ABSTRACT
To determine adipocytokines that play a regulatory role during obesity development, we explored the genes that encode growth factors and investigated the physiological functions for adipose tissue development. Here, we isolated amphiregulin (Areg) gene whose expression was significantly up-regulated in obese adipose tissues. Areg mRNA level was positively correlated with macrophage marker gene expression in adipose tissues in vivo. Unexpectedly, Areg transgenic mice showed less adipose tissue mass with increased mRNA expression levels of Tnf-α and peroxisome proliferator-activated receptor γ coactivator 1α (Pgc-1α) and delayed white adipose tissue development during the convalescent stage in a dextran sodium sulfate-induced colitis model. This study showed that Areg mRNA expression was significantly up-regulated in obese adipose tissues and over-expression of Areg in white adipose tissue caused less adipose tissue mass.
Subject(s)
Adipose Tissue, White/pathology , Amphiregulin/metabolism , Colitis/pathology , Disease Models, Animal , Obesity/physiopathology , Adipose Tissue, White/metabolism , Amphiregulin/genetics , Animals , Colitis/chemically induced , Colitis/metabolism , Dextran Sulfate/toxicity , Female , Gene Expression Profiling , Male , Mice , Mice, Inbred C57BL , Mice, Transgenic , Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha/genetics , Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha/metabolism , Tumor Necrosis Factor-alpha/genetics , Tumor Necrosis Factor-alpha/metabolismABSTRACT
Macrophage infiltration in the adipose tissue, and the interaction with adipocytes, is well documented to be involved in fat inflammation and obesity-associated complications. In this study, we isolated IκB kinase ε (IKKε) as a key adipocyte factor that is potentially affected by interaction with macrophages in adipose tissue in vivo. We showed that IKKε mRNA expression levels in white adipose tissue were increased in both genetic and diet-induced obese mouse. Furthermore, IKKε mRNA expression was decreased by the administration of vitamin B6, an anti-inflammatory vitamin, and that IKKε expression levels in adipose tissue were closely correlated with the numbers of infiltrating macrophages. In a co-culture system, we showed that IKKε expression in adipocytes was upregulated by interaction with activated macrophages. This study provides novel insight into IKKε, which is involved in adipose tissue inflammation during the development of obesity.
Subject(s)
Adipocytes/cytology , Adipocytes/metabolism , Cell Communication , I-kappa B Kinase/genetics , Macrophages/cytology , Up-Regulation , 3T3-L1 Cells , Animals , Cell Count , Macrophage Activation , Macrophages/immunology , Male , Mice , RNA, Messenger/genetics , RNA, Messenger/metabolismABSTRACT
Macrophage infiltration into adipose tissue is associated with obesity and the crosstalk between adipocytes and infiltrated macrophages has been investigated as an important pathological phenomenon during adipose tissue inflammation. Here, we sought to identify adipocyte mRNAs that are regulated by interaction with infiltrated macrophages in vivo. An anti-inflammatory vitamin, vitamin B6, suppressed macrophage infiltration into white adipose tissue and altered mRNA expression. We identified >3500 genes whose expression is significantly altered during the development of obesity in db/db mice, and compared them to the adipose tissue mRNA expression profile of mice supplemented with vitamin B6. We identified PTX3 and MMP3 as candidate genes regulated by macrophage infiltration. PTX3 and MMP3 mRNA expression in 3T3-L1 adipocytes was up-regulated by activated RAW264.7 cells and these mRNA levels were positively correlated with macrophage number in adipose tissue in vivo. Next, we screened adipose genes down-regulated by the interaction with macrophages, and isolated RASSF6 (Ras association domain family 6). RASSF6 mRNA in adipocytes was decreased by culture medium conditioned by activated RAW264.7 cells, and RASSF6 mRNA level was negatively correlated with macrophage number in adipose tissue, suggesting that adipocyte RASSF6 mRNA expression is down-regulated by infiltrated macrophages in vivo. Finally, this study also showed that decreased RASSF6 expression up-regulates mRNA expression of several genes, such as CD44 and high mobility group protein HMGA2. These data provide novel insights into the biological significance of interactions between adipocytes and macrophages in adipose tissue during the development of obesity.