Plasma YKL-40, a new biomarker for atrial fibrillation?

A novel biomarker in acute cholecystitis: YKL-40

BACKGROUND

The lack of a specific biomarker that can be used in the diagnosis of acute cholecystitis, a common cause of admission to the emergency department, delays physician efforts to diagnose and treat these patients. Therefore, the aim of this study was to measure plasma YKL-40 levels and investigate their diagnostic value in patients with acute cholecystitis (AC).

METHODS

This study was carried out between February 2020 and September 2020 in the adult emergency department of a tertiary university hospital. Permission was obtained from the Ethics Committee of Scientific Research on 03/02/2020 with Decision No. 03/16. The study included 80 patients who were diagnosed with acute cholecystitis and 80 healthy volunteers without known chronic diseases.

RESULTS

The median YKL-40 protein level was 798.66 pq/mL in the patient group and 392.45 pq/mL in the control group. A statistically significant difference in YKL-40 protein levels was found between the two groups. YKL-40 protein levels were significantly higher in patients diagnosed with acute cholecystitis than in healthy individuals (p < 0.001). A positive correlation was found between YKL-40 protein levels and ALT, AST, LDH, and GGT levels (r = 0.272, p = 0.015; r = 0.397, p < 0.001; r = 0.386, p < 0.001; and r = 0.264, p = 0.018; respectively).

CONCLUSION

When evaluated together with physical examination, radiological imaging and other laboratory parameters, we think that plasma YKL-40 levels can be used effectively in the diagnosis of acute cholecystitis.

Atrial fibrillation and cardiac fibrosis: A review on the potential of extracellular matrix proteins as biomarkers

The involvement of fibrosis as an underlying pathology in heart diseases is becoming increasingly clear. In recent years, fibrosis has been granted a causative role in heart diseases and is now emerging as a major contributor to Atrial Fibrillation (AF) pathogenesis. AF is the most common arrhythmia encountered in the clinic, but the substrate for AF is still being debated. Consensus in the field is a combination of cardiac tissue remodeling, inflammation and genetic predisposition. The extracellular matrix (ECM) is subject of growing investigation, since measuring circulatory biomarkers of ECM formation and degradation provides both diagnostic and prognostic information. However, fibrosis is not just fibrosis. Each specific collagen biomarker holds information on regulatory mechanisms, as well as information about which section of the ECM is being remodeled, providing a detailed description of cardiac tissue homeostasis. This review entails an overview of the implication of fibrosis in AF, the different collagens and their significance, and the potential of using biomarkers of ECM remodeling as tools for understanding AF pathogenesis and identifying patients at risk for further disease progression.

YKL-40 is highly expressed in the epicardial adipose tissue of patients with atrial fibrillation and associated with atrial fibrosis

Background

YKL-40 (CHI3L1) is a novel biomarker for inflammation, tissue remodeling, and fibrosis, as well as cardiovascular diseases. We investigated the association between YKL-40 expression in epicardial adipose tissue (EAT) and atrial fibrosis in patients with atrial fibrillation (AF).

Methods

Blood samples, subcutaneous adipose tissue (SAT), paracardial adipose tissue (PAT), EAT, and adjacent atrial myocardium were acquired from patients receiving coronary artery bypass grafts. The patients were divided into the AF group (n = 28) and the sinus rhythm (SR) group (n = 36).

Results

We did not detect a significant difference in the serum YKL-40 levels in the SR and AF groups (P = 0.145). Quantitative real-time PCR showed that YKL-40 (CHI3L1) mRNA levels in the EAT were significantly higher than in the SAT or PAT of AF patients, or the EAT of SR patients (All P < 0.001). We found similar results for YKL-40 protein levels by immunohistochemistry. Masson staining showed significantly more fibrosis in AF patients than in SR patients (P < 0.001). Western blotting indicated that AF patients had significantly higher expression of collagen I (P = 0.039). We found a linear relationship between YKL-40 mRNA expression and the collagen volume fraction of the atrial myocardium (y = 3.576x + 26.205, P < 0.001). Multivariate linear regression analysis revealed that body mass index is an independent risk factor for YKL-40 expression in EAT (β = 0.328, P = 0.011).

Conclusions

YKL-40, which is highly expressed in the EAT of patients with AF, is affected by body mass index and associated with atrial fibrosis, which may contribute to the development of AF.

Serum hs-CRP, YKL-40 and brain-derived neurotrophic factor (BDNF) associated biomarkers in non-dipper hypertension profile?

Background: Twenty-four hours dynamic blood pressure (BP) behaviour displays dipper profile defined as nocturnal systolic BP (SBP) reduction>10% compared to daytime. Non-dipper profile, nocturnal absence of SBP fall, associates an increased cardiovascular risk. We investigated the concomitant association of inflammatory bio-markers - high-sensitivity- C-reactive protein (hs-CRP), Human Chitinase3-like1 (YKL-40) and autonomic nervous system (total brain-derived neurotrophic factor, BDNF) with respect to non-dipping blood pressure status.

Material and method: Using 24h automatic BP measurements, 80 known hypertensive patients were divided into two groups: dipper group included fifty-one dipper patients (age 55.6 ±13.5 years) and non-dipper group consisted of 29 non-dipper subjects (62.07±12.03 years). Serum levels of hs-CRP were evaluated with enhanced immunoturbidimetric assay. Plasma levels of YKL-40 were measured by commercial sandwich ELISA using microplate coated with a monoclonal antibody for CHI3L1. Plasma levels of total BDNF were determined using quantitative sandwich enzyme-linked immunoassay. Statistical analysis of obtained data was performed.

Results: In the non-dipper group, a significant positive association with age over 60 years, hs-CRP values above 1.90 mg/dl was observed along with increased mean values of YKL-40. Non-dipper status is independently and statistically significantly associated with elevated levels of hs-CRP (OR: 3.248, 95% CI: 1.022-10.317, p=0.046) in multivariate odds ratio analysis. No statistically significant positive association between a median total BDNF plasma level of 1430 pg/ml and the non-dipper hypertension profile was identified.

Conclusion: Our study demonstrated that patients over 60 years, in particular, have a higher probability to present a non-dipping pattern of hypertension. hs-CRP and YKL-40 values are more likely to increase in the non-dipping hypertensive patients, and hs-CRP values above 1.9 mg/dl can identify the presence of a non-dipper blood pressure profile.

Glycoprotein YKL-40 Levels in Plasma Are Associated with Fibrotic Changes on HRCT in Asbestos-Exposed Subjects

YKL-40 is a chitinase-like glycoprotein produced by alternatively activated macrophages that are associated with wound healing and fibrosis. Asbestosis is a chronic asbestos-induced lung disease, in which injury of epithelial cells and activation of alveolar macrophages lead to enhanced collagen production and fibrosis. We studied if YKL-40 is related to inflammation, fibrosis, and/or lung function in subjects exposed to asbestosis. Venous blood samples were collected from 85 men with moderate or heavy occupational asbestos exposure and from 28 healthy, age-matched controls. Levels of plasma YKL-40, CRP, IL-6, adipsin, and MMP-9 were measured with enzyme-linked immunosorbent assay (ELISA). Plasma YKL-40 levels were significantly higher in subjects with asbestosis (n = 19) than in those with no fibrotic findings in HRCT following asbestos exposure (n = 66) or in unexposed healthy controls. In asbestos-exposed subjects, plasma YKL-40 correlated negatively with lung function capacity parameters FVC (Pearson's r −0.259, p = 0.018) and FEV₁ (Pearson's r −0.240, p = 0.028) and positively with CRP (Spearman's rho 0.371, p < 0.001), IL-6 (Spearman's rho 0.314, p = 0.003), adipsin (Spearman's rho 0.459, p < 0.001), and MMP-9 (Spearman's rho 0.243, p = 0.025). The present finding suggests YKL-40 as a biomarker associated with fibrosis and inflammation in asbestos-exposed subjects.

Serum YKL-40 is increased in patients with slow coronary flow

OBJECTIVES

There is accumulating evidence that inflammation plays a major role in the development of the slow coronary flow (SCF) phenomenon. YKL-40 has been suggested to be a potential biomarker of inflammation. In this study, we aimed to study YKL-40 as it relates to SCF.

MATERIALS AND METHODS

Patients who underwent coronary angiography before and had angiographically normal coronary arteries of varying coronary flow rates without any atherosclerotic lesion were enrolled in this study. Patients who had thrombolysis in myocardial infarction frame counts (TFC) above the normal cutoffs were considered to have SCF and those within normal limits were considered to have normal coronary flow (NCF). The YKL-40 levels and biochemical profiles of all patients were studied and analyzed.

RESULTS

There were 41 patients in the SCF group and 209 patients in the NCF group. Compared with the NCF patients, SCF patients had higher serum high-sensitivity C-reactive protein (hs-CRP) (P=0.0003) and YKL-40 (P=0.0007) levels. A positive correlation was detected between the YKL-40 levels and hs-CRP (r=0.7021, P<0.001), and the mean TFC (r=0.4038, P=0.0088) in SCF patients.

CONCLUSION

Our study showed that YKL-40 levels are higher and correlated positively with TFC and hs-CRP in SCF patients. This finding suggests that YKL-40 may be a useful marker and predictor for SCF.

New inflammatory markers for prediction of non-dipper blood pressure pattern in patients with essential hypertension: Serum YKL-40/Chitinase 3-like protein 1 levels and echocardiographic epicardial adipose tissue thickness

The aim of the present study was to investigate whether YKL-40 levels and epicardial adipose tissue (EAT) thickness were associated with non-dipping pattern in essential hypertension (HT). Age- and sex-matched 40 dipper hypertensive patients and 40 non-dipper hypertensive patients were included in the study. Non-dippers had significantly increased EAT thickness and higher YKL-40 and high-sensitivity C-reactive protein levels than dippers. Multivariate logistic regression analysis showed that the EAT thickness and serum levels of YKL-40 and high-sensitivity C-reactive protein were independent predictors of non-dipping pattern in essential HT. In essential HT, presence of non-dipping pattern is associated with increased inflammatory response.

Circulating YKL-40 level, but not CHI3L1 gene variants, is associated with atherosclerosis-related quantitative traits and the risk of peripheral artery disease

YKL-40, a pleotropic cytokine, is emerging as a risk factor and a prognostic predictor of atherosclerotic cardiovascular disease. We attempted to elucidate the genetic, clinical and biochemical correlates of circulating YKL-40 level and, by combining it with CHI3L1 gene variants, with the risk and long-term mortality of peripheral artery disease (PAD). Plasma YKL-40 concentrations were measured in 612 Taiwanese individuals who had no clinically overt systemic disease. Clinical parameters, CHI3L1 gene promoter variants and 18 biomarker levels were analyzed. Eighty-six PAD patients were further enrolled for analysis. Significant associations were found between CHI3L1 genotypes/haplotypes and YKL-40 levels for the health examination subjects (smallest p = 8.36 × 10-7 for rs4950928 and smallest p = 1.72 × 10-10 for haplotype TGG) and also for PAD patients. For the health examination subjects, circulating YKL-40 level, but not CHI3L1 gene variants, were positively associated with age, smoking, and circulating levels of triglyceride, lipocalin 2 and multiple inflammatory biomarkers and negatively associated with low-density-lipoprotein cholesterol levels. Circulating YKL-40 level is also significantly associated with the risk of PAD (p = 3.3 × 10-23). Circulating YKL40 level, but not CHI3L1 gene promoter variants, is associated with the risk of PAD in Taiwanese. The association of YKL-40 levels with multiple quantitative traits relating to the risk of PAD may provide a molecular basis linking YKL-40 to atherosclerotic cardiovascular disease.

Serum YKL-40: a potential biomarker for psoriasis or endothelial dysfunction in psoriasis?

Psoriasis is a disease that can contribute to a risk of atherosclerosis. In several studies, impaired endothelial dysfunction (ED) is correlated with psoriasis. Serum YKL-40 is a new inflammatory biomarker of vascular damage, like ED and cardiovascular diseases. The aim of the study was to compare relevance of serum YKL-40 levels in psoriasis patients and healthy subjects according to ED diagnosis and identifiable cardiovascular risk factors. Sixty (31 female, 29 male) patients with plaque psoriasis, and 30 (18 female, 12 male) healthy controls were selected according to whether they had at least one or no identifiable risk factors for cardiovascular disease. All subjects were evaluated ultrasonographically for endothelial function and diagnosed as with or without ED and all groups compared for serum YKL-40 levels. YKL-40 levels of psoriatic patients with ED were higher than healthy controls with ED (P = <0.05). There were no statistical differences in between subjects without ED. YKL-40 levels of patients over age of 40 were higher than younger ones (P < 0.05). But in healthy controls, there were no differences. In comparison of cardiovascular risk-positive (RP) patients and RP healthy subjects, YKL-40 levels were higher in RP patients (P = <0.05). The elevation of plasma YKL-40 in psoriasis can be associated not only with inflammation of the disease, but also with ED. YKL-40 can be used as a marker for predicting and preventing cardiovascular diseases in RP psoriatic patients with age above 40.

Serum YKL-40 concentrations are elevated and correlated with disease severity in patients with obstructive sleep apnea syndrome

Abstract Inflammation plays a critical role in the pathogenesis of obstructive sleep apnea syndrome (OSAS). YKL-40 is a novel biomarker of systemic inflammation. We aim to detect serum YKL-40 concentrations in OSAS patients and to clarify their relationship with clinical severity of the disease. We enrolled 159 OSAS patients and 104 healthy controls. The presence and severity of OSAS was assessed by Apnea-hypopnea index (AHI). Serum YKL-40 concentrations were detected by enzyme-linked immunosorbent assay (ELISA). We demonstrated that serum YKL-40 concentrations were significantly elevated in OSAS patients than those in controls. Multivariate logistic regression including all variables revealed that YKL-40 was the significant and independent predictor for the present of OSAS. In OSAS patients, there is a significant positive correlation between increments in serum YKL-40 concentrations and severity of OSAS. Serum YKL-40 concentrations were independently and significantly correlated with AHI scores. These results suggest that YKL-40 could be used as a potential biomarker for predicting the development and progression of OSAS.

Atrial fibrillation: inflammation in disguise?

Atrial fibrillation is highly prevalent, and affected patients are at an increased risk of a number of complications, including heart failure and thrombo-embolism. Over the past years, there has been increasing interest in the role of inflammatory processes in atrial fibrillation, from the first occurrence of the arrhythmia to dreaded complications such as strokes or peripheral emboli. As the standard drug combination which aims at rate control and anticoagulation only offers partial protection against complications, newer agents are needed to optimize treatment. In this paper, we review recent knowledge regarding the impact of inflammation on the occurrence, recurrence, perpetuation and complications of the arrhythmia, as well as the role of anti-inflammatory therapies in the treatment for the disease.

Diabetes, Obesity and Atrial Fibrillation: Epidemiology, Mechanisms and Interventions

Body mass index (BMI) is a powerful predictor of death, type 2 diabetes (T2DM) and cardiovascular (CV) morbidity and mortality. Over the last few decades, we have witnessed a global rise in adult obesity of epidemic proportions. Similarly, there has been a parallel increase in the incidence of atrial fibrillation (AF), itself a significant cause of cardiovascular morbidity and mortality. This may be partly attributable to advances in the treatment of coronary heart disease (CHD) and heart failure (HF) improving life expectancy, however, epidemiological studies have demonstrated an independent association between obesity, diabetes and AF, suggesting possible common pathophysiological mechanisms and risk factors. Indeed, cardiac remodeling, haemodynamic alterations, autonomic dysfunction, and diastolic dysfunction have been reported in obese and diabetic cohorts. Moreover, diabetic cardiomyopathy is characterized by an adverse structural and functional cardiac phenotype, which may predispose to the development of AF. In this review, we discuss the pathophysiological and mechanistic relationships between obesity, diabetes and AF, and some of the challenges posed in the management of this high-risk group of individuals.

Angiotensin II blockade, YKL-40 and maintenance of sinus rhythm after electrical cardioversion for atrial fibrillation

High levels of the novel inflammatory marker YKL-40 have been demonstrated in inflammatory environments and in remodeling of the extracellular matrix. Both are key components in atrial wall remodeling in atrial fibrillation (AF). We studied the relation between rhythm outcome after electrical cardioversion (ECV) for persistent AF and serum levels of YKL-40. A secondary point of interest was a potential effect of the angiotensin receptor blocker candesartan on YKL-40 levels. In the Candesartan in the Prevention of Relapsing Atrial Fibrillation (CAPRAF) study, 171 patients with persistent AF were randomized to receive candesartan 8mg once daily or placebo for 3-6 weeks before ECV and candesartan 16mg once daily or placebo for 6 months after ECV. Serum levels of YKL-40 were measured in fasting blood samples collected at baseline and at end of the study. Mean age was 64±11 years, and 39 (22.8%) were women. Sinus rhythm was maintained for 6 months after ECV in 41 (23.9%). Baseline levels of YKL-40 were significantly correlated to age (Spearmans rho; rs=0.442; p<0.001), CHA2DS2-VASc(1) score (rs=0.256; p<0.001) and left atrial diameter (rs=0.185; p=0.017). By use of Kaplan-Meier quartile analysis of baseline YKL-40 levels, no relation between YKL-40 levels and risk of AF recurrence was found. End of study YKL-40 levels were unchanged from baseline, both in patients with AF recurrence and those maintaining sinus rhythm for 6 months. Treatment with candesartan had no influence on serum YKL-40 levels.

Obesity, diabetes and atrial fibrillation; epidemiology, mechanisms and interventions

The last few decades have witnessed a global rise in adult obesity of epidemic proportions. The potential impact of this is emphasized when one considers that body mass index (BMI) is a powerful predictor of death, type 2 diabetes (T2DM) and cardiovascular (CV) morbidity and mortality [1, 2]. Similarly we have witnessed a parallel rise in the incidence of atrial fibrillation (AF), the commonest sustained cardiac arrhythmia, which is also a significant cause of cardiovascular morbidity and mortality. Part of this increase is attributable to advances in the treatment of coronary heart disease (CHD) and heart failure (HF) improving life expectancy and consequently the prevalence of AF. However, epidemiological studies have demonstrated an independent association between obesity and AF, possibly reflecting common pathophysiology and risk factors for both conditions. Indeed, weight gain and obesity are associated with structural and functional changes of the cardiovascular system including left atrial and ventricular remodeling, haemodynamic alterations, autonomic dysfunction, and diastolic dysfunction. Moreover, diabetic cardiomyopathy is characterized by an adverse structural and functional cardiac phenotype which may predispose to the development of AF [3]. In this review, we discuss the pathophysiological and mechanistic relationships between obesity, diabetes and AF, and the challenges posed in the management of this high-risk group of individuals.

A polymorphism associated with increased levels of YKL-40 and the risk of early onset of lone atrial fibrillation

Background

Plasma levels of YKL-40 are elevated in patients with atrial fibrillation (AF). We hypothesized that a single nucleotide polymorphism (SNP) that affects YKL-40 plasma levels is associated to the risk of lone AF.

Findings

We included 178 young patients with lone AF and the first episode before the age of 40 years, and a control group of 875 healthy individuals. We analyzed a promoter SNP (−131CG) (rs4950928) in the Chitinase 3–like 1 (CHI3L1) gene encoding YKL-40, which had previously been associated with elevated levels of YKL-40.

Conclusions

The (−131CG) genotype was not associated with increased risk of AF. Genetically increased YKL-40 levels were not associated to AF.

Hypoadiponectinemia in patients with paroxysmal atrial fibrillation

Background and Objectives

Adiponectin is an adipose tissue-derived hormone that has beneficial effects on cardiac function and has been reported to be associated with lipid metabolism, glucose metabolism, and insulin resistance. Serum levels of adiponectin are reduced in obese individuals compared with non-obese individuals. Obesity is associated with an increased incidence of atrial fibrillation (AF); however, the role of adiponectin in AF is unclear. The aim of this study is to evaluate the relationship between the plasma adiponectin level and AF.

Subjects and Methods

Sixty-one consecutive patients were prospectively enrolled for this study. Subjects were divided into two groups: patients with AF (n=30) and controls (n=31). Laboratory evaluation, including levels of plasma adiponectin, was performed and echocardiographic parameters were measured.

Results

The baseline characteristics were not different between the two groups. The plasma adiponectin level of patients in the AF group was significantly lower than in the control group (14.9±7.2 vs. 19.±8.9 µg/mL, p<0.05). In addition, when we divided the AF patients into paroxysmal and chronic AF, the plasma adiponectin level was significantly lower in patients with paroxysmal AF, compared with the control group. In multiple binary logistic regression analysis to evaluate the independent predictors for AF, adiponectin and left atrial diameter were strong independent predictors of AF.

Conclusion

In this study a lower plasma adiponectin concentration was significantly associated with that of paroxysmal AF. Hypoadiponectinemia can potentially be an important risk factor for AF.

Variations of CHI3L1, levels of the encoded glycoprotein YKL-40 and prediction of fatal and non-fatal ischemic stroke

Background

Polymorphisms of CHI3L1 are associated with inter-individual YKL-40 levels and YKL-40 is associated with an increased mortality and is elevated in patients with cardiovascular disease. We investigated the association between single nucleotide polymorphisms (SNPs) of CHI3L1, serum YKL-40 levels and all-cause and cardiovascular mortality and first-time incidence of myocardial infarction, ischemic heart disease (IHD) and stroke.

Methodology/Principal Findings

12 SNPs of CHI3L1 were genotyped and serum YKL-40 was measured in 2656 Danes representative of the general population. Median follow-up period was 15 (0–16) years. Admission data and deaths were ascertained from registers from the Danish National Board of Health. Fourth quartile YKL-40 levels were associated with an increased mortality risk of ischemic stroke (HR 2.44 (1.01–5.88), p = 0.041) and so were homozygotes of the minor allele of rs872129 (HR 9.35 (1.25–69.87, p = 0.022)). Both continuous YKL-40 levels and 4^th quartile YKL-40 values (>85 ng/ml) were associated with all-cause mortality (HRs 1.22 (95% CI, 1.10–1.35), p<0.0001, and 1.40 (1.15–1.71), p<0.0001), an increased risk of first-time stroke (HR 1.16 (1.01–1.33), p = 0.04, and 1.63 (1.23–2.16), p = 0.001) and a decreased risk of incidence of IHD (HR 0.77 (0.65–0.91), p = 0.002, and 0.61 (0.44–0.85), p = 0.003).

Conclusions/Signficance

High YKL-40 levels (>85 ng/ml) and rs872129 were associated with an increased mortality risk of ischemic stroke, but high YKL-40 levels were also inverse related with the risk of incidence of IHD. This could be a chance finding but could also elucidate that YKL-40 plays different roles in development of thromboembolisms versus the formation of local thrombosis.

YKL-40 levels and atrial fibrillation in the general population

BACKGROUND

Atrial fibrillation is associated with inflammation. In contrast to inflammatory markers like C-reactive protein (CRP) and fibrinogen produced in the liver, YKL-40 is produced at the site of inflammation including in the myocardium. We hypothesized that elevated plasma YKL-40 levels associate with increased risk of atrial fibrillation.

METHOD AND RESULTS

We measured plasma YKL-40 in 8731 participants from the prospective Copenhagen City Heart Study including 896 individuals who developed atrial fibrillation during up to 18 years of follow-up. Additionally, we measured YKL-40 in 6621 individuals from the cross-sectional Copenhagen General Population Study including 337 cases with atrial fibrillation. A YKL-40 level >95% percentile (>204 μg/L) versus <25% percentile (<36 μg/L) associated prospectively with a 2.10-fold (95%CI:1.43-3.09) increased risk of atrial fibrillation. Hazard ratios attenuated slightly after multifactorial adjustment to 2.01 (1.35-2.98), and further after additional adjustment for heart failure to 1.89 (1.27-2.80), for plasma CRP to 1.79 (1.20-2.67), and for fibrinogen levels to 1.89 (1.27-2.81). Adjusting multifactorially including both heart failure, CRP, and fibrinogen attenuated the risk of atrial fibrillation to 1.79 (1.20-2.67). These findings were supported in the cross-sectional study with an odds ratio of 2.73 (1.46-5.11) for a YKL-40 level >95% percentile versus <25% percentile, attenuating to an odds ratio of 2.13 (1.09-4.18) when adjusting multifactorially including heart failure, CRP, and fibrinogen.

CONCLUSIONS

Elevated plasma YKL-40 levels robustly associated with increased risk of atrial fibrillation originating from hospital admissions or visits to the emergency department, independent of heart failure, and CRP and fibrinogen levels. These findings need to be confirmed in other independent studies.

YKL-40: a new biomarker in cardiovascular disease?

Cardiovascular disease in the form of coronary artery disease is the most common cause of death in western countries. Early treatment with stabilizing drugs and mechanical revascularization by percutaneous coronary intervention or coronary bypass surgery has reduced the mortality significantly. But in spite of improved treatments, many patients are still plagued by a high frequency of angina symptoms, hospitalizations and a poor prognosis. There is a need for new independent or supplementary biomarkers that can help to predict cardiovascular disease and cardiovascular events earlier and more precisely, and thus accompany existing biomarkers in both primary and secondary cardiovascular prevention. One such potential new biomarker is the protein YKL-40. As an independent biomarker in both cardiovascular diseases and noncardiovascular diseases, current evidence suggests YKL-40 to be most useful as a marker of disease severity, prognosis and short survival. However, future studies will evaluate whether YKL-40 can be used for monitoring of the treatment effect in different patient populations with a distinct disease diagnosis. In this article we explore present knowledge on YKL-40 as a biomarker in cardiovascular disease.

YKL-40-A Protein in the Field of Translational Medicine: A Role as a Biomarker in Cancer Patients?

YKL-40 is a 40 kDa glycoprotein produced by cancer cells, inflammatory cells and stem cells. It probably has a role in cell proliferation and differentiation, inflammation, protection against apoptosis, stimulation of angiogenesis, and regulation of extracellular tissue remodelling. Plasma levels of YKL-40 are often elevated in patients with localized or advanced cancer compared to age-matched healthy subjects. Several studies have demonstrated that high plasma YKL-40 is an independent prognostic biomarker of short survival in patients with different types of cancer. However, there is not yet sufficient data to support determination of plasma YKL-40 outside research projects as a biomarker for screening of gastrointestinal cancer and determination of treatment response and poor prognosis before or during treatment and follow-up. Plasma YKL-40 is also elevated in patients with other diseases than cancer, e.g., severe infections, cardiovascular disease, diabetes, chronic obstructive lung disease, asthma, liver fibrosis and rheumatoid arthritis. Co-morbidity should therefore always be considered in patients with cancer, since other sources than cancer cells can increase plasma YKL-40 levels. Future focused translational research projects combining basic and clinical research are needed in a joint effort to answer questions of the complex function and regulation of YKL-40 and the question if plasma YKL-40 is a clinical useful biomarker in patients with cancer.

Plasma YKL-40 levels are elevated in patients with chronic heart failure

OBJECTIVES

Congestive heart failure (CHF) has been associated with elevated biomarker levels reflecting chronic low-grade inflammation. YKL-40 is a biomarker with increasing levels in patients with cardiovascular disease (CVD) of increasing severity. Furthermore, YKL-40 is associated with all-cause and cardiovascular mortality. We investigated plasma YKL-40 levels in patients with CHF and evaluated the possible predictive value with respect to overall mortality and recurrent cardiovascular outcomes.

DESIGN

Plasma YKL-40 was measured in 194 CHF patients and in 117 age-matched individuals without CVD.

RESULTS

Median YKL-40 levels were approximately 77% higher in patients with CHF (106 (IQR, 66-184) ng/ml vs. 60 (IQR, 42-97) ng/ml, p < 0.0001). We found a trend towards an association of YKL-40 levels with urinary albumin/creatinine ratio (UACR) (beta = 0.12, p = 0.08). YKL-40 levels were not predictive of overall mortality (p = 0.59), major cardiovascular events (p = 0.23) or events of incompensation (p = 0.56).

CONCLUSIONS

Plasma YKL-40 levels are elevated in patients with CHF but show no association with other clinical or paraclinical variables. YKL-40 levels were not predictive of overall mortality or incident cardiovascular events. Most likely, elevated YKL-40 levels in CHF patients are explained by the presence of concomitant diseases but a role of YKL-40 in low-grade inflammation is not excluded.

Plasma YKL-40 is elevated in patients with recurrent atrial fibrillation after catheter ablation

AIM

To study plasma YKL-40 in patients with atrial fibrillation (AF) treated with radiofrequency (RF) catheter ablation and to assess the predictive role of plasma YKL-40 and its changes after restoration of sinus rhythm (SR).

METHODS

Forty-six patients (mean age 55 years, range 31-81) with paroxysmal/persistent AF were treated with RF catheter ablation; Holter monitoring for 14 days was performed before ablation and after 3 months. Recurrent symptomatic AF or atrial tachycardia >10 min was considered failure, and the patients were offered a second ablation session. YKL-40 was determined in plasma samples taken prior to ablation and at follow-up visits up to 12 months after ablation.

RESULTS

After a maximum of two ablations, 19 patients (41%) had SR without recurrence of AF after 12 months. The patients with no recurrence of AF had significantly lower baseline plasma levels of YKL-40 prior to ablation compared to patients with recurrence of AF (31 vs. 62 microg/l, P = 0.029). Plasma YKL-40 was not an independent predictor of recurrence of AF after ablation. No significant changes in plasma YKL-40 levels were seen from baseline to follow-up at 12 months.

CONCLUSION

In patients with paroxysmal or persistent AF treated with catheter ablation, high plasma YKL-40 before ablation is associated with recurrence of AF.

YKL-40--an emerging biomarker in cardiovascular disease and diabetes

Several inflammatory cytokines are involved in vascular inflammation resulting in endothelial dysfunction which is the earliest event in the atherosclerotic process leading to manifest cardiovascular disease. YKL-40 is an inflammatory glycoprotein involved in endothelial dysfunction by promoting chemotaxis, cell attachment and migration, reorganization and tissue remodelling as a response to endothelial damage. YKL-40 protein expression is seen in macrophages and smooth muscle cells in atherosclerotic plaques with the highest expression seen in macrophages in the early lesion of atherosclerosis. Several studies demonstrate, that elevated serum YKL-levels are independently associated with the presence and extent of coronary artery disease and even higher YKL-40 levels are documented in patients with myocardial infarction. Moreover, elevated serum YKL-40 levels have also been found to be associated with all-cause as well as cardiovascular mortality. Finally, YKL-40 levels are elevated both in patients with type 1 and type 2 diabetes, known to be at high risk for the development of cardiovascular diseases, when compared to non-diabetic persons. A positive association between elevated circulating YKL-40 levels and increasing levels of albuminuria have been described in patients with type 1 diabetes indicating a role of YKL-40 in the progressing vascular damage resulting in microvascular disease.

This review describes the present knowledge about YKL-40 and discusses its relation to endothelial dysfunction, atherosclerosis, cardiovascular disease and diabetes and look ahead on future perspectives of YKL-40 research.