IL-6, but not TNF-α, increases plasma YKL-40 in human subjects

YKL-40 (chitinase-3-like protein 1) serum levels are associated with abdominal aortic calcification in hemodialysis patients

BACKGROUND

Vascular calcification (VC) is highly prevalent and predicts cardiovascular mortality in dialysis patients. The mechanisms are still unclear. Inflammation is a well-known inducer of VC. YKL-40 has been suggested as a novel biomarker of inflammation and has been demonstrated to be associated with cardiovascular mortality in hemodialysis patients. This study aims to evaluate the relationship between serum YKL-40 and VC in hemodialysis (HD) patients.

METHODS

A total of 109 HD patients and 31 healthy controls were enrolled in the study from September 2014 to December 2014. We evaluated the abdominal aortic calcification (AAC) score by plain X-ray films of the abdomen and measured serum YKL-40 concentrations using enzyme-linked immunosorbent assay. We also examined the relationship between YKL-40 levels and AAC scores in HD patients.

RESULTS

Serum YKL-40 levels in HD patients were significantly higher than those in healthy controls [199.8 (144.8, 288.7) vs. 71.9 (52.8, 89.3) ng/ml; P < 0.001]. There was a tendency that YKL-40 levels in diabetic hemodialysis patients were higher than those in nondiabetic patients [217.8 (155.3, 335.8) vs. 192.9 (135.9, 274.4) ng/ml; P = 0.093]. A significant positive correlation was found between serum YKL-40 level and AAC score in these patients (r = 0.410, P = 0.003). Multiple regression analysis showed that Ln(YKL-40) was independently associated with AAC score in HD patients (P = 0.044).

CONCLUSION

This study showed high serum YKL-40 concentrations in chronic HD patients and that YKL-40 was independently associated with increased AAC in hemodialysis patients.

YKL-40 as a biomarker in various inflammatory diseases: A review

YKL-40 or Chitinase-3-Like Protein 1 (CHI3L1) is a highly conserved glycoprotein that binds heparin and chitin in a non-enzymatic manner. It is a member of the chitinase protein family 18, subfamily A, and unlike true chitinases, YKL-40 is a chitinase-like protein without enzymatic activity for chitin. Although its accurate function is yet unknown, the pattern of its expression in the normal and disease states suggests its possible engagement in apoptosis, inflammation and remodeling or degradation of the extracellular matrix. During an inflammatory response, YKL-40 is involved in a complicated interaction between host and bacteria, both promoting and attenuating immune response and potentially being served as an autoantigen in a vicious circle of autoimmunity. Based on its pathophysiology and mechanism of action, the aim of this review was to summarize research on the growing role of YKL-40 as a persuasive biomarker for inflammatory diseases' early diagnosis, prediction and follow-up (e.g., cardiovascular, gastrointestinal, endocrinological, immunological, musculoskeletal, neurological, respiratory, urinary, infectious) with detailed structural and functional background of YKL-40.

Inflammatory markers in children with obstructive sleep apnea syndrome

Objective

To evaluate serum inflammatory markers of YKL-40, Interleukin-6 (IL-6), Interleukin-8(IL-8), Interleukin-10(IL-10), TNF-α(tumor necrosis factor-α), and CRP (C-reactive protein) in children with and without OSAS.

Methods

The ELISA technique has been used to identify the concentration of inflammatory markers such as YKL-40, IL-6, IL-8, IL-10, TNF-α, and CRP in the serum of 83 children with OSAS and 83 children without OSAS.

Results

Serum levels of YKL-40, IL-6, IL-8, and IL-10 were found to be increased in children with OSAS. YKL-40 was found to be positively correlated with IL-6 and IL-8, and negatively correlated with IL-10. At the same time,YKL-40 was also found to be positively correlated with OAHI and LoSpO2% in OSAS group. IL-8 was positively correlated with OAHI whereas IL-10 was positively correlated with LoSpO2.

Conclusion

Children with OSAS are in a systemic inflammatory state. YKL-40 together with IL-8 may act as serum inflammatory markers and provide an indication for the diagnosis of children with OSAS.

Chitinase-3-like Protein 1 (YKL-40): A New Biomarker of Inflamma-tion in Pyoderma Gangrenosum

Pyoderma gangrenosum (PG) is a rare, neutrophil-ic dermatosis with unclear aetiopathology, considered as an autoinflammatory disease, associated with other immune-mediated disorders. Chitinase-3-like protein 1 (YKL-40) is an inflammatory biomarker secreted by a wide variety of cells, including neutrophils. To evaluate YKL-40 serum level in relation to clinicopathological data, 48 patients with PG and 40 healthy controls were enrolled in the study. Skin lesions were measured to calculate the affected area. Inflammatory parameters (C-reactive protein, white blood cell count with neutrophils) were determined from blood samples. YKL-40 and IL-6 levels were measured in serum by enzyme-linked immunosorbent assay. YKL-40 serum level was significantly higher in patients with PG than in controls (58.4 vs 36.4 ng/ml, respectively; p < 0.00001). The positive correlation between YKL-40 level and IL-6 level was observed (r=0.48, p = 0.0006) along with a trend towards significance of relationship between YKL-40 level and C-reactive protein (r=0.28, p = 0.052). YKL-40 can be considered a valuable biomarker of inflammation in PG.

Diagnostic value of YKL-40 for patients with asthma: A meta-analysis

Objective: YKL-40 is a highly conserved and chitin-bound human glycoprotein in mammals that is associated with airway inflammation and has no enzyme activity. We aimed to conduct a meta-analysis to assess the use of YKL-40 levels as a diagnosis of asthma. Methods: A meta-analysis was conducted based on the data from medical literature data base searches with time restrictions of January 2007 to January 2021. We searched and extracted relevant information from a total of 15 studies that reported YKL-40 levels in patients with asthma and in healthy controls, and obtained a sample of 1647 patients with asthma and 1259 healthy controls. Standardized mean differences (SMD) with 95% confidence intervals (CI) were calculated for this study by using statistical software packages. Results: Serum YKL-40 levels were higher in the patients with asthma than in the healthy controls (SMD 1.36 ng/ml [95% CI, 0.82-1.89 ng/ml]). YKL-40 levels are elevated in pediatric patients with asthma (SMD 2.26 ng/ml [95% CI, 1.33-3.18 ng/ml]) and in adult patients with asthma (SMD 0.96 ng/ml [95% CI, 0.26-1.66 ng/ml]). In addition, a subgroup analysis of asthma disease status showed that YKL-40 levels were significantly increased in the patients with stable asthma (SMD 1.69 ng/ml [95% CI, 0.81-2.56 ng/ml]) and in those with acute exacerbation asthma (SMD 3.31 ng/ml [95% CI, 2.04-4.58 ng/ml]), and serum YKL-40 levels were significantly higher in patients with acute exacerbation asthma than in patients with stable asthma (SMD 1.49 ng/ml [95% CI, 0.50-2.48 ng/ml]). Conclusion: Results of this meta-analysis suggested that increased serum levels of YKL-40 in patients with asthma could be used as an emerging indicator for distinguishing individuals with asthma from healthy individuals.

Associations between YKL-40 and markers of disease severity and death in patients with necrotizing soft-tissue infection

Background

Necrotizing soft-tissue infection (NSTI) is a severe and fast-progressing bacterial infection. Prognostic biomarkers may provide valuable information in treatment guidance and decision-making, but none have provided sufficient robustness to have a clinical impact. YKL-40 may reflect the ongoing pathological inflammatory processes more accurately than traditional biomarkers as it is secreted by the activated immune cells, but its prognostic yields in NSTI remains unknown. For this purpose, we investigated the association between plasma YKL-40 and 30-day mortality in patients with NSTI, and assessed its value as a marker of disease severity.

Methods

We determined plasma YKL-40 levels in patients with NSTI (n = 161) and age-sex matched controls (n = 65) upon admission and at day 1, 2 and 3.

Results

Baseline plasma YKL-40 was 1191 ng/mL in patients with NSTI compared with 40 ng/mL in controls (p < 0.001). YKL-40 was found to be significantly higher in patients with septic shock (1942 vs. 720 ng/mL, p < 0.001), and in patients receiving renal-replacement therapy (2382 vs. 1041 ng/mL, p < 0.001). YKL-40 correlated with Simplified Acute Physiology Score II (Rho 0.33, p < 0.001). Baseline YKL-40 above 1840 ng/mL was associated with increased risk of 30-day mortality in age-sex-comorbidity adjusted analysis (OR 3.77, 95% CI; 1.59–9.24, p = 0.003), but after further adjustment for Simplified Acute Physiology Score II no association was found between YKL-40 and early mortality.

Conclusion

High plasma YKL-40 to be associated with disease severity, renal-replacement therapy and risk of death in patients with NSTI. However, YKL-40 is not an independent predictor of 30-day mortality.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06760-x.

Relationship between Serum YKL-40 Level and Forearm Arterial Patency after Repair

BACKGROUND

The study aimed to assess the effects of serum YKL-40 level on patency at the repair site in patients who underwent arterial repair at the level of the forearm.

METHODS

The study included 58 subjects, including 29 patients (aged 18-50 years) who had ulnar or radial artery injury secondary to cut injury to wrist between June 2015 and November 2019 and no comorbid disease and 29 age- and sex-matched healthy controls. The vascular patency was assessed using Doppler sonography in patients who underwent arterial repair at the level of the forearm. The patients were defined as flow failure if the blood flow was ≤50%, and sufficient flow if the blood flow was >50% of those in the synonymous artery on the intact extremity. The YKL-40 level differences in the patient and control groups were compared to those in the sufficient and insufficient flow groups.

RESULTS

The patients were stratified into 2 groups based on the presence of sufficient flow. The mean YKL level was 11.96 ± 8.87 in the sufficient flow groups, whereas it was 32.22 ± 15.43 in the insufficient flow groups (p= 0.038). Besides, it was found that each unit of increase in the YKL-40 level increased the likelihood of having flow failure by 1.128.

CONCLUSION

Based on our results, it was observed that over-expression of the YKL-40 level has adverse effects on patency following arterial repair.

Associations of plasma YKL-40 concentrations with heel ultrasound parameters and bone turnover markers in the general adult population

OBJECTIVE

YKL-40, also known as chitinase-3-like protein 1, is a new proinflammatory biomarker, that might play a role in tissue remodeling and bone resorption. Here we evaluated the associations of the YKL-40 plasma concentration with heel ultrasound parameters and bone turnover markers (BTMs) in adult men and women from the general population. We tested for a causal role of YKL-40 on bone metabolism using published single nucleotide polymorphisms (SNPs) with consequences for YKL-40 expression and function.

METHODS

Data were obtained from two population-based cohorts: the Study of Health in Pomerania (SHIP) and SHIP-Trend. Quantitative ultrasound (QUS) measurements at the heel were performed and bone turnover was assessed by measurement of intact amino-terminal propeptide of type I procollagen (PINP) and carboxy-terminal telopeptide of type I collagen (CTX). Associations between the YKL-40 plasma concentration and the QUS-based parameters, bone turnover marker (BTM) concentrations and 44 SNPs, including the lead SNP rs4950928, were evaluated in 382 subjects. Furthermore, we assessed the associations between the same SNPs and the QUS-based parameters (n = 5777) or the BTM concentrations (n = 7190).

RESULTS

Sex-specific linear regression models adjusted for a comprehensive panel of interfering covariantes revealed statistically significant inverse associations between YKL-40 and all QUS-based parameters as well as positive associations with CTX in women. The rs4950928 polymorphism was associated with YKL-40 in men and women but none of the tested SNPs was associated with the QUS-based parameters or the BTMs after correction for multiple testing.

CONCLUSIONS

Plasma YKL-40 concentrations are associated with QUS-based parameters as well as CTX concentrations in women but these associations are probably not causal.

Prognostic utility of serum YKL-40 in patients with cervical cancer

Inflammation is one of the hallmarks of cancer and plays a crucial role in the development and progression. The objective of the present study was to investigate if high serum YKL-40 is related to poor prognosis in cervical cancer (CC) patients. A prospective biomarker study of 116 patients with CC (FIGO stage Ia: n = 4; Ib: n = 55; II: n = 26; III: n = 26; IV: n = 5) and 152 patients with cervical intraepithelial neoplasia (CIN). The patients received primary surgery, radiotherapy and chemotherapy according to standard guidelines during the period 2001-2004. Seventy patients died during the follow-up period (median 117 months, range 104-131). Serum concentrations of YKL-40 were measured by ELISA. Serum concentrations of YKL-40 were increased (p < .001) in CC patients (median 76 µg/L, IQR 45-148) compared to CIN patients (44 µg/L, IQR 30-61) and healthy women (41 µg/L, IQR 29-58). YKL-40 was elevated (>age-corrected 95th percentile of YKL-40 in healthy women) in 30 (26%) of the CC patients. Univariate Cox analysis demonstrated that YKL-40 (included as a log-transformed continuous variable (base 2)) was associated with recurrence-free survival (RFS) (HR = 1.48, 95% CI: 1.11-1.98, p = .008) and overall survival (OS) (HR = 1.74, 1.44-2.10, p < .0001). Multivariate Cox analysis showed that stage (II + III vs. I: HR = 2.92, 1.37-6.20, p = .005), YKL-40 (HR = 1.35, 1.06-1.73, p = .018) and age (HR = 1.56, 1.21-1.99, p = .0005) were independent prognostic variables of OS. During treatment, a 2-fold increase in YKL-40 compared to baseline level was associated with short RFS (HR = 1.87, 1.27-2.77, p = .0016) and OS (HR = 1.78, 1.26-2.50, p = .0010). Serum YKL-40 is an independent biomarker of OS in patients with cervical cancer.

Relationships between increased circulating YKL-40, IL-6 and TNF-α levels and phenotypes and disease activity of primary Sjögren's syndrome

BACKGROUND

There is now no single score or marker useful for evaluating disease activity of primary Sjögren's syndrome (pSS). This study was designed to explore the associations of circulating YKL-40, interleukin 6 (IL-6) and tumor necrosis factor α (TNF-α) with systemic activity and phenotypes of pSS.

METHODS

This study included 58 pSS patients and 30 healthy controls (HC). The sera were measured by multiplex immunoassay for YKL-40, IL-6 and TNF-α concentrations. The disease activity of pSS patients was evaluated by European league against rheumatism (EULAR) SS disease activity index (ESSDAI). Local severity was assessed in accordance with the Tarpley score.

RESULTS

Serum YKL-40, IL-6 and TNF-α levels significantly elevated in pSS patients compared with those in HC (all P < 0.001). These cytokines correlated with ESSDAI, ESR, CRP, and IgG (all P < 0.05). Serum YKL-40 level correlated markedly with age (r = 0.405, P = 0.002), neutrophil count (r = 0.399, P = 0.002) and neutrophil-to-lymphocyte ratio (NLR) (r = 0.401, P = 0.002), while IL-6 did weakly with NLR (r = 0.296, P = 0.024) and C3 (r = 0.288, 0.036). Serum levels of all three cytokines were substantially lower in patients with eye/mouth dryness vs. those without (all P < 0.05). Additionally, patients with pulmonary, renal involvement or anemia had remarkably higher concentrations of YKL-40 (all P < 0.05), while those with leukocytopenia had lower levels (P = 0.01). Fever or anemia patients showed higher serum concentrations of IL-6 (both P < 0.05), while serum levels of TNF-α were much higher in patients with presence of ANA, anti-SSA or anti-SSB antibodies (All P < 0.05). Serum IL-6 level correlated strongly with YKL-40 (r = 0.452, P < 0.001) and TNF-α (r = 0.743, P < 0.001) in pSS patients. A significant correlation was also found between YKL-40 and TNF-α (r = 0.308, P = 0.022) .

CONCLUSION

The circulating YKL-40, IL-6 and TNF-α levels increase in pSS, and all of them are significantly correlated with indicators (ESSDAI, ESR, CRP, and IgG) for systemic inflammation of pSS. Each cytokine is separately associated with specific pSS phenotype.

Elevated serum YKL-40, IL-6, CRP, CEA, and CA19-9 combined as a prognostic biomarker panel after resection of colorectal liver metastases

Background

The inflammatory biomarkers, YKL-40 and interleukin-6 (IL-6), are elevated in patients with metastatic colorectal cancer. We examined their associations with relapse-free survival and overall survival in combination with serum C-reactive protein (CRP), carcinoembryonic antigen (CEA), and carbohydrate antigen 19–9 (CA19-9) in patients with colorectal liver metastases.

Methods

Altogether 441 consecutive patients undergoing liver resection at Helsinki University Hospital between 1998 and 2013 were included in the study. Pre- and postoperative YKL-40 and IL-6 were determined from serum samples with commercially available enzyme-linked immunosorbent assay (ELISA) kits, and CRP, CEA, and CA19-9 by routine methods. Associations between these biomarkers and relapse-free and overall survival were examined using Cox regression analysis.

Results

Patients with 2–5 elevated biomarkers were at an increased risk of relapse compared to those with 0–1 elevated biomarkers, preoperatively (HR 1.37, 95% CI 1.1–1.72) or postoperatively (HR 1.54, 95% CI 1.23–1.92). Patients with 2–5 elevated biomarkers were also at an increased risk of death compared to those with 0–1 elevated biomarkers, preoperatively (HR 1.76, 95% CI 1.39–2.24) or postoperatively (HR 1.83, 95% CI 1.44–2.33).

Conclusion

The results suggest that a protein panel of the inflammatory biomarkers YKL-40, IL-6, and CRP, and the cancer biomarkers CEA and CA19-9 might identify patients that benefit from more aggressive treatment and surveillance, although the additional value of IL-6 and CRP in this aspect is limited.

Systemic Immune Modulation in Gliomas: Prognostic Value of Plasma IL-6, YKL-40, and Genetic Variation in YKL-40

Background: Complex local and systemic immune dysfunction in glioblastoma (GBM) may affect survival. Interleukin (IL)-6 and YKL-40 are pleiotropic biomarkers present in the tumor microenvironment and involved in immune regulation. We therefore analyzed plasma IL-6, YKL-40, and genetic variation in YKL-40 and explored their ability to distinguish between glioma subtypes and predict survival in GBM. Methods: One hundred fifty-eight patients with glioma WHO grade II-IV were included in the study. Plasma collected at surgery was analyzed for IL-6 and YKL-40 (CHI3L1) by ELISA. CHI3L1 rs4950928 genotyping was analyzed on whole-blood DNA. Results: Neither plasma IL-6 nor YKL-40 corrected for age or rs4950928 genotype could differentiate GBM from lower grade gliomas. GC and GG rs4950928 genotype were associated with lower plasma YKL-40 levels (CC vs. GC, p = 0.0019; CC vs. GG, p = 0.01). Only 10 and 14 out of 94 patients with newly diagnosed GBM had elevated IL-6 or YKL-40, respectively. Most patients received corticosteroid treatment at time of blood-sampling. Higher pretreatment plasma IL-6 was associated with short overall survival (OS) [HR = 1.19 (per 2-fold change), p = 0.042] in univariate analysis. The effect disappeared in multivariate analysis. rs4950928 genotype did not associate with OS [HR = 1.30, p = 0.30]. In recurrent GBM, higher YKL-40 [HR = 2.12 (per 2-fold change), p = 0.0005] but not IL-6 [HR = 0.99 (per 2-fold change), p = 0.92] were associated with short OS in univariate analysis. Conclusion: In recurrent GBM high plasma YKL-40 may hold promise as a prognostic marker. In newly diagnosed GBM perioperative plasma IL-6, YKL-40, and genetic variation in YKL-40 did not associate with survival. Corticosteroid use may complicate interpretation of results.

Elevated plasma YKL-40 and risk of infectious disease: a prospective study of 94665 individuals from the general population

OBJECTIVES

YKL-40 is an acute phase protein elevated in patients with infectious and inflammatory diseases. We tested the hypothesis that baseline elevated YKL-40 is associated with increased risk of future infectious disease in healthy individuals in the general population.

METHODS

We prospectively followed 94 665 individuals from the Danish general population for up to 23 years and analysed for plasma YKL-40 levels (n = 21 584) and CHI3L1 rs4950928 genotype (n = 94 184). Endpoints were any infection, bacterial pneumonia, urinary tract infection, skin infection, sepsis, diarrhoeal disease, and other infections.

RESULTS

For YKL-40 percentile category 91-100% versus 0-33%, the multifactorially and C-reactive protein (CRP) adjusted hazard ratios were 1.71 (95% confidence interval 1.50-1.96; p 4 × 10^-14) for any infection, 1.97 (1.64-2.37; p 4 × 10^-13) for bacterial pneumonia, 1.62 (1.24-2.11; p 0.002) for urinary tract infection, 1.74 (1.31-2.32; p 2 × 10^-4) for skin infection, 1.76 (1.25-2.46; p 0.004) for sepsis, 1.90 (1.29-2.78; p 0.002) for diarrhoeal disease and 2.71 (1.38-5.35; p 0.01) for other infections. In multifactorially and CRP-adjusted models, a twofold increase in YKL-40 was associated with increased risk of all infectious disease endpoints. Mendelian randomization did not support causality, as CHI3L1 rs4950928 was associated with 94% and 190% higher YKL-40 levels (for CG and CC versus GG genotype), but not with increased risk of any infectious disease endpoint.

DISCUSSION

Baseline elevated plasma YKL-40 was not a cause but a strong marker of increased risk of future infectious diseases in individuals in the general population.

Prediction of Unresectability and Prognosis in Patients Undergoing Surgery on Suspicion of Pancreatic Cancer Using Carbohydrate Antigen 19-9, Interleukin 6, and YKL-40

OBJECTIVES

The aim was to determine whether serum levels of carbohydrate antigen (CA) 19-9, interleukin 6 (IL-6), and YKL-40 could identify advanced disease and poor prognosis in pancreatic cancer (PC) patients intraoperatively diagnosed with locally advanced or metastatic disease.

METHODS

Two hundred ninety patients were included with preoperative blood samples. Plasma IL-6 and YKL-40 were determined by enzyme-linked immunosorbent assays.

RESULTS

Interleukin 6 was elevated in patients with unresectable PC compared with resectable PC (P = 0.03). Carbohydrate antigen 19-9 and YKL-40 were similar. Patients with resectable tumors and greater than median preoperative CA 19-9, IL-6, and YKL-40 had shorter overall survival than patients with low levels (CA 19-9: hazard ratio [HR], 1.79; 95% confidence interval [CI], 1.13-2.83; P = 0.01; IL-6: HR, 1.83; 95% CI, 1.20-2.78; P = 0.01; YKL-40: HR, 1.60; 95% CI, 1.02-2.49; P = 0.04). Patients with resectable tumors and 2 or 3 high biomarker levels had significantly reduced overall survival compared with patients with low levels (2 high: HR, 2.97; 95% CI, 1.44-6.10; P = 0.00; 3 high: HR, 3.10; 95% CI, 1.45-6.65; P = 0.00).

CONCLUSIONS

Preoperative levels of CA 19-9, IL-6, and YKL-40 may be useful to identify a subgroup of PC patients with poor prognosis.

Chitinase-like protein YKL-40 correlates with inflammatory phenotypes, anti-asthma responsiveness and future exacerbations

Background

Asthma is a heterogeneous chronic airway disease, which may be classified into different phenotypes. YKL-40 is a chitin-binding glycoprotein with unclear functions, but its expression is associated with inflammation and tissue remodeling. However, few studies have explored whether YKL-40 is associated with inflammatory phenotypes of asthma.

Methods

The study had two parts. Study I (n = 115) was a one-year prospective cohort designed to explore the relationship of serum YKL-40 levels with inflammatory phenotypes of asthma at baseline, and during exacerbations. Study II (n = 62) was a four-week prospective cohort designed to define whether serum YKL-40 levels could predict responses to a fixed anti-asthma regimen. YKL-40, IL-6 and CCL22 levels were detected using ELISA, and a sputum inflammatory panel (including IL-1β, IL-5, IL-8 and TNF-α) was assessed using Luminex-based MILLIPLEX assay.

Results

Study I: Serum YKL-40 levels in non-eosinophilic asthma (NEA) i.e. neutrophilic (47.77 [29.59, 74.97] ng/mL, n = 40) and paucigranulocytic (47.36 [28.81, 61.68] ng/mL, n = 31) were significantly elevated compared with eosinophilic asthma (31.05 [22.41, 51.10] ng/mL, n = 44) (P = 0.015). Serum YKL-40levels positively correlated with blood neutrophils, sputum IL-1β and plasma IL-6 but negatively correlated with serum IgE and blood eosinophils (all P ≤ 0.05). Baseline YKL-40 levels predicted moderate to severe exacerbations within a one-year period (aOR = 4.13, 95% CI = [1.08, 15.83]). Study II: Serum YKL-40 was an independent biomarker of negative responses to anti-asthma regimens (adjusted Odds Ratio [aOR] = 0.82, 95% CI = [0.71, 0.96].

Conclusions

These studies show that YKL-40 is a non-type 2 inflammatory signature for NEA, which could predict responsiveness or insensitivity to anti-asthma medications and more exacerbations. Further studies are needed to assess whether monitoring YKL-40 levels could provide potential implications for clinical relevance.

Electronic supplementary material

The online version of this article (10.1186/s12931-019-1051-9) contains supplementary material, which is available to authorized users.

An association between YKL-40 and type 2 diabetes in psychotic disorders

OBJECTIVE

This study examines if YKL-40 is increased in individuals with psychotic disorders and if elevated YKL-40 levels at baseline is associated with subsequent development of type 2 diabetes.

METHOD

A total of 1383 patients with a diagnosis of schizophrenia or affective psychosis and 799 healthy controls were recruited in the period 2002-2015. Plasma YKL-40 and metabolic risk factors were measured and medication was recorded. Using national registry data, association between baseline risk factors and later development of type 2 diabetes was assessed using Cox proportional hazards models.

RESULTS

Plasma YKL-40 was higher in patients vs. healthy controls also after adjusting for metabolic risk factors, with no difference between the schizophrenia and affective psychosis groups. Patients were diagnosed with type 2 diabetes at a significantly younger age. Multivariate Cox regression analyses showed that elevated YKL-40 (hazard ratio (HR) = 5.6, P = 0.001), elevated glucose (HR = 3.6, P = 0.001), and schizophrenia diagnosis (HR = 3.0, P = 0.014) at baseline were associated with subsequent development of type 2 diabetes.

CONCLUSIONS

Patients with psychotic disorders have at baseline increased levels of YKL-40 beyond the effect of comorbid type 2 diabetes and metabolic risk factors. Elevated YKL-40 level at baseline is associated with later development of type 2 diabetes.

YKL-40 is a local marker for inflammation in patients with pseudoexfoliation syndrome

PURPOSE

To investigate the YKL-40, as a marker of inflammation, in aqueous humor and serum of cataract patients with and without pseudoexfoliation syndrome (PEX).

METHODS

Aqueous humor and serum samples were obtained from 44 patients who underwent phacoemulsification surgery. All patients were divided into two groups: PEX (n = 24) and control (n = 20). YKL-40 levels were measured with enzyme-linked immunosorbent assay (ELISA). The differences between the groups were assessed by using Chi-square and independent sample t-tests. The Pearson correlation coefficient was used to evaluate the correlation between variables.

RESULTS

There was a significant difference between the mean YKL-40 levels in the aqueous humor of PEX group (112.0 ± 35.8 ng/mL) and control subjects (88.2 ± 30.6 ng/mL) (P = 0.025). However, the difference between the mean YKL-40 levels in the serum of PEX group (53.5 ± 29.1 ng/mL) and control subjects (44.6 ± 30.2 ng/mL) was non-significant (P = 0.326). The correlation between aqueous humor and serum YKL-40 concentrations was significant in both the groups (r = 0.833, P < 0.001; r = 0.840, P < 0.001, respectively).

CONCLUSIONS

Increased aqueous humor levels of YKL-40 demonstrate that it is local, but not a systemic marker for inflammation in patients with PEX.

Elevation of YKL-40 in the CSF of Anti-NMDAR Encephalitis Patients Is Associated With Poor Prognosis

Objective: Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis predominantly affects children and young women; the disease can have a multistage presentation and exhibit a wide variety of neuropsychiatric features. This study aimed to investigate the profile of YKL-40 (Chitinase 3-like 1) in anti-NMDAR encephalitis patients and evaluate its association with modified Rankin Scale (mRS) scores and expression of inflammatory cytokines.

Methods: A total of 66 patients were enrolled in this study, 33 with anti-NMDAR encephalitis, 13 with viral meningitis and 20 with non-inflammatory neurological disease. Patients were evaluated to determine mRS scores at disease onset and at the 3 month follow-up; cerebrospinal fluid (CSF) samples were collected in the meantime. CSF levels of YKL-40 and cytokines (TNF-α, IL-6, IL-10) were measured by enzyme-linked immunosorbent assay.

Results: CSF levels of YKL-40 and inflammatory cytokines (TNF-α, IL-6, IL-10) were all more highly elevated in patients with anti-NMDAR encephalitis at the acute stage of disease compared with the controls. Levels of CSF YKL-40 were correlated with levels of IL-6 both at disease onset and at the 3 month follow-up. Changes in YKL-40 levels were significantly correlated with improved mRS scores in patients with anti-NMDAR encephalitis.

Conclusion: Our study suggests that CSF levels of YKL-40 in patients with anti-NMDAR encephalitis were increased and correlated with clinical mRS scores. This may be reflective of the underlying neuroinflammatory process. YKL-40 demonstrates potential as a possible biomarker for the prognosis of anti-NMDAR encephalitis.

A Novel Biomarker in Diabetic Macular Edema with Serous Retinal Detachment: Serum Chitinase-3-Like Protein 1

PURPOSE

To determine whether serum chitinase-3-like protein 1 (CHI3L1) and interleukin-6 (IL-6) levels correlate with serous retinal detachment (SRD) in diabetic macular edema (DME) using spectral-domain optical coherence tomography (SD-OCT).

METHODS

In this cross-sectional case-control study, 394 patients (treatment-naive DME patients, n = 218; diabetic patients without DME, n = 96; nondiabetic controls, n = 80) were included in the study. Eyes were classified according to SD-OCT features of DME: SRD, cystoid macular edema (CMO), and diffuse retinal thickness (DRT). Serum concentrations of CHI3L1 and IL-6 were analyzed using enzyme-linked immunosorbent assay.

RESULTS

Serum CHI3L1 and IL-6 levels were significantly higher in DME with SRD compared to patients with CMO and DRT (p < 0.001 for all groups). Multivariate regression analysis showed that CHI3L1 and IL-6 had a stronger influence on the presence of SRD in DME (r = 1.162, p = 0.026, and r = 1.242, p = 0.016, respectively). Serum concentration of CHI3L1 was significantly correlated with that of IL-6 (r = 0.386, p = 0.0015).

CONCLUSIONS

Our data suggest that serum concentrations of CHI3L1 and IL-6 are involved in the process of SRD in DME. CHI3L1 can be investigated further as a new diagnostic biomarker for DME with SRD.

YKL-40: A biomarker for early nephropathy in type 2 diabetic patients and its association with inflammatory cytokines

Diabetic Nephropathy (DN) is an important cause of morbidity and death amongst diabetes. Persistent micro and macroalbuminuria are well known predictors of DN leading to progressive end-stage renal disease. However, albuminuria has several limitations. Increasing evidences show that YKL-40 is highly expressed in variety of inflammatory diseases and also recognized as a non-invasive prognostic biomarker for inflammation. In the present study, we measured plasma YKL-40 levels in different stages of albuminuria and assessed its diagnostic accuracy as a biomarker for DN and correlated with different families of circulatory cytokines. A total of 306 subjects were recruited and divided into three groups [Group-I, control (n = 83), Group-II, Normoalbuminuria (n = 81), Group-III, DN (n = 142)]. Group-III is further subdivided into: Group-IIIa, microalbuminuria (n = 73), Group-IIIb, macroalbuminuria (n = 69). The median levels of YKL-40 (p = 0.001) showed a marked stepwise increase from normo to macroalbuminuria and positively correlated with eGFR. The AUC_ROC for YKL-40 was found to be high [0.95; (95% CI: 0.88-1.0)], when compared to other acute phase markers. Plasma YKL-40 showed a positive correlation with LIGHT/TNFSF14, sIL-6Ra, gp130/sIL-6Rβ, IFN-β, IL-8, TNFSF14, sCD-30 and eGFR meanwhile a negative correlation with TWEAK/TNFSF12, IL-7 like cytokine and IFN-λ2. Plasma YKL-40 could be a potential biomarker for early diagnosis of incipient DN among South Indian population.

Elevated serum YKL-40 correlates with clinical characteristics in patients with polymyositis or dermatomyositis

Background

Serum YKL-40 has been proved to be a promising biomarker for estimating the disease activity of several autoimmune diseases. However, its utility in polymyositis or dermatomyositis has not been established. The aim of this study was to investigate the utility of YKL-40 in patients with polymyositis/dermatomyositis.

Method

Patients with definite polymyositis/dermatomyositis who visited the Second People’s Hospital of Wuxi between April 2016 and March 2017 were prospectively enrolled. Eighty-seven healthy individuals were set as a control. Serum YKL-40 of all participants was determined using ELISA. The associations between YKL-40 and clinical characteristics of polymyositis/dermatomyositis were analysed using the Student’s t-test, Mann-Whitney test and receiver operating characteristic curve analysis.

Results

A total of 99 patients with polymyositis/dermatomyositis were enrolled. The patients with polymyositis/dermatomyositis had significantly higher serum YKL-40 concentration. Patients with interstitial lung disease had significantly higher YKL-40 concentration than those without. Serum YKL-40 was positively correlated with myositis disease activity assessment visual analogue scale, C-reactive protein, erythrocyte sedimentation rate and ferritin. The area under receiver operating characteristic curve of YKL-40 for identifying interstitial lung disease was 0.82.

Conclusions

Serum YKL-40 is a useful biomarker for estimating disease activity or severity of polymyositis/dermatomyositis.

Rheumatoid Arthritis Magnetic Resonance Imaging Score Predicts Therapy Response: Results of the German ArthroMark Cohort

OBJECTIVE

Markers for treatment response in rheumatoid arthritis (RA) are lacking. The aim of the study was to assess the performance of the RA magnetic resonance imaging (MRI) scoring system (RAMRIS) in combination with serum biomarkers to predict response to methotrexate (MTX) treatment in therapy-naive patients with early RA by using high-field MRI.

METHODS

Twenty-eight patients with RA were prospectively assessed with baseline 3-T MRI of the clinical dominant hand, 3 and 6 months after MTX. The patients met the 2010 American College of Rheumatology/European League Against Rheumatism (EULAR) criteria [average age 56.8 yrs (range 39-74); positive for rheumatoid factor and/or anticyclic citrullinated peptide antibodies; disease duration < 6 mos (range 2-23 weeks)]. RAMRIS and serum biomarkers consisting of various experimental proteins including receptor activator of nuclear factor-κB ligand (RANKL) were obtained. Remission or treatment response was defined according to EULAR. To adjust for intrapersonal correlation, generalized linear mixed models were used.

RESULTS

Treatment response at 3 months was associated to low RAMRIS erosion subscores and low total RAMRIS scores (p = 0.019 and 0.03, respectively). Remission at 6 months was associated to low RANKL levels (p = 0.033). In multivariate analyses, response at 3 and 6 months was predicted more accurately with the inclusion of total RAMRIS score, RAMRIS synovitis subscore at the second metacarpophalangeal (MCP) joint, or a combination of the two (p value likelihood ratio test = 0.035, 0.035, and 0.041, respectively). Remission was more accurately predicted with inclusion of RANKL, with no significant predictive effect of MRI.

CONCLUSION

Baseline total RAMRIS can predict EULAR response. RAMRIS synovitis subscore at the second MCP joint and RANKL are associated with response and remission, respectively.

The tumor microenvironment promotes cancer progression and cell migration

The tumor microenvironment contributes to cancer progression, in part through interactions between tumor and normal stromal cells. This study analyzed morphological and molecular changes induced in co-cultured human fibroblasts (HFs) and the MG-63 osteosarcoma cell line. Co-cultured cell monolayers were morphologically analyzed using high resolution scanning electron microscopy (HR-SEM), and trans-well assays were performed to assess cell migration and invasion. Proteins involved in inflammatory responses, cancer cell invasion, and angiogenesis were assessed using western blotting. HR-SEM showed progressive spatial orientation loss by fibroblasts in contact with MG-63s, while MG-63s proliferated rapidly and invaded HF space. Trans-well assays showed enhanced MG-63 migration in the presence of HFs. IL-6 expression was increased in co-cultured HFs, possibly stimulated by TNF-α. HFs do not normally express YKL-40 but did so in co-culture. Band densitometric analyses showed that increasing YKL-40 expression was followed by VEGF overexpression, especially in MG-63s. Finally, our results confirmed fibroblasts as the main matrix metalloproteinase source in this tumor microenvironment. Our study sheds new light on how tumor-stroma interactions promote tumor development and progression, and may support identification of novel anti-cancer therapeutics.

Prognostic and predictive value of YKL-40 in stage IIB-III melanoma

This study investigates the prognostic and predictive value of YKL-40 in stage IIB-III melanoma patients who were randomized to adjuvant interferon α-2b (IFN) or observation. Serum YKL-40 was determined postoperatively in patients from the Nordic IFN Trial (n=602), EORTC 18952 (n=246), and EORTC 18991 (n=386) (EORTC, European Organisation for Research and Treatment of Cancer). YKL-40 protein expression was determined in 300 tissue sections of primary melanoma or lymph node metastases from 204 Danish patients from the Nordic IFN Trial. Multivariate Cox analysis (including sex, age, stage, ulceration, YKL-40) showed that elevated baseline YKL-40 level was associated with shorter overall survival (OS) in observation groups from the Nordic IFN Trial and EORTC 18952 [hazard ratio (HR)=1.33; 95% confidence interval (CI) 1.01-1.74; P=0.04], but not in the interferon groups (1-year IFN: HR=0.97; 95% CI 0.76-1.25; P=0.83; 2-years IFN: HR=1.06; 95% CI 0.83-1.34; P=0.64). During follow-up, increases in YKL-40 were significantly associated with shorter OS, but not with recurrence-free survival in univariate analysis. YKL-40 expression was stronger in tumor-associated macrophages than melanoma cells in primary melanoma. High YKL-40 expression in macrophages in lymph node metastases was associated with shorter OS in the observation group (HR=2.76; 95% CI: 1.13-6.76, P=0.02), but not in the interferon-treated groups. YKL-40 was an independent prognostic biomarker of OS in melanoma patients stage IIB-III. High serum YKL-40 in poor-prognosis patients may originate from macrophages in the tumor microenvironment and the melanoma cells. Furthermore, we hypothesize that elevated serum YKL-40 after surgery may predict the efficacy of adjuvant IFN treatment.

Circulating serum interleukin-6, serum chitinase-3-like protein-1, and plasma vascular endothelial growth factor are not predictive for remission and radiographic progression in patients with early rheumatoid arthritis: post-hoc explorative and validation studies based on the CIMESTRA and OPERA trials

OBJECTIVE

To investigate serum interleukin-6 (IL-6), serum chitinase-3-like protein-1 (YKL-40), and plasma vascular endothelial growth factor (VEGF) as measures of disease activity and predictors of clinical remission and radiographic progression in two early rheumatoid arthritis (RA) randomized controlled trials (RCTs).

METHOD

Treatment-naïve patients with early RA (< 6 months' duration) and active disease, participating in two investigator-initiated RCTs, were treated according to a predefined treat-to-target algorithm aiming at inflammatory control, using methotrexate (MTX) + cyclosporine versus MTX + placebo (CIMESTRA study, n = 150, 5 year follow-up) or MTX + adalimumab versus MTX + placebo (OPERA study, n = 180, 2 year follow-up). The 28-joint Disease Activity Score (DAS28) and conventional radiography [bilateral hands and feet at baseline, 2 years and 5 years (only CIMESTRA)] were obtained at baseline and during follow-up. Serum IL-6, serum YKL-40, and plasma VEGF were measured in baseline blood samples and during follow-up. Hypotheses regarding the biomarkers' relation with DAS28 and ability to predict clinical remission (DAS28 < 2.6) and radiographic progression (change in total Sharp van der Heijde score ≥ 2) were generated in CIMESTRA and validated in OPERA, by Spearman's correlation and logistic regression analyses.

RESULTS

Baseline IL-6, YKL-40, and VEGF correlated significantly with DAS28 in CIMESTRA (r = 0.50, r = 0.36, r = 0.36, respectively, all p < 0.01) and these results were confirmed in OPERA patients (r = 0.52, p < 0.01; r = 0.18, p = 0.01; r = 0.23, p = 0.002, respectively). None of the biomarkers (absolute values or change) was predictive of clinical remission or radiographic progression at 2 or 5 years in either study.

CONCLUSION

Serum IL-6, serum YKL-40, and plasma VEGF were significantly correlated with DAS28 at baseline, but did not have consistent predictive value for clinical remission or radiographic progression in two early RA RCTs.

Chitinase 3-like 1 secreted by peritumoral macrophages in esophageal squamous cell carcinoma is a favorable prognostic factor for survival

AIM

To identify whether chitinase 3-like 1 (CHI3L1) serves as a suitable biomarker for the prognosis of esophageal squamous cell carcinoma (ESCC) and to analyze this protein’s cellular source.

METHODS

An ELISA was conducted to detect the concentration of CHI3L1 in the serum of 150 ESCC patients diagnosed between January 2001 and February 2005. The prognostic relevance of CHI3L1 was evaluated by a Kaplan-Meier and Cox regression analysis. The immunohistochemistry was reanalyzed, and fluorescent staining was utilized to explore the cellular origins of CHI3L1. We stimulated monocyte-derived macrophages (MDMs) with either IL-6 or the supernatant of the ESCC cell line Eca-109 and later investigated the level of CHI3L1 by qPCR and ELISA.

RESULTS

The level of serum CHI3L1 was higher in older patients (≥ 60) than in patients under the age of 60 (P = 0.001). The patients with higher levels of CHI3L1 had a significantly shorter overall survival, whereas the traditional markers, carcinoembryonic antigen and squamous cell carcinoma antigen, were less effective (P > 0.05). A multivariate Cox analysis (P = 0.001) indicated that CHI3L1 was an independent prognostic factor for ESCC patients. Peritumoral macrophages in ESCC exhibited high levels of CHI3L1. Interleukin-6 (IL-6) and the supernatant of Eca-109 containing IL-6 stimulated MDMs to secrete CHI3L1. The serum concentration of CHI3L1 in the ESCC patients showed a weak correlation with the laboratory inflammatory parameters neutrophil (NEU, P = 0.045), neutrophil/lymphocyte rate (NLR, P = 0.016), and C-reactive protein (CRP, P < 0.001).

CONCLUSION

Our study first established a connection between the pretreated CHI3L1 and patients with ESCC, and the serum CHI3L1 was primarily secreted by ESCC-surrounded macrophages.

Mortality prediction in stable hemodialysis patients is refined by YKL-40, a 40-kDa glycoprotein associated with inflammation

Chronic inflammation contributes to increased mortality in hemodialysis (HD) patients. YKL-40 is a novel marker of inflammation, tissue remodeling, and highly expressed in macrophages inside vascular lesions. Elevated levels of YKL-40 have been reported for HD patients but how it integrates into the proinflammatory mediator network as a predictor of mortality remains elusive. We studied serum YKL-40, Interleukin-6 (IL-6), high-sensitivity C-reactive protein, monocyte chemotactic protein-1 (MCP-1), and interferon-gamma induced protein-10 (IP-10) in 475 chronic hemodialysis patients. Patients were followed for mortality for a median of 37 [interquartile range: 25-49] months and checked for interrelation of the measured mediators. To plot cumulative incidence functions, patients were stratified into terciles per YKL-40, IL-6, MCP-1, and IP-10 levels. Multivariable Cox regression models were built to examine associations of YKL-40, IP-10, and MCP-1 with all-cause and cause-specific mortality. Net reclassification improvement was calculated for the final models containing YKL-40 and IL-6. Increased YKL-40 was independently associated with age, IP-10, and IL-6 serum levels. After adjustment for demographic and laboratory parameters, comorbidities, and IL-6, only YKL-40 significantly improved risk prediction for all-cause (hazard ratio 1.4; 95% confidence interval 1.1-1.8) and cardiovascular mortality (hazard ratio 1.5; 95% confidence interval 1.03-2.2). Thus, in contrast to other biomarkers of aberrant macrophage activation, YKL-40 reflects inflammatory activity, which is not covered by IL-6. Mechanistic and prospective studies are needed to test for causal involvement of YKL-40 and whether it might qualify as a therapeutic target.

Glycoprotein YKL-40: A potential biomarker of disease activity in rheumatoid arthritis during intensive treatment with csDMARDs and infliximab. Evidence from the randomised controlled NEO-RACo trial

OBJECTIVE

YKL-40, a chitinase-like glycoprotein associated with inflammation and tissue remodeling, is produced by joint tissues and recognized as a candidate auto-antigen in rheumatoid arthritis (RA). In the present study, we investigated YKL-40 as a potential biomarker of disease activity in patients with early RA at baseline and during intensive treatment aiming for early remission.

METHODS

Ninety-nine patients with early DMARD-naïve RA participated in the NEO-RACo study. For the first four weeks, the patients were treated with the combination of sulphasalazine, methotrexate, hydroxychloroquine and low dose prednisolone (FIN-RACo DMARD combination), and subsequently randomized to receive placebo or infliximab added on the treatment for further 22 weeks. Disease activity was evaluated using the 28-joint disease activity score and plasma YKL-40 concentrations were measured by immunoassay.

RESULTS

At the baseline, plasma YKL-40 concentration was 57 ± 37 (mean ± SD) ng/ml. YKL-40 was significantly associated with the disease activity score, interleukin-6 and erythrocyte sedimentation rate both at the baseline and during the 26 weeks' treatment. The csDMARD combination decreased YKL-40 levels already during the first four weeks of treatment, and there was no further reduction when the tumour necrosis factor-α antagonist infliximab was added on the combination treatment.

CONCLUSIONS

High YKL-40 levels were found to be associated with disease activity in early DMARD-naïve RA and during intensive treat-to-target therapy. The present results suggest YKL-40 as a useful biomarker of disease activity in RA to be used to steer treatment towards remission.

New Insights Into the Relationship Between Chitinase-3-Like-1 and Asthma

PURPOSE OF REVIEW

CHI3L1 (also known as YKL-40), a member of "mammalian chitinase-like proteins," is a serum protein lacking enzymatic activity. Although the protein is highly conserved in mammals, a consensus regarding its role in human pathologies is currently lacking. In an attempt to shed light on the many physiological functions of the protein, specifically with regard to asthma, a comprehensive overview of recent studies is provided.

RECENT FINDINGS

In asthma, CHI3L1 is secreted from macrophages and airway epithelial cells through an IL-13 related mechanism. Th2-associated inflammatory responses due to allergen exposure, resulting in airway hyper-responsiveness and smooth muscle contraction, play a role in tissue remodeling. The importance of CHI3L1 in initiation and development of asthma is not limited to its involvement in highly orchestrated events of inflammatory cytokines but further research is needed for further elucidation. Levels of the protein are associated with severity for numerous pathologies, including asthma, suggesting limited specificity as a biomarker.

The Effects of Ferulic Acid Against Oxidative Stress and Inflammation in Formaldehyde-Induced Hepatotoxicity

This study was designed to elucidate the protective effects of ferulic acid (FA) on formaldehyde-induced hepatotoxicity by measuring some routine biochemical parameters, cytokine levels, and oxidative stress-related parameters in addition to YKL-40 in male Wistar albino rats. Tissue superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) activities, and tissue malondialdehyde (MDA) levels were measured. Also, serum YKL-40, TNF-α, IL-6, IL-1β, IL-8, total protein, albumin, total bilirubin concentrations, and AST, ALT, ALP, and LDH activities were measured. Histological specimens were examined in light microscopy. Formaldehyde significantly increased tissue MDA, and serum cytokine levels and also decreased activities of antioxidant enzymes. FA treatment decreased MDA and cytokine levels and increased activities of antioxidant enzymes. FA also alleviated degeneration due to formaldehyde toxicity. We suggested that FA can be used as a promising hepatoprotective agent against formaldehyde toxicity because of the obvious beneficial effects on oxidative stress parameters.

Chitinase 3-like-1 deficient donor splenocytes accentuated the pathogenesis of acute graft-versus-host diseases through regulating T cell expansion and type I inflammation

Acute graft-versus-host disease (aGVHD) is a major complication following transplantation, limiting the success of this therapy. Chitinase 3-like-1 (CHI3L1), a member of the glycosyl hydrolase 18 family, plays a critical role in bacterial infections, allergic disease and a variety of malignancies. Here, we investigated whether CHI3L1 could affect the pathogenesis of aGVHD in a mouse allo-HCT model. In this study, we show that CHI3L1 deficiency in donor T cells increased the severity of aGVHD through enhancing systemic and local inflammation. In addition, we found that aGVHD induced by CHI3L1-knockout (CHI3L1-KO) donors resulted in massive expansion of donor CD3⁺ T cells, release of Th1-related cytokines and chemokines, and significant inhibition of CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Tregs) without changing the suppressive ability of donor Tregs remarkably. Expression of PERK1/2 and PAkt increased both in the skin and intestine from CHI3L1-KO splenocytes-treated aGVHD mice. Moreover, at mRNA and protein levels, we defined several molecules that may account for the enhanced ability of CHI3L1-KO splenocytes to migrate into target organs and produce Th1-related cytokines and chemokines, such as CXCL9, CXCL11, IFN-γ and TNF-α. Therefore, these results imply that CHI3L1 levels in donor cells may be related to the risk of aGVHD and targeting CHI3L1 may be a promising clinical strategy to control aGVHD.

Prognostic Biomarkers for Hodgkin Lymphoma

The prognosis of patients with classical Hodgkin lymphoma following chemo- and radiotherapy has been excellent during the last 4 decades. However, the development of secondary malignancies is of major concern. Therefore, the reduction of radiotherapy application is a major objective of ongoing clinical trials. De-escalation of treatment may increase the risk of relapses and thus may lead to reappearance of prognostic factors. Prognostic biomarkers might help to identify patients who are at increased risk of relapse. This review summarizes the current knowledge about potential prognostic biomarkers for patients with classical Hodgkin lymphoma.

Increased Obesity-Associated Circulating Levels of the Extracellular Matrix Proteins Osteopontin, Chitinase-3 Like-1 and Tenascin C Are Associated with Colon Cancer

BACKGROUND

Excess adipose tissue represents a major risk factor for the development of colon cancer with inflammation and extracellular matrix (ECM) remodeling being proposed as plausible mechanisms. The aim of this study was to investigate whether obesity can influence circulating levels of inflammation-related extracellular matrix proteins in patients with colon cancer (CC), promoting a microenvironment favorable for tumor growth.

METHODS

Serum samples obtained from 79 subjects [26 lean (LN) and 53 obese (OB)] were used in the study. Enrolled subjects were further subclassified according to the established diagnostic protocol for CC (44 without CC and 35 with CC). Anthropometric measurements as well as circulating metabolites and hormones were determined. Circulating concentrations of the ECM proteins osteopontin (OPN), chitinase-3-like protein 1 (YKL-40), tenascin C (TNC) and lipocalin-2 (LCN-2) were determined by ELISA.

RESULTS

Significant differences in circulating OPN, YKL-40 and TNC concentrations between the experimental groups were observed, being significantly increased due to obesity (P<0.01) and colon cancer (P<0.05). LCN-2 levels were affected by obesity (P<0.05), but no differences were detected regarding the presence or not of CC. A positive association (P<0.05) with different inflammatory markers was also detected.

CONCLUSIONS

To our knowledge, we herein show for the first time that obese patients with CC exhibit increased circulating levels of OPN, YKL-40 and TNC providing further evidence for the influence of obesity on CC development via ECM proteins, representing promising diagnostic biomarkers or target molecules for therapeutics.

New insights on chitinases immunologic activities

Mammalian chitinases and the related chilectins (ChiLs) belong to the GH18 family, which hydrolyse the glycosidic bond of chitin by a substrate-assisted mechanism. Chitin the fundamental component in the coating of numerous living species is the most abundant natural biopolymer. Mounting evidence suggest that the function of the majority of the mammalian chitinases is not exclusive to catalyze the hydrolysis of chitin producing pathogens, but include crucial role specific in the immunologic activities. The chitinases and chitinase-like proteins are expressed in response to different proinflammatory cues in various tissues by activated macrophages, neutrophils and in different monocyte-derived cell lines. The mechanism and molecular interaction of chitinases in relation to immune regulation embrace bacterial infection, inflammation, dismetabolic and degenerative disease. The aim of this review is to update the reader with regard to the role of chitinases proposed in the recent innate and adaptive immunity literature. The deep scrutiny of this family of enzymes could be a useful base for further studies addressed to the development of potential procedure directing these molecules as diagnostic and prognostic markers for numerous immune and inflammatory diseases.

Serum YKL-40 and gestational diabetes - an observational cohort study

To examine serum YKL-40 in women developing gestational diabetes mellitus (GDM). In the present large observational cohort study of 1179 pregnant women, we determined serum YKL-40 four times during pregnancy (at gestational age 12, 20, 25, and 32 weeks). Pregnancy outcome was obtained from medical records. Sixty-eight women (5.8%) developed GDM. Serum YKL-40 increased from gestational age (GA) 12 weeks and the following weeks in the women who developed GDM and was independent of BMI, parity, and maternal age (OR = 2.69, 95% CI: 1.45-5.00, p = 0.002). No association was found between serum YKL-40 and the oral glucose tolerance test results. In conclusion, YKL-40 significantly increased in pregnant women with GDM compared with women without GDM, probably reflecting the low-grade inflammation of GDM. However, we did not find an association between serum concentrations of YKL-40 in early pregnancy and the development of GDM and thus we conclude that YKL-40 alone is not usable as a biomarker for early prediction of GDM.

YKL-40 in allogeneic hematopoietic cell transplantation after AML and myelodysplastic syndrome

YKL-40, also called chitinase-3-like-1 protein, is an inflammatory biomarker that has been associated with disease severity in inflammatory and malignant diseases, including AML, multiple myeloma and lymphomas. The objective of the current study was to assess the prognostic value of pretransplant recipient and donor plasma YKL-40 concentrations in patients with AML (n=624) or myelodysplastic syndrome (n=157) treated with allogeneic hematopoietic cell transplantation (HCT). In recipients, the plasma YKL-40 concentrations were increased when the HCT-comorbidity index was ⩾5 (P=0.028). There were no significant associations between plasma YKL-40 concentrations in recipients and any outcome measures. In donors with YKL-40 plasma concentrations above the age-adjusted 95th percentile, a trend toward increased grade II-IV acute GvHD in recipients was observed (adjusted hazard ratio 1.39 (95% confidence interval 1.00-1.94), P=0.050), with no significant associations with overall survival, treatment-related mortality or relapse. In conclusion, our study shows that YKL-40 does not aid risk stratification of patients undergoing allogeneic HCT, but suggests that YKL-40 may aid donor selection when multiple, otherwise equal, donors are available.

The exercise-regulated myokine chitinase-3-like protein 1 stimulates human myocyte proliferation

AIM

Chitinase-3-like protein 1 (CHI3L1) is involved in tissue remodelling and inflammatory processes. Plasma levels are elevated in patients with insulin resistance and T2DM. We recently showed that CHI3L1 and its receptor protease-activated receptor 2 (PAR-2) are expressed in skeletal muscle. Activation of PAR-2 by CHI3L1 protects against TNF-α-induced inflammation and insulin resistance. However, the effect of exercise on CHI3L1 and PAR-2 signalling remains unknown. The aim of this work was to study the impact of exercise on CHI3L1 production and the effect of CHI3L1/PAR-2 signalling on skeletal muscle growth and repair.

METHODS

Three human exercise studies were used to measure CHI3L1 plasma levels (n = 32). In addition, muscle and adipose tissue CHI3L1 mRNA expression was measured in response to acute and long-term exercise (n = 24). Primary human skeletal muscle cells were differentiated in vitro, and electrical pulse stimulation was applied. In addition, myoblasts were incubated with CHI3L1 protein and activation of MAP kinase signalling as well as proliferation was measured.

RESULTS

Circulating CHI3L1 levels and muscle CHI3L1 mRNA were increased after acute exercise. In addition, CHI3L1 mRNA expression as well as CHI3L1 secretion was enhanced in electrically stimulated cultured myotubes. Incubation of cultured human myoblasts with CHI3L1 protein leads to a strong activation of p44/42, p38 MAPK and Akt as well as enhanced myoblast proliferation.

CONCLUSION

Our findings suggest that CHI3L1 is induced by acute exercise and that CHI3L1/PAR-2 signalling activates myocyte proliferation, which is important for restructuring of skeletal muscle in the response to exercise training.

CHI3L1 nuclear localization in monocyte derived dendritic cells

Chitinase-3-like-1 protein (CHI3L1) is a glycosyl hydrolase (GH) highly expressed in a variety of inflammatory diseases at infectious and non-infectious etiology. CHI3L1 is produced by a wide variety of cells including monocyte-derived macrophages cell lines such as polarized M1 and M2 type macrophages, osteoclasts and Kupffer cells. In this study we have examined the expression of CHI3L1 during the differentiation and maturation of dendritic cells. Magnetically-isolated peripheral blood monocytes were differentiated toward immature DCs (iDC) and mature DCs (mDCs) through a combination of factors and cytokines. Our result showed, for the first time, that CHI3L1 is expressed during the process of differentiation and maturation of dendritic cells in time dependent manner. Furthermore, the CHI3L1 is evenly distributed in cytoplasm and in the nucleus of both the iDCs and mDCs. These results suggest that CHI3L1 may play crucial role in the DCs immunoresponse.

Circulating and Tissue Expression Levels of YKL-40 in Renal Cell Cancer

PURPOSE

Blood levels of YKL-40 are elevated in various malignancies and other inflammatory diseases. Higher YKL-40 levels have consequently been shown to correlate with poor prognosis in several cancers. We investigated the prognostic value of circulating and tissue levels of YKL-40 in renal cell cancer.

MATERIALS AND METHODS

Preoperative YKL-40 serum/plasma levels were determined in 222 surgically treated patients with renal cell cancer and in 35 controls. Postoperative serum samples were analyzed in 19 of the 222 renal cell cancer cases. Gene expression levels were assessed in 101 renal cell cancer frozen tissue samples using quantitative real-time reverse transcriptase-polymerase chain reaction. Finally immunohistochemical analysis was done in 37 renal cell cancer cases to assess tissue localization of YKL-40. Results were correlated with clinicopathological and followup data.

RESULTS

YKL-40 serum but not tissue gene expression levels were higher in patients with renal cell cancer compared to controls (p = 0.050). Serum YKL-40 levels significantly increased following nephrectomy (p <0.001). High circulating YKL-40 concentrations were independently associated with shorter survival in the serum and plasma cohorts. YKL-40 gene expression did not correlate with patient prognosis.

CONCLUSIONS

Preoperatively elevated circulating levels of YKL-40 predict survival in patients treated with nephrectomy for renal cell cancer independently of levels determined in serum or plasma. Tumor cells do not seem to be the main source of increased serum/plasma YKL-40 levels in patients with renal cell cancer.

Changes in the gene expression of co-cultured human fibroblast cells and osteosarcoma cells: the role of microenvironment

BACKGROUND

The progression of malignant tumors does not depend exclusively on the autonomous properties of cancer cells; it is also influenced by tumor stroma reactivity and is under strict microenvironmental control. By themselves, stromal cells are not malignant, and they maintain normal tissue structure and function. However, through intercellular interactions or by paracrine secretions from cancer cells, normal stromal cells acquire abnormal phenotypes that sustain cancer cell growth and tumor progression. In their dysfunctional state, fibroblast and immune cells produce chemokines and growth factors that stimulate cancer cell growth and invasion. In our previous work, we established an in vitro model based on a monolayer co-culture system of healthy human fibroblasts (HFs) and human osteosarcoma cells (the MG-63 cell line) that simulates the microenvironment of tumor cells and healthy cells. The coexistence between MG-63 cells and HFs allowed us to identify the YKL-40 protein as the main marker for verifying the influence of tumor cells grown in contact with healthy cells.

METHODS

In this study, we evaluated the interactions of HFs and MG-63 cells in a transwell co-culture system over 24 h, 48 h, 72 h, and 96 h. We analyzed the contributions of these populations to the tumor microenvironment during cancer progression, as measured by multiple markers. We examined the effect of siRNA knockdown of YKL-40 by tracking the subsequent changes in gene expression within the co-culture. We validated the expression of several genes, focusing on those involved in cancer cell invasion, inflammatory responses, and angiogenesis: TNF alpha, IL-6, MMP-1, MMP-9, and VEGF. We compared the results to those from a transwell co-culture without the YKL-40 knockdown.

RESULTS

In a pro-inflammatory environment promoted by TNF alpha and IL-6, siRNA knockdown of YKL-40 caused a down-regulation of VEGF and MMP-1 expression in HFs.

CONCLUSIONS

These findings demonstrated that the tumor microenvironment has an influence on the gene expression of healthy surrounding tissues and on the process of tumorigenicity and it is emerging as attractive targets for therapeutic strategies.

The impact of acute aerobic exercise on chitinase 3-like protein 1 and intelectin-1 expression in obesity

Chitinase 3-like 1 (CHI3L1) and intelectin 1 (ITLN-1) recognize microbial N-acetylglucosamine polymer and galactofuranosyl carbohydrates, respectively. Both lectins are highly abundant in plasma and seem to play pro- and anti-inflammatory roles, respectively, in obesity and inflammatory-related illnesses. The aim of this study was to examine whether plasma levels of these lectins in obese subjects are useful for monitoring inflammatory conditions immediately influenced by acute aerobic exercise. Plasma interleukin-6, a pro-inflammatory cytokine, was also examined. Twenty-two (11 obese and 11 normal-weight) healthy subjects, ages 18-30 years, were recruited to perform a 30 min bout of acute aerobic exercise at 75% VO2max. We confirmed higher baseline levels of plasma CHI3L1, but lower ITLN-1, in obese subjects than in normal-weight subjects. The baseline levels of CHI3L1 were negatively correlated with cardiorespiratory fitness (relative VO2max). However, when controlled for BMI, the relationship between baseline level of CHI3L1 and relative VO2max was no longer observed. While acute aerobic exercise elicited an elevation in these parameters, we found a lower ITLN-1 response in obese subjects compared to normal-weight subjects. Our study clearly indicates that acute aerobic exercise elicits a pro-inflammatory response (e.g. CHI3L1) with a lower anti-inflammatory effect (e.g. ITLN-1) in obese individuals. Furthermore, these lectins could be predictors of outcome of exercise interventions in obesity-associated inflammation.

Plasma YKL-40 during pregnancy and gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is characterised by hyperglycaemia during pregnancy. The clinical circumstances involved in the development of GDM leaves the patient at a high risk of the subsequent development of type 2 diabetes. Plasma levels of the inflammation marker YKL-40 are elevated in type 2 diabetes and correlate with fasting plasma glucose levels and insulin resistance in patients with type 2 diabetes. With the present study we aimed to determine if pregnancy (and associated insulin resistance) with or without GDM affects plasma YKL-40 levels. Plasma from women diagnosed with GDM and healthy normal glucose-tolerant pregnant women (non-GDM) was obtained at the third trimester of pregnancy and again 3-4 months following delivery, and levels of YKL-40 and interleukin 6 (IL-6; known to regulate YKL-40) were measured. Plasma YKL-40 levels were similarly low during pregnancy in both groups and increased significantly after delivery, but remained lower in the GDM group compared with the non-GDM group postpartum. In contrast, plasma IL-6 levels were not affected by pregnancy or diagnosis of GDM, Nevertheless, YKL-40 levels were associated with IL-6 levels in the non-GDM group (but not in the GDM group). Pregnancy seems to be associated with a temporary reduction in circulating YKL-40, which increases after delivery, but to a much lesser extent in women with GDM than in non-GDM women.

Serum YKL-40 for monitoring myocardial ischemia after revascularization in patients with stable coronary artery disease

AIM

The aim was to investigate the inflammatory biomarker YKL-40 as a monitor of myocardial ischemia in patients with coronary artery disease (CAD).

METHODS

A total of 311 patients with stable CAD were included. Blood samples were taken at baseline, the day after coronary angiography and/or after percutaneous coronary intervention and after 6 months.

RESULTS

A total of 148 (48%) patients were revascularized and 163 patients underwent only coronary angiography. In the entire population, serum YKL-40 increased significantly from baseline to 6 months (p = 0.05). This tendency was seen in nonrevascularized patients (p = 0.06), but not in revascularized patients (p = 0.46). Serum YKL-40 increased approximately 25% the day after the invasive procedure (p < 0.001) and then decreased significantly to nearly baseline after 6 months (p = 0.002).

CONCLUSION

Serum YKL-40 is a potential promising biomarker of disease progression but not of myocardial ischemia in patients with stable CAD.

The association between serum YKL-40 levels, mean platelet volume, and c-reactive protein in patients with cellulitis

BACKGROUND

Lower limb cellulitis is an infectious disease that has serious complications unless it is treated.

OBJECTIVES

In this pilot study, we evaluated whether levels of YKL-40, an acute-phase reactant, and mean platelet volume (MPV), which occurs secondary to inflammation in cellulitis, increase compared to healthy subjects. We also aimed to investigate the association between YKL-40 and MPV in the prognosis of the patients.

MATERIAL AND METHODS

A total of 55 patients with cellulitis (23 men and 32 women) and a similar age group of 46 healthy individuals (22 men and 24 women) were included in the study. Cellulitis was diagnosed according to guideline. Serum YKL-40 levels, MPV, C-reactive protein (CRP), and other biochemical values of both groups were compared.

RESULTS

YKL-40 levels (52.2±34.5 ng/mL vs 34.6±18.0 ng/mL, P=0.004), MPV (7.7±1.0 fL vs 6.9±0.7 fL, P<0.001), and CRP (9.5±8.2 mg/dL vs 0.7±0.6 mg/dL, P<0.001) were significantly higher in the patients with cellulitis than the control. The mean recovery time (RT) of the patients was 22.6±6.9 days. We found that YKL-40 (odds ratio [OR] 0.1, confidence interval [Cl] 0.028-0.191, P=0.009) and MPV (OR 2.4, Cl 0.254-4.578, P=0.029) have an independent association with RT.

CONCLUSION

YKL-40 and MPV values were correlated with higher CRP in the cellulitis group than in controls. According to these results, increased YKL-40 and MPV levels might be a prognostic factor for cellulitis in patients.

Serum YKL-40 in risk assessment for colorectal cancer: a prospective study of 4,496 subjects at risk of colorectal cancer

The aim of the present study was to test the hypothesis that high serum YKL-40 associates with colorectal cancer in subjects at risk of colorectal cancer. We measured serum YKL-40 in a prospective study of 4,496 Danish subjects [2,064 men, 2,432 women, median age 61 years (range, 18-97)] referred to endoscopy due to symptoms or other risk factors for colorectal cancer. Blood samples were collected just before large bowel endoscopy. Serum YKL-40 was determined by ELISA. Serum YKL-40 was higher (P < 0.0001, unadjusted for confounding covariates) in subjects diagnosed with colon cancer (median 126 μg/L, 25%-75%: 80-206 μg/L) and rectal cancer (104, 72-204 μg/L) compared with subjects with adenoma (84, 53-154 μg/L), other nonmalignant findings (79, 49-138 μg/L), and no findings (62, 41-109 μg/L). Serum YKL-40 independently predicted colorectal cancer [OR, 1.53; 95% confidence interval (CI), 1.40-1.67; AUC = 0.68, P < 0.0001]. Restricting the analysis to subjects with no comorbidity increased the OR for serum YKL-40 to predict colorectal cancer (OR, 1.82; 1.58-2.08; AUC = 0.73, P < 0.0001). Combining serum YKL-40 and CEA demonstrated that both were significant [(YKL-40, OR, 1.27; 95% CI, 1.16-1.40); (CEA, OR, 1.92; 1.75-2.10; AUC = 0.75, P < 0.0001; OR for a 2-fold difference in marker level)]. Multivariable analysis (YKL-40, CEA, age, gender, body mass index, and center) showed that serum YKL-40 was a predictor for colorectal cancer in individuals without comorbidity (OR, 1.25; 95% CI, 1.05-1.40; P = 0.012), whereas this was not the case for those with comorbidity (OR, 0.98; 95% CI, 0.84-1.14; P = 0.80). In conclusion, high serum YKL-40 in subjects suspected of colorectal cancer and without comorbidity associates with colorectal cancer. Determination of serum YKL-40 may be useful in combination with other biomarkers in risk assessment for colorectal cancer. Cancer Epidemiol Biomarkers Prev; 24(3); 621-6. ©2015 AACR.

Plasma YKL-40 in Inuit and Danes

AIMS

The aim of the present study was to investigate whether there are differences in plasma levels of YKL-40 between Inuit in Greenland and in Denmark and in Danes, as well as to study the relationship between alcohol intake, plasma YKL-40 and other factors in Inuit.

METHODS

Plasma YKL-40 levels were measured on 1645 people from The Greenland Population Study (a cross-sectional population study of Inuit from Denmark and West Greenland) and were compared with the plasma YKL-40 levels of 8899 people from The Copenhagen City Heart Study (a population-based, prospective study of the Danish general population).

RESULTS

The plasma concentrations of YKL-40 were significantly (P = 0.001) lower in Inuit living in Greenland (median 46 µg/l, range 10-2164, n = 1164) compared with the plasma YKL-40 levels of Inuit living in Denmark (median 63 µg/l, range 20-2827, n = 481) and of Danes living in Denmark (median 55 µg/l, range 10-2909, n = 8899). In Inuit, increased alcohol intake was significantly associated with increased plasma YKL-40 levels (P < 0.001), and high plasma YKL-40 levels were associated with high values of alkaline phosphatase and low values of albumin. Smoking, gender and bilirubin were not associated with the plasma YKL-40 level. High levels of YKL-40 and alcohol were associated with where people lived.

CONCLUSION

The plasma concentrations of YKL-40 are significantly lower in Inuit living in Greenland than Inuit and Danes living in Denmark. A number of factors, including different alcohol intake patterns, nutrition and genes may play a role in these findings.

Increased expression of YKL-40 in mild and moderate/severe persistent allergic rhinitis and its possible contribution to remodeling of nasal mucosa

BACKGROUND

Prominent expression of YKL-40 has been associated with pathological conditions characterized by tissue remodeling. We determined the expression level and distribution pattern of YKL-40 in allergic nasal mucosa and evaluated the effect of YKL-40 on the proliferation and migration of fibroblasts, the production of the mediators related to tissue remodeling, and collagen production. Additionally, the cytokine-driven regulation of YKL-40 expression was evaluated in cultured epithelial cells.

METHODS

The expression of YKL-40 in normal, mild, and moderate/severe allergic nasal mucosa was evaluated using real-time polymerase chain reaction (PCR), Western blot, and immunohistochemistry. Fibroblast migration was observed using a scratch wound method, and proliferation was determined by the MTT methods. Expression of proteoglycans, transforming growth factor (TGF) beta1, MMP2, MMP9, TIMP1, TIMP2, and collagen concentration were analyzed in fibroblasts treated with YKL-40. The expression levels of YKL-40 in cultured epithelial cells were examined after stimulation with mediators including Th2 cytokines, interferon (IFN)gamma, and TNF-alpha with real-time PCR and ELISA.

RESULTS

The expression of YKL-40 was up-regulated in allergic rhinitis and distributed in superficial epithelium, submucosal glands, and vascular endothelium, in addition to infiltrating cells. TGF-beta1, TIMP1, MMP9, and biglycan were up-regulated in fibroblasts on stimulation with YKL-40, accompanying increased proliferation and migration, and collagen production. IL-13, IFN-gamma, and TNF-alpha induced the increased production of YKL-40 in cultured epithelial cells.

CONCLUSION

YKL-40 is up-regulated in mild and moderate/severe persistent allergic rhinitis, and its expression can be regulated differentially by different cytokines, possibly contributing to the remodeling of nasal mucosa in allergic rhinitis.

Obesity and low-grade inflammation increase plasma follistatin-like 3 in humans

BACKGROUND

Rodent models suggest that follistatin-like 3 (fstl3) is associated with diabetes and obesity. In humans, plasma fstl3 is reduced with gestational diabetes. In vitro, TNF-α induces fstl3 secretion, which suggests a link to inflammation.

OBJECTIVE

To elucidate the association between plasma fstl3 and obesity, insulin resistance, and low-grade inflammation in humans.

STUDY DESIGN

Plasma fstl3 levels were determined in a cross-sectional study including three groups: patients with type 2 diabetes, impaired glucose tolerance, and healthy controls. In addition, lipopolysaccharide (LPS), TNF-α, or interleukin-6 (IL-6) as well as a hyperinsulinemic euglycemic clamp were used to examine if plasma fstl3 was acutely regulated in humans.

RESULTS

Plasma fstl3 was increased in obese subjects independent of glycemic state. Moreover, plasma fstl3 was positively correlated with fat mass, plasma leptin, fasting insulin, and HOMA B and negatively with HOMA S. Furthermore plasma fstl3 correlated positively with plasma TNF-α and IL-6 levels. Infusion of LPS and TNF-α, but not IL-6 and insulin, increased plasma fstl3 in humans.

CONCLUSION

Plasma fstl3 is increased in obese subjects and associated with fat mass and low-grade inflammation. Furthermore, TNF-α increased plasma fstl3, suggesting that TNF-α is one of the inflammatory drivers of increased systemic levels of fstl3.

Plasma levels of the proinflammatory chitin-binding glycoprotein YKL-40, variation in the chitinase 3-like 1 gene (CHI3L1), and incident cardiovascular events

Background

YKL‐40, encoded by the chitinase 3‐like 1 (CHI3L1) gene, is a chitinase‐like protein involved in innate immune function hypothesized to play a role in the progression of atherosclerosis that may have differential roles in myocardial infarction (MI), as compared to stroke.

Methods and Results

In a nested case‐control study conducted within a prospective cohort of 23 294 initially healthy women of European ancestry, we (1) measured plasma concentration of YKL‐40 among 359 participants who subsequently developed cardiovascular events and among 359 age‐, smoking‐, and hormone replacement therapy–matched participants who remained free of disease during 17 years of follow‐up, (2) compared effects of YKL‐40 on vascular risk to that associated with 3 alternative inflammatory biomarkers (high‐sensitivity C‐reactive protein) ([hsCRP], soluble intracellular adhesion molecule 1, and fibrinogen), and (3) evaluated the role of 41 single‐nucleotide polymorphisms (SNPs) in the chitinase 3‐like 1 gene (CHI3L1) as determinants of YKL‐40 levels and incident vascular events. YKL‐40 levels were higher in women with hypertension, diabetes, and obesity and correlated modestly with high‐density lipoprotein cholesterol, triglycerides, and hsCRP, but not with low‐density lipoprotein cholesterol. Baseline YKL‐40 level was significantly associated with incident thromboembolic stroke with a magnitude of effect (a 40% per quartile increase in odds ratio [OR], P=0.019) comparable to that of hsCRP (a 52% per quartile increase in OR, P=0.006). By contrast, no significant association was observed between YKL‐40 and incident MI. Genetic variation in CHI3L1 was strongly associated with YKL‐40 levels; however, in this sample set, we did not observe a statistically significant association between genotype and future vascular events.

Conclusions

Among initially healthy U.S. women, plasma levels of the proinflammatory chitenase‐like protein, YKL‐40, were influenced by environmental as well as genetic factors and predicted incident thromboembolic stroke, but not MI, a differential effect consistent with limited previous data.