YKL-40 protein is a marker of asthma

Association of serum YKL-40 and DPP4 with T2-high asthma in Chinese adults

This study aimed to assess the utility of serum YKL-40 and serum dipeptidyl peptidase IV (DPP4) as biomarkers for distinguishing between type 2 (T2)-high and T2-low asthma in the Chinese population. Additionally, we sought to explore the associations of serum YKL-40 and DPP4 levels with asthma characteristics and conventional markers. A real-world observational cross-sectional study was conducted, involving a total of 75 adult asthma patients. We collected general information, including demographics and medical history. Measurements included complete blood count, fractional exhaled nitric oxide (FeNO), post-bronchodilator spirometry, serum YKL-40 and serum DPP4 levels. Asthma endotypes, T2-high and T2-low, were defined through a comprehensive review of existing literature and expert group discussions. Logistic and linear regression models were employed. Our findings indicated no significant association between serum YKL-40 or serum DPP4 levels and T2-high asthma across all models. In the fully adjusted model, their odds ratios (OR) were 0.967 (95% CI: 0.920-1.017) and 0.997 (95% CI: 0.993-1.001), respectively. Notably, serum YKL-40 exhibited a positive correlation with FeNO (β = 0.382, 95% CI: 0.230-0.533) after adjusting for confounding factors. This association, however, diminished in patients under 40 years old (P = .24), males (P = .25), and those with FEV1%pred of 80% or higher (P = .25). Serum DPP4 demonstrated a negative correlation with FEV1/FVC in the fully adjusted model (β: -0.005, 95% CI: -0.009, -0.000). Among Chinese adult asthma patients, a positive correlation was observed between serum YKL-40 levels and FeNO in females aged over 40 with FEV1%pred less than 80%. Additionally, a weak negative correlation was found between serum DPP4 levels and FEV1/FVC. However, neither serum YKL-40 nor serum DPP4 levels exhibited the capability to differentiate between T2-high and T2-low asthma.

Further evidence for association of YKL-40 with severe asthma airway remodeling

BACKGROUND

The chitinase-like protein YKL-40 is associated with airflow limitation on spirometry and airway remodeling in patients with asthma. It remains unclear whether YKL-40 is associated with morphologic changes in the airways and parenchyma or with future progression of airflow limitation in severe asthma.

OBJECTIVE

To evaluate the association of circulating YKL-40 levels with morphologic changes in the airways and parenchyma and with longitudinal progression of airflow limitation.

METHODS

The patients were participants in the Hokkaido Severe Asthma Cohort Study (n = 127), including smokers. This study consisted of 2 parts. In analysis 1, we analyzed associations between circulating YKL-40 levels and several asthma-related indices, including computed tomography-derived indices of proximal wall area percentage, the complexity of the airways (airway fractal dimension), and the parenchyma (exponent D) cross-sectionally (n = 97). In analysis 2, we evaluated the impact of circulating YKL-40 levels on forced expiratory volume in 1 second (FEV₁) decline longitudinally for a 5-year follow-up (n = 103).

RESULTS

Circulating YKL-40 levels were significantly associated with proximal wall area percentage and airway fractal dimension (r = 0.25, P = .01; r = -0.22, P = .04, respectively), but not with exponent D. The mean annual change in FEV₁ was -33.7 (± 23.3) mL/y, and the circulating YKL-40 level was a significant independent factor associated with annual FEV₁ decline (β = -0.24, P = .02), even after controlling for exponent D (β = -0.26, P = .01).

CONCLUSION

These results provide further evidence for the association of YKL-40 with the pathogenesis of airway remodeling in severe asthma.

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.

Association between YKL-40 and asthma: a systematic meta-analysis

PURPOSE

Many studies have shown that chitinase-3-like protein 1 (CHI3L1), also known as YKL-40, is associated with asthma. The purpose of this meta-analysis was to evaluate the role of serum YKL-40 in the diagnosis and differential diagnosis of asthma, severity grading, and determination of disease state.

METHODS

The PubMed, Ovid, and Cochrane databases were searched. A total of 17 articles involving 5696 subjects were included in this meta-analysis.

RESULTS

The results showed that the level of YKL-40 was significantly higher in asthmatic patients than in the normal group regardless of age and residential location, and increased with severity and acute exacerbation (p < 0.05). YKL-40 levels were significantly different between chronic obstructive pulmonary disease (COPD) and asthma, and also between asthma-COPD overlap syndrome (ACO) and asthma (p < 0.05).

CONCLUSION

YKL-40 may act as a potential serological marker for the diagnosis of asthma, assessment of severity, indicator of the disease state, and differential diagnosis of COPD, ACO, and asthma.

Effects of Obesity on Airway and Systemic Inflammation in Asthmatic Children

BACKGROUND

Obese asthma is a complex syndrome with certain phenotypes that differ in children and adults. There is no clear evidence regarding the presence of additive or synergistic pathological interaction between obesity and asthma in children.

OBJECTIVES

Our aim was to demonstrate the interaction of obesity and asthma in children in terms of airway and systemic inflammation by a controlled observational study.

METHODS

Four groups were formed: asthma obese (AO), asthma nonobese (ANO), non-AO (NAO), nonasthma nonobese (NANO). Spirometry test, fractional exhaled nitric oxide (FeNO) test, skin prick test, serum inflammatory biomarkers (C-reactive protein, C3, C4, adiponectin, leptin, resistin, periostin, YKL-40, Type 1, and Type 2 cytokines) were conducted and evaluated in all participants. Sputum inflammatory cells (sputum eosinophils and neutrophils) were evaluated in patients who could produce induced sputum and obesity-asthma interactions were determined.

RESULTS

A total of 153 participants aged 6-18 years were included in the study, including the AO group (n = 46), the ANO group (n = 45), the NAO group (n = 30), and the NANO group (n = 32). IL-4 (p < 0.001), IL-5 (p < 0.001), IL-13 (p < 0.001), resistin (p < 0.001), and YKL-40 (p < 0.001) levels were higher in patients with asthma independent of obesity. The lowest adiponectin level was found in the AO group and obesity-asthma interaction was detected (p < 0.001). Sputum eosinophilia (p < 0.01), sputum neutrophilia (p < 0.01), and FeNO levels (p = 0.07) were higher in asthmatic patients independent of obesity. In the group with paucigranulocytic inflammation, resistin and YKL-40 levels were significantly lower than in the group without paucigranulocytic inflammation (p < 0.01).

CONCLUSION

No interaction was found between obesity and asthma in terms of airway inflammation. Interaction between obesity and asthma was shown in terms of adiponectin level and resistin/adiponectin and leptin/adiponectin ratios. It was found that serum YKL-40 and resistin levels could be associated with airway inflammation.

Overexpression of YKL-40 (CHI3L1 gene) in patient fluids may be a potential predictive marker for early detection of comorbidity in non-communicable disease

Predictive biomarkers which can diagnose the onset of non-communicable diseases and the associated comorbid conditions are lacking for clinical utility. Highly sensitive and specific biomarkers for early disease detection and risk stratification may provide timely intervention to patients and prevent secondary complications. However, till the time patients are diagnosed, cellular events and biomolecules get active effecting multiple organs at the same time. This series of events lead to disruption in normal functioning of the organs and their coordinative crosstalk, hence, increase in mortality rate of patients. The primary functional molecules of inflammatory pathways are active in NCDs. YKL-40, an anti-apoptotic molecule in inflammatory pathways, is overexpressed in patient fluids in different organs under diseased conditions. We performed a preliminary network analysis to study YKL-40 co-expression with diagnostic markers: TNNT2/I3 (Cardiac Troponin T/I) for cardiovascular diseases, LCN2 (NGAL) and CKM (Creatinine kinase M-type) in acute kidney injury and HbA1c in type-2-diabetes. It is observed that YKL-40 is actively co-expressed and linked with standard diagnostic markers and may be influencing the pathways active in organ crosstalk. The pathways may be regulating the signaling events in patients with non-communicable diseases leading to comorbidities. We, hence, postulate that if YKL-40 and disease specific pathways influenced are clinically utilized, this will provide the foundation of establishing tailored and specific approach in diagnosis and monitoring non-communicable diseases and predict the onset of comorbid conditions due to phenomenon influencing organ cross talks.

Chitinase-like protein YKL-40 regulates human bronchial epithelial cells proliferation, apoptosis, and migration through TGF-β1/Smads pathway

In order to study the effects of chitinase-like protein YKL-40 on proliferation, apoptosis, and migration of human bronchial epithelial cell line (BEAS-2B), and the underlying mechanisms, we cultured BEAS-2B alone or with different concentrations of YKL-40. thiazolyl blue tetrazolium bromide (MTT) assay was used to examine the cell proliferation. Annexin V-fluorescein isothiocyanate isomer (FITC)/propidium iodide staining and scratch assay were performed to test the cell apoptosis and migration. The concentrations of transforming growth factor-β1 (TGF-β1), Smad3, Smad7, alpha-smooth muscle actin (α-SMA), interleukin-4 (IL-4), IL-6, and IL-8 in the cell culture supernatant were detected by enzyme-linked immunosorbent assay. The messenger RNA and protein levels of YKL-40, TGF-β1, Smad3, Smad7, and α-SMA were detected by reverse transcription polymerase chain reaction and Western blot. BEAS-2B cells cultured with different concentrations of YKL-40 showed significantly higher cell proliferation and migration and inflammatory cytokines compared with that of control group, while the cell apoptosis was significantly lower than that of control group (p < 0.05). In addition, BEAS-2B cells cultured with YKL-40 had increased TGF-β1, Smad3, Smad7, and α-SMA levels in the supernatant, compared with that of BEAS-2B cells cultured alone (p < 0.05). Furthermore, LY364947, as TGF-β1/Smads signaling pathway inhibitor, decreased cell proliferation and migration ability and enhanced cell apoptosis of BEAS-2B cells compared with control group (p < 0.05). However, YKL-40 administration reversed the effect of LY364947 on the biological behavior of BEAS-2B cells. YKL-40 could affect the biological behaviors of BEAS-2B cells, which might be related to the TGF-β1/Smads pathway.

Biomarkers and asthma management: analysis and potential applications

PURPOSE OF REVIEW

Asthma features a high degree of heterogeneity in both pathophysiology and therapeutic response, resulting in many asthma patients being treated inadequately. Biomarkers indicative of underlying pathological processes could be used to identify disease subtypes, determine prognosis and to predict or monitor treatment response. However, the newly identified as well as more established biomarkers have different applications and limitations.

RECENT FINDINGS

Conventional markers for type 2-high asthma, such as blood eosinophils, fraction of exhaled nitric oxide, serum IgE and periostin, feature limited sensitivity and specificity despite their significant correlations. More distinctive models have been developed by combining biomarkers and/or using omics techniques. Recently, a model with a positive predictive value of 100% for identification of type 2-high asthma based on a combination of minimally invasive biomarkers was developed.

SUMMARY

Individualisation of asthma treatment regimens on the basis of biomarkers is necessary to improve asthma control. However, the suboptimal properties of currently available conventional biomarkers limit its clinical utility. Newly identified biomarkers and models based on combinations and/or omics analysis must be validated and standardised before they can be routinely applied in clinical practice. The development of robust biomarkers will allow development of more efficacious precision medicine-based treatment approaches for asthma.

Functional variant of CHI3L1 gene is associated with neck metastasis in oral cancer

OBJECTIVES

Oral cancer is the most common head and neck malignancy, and it is associated with a high recurrence rate and lymph node metastasis potential. YKL-40, also known as chitinase-3-like protein 1 (CHI3L1), is a secreted glycoprotein that serves as a biomarker in several diseases. It also plays a crucial role in regulating many characteristics of cancer, such as cell growth, migration, anti-apoptosis, and angiogenesis. Accumulating evidence supports the link between single-nucleotide polymorphisms (SNPs) and oral cancer, but no report on the association between CHI3L1 polymorphisms and oral cancer is available. Thus, the present study evaluated the contribution of CHI3L1 SNPs to oral cancer susceptibility and clinicopathology.

MATERIALS AND METHODS

This study recruited a total of 2362 subjects, comprising 1190 healthy male controls and 1172 male patients with oral cancer. Allelic discrimination of the CHI3L1 polymorphisms - 1371 G>A (rs6691378), - 247 G>A (rs10399805), - 131 C>G (rs4950928), and + 2950 T>C (rs880633) was assessed through real-time polymerase chain reaction.

RESULTS

We detected a significant association of rs10399805 and rs6691378 with the risk of oral cancer (AOR, 1.537; 95% CI, 1.089-2.168; p = 0.014; AOR, 1.561; 95% CI, 1.131-2.156; p = 0.007, respectively) after adjustment for three potential confounders, smoking, betel nut chewing, and alcohol consumption. Moreover, we found that oral cancer patients carrying the homozygous A/A genotype of the rs10399805 (p = 0.035) or rs6691378 polymorphism (p = 0.023) showed a significantly lower risk of lymph node metastasis. Moreover, according to the Genotype-Tissue Expression database, the rs10399805 and rs6691378 polymorphisms in the promoter region were associated with decreased levels of CHI3L1 mRNA.

CONCLUSIONS

In conclusion, we found that the homozygous mutant allele of rs10399805 and rs6691378 appeared to have significantly lower risk of lymph node metastasis and associated with its mRNA levels in oral cancer.

CLINICAL RELEVANCE

The CHI3L1 polymorphisms rs10399805 and rs6691378 may act as biomarkers for predicting lymph node metastasis in oral cancer patients.

The current and future role of biomarkers in type 2 cytokine-mediated asthma management

Assessment and management of asthma is complicated by the heterogeneous pathophysiological mechanisms that underlie its clinical presentation, which are not necessarily reflected in standardized management paradigms and which necessitate an individualized approach to treatment. This is particularly important with the emerging availability of a variety of targeted forms of therapy that may only be appropriate for use in particular patient subgroups. The identification of biomarkers can potentially aid diagnosis and inform prognosis, help guide treatment decisions and allow clinicians to predict and monitor response to treatment. Biomarkers for asthma have been identified from a variety of sources, including airway, exhaled breath and blood. Biomarkers from exhaled breath include fractional exhaled nitric oxide, measurement of which can help identify patients most likely to benefit from inhaled corticosteroids and targeted anti-immunoglobulin E therapy. Biomarkers measured in blood are relatively non-invasive and technically more straightforward than those measured from exhaled breath or directly from the airway. The most well established of these are the blood eosinophil count and serum periostin, both of which have demonstrated utility in identifying patients most likely to benefit from targeted anti-interleukin and anti-immunoglobulin E therapies, and in monitoring subsequent treatment response. For example, serum periostin appears to be a biomarker for responsiveness to inhaled corticosteroid therapy and may help identify patients as suitable candidates for anti-IL-13 treatment. The use of biomarkers can therefore potentially help avoid unnecessary morbidity from high-dose corticosteroid therapy and allow the most appropriate and cost-effective use of targeted therapies. Ongoing clinical trials are helping to further elucidate the role of established biomarkers in routine clinical practice, and a range of other circulating novel potential biomarkers are currently being investigated in the research setting.

Severe Asthma in Children

PURPOSE OF REVIEW

The aim of this study is to characterize, diagnose, evaluate, and treat severe childhood asthma.

RECENT FINDINGS

Understanding the occurrence of the physiologic and clinical presentations of childhood severe asthma, the treatment and response may be predicted by biomarkers, but the patient's response is highly variable. The onset of severe asthma occurs early and is primarily predicted by severity of viral infection and coexistence of the atopic state.

Biomarkers for the Phenotyping and Monitoring of Asthma in Children

An important issue in relation to the utility and reliability of biomarkers for asthma monitoring is how asthma is defined and characterized. What kind of asthma, or at what stage of the disease is a particular biomarker supposed to add information? Often, the purpose, or usefulness of a biomarker is not made clear. Diagnosis, severity evaluation, and monitoring are all different clinical uses for a biomarker, and confusion may arise when a biomarker is suitable for one of these but not another. When the utility of available biomarkers are discussed, these different roles need to be clarified. Our opinion is that there are four aspects of relevance to asthma, for which biomarkers are required: to diagnose allergies, to evaluate inflammation in the airways, to evaluate hyper-responsiveness, and for certain measures of lung function, such as lung clearance index. These types of biomarkers are needed for the phenotyping and monitoring of asthma. Another important role for biomarkers is, as mentioned above, to monitor asthma in order to follow treatment effects on inflammation and hyper-responsiveness as objective adjuncts to the patients' own symptom reports and lung function. This review will mainly focus on biomarkers that reflect airway inflammation. In spite of the numerous studies that have been conducted, we still have to remember that the value of biomarkers available for routine use, such as eosinophil counts in blood and sputum and exhaled nitric oxide, have to be interpreted in relation to reported symptoms and lung function. Measures of bronchial hyper-responsiveness, performed either by direct (methacholine challenge) or indirect (exercise or mannitol challenge) methods, could be considered biomarkers but will not be included in this review. On the other hand, diagnosing allergy is not usually useful for monitoring asthma although it is of fundamental importance for the interpretation of most biomarkers that are suitable for monitoring. We have therefore included the different approaches for diagnosing and evaluating allergic sensitization in this review.

Estimation of Serum YKL-40 by Real-Time Surface Plasmon Resonance Technology in North-Indian Asthma Patients

BACKGROUND

Many studies reported for estimating serum YKL-40 using ELISA or RIA methods. This study introduces the plausible utilization of real-time surface plasmon resonance (SPR) technology in investigating the expression of serum YKL-40 protein levels and ELISA method for serum IgE in bronchial asthma.

METHODS

A commercially available BIAcore 2000 instrument, based on SPR technology, was utilized for assessing serum YKL-40 levels in a control sample size of 45 and active sample size of 97. Antibody immobilization was optimized to obtain the best sensor performance and a sensitive analytic detection. A commercially available ELISA kit was utilized for detecting serum IgE to estimate allergic condition-associated asthma.

RESULTS

The results of SPR technology could distinctly classify with highly statistical significance, the asthma severities by estimating the elevated levels of YKL-40 in blood sera of minute quantities (up to 0.33 ng/ml), and thus differentiates superior utility in comparison with ELISA method. No statistically significant correlation of YKL-40 and IgE was observed.

CONCLUSIONS

Serum YKL-40 may be used as a protein marker in classifying asthma severity by applying SPR technology as a reliable, label-free, highly sensitive, and cost-effective tool.

Increased YKL-40 and Chitotriosidase in Asthma and Chronic Obstructive Pulmonary Disease

RATIONALE

Serum chitinases may be novel biomarkers of airway inflammation and remodeling, but less is known about factors regulating their levels.

OBJECTIVES

To examine serum chitotriosidase activity and YKL-40 levels in patients with asthma and chronic obstructive pulmonary disease (COPD) and evaluate clinically relevant factors that may affect chitinase levels, including genetic variability, corticosteroid treatment, disease exacerbations, and allergen exposure.

METHODS

Serum chitotriosidase (CHIT1) activity and YKL-40 (CHI3L1) levels, as well as the CHIT1 rs3831317 and CHI3L1 rs4950928 genotypes, were examined in subsets of patients with mild to moderate asthma (n = 76), severe asthma (n = 93), and COPD (n = 64) taking part in the European multicenter BIOAIR (Longitudinal Assessment of Clinical Course and Biomarkers in Severe Chronic Airway Disease) study. Blood was obtained at baseline, before and after a 2-week oral steroid intervention, up to six times during a 1-year period, and during exacerbations. Baseline chitinase levels were also measured in 72 healthy control subjects. The effect of allergen inhalation on blood and sputum YKL-40 levels was measured in two separate groups of patients with mild atopic asthma; one group underwent repeated low-dose allergen challenge (n = 15), and the other underwent high-dose allergen challenge (n = 16).

MEASUREMENTS AND MAIN RESULTS

Serum chitotriosidase and YKL-40 were significantly elevated in patients with asthma and those with COPD compared with healthy control subjects. Genotype and age strongly affected both YKL-40 and chitotriosidase activity, but associations with disease remained following adjustment for these factors. Correlations were observed with lung function but not with other biomarkers, including exhaled nitric oxide, blood eosinophils, periostin, and IgE. Generally, acute exacerbations, allergen-induced airway obstruction, and corticosteroid treatment did not affect circulating chitinase levels.

CONCLUSIONS

YKL-40 and chitotriosidase are increased in asthma and more so in COPD. The data in the present study support these substances as being relatively steroid-insensitive, non-T-helper cell type 2-type biomarkers distinctly related to chronic inflammatory disease processes.

Asthma Associates With Human Abdominal Aortic Aneurysm and Rupture

OBJECTIVE

Both asthma and abdominal aortic aneurysms (AAA) involve inflammation. It remains unknown whether these diseases interact.

APPROACH AND RESULTS

Databases analyzed included Danish National Registry of Patients, a population-based nationwide case-control study included all patients with ruptured AAA and age- and sex-matched AAA controls without rupture in Denmark from 1996 to 2012; Viborg vascular trial, subgroup study of participants from the population-based randomized Viborg vascular screening trial. Patients with asthma were categorized by hospital diagnosis, bronchodilator use, and the recorded use of other anti-asthma prescription medications. Logistic regression models were fitted to determine whether asthma associated with the risk of ruptured AAA in Danish National Registry of Patients and an independent risk of having an AAA at screening in the Viborg vascular trial. From the Danish National Registry of Patients study, asthma diagnosed <1 year or 6 months before the index date increased the risk of AAA rupture before (odds ratio [OR]=1.60-2.12) and after (OR=1.51-2.06) adjusting for AAA comorbidities. Use of bronchodilators elevated the risk of AAA rupture from ever use to within 90 days from the index date, before (OR=1.10-1.37) and after (OR=1.10-1.31) adjustment. Patients prescribed anti-asthma drugs also showed an increased risk of rupture before (OR=1.12-1.79) and after (OR=1.09-1.48) the same adjustment. In Viborg vascular trial, anti-asthmatic medication use associated with increased risk of AAA before (OR=1.45) or after adjustment for smoking (OR=1.45) or other risk factors (OR=1.46).

CONCLUSIONS

Recent active asthma increased risk of AAA and ruptured AAA. These findings document and furnish novel links between airway disease and AAA, 2 common diseases that share inflammatory aspects.

Commentary: IL-4 and IL-13 receptors and signaling

Interleukin (IL)-4 and IL-13 were discovered approximately 30years ago and were immediately linked to allergy and atopic diseases. Since then, new roles for IL-4 and IL-13 and their receptors in normal gestation, fetal development and neurological function and in the pathogenesis of cancer and fibrosis have been appreciated. Studying IL-4/-13 and their receptors has revealed important clues about cytokine biology and led to the development of numerous experimental therapeutics. Here we aim to highlight new discoveries and consolidate concepts in the field of IL-4 and IL-13 structure, receptor regulation, signaling and experimental therapeutics.

Allergen induced pulmonary inflammation enhances mammary tumor growth and metastasis: Role of CHI3L1

Metastasis is the primary cause of mortality in women with breast cancer. Metastasis to the lungs is greater in patients with pulmonary inflammatory illnesses. It is unknown how pre-existing pulmonary inflammation affects mammary tumor progression. We developed a novel breast cancer model in which pulmonary inflammation is induced in mice prior to tumor cell implantation. In the present study, we determined how pre-existing allergen-induced inflammation changes the pulmonary microenvironment to exacerbate tumor metastasis. We showed that pre-existing pulmonary inflammation in mammary tumor bearers is associated with: 1) an increase in growth of the primary tumor and metastasis; 2) an increase in the expression of a glycoprotein known as CHI3L1; and 3) increase in the levels of myeloid populations in their lungs. We also showed that myeloid derived cells from the lungs of allergic tumor bearers produce higher amounts of CHI3L1 than the saline controls. We previously showed that CHI3L1 induces the expression of proinflammatory and protumorigenic molecules. In this study, we show that CHI3L1 knockout tumor bearers with pre-existing allergic pulmonary inflammation had decreased levels of myeloid-derived cells, decreased levels of proinflammatory mediators, and a significant reduction in tumor volume and metastasis compared with the wild-type controls. Pre-existing inflammation and CHI3L1 might be driving the establishment of a premetastatic milieu in the lungs and aiding in the support of metastatic foci. Understanding the role of allergen-induced CHI3L1 and inflammation in tumor bearers and its effects on the pulmonary microenvironment could result in targeted therapies for breast cancer.

The role of chitin, chitinases, and chitinase-like proteins in pediatric lung diseases

Chitin, after cellulose, the second most abundant biopolymer on earth, is a key component of insects, fungi, and house-dust mites. Lower life forms are endowed with chitinases to defend themselves against chitin-bearing pathogens. Unexpectedly, humans were also found to express chitinases as well as chitinase-like proteins that modulate immune responses. Particularly, increased levels of the chitinase-like protein YKL-40 have been associated with severe asthma, cystic fibrosis, and other inflammatory disease conditions. Here, we summarize and discuss the potential role of chitin, chitinases, and chitinase-like proteins in pediatric lung diseases.

YKL-40 protein correlates with the phenotype of asthma

Purpose

YKL-40 is a chitinase-like protein found to correlate with asthma as well as numerous infectious and autoimmune diseases or cancer. The aim of the present study was to investigate the role of YKL-40 as a possible marker of asthma and its associations with factors differentiating phenotypes of asthma.

Methods

The study group comprised 167 patients, including 116 women and 51 men aged 18–88 years with chronic asthma. The control group comprised 81 healthy individuals, including 50 women and 31 men aged 19–86 years. In every participant, medical history was taken; spirometry and skin prick tests were performed. YKL-40 was determined in sera by means of ELISA test.

Results

Mean serum YKL-40 level was 59.7 ng/ml (53.6–65.7 ng/ml; 95 % CI) with significant difference between asthmatics and healthy controls (mean values: 66.8 ± 53.8 vs. 44.9 ± 29.4 ng/ml; p < 0.001). In asthmatics, the level was significantly higher in subgroup with poor control of symptoms and exacerbations (91.8 ± 57.1 ng/ml) compared to stable asthmatics (59.6 ± 50.8 ng/ml; p < 0.001) as well as in atopic compared to non-atopic asthmatics (77.2 ± 53.9 vs. 61.1 ± 57.8 ng/ml; p < 0.001). Mean YKL-40 level in obese asthmatics was 135.6 ng/ml compared to 50.0 ng/ml in non-obese (p < 0.001). When phenotypes of early-onset atopic, late-onset non-atopic, and obesity-related asthma were compared, YKL-40 levels were 80.62 ± 46.9, 51.5 ± 24.9, and 168.1 ± 71.5 ng/ml, respectively (p < 0.05).

Conclusion

Although YKL-40 is not a specific marker for asthma, it correlates with some clinical features such as exacerbation, level of control, atopy, and obesity.

YKL-40 is correlated with FEV1 and the asthma control test (ACT) in asthmatic patients: influence of treatment

Background

YKL-40 is also called chitinase-3-like-1 (CHI3L1) protein and may be a marker for asthma. The aims of the present study were to investigate whether serum YKL-40 levels are stable or decreased in patients with asthma after appropriate treatment and to evaluate the correlation of YKL-40 levels with lung function and asthma control test (ACT) results.

Methods

A total of 103 asthmatic patients (mean age 33.1 ± 0.9 years) with diagnosed asthma were enrolled in our study. All patients underwent a detailed clinical examination and completed the ACT questionnaire, serum YKL-40 measurement, and spirometry before (visit 1) and 8 weeks after initiation of treatment (visit 2).

Results

At the follow-up, the median serum YKL-40 level was significantly decreased compared to the levels at visit 1 (75.2 [55.8-86.8] ng/ml versus 54.5 [46.4-58.4] ng/ml, p < 0.001). The serum YKL-40 level was negatively correlated with %FEV₁ (r = -0.37, p < 0.001) and ACT score (r = -0.26, p = 0.007) at visit 1. The change in serum YKL-40 levels between the visits was significantly correlated with changes in FEV₁ (r = -0.28, p = 0.006) and ACT score (r = -0.22, p = 0.037). Patients with elevated YKL-40 levels had significantly greater corticosteroid use than patients with lower levels.

Conclusions

YKL-40 was reduced in the serum of asthmatic patients after appropriate treatment, and the levels correlated with improvements in %FEV₁ and ACT. High levels of serum YKL-40 may be refractory to current asthma treatments.

Trial registration

ChiCTR-OCC-13003316

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2466-15-1) contains supplementary material, which is available to authorized users.

The serum YKL-40 level is associated with vascular injury and predicts proteinuria in nephrotic syndrome patients

AIM

Nephrotic syndrome (NS) is associated with an increased rate of cardiovascular events. The YKL-40 level is associated with atherosclerosis, endothelial dysfunction and proteinuria in renal and non-renal populations. The aim of this study was to investigate the relationships between the YKL-40 level and both vascular injury and proteinuria in NS patients.

METHODS

Sixty-nine NS patients and 20 healthy subjects were enrolled in the present study. The endothelial function was assessed according to the flow mediated dilatation (FMD) and the degree of arterial stiffness was determined based on the pulse wave velocity (PWV). The serum YKL-40 levels were measured using ELISA.

RESULTS

The YKL-40 levels and PWV values were higher and the FMD values were lower in the NS patients than in the healthy controls. However, the CA-IMT and LVEF levels were not statistically different between the two groups. The patients were divided into three groups with respect to the extent of proteinuria: the normoproteinuria group (n:18), non-nephrotic proteinuria group (n:33) and nephrotic proteinuria group (n:18). Consequently, the YKL-40 levels and PWV values were significantly increased and the FMD values were decreased in the nephrotic proteinuria group compared to that observed in both the non-nephrotic proteinuria and normoproteinuria groups. Furthermore, the YKL-40 level correlated with the FMD and PWV values in the NS patients. In addition, proteinuria correlated with the YKL-40, FMD, PWV, eGFR and fasting LDL cholesterol values in this patient group. Multivariate linear regression analyses showed that the YKL-40 and eGFR values were effective in predicting proteinuria in the NS patients.

CONCLUSIONS

The serum YKL-40 level is associated with endothelial dysfunction and increased arterial stiffness in NS patients and may be an indicator of the level of proteinuria in this patient population.

Serum based diagnosis of asthma using Raman spectroscopy: an early phase pilot study

The currently prescribed tests for asthma diagnosis require compulsory patient compliance, and are usually not sensitive to mild asthma. Development of an objective test using minimally invasive samples for diagnosing and monitoring of the response of asthma may help better management of the disease. Raman spectroscopy (RS) has previously shown potential in several biomedical applications, including pharmacology and forensics. In this study, we have explored the feasibility of detecting asthma and determining treatment response in asthma patients, through RS of serum. Serum samples from 44 asthma subjects of different grades (mild, moderate, treated severe and untreated severe) and from 15 reference subjects were subjected to Raman spectroscopic analysis and YKL-40 measurements. The force expiratory volume in 1 second (FEV1) values were used as gold standard and the serum YKL-40 levels were used as an additional parameter for diagnosing the different grades of asthma. For spectral acquisition, serum was placed on a calcium fluoride (CaF2) window and spectra were recorded using Raman microprobe. Mean and difference spectra comparisons indicated significant differences between asthma and reference spectra. Differences like changes in protein structure, increase in DNA specific bands and increased glycosaminoglycans-like features were more prominent with increase in asthma severity. Multivariate tools using Principal-component-analysis (PCA) and Principal-component based-linear-discriminant analysis (PC-LDA) followed by Leave-one-out-cross-validation (LOOCV), were employed for data analyses. PCA and PC-LDA results indicate separation of all asthma groups from the reference group, with minor overlap (19.4%) between reference and mild groups. No overlap was observed between the treated severe and untreated severe groups, indicating that patient response to treatment could be determined. Overall promising results were obtained, and a large scale validation study on random subjects is warranted before the routine clinical usage of this technique.

Ovalbumin enhances YKL-40, IL-5, GM-CSF, and eotaxin expression simultaneously in primarily cultured mouse tracheal epithelial cells

Epithelial inflammation and eosinophil infiltration are crucial for the pathogenesis of asthma. Many inflammatory mediators, such as YKL-40, interleukin -5 (IL-5), granulocyte-macrophage colony-stimulating factor (GM-CSF), and eotaxin, are important for the development of allergic airway inflammation. This study is aimed at investigating the impact of treatment with ovalbumin (OVA) on the levels of those inflammatory mediators in primarily cultured mouse tracheal epithelial cells. Mouse tracheal epithelial cells were isolated and identified by immunofluorescent staining; the isolated mouse tracheal epithelial cells expressed cytokeratins. Treatment with OVA for 24 or 48 h significantly increased the relative levels of YKL-40, IL-5, GM-CSF, and eotaxin mRNA transcripts and YKL-40, IL-5, GM-CSF, and eotaxin proteins secreted in the supernatants of cultured cells, as compared with that in the untreated control cells (P < 0.01, P < 0.05, respectively). The levels of YKL-40 expression were correlated positively with the levels of IL-5, GM-CSF, and eotaxin expression in the OVA-treated cells. These data indicated that treatment with OVA simultaneously enhanced YKL-40, IL-5, GM-CSF, and eotaxin expression in the cultured mouse tracheal epithelial cells in vitro. These inflammatory mediators may synergistically contribute to the pathogenesis of allergic inflammation, and this study may help to understand the role of YKL-40 in the pathogenesis of asthma.

Serum biomarkers in elderly asthma

OBJECTIVE

Asthma is usually misdiagnosed and under-treated in the elderly population, resulting in complications and increased severity to the patient. In this review, we describe some of the most important serum markers of asthma studied so far, reporting their outcomes and possible prediction of asthma in the elderly population.

METHODS

The PubMed electronic database was used to search for promising serum biomarkers of asthma studied in original articles published in peer-reviewed journals from 2000 to January 2013.

RESULTS

A total of 13 relevant serum biomarkers were selected, including IgE, CRP, high sensitive CRP, IL-6, IL-8, IL-17, TNF-α, neopterin, serum amyloid A, eosinophil cationic protein, leukolysin, YKL-40 and soluble CD86.

CONCLUSIONS

Although the major focus of treatment and research has been on allergic asthma, several forms of the disease are recognized, such as neutrophilic asthma, which is characteristic of older patients. Different phenotypes imply different treatments and so it becomes important to correctly determine which type of asthma the patient is suffering from. Serum markers capable of supporting a diagnosis of asthma are needed in order to counter mistreatment and misdiagnosis with other obstructive airways disease (OAD) in elderly patients. As convenient as serum markers may seem to be, a marker capable of accurately identifying asthma with sufficient specificity is yet to be found.

The chitinase-like protein YKL-40 increases mucin5AC production in human bronchial epithelial cells

Mucus overproduction is an important feature in patients with chronic inflammatory airway diseases. However, the regulatory mechanisms that mediate excessive mucin production remain elusive. Recently, the level of YKL-40, a chitinase-like protein, has been found to be significantly increased in chronic inflammatory airway diseases and has been shown to be associated with the severity of these diseases. In this study, we sought to explore the effect of YKL-40 on mucin5AC (MUC5AC) production in chronic inflammatory airway diseases and the potential signaling pathways involved in this process. We found that elevated YKL-40 levels increased the mRNA and protein expression of MUC5AC in a dose- and time-dependent manner, in association with the phosphorylation of extracellular signal-regulated kinase (ERK) and nuclear factor κB (NF-κB), reflecting their activation. These responses were significantly suppressed by the knockdown of protease-activating receptor 2 (PAR2) with specific small interfering RNA or the inhibitors of ERK and NF-κB. YKL-40-induced MUC5AC overproduction was also effectively attenuated by the inhibitor of focal adhesion kinase (FAK). Taken together, these results imply that YKL-40 can stimulate excessive MUC5AC production through PAR2- and FAK-mediated mechanisms.

Evaluation of CHI3L-1 and CHIT-1 expression in differentiated and polarized macrophages

Chitinase 3-like protein 1 (CHI3L-1) and chitotriosidase (CHIT-1) are members of the chitinase family. CHI3L-1 is a newly recognized protein that is secreted by activated macrophages and neutrophils and expressed in a broad spectrum of inflammatory conditions and cancers. In human plasma, CHIT-1 activity has been proposed as a biochemical marker of macrophage activation. Although CHI3L-1 expression in inflammation is under examination, little is known regarding its regulation during macrophages' full maturation and polarization. In this study, we compared CHI3L-1 and CHIT-1 modulation during monocyte to macrophage transition and polarization. Gene expression analysis was investigated by real-time PCR. We found that during the maturation of monocytes into macrophages, the expression of both CHI3L-1 and CHIT-1 increased exponentially over time. Additionally, we observed a different regulation of CHI3L-1 and CHIT-1 in undifferentiated monocytes under stimulation with lipopolysaccharide, interferon-γ, and interleukin-4, at the same concentration used to polarize macrophages. Our finding suggests that in the immune response, the role of CHI3L-1 and CHIT-1 is not restricted to innate immunity, but they are also protagonists in acquired immunity.

The relation of circulating YKL-40 to levels and decline of lung function in adult life

BACKGROUND

YKL-40 is a chitinase-like protein that, in cross-sectional clinical studies, has been associated with severe asthma and COPD in smokers.

AIM

To determine the longitudinal relation of circulating YKL-40 to levels and decline of lung function in the general population.

METHODS

We used longitudinal data from up to 13 surveys from the population-based TESAOD study which was conducted in Tucson, Arizona between 1972 and 1996. In cross-sectional analyses, we also used data from 3 Spanish centers of the multicenter ECRHS study (ECRHS-Sp). Serum YKL-40 was measured at baseline in TESAOD and in survey 2 in ECRHS-Sp using ELISAs. Multivariate linear regression was used to test associations of serum YKL-40 to concomitant lung function. In TESAOD, random coefficients models were used to test associations of serum YKL-40 to subsequent decline of lung function.

RESULTS

Data on YKL-40 and lung function were available from 1088 TESAOD and 854 ECRHS-Sp adult participants (59% and 51% females; respectively). In adjusted multivariate meta-analyses, being in the highest YKL-40 quartile was associated cross-sectionally with significant deficits in FEV1 and FVC %predicted. In adjusted longitudinal analyses, TESAOD participants in the top YKL-40 quartile had an FEV1 decline that was 5 ml/yr (p = 0.05) faster than subjects in the third quartile, 5 ml/yr (p = 0.02) faster than subjects in the second quartile, and 10 ml/yr (p < 0.001) faster than subjects in the lowest YKL-40 quartile. These longitudinal effects were particularly strong in smokers and absent in never smokers. After adjusting for covariates, as compared with the other three quartiles combined, the top YKL-40 quartile was associated with a 9 ml/yr (p = 0.001) faster FEV1 decline among smokers, while no significant effects were found among never smokers (2 ml/yr, p = 0.35).

CONCLUSIONS

Circulating YKL-40 is associated with levels and decline of lung function in the general population and may be a biomarker of susceptibility to the long-term effects of cigarette smoking.

The inflammatory biomarker YKL-40 at admission is a strong predictor of overall mortality

OBJECTIVES

YKL-40 is an inflammatory biomarker associated with disease activity and mortality in patients with diseases characterized by inflammation and tissue remodelling. The aim of this study was to describe the prognostic value of YKL-40 in an unselected patient population.

DESIGN

In consecutive patients admitted to hospital during a 1-year period, blood was collected and information regarding final diagnosis and mortality was collected. Median follow-up time was 11.5 years.

SETTING

District hospital, Copenhagen, Denmark.

PATIENTS

A total of 1407 patients >40 years of age were admitted acutely.

MAIN OUTCOME MEASURE

All-cause mortality.

RESULTS

Median YKL-40 was increased in patients (157 μg L(-1) , range 13-7704 μg L(-1) ) compared to healthy controls (40 μg L(-1) , range 29-58 μg L(-1) ; P < 0.001). Patients with YKL-40 in the highest quartile had a hazard ratio (HR) of 7.1 [95% confidence interval (CI) 4.2-12.0] for all-cause mortality in the first year and 3.4 (95% CI 2.8-4.2) in the total study period, compared to those in the lowest quartile (HR = 1). The HR for death for all patients with YKL-40 above the normal age-corrected 95th percentile was 2.1 (95% CI 1.6-2.7) after 1 year and 1.5 (95% CI 1.3-1.7) during the total study period, compared to patients with YKL-40 below the age-corrected 95th percentile. The results of multivariable analysis showed that YKL-40 was an independent biomarker of mortality; this was most significant in the first year. YKL-40 was a marker of prognosis in all disease categories. The HR for death was increased in patients with YKL-40 above the normal age-corrected 95th percentile in healthy subjects independent of type of disease (all P < 0.001).

CONCLUSION

The level of YKL-40 at admission is a strong predictor of overall mortality, independent of diagnosis and could be useful as a biomarker in the acute evaluation of all patients.