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Chitinase 3-Like 1 (CHI3L1) Polymorphism Contributes to Visceral Obesity and Obesity-related Inflammation Induces Chi3l1 in Adipocytes
Biomed Sci Letters 2018;24:23-29
Published online March 31, 2018;
© 2018 The Korean Society For Biomedical Laboratory Sciences.

A Young Kim1, Hyun Woo Jeong1, Ji-Hae Lee1, Jin Kyu Choi2, Jeong Kee Kim3, Jae Sung Hwang3, and Dae-Bang Seo1,†

1Vital Beautie Research Division, Amorepacific R&D Center, Yongin 17074, Korea,
2QA team, Aestura Corporation, Ansung 17573, Korea,
3Department of Genetic Engineering & Graduate School of Biotechnology, College of Life Sciences, Kyung Hee University, Yongin 17104, Korea
Correspondence to: Dae-Bang Seo. Vital Beautie Research Division, Amorepacific R&D Center, Youngin 17074, Korea. Tel: +82-31-280-5975, Fax: +82-31-284-8392, e-mail:
Received November 29, 2017; Revised March 12, 2018; Accepted March 13, 2018.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abdominal obesity is considered as one of the most risky factors governing the development of metabolic diseases. Here we identify that human chitinase 3-like 1 (CHI3L1, also called YKL-40 in human) single nucleotide polymorphism (SNP), rs883125, is associated with abdominal obesity in Korean women. Korean women subjects with the rs883125 G/G or C/G genotype present higher waist-hip ratio than subjects with C/C genotype suggesting that human subjects who G nucleotide substitution at the rs883125 tended to more accumulate intra-abdominal fat at the abdominal cavity. In addition, Chi3l1 gene expression is increased in adipose tissue from obese mice and pro-inflammatory cytokine enhances Chi3l1 expression in adipocytes, indicating that Chi3l1 is greatly related with obesity and obesity-induced pro-inflammatory responses. Taken together, the minor allele of rs883125 is associated with a higher prevalence of abdominal obesity in Korean women. These findings suggest that genotype of rs883125 can be a biomarker of incident abdominal obesity and abdominal obesity-related metabolic diseases.

Keywords : Chitinase 3-like 1, CHI3L1, YKL-40, SNP, Abdominal obesity, Korean women

For the several decades, the prevalence and severity of obesity is dramatically and continuously has increased world-wide. Obesity has become a major public health problem since it is one of the key factors for development of metabolic diseases such as insulin resistance, type 2 diabetes, atherosclerosis, and several cancers. Although obesity is considered as a lifestyle disease, it is substantially recognized that genetic factors are also involved in the pathogenesis of obesity (Herrera and Lindgren, 2010; Choquet and Meyre, 2011). Single nucleotide polymorphisms (SNPs) is represented these genetic factors that contribute to development of obesity. Many researchers have found SNPs, which are associated with obesity, and identified those SNPs are located in genes that involved in food intake, fat metabolism, adipocyte differentiation, and energy metabolism (Dina et al., 2007; Frayling et al., 2007; Loos et al., 2008; Lindgren et al., 2009; Meyre et al., 2009).

Abdominal fat, also known as visceral fat, is located in peritoneal cavity around the organs. Accumulation of excess energy as abdominal fat in adipocytes leads abdominal obesity and is a very high risk factor for cardiovascular diseases and type 2 diabetes (Despres et al., 2008). Increase of fat storage in visceral adipocytes changes their characteristics and functions such as production of cytokines (McArdle et al., 2013). Enlarged adipocytes produce and secret pro-inflammatory cytokines and chemo-attractant molecules, including tumor necrosis factor-α (TNF-α), interleukin (IL)-1, IL-6, and monocyte chemotactic protein 1 (MCP1), in turn, induce a state of chronic low-grade inflammation with increase of infiltration of various immune cells into adipose tissue and lead alternation of whole body energy balance (Esser et al., 2014).

Chitinase 3-like 1 (CHI3L1, also called YKL-40 in human) is a chitinase-like glycoprotein, which binds to chitin but cannot degrade it because of mutations in their active domains (Rehli et al., 1997). CHI3L1 involves in tissue remodeling and immune responses through participating in M2 macrophage differentiation, inflammasome activation, and Th1/Th2 immune balance (Rehli et al., 2003). CHI3L1 is produced by various cells including macrophage and neutrophils (Krause et al., 1996; Volck et al., 1998). Additionally, circulating levels of CHI3L1 are increased in patients with inflammation-related diseases including asthma, atrophy, liver fibrosis, atherosclerosis, and type 2 diabetes (T2DM) (Chupp et al., 2007; Lee et al., 2012). Furthermore, CHI3L1 expression is induced by inflammatory cytokines such as IL-6, INF-γ, and TNFα (Ling and Recklies, 2004). In contrast, CHI3L1 inhibits cellular responses induced by those cytokines, implying that enhancement of CHI3L1 is one of the defense mechanisms to cytokine mediated-inflammation. Although several studies are reported that serum CHI3L1 levels are higher in obese subjects (Kyrgios et al., 2012; Huang et al., 2014; Huang et al., 2016), it is still not clear whether CHI3L1 is involved in obesity especially abdominal obesity. Therefore, in this study, we investigated the contribution of CHI3L1 to development of obesity in Korean women through analysis of CHI3L1 SNPs and found that rs883125 is associated with visceral obesity.


Study population

This study approved by Ethical Committee and the Institutional Review Board at Dermapro (IRB no. 1-220777-B-N-02-DICN14002), and all participants provided informed written consent before participation. A total of 106 healthy volunteers (Korean females, aged 20~60 years) were enrolled.

Biological parameters

BMI was calculated as weight (kg)/height2 (m2). Body fat contents (kg), body fat rate (%) were obtained by bioelectrical impedance analysis using InBody 3.0 (Biospace, Seoul, Korea).

SNP genotyping

The experimental determination of SNP genotypes were conducted by the Theragen Etex Co., Ltd. For genotyping analysis, DNA was extracted from peripheral blood leukocytes by using Exgene™ Blood SV (GeneAll, Seoul, Korea). 125 ng DNA was mixed with 2.5 μL of TaqMan OA GT Master Miz and used for the real-time quantitative PCR by TaqMan assay (Applied Biosystems, Calsbug, CA). The PCR mixture was loaded on the Open Array by using Accufill automated machine (Applied Biosystems, Calsbug, CA). The reaction ready Open Array chip was used in Quant Studio 12K (Applied Biosystems, Calsbug, CA). The real-time PCR reactions were performed at 95°C for 10 min, 40 cycles at 92°C for 15 sec, at 60°C for 1 sec. The genotyping was determined by the Vic and/or Fam fluorescent dye intensity.

Animal experiments

All animal procedures were approved by the Institutional Animal Care and Use Committee (IACUC) of Aestura Corporation and performed in accordance with their guidelines. 7-week-old C57BL/6J mice were purchased from the Central Laboratory Animal Inc. and maintained in a 12 h dark-12 h light cycle chamber with controlled temperature of 22~25°C and 40~50% humidity. For the HFD study, 8-week-old C57BL/6J male mice were fed a NCD or 60% HFD (Research Diet, Inc., D12492) for 16 weeks.

Cell culture

3T3-L1 cells were obtained from ATCC (CL-173). 3T3-L1 cells were grown to confluence in Dulbecco’s modified Eagle medium (DMEM; Hyclone, SH30243.01) supplemented with 10% bovine calf serum (Gibco, 26010-074). To induce adipocyte differentiation, at 2 days post-confluence, 3T3-L1 cells were incubated with DMEM containing 10% fetal bovine serum (FBS; Hyclone, SH30919.03), 0.52 mM 3-isobutyl-1-methylxanthine (Sigma Aldrich, I5879), 1 μM dexamethasone (Sigma Aldrich, D1756), and 1 μg/mL insulin (Roche, 11 376 497 001) for 2 days. Then, the culture medium was replaced with DMEM containing 10% FBS and 1 μg/mL insulin and the cells were cultured for 2 additional days. The culture medium was changed every two days with DMEM containing 10% FBS.

For the inflammatory environmental mimicking experiments, differentiated 3T3-L1 adipocytes were incubated with or without 10 ng/mL TNFα (R&D Systems, 210-TA) for 24 h.

RNA isolation and quantitative real-time PCR (qPCR)

The RNA isolation and cDNA synthesis procedure were performed as described previously. Briefly, total RNA was isolated from mouse cells or cell lines with TRIzol Reagent (Ambion, 15596-018) and subjected to cDNA synthesis using RevertAid™ First Strand cDNA Synthesis (Thermo Scientific). mRNA relative amounts were measured using the CFX96™ Real-Time System (Bio-Rad Laboratories Inc.) and calculated by normalization to the level of cyclophilin mRNA. The primer sequences that were used for quantitative real-time PCR analyses are provided in Supplementary Table 1.

Statistical analysis

The genetic association analysis used SPSS 15.0 and linear regression analysis.

In cell and mouse experiments, the results are presented as mean ± SEM. Statistical significance was assessed by the two-tailed Student’s t-test using GraphPad Prism 5.0 (GraphPad Software). When cells were used for experiments, three replicates per group were chosen. Differences were considered statistically significant at P < 0.05.


Baseline characteristics of this study are presented in Table 1.

Demographic characteristics of the study subjects

Age (y)44.51±6.22
Height (cm)158.36±5.21
Weight (kg)59.1±8.96
BMI (kg/m2)23.58±3.55
Fat mass (kg)19.87±6.28
Skeletal muscle mass (kg)21.2±2.43
Percent body fat (%)32.98±5.72
Waist-hip ratio0.9±0.04

CHI3L1 SNP rs883125 is associated with abdominal obesity in Korean Women

To identify polymorphisms in CHI3L1 that are associated with obesity, we analyzed the subjects using a dominant model. The SNP rs883125 is associated with obesity, especially abdominal obesity (Table 2), whereas other CHI3L1 SNPs, rs2275353 and rs10399805, had no relation with obesity (data not shown). We found that rs883125 G-allele was correlated with increased waist-hip ratio in Korean women, indicating that rs883125 contribute to visceral obesity.

Association of rs883125 of CHI3L1 and obesity-related quantitative traits among BMI, body fat contents, body fat rate and waist-hip ratio in collected Korean women

GenotypeDominant model

Age (years)45±644±643±844±6
BMI (kg/m2)23.1±3.124.2±3.925.0±5.724.3±
Body fat content (kg)19.0±5.420.9±7.323.8±7.421.1±
Body fat rate (%)32.2±5.234.0±6.534.5±3.634.0±6.31.721.130.13
Waist-hip ratio0.89±0.040.90±0.050.88±0.060.9±

Inflammatory cytokines promotes Chi3l1 expression in adipocytes

To determine whether CHI3L1 contributes in visceral obesity, we analyzed the mRNA levels of Chi3l1 in epididymal adipose tissue of diet-induced obese mice model. Consistent with previous reports (Ahangari et al., 2015), the transcripts of Chi3l1 were elevated in adipose tissue of high fat diet (HFD)-induced obese mice (Fig. 1A).

Fig. 1.

Chi3l1 is increased in adipose tissue of obese subjects and induced by inflammation in adipocytes. (A) C57BL/6J male mice were fed a NCD or 60% HFD for 16 weeks. Chi3l1 and Mcp-1 mRNA levels were measured by qPCR. (B) Differentiated 3T3-L1 adipocytes were incubated with or without TNFα (10 ng/mL) for 24 h. The mRNA levels of Chi3l1, Mcp-1, and adiponectin were measured by qPCR. All graphs show mean value ± SEM. **P < 0.01; ***P < 0.001 in two-tailed Student’s t-test.

To understand molecular mechanisms of obesity-mediated Chi3l1 enhancement, we evaluated which factors influence to induction of Chi3l1 in adipocytes. Several evidences indicate that the levels of CHI3L1 are enhanced in inflammatory environments (Recklies et al., 2005; Di Rosa and Malaguarnera, 2016). Notably, TNFα significantly increased the Chi3l1 gene expression in 3T3-L1 adipocytes suggesting that obesity-induced inflammatory responses could be a one of causing factor for enhancement of Chi3l1 in adipocytes (Fig. 1B).


Characteristics of fat tissues are completely different according to its location (Ibrahim, 2010). Among various fat tissues, abdominal adipose tissue is closely involved in development of metabolic diseases due to its spatial position, closed to other organs, and its own properties, more pro-inflammatory than subcutaneous fat (Lee et al., 2013). Consequently, it is important to control the intra-abdominal adiposity. In this study, we identify that CHI3L1 rs883125 G-allele associates with higher waist-hip ratio, indicating rs883125 could be a risk factor for abdominal obesity in Korean women.

Previous studies have approached that mouse CHI3L1 is involved in obesity, especially abdominal obesity (Ahangari et al., 2015). In visceral adipose tissue of high fat diet-induced obese mice, the mRNA levels of Chi3l1 are enhanced than visceral adipose tissue of normal chow diet-fed mice. In addition, Chi3l1 null mice have reduced visceral adipose tissue, which is composed with small adipocytes, compared with WT mice. On the other hand, Chi3l1 overexpressed mice have increased visceral fat pad. Furthermore, serum CHI3L1 levels have positive correlation with obesity, especially abdominal obesity in human (Thomsen et al., 2015). Therefore, these results support our finding, which is CHI3L1 contributes accumulation of fat in abdominal adipose tissue.

During weight gain, excess energy is accumulated in adipocytes as a fat resulting formation of enlarged adipocytes. Enlarged adipocytes secret various chemokines and cytokines to adapt the changed environment (Tilg and Moschen, 2006). Several immune cells are recruited into the visceral adipose tissue upon these signals from adipocytes and actively participate adipose tissue remodeling event (Sun et al., 2011). Even though the functions of CHI3L1 are not fully elucidated yet, it is known to have a closed relationship with inflammation and tissue remodeling via modulation of extracellular matrix (Kim et al., 2012; Di Rosa and Malaguarnera, 2016). Thus, obesity-induced enhancement of CHI3L1 might be involved in adipose tissue remodeling through regulation of inflammatory responses and adipocytes microenvironments.

A limitation of this study is the absence of serum CHI3L1 data. Therefore, it is difficult to conclude that rs883125 involved in abdominal obesity through regulating CHI3L1 levels. Accordingly, it is clearly of importance to clarify whether rs883125 influences the expression, synthesis, and circulating levels of CHI3L1.

Collectively, our study suggests rs883125, one of SNPs of CHI3L1, is significantly associated with abdominal obesity in Korean women. And these genetic variants could be a biomarker for development of abdominal obesity.




The authors have no conflicts of interest to disclose.

  1. Ahangari F, Sood A, Ma B, Takyar S, Schuyler M, Qualls C, Dela Cruz CS, Chupp GL, Lee CG, and Elias JA. Chitinase 3-like-1 regulates both visceral fat accumulation and asthma-like th2 inflammation. Am J Respir Crit Care Med 2015;191:746-757.
    Pubmed KoreaMed CrossRef
  2. Choquet H, and Meyre D. Genetics of obesity: What have we learned?. Curr Genomics 2011;12:169-179.
    Pubmed KoreaMed CrossRef
  3. Chupp GL, Lee CG, Jarjour N, Shim YM, Holm CT, He S, Dziura JD, Reed J, Coyle AJ, Kiener P, Cullen M, Grandsaigne M, Dombret MC, Aubier M, Pretolani M, and Elias JA. A chitinase-like protein in the lung and circulation of patients with severe asthma. N Engl J Med 2007;357:2016-2027.
    Pubmed CrossRef
  4. Despres JP, Lemieux I, Bergeron J, Pibarot P, Mathieu P, Larose E, Rodes-Cabau J, Bertrand OF, and Poirier P. Abdominal obesity and the metabolic syndrome: Contribution to global cardiometabolic risk. Arterioscler Thromb Vasc Biol 2008;28:1039-1049.
    Pubmed CrossRef
  5. Di Rosa M, and Malaguarnera L. Chitinase 3 like-1: An emerging molecule involved in diabetes and diabetic complications. Pathobiology 2016;83:228-242.
    Pubmed CrossRef
  6. Dina C, Meyre D, Gallina S, Durand E, Korner A, Jacobson P, Carlsson LM, Kiess W, Vatin V, Lecoeur C, Delplanque J, Vaillant E, Pattou F, Ruiz J, Weill J, Levy-Marchal C, Horber F, Potoczna N, Hercberg S, and Le Stunff C et al. Variation in fto contributes to childhood obesity and severe adult obesity. Nat Genet 2007;39:724-726.
    Pubmed CrossRef
  7. Esser N, Legrand-Poels S, Piette J, Scheen AJ, and Paquot N. Inflammation as a link between obesity, metabolic syndrome and type 2 diabetes. Diabetes Res Clin Pract 2014;105:141-150.
    Pubmed CrossRef
  8. Frayling TM, Timpson NJ, Weedon MN, Zeggini E, Freathy RM, Lindgren CM, Perry JR, Elliott KS, Lango H, Rayner NW, Shields B, Harries LW, Barrett JC, Ellard S, Groves CJ, Knight B, Patch AM, Ness AR, Ebrahim S, and Lawlor DA et al. A common variant in the fto gene is associated with body mass index and predisposes to childhood and adult obesity. Science 2007;316:889-894.
    Pubmed KoreaMed CrossRef
  9. Herrera BM, and Lindgren CM. The genetics of obesity. Curr Diab Rep 2010;10:498-505.
    Pubmed KoreaMed CrossRef
  10. Huang CJ, Beasley KN, Acevedo EO, Franco RL, Jones TL, Mari DC, and Shibata Y. Chitin enhances obese inflammation ex vivo. Hum Immunol 2014;75:41-46.
    Pubmed CrossRef
  11. Huang CJ, Slusher AL, Whitehurst M, Wells M, Maharaj A, and Shibata Y. The impact of acute aerobic exercise on chitinase 3-like protein 1 and intelectin-1 expression in obesity. Exp Biol Med (Maywood) 2016;241:216-221.
    Pubmed KoreaMed CrossRef
  12. Ibrahim MM. Subcutaneous and visceral adipose tissue: Structural and functional differences. Obes Rev 2010;11:11-18.
    Pubmed CrossRef
  13. Kim MN, Lee KE, Hong JY, Heo WI, Kim KW, Kim KE, and Sohn MH. Involvement of the mapk and pi3k pathways in chitinase 3-like 1-regulated hyperoxia-induced airway epithelial cell death. Biochem Biophys Res Commun 2012;421:790-796.
    Pubmed CrossRef
  14. Krause SW, Rehli M, Kreutz M, Schwarzfischer L, Paulauskis JD, and Andreesen R. Differential screening identifies genetic markers of monocyte to macrophage maturation. J Leukoc Biol 1996;60:540-545.
    Pubmed CrossRef
  15. Kyrgios I, Galli-Tsinopoulou A, Stylianou C, Papakonstantinou E, Arvanitidou M, and Haidich AB. 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. Metabolism 2012;61:562-568.
    Pubmed CrossRef
  16. Lee JH, Kim SS, Kim IJ, Song SH, Kim YK, In Kim J, Jeon YK, Kim BH, and Kwak IS. Clinical implication of plasma and urine ykl-40, as a proinflammatory biomarker, on early stage of nephropathy in type 2 diabetic patients. J Diabetes Complications 2012;26:308-312.
    Pubmed CrossRef
  17. Lee MJ, Wu Y, and Fried SK. Adipose tissue heterogeneity: Implication of depot differences in adipose tissue for obesity complications. Mol Aspects Med 2013;34:1-11.
    Pubmed KoreaMed CrossRef
  18. Lindgren CM, Heid IMR, andall JC, Lamina C, Steinthorsdottir V, Qi L, Speliotes EK, Thorleifsson G, Willer CJ, Herrera BM, Jackson AU, Lim N, Scheet P, Soranzo N, Amin N, Aulchenko YS, Chambers JC, Drong A, Luan J, and Lyon HN et al. Genome-wide association scan meta-analysis identifies three loci influencing adiposity and fat distribution. PLoS Genet 2009;5:e1000508.
    Pubmed KoreaMed CrossRef
  19. Ling H, and Recklies AD. The chitinase 3-like protein human cartilage glycoprotein 39 inhibits cellular responses to the inflammatory cytokines interleukin-1 and tumour necrosis factor-alpha. Biochem J 2004;380:651-659.
    Pubmed KoreaMed CrossRef
  20. Loos RJ, Lindgren CM, Li S, Wheeler E, Zhao JH, Prokopenko I, Inouye M, Freathy RM, Attwood AP, Beckmann JS, Berndt SI, Prostate LC, Ovarian Cancer Screening T, Jacobs KB, Chanock SJ, Hayes RB, Bergmann S, Bennett AJ, Bingham SA, and Bochud M et al. Common variants near mc4r are associated with fat mass, weight and risk of obesity. Nat Genet 2008;40:768-775.
    Pubmed KoreaMed CrossRef
  21. McArdle MA, Finucane OM, Connaughton RM, McMorrow AM, and Roche HM. Mechanisms of obesity-induced inflammation and insulin resistance: Insights into the emerging role of nutrional strategies. Front Endocrinol (Lausanne) 2013;4:52.
    Pubmed KoreaMed CrossRef
  22. Meyre D, Delplanque J, Chevre JC, Lecoeur C, Lobbens S, Gallina S, Durand E, Vatin V, Degraeve F, Proenca C, Gaget S, Korner A, Kovacs P, Kiess W, Tichet J, Marre M, Hartikainen AL, Horber F, Potoczna N, and Hercberg S et al. Genome-wide association study for early-onset and morbid adult obesity identifies three new risk loci in european populations. Nat Genet 2009;41:157-159.
    Pubmed CrossRef
  23. Recklies AD, Ling H, White C, and Bernier SM. Inflammatory cytokines induce production of chi3l1 by articular chondrocytes. J Biol Chem 2005;280:41213-41221.
    Pubmed CrossRef
  24. Rehli M, Krause SW, and Andreesen R. Molecular characterization of the gene for human cartilage gp-39 (chi3l1), a member of the chitinase protein family and marker for late stages of macrophage differentiation. Genomics 1997;43:221-225.
    Pubmed CrossRef
  25. Rehli M, Niller HH, Ammon C, Langmann S, Schwarzfischer L, Andreesen R, and Krause SW. Transcriptional regulation of chi3l1, a marker gene for late stages of macrophage differentiation. J Biol Chem 2003;278:44058-44067.
    Pubmed CrossRef
  26. Sun K, Kusminski CM, and Scherer PE. Adipose tissue remodeling and obesity. J Clin Invest 2011;121:2094-2101.
    Pubmed KoreaMed CrossRef
  27. Thomsen SB, Gjesing AP, Rathcke CN, Ekstrom CT, Eiberg H, Hansen T, Pedersen O, and Vestergaard H. Associations of the inflammatory marker ykl-40 with measures of obesity and dyslipidaemia in individuals at high risk of type 2 diabetes. PLoS One 2015;10:e0133672.
    Pubmed KoreaMed CrossRef
  28. Tilg H, and Moschen AR. Adipocytokines: Mediators linking adipose tissue, inflammation and immunity. Nat Rev Immunol 2006;6:772-783.
    Pubmed CrossRef
  29. Volck B, Price PA, Johansen JS, Sorensen O, Benfield TL, Nielsen HJ, Calafat J, and Borregaard N. Ykl-40, a mammalian member of the chitinase family, is a matrix protein of specific granules in human neutrophils. Proc Assoc Am Physicians 1998;110:351-360.