Elsevier

Metabolism

Volume 63, Issue 4, April 2014, Pages 542-553
Metabolism

Clinical Science
Accumulation of adiponectin in inflamed adipose tissues of obese mice

https://doi.org/10.1016/j.metabol.2013.12.012Get rights and content

Abstract

Objective

Adipose tissue inflammation plays an important role in the pathogenesis of obesity-associated complications, such as atherosclerosis. Adiponectin secreted from adipocytes has various beneficial effects including anti-inflammatory effect. Obesity often presents with hypoadiponectinemia. However, the mechanism and adiponectin movement in obesity remain uncharacterized. Here we investigated tissue distribution of adiponectin protein in lean and obese mice.

Methods

Adiponectin protein levels were evaluated by enzyme-linked immunosorbent assay and western blotting. Adipose tissues were fractionated into mature adipocyte fraction (MAF) and stromal vascular fraction (SVF).

Results

Adiponectin protein was detected not only in MAF but also in SVF, which lacks adiponectin mRNA expression, of adipose tissue remarkably. SVF adiponectin protein level was higher in obese mice than in lean mice. The mechanism of adiponectin accumulation was investigated in adiponectin-deficient (APN-KO) mice after injection of plasma from wild-type mice. These mice showed accumulation of exogenous adiponectin, which derived from wild type mice, in adipose tissues, and the adiponectin was more observed in SVF of diet induced obese APN-KO mice than lean APN-KO mice. Among the adiponectin binding proteins, T-cadherin mRNA and protein levels in SVF of obese mice were remarkably higher than in lean mice. Oxidative stress levels were also significantly higher in SVF of obese mice than lean mice. Mechanistically, H2O2 up-regulated T-cadherin mRNA level in murine macrophages.

Conclusions

The results demonstrated adiponectin targets to adipose SVF of obese mice. These findings should shed a new light on the pathology of adipose tissue inflammation and hypoadiponectinemia of obesity.

Introduction

Visceral obesity associated with multiple cardiometabolic risk factors is a common basis of atherosclerotic vascular diseases. Obesity correlates with chronic inflammation of the adipose tissues, which is characterized by progressive infiltration of macrophages [1] and overproduction of reactive oxygen species (ROS) [2], [3]. The chronic inflammation state results in adipocyte dysfunction and dysregulated production of adipocytokines, leading to systemic metabolic disorders and atherosclerosis [4], [5]. The inflamed adipose tissue in obesity is also characterized histopathologically by the presence of "crown-like structures", representing macrophages around dead adipocytes [6], [7].

The normal blood level of adiponectin [also known as adipocyte complement-related protein of 30 kDa (ACRP30), adipoQ and gelatin binding protein of 28 kDa (GBP28)], an adipocytokine discovered by our laboratory and three other groups, independently [8], [9], [10], [11], [12], ranges from 3 to 30 μg/mL, but decreases in obese individuals [13]. However, the mechanism of plasma adiponectin reduction in obesity has not been fully elucidated. Adiponectin is exclusively synthesized by adipocytes and exhibits anti-diabetic, anti-atherosclerotic, and anti-inflammatory properties [14]. These actions are supposed to be mediated through the interaction of adiponectin with cell surface binding receptors. The first identified adiponectin receptor, AdipoR1, was isolated from a human skeletal muscle cDNA library while screening for globular adiponectin binding [15]. AdipoR2 was found based on its homology with AdipoR1. Both AdipoR1 and AdipoR2 are surface membrane proteins with seven transmembrane domains, with similar molecular structures, and are expressed in the liver, muscle, and adipose tissue in humans. Adiponectin also binds to calreticulin on the macrophage cell surface, and opsonizes apoptotic cells [16]. T-cadherin, a GPI-anchored molecule that lacks a cytoplasmic region, also binds with adiponectin on vascular endothelial cells and smooth muscle [17], [18].

Studies from our laboratories have demonstrated the severer tissue damage in the heart and kidney of adiponectin-deficient (APN-KO) mice compared to wild type mice, by various pathological overload. Administration of adenovirus-induced adiponectin ameliorates such tissue injury and also suppressed progression of fatty streak lesion in apoE KO mice [19], [20], [21]. The anti-proinflammatory property of adiponectin [14] might be mediated partly through the release of IL-10 by macrophages [22]. Adiponectin also promotes macrophage polarization toward the M2 phenotype and reduces ROS generation [23]. Here, in this study, we postulate adiponectin may stay or return to interstitial space of adipose tissue adipose tissue, and may play a role in the control of adipose tissue inflammation in obesity. The present study was designed to localize adiponectin in adipose tissues of obese and lean mice, and the mechanisms involved in such distribution pattern.

Section snippets

Materials

Rabbit polyclonal antibody to mouse adiponectin was generated at Otsuka Pharmaceutical (Tokyo, Japan). Monoclonal antibodies to mouse F4/80 (Abcam, Cambridge, MA) and T-cadherin (Santa Cruz Biotechnology, Santa Cruz, CA) were purchased. Goat anti-rabbit IgG horseradish peroxidase (HRP) conjugate and Goat anti-rat IgG HRP conjugate were purchased from GE Healthcare (Uppsala, Sweden).

Animal models

Male BKS.Cg-+LeprDB/+ Leprdb/J (db/db) mice and their respective lean control male BKS.Cg-m +/m +/J (+ m/+ m) mice were

Adiponectin protein in lean and obese mice

Body weight, tissue weight of WATsub and WATmes were significantly higher and plasma adiponectin concentrations were significantly lower in obese db/db mice than lean control + m/+ m mice (body weight: db/db; 45.2 ± 1.6 g, + m/+ m; 24.4 ± 1.2 g, p < 0.0001, WATsub: db/db; 3.7 ± 0.5 g, + m/+ m; 0.4 ± 0.1 g, p < 0.0001, WATmes: db/db; 1.6 ± 0.2 g, + m/+ m; 0.3 ± 0.1 g, p < 0.0001, plasma adiponectin: db/db; 14.2 ± 2.2 μg/mL, + m/+ m; 19.0 ± 2.1 μg/mL, p < 0.0001). Next, we examined the tissue distribution of adiponectin protein in lean

Discussion

The major findings of the present study were 1) adiponectin protein existed in SVF, which lacks adiponectin mRNA expression, as well as MAF of WATsub and WATmes, 2) adiponectin protein levels were significantly higher in SVFsub and SVFmes of obese mice than in lean mice, 3) using fluorescent immunostaining, adiponectin protein was observed not only in adipocytes, but also in interstitium of WATsub and WATmes. The present study also demonstrated that 1) by a single injection of WT-plasma

Author contributions

HN and KK researched and analyzed the data, participated in the concept and design of the study. KK also participated in interpretation of data and reviewed/edited the manuscript. RS analyzed the data. NK and SK contributed to the discussion. TF and IS contributed to the discussion and wrote the manuscript. All authors read and approved the final version of the manuscript.

Funding

This research was supported in part by a Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area) "Molecular Basis and Disorders of Control of Appetite and Fat Accumulation" (#22126008, to TF and KK).

Conflict of interest

TF is a member of the “Department of Metabolism and Atherosclerosis”, a sponsored course endowed by Kowa Co. Ltd. The company has a scientific officer who oversees the program. All other authors declare no competing interests.

Acknowledgments

We thank Dr. Yoshihiro Tochino, Mrs. Miyuki Nakamura, Mr. Yugo Miyata and Takuya Mori (members of our laboratory) for the excellent technical assistance.

References (46)

  • P. Mandal et al.

    Molecular mechanism for adiponectin-dependent M2 macrophage polarization: link between the metabolic and innate immune activity of full-length adiponectin

    J Biol Chem

    (2011)
  • Y. Hattori et al.

    High molecular weight adiponectin activates AMPK and suppresses cytokine-induced NF-kappaB activation in vascular endothelial cells

    FEBS Lett

    (2008)
  • K. Kishida et al.

    Disturbed secretion of mutant adiponectin associated with the metabolic syndrome

    Biochem Biophys Res Commun

    (2003)
  • S.H. Jee et al.

    Adiponectin concentrations: a genome-wide association study

    Am J Hum Genet

    (2010)
  • S.P. Weisberg et al.

    Obesity is associated with macrophage accumulation in adipose tissue

    J Clin Invest

    (2003)
  • S. Furukawa et al.

    Increased oxidative stress in obesity and its impact on metabolic syndrome

    J Clin Invest

    (2004)
  • Y. Okauchi et al.

    Cross-sectional and longitudinal study of association between circulating thiobarbituric acid-reacting substance levels and clinicobiochemical parameters in 1,178 middle-aged Japanese men — the Amagasaki Visceral Fat Study

    Nutr Metab (Lond)

    (2011)
  • Y. Matsuzawa

    Therapy insight: adipocytokines in metabolic syndrome and related cardiovascular disease

    Nat Clin Pract Cardiovasc Med

    (2006)
  • J.P. Després et al.

    Abdominal obesity and metabolic syndrome

    Nature

    (2006)
  • Y. Nakano et al.

    Isolation and characterization of GBP28, a novel gelatin-binding protein purified from human plasma

    J Biochem

    (1996)
  • N. Ouchi et al.

    Adipokines in inflammation and metabolic disease

    Nat Rev Immunol

    (2011)
  • T. Yamauchi et al.

    Cloning of adiponectin receptors that mediate antidiabetic metabolic effects

    Nature

    (2003)
  • Y. Takemura et al.

    Adiponectin modulates inflammatory reactions via calreticulin receptor-dependent clearance of early apoptotic bodies

    J Clin Invest

    (2007)
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