients with coronary artery disease. Diabetes Metab J 2011;35:248–54.
[50] Becker M, Rabe K, Lebherz C, et al. Expression of human chemerin induces insulin resistance in the skeletal muscle but does not affect weight, lipid levels, and atherosclerosis in LDL receptor knockout mice on high-fat diet. Diabetes 2010;59:2898–903. [51] Gisondi P, Lora V, Bonauguri C, et al. Serum chemerin is increased in patients with chronic plaque psoriasis and normalizes following treatment with infliximab. Br J Dermatol 2013;168:749–55. [52] Kim SH, Lee SH, Ahn KY, et al. Effect of lifestyle modification on serum chemerin concentration and its association with insulin sensitivity in overweight and obese adults with type 2 diabetes. Clin Endocrinol (Oxf) 2013. http://dx.doi.org/10.1111/ cen.12249.