YKL-40: a novel marker shared by chronic inflammation and oncogenic transformation

Strong YKL-40 expression in the invasive tumor front of colorectal cancer-A pilot study

Тhe poor prognosis of patients initially diagnosed at an advanced stage of colorectal cancer (CRC) and the heterogeneity within the same tumor stage define the need for additional predictive biomarkers. Tumor buds are proposed as a poor prognostic factor for CRC, however, they are still not implemented into routine pathology reporting. In turn, the chitinase-3-like protein 1 (CHI3L1) also known as YKL-40, is regarded as a candidate circulating biomarker and therapeutic target in CRC. The aim of our study was to investigate tissue YKL-40 localization and tumor budding in CRC. Thirty-one CRC patients and normal colonic tissues were examined. The correlation between YKL-40 levels, tumor budding and clinocopathological parameters was evaluated by polychoric correlation analysis. The immunohistochemical assessment revealed high YKL-40 expression in CRC in contrast to normal mucosa. Specifically, intense YKL-40 staining was detected in the front of tumor invasion compared with tumor parenchyma and noncancerous tissue. We present novel data for increased YKL-40 expression in tumor buds within the front of tumor invasion. We assume that the combination of this morphological parameter with the tissue level of the pleotropic YKL-40 glycoprotein could serve as a future prognostic biomarker for CRC stratification and treatment.

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

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

The potential roles and mechanisms of Chitinase-3-like-1 in the pathogenesis of type 2-biased airway diseases

The immune modulation in the epithelium is a protective feature of the epithelial function in the mucosal airways. Dysfunction of the epithelium can lead to chronic allergic airway inflammatory diseases, such as chronic rhinosinusitis with nasal polyps (CRSwNP), allergic rhinitis (AR), and allergic asthma. Chitinase-3-like-1 (CHI3L1) is a key modulator in the epithelium against irritants, pathogens, and allergens and is involved in cancers, autoimmune diseases, neurological disorders, and other chronic diseases. Induction of epithelial cell-derived CHI3L1 is also confirmed to be implicated in the pathogenesis of Th2-related airway diseases like CRSwNP, AR, and allergic asthma, triggering a cascade of subsequent inflammatory reactions leading to the disease development. The techniques that block the biological function of CHI3L1 include small interfering RNA, neutralizing antibodies, and microRNAs and these methods proved to be successful in preclinical and clinical investigation in cancers, autoimmune diseases, asthma, and chronic obstructive pulmonary disease. Therefore, treatment with CHI3L1-blocking methods could open up therapeutic options for allergic airway diseases. This review article discusses the role of epithelial cell-derived CHI3L1 in the development of CRSwNP, AR, and allergic asthma and examines the use of CHI3L1 as a potential therapeutic agent for allergic airway diseases.

Biomarkers of Spinal Cord Injury in Patients Undergoing Complex Endovascular Aortic Repair Procedures-A Narrative Review of Current Literature

Complex endovascular aortic repair (coEVAR) of thoracoabdominal aortic aneurysms (TAAA) has greatly evolved in the past decades. Despite substantial improvements of postoperative care, spinal cord injury (SCI) remains the most devastating complication of coEVAR being associated with impaired patient outcome and having an impact on long-term survival. The rising number of challenges of coEVAR, essentially associated with an extensive coverage of critical blood vessels supplying the spinal cord, resulted in the implementation of dedicated SCI prevention protocols. In addition to maintenance of adequate spinal cord perfusion pressure (SCPP), early detection of SCI plays an integral role in intra- and postoperative patient care. However, this is challenging due to difficulties with clinical neurological examinations during patient sedation in the postoperative setting. There is a rising amount of evidence, suggesting that subclinical forms of SCI might be accompanied by an elevation of biochemical markers, specific to neuronal tissue damage. Addressing this hypothesis, several studies have attempted to assess the potential of selected biomarkers with regard to early SCI diagnosis. In this review, we discuss biomarkers measured in patients undergoing coEVAR. Once validated in future prospective clinical studies, biomarkers of neuronal tissue damage may potentially add to the armamentarium of modalities for early SCI diagnosis and risk stratification.

Chitinase 3 like 1 deficiency ameliorates lipopolysaccharide-induced acute liver injury by inhibition of M2 macrophage polarization

Chitinase 3-like-1 protein (CHI3L1) is involved in various infectious diseases, especially sepsis. Aberrant CHI3L1 expression potentially plays a critical role in chronic inflammation because a considerable number of macrophages are associated with immune/inflammatory diseases. In this study, we examined the effect of CHI3L1 on hepatic sepsis injury using a lipopolysaccharide (LPS)-induced model. LPS-treated CHI3L1 knockout (KO) mice exhibited a higher survival rate than LPS-treated CHI3L1 wild-type (WT) mice. In addition, hepatic injury-related enzyme levels (aspartate transaminase, alanine transaminase, and lactate dehydrogenase) decreased in CHI3L1 KO mice sera, suggesting attenuated LPS-induced septic liver damage in CHI3L1 KO mice. A greater reduction in the mRNA and protein expressions of M2 polarization markers, such as MRC1, ARG1, IL-10, and IL-4, was observed in LPS-induced CHI3L1 KO mice livers than in LPS-induced WT mice livers. Nonetheless, no change in the mRNA and protein expressions of M1 polarization markers, such as INOS, CD86, TNF-α, and IL6, was noted in LPS-induced CHI3L1 KO mice livers compared with those in LPS-induced WT and KO mice. Similar to the in vivo scenario, liver CHI3L1 depletion in LPS-treated HEP3B cells significantly decreased M2 polarization marker protein expression. However, M1 polarization marker protein expression did not differ significantly. These results suggest that CHI3L1 depletion decreases M2 macrophage polarization, and this effect is potentially associated with the alleviation of liver sepsis in CHI3L1 KO mice.

An adipocentric perspective on the development and progression of non-alcoholic fatty liver disease

Alongside the liver, white adipose tissue (WAT) is critical in regulating systemic energy homeostasis. Although each organ has its specialised functions, they must work coordinately to regulate whole-body metabolism. Adipose tissues and the liver are relatively resilient and can adapt to an energy surplus by facilitating triglyceride (TG) storage up to a certain threshold level without significant metabolic disturbances. However, lipid storage in WAT beyond a "personalised" adiposity threshold becomes dysfunctional, leading to metabolic inflexibility, progressive inflammation, and aberrant adipokine secretion. Moreover, the failure of adipose tissue to store and mobilise lipids results in systemic knock-on lipid overload, particularly in the liver. Factors contributing to hepatic lipid overload include lipids released from WAT, dietary fat intake, and enhanced de novo lipogenesis. In contrast, extrahepatic mechanisms counteracting toxic hepatic lipid overload entail coordinated compensation through oxidation of surplus fatty acids in brown adipose tissue and storage of fatty acids as TGs in WAT. Failure of these integrated homeostatic mechanisms leads to quantitative increases and qualitative alterations to the lipidome of the liver. Initially, hepatocytes preferentially accumulate TG species leading to a relatively "benign" non-alcoholic fatty liver. However, with time, inflammatory responses ensue, progressing into more severe conditions such as non-alcoholic steatohepatitis, cirrhosis, and hepatocellular carcinoma, in some individuals (often without an early prognostic clue). Herein, we highlight the pathogenic importance of obesity-induced "adipose tissue failure", resulting in decreased adipose tissue functionality (i.e. fat storage capacity and metabolic flexibility), in the development and progression of NAFL/NASH.

Chitinase-like proteins promoting tumorigenesis through disruption of cell polarity via enlarged endosomal vesicles

Introduction

Chitinase-like proteins (CLPs) are associated with tissue-remodeling and inflammation but also with several disorders, including fibrosis, atherosclerosis, allergies, and cancer. However, CLP's role in tumors is far from clear.

Methods

Here, we utilize Drosophila melanogaster and molecular genetics to investigate the function of CLPs (imaginal disc growth factors; Idgf's) in Ras^V12 dysplastic salivary glands.

Results and discussion

We find one of the Idgf's members, Idgf3, is transcriptionally induced in a JNK-dependent manner via a positive feedback loop mediated by reactive oxygen species (ROS). Moreover, Idgf3 accumulates in enlarged endosomal vesicles (EnVs) that promote tumor progression by disrupting cytoskeletal organization. The process is mediated via the downstream component, aSpectrin, which localizes to the EnVs. Our data provide new insight into CLP function in tumors and identifies specific targets for tumor control.

An Association of Chitinase-3 Like-Protein-1 With Neuronal Deterioration in Multiple Sclerosis

Elevated levels of Chitinase-3-like protein-1 (CHI3L1) in cerebrospinal fluid have previously been linked to inflammatory activity and disease progression in multiple sclerosis (MS) patients. This study aimed to investigate the presence of CHI3L1 in the brains of MS patients and in the cuprizone model in mice (CPZ), a model of toxic/metabolic demyelination and remyelination in different brain areas. In MS gray matter (GM), CHI3L1 was detected primarily in astrocytes and in a subset of pyramidal neurons. In neurons, CHI3L1 immunopositivity was associated with lipofuscin-like substance accumulation, a sign of cellular aging that can lead to cell death. The density of CHI3L1-positive neurons was found to be significantly higher in normal-appearing MS GM tissue compared to that of control subjects (p  =  .014). In MS white matter (WM), CHI3L1 was detected in astrocytes located within lesion areas, as well as in perivascular normal-appearing areas and in phagocytic cells from the initial phases of lesion development. In the CPZ model, the density of CHI3L1-positive cells was strongly associated with microglial activation in the WM and choroid plexus inflammation. Compared to controls, CHI3L1 immunopositivity in WM was increased from an early phase of CPZ exposure. In the GM, CHI3L1 immunopositivity increased later in the CPZ exposure phase, particularly in the deep GM region. These results indicate that CHI3L1 is associated with neuronal deterioration, pre-lesion pathology, along with inflammation in MS.

Upregulation of YKL-40 Promotes Metastatic Phenotype and Correlates with Poor Prognosis and Therapy Response in Patients with Colorectal Cancer

YKL-40 is a heparin- and chitin-binding glycoprotein that belongs to the family of glycosyl hydrolases but lacks enzymatic properties. It affects different (patho)physiological processes, including cancer. In different tumors, YKL-40 gene overexpression has been linked to higher cell proliferation, angiogenesis, and vasculogenic mimicry, migration, and invasion. Because, in colorectal cancer (CRC), the serological YKL-40 level may serve as a risk predictor and prognostic biomarker, we investigated the underlying mechanisms by which it may contribute to tumor progression and the clinical significance of its tissue expression in metastatic CRC. We demonstrated that high-YKL-40-expressing HCT116 and Caco2 cells showed increased motility, invasion, and proliferation. YKL-40 upregulation was associated with EMT signaling activation. In the AOM/DSS mouse model, as well as in tumors and sera from CRC patients, elevated YKL-40 levels correlated with high-grade tumors. In retrospective analyses of six independent cohorts of CRC patients, elevated YKL-40 expression correlated with shorter survival in patients with advanced CRC. Strikingly, high YKL-40 tissue levels showed a predictive value for a better response to cetuximab, even in patients with stage IV CRC and mutant KRAS, and worse sensitivity to oxaliplatin. Taken together, our findings establish that tissue YKL-40 overexpression enhances CRC metastatic potential, highlighting this gene as a novel prognostic candidate, a predictive biomarker for therapy response, and an attractive target for future therapy in CRC.

Can Micro RNA-24 Affect the Cardiovascular Morbidity in Systemic Lupus Erythematosus by Targeting YKL-40?

Background

Systemic lupus erythematosus (SLE) is an autoimmune disease with inflammatory nature. One of the leading causes of death in SLE patients is cardiovascular (CVS) morbidity. MiRNA-24 is highly expressed in vascular endothelial cells (VECs). This dysregulated expression pattern is associated with dysfunction or even damage of VECs and leads to the occurrence of cardiovascular diseases. YKL- 40 is an inflammatory glycoprotein involved in the pathogenesis of endothelial dysfunction and thereby atherosclerosis. In this work, we aimed at illustrating the possible role of miR-24 and its target YKL-40 in the pathogenesis of the CVS morbidity associated with SLE.

Methods

This work was conducted on 40 SLE patients and 40 healthy controls. Quantitative real-time PCR (qPCR) was done to estimate the expression level of miRNA-24 in serum. In addition, we measured the serum level of YKL-40 using ELISA.

Results

miR-24-fold change was found to be down-regulated, whereas serum YKL- 40 was up-regulated among SLE patients with observed significant and negative correlation between the two parameters.

Conclusion

Our study provided an insight about the role of miR-24 and its target serum YKL-40 protein in the development of SLE-related inflammation and atherosclerosis.

The Perspectives of Biomarkers in Predicting the Survival of the Renal Graft

Kidney transplantation (KT) is currently the elective approach for patients with end-stage renal disease. Although it is a safe choice for these patients, the early complications can lead to graft dysfunction. One of the most redoubtable complications is delayed graft function (DGF), having no specific treatment. The effects of DGF on the graft survival are large enough to justify the formulation of specific biological protocols. Therefore, discovering biomarkers of acute impairment in renal transplanted patients is required. Creatinine is a poor marker to establish the kidney injury. Estimated glomerular filtration rate together with creatinine is ready to approximately measure the kidney function. Different serum and urine proteins are being studied as possible predictive biomarkers for delayed graft function. This review will concentrate on recent and existing research which provide insight concerning the contribution of some molecules for the estimation and evaluation of graft function after kidney transplantation. Further studies examining various aspects of DGF after KT are urgently needed to address a hitherto less-known clinical question.

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

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

Serum YKL-40 levels in patients with multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a chronic inflammatory disease affecting the central nervous system. The YKL-40 protein, which is secreted from various cells that contribute to inflammation and infection, plays a role in immune regulation.

OBJECTIVE

This study investigated the serum YKL-40 levels of patients with clinically isolated syndrome (CIS) and MS.

METHODS

The participants was divided into three groups: 1) patients with CIS (n = 20); 2) patients with relapsing-remitting MS (RRMS; n = 39); and 3) healthy individuals (n = 35). The YKL-40 levels in serum samples obtained from the participants were measured using enzyme-linked immunoassays.

RESULTS

The median serum YKL-40 level was 20.2 ng/mL (range 9.8-75.9 ng/mL) in the patients with CIS, 22.7 ng/mL (range 13.4-57.9 ng/mL) in the patients with RRMS and 11.0 ng/mL (range 10.0-17.3 ng/mL) in the control group (p < 0.001). The serum YKL-40 levels in the patients with RRMS were correlated with the patients' expanded disability status scale scores and ages (p < 0.05). No relationships were determined between the serum YKL-40 levels and the other variables (p > 0.05). The serum YKL-40 levels were higher in the CIS group than in the MS group. These findings show that the serum YKL-40 levels were high even at the beginning of the disease. The serum YKL-40 levels were also not involved in the progression to clinically definite MS.

CONCLUSIONS

The findings from this study suggested that YKL-40 may be a useful marker for the inflammatory process of MS.

Salivary Total Protease Activity Based on a Broad-Spectrum Fluorescence Resonance Energy Transfer Approach to Monitor Induction and Resolution of Gingival Inflammation

OBJECTIVE

Salivary total protease and chitinase activities were measured by a broad-spectrum fluorescence resonance energy transfer approach as predictors of induction and resolution of gingival inflammation in healthy individuals by applying an experimental human gingivitis model.

METHODS

Dental biofilm accumulated (21 days, Induction Phase) by omitting oral hygiene practices followed by a 2-week Resolution Phase to restore gingival health in an experimental gingivitis study. Plaque accumulation, as assessed by the Turesky Modification of the Quigley-Hein Plaque Index (TQHPI), and gingival inflammation, assessed using the Modified Gingival Index (MGI), scores were recorded and unstimulated saliva was collected weekly. Saliva was analysed for total protein, albumin, total protease activity and chitinase activity (n = 18).

RESULTS

The TQHPI and MGI scores, as well as total protease activity, increased until day 21. After re-establishment of oral hygiene, gingival inflammation levels returned to values similar to baseline (day 0). Levels of protease activity decreased significantly, but not to baseline values. Furthermore, 'fast' responders, who responded immediately to plaque, exhibited significantly higher proteolytic activity throughout the experimental course than 'slow' responders, who showed a lagged inflammatory response.

CONCLUSION

The results indicate that differential inflammatory responses encompass inherent variations in total salivary proteolytic activities, which could be further utilised in contemporary diagnostic, prognostic and treatment modalities for periodontal diseases.

The clinical significance of serum chitinase 3-like 1 in hepatitis B-related chronic liver diseases

Aim

In the present study, we purposed to determine serum chitinase 3‐like 1 (CHI3L1) expression characteristics in chronic liver diseases monoinfected with hepatitis B virus and analyze its diagnostic value in liver fibrosis.

Methods

A total of 467 chronic hepatitis B (CHB) patients, 312 liver cirrhosis (LC) patients, and 104 hepatocellular carcinoma (HCC) patients at our institution were enrolled, and clinical indicators were analyzed.

Results

Our data have shown that the expression level of serum CHI3L1 was steadily increased from CHB to LC to HCC (P < .001). Serum CHI3L1 expression levels were positively associated with liver stiffness measurement (LSM), fibrosis‐4 (FIB‐4) index, aspartate aminotransferase‐to‐platelet ratio index (APRI), and HCC stage. The receiver operating characteristic (ROC) curve proved that serum CHI3L1 was superior to other noninvasive methods (LSM, FIB‐4, and APRI) with an area under the ROC curve (AUC) of 0.97 in diagnosing significant fibrosis.

Conclusions

Serum CHI3L1 harbors significant clinical value in chronic liver diseases infected with hepatitis B virus, especially in the diagnosis of fibrosis.

Chitinase 3-Like 1, Nestin, and Testin Proteins as Novel Biomarkers of Potential Clinical Use in Colorectal Cancer: A Review

Colorectal cancer is the third most commonly diagnosed cancer in males and the second most common in females. Only 10-20% of patients are diagnosed at the early stage of disease. Recently, the role of novel biomarkers of the neoplastic process in the early detection of colorectal cancer has been widely discussed. In this review, we focused on the three novel biomarkers that are of potential clinical importance in diagnosing and monitoring colorectal cancer. Chitinase 3-like 1 protein, also known as YKL-40, and nestin and testin proteins are produced by colorectal cancer cells. YKL-40 protein is a marker of proliferation, differentiation, and tissue morphogenetic changes. The level of YKL-40 is elevated in about 20% of patients with colorectal cancer. An increased expression of nestin indicates immaturity. It is a marker of angiogenesis in neoplastic processes. Testin protein is a component of cell-cell connections and focal adhesions. The protein is produced in normal human tissues, but not in tumor tissues. Downregulation of testin increases cell motility, spread, and proliferation, and decreases apoptosis. The usefulness and role of these biomarkers, both alone and combined, in the diagnostics of colorectal cancer should be further explored as early cancer detection may substantially improve treatment outcome and patient survival.

YKL-40/CHI3L1 facilitates migration and invasion in HER2 overexpressing breast epithelial progenitor cells and generates a niche for capillary-like network formation

Epithelial to mesenchymal transition (EMT) is a developmental event that is hijacked in some diseases such as fibrosis and cancer. In cancer, EMT has been linked to increased invasion and metastasis and is generally associated with a poor prognosis. In this study, we have compared phenotypic and functional differences between two isogenic cell lines with an EMT profile: D492M and D492HER2 that are both derived from D492, a breast epithelial cell line with stem cell properties. D492M is non-tumorigenic while D492HER2 is tumorigenic. Thus, the aim of this study was to analyze the expression profile of these cell lines, identify potential oncogenes, and evaluate their effects on cellular phenotype. We performed transcriptome and secretome analyses of D492M and D492HER2 and verified expression of selected genes at the RNA and protein level. One candidate, YKL-40 (also known as CHI3L1), was selected for further studies due to its differential expression between D492M and D492HER2, being considerably higher in D492HER2. YKL-40 has been linked to chronic inflammation diseases and cancer, yet its function is not fully understood. Knock-down experiments of YKL-40 in D492HER2 resulted in reduced migration and invasion as well as reduced ability to induce angiogenesis in an in vitro assay, plus changes in the EMT-phenotype. In summary, our data suggest that YKL-40 may provide D492HER2 with increased aggressiveness, supporting cancer progression and facilitating angiogenesis.

Chitinase-3-like-1 deficiency attenuates ethanol-induced liver injury by inhibition of sterol regulatory element binding protein 1-dependent triglyceride synthesis

OBJECTIVE

Alcohol overconsumption and abuse lead to alcoholic liver disease (ALD), which is a major chronic liver disease worldwide. Chitinase-3-like protein 1 (CHI3L1) have an important role in the pathogenesis of inflammatory disease. However, the role of CHI3L1 in ALD has not yet been reported. In the present study, we investigated the effect of CHI3L1 on chronic plus binge ethanol-induced liver injury.

METHODS

CHI3L1 knock out (KO) mice and their littermate control mice based on C57BL/6 (10-12 weeks old) were fed on a Lieber-DeCarli diet containing 6.6% ethanol for 10 days. And, CHI3L1 siRNA or CHI3L1 expressing vector was transfected HepG2 cells were treated with ethanol or without.

RESULTS

Ethanol-induced hepatic triglyceride (TG) levels and the mRNA levels of TG synthesis-related genes such as acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS) and stearoyl-CoA desaturase-1 (SCD1) were decreased in the liver of CHI3L1 knock out (KO) mice and the HepG2 cells transfected with CHI3L1 siRNA. Increased mRNA level and activation of SREBP1 which is transcription factor of ACC, FAS and SCD1 by ethanol feeding were reduced in the liver of ethanol-fed CHI3L1 KO mice. Moreover, ethanol-induced SREBP1 luciferase activity and mRNA level of SREBP1, ACC, FAS and SCD1 were also decreased in the HepG2 cells transfected with CHI3L1 siRNA, while those were further increased in the HepG2 cells treated with recombinant human CHI3L1. Furthermore, oxidative stress and up-regulated pro-inflammatory cytokines by ethanol were recovered in the liver of ethanol-fed CHI3L1 KO mice.

CONCLUSION

Our finding suggest that inhibition of CHI3L1 suppressed ethanol-induced liver injury through inhibition of TG synthesis, and the blocking of oxidative stress and hepatic inflammation induced SREBP1 activity could be significant.

Cerebrospinal fluid levels of glial marker YKL-40 strongly associated with axonal injury in HIV infection

BACKGROUND

HIV-1 infects the central nervous system (CNS) shortly after transmission. This leads to a chronic intrathecal immune activation. YKL-40, a biomarker that mainly reflects activation of astroglial cells, has not been thoroughly investigated in relation to HIV. The objective of our study was to characterize cerebrospinal fluid (CSF) YKL-40 in chronic HIV infection, with and without antiretroviral treatment (ART).

METHODS

YKL-40, neopterin, and the axonal marker neurofilament light protein (NFL) were analyzed with ELISA in archived CSF samples from 120 HIV-infected individuals (85 untreated neuroasymptomatic patients, 7 with HIV-associated dementia, and 28 on effective ART) and 39 HIV-negative controls.

RESULTS

CSF YKL-40 was significantly higher in patients with HIV-associated dementia compared to all other groups. It was also higher in untreated neuroasymptomatic individuals with CD4 cell count < 350 compared to controls. Significant correlations were found between CSF YKL-40 and age (r = 0.38, p < 0.001), CD4 (r = - 0.36, p < 0.001), plasma HIV RNA (r = 0.35, p < 0.001), CSF HIV RNA (r = 0.35, p < 0.001), CSF neopterin (r = 0.40, p < 0.001), albumin ratio (r = 0.44, p < 0.001), and CSF NFL (r = 0.71, p < 0.001). Age, CD4 cell count, albumin ratio, and CSF HIV RNA were found as independent predictors of CSF YKL-40 concentrations in multivariable analysis. In addition, CSF YKL-40 was revealed as a strong independent predictor of CSF NFL together with age, CSF neopterin, and CD4 cell count.

CONCLUSIONS

CSF YKL-40 is a promising biomarker candidate for understanding the pathogenesis of HIV in the CNS. The strong correlation between CSF YKL-40 and NFL suggests a pathogenic association between astroglial activation and axonal injury, and implies its utility in assessing the prognostic value of YKL-40.

YKL-40 expression in pterygium: a potential role in the pathogenesis

PURPOSE

The aim of the study was to evaluate whether YKL-40 (chitinase 3-like 1 protein) plays a role in pterygium pathogenesis.

METHODS

We included 42 primary pterygium patients and 24 control subjects with normal bulbar conjunctiva in the study. The pterygium patients were classified into the atrophic, fleshy, and intermediate groups according to the Tan classification. We then surgically removed the primary nasal pterygium and normal bulbar conjunctiva from the patients and immunohistochemically investigated YKL-40 expression.

RESULTS

YKL-40 expression was statistically significantly higher in the epithelial, endothelial, and stromal cells of the pterygium tissues than in the control tissues (P = 0.009, P = 0.003, P = 0.002, respectively). There was no significant correlation between the pterygium subgroups and YKL-40 expression (P > 0.05).

CONCLUSIONS

We believe YKL-40 may play a significant role in pterygium pathogenesis.

Influence of YKL-40 gene RNA interference on the biological behaviors of endometrial cancer HEC-1A cells

The present study aimed to investigate the effects of chitinase-3-like protein 1 (YKL-40) gene RNA interference on the biological behaviors and enhanced chemosensitivity of endometrial cancer (EC) HEC-1A cells. YKL-40 small interfering (si)RNA was transduced into EC HEC-1A cells using a lentivirus. The experiment was divided into three groups: The experimental group was transfected with YKL-40 siRNA (si-YKL-40); the mock-treatment group was transfected with transfection reagent only; and the blank control group was left untreated. A reverse transcription-quantitative polymerase chain reaction was performed to investigate the mRNA expression levels of YKL-40. The biological behaviors, including cell proliferation, migration, invasion and apoptosis, were detected by MTT and Transwell assays, and flow cytometry (FCM) analysis, respectively. The results of the present study demonstrated that the mRNA expression levels of YKL-40 were downregulated within HEC-1A cells upon transfection with si-YKL-40 (P<0.05). The proliferative, migratory and invasive abilities of HEC-1A cells were inhibited by si-YKL-40 (P<0.05). The mRNA expression levels of YKL-40 were upregulated within HEC-1A cells following treatment with cisplatin (P<0.05). FCM analysis revealed that the average cellular apoptosis rate increased following the inhibition of YKL-40 gene expression via siRNA (P<0.05). Therefore, the YKL-40 gene may be associated with the proliferative, migratory, invasive and anti-apoptotic ability of HEC-1A cells. YKL-40 downregulation may enhance the sensitivity of human EC HEC-1A cells to chemotherapy.

YKL-40 as a Potential Biomarker and a Possible Target in Therapeutic Strategies of Alzheimer's Disease

Background:

Growing body of evidence suggests that the pathogenesis of Alzheimer’s disease (AD), a progressing neurodegenerative condition, is not limited to the neuronal compartment, but also involves various immunological mechanisms. Insoluble Aβ aggregates in the brain can induce the activation of microglia, resulting in the synthesis of proinflammatory mediators, which further can stimulate astrocytic expression of YKL-40. Therefore, the aim of the current review is to present up-to-date data about the role of YKL-40 as a biomarker of AD as well as the possibility of therapeutic strategies targeting neuroinflammation.

Objective/Methods:

We searched PubMed articles for the terms “YKL-40”, “neurodegeneration”, “neuroinflammation” and “Alzheimer’s disease”, and included papers focusing on this review’s scope.

Results:

Recent studies indicate that CSF concentrations of YKL-40 were significantly higher in AD patients than in cognitively normal individuals and correlated with dementia biomarkers, such as tau proteins and amyloid beta. Determination of YKL-40 CSF concentration may be also helpful in differentiation between types of dementia and in the distinction of patients in the stable phase of MCI from those who progressed to dementia. Moreover, significantly increased levels of YKL-40 mRNA were found in AD brains in comparison with non-demented controls. Additionally, it was suggested that anti-inflammatory treatment might relief the symptoms of AD and slow its progression.

Conclusion:

Based on the recent knowledge, YKL-40 might be useful as a possible biomarker in the diagnosis and prognosis of AD. Modulation of risk factors and targeting of immune mechanisms, including systemic inflammation could lead to future preventive or therapeutic strategies for AD.

Serum YKL-40 as a biomarker for liver fibrosis in chronic hepatitis B patients with normal and mildly elevated ALT

Purpose

YKL-40 is a chitinase-like protein expressed in multiple tissues including liver and is reported as a fibrosis marker. This study aimed to determine whether YKL-40 could serve as a diagnostic marker for the assessment of liver fibrosis in chronic hepatitis B patients with normal and mildly elevated ALT.

Methods

Six hundred and eighty-five patients with chronic hepatitis B infection were enrolled in this study from October 2013 to March 2016. All patients underwent liver biopsy and then staged based on Ishak histological system. Serum YKL-40 levels were measured by Human Magnetic Luminex Assays.

Results

Among chronic hepatitis B patients with normal and mildly elevated ALT, almost more than 30% of patients have significant liver fibrosis. Serum YKL-40 levels increased significantly in parallel with the progression of fibrosis in patients with ALT less than two times the upper limit of normal range (P < 0.0001). Multivariate analysis revealed that serum YKL-40, hyaluronic acid, PLT, and AST were independently associated with significant fibrosis. We established a novel YKL-40-based fibrosis model for patients with ALT less than two times the upper limit of normal range (ULN). YKL-40 model was superior to APRI, FIB-4, Forns’ index, and Hui model for diagnosis of significant fibrosis in patients with ALT < 2ULN, with AUROCs of 0.786 [95% confidence interval (CI) 0.726–0.846] in the training group, 0.831 (95%CI 0.752–0.910) in the validation group and 0.801 (95%CI 0.753–0.849) in the entire cohort.

Conclusion

Serum YKL-40 is a feasible biomarker of liver fibrosis in chronic hepatitis B patients. YKL-40 model was superior to APRI, FIB-4, Forns’ index and Hui model for diagnosis of significant fibrosis in patients with normal and mildly elevated ALT.

Electronic supplementary material

The online version of this article (10.1007/s15010-018-1136-2) contains supplementary material, which is available to authorized users.

Immediate initiation of cART is associated with lower levels of cerebrospinal fluid YKL-40, a marker of microglial activation, in HIV-1 infection

OBJECTIVE

To characterize cerebrospinal fluid (CSF) YKL-40, a unique biomarker that reflects activation of microglial cells, in acute (AHI) and chronic HIV-1 infection (CHI) and to determine the effect of treatment initiation on levels of this marker.

DESIGN

A cross-sectional study of two groups of HIV-infected participants at baseline and follow-up timepoints.

METHODS

AHI (n = 33) and CHI (n = 34) participants underwent CSF and blood sampling before treatment initiation with combination antiretroviral therapy (cART) and at follow-up on cART in a subset of these individuals [6 months in AHI participants (n = 24), 1 year in CHI participants (n = 10)]. Measured parameters were analyzed at each timepoint. Analyses employed Mann-Whitney tests and Spearman correlations.

RESULTS

Baseline median YKL-40 was higher in CHI than AHI (96844 versus 80754 ng/l; P = 0.011). Elevations in the CHI group relative to the AHI group persisted at follow-up despite treatment (87414 versus 66130 ng/l; P = 0.003). In untreated CHI, YKL-40 correlated with neopterin (r = 0.51, P = 0.0025), chemokine (CXC-motif) ligand-10 (r = 0.44, P = 0.011), and neurofilament light chain (r = 0.56, P = 0.0008) in CSF.

CONCLUSIONS

This study is the first to describe the dynamics of CSF YKL-40 in two groups of HIV-infected individuals before and after cART and demonstrates the value of this marker in understanding HIV neuropathogenesis. The results suggest the utility of further exploring the prognostic value of YKL-40, particularly in individuals with early HIV infection or those initiating treatment during CHI.

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

YKL-40 regulated epithelial-mesenchymal transition and migration/invasion enhancement in non-small cell lung cancer

Background

YKL-40 is a secreted inflammatory protein that its overexpression has been reported to correlate with poor outcome of various malignant diseases, especially in cancer. However, the function of this protein is still unclear.

Methods

The clinical prognosis of non-small cell lung cancers (NSCLC) patients and their clinical YKL-40 expressions were obtained from the Prognoscan database. The expressions of YKL-40 in patient samples were determined by Western Blotting assay. YKL-40 gene knockdown and overexpression were performed on NSCLC cancer cells (CL1-1 and CL1-5). The cells were investigated for their epithelial–mesenchymal transition (EMT) markers gene modulation through Western Blotting and RT-PCR. Further cell metastatic abilities were assessed by transwell migration and invasion assay.

Result

In this study, YKL-40 was observed to be highly expressed in NSCLC specimens. Furthermore, determined by the PrognoScan database analysis, patients with high expression levels of YKL-40 were found with poor prognosis. In the in vitro study, different characteristics of NSCLC cell lines (CL1-1, H23, H838, CL1-5, and H2009) were used as study models, where YKL-40 expression levels were determined to correlate with the phenotypic characteristics of cancer metastasis. In this study,YKL-40 was demonstrated to regulate EMT marker expressions such as Twist, Snail, Slug, N-cadherin, Vimentin, and E-cadherin. The protein’s affects in cancer cell migration and invasion were also observed in YKL-40 overexpression or knock down NSCLC cell lines.

Conclusion

All of results from this study suggest that YKL-40 is a major factor in NSCLC metastasis. Thus, YKL-40 may serve as therapeutic targets for NSCLC patients in the future.

CILAIR-Based Secretome Analysis of Obese Visceral and Subcutaneous Adipose Tissues Reveals Distinctive ECM Remodeling and Inflammation Mediators

In the context of obesity, strong evidences support a distinctive pathological contribution of adipose tissue depending on its anatomical site of accumulation. Therefore, subcutaneous adipose tissue (SAT) has been lately considered metabolically benign compared to visceral fat (VAT), whose location is associated to the risk of developing cardiovascular disease, insulin resistance, and other associated comorbidities. Under the above situation, the chronic local inflammation that characterizes obese adipose tissue, has acquired a major role on the pathogenesis of obesity. In this work, we have analyzed for the first time human obese VAT and SAT secretomes using an improved quantitative proteomic approach for the study of tissue secretomes, Comparison of Isotope-Labeled Amino acid Incorporation Rates (CILAIR). The use of double isotope-labeling-CILAIR approach to analyze VAT and SAT secretomes allowed the identification of location-specific secreted proteins and its differential secretion. Additionally to the very high percentage of identified proteins previously implicated in obesity or in its comorbidities, this approach was revealed as a useful tool for the study of the obese adipose tissue microenvironment including extracellular matrix (ECM) remodeling and inflammatory status. The results herein presented reinforce the fact that VAT and SAT depots have distinct features and contribute differentially to metabolic disease.

RelB/p50 complexes regulate cytokine-induced YKL-40 expression

The secreted protein, YKL-40, has been proposed as a biomarker of a variety of human diseases characterized by ongoing inflammation, including chronic neurologic pathologies such as multiple sclerosis and Alzheimer's disease. However, inflammatory mediators and the molecular mechanism responsible for enhanced expression of YKL-40 remained elusive. Using several mouse models of inflammation, we now show that YKL-40 expression correlated with increased expression of both IL-1 and IL-6. Furthermore, IL-1 together with IL-6 or the IL-6 family cytokine, oncostatin M, synergistically upregulated YKL-40 expression in both primary human and mouse astrocytes in vitro. The robust cytokine-driven expression of YKL-40 in astrocytes required both STAT3 and NF-κB binding elements of the YKL-40 promoter. In addition, YKL-40 expression was enhanced by constitutively active STAT3 and inhibited by dominant-negative IκBα. Surprisingly, cytokine-driven expression of YKL-40 in astrocytes was independent of the p65 subunit of NF-κB and instead required subunits RelB and p50. Mechanistically, we show that IL-1-induced RelB/p50 complex formation was further promoted by oncostatin M and that these complexes directly bound to the YKL-40 promoter. Moreover, we found that expression of RelB was strongly upregulated during inflammation in vivo and by IL-1 in astrocytes in vitro. We propose that IL-1 and the IL-6 family of cytokines regulate YKL-40 expression during sterile inflammation via both STAT3 and RelB/p50 complexes. These results suggest that IL-1 may regulate the expression of specific anti-inflammatory genes in nonlymphoid tissues via the canonical activation of the RelB/p50 complexes.

Elevation in circulating YKL-40 concentration in patients with cerebrovascular disease

YKL-40 is a novel inflammatory protein. Elevated serum levels of YKL-40 have been reported in patients with atherosclerosis and other cardiovascular diseases, but the circulating profile of YKL-40 in patients with cerebrovascular disease has been less investigated. This prospective observational study aimed to determine serum levels of YKL-40 in patients with different subtypes and severities of cerebrovascular disease. Eighty patients with acute ischemic stroke, 30 patients with acute hemorrhagic stroke, 15 patients with transient ischemic attack (TIA) and 18 age- and gender-matched healthy control subjects were recruited. Blood was sampled. Serum levels of YKL-40 were measured by ELISA. In healthy control subjects, serum levels of YKL-40 were 45.09 ± 31.41 ng/ml, significantly lower than those in patients with acute ischemic stroke (178.58 ± 127.78 ng/ml), hemorrhagic stroke (105.32 ± 87.35 ng/ml) and TIA (148.09 ± 108 ng/ml) respectively (P<0.05). When the 80 acute ischemic stroke cases were stratified into four Oxfordshire Community Stroke subtypes, serum levels of YKL-40 were significantly higher in patients with total anterior (n=16), partial anterior (n=25) and posterior (n=12) circulation infarctions respectively than those with lacunar (n=27) infarction (P<0.05). Moreover, 63 of 80 patients with acute ischemic stroke survived. Circulating levels of YKL-40 in these stroke survivors were associated with the United States National Institutes of Health Stroke Scale (NIHSS) scores of neurological deficit. In summary, serum levels of YKL-40 were elevated in patients with cerebrovascular disease in lesion subtype- and severity-dependent manners. These observations suggest a potential for YKL-40 as a diagnostic/prognostic biomarker for cerebrovascular disease.

From bacteria to human: a journey into the world of chitinases

Chitinases, the enzymes responsible for the biological degradation of chitin, are found in a wide range of organisms from bacteria to higher plants and animals. They participate in numerous physiological processes such as nutrition, parasitism, morphogenesis and immunity. Many organisms, in addition to chitinases, produce inactive chitinase-like lectins that despite lacking enzymatic activity are involved in several regulatory functions. Most known chitinases belong to families 18 and 19 of glycosyl hydrolases, however a few chitinases that belong to families 23 and 48 have also been identified in recent years. In this review, different aspects of chitinases and chi-lectins from bacteria, fungi, insects, plants and mammals are discussed.

Chitinases in the salivary glands and circulation of patients with Sjögren's syndrome: macrophage harbingers of disease severity

OBJECTIVE

Sjögren's syndrome (SS) is a chronic autoimmune disease of unknown etiology that targets salivary and lacrimal glands and may be accompanied by multiorgan systemic manifestations. To further the understanding of immunopathology associated with SS and identify potential therapeutic targets, we undertook the present study comparing the gene expression profiles of salivary glands with severe inflammation versus those of salivary glands with mild or no disease.

METHODS

Using microarray profiling of salivary gland tissue from patients with SS and control subjects, we identified target genes, which were further characterized in tissue, serum, and cultured cell populations by real-time polymerase chain reaction and protein analysis.

RESULTS

Among the most highly expressed SS genes were those associated with myeloid cells, including members of the mammalian chitinase family, which had not previously been shown to be associated with exocrinopathies. Both chitinase 3-like protein 1 and chitinase 1, highly conserved chitinase-like glycoproteins (one with enzymatic activity and one lacking enzymatic activity), were evident at the transcriptome level and were detected within inflamed tissue. Chitinases were expressed during monocyte-to-macrophage differentiation and their levels augmented by stimulation with cytokines, including interferon-α (IFNα).

CONCLUSION

Because elevated expression of these and other macrophage-derived molecules corresponded with more severe SS, the present observations suggest that macrophages have potential immunopathologic involvement in SS and that the tissue macrophage transcription profile reflects multiple genes induced by IFNα.

Potential biomarkers of insulin resistance and atherosclerosis in type 2 diabetes mellitus patients with coronary artery disease

Type 2 diabetes mellitus patients with coronary artery disease have become a major public health concern. The occurrence of insulin resistance accompanied with endothelial dysfunction worsens the state of atherosclerosis in type 2 diabetes mellitus patients. The combination of insulin resistance and endothelial dysfunction leads to coronary artery disease and ischemic heart disease complications. A recognized biological marker, high-sensitivity C-reactive protein, has been used widely to assess the progression of atherosclerosis and inflammation. Along with coronary arterial damage and inflammatory processes, high-sensitivity C-reactive protein is considered as an essential atherosclerosis marker in patients with cardiovascular disease, but not as an insulin resistance marker in type 2 diabetes mellitus patients. A new biological marker that can act as a reliable indicator of both the exact state of insulin resistance and atherosclerosis is required to facilitate optimal health management of diabetic patients. Malfunctioning of insulin mechanism and endothelial dysfunction leads to innate immune activation and released several biological markers into circulation. This review examines potential biological markers, YKL-40, alpha-hydroxybutyrate, soluble CD36, leptin, resistin, interleukin-18, retinol binding protein-4, and chemerin, as they may play significant roles in insulin resistance and atherosclerosis in type 2 diabetes mellitus patients with coronary artery disease.

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.

Chronic obstructive pulmonary disease and lung cancer: common pathogenesis, shared clinical challenges

Environmental inhaled noxious particles have been known to play a role in several lung diseases, including chronic obstructive pulmonary disease (COPD) and lung cancer, the deadliest malignancy in the world in both sexes. Of the known noxious agents, tobacco smoking is the leading preventable cause of death worldwide and is a recognized risk for the development of both diseases. The association between COPD and lung cancer has been demonstrated in population-based studies, lung cancer screening programs, epidemiological surveys, and case control and biological mechanistic studies. There is evidence that cumulative smoking history is associated with the risk of developing lung cancer and COPD; however, the majority of smokers do not develop clinical COPD or lung cancer. This suggests the presence of one or several factors that modulate the responses to the offending agents and define the final risk for disease development. The 54th Aspen Lung Conference was convened to provide a forum for a systematic dissection of the potential mechanisms by which persons exposed to the causative agents are able to handle and control the process or, in the case of dysfunctional response, the mechanisms that take off in different directions and result in injury and disease. This summary reviews the themes presented and attempts to integrate them for those clinicians and researchers interested in these topics. The challenges and future directions emanating from the discussions may help frame future conferences and hopefully inspire the interest of young researchers.

Alpha-secretase inhibition reduces human glioblastoma stem cell growth in vitro and in vivo by inhibiting Notch

The Notch pathway is dysregulated and a potential target in glioblastoma multiforme (GBM). Currently available Notch inhibitors block γ-secretase, which is necessary for Notch processing. However, Notch is first cleaved by α-secretase outside the plasma membrane, via a disintegrin and metalloproteinase-10 and -17. In this work, we used a potent α-secretase inhibitor (ASI) to test inhibition of glioblastoma growth and inhibition of Notch and of both novel and known Notch targets. Featured in this study are luciferase reporter assays and immunoblot, microarray analysis, chromatin immunoprecipitation (ChIP), quantitative real-time PCR, cell number assay, bromodeoxyuridine incorporation, plasmid rescue, orthotopic xenograft model, and local delivery of treatment with convection-enhanced delivery using nanoparticles, as well as survival, MRI, and ex vivo luciferase assay. A CBF1-luciferase reporter assay as well as an immunoblot of endogenous Notch revealed Notch inhibition by the ASI. Microarray analysis, quantitative real-time PCR, and ChIP of ASI and γ-secretase inhibitor (GSI) treatment of GBM cells identified known Notch pathway targets, as well as novel Notch targets, including YKL-40 and leukemia inhibitory factor. Finally, we found that local nanoparticle delivery of ASIs but not GSIs increased survival time significantly in a GBM stem cell xenograft treatment model, and ASI treatment resulted in decreased tumor size and Notch activity. This work indicates α-secretase as an alternative to γ-secretase for inhibition of Notch in GBM and possibly other cancers as well, and it identifies novel Notch targets with biologic relevance and potential as biomarkers.

Transcriptional response to GAA deficiency (Pompe disease) in infantile-onset patients

Pompe disease is a genetic disorder resulting from a deficiency of lysosomal acid alpha-glucosidase (GAA) that manifests as a clinical spectrum with regard to symptom severity and rate of progression. In this study, we used microarrays to examine gene expression from the muscle of two cohorts of infantile-onset Pompe patients to identify transcriptional differences that may contribute to the disease phenotype. We found strong similarities among the gene expression profiles generated from biceps and quadriceps, and identified a number of signaling pathways altered in both cohorts. We also found that infantile-onset Pompe patient muscle had a gene expression pattern characteristic of immature or regenerating muscle, and exhibited many transcriptional markers of inflammation, despite having few overt signs of inflammatory infiltrate. Further, we identified genes exhibiting correlation between expression at baseline and response to therapy. This combined dataset can serve as a foundation for biological discovery and biomarker development to improve the treatment of Pompe disease.

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.

Relationship between sonographic parameters and YKL-40 levels in rheumatoid arthritis

YKL-40, also known as human cartilage glycoprotein 39, is a member of the "mammalian chitinase-like proteins" family without chitinase activity. Increased serum concentrations are associated with inflammatory processes and several types of cancer. In this study, we evaluated YKL-40 levels in serum and synovial fluid of patients with rheumatoid arthritis in comparison with the ultrasonographic findings. YKL-40 levels were measured by enzyme-linked immunosorbent assay in 25 patients with active rheumatoid arthritis and in 40 healthy subjects. B mode and power Doppler were performed to determine synovial thickening and vascularization. Serum YKL-40 level in patients was significantly higher than the concentration in healthy controls (P < 0.01). In patients with rheumatoid arthritis, the level of the glycoprotein in synovial fluid was remarkably elevated compared to the serum level (P = 0.003). The B mode and power Doppler scores correlated to YKL-40 in serum and synovial fluid (P = 0.07). Serum YKL-40 levels were related positively to serum markers of inflammation such as C-reactive protein (P = 0.004) and erythrocyte sedimentation rate (P = 0.003). This study is the first to demonstrate a relationship between YKL-40 levels and ultrasonographic examinations in Bulgarian patients with rheumatoid arthritis. The findings suggest that YKL-40 might be implicated in the pathogenesis of the disease and could indicate the level of joint inflammation.

[Identification in the rat olfactory epithelium new subgroup YM-1 chitinase-like protein]

Novel protein with a molecular mass of ~43 kDa from rat olfactory epithelium in pathophysiological conditions was discovered. Its amino acid sequence and affiliation with the family 18 glycohydrolase subgroup of chitinase-like proteins YM-1 were determined.

YKL-40 and mast cells are associated with detrusor fibrosis in patients diagnosed with bladder pain syndrome/interstitial cystitis according to the 2008 criteria of the European Society for the Study of Interstitial Cystitis

AIMS

Bladder pain syndrome/interstitial cystitis (BPS/IC), diagnosed according to the new 2008 criteria of the European Society for the Study of Interstitial Cystitis (ESSIC), may lead to detrusor fibrosis. In some inflammatory diseases, fibrosis is related to YKL-40. The aims were to examine YKL-40 antigenic expression in bladder tissue and levels in serum and urine in BPS/IC and to evaluate whether YKL-40 could be a non-invasive, prognostic biomarker for bladder fibrogenesis and treatment intensity.

METHODS AND RESULTS

Immunohistochemistry, immunoelectron microscopy and enzyme-linked immunosorbent assay (ELISA) analyses in 45 patients showed YKL-40 expression in detrusor mast cell granules and submucosal macrophages, and elevated YKL-40 levels in serum and urine compared to healthy individuals (median 72 versus 7 μg/l, P < 0.001). Clinicopathological parameters showed associations of detrusor fibrosis with YKL-40-positive cells (P = 0.001), mast cells (P = 0.014) and urine YKL-40 (P = 0.009). Bladder capacity correlated inversely with YKL-40-positive cells (P < 0.001) and mast cells (P = 0.029). Treatment intensity was not associated with YKL-40.

CONCLUSION

Serum and urine levels of YKL-40 may be used as non-invasive biomarkers in BPS/IC for the evaluation of bladder fibrogenesis.

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

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

Plasma YKL-40: a potential new cancer biomarker?

YKL-40, a 40-kDa secreted glycoprotein, with its gene located on chromosome 1q32.1, is produced by cancer cells and inflammatory cells and has a role in inflammation, cell proliferation, differentiation, protection against apoptosis, stimulation of angiogenesis and regulation of extracellular tissue remodeling. Plasma levels of YKL-40 are elevated in a subgroup of patients with primary or advanced cancer compared with age-matched healthy subjects, but also in patients with many different diseases characterized by inflammation. Elevated plasma YKL-40 levels are an independent prognostic biomarker of short survival. There is still insufficient evidence to support its value outside of clinical trials as a screening tool, prognosticator of survival, predictor of treatment response and as a monitoring tool in the routine management of individual patients with cancer or diseases characterized by inflammation. Large prospective, longitudinal clinical cancer studies are needed to determine if plasma YKL-40 is a new cancer biomarker, or is mainly a biomarker of inflammation.

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

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

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