title: The Prostaglandin E2 Receptor EP4 Regulates Obesity-Related Inflammation and Insulin Sensitivity.
abstract: With increasing body weight, macrophages accumulate in adipose tissue. There, activated macrophages secrete numerous proinflammatory cytokines and chemokines, giving rise to chronic inflammation and insulin resistance. Prostaglandin E2 suppresses macrophage activation via EP4; however, the role of EP4 signaling in insulin resistance and type 2 diabetes mellitus remains unknown. In this study, we treated db/db mice with an EP4-selective agonist, ONO-AE1-329, for 4 weeks to explore the role of EP4 signaling in obesity-related inflammation in vivo. Administration of the EP4 agonist did not affect body weight gain or food intake; however, in the EP4 agonist-treated group, glucose tolerance and insulin resistance were significantly improved over that of the vehicle-treated group. Additionally, administration of the EP4 agonist inhibited the accumulation of F4/80-positive macrophages and the formation of crown-like structures in white adipose tissue, and the adipocytes were significantly smaller. The treatment of the EP4 agonist increased the number of anti-inflammatory M2 macrophages, and in the stromal vascular fraction of white adipose tissue, which includes macrophages, it markedly decreased the levels of proinflammatory cytokines and chemokines. Further, EP4 activation increased the expression of adiponectin and peroxidase proliferator-activated receptors in white adipose tissue. Next, we examined in vitro M1/M2 polarization assay to investigate the impact of EP4 signaling on determining the functional phenotypes of macrophages. Treatment with EP4 agonist enhanced M2 polarization in wild-type peritoneal macrophages, whereas EP4-deficient macrophages were less susceptible to M2 polarization. Notably, antagonizing peroxidase proliferator-activated receptor δ activity suppressed EP4 signaling-mediated shift toward M2 macrophage polarization. Thus, our results demonstrate that EP4 signaling plays a critical role in obesity-related adipose tissue inflammation and insulin resistance by regulating macrophage recruitment and polarization. The activation of EP4 signaling holds promise for treating obesity and type 2 diabetes mellitus.
authors: Department of Clinical Innovative Medicine, Kyoto University Graduate School of Medicine, Kyoto, Kyoto, Japan.
authors: Mika
authors: M
authors: Yasui
authors: Department of Clinical Innovative Medicine, Kyoto University Graduate School of Medicine, Kyoto, Kyoto, Japan; Department of Physiology and Regenerative Medicine, Kinki University Faculty of Medicine, Osakasayama, Osaka, Japan.
authors: Yukinori
authors: Y
authors: Tamura
authors: Department of Clinical Innovative Medicine, Kyoto University Graduate School of Medicine, Kyoto, Kyoto, Japan.
authors: Manabu
authors: M
authors: Minami
authors: Department of Clinical Innovative Medicine, Kyoto University Graduate School of Medicine, Kyoto, Kyoto, Japan.
authors: Sei
authors: S
authors: Higuchi
authors: Department of Clinical Innovative Medicine, Kyoto University Graduate School of Medicine, Kyoto, Kyoto, Japan.
authors: Risako
authors: R
authors: Fujikawa
authors: Department of Clinical Innovative Medicine, Kyoto University Graduate School of Medicine, Kyoto, Kyoto, Japan; Department of Neurosurgery, Kyoto University Graduate School of Medicine, Kyoto, Kyoto, Japan.
authors: Taichi
authors: T
authors: Ikedo
authors: Department of Clinical Innovative Medicine, Kyoto University Graduate School of Medicine, Kyoto, Kyoto, Japan; Department of Neurosurgery, Kyoto University Graduate School of Medicine, Kyoto, Kyoto, Japan.
authors: Manabu
authors: M
authors: Nagata
authors: National Center for Geriatrics and Gerontology, Obu, Aichi, Japan.
authors: Hidenori
authors: H
authors: Arai
authors: Department of Clinical Innovative Medicine, Kyoto University Graduate School of Medicine, Kyoto, Kyoto, Japan.
authors: Toshinori
authors: T
authors: Murayama
authors: Department of Clinical Innovative Medicine, Kyoto University Graduate School of Medicine, Kyoto, Kyoto, Japan.
authors: Masayuki
authors: M
authors: Yokode
mesh_terms: D000273:Adipose Tissue / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D018925:Chemokines / Q000235:genetics / Q000378:metabolism; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D004195:Disease Models, Animal; D007249:Inflammation / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D007333:Insulin Resistance; D008262:Macrophage Activation / Q000187:drug effects; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008738:Methyl Ethers / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D009765:Obesity / Q000150:complications*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D058309:Receptors, Prostaglandin E, EP4 Subtype / Q000819:agonists* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction
chemical_list: D018925:Chemokines; D016207:Cytokines; D008738:Methyl Ethers; C461399:ONO-AE1-329; D012333:RNA, Messenger; D058309:Receptors, Prostaglandin E, EP4 Subtype