Obesity is recognized as a risk factor for lifestyle-related diseases such as type 2 diabetes and cardiovascular disease. White adipose tissue (WAT) is not only a static storage site for energy; it is also a dynamic tissue that is actively involved in metabolic reactions and produces humoral factors, such as leptin and adiponectin, which are collectively referred to as adipokines. Additionally, because there is much evidence that obesity-induced inflammatory changes in WAT, which is caused by dysregulated expression of inflammation-related adipokines involving tumor necrosis factor-α and monocyte chemoattractant protein 1, contribute to the development of insulin resistance, WAT has attracted special attention as an organ that causes diabetes and other lifestyle-related diseases. Exercise training (TR) not only leads to a decrease in WAT mass but also attenuates obesity-induced dysregulated expression of the inflammation-related adipokines in WAT. Therefore, TR is widely used as a tool for preventing and improving lifestyle-related diseases. This review outlines the impact of TR on the expression and secretory response of adipokines in WAT.

Obesity-induced inflammatory changes in white adipose tissue (WAT), which caused dysregulated expression of inflammation-related adipokines involving tumor necrosis factor-α and monocyte chemoattractant protein-1, contribute to the development of insulin resistance. Moreover, current literature reports state that WAT generates reactive oxygen species (ROS), and the enhanced production of ROS in obese WAT has been closely associated with the dysregulated expression of adipokines in WAT. Therefore, the reduction in excess WAT and oxidative stress that results from obesity is thought to be one of the important strategies in preventing and improving lifestyle-related diseases. Exercise training (TR) not only brings about a decrease in WAT mass but also attenuates obesity-induced dysregulated expression of the adipokines in WAT. Furthermore, some reports indicate that TR affects the generation of oxidative stress in WAT. This review outlines the impact of TR on the expression of inflammation-related adipokines and oxidative stress in WAT.

Macrophages are distributed in all peripheral tissues and play a critical role in the first line of the innate immune defenses against bacterial infection by phagocytosis of bacterial pathogens through the macrophage scavenger receptor 1 (MSR1). Within tissues, the partial pressure of oxygen (pO2) decreases depending on the distance of cells from the closest O2-supplying blood vessel. However, it is not clear how the expression of MSR1 in macrophages is regulated by low pO2. On the other hand, hypoxia-inducible factor (HIF)-1alpha is well known to control hypoxic responses through regulation of hypoxia-inducible genes. Therefore, we investigated the effects of hypoxia and HIF-1alpha on MSR1 expression and function in the macrophage cell line RAW264. Exposure to 1% O2 or treatment with the hypoxia-mimetic agent cobalt chloride (CoCl2) significantly suppressed the expression of MSR1 mRNA, accompanied by a markedly increase in levels of nuclear HIF-1alpha protein. The overexpression of HIF-1alpha in RAW264 cells suppressed the expression of MSR1 mRNA and protein, transcriptional activity of the MSR1 gene, and phagocytic capacity against the Gram-positive bacteria Listeria monocytogenes. The suppression of MSR1 mRNA by hypoxia or CoCl2 was inhibited by YC-1, an inhibitor of HIF-1alpha, or by the depletion of HIF-1alpha expression by small interference RNA. These results indicate that hypoxia transcriptionally suppresses MSR1 expression through HIF-1alpha.

It is now evident that many nuclear hormone receptors can modulate target gene expression. REV-ERBα, one of the nuclear hormone receptors with the capacity to alter clock function, is critically involved in lipid metabolism, adipogenesis, and the inflammatory response. Recent studies suggest that REV-ERBα plays a key role in the mediation between clockwork and inflammation. The purpose of the current study was to investigate the role of REV-ERBα in the regulation of interleukin-6 (il6) gene expression in murine macrophages. REV-ERBα agonists, or overexpression of rev-erb α in the murine macrophage cell line RAW264 cells, suppressed the induction of il6 mRNA following a lipopolysaccharide (LPS) endotoxin challenge. Also, rev-erb α overexpression decreased LPS-stimulated nuclear factor κB (NFκB) activation in RAW264 cells. We showed that REV-ERBα represses il6 expression not only indirectly through an NFκB binding motif but also directly through a REV-ERBα binding motif in the murine il6 promoter region. Furthermore, peritoneal macrophages from mice lacking rev-erb α increased il6 mRNA expression. These data suggest that REV-ERBα regulates the inflammatory response of macrophages through the suppression of il6 expression. REV-ERBα may therefore be identified as a potent anti-inflammatory receptor and be a therapeutic target receptor of inflammatory diseases.

BackgroundIn adipose cells, adipose triglyceride lipase (ATGL) catalyzes the first step in adipocyte triacylglyceride hydrolysis, thereby regulating both basal and hormone-stimulated lipolysis. However, little is known about the molecular mechanism(s) underlying habitual exercise-induced adaptive modulation of ATGL in white adipocytes via alteration in transcription regulator and lipolytic cofactors.Methodology/Principal ResultsMale Wistar rats were randomly divided into 2 groups a sedentary control group (CG) and a habitual exercise group (EG). The EG was subjected to running on a treadmill set at 5 days per week for 9 weeks. The CG was not subjected to running on a treadmill. In the EG, levels of ATGL mRNA and protein were elevated with a significant increase in lipolysis compared with the CG, accompanied by a significant increase in associations of CGI-58 with ATGL protein. Under these conditions, an upregulation of peroxisome proliferation-activated receptorg-2 (PPARg-2) was observed. In the EG, the addition of rosiglitazone further significantly increased the levels of ATGL protein compared with the CG. However, attenuated levels of the ATGL protein in adipocytes were obtained by the addition of insulin, which is known to inhibit the expression of ATGL, in both types of groups. Actually, levels of plasma insulin were significantly reduced in the EG compared with the CG.ConclusionsThese data suggest that elevated levels of ATGL are involved in the exercise-induced enhancement of lipolysis in primary adipocytes. The exact mechanism(s) underlying this phenomenon is associated, at least in part, with upregulated transcriptional activation of PPARg-2. In addition, exercise-induced lower circulation levels of insulin also correlate with habitual exercise-induced higher levels of ATGL in primary adipocytes.