The chitinase 3-like protein human cartilage glycoprotein 39 inhibits cellular responses to the inflammatory cytokines interleukin-1 and tumour necrosis factor-alpha

Expression of CHI3L1 and CHIT1 in osteoarthritic rat cartilage model. A morphological study

Osteoarthritis is a degenerative joint disease, which affects millions of people around the world. It occurs when the protective cartilage at the end of bones wears over time, leading to loss of flexibility of the joint, pain and stiffness. The cause of osteoarthritis is unknown, but its development is associated with different factors, such as metabolic, genetic, mechanical and inflammatory ones. In recent years the biological role of chitinases has been studied in relation to different inflammatory diseases and more in particular the elevated levels of human cartilage glycoprotein 39 (CHI3L1) and chitotriosidase (CHIT1) have been reported in a variety of diseases including chronic inflammation and degenerative disorders. The aim of this study was to investigate, by immunohistochemistry, the distribution of CHI3L1 and CHIT1 in osteoarthritic and normal rat articular cartilage, to discover their potential role in the development of this disease. The hypothesis was that the expression of chitinases could increase in OA disease. Immunohistochemical analysis showed that CHI3L1 and CHIT1 staining was very strong in osteoarthritic cartilage, especially in the superficial areas of the cartilage most exposed to mechanical load, while it was weak or absent in normal cartilage. These findings suggest that these two chitinases could be functionally associated with the development of osteoarthritis and could be used as markers, so in the future they could have a role in the daily clinical practice to stage the severity of the disease. However, the longer-term in vivoand in vitro studies are needed to understand the exact mechanism of these molecules, their receptors and activities on cartilage tissue.

YKL-40 as a novel factor associated with inflammation and catabolic mechanisms in osteoarthritic joints

YKL-40 is associated with tissue injury and inflammation, and consequently to diseases in which these mechanisms lead to tissue degradation, for example, asthma and rheumatoid arthritis. The purpose of the present study was to investigate if YKL-40 is also a significant factor in osteoarthritis (OA) by assessing associations of YKL-40 with mediators related to the pathogenesis of OA: cartilage destructing matrix metalloproteinases (MMPs) and proinflammatory cytokines interleukin-6 (IL-6) and interleukin-17 (IL-17). Cartilage, synovial fluid (SF), and plasma samples were obtained from 100 OA patients undergoing total knee replacement surgery. SF levels of YKL-40 (1027.9 ± 78.3 ng/mL) were considerably higher than plasma levels (67.2 ± 4.5 ng/mL) and correlated with YKL-40 released from cartilage samples obtained from the same patients (r = 0.37, P = 0.010), indicating that YKL-40 is produced by OA cartilage. Interestingly, YKL-40 concentrations in OA SF correlated positively with MMP-1 (r = 0.36, P = 0.014), MMP-3 (r = 0.46, P = 0.001), IL-6 (r = 0.57, P < 0.001), and IL-17 (r = 0.52, P = 0.010) levels. Moreover, IL-6 and IL-17 enhanced YKL-40 production in human primary chondrocyte cultures. The present study introduces YKL-40 as a cartilage-derived factor associated with mediators of inflammation and cartilage destruction involved in the pathogenesis of OA.

The chitinase-like protein YKL-40 is not a useful biomarker for severe persistent asthma in children

BACKGROUND

The chitinase-like protein YKL-40 is thought to play a role in inflammation and tissue remodeling. In adults with severe asthma, YKL-40 is expressed in the airway and YKL-40 levels are elevated in the serum.

OBJECTIVE

To compare YKL-40 levels in children with severe persistent asthma with those in adults with severe persistent asthma and to determine whether YKL-40 levels correlate with increasing asthma severity in childhood asthma.

METHODS

In this prospective, cross-sectional study, 23 adults and 19 children with severe persistent asthma, 23 children with moderate persistent asthma, and 19 children with mild persistent asthma were enrolled. The following data were collected on each patient: spirometry, exhaled nitric oxide, percutaneous skin testing results to aeroallergens, peripheral eosinophils, serum IgE levels, and serum YKL-40 levels.

RESULTS

Compared with adults, children with severe persistent asthma had significantly lower YKL-40 levels, higher values for forced vital capacity and forced expiration volume in 1 second, higher serum IgE levels, and higher exhaled nitric oxide levels. YKL-40 levels did not correlate with increasing asthma severity in the pediatric cohort.

CONCLUSION

Severe persistent asthma in childhood is not associated with elevated YKL-40 levels, unlike in adults with severe persistent asthma. YKL-40 is not a useful biomarker for asthma severity in childhood asthma.

Chitinase-3-like protein 1 protects skeletal muscle from TNFα-induced inflammation and insulin resistance

CHI3L1 (chitinase-3-like protein 1) is a glycoprotein consisting of 383 amino acids with a molecular mass of 40 kDa, and its serum level is elevated in inflammatory diseases. Although CHI3L1 is described as a biomarker of inflammation, the function of this protein is not completely understood. In the present study, we examined the regulation of CHI3L1 in primary human skeletal muscle cells. Moreover, we analysed potential autocrine effects of CHI3L1. We show that myotubes express CHI3L1 in a differentiation-dependent manner. Furthermore, pro-inflammatory cytokines up-regulate CHI3L1 expression (6-fold) and release (3-fold). Importantly, CHI3L1 treatment blocked TNFα (tumour necrosis factor α)-induced inflammation by inhibiting NF-κB (nuclear factor κB) activation in skeletal muscle cells. We show that this effect is mediated via PAR2 (protease-activated receptor 2). In addition, CHI3L1 treatment diminished the TNFα-induced expression and secretion of IL (interleukin)-8, MCP1 (monocyte chemoattractant protein 1) and IL-6. In addition, impaired insulin action at the level of Akt and GSK3α/β (glycogen synthase kinase 3α/β) phosphoryl-ation and insulin-stimulated glucose uptake was normalized by CHI3L1. In conclusion, the novel myokine CHI3L1, which is induced by pro-inflammatory cytokines, can counteract TNFα-mediated inflammation and insulin resistance in human skeletal muscle cells, potentially involving an auto- and/or para-crine mechanism.

Antibody directed against human YKL-40 increases tumor volume in a human melanoma xenograft model in scid mice

Induced overexpression of the secretory protein YKL-40 promotes tumor growth in xenograft experiments. We investigated if targeting YKL-40 with a monoclonal antibody could inhibit tumor growth. YKL-40 expressing human melanoma cells (LOX) were injected subcutenously in Balb/c scid mice. Animals were treated with intraperitoneal injections of anti-YKL-40, isoptype control or PBS. Non-YKL-40 expressing human pancreatic carcinoma cell line PaCa 5061 served as additional control. MR imaging was used for evaluation of tumor growth. Two days after the first injections of anti-YKL-40, tumor volume had increased significantly compared with controls, whereas no effects were observed for control tumors from PaCa 5061 cells lacking YKL-40 expression. After 18 days, mean tumor size of the mice receiving repeated anti-YKL-40 injections was 1.82 g, >4 times higher than mean tumor size of the controls (0.42 g). The effect of anti-YKL-40 on the increase of tumor volume started within hours after injection and was dose dependent. Intratumoral hemorrhage was observed in the treated animals. The strong effect on tumor size indicates important roles for YKL-40 in melanoma growth and argues for a careful evaluation of antibody therapy directed against YKL-40.

Serum YKL-40 levels and chitotriosidase activity in patients with beta-thalassemia major

BACKGROUND

YKL-40 association with human disease has been the object of many years of investigation. β-thalassemia patients are affected by hepatic siderosis, which determines a fibrotic process and tissue remodelling. Chitotriosidase has been found to be increased in thalassemic patients returning to normal in patients submitted to bone marrow transplantation. YKL-40 is associated with macrophage activation in liver and in other tissues. The aim of the study was to analyse the level of serum YKL-40 and plasma chitotriosidase activity of patients with beta-thalassemia to assess whether their expression correlates with liver disease and degree of liver siderosis.

METHODS

Expression of YKL-40 and chitotriosidase as a marker of inflammation in 69 thalassemic patients were evaluated. We sought to investigate whether these two chitinases could be considered as a significant biomarker to evaluate therapy effectiveness.

RESULTS

Surprisingly we found normal value of YKL-40. We, also, analysed chitotriosidase activity in the same patients that was slightly increased as a consequence of macrophage activation.

CONCLUSIONS

These data would suggest a good treatment for these patients.

Determination of chitinases family during osteoclastogenesis

Mammalian chitinases consisting of CHIA, CHIT1, CHI3L1, CHI3L2 and CHID1 exert important biological roles in the monocyte lineage and chronic inflammatory diseases. Pathological bone resorption is a cause of significant morbidity in diseases affecting the skeleton such as rheumatoid arthritis, osteoporosis, periodontitis and cancer metastasis. The biologic role of chitinases in bone resorption is poorly understood. In this study, we evaluated the expression of the chitinases family during osteoclast differentiation. The expression of CHIA, CHI3L2 and CHID1 resulted unchanged during osteoclast differentiation, whereas CHIT1 and CHI3L1 increased significantly. We also observed that CHIT1 and CHI3L1 are involved in osteoclast function. Indeed, silencing CHIT1 and CHI3L1 with siRNA resulted in a significant decrease in bone resorption activity. In addition, transfection with CHIT1 or CHI3L1 siRNA and co-transfection with both decreased the levels of the pro-differentiative marker MMP9. Overall, these discoveries reveal a novel and crucial role for both CHIT1 and CHI3L1 in promoting bone resorption and identifying new potential candidate markers for therapeutic targeting.

Chitinase 3 like 1 is associated with tumor angiogenesis in cervical cancer

Elevated serum levels of a secreted glycoprotein chitinase 3 like 1 (CHI3L1) are associated with poor prognosis and short survival time of patients with cervical cancer (CxCa). Our previous microarray data showed the increased expression of CHI3L1 in invasive CxCa compared to normal tissue, implicating a potential role of CHI3L1 in CxCa. To establish the pathological role of CHI3L1 in the development of CxCa, this study focused on its expression in CxCa and angiogenic impacts in tumor vessel formation. CHI3L1 activated angiogenesis by promoting endothelial cell migration and tube formation in vitro but failed to protect CxCa cell lines, CaSki and HeLa against apoptosis induced by γ-irradiation. In addition, the capability of CHI3L1 to induce proliferation and migration of CaSki and HeLa cells was cell type specific. In an analysis of 103 specimens from CxCa patients, increased expression levels of CHI3L1 mRNA and protein in invasive CxCa were 4-fold (P<0.05) and 2-fold (P<0.01), respectively, stronger than those in normal subjects. The immunostaining of CHI3L1 was positively correlated with VEGF expression (P=0.0019) and microvessel density (P=0.0110). Moreover, CHI3L1 expression was also positively associated with cancer metastasis (P=0.011). The data suggest the crucial role of CHI3L1 by promoting angiogenesis, which may contribute to the development and progression of CxCa. The findings help establish CHI3L1 as a prognostic biomarker and therapeutic target for CxCa patients.

The Effect of Recombinant Human Interleukin-6 on Osteogenic Differentiation and YKL-40 Expression in Human, Bone Marrow-Derived Mesenchymal Stem Cells

Human mesenchymal stem cells are an attractive cell source for tissue engineering and regenerative medicine applications, especially because of their differentiation potential toward the mesenchymal lineage. Furthermore, this cell type participates in the regeneration of tissue damage and plays an important role in immunity. Similarly, chitinase-like proteins have been proposed to aid in tissue remodeling, inflammation, and differentiation processes. The chitinase-like protein YKL-40 in particular is indicated in preventing damage to the extracellular matrix in response to proinflammatory cytokines, even though its biological function remains speculative. Finally, interleukin (IL)-6, a pleiotropic acute phase protein, participates in the regulation of bone turnover and immunoregulation. The physiological role of IL-6 in bone homeostasis is complex, exerting different effects on osteoblasts and osteoclasts depending on their differentiation stage. The aim of this study was to determine the effect of recombinant human IL-6 (5 ng/mL) on YKL-40 expression and osteogenic differentiation of human mesenchymal stem cells. Recombinant human IL-6 induced a donor-dependent change in mineralization and significantly promoted YKL-40 protein secretion. However, YKL-40 gene expression remained unaffected, and no statistically significant differences in the expression of osteogenic marker genes could be observed.

Novel methylxanthine derivative-mediated anti-inflammatory effects in inflammatory bowel disease

Family 18 chitinases have a binding capacity with chitin, a polymer of N-acetylglucosamine. Recent studies strongly suggested that chitinase 3-like 1 (CHI3L1, also known as YKL-40) and acidic mammalian chitinase, the two major members of family 18 chitinases, play a pivotal role in the pathogenesis of inflammatory bowel disease (IBD), bronchial asthma and several other inflammatory disorders. Based on the data from high-throughput screening, it has been found that three methylxanthine derivatives, caffeine, theophylline, and pentoxifylline, have competitive inhibitory effects against a fungal family 18 chitinase by specifically interacting with conserved tryptophans in the active site of this protein. Methylxanthine derivatives are also known as adenosine receptor antagonists, phosphodiesterase inhibitors and histone deacetylase inducers. Anti-inflammatory effects of methylxanthine derivatives have been well-documented in the literature. For example, a beneficial link between coffee or caffeine consumption and type 2 diabetes as well as liver cirrhosis has been reported. Furthermore, theophylline has a long history of being used as a bronchodilator in asthma therapy, and pentoxifylline has an immuno-modulating effect for peripheral vascular disease. However, it is still largely unknown whether these methylxanthine derivative-mediated anti-inflammatory effects are associated with the inhibition of CHI3L1-induced cytoplasmic signaling cascades in epithelial cells. In this review article we will examine the above possibility and summarize the biological significance of methylxanthine derivatives in intestinal epithelial cells. We hope that this study will provide a rationale for the development of methylxanthine derivatives, in particular caffeine, -based anti-inflammatory therapeutics in the field of IBD and IBD-associated carcinogenesis.

Cells from the skin of patients with systemic sclerosis secrete chitinase 3-like protein 1

Background

The chitinase-like protein, Chi3L1, is associated with increased fibrotic activity as well as inflammatory processes. The capacity of skin cells from systemic sclerosis (SSc) patients to produce Chi3L1, and the stimulation of its synthesis by cytokines or growth factors known to be associated with SSc, was investigated.

Methods

Cells were isolated from forearm and/or abdomen skin biopsies taken from SSc patients and normal individuals and stimulated with cytokines and growth factors to assess Chi3L1 expression. Chi3L1-expressing cells were characterized by immunohistochemical staining.

Results

Chi3L1 was not secreted by skin cells from normal individuals nor was its synthesis induced by any of the cytokines or growth factors investigated. In contrast, Chi3L1 secretion was induced by OSM or IL-1 in cells from all forearm biopsies of SSc patients, and endogenous secretion in the absence of cytokines was detected in several specimens. Patients with Chi3L1-producing cells at both the arm and abdomen had a disease duration of less than 3 years. Endogenous Chi3L1 production was not a property of the major fibroblast population nor of myofibroblasts, but rather was related to the presence of stem-like cells not present in normal skin. Other cells, however, contributed to the upregulation of Chi3L1 by OSM.

Conclusions

The emergence of cells primed to respond to OSM with increased Chi3L1 production appears to be associated with pathological processes active in SSc.

General significance

The presence of progenitor cells expressing the chilectin Chi3L1 in SSc skin appears to play a role in the initiation of the disease process.

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Cells isolated from the skin of scleroderma patients secrete Chi3L1.

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Chi3L1 production is stimulated by oncostatin M or interleukin 1.

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Patients with Chi3L1 producing cells have disease duration of < 3 years.

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Chi3L1 production is a property of stem-like cells not present in normal skin.

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Other cells contribute to Chi3L1 upregulation by oncostatin M.

Plasma YKL-40 predicts 10-year cardiovascular and all-cause mortality in individuals with type 2 diabetes

OBJECTIVE

Elevated YKL-40 concentrations have been observed in both coronary heart disease (CHD) and diabetes. Thus, YKL-40 may play a role in pathogenesis of CHD in patients with diabetes. We evaluated whether plasma YKL-40 concentration can predict all-cause and cardiovascular mortality in individuals with type 2 diabetes.

DESIGN

This is a prospective, observational study.

PATIENTS

A total of 628 subjects with type 2 diabetes were recruited between July 1996 and June 2003.

MEASUREMENTS

Plasma YKL-40 concentrations were measured via enzyme-linked immunosorbent assay (ELISA). The cohort was followed up until 31 December 2008, when vital status and causes of death were obtained. Survival analysis and concordance statistics were performed. All-cause and cardiovascular mortalities were documented.

RESULTS

There were 153 (24·36%) mortalities, including 48 participants (7·64%) who died from cardiovascular diseases (CVDs). Participants with higher plasma YKL-40 (defined with a level above the median of 87·5 μg/l) had an increased risk of mortality. After adjusting for confounding variables, the hazard ratios (HR) for all-cause and cardiovascular mortality in participants with higher plasma YKL-40 were 1·97 (95% CI, 1·31-2·95, P < 0·01) and 2·45 (95% CI, 1·11-5·37, P < 0·05). The results remained similar after adjustment for age. Concordance statistics revealed that plasma YKL-40 concentration significantly increases the predictive power for both all-cause and cardiovascular mortality in different models.

CONCLUSIONS

Plasma YKL-40 concentration is an independent predictor of 10-year all-cause and cardiovascular mortality in subjects with type 2 diabetes. Further investigations on the role of YKL-40 in the pathogenesis of CVD are required to elucidate the underlying mechanisms.

Chitinases: in agriculture and human healthcare

Biological control of phytopathogenic fungi and insects continues to inspire the research and development of environmentally friendly bioactive alternatives. Potentially lytic enzymes, chitinases can act as a biocontrol agent against agriculturally important fungi and insects. The cell wall in fungi and protective covers, i.e. cuticle in insects shares a key structural polymer, chitin, a β-1,4-linked N-acetylglucosamine polymer. Therefore, it is advantageous to develop a common biocontrol agent against both of these groups. As chitin is absent in plants and mammals, targeting its metabolism will signify an eco-friendly strategy for the control of agriculturally important fungi and insects but is innocuous to mammals, plants, beneficial insects and other organisms. In addition, development of chitinase transgenic plant varieties probably holds the most promising method for augmenting agricultural crop protection and productivity, when properly integrated into traditional systems. Recently, human proteins with chitinase activity and chitinase-like proteins were identified and established as biomarkers for human diseases. This review covers the recent advances of chitinases as a biocontrol agent and its various applications including preparation of medically important chitooligosaccharides, bioconversion of chitin as well as in implementing chitinases as diagnostic and prognostic markers for numerous diseases and the prospect of their future utilization.

Plasma YKL-40 and CHI3L1 in systemic inflammation and sepsis-experience from two prospective cohorts

YKL-40, derived from the CHI3L1 gene, has been associated with outcome of infectious and inflammatory diseases. We hypothesized that plasma YKL-40 concentrations and CHI3L1 genotype could be used as prognostic biomarkers in the assessment of systemic inflammatory response syndrome (SIRS) and sepsis. The objective of the study was to assess the prognostic value of plasma YKL-40 and CHI3L1 genotype in patients with SIRS and sepsis. Plasma YKL-40 and CHI3L1 genotype (rs4950928) were analyzed at time of admission to intensive care units (ICU), in two prospective cohorts of consecutive SIRS patients (cohort 1, n=272; cohort 2, n=502). The plasma YKL-40 cut-off for predicting survival was determined in cohort 1 by receiver operator characteristic analyses and validated in cohort 2. In cohort 1 patients with plasma YKL-40 ≤505ng/ml (area under the curve 0.64 (95% confidence interval (CI) 0.57-0.70), p<0.001, sensitivity 53%, specificity 76%) had superior day 90 survival (81% vs. 55%, p<0.001, hazard ratio (HR) 2.29 (95% CI 1.29-4.07)). In the second cohort plasma YKL-40 ≤505ng/ml was also associated with superior survival (61% vs. 38%, p<0.001, HR 1.43 (1.03-1.99)). CHI3L1 minor allele homozygosity was associated with low plasma YKL-40 at time of admission (p=0.002) and no variation (p=0.462) in concentrations throughout the first 14 days in the ICU, but this was not associated with better survival. In conclusion patients with SIRS and sepsis, plasma YKL-40 ≤505ng/ml at time of ICU admission was associated with better survival. However, this association was not observed for patients homozygous for the low expressing YKL-40 CHI3L1 allele.

Validation of terminal peptide of procollagen III for the detection and assessment of nonalcoholic steatohepatitis in patients with nonalcoholic fatty liver disease

Liver biopsy is the reference standard for the detection of nonalcoholic steatohepatitis (NASH) within nonalcoholic fatty liver disease (NAFLD). The aim of this study was to identify a biomarker of NASH in patients without significant fibrosis. In all, 172 patients from two centers with biopsy-proven NAFLD were included in this study. Eighty-four patients from a single center were included as a derivation cohort and 88 patients from a second center were included as a validation cohort. Serum samples were tested for candidate markers of fibrosis and inflammation alongside hematological and biochemical markers. Among patients without advanced fibrosis, terminal peptide of procollagen III (PIIINP) was the only marker found to be associated with a histological diagnosis of NASH in both cohorts. PIIINP also correlated with the total NAFLD activity score (NAS) and its constituent components (P < 0.001). Area under receiver operating characteristic curve (AUROC) for PIIINP in discriminating between NASH and simple steatosis (SS) was 0.77-0.82 in patients with F0-2 fibrosis and 0.82-0.84 in patients with F0-3 fibrosis. PIIINP was elevated in patients with advanced fibrosis, the overwhelming majority of whom had NASH. When incorporating patients with all degrees of fibrosis from both cohorts, PIIINP was able to discriminate between patients with SS and those with NASH or advanced fibrosis with AUROC 0.85-0.87.

CONCLUSION

PIIINP discriminates between SS and NASH or advanced fibrosis. The use of a single biomarker in this context will be of clinical utility in detecting the minority of patients with NAFLD who have NASH or advanced fibrosis related to NASH.

Endotoxins affect bioactivity of chitosan derivatives in cultures of bone marrow-derived human mesenchymal stem cells

Biomaterials research has been expanding over the last decade, in part to provide improved medical devices for the treatment of orthopedic tissue injuries. In the quest to provide the best performance combined with low cost for medical implants, an increasing number of non-chemists have entered the field of biomaterials research without the profound knowledge of chemistry needed to understand the complex interaction mechanisms and characteristics of natural substances. Likewise, non-biologists often lack understanding when it comes to the presence of the contaminating biota frequently found in natural substances. This lack of knowledge by researchers in the field, combined with sensitive in vitro cell-based assays, can lead to inaccurate evaluation of biomaterials. Hence, there should be both an active effort to assemble multi-disciplinary teams and a genuine concern for the possible effects of contamination on in vitro assays. Here, we show that the presence of bacterial endotoxins in chitosan derivatives can result in false-positive results, profoundly altering product performance in in vitro assays. False-positive results through uncritical use of natural substances in vitro can be avoided by proper endotoxin testing and careful evaluation of cytokine secretion patterns.

Significant association of elevated concentration of plasma YKL-40 with disease severity in patients with pelvic inflammatory disease

INTRODUCTION

To date, no study reports the implication of YKL-40 in pelvic inflammatory disease (PID). Therefore, we investigate the levels of plasma YKL-40 in patients with PID and further associate its expression with the severity of disease.

METHODS

We designed a hospital-based case-control study with approximate 1:1 ratio and consecutively recruited 64 patients with PID and 70 control women. We collected blood samples from 64 women with PID before and after they received treatment and 70 control women to detect levels of plasma YKL-40 and C-reactive protein (CRP) as well as white blood cell and neutrophil counts.

RESULTS

The results revealed that levels of plasma YKL-40 were significantly elevated in patients with PID as compared to those in controls (38.36 vs. 21.69 ng/ml, P = 0.001) but the significant difference was restricted to women aged 30 years or old after age stratification (56.75 vs. 23.61 ng/ml, P ≤ 0.001). It declined significantly after they received treatment (median: 38.36 vs. 27.54 ng/ml; P ≤ 0.001). Although both plasma YKL-40 and CRP were elevated in patients with tubo-ovarian abscess, PID patients with surgery exhibited higher YKL-40 concentration than those without surgery (median: 82.05 vs. 30.19 ng/ml, P = 0.005) and only plasma YKL-40 was significantly associated with the length of the hospital stay (P ≤ 0.001, R = 0.604).

CONCLUSION

We conclude that once individuals are diagnosed to have PID, YKL-40 may act as a biomarker to predict the severity and clinical outcome of the disease.

Increased levels of YKL-40 and interleukin 6 in patients with chronic pancreatitis and secondary diabetes

OBJECTIVES

Circulating levels of YKL-40 and interleukin 6 (IL-6) are elevated in patients with type 2 diabetes. We aimed to evaluate YKL-40 levels in patients with chronic pancreatitis (CP) with and without secondary diabetes mellitus (DM) to investigate whether elevated plasma YKL-40 could play a primary role in the pathogenesis of type 2 diabetes or rather represent a consequence of the diabetic state.

METHODS

Plasma levels of YKL-40 and IL-6 were measured during an oral glucose tolerance test in 8 patients with CP and secondary DM, 8 patients with CP and normal glucose tolerance (NGT), and 8 healthy control subjects (CTRLs).

RESULTS

Plasma YKL-40 and IL-6 were significantly higher in patients with CP and secondary DM (YKL-40, mean [95% confidence interval], 113 [60-215 ng/mL]; IL-6, 4.6 [2.3-9.1 pg/mL]) compared to patients with CP and NGT (YKL-40, 42 [28-63 ng/mL]; IL-6, 1.4 [0.8-2.4 pg/mL]) and healthy control subjects (YKL-40, 46 [31-69 ng/mL]; IL-6, 1.4 [0.8-2.4 pg/mL]).

CONCLUSIONS

Patients with CP and secondary DM have elevated levels of YKL-40 and IL-6 compared to CP patients with NGT and healthy subjects, suggesting that YKL-40 is not a primary mediator of DM but a consequence of the diabetic state.

Human YKL-39 is a pseudo-chitinase with retained chitooligosaccharide-binding properties

The chitinase-like proteins YKL-39 (chitinase 3-like-2) and YKL-40 (chitinase 3-like-1) are highly expressed in a number of human cells independent of their origin (mesenchymal, epithelial or haemapoietic). Elevated serum levels of YKL-40 have been associated with a negative outcome in a number of diseases ranging from cancer to inflammation and asthma. YKL-39 expression has been associated with osteoarthritis. However, despite the reported association with disease, the physiological or pathological role of these proteins is still very poorly understood. Although YKL-39 is homologous to the two family 18 chitinases in the human genome, it has been reported to lack any chitinase activity. In the present study, we show that human YKL-39 possesses a chitinase-like fold, but lacks key active-site residues required for catalysis. A glycan screen identified oligomers of N-acetylglucosamine as preferred binding partners. YKL-39 binds chitooligosaccharides and a newly synthesized derivative of the bisdionin chitinase-inhibitor class with micromolar affinity, through a number of conserved tryptophan residues. Strikingly, the chitinase activity of YKL-39 was recovered by reverting two non-conservative substitutions in the active site to those found in the active enzymes, suggesting that YKL-39 is a pseudo-chitinase with retention of chitinase-like ligand-binding properties.

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

Background

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

Methodology/Principal Findings

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

Conclusions/Signficance

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

Upcoming candidate cerebrospinal fluid biomarkers of Alzheimer's disease

Dementia due to Alzheimer's disease (AD) is estimated to reach epidemic proportions by the year 2030. Given the limited accuracy of current AD clinical diagnosis, biomarkers of AD pathologies are currently being sought. Reductions in cerebrospinal fluid levels of β-amyloid 42 (a marker of amyloid plaques) and elevations in tau species (markers of neurofibrillary tangles and/or neurodegeneration) are well-established as biomarkers useful for AD diagnosis and prognosis. However, novel markers for other features of AD pathophysiology (e.g., β-amyloid processing, neuroinflammation and neuronal stress/dysfunction) and for other non-AD dementias are required to improve the accuracy of AD disease diagnosis, prognosis, staging and therapeutic monitoring (theragnosis). This article discusses the potential of several promising novel cerebrospinal fluid analytes, highlights the next steps critical for advancement in the field, and provides a prediction on how the field may evolve in 5-10 years.

Review: molecular pathology in adult high-grade gliomas: from molecular diagnostics to target therapies

The classification of malignant gliomas is moving from a morphology-based guide to a system built on molecular criteria. The development of a genomic landscape for gliomas and a better understanding of its functional consequences have led to the development of internally consistent molecular classifiers. However, development of a biologically insightful classification to guide therapy is still a work in progress. Response to targeted treatments is based not only on the presence of drugable targets, but rather on the molecular circuitry of the cells. Further, tumours are heterogeneous and change and adapt in response to drugs. Therefore, the challenge of developing molecular classifiers that provide meaningful ways to stratify patients for therapy remains a major challenge for the field. In this review, we examine the potential role of MGMT methylation, IDH1/2 mutations, 1p/19q deletions, aberrant epidermal growth factor receptor and PI3K pathways, abnormal p53/Rb pathways, cancer stem-cell markers and microRNAs as prognostic and predictive molecular markers in the setting of adult high-grade gliomas and we outline the clinically relevant subtypes of glioblastoma with genomic, transcriptomic and proteomic integrated analyses. Furthermore, we describe how these advances, especially in epidermal growth factor receptor/PI3K/mTOR signalling pathway, affect our approaches towards targeted therapy, raising new challenges and identifying new leads.

Performance of a multi-biomarker score measuring rheumatoid arthritis disease activity in the CAMERA tight control study

OBJECTIVES

To evaluate the performance of individual biomarkers and a multi-biomarker disease activity (MBDA) score in the early rheumatoid arthritis (RA) patient population from the computer assisted management in early rheumatoid arthritis (CAMERA) study.

METHODS

Twenty biomarkers were measured in the CAMERA cohort, in which patients were treated with either intensive or conventional methotrexate-based treatment strategies. The MBDA score was calculated using the concentrations of 12 biomarkers (SAA, IL-6, TNF-RI, VEGF-A, MMP-1, YKL-40, MMP-3, EGF, VCAM-1, leptin, resistin and CRP) according to a previously trained algorithm. The performance of the scores was evaluated relative to clinical disease activity assessments. Change in MBDA score over time was assessed by paired Wilcoxon rank sum test. Logistic regression was used to evaluate the ability of disease activity measures to predict radiographic progression.

RESULTS

The MBDA score had a significant correlation with the disease activity score based on 28 joints-C reactive protein (DAS28-CRP) (r=0.72; p<0.001) and an area under the receiver operating characteristic curve for distinguishing remission/low from moderate/high disease activity of 0.86 (p<0.001) using a DAS28-CRP cut-off of 2.7. In multivariate analysis the MBDA score, but not CRP, was an independent predictor of disease activity measures. Additionally, mean (SD) MBDA score decreased from 53 (18) at baseline to 39 (16) at 6 months in response to study therapy (p<0.0001). Neither MBDA score nor clinical variables were predictive of radiographic progression.

CONCLUSIONS

This multi-biomarker test performed well in the assessment of disease activity in RA patients in the CAMERA study. Upon further validation, this test could be used to complement currently available disease activity measures and improve patient care and outcomes.

Glucosamine increases the expression of YKL-40 and osteogenic marker genes in hMSC during osteogenic differentiation

Human mesenchymal stem cells (hMSC) can be expanded in vitro and differentiated towards osteogenic, chondrogenic or adipogenic lineages, making them an attractive source for tissue engineering and regenerative medicine. Chitinase-like-proteins (CLPs) belong to the family 18 glycosyl hydrolases and are believed to play a role in inflammation and tissue remodelling. The aim of this study was to determine the effect of the aminosugar glucosamine on the expression of the CLP YKL-40 during osteogenic differentiation of hMSC. Glucosamine did not affect multipotency of hMSC nor proliferation rate of undifferentiated hMSC. YKL-40 was expressed during both expansion of undifferentiated hMSC and during osteogenic differentiation. A slight but nonsignificant increase in YKL-40 expression was observed with glucosamine, accompanied by a pH-dependent delay in mineralization. However, glucosamine induced higher expression of osteogenic marker genes.

Elevated circulating levels of the serum acute-phase protein YKL-40 (chitinase 3-like protein 1) are a marker of obesity and insulin resistance in prepubertal children

YKL-40 (chitinase 3-like protein 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. It has also been associated with endothelial dysfunction and diabetes in adults. Its role in childhood obesity has not been evaluated yet. Our aim was to evaluate the associations of serum YKL-40 levels with markers of obesity, inflammation, and insulin resistance in children. Forty-one obese prepubertal children and 41 age- and sex-matched lean controls were included, and serum YKL-40 levels were determined. Body mass index (BMI), blood pressure (BP), body fat percentage, fasting glucose, insulin, homeostasis model assessment for insulin resistance (HOMA-IR) index, whole-body insulin sensitivity index, lipids, white blood cell (WBC) count, C-reactive protein, and fibrinogen levels were also assessed. Obese children had higher YKL-40 levels compared with controls (P = .003). Insulin-resistant individuals showed higher YKL-40 compared with non-insulin-resistant individuals after adjusting for age and BMI (adjusted P = .039). Serum YKL-40 levels were positively correlated with age, BMI, body fat percentage, fasting glucose and insulin, HOMA-IR index, whole-body insulin sensitivity index, systolic BP, mean BP, and WBC count (P < .05). After adjustment for age, sex, BMI, WBC count, and systolic BP, HOMA-IR index remained significantly associated with YKL-40 levels (P < .001). The study suggests that YKL-40 levels are elevated in obese youth and represent a marker of insulin resistance even in childhood. Prospective studies are needed to determine whether children with elevated YKL-40 levels are at higher risk for future cardiovascular disease.

YKL-40 is differentially expressed in human embryonic stem cells and in cell progeny of the three germ layers

The secreted glycoprotein YKL-40 participates in cell differentiation, inflammation, and cancer progression. High YKL-40 expression is reported during early human development, but its functions are unknown. Six human embryonic stem cell (hESC) lines were cultured in an atmosphere of low or high oxygen tension, in culture medium with or without basic fibroblast growth factor, and on feeder layers comprising mouse embryonic fibroblasts or human foreskin fibroblasts to evaluate whether hESCs and their progeny produced YKL-40 and to characterize YKL-40 expression during differentiation. Secreted YKL-40 protein and YKL-40 mRNA expression were measured by enzyme-linked immunosorbent assay (ELISA) and quantitative RT-PCR. Serial-sectioned colonies were stained for YKL-40 protein and for pluripotent hESC (OCT4, NANOG) and germ layer (HNF-3β, PDX1, CD34, p63, nestin, PAX6) markers. Double-labeling showed YKL-40 expression in OCT4-positive hESCs, PAX6-positive neuroectodermal cells, and HNF-3β-positive endodermal cells. The differentiating progeny showed strong YKL-40 expression. Abrupt transition between YKL-40 and OCT4-positive hESCs and YKL-40-positive ecto- and neuroectodermal lineages was observed within the same epithelial-like layer. YKL-40-positive cells within deeper layers lacked contact with OCT4-positive cells. YKL-40 may be important in initial cell differentiation from hESCs toward ectoderm and neuroectoderm, with retained epithelial morphology, whereas later differentiation into endoderm and mesoderm involves a transition into the deeper layers of the colony.

Chitinase 3-like 1 promotes macrophage recruitment and angiogenesis in colorectal cancer

Chitinase 3-like 1 (CHI3L1), one of mammalian members of the chitinase family, is expressed in several types of human cancer, and elevated serum level of CHI3L1 is suggested to be a biomarker of poor prognosis in advanced cancer patients. However, the overall biological function of CHI3L1 in human cancers still remains unknown. Studies were performed to characterize the role of CHI3L1 in cancer pathophysiology utilizing human colorectal cancer samples and human cell lines. Plasma protein and tissue mRNA expression levels of CHI3L1 in colorectal cancer were strongly upregulated. Immunohistochemical analysis showed that CHI3L1 was expressed in cancer cells and CHI3L1 expression had a significant association with the number of infiltrated macrophages and microvessel density. By utilizing trans-well migration and tube formation assays, overexpression of CHI3L1 in SW480 cells (human colon cancer cells) enhanced the migration of THP-1 cells (human macrophage cells) and HUVECs (human endothelial cells), and the tube formation of HUVECs. The knockdown of CHI3L1 by RNA interference or the neutralization of CHI3L1 by anti-CHI3L1 antibody displayed strong suppression of CHI3L1-induced migration and tube formation. Cell proliferation assay showed that CHI3L1 overexpression significantly enhanced the proliferation of SW480 cells. ELISA analysis showed that CHI3L1 increased the secretion of inflammatory chemokines, IL-8 and MCP-1, from SW480 cells through mitogen-activated protein kinase (MAPK) signaling pathway. Both neutralization of IL-8 or MCP-1 and inhibition or knockdown of MAPK in SW480 cells significantly inhibited CHI3L1-induced migration and tube formation. In a xenograft mouse model, overexpression of CHI3L1 in HCT116 cells (human colon cancer cells) enhanced the tumor growth as well as macrophage infiltration and microvessel density. In conclusion, CHI3L1 expressed in colon cancer cells promotes cancer cell proliferation, macrophage recruitment and angiogenesis. Thus, the inhibition of CHI3L1 activity may be a novel therapeutic strategy for human colorectal cancer.

Induction of proinflammatory mediators by CHI3L1 is reduced by chitin treatment: decreased tumor metastasis in a breast cancer model

Disseminated metastasis accounts for over 90% of breast cancer deaths. Recently, elevated serum levels of a glycoprotein known as chitinase-3 like-protein-1 (CHI3L1) has been correlated with poor prognosis and shorter survival of patients with metastatic breast cancer. In this study, we show that there are increased levels of CHI3L1 in plasma of tumor-bearing mice and that both tumor cells and immune cells express and secrete CHI3L1. However, the biological and physiological functions of CHI3L1 are still unclear. We demonstrate that while CHI3L1 has an inhibitory role in the expression of interferon-gamma (IFN-γ), CHI3L1 up-regulates pro-inflammatory mediators, C-chemokine ligand 2 (CCL2), chemokine CX motif ligand 2 (CXCL2) and matrix metalloproteinase-9 (MMP-9) all of which contribute to tumor growth and metastasis. We found that in vitro inhibition of CHI3L1 by siRNA suppressed the production of CCL2, CXCL2 and MMP-9 by macrophages. In vivo treatment of mammary tumor-bearing mice with chitin (β-(1-4)-poly-N-acetyl D-glucosamine), a TH(1) adjuvant and a ligand for CHI3L1, promoted immune effector functions with increased production of IFN-γ and decreased CCL2, CXCL2 and MMP-9 expression. In vivo administration of chitin to mammary tumor-bearing mice significantly decreased lung metastasis. These studies show that CHI3L1 plays a role in tumor progression and that chitin can inhibit the pleiotropic effects of CHI3L1 giving support to the idea that CHI3L1 is a useful therapeutic target for treatment of breast cancer.

A complex of nuclear factor I-X3 and STAT3 regulates astrocyte and glioma migration through the secreted glycoprotein YKL-40

Nuclear factor I-X3 (NFI-X3) is a newly identified splice variant of NFI-X that regulates expression of several astrocyte-specific markers, such as glial fibrillary acidic protein. Here, we identified a set of genes regulated by NFI-X3 that includes a gene encoding a secreted glycoprotein YKL-40. Although YKL-40 expression is up-regulated in glioblastoma multiforme, its regulation and functions in nontransformed cells of the central nervous system are widely unexplored. We find that expression of YKL-40 is activated during brain development and also differentiation of neural progenitors into astrocytes in vitro. Furthermore, YKL-40 is a migration factor for primary astrocytes, and its expression is controlled by both NFI-X3 and STAT3, which are known regulators of gliogenesis. Knockdown of NFI-X3 and STAT3 significantly reduced YKL-40 expression in astrocytes, whereas overexpression of NFI-X3 dramatically enhanced YKL-40 expression in glioma cells. Activation of STAT3 by oncostatin M induced YKL-40 expression in astrocytes, whereas expression of a dominant-negative STAT3 had a suppressive effect. Mechanistically, NFI-X3 and STAT3 form a complex that binds to weak regulatory elements in the YKL-40 promoter and activates transcription. We propose that NFI-X3 and STAT3 control the migration of differentiating astrocytes as well as migration and invasion of glioma cells via regulating YKL-40 expression.

Gene Encoding Chitinase 3-Like 1 Protein (CHI3L1) is a Putative Oncogene

An important task in understanding oncogenesis is the identification of those genes whose copy number and expression increase during tumorigenesis. Previously, in an effort to identify genes which could be used as molecular markers for glial tumors, we compared gene expression in glioblastoma to the normal brain cells. Among the genes with the most pronounced increased expression in tumors there was CHI3L1, encoding the secreted chitinase 3-like 1 protein (also known as HC gp-39 or YKL-40). Expression of CHI3L1 was found increased significantly in various tumors in comparison with corresponding normal tissues. Here we show that CHI3L1 can decrease the doubling time of 293 cells. We have also demonstrated that CHI3L1 allows the anchorage-independent growth in soft agar and, in addition, stable CHI3L1 expression made 293 cells tumorigenic: these cells stimulate the initiation of tumors after their xenograft transplantation into the Wistar rat brains. Thus, the overexpression of CHI3L1 is likely to be critical in the development of some tumors and when we gain more information about mechanisms of CHI3L1 oncogenicity, it could be used as one of the potential targets for anticancer therapy.

Role of chitin and chitinase/chitinase-like proteins in inflammation, tissue remodeling, and injury

The 18 glycosyl hydrolase family of chitinases is an ancient gene family that is widely expressed from prokaryotes to eukaryotes. In mammals, despite the absence of endogenous chitin, a number of chitinases and chitinase-like proteins (C/CLPs) have been identified. However, their roles have only recently begun to be elucidated. Acidic mammalian chitinase (AMCase) inhibits chitin-induced innate inflammation; augments chitin-free, allergen-induced Th2 inflammation; and mediates effector functions of IL-13. The CLPs BRP-39/YKL-40 (also termed chitinase 3-like 1) inhibit oxidant-induced lung injury, augments adaptive Th2 immunity, regulates apoptosis, stimulates alternative macrophage activation, and contributes to fibrosis and wound healing. In accord with these findings, levels of YKL-40 in the lung and serum are increased in asthma and other inflammatory and remodeling disorders and often correlate with disease severity. Our understanding of the roles of C/CLPs in inflammation, tissue remodeling, and tissue injury in health and disease is reviewed below.

Promoter polymorphisms in the chitinase 3-like 1 gene influence the serum concentration of YKL-40 in Danish patients with rheumatoid arthritis and in healthy subjects

Introduction

The present study investigates the association between single nucleotide polymorphisms (SNPs) in the chitinase 3-like 1 (CHI3L1) gene and serum concentrations of YKL-40 in Danish patients with rheumatoid arthritis (RA) and healthy controls as well as the association with RA in the Danish population. The CHI3L1 gene is located on chromosome 1q32.1 and encodes the YKL-40 glycoprotein. YKL-40 concentrations are elevated in the serum of patients with RA compared to healthy subjects, and YKL-40 has been suggested to be an auto-antigen and may play a role in development of RA and in inflammation.

Methods

Eight SNPs in the CHI3L1 gene and promotor were genotyped in 308 patients with RA and 605 controls (healthy blood donors) using TaqMan allele discrimination assays. Serum concentrations of YKL-40 were determined by an enzyme-linked immunosorbent assay (ELISA).

Results

We found significant association between the serum concentrations of YKL-40 and polymorphism in the CHI3L1 gene among both patients with RA and controls. The g.-131(C > G) polymorphism (rs4950928) was most strongly associated with age adjusted serum concentrations of YKL-40 in patients with RA (P < 2.4e-8) and controls (P < 2.2e-16). No significant allelic- or genotypic association with RA was found in this Danish cohort.

Conclusions

We suggest that the g.-131(C > G) promoter polymorphism has a substantial impact on serum concentrations of YKL-40 in patients with RA and healthy subjects. However, the polymorphism does not seem to confer risk to RA itself. The effect of CHI3L1 polymorphism on clinical outcome or the response to treatment in patients with RA remains to be investigated.

Carbohydrate-binding motif in chitinase 3-like 1 (CHI3L1/YKL-40) specifically activates Akt signaling pathway in colonic epithelial cells

Host-microbial interactions play a key role during the development of colitis. We have previously shown that chinase 3-like 1 (CHI3L1) is an inducible molecule overexpressed in colonic epithelial cells (CECs) under inflammatory conditions. In this study, we found that chitin-binding motif (CBM) of CHI3L1 is specifically associated with the CHI3L1-mediated activation of the Akt-signaling in CEC by transfecting the CBM-mutant CHI3L1 vectors in SW480 CECs. Downstream, CHI3L1 enhanced the secretion of IL-8 and TNFα in a dose-dependent manner. We previously show that 325 through 339 amino-acids in CBM are crucial for the biological function of CHI3L1. Here we demonstrated that 325th-339th residues of CBM in CHI3L1 is a critical region for the activation of Akt, IL-8 production, and for a specific cellular localization of CHI3L1. In conclusion, CBM region of CHI3L1 is critical in activating Akt signaling in CECs, and the activation may be associated with the development of chronic colitis.

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

Plasma levels of YKL-40 are elevated in patients with systemic infection, inflammatory disorders and cancer. Both monocytes/macrophages, neutrophils, and cancer cells have the capacity to produce YKL-40, but the regulation during the inflammatory response is unknown. To study the possible role of interleukin-6 (IL-6) and tumor necrosis factor (TNF)-α in the regulation of YKL-40 plasma levels, we included healthy men, who received either recombinant human (rh)IL-6 (n=6), rhTNF-α (n=8) or vehicle (n=7) for 3h. The plasma levels of IL-6 and TNF-α reached ∼ 150 and ∼ 18 pg/ml, respectively, during the infusions. Following the IL-6 infusion, the plasma level of YKL-40 increased from ∼ 30 to ∼ 57 ng/ml (p<0.05) at 24h, and returned to normal values after 48 h. The plasma level of YKL-40 did not change during TNF-α infusion or infusion of vehicle. These data demonstrate that IL-6, but not TNF-α, has a key-role in the regulation of plasma YKL-40 levels during inflammation.

Identification and validation of novel cerebrospinal fluid biomarkers for staging early Alzheimer's disease

BACKGROUND

Ideally, disease modifying therapies for Alzheimer disease (AD) will be applied during the 'preclinical' stage (pathology present with cognition intact) before severe neuronal damage occurs, or upon recognizing very mild cognitive impairment. Developing and judiciously administering such therapies will require biomarker panels to identify early AD pathology, classify disease stage, monitor pathological progression, and predict cognitive decline. To discover such biomarkers, we measured AD-associated changes in the cerebrospinal fluid (CSF) proteome.

METHODS AND FINDINGS

CSF samples from individuals with mild AD (Clinical Dementia Rating [CDR] 1) (n = 24) and cognitively normal controls (CDR 0) (n = 24) were subjected to two-dimensional difference-in-gel electrophoresis. Within 119 differentially-abundant gel features, mass spectrometry (LC-MS/MS) identified 47 proteins. For validation, eleven proteins were re-evaluated by enzyme-linked immunosorbent assays (ELISA). Six of these assays (NrCAM, YKL-40, chromogranin A, carnosinase I, transthyretin, cystatin C) distinguished CDR 1 and CDR 0 groups and were subsequently applied (with tau, p-tau181 and Aβ42 ELISAs) to a larger independent cohort (n = 292) that included individuals with very mild dementia (CDR 0.5). Receiver-operating characteristic curve analyses using stepwise logistic regression yielded optimal biomarker combinations to distinguish CDR 0 from CDR>0 (tau, YKL-40, NrCAM) and CDR 1 from CDR<1 (tau, chromogranin A, carnosinase I) with areas under the curve of 0.90 (0.85-0.94 95% confidence interval [CI]) and 0.88 (0.81-0.94 CI), respectively.

CONCLUSIONS

Four novel CSF biomarkers for AD (NrCAM, YKL-40, chromogranin A, carnosinase I) can improve the diagnostic accuracy of Aβ42 and tau. Together, these six markers describe six clinicopathological stages from cognitive normalcy to mild dementia, including stages defined by increased risk of cognitive decline. Such a panel might improve clinical trial efficiency by guiding subject enrollment and monitoring disease progression. Further studies will be required to validate this panel and evaluate its potential for distinguishing AD from other dementing conditions.

Purification, sequence characterization and effect of goat oviduct-specific glycoprotein on in vitro embryo development

Oviduct-specific glycoprotein (oviductin) plays an important role during fertilization and early embryonic development. The oviductin cDNA was successfully cloned and sequenced in goat, which possessed an open reading frame of 1620 nucleotides representing 539 amino acids. Predicted amino acid sequence showed very high identity with sheep (97%) followed by cow (94%), porcine (77%), hamster (69%), human (66%), rabbit (65%), mouse (64%) and baboon (62%). The bioinformatics analysis of the sequences revealed the presence of a signal sequence of 21 amino acids, one potential N-linked glycosylation site at position 402, 21 potential O-linked glycosylation sites and 36 potential phosphorylation sites. The native oviductin was purified from the oviductal tissue, which showed three distinct bands on SDS-PAGE and western blot (MW ~60-95 kDa). The predicted molecular weight of goat oviductin was 57.5 kDa, calculated from the amino acid sequences. The observed higher molecular weight has been attributed to the presence of large number of potential O-linked glycosylation sites. The lower concentration (10 μg/mL) of oviductin increased the cleavage rate, morula and blastocyst yield significantly (P < 0.05) as compared to higher concentration (100 μg/mL). Goat oviductin retarded the activity of pronase (0.1%) on zona solubility of oocytes significantly (P < 0.01).

YKL-40: a novel prognostic fluid biomarker for preclinical Alzheimer's disease

BACKGROUND

Disease-modifying therapies for Alzheimer's disease (AD) would be most effective during the preclinical stage (pathology present, cognition intact) before significant neuronal loss occurs. Therefore, biomarkers that detect AD pathology in its early stages and predict dementia onset and progression will be invaluable for patient care and efficient clinical trial design.

METHODS

AD-associated changes in cerebrospinal fluid (CSF) were measured using two-dimensional difference gel electrophoresis and liquid chromatography tandem mass spectrometry. Subsequently, CSF YKL-40 was measured by enzyme-linked immunosorbent assay in the discovery cohort (n = 47), validation cohort (n = 292) with paired plasma samples (n = 237), frontotemporal lobar degeneration (n=9) [corrected], and progressive supranuclear palsy (PSP; n = 6). Immunohistochemistry was performed to identify source(s) of YKL-40 in human AD brain.

RESULTS

Discovery and validation cohorts, showed higher mean CSF YKL-40 in very mild and mild AD-type dementia (Clinical Dementia Rating [CDR] 0.5 and 1) versus control subjects (CDR 0) and PSP subjects. Importantly, CSF YKL-40/Aβ42 ratio predicted risk of developing cognitive impairment (CDR 0 to CDR > 0 conversion), as well as the best CSF biomarkers identified to date, tau/Aβ42 and p-tau 181/Aβ42. Mean plasma YKL-40 was higher in CDR 0.5 and 1 versus CDR 0, and correlated with CSF levels. YKL-40 immunoreactivity labeled astrocytes near a subset of amyloid plaques, implicating YKL-40 in the neuroinflammatory response to Aβ deposition.

CONCLUSIONS

These data demonstrate that YKL-40, a putative indicator of neuroinflammation, is elevated in AD and, together with Aβ42, has potential prognostic utility as a biomarker for preclinical AD.

Plasma YKL-40 and total and disease-specific mortality in the general population

BACKGROUND

Increased plasma YKL-40 is associated with short-term survival in patients with cardiovascular disease and cancer. We tested the hypothesis that increased plasma YKL-40 is associated with total and disease-specific mortality in the general population.

METHODS

We measured plasma YKL-40 in 8899 study participants, aged 20-95 years, in the Copenhagen City Heart Study from the Danish general population who were followed for 16 years: 3059 died, 2158 had ischemic cardiovascular disease, 2271 had cancer, and 2820 had other diseases associated with increased YKL-40. Hazard ratios for early death and absolute 10-year mortality rates were calculated according to plasma YKL-40 percentile groupings computed within sex and age decade: 0%-33%, 34%-66%, 67%-90%, 91%-95%, and 96%-100%.

RESULTS

Median survival age decreased from 83 years for participants with plasma YKL-40 in category 0%-33% to 69 years in category 96%-100% (trend, P < 0.0001). Risk of early death was increased (multifactorially adjusted hazard ratios) by 10% for YKL-40 category 34%-66%, by 30% for 67%-90%, by 70% for 91%-95%, and by 90% for 96%-100% vs YKL-40 category 0%-33% (trend, P < 0.0001). Corresponding increases in participants with ischemic cardiovascular disease were 10%, 20%, 80%, and 60% (P < 0.0001); in those with cancer were 10%, 20%, 50%, and 70% (P < 0.0001); and in those with other diseases were 10%, 20%, 40%, and 60% (P < 0.0001). Highest absolute 10-year mortality rates were 78% and 90% in women and men, respectively, who were >70 years old, smoked, and were in YKL-40 category 96%-100%.

CONCLUSIONS

Increased plasma YKL-40 is associated with risk of early death from cardiovascular disease, cancer, and other diseases in the general population.

Homology modeling of 3D structure of human chitinase-like protein CHI3L2

The human genome encodes six proteins of family 18 glycosyl hydrolases, two active chitinases and four chitinase-like lectins (chi-lectins) lacking catalytic activity. The present article is dedicated to homology modeling of 3D structure of human chitinase 3-like 2 protein (CHI3L2), which is overexpressed in glial brain tumors, and its structural comparison with homologous chi-lectin CHI3L1. Two crystal structures of CHI3L1 in free state (Protein Data Bank codes 1HJX and 1NWR) were used as structural templates for the homology modeling by Modeller 9.7 program, and the best quality model structure was selected from the obtained model ensemble. Analysis of potential oligosaccharide-binding groove structures of CHI3L1 and CHI3L2 revealed significant differences between these two homologous proteins. 8 of 19 amino acid residues important for ligand binding are substituted in CHI3L2: Tyr34/Asp39, Trp69/Lys74, Trp71/Lys76, Trp99/Tyr104, Asn100/Leu105, Met204/Leu210, Tyr206/Phe212 and Arg263/His271. The differences between these residues could influence the structure of the ligand-binding groove and substantially change the ability of CHI3L2 to bind oligosaccharide ligands.

YKL-40: a new biomarker in cardiovascular disease?

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

Role of breast regression protein-39 in the pathogenesis of cigarette smoke-induced inflammation and emphysema

The exaggerated expression of chitinase-like protein YKL-40, the human homologue of breast regression protein-39 (BRP-39), was reported in a number of diseases, including chronic obstructive pulmonary disease (COPD). However, the in vivo roles of YKL-40 in normal physiology or in the pathogenesis of specific diseases such as COPD remain poorly understood. We hypothesized that BRP-39/YKL-40 plays an important role in the pathogenesis of cigarette smoke (CS)-induced emphysema. To test this hypothesis, 10-week-old wild-type and BRP-39 null mutant mice (BRP-39(-/-)) were exposed to room air (RA) and CS for up to 10 months. The expression of BRP-39 was significantly induced in macrophages, airway epithelial cells, and alveolar Type II cells in the lungs of CS-exposed mice compared with RA-exposed mice, at least in part via an IL-18 signaling-dependent pathway. The null mutation of BRP-39 significantly reduced CS-induced bronchoalveolar lavage and tissue inflammation. However, CS-induced epithelial cell apoptosis and alveolar destruction were further enhanced in the absence of BRP-39. Consistent with these findings in mice, the tissue expression of YKL-40 was significantly increased in the lungs of current smokers compared with the lungs of ex-smokers or nonsmokers. In addition, serum concentrations of YKL-40 were significantly higher in smokers with COPD than in nonsmokers or smokers without COPD. These studies demonstrate a novel regulatory role of BRP-39/YKL-40 in CS-induced inflammation and emphysematous destruction. These studies also underscore that maintaining physiologic concentrations of YKL-40 in the lung is therapeutically important in preventing excessive inflammatory responses or emphysematous alveolar destruction.

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

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

Association between YKL-40 and adult primary astrocytoma

BACKGROUND

The YKL-40 coding chitinase 3-like 1 gene is 1 of the most overexpressed genes in human glioblastomas. The objectives of this study were to explore YKL-40 protein expression status and World Health Organization (WHO) pathologic grades of primary human astrocytoma and to investigate the role of YKL-40 in the proliferation of both established and primary astrocytoma cells in vitro.

METHODS

WHO grade 1, 2, 3, and 4 primary astrocytomas (210 patients) were evaluated for YKL-40 protein expression status in immunohistochemical analyses. In addition, after transfection with a plasmid that contained YKL-40 small-interfering RNA (siRNA), cell proliferation and the cell cycle were measured with a cell-viability assay and flow cytometry. Expression levels of phosphorylated, total mitogen-activated protein kinase (MAPK) and protein kinase B (AKT) were detected by Western blot analysis.

RESULTS

The percentage of positive cells and the staining intensity differed significantly between different pathologic tumor grades (P < .001). The YKL-40 immunoreactivity score increased markedly with increased pathologic grade (F = 18.89; P < .001). In the in vitro experiment, the cell cycle was arrested in G(1) phase. An inhibitor of the p38 MAPK, SB203580, could partially abrogate the cell proliferation inhibition effect by siRNA treatment. The expression levels of phosphorylated extracellular signal-regulated kinase 1/2 and phosphorylated AKT were notably decreased in siRNA-transfected U87 cells. In contrast, the expression levels of phosphorylated p38 and phosphorylated c-jun N-terminal kinase 1 and 2 increased significantly (P < .01).

CONCLUSIONS

YKL-40 expression status correlated well with the pathologic grade of primary astrocytomas. The current results also indicted that YKL-40 plays a pivotal role in glioma cell proliferation through activation of the MAPK and AKT pathways. YKL-40 may be an attractive target for glioma therapy.

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

OBJECTIVES

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

DESIGN

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

RESULTS

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

CONCLUSIONS

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

Proteomic analysis by two-dimensional electrophoresis to identify the normal human chondrocyte proteome stimulated by tumor necrosis factor alpha and interleukin-1beta

OBJECTIVE

To determine the intracellular proteome of normal human chondrocytes stimulated with interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNFalpha) and to ascertain differences in the protein expression patterns of these 2 cytokines.

METHODS

Normal human knee cartilage chondrocytes were incubated for 48 hours without stimulation or stimulated with IL-1beta (5 ng/ml) or with TNFalpha (10 ng/ml). For each culture condition, protein extracts from 4 normal subjects were pooled and resolved using 2-dimensional electrophoresis. Protein spots were visualized with Sypro stain, and qualitative and quantitative analyses were performed using PDQuest software. Protein spots were then identified by mass spectrometry, using matrix-assisted laser desorption ionization-time-of-flight/time-of-flight technology.

RESULTS

We identified 37 spots by mass spectrometry (MS) or by MS/MS, corresponding to 35 different proteins. In IL-1beta-stimulated chondrocytes, IL-1beta was found to modulate 22 proteins, as compared with unstimulated chondrocytes. All of these proteins except connective tissue growth factor (CCND2) were up-regulated. Proteins involved in cellular metabolism and energy (23%) that were up-regulated or induced by IL-1beta included nicotinamide phosphoribosyltransferase, long-chain fatty acid-coenzyme A ligase 4, delta-aminolevulinic acid dehydratase, triosephosphate isomerase, and an isoform of glyceraldehyde-3-phosphate dehydrogenase. In TNFalpha-stimulated chondrocytes, TNFalpha was found to modulate 20 proteins, as compared with unstimulated chondrocytes. All of these except chitinase 3-like 1 (cartilage glycoprotein 39), proteasome activator complex subunit 2, and G3PDH, were up-regulated. Eighteen proteins were differently modulated by IL-1beta and TNFalpha. Of these, 45% were related to metabolism.

CONCLUSION

IL-1beta and TNFalpha induce different profiles of intracellular protein expression in healthy human chondrocytes. Most of the proteins that are differently regulated are proteins that are implicated in the generation of cellular energy and in glycolysis.