Adiponectin upregulates hepatocyte CMKLR1 which is reduced in human fatty liver

https://doi.org/10.1016/j.mce.2011.10.032Get rights and content

Abstract

Chemokine-like receptor 1 (CMKLR1) ligands chemerin and resolvin E1 are suggested to have a role in non-alcoholic fatty liver disease (NAFLD). Here, expression of CMKLR1 in liver cells and NAFLD was studied. CMKLR1 was detected in primary human hepatocytes (PHH), Kupffer cells, bile-duct cells and hepatic stellate cells. In human and rodent fatty liver and in fibrotic liver of mice fed a methionine–choline deficient diet CMKLR1 was reduced. Hepatocytes are the major cells in the liver and effects of adipokines, cytokines and lipids on CMKLR1 in PHH were analyzed. Increased cellular triglyceride or cholesterol content, lipopolysaccharide, IL-6, TNF and leptin did not influence CMKLR1 levels in PHH whereas profibrotic TGFβ tended to reduce CMKLR1. Adiponectin strongly upregulated CMKLR1 mRNA and protein in PHH and hepatic CMKLR1 when injected into wild type mice. Further, CMKLR1 was suppressed in the liver of adiponectin deficient mice. These data indicate that low CMKLR1 in NAFLD may partly result from reduced adiponectin activity.

Highlights

► Chemokine-like receptor 1 (CMKLR1) is the receptor for the adipokine chemerin. ► CMKLR1 is expressed by hepatocytes. ► CMKLR1 is reduced in fatty liver and in rodent fibrotic liver. ► Adiponectin induces CMKLR1 in hepatocytes. ► CMKLR1 is reduced in liver of adiponectin-deficient mice.

Introduction

Non-alcoholic fatty liver disease is becoming the most common cause of chronic liver diseases in westernized countries (Clark, 2006). Obesity is frequently accompanied by NAFLD and altered metabolic function and increased production of inflammatory adipokines are suggested to contribute to hepatic steatosis and progressive liver disease (Clark, 2006, Schaffler et al., 2005). IL-6 is preferentially released from visceral fat and upregulates suppressor of cytokine signaling 3 in the liver which causes hepatic insulin resistance (Fontana et al., 2007, Sabio et al., 2008, Wiest et al., 2011). Leptin is mainly produced by subcutaneous adipocytes, and obesity is characterized by elevated systemic levels. Leptin prevents lipid accumulation in the liver, and animal studies proved that leptin directly promotes fibrogenesis (Biddinger et al., 2006, Wang et al., 2009a). Systemic adiponectin which lowers hepatocyte lipid storage and protects from progressive liver damage is reduced in obesity and patients with fatty liver disease independent of body mass index (Polyzos et al., 2010, Schaffler et al., 2005, Wang et al., 2009b). Antiinflammatory effects of adiponectin include inhibition of TNF activity, a cytokine involved in the pathophysiology of metabolic liver injury (Tilg, 2010).

Chemokine-like receptor 1 (CMKLR1) is expressed by immune cells and is downregulated by TNF and LPS in macrophages (Zabel et al., 2006). TGFβ which deactivates macrophages induces CMKLR1 (Zabel et al., 2006). Mice with deficiency of CMKLR1 exhibit increased recruitment of inflammatory cells in the lung upon LPS challenge indicating antiinflammatory effects of CMKLR1 (Luangsay et al., 2009).

Chemerin is one of the ligands of CMKLR1 and circulating levels are increased in obesity (Meder et al., 2003, Weigert et al., 2010). Serum chemerin positively correlates with BMI, Homeostasis Model Assessment of Insulin Resistance, triglycerides, systolic blood pressure, leptin, resistin, C-reactive protein, TNF and IL-6 and negatively with HDL cholesterol suggesting a function of chemerin in metabolic disturbances associated with obesity (Bozaoglu et al., 2007, Ernst et al., 2010, Parlee et al., 2010, Stejskal et al., 2008, Weigert et al., 2010). In morbidly obese patients with non-alcoholic steatohepatitis (NASH) chemerin is further elevated (Sell et al., 2010). Chemerin is an attractant for immune cells and pro- and antiinflammatory effects of chemerin have been described (Ernst and Sinal, 2010). More recently it has been shown that chemerin impairs insulin signaling in adipocytes and skeletal muscle cells (Becker et al., 2010, Kralisch et al., 2009, Sell et al., 2009).

CMKLR1 also serves as a receptor for resolvin E1 which is derived from omega 3 polyunsaturated fatty acids at inflammatory sites (Arita et al., 2007). Resolvin E1 mediates insulin-sensitizing and antisteatotic effects in rodent models of obesity (Arita et al., 2007, Gonzalez-Periz et al., 2009).

CMKLR1 is expressed in the liver (Ernst et al., 2010, Parlee et al., 2010) and so far it has been shown that mRNA levels are not altered in the liver of ob/ob mice compared to wild type animals. It was hypothesized that CMKLR1 is also expressed by hepatocytes and that its level may be altered in NAFLD. Therefore, we intended to more closely analyse the expression of CMKLR1 in human liver cell populations, human and rodent fatty liver and rodent NASH.

Section snippets

Material

Dulbecco’s modified eagle medium (DMEM) was from PAA (Karlsruhe, Germany), RNeasy Mini Kit was from Qiagen (Hilden, Germany) and oligonucleotides were synthesized by Metabion (Planegg-Martinsried, Germany). LightCycler FastStart DNA Master SYBR Green I was purchased from Roche (Mannheim, Germany). The ACAT inhibitor Sandoz 58-035, LPS (Escherichia coli serotype 055:B5), palmitic acid and oleic acid were ordered from Sigma (Deisenhofen, Germany). Acetylated LDL was from Invitrogen GmbH

CMKLR1 expression in primary human liver cells

CMKLR1 mRNA was detected in primary human hepatocytes (PHH), hepatic stellate cells (HSC), endothelial cells, Kupffer cells (KC) and bile duct cells (Fig. 1A). CMKLR1 protein was analyzed in PHH, KC and HSC and was expressed by all of these cells. Although identical concentrations of the different protein lysates were used GAPDH protein was higher abundant in HSC, KC and macrophages compared to PHH (Fig. 1B). To confirm similar amounts of protein in the different lysates Coomassie stained

Discussion

In the current study we show that CMKLR1 protein is expressed by hepatocytes, hepatic stellate cells, bile duct epithelial cells and Kupffer cells. All of these cells express CMKLR1 mRNA but it has to be considered that primary cells are contaminated with other liver cells to some degree and this may give false positive results. To solve this problem in situ hybridisation to detect cellular mRNAs has to be performed. CMKLR1 protein is highly expressed in hepatoma cell lines suggesting that

Disclosure

The authors declare that they have no conflicts of interest related to this work.

Acknowledgments

The technical assistance of Yvonne Hader is greatly appreciated. The study was supported by a Grant from the Deutsche Forschungsgemeinschaft (BU 1141/3-3, BU 1141/7-1) to C. Buechler and a grant from the Regensburger Forschungsförderung (ReForm C) to C. Buechler, C. Hellerbrand and T.S. Weiss.

References (57)

  • F. Schober et al.

    Low molecular weight adiponectin negatively correlates with the waist circumference and monocytic IL-6 release

    Biochem. Biophys. Res. Commun.

    (2007)
  • H. Seki et al.

    Omega-3 PUFA derived anti-inflammatory lipid mediator resolvin E1

    Prostaglandins Other Lipid Mediat.

    (2009)
  • H. Steiling et al.

    Activated hepatic stellate cells express keratinocyte growth factor in chronic liver disease

    Am. J. Pathol.

    (2004)
  • J. Wanninger et al.

    Lipid accumulation impairs adiponectin-mediated induction of activin A by increasing TGFbeta in primary human hepatocytes

    Biochim. Biophys. Acta

    (2011)
  • J. Wanninger et al.

    MMP-9 activity is increased by adiponectin in primary human hepatocytes but even negatively correlates with serum adiponectin in a rodent model of non-alcoholic steatohepatitis

    Exp. Mol. Pathol.

    (2011)
  • T.S. Weiss et al.

    Cellular damage to human hepatocytes through repeated application of 5-aminolevulinic acid

    J. Hepatol.

    (2003)
  • R. Wiest et al.

    Impaired hepatic removal of interleukin-6 in patients with liver cirrhosis

    Cytokine

    (2011)
  • B.A. Zabel et al.

    Chemokine-like receptor 1 expression by macrophages in vivo: regulation by TGF-beta and TLR ligands

    Exp. Hematol.

    (2006)
  • M. Arita et al.

    Resolvin E1 selectively interacts with leukotriene B4 receptor BLT1 and ChemR23 to regulate inflammation

    J. Immunol.

    (2007)
  • T. Asano et al.

    Adiponectin knockout mice on high fat diet develop fibrosing steatohepatitis

    J. Gastroenterol. Hepatol.

    (2009)
  • S. Bauer et al.

    Sterol regulatory element-binding protein 2 (SREBP2) activation after excess triglyceride storage induces chemerin in hypertrophic adipocytes

    Endocrinology

    (2011)
  • M. Becker et al.

    Expression of human chemerin induces insulin resistance in the skeletal muscle but does not affect weight, lipid levels, and atherosclerosis in LDL receptor knockout mice on high-fat diet

    Diabetes

    (2010)
  • V. Berg et al.

    Human articular chondrocytes express ChemR23 and chemerin; ChemR23 promotes inflammatory signalling upon binding the ligand chemerin(21–157)

    Arthritis Res. Ther.

    (2010)
  • S.B. Biddinger et al.

    Leptin suppresses stearoyl-CoA desaturase 1 by mechanisms independent of insulin and sterol regulatory element-binding protein-1c

    Diabetes

    (2006)
  • K. Bozaoglu et al.

    Chemerin is a novel adipokine associated with obesity and metabolic syndrome

    Endocrinology

    (2007)
  • K. Bozaoglu et al.

    Chemerin, a novel adipokine in the regulation of angiogenesis

    J. Clin. Endocrinol. Metab.

    (2010)
  • J.L. Cash et al.

    Synthetic chemerin-derived peptides suppress inflammation through ChemR23

    J. Exp. Med.

    (2008)
  • J.M. Clark

    The epidemiology of nonalcoholic fatty liver disease in adults

    J. Clin. Gastroenterol.

    (2006)
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