摘要:代謝異常,特別是肥胖症與第2型糖尿病,已成為全人類健康的巨大威脅。PPARγ在代謝過程扮演了重要的角色,然而,內生性的PPARγ配體,目前尚未確定。許多研究證實前列腺素與其相關合成酵素對白色/棕色脂肪細胞分化、胰島素敏感性和能量恆定扮演相當重要的角色,前列腺素或其相關合成酵素功能異常將導致嚴重的代謝症候群。在我們先前的細胞研究實驗中,我們發現前列腺素還原酶3 (prostaglandin reductase 3, PTGR-3)具有催化15-keto-PGE2還原成13,14-dihydro-15-keto-PGE2的酵素活性。我們也証實15-keto-PGE2是內源性PPARγ的配體,會調控PPARγ活性進而影響脂肪細胞分化與葡萄糖恆定,在白色脂肪前身細胞中抑制PTGR-3基因表現可促進其脂肪細胞分化。我們也發現PTGR-3表現量在白色脂肪細胞分化過程中下降,但在棕色脂肪細胞分化過程中上升。目前除已知PTGR-3可抑制PPARγ活性與脂肪細胞分化外,對PTGR-3的生理功能了解極為有限。因此本計畫將研究PTGR-3及其相關代謝產物是否在小鼠與人類中與葡萄糖與脂質代謝有關。在我們的初步人類臨床研究發現內臟脂肪組織的PTGR-3表現量與BMI以及血中胰島素成正相關,而與血中高密度脂蛋白、脂締素成負相關。除此之外,PTGR-3表現量在肥胖鼠的白色脂肪組織也下降,這些初步結果暗示了PTGR-3對能量代謝扮演重要之角色,但因果關係與其調節機制仍是未知。因此我們將進行以下的研究:我們計劃在未來三年完成:1. 利用基因剔除小鼠所分離的白色/棕色脂肪前身細胞探討PTGR-3在白色/棕色脂肪分化的角色。2. 利用基因剔除小鼠所分離的白色/棕色脂肪細胞、肝細胞和肌肉細胞探討PTGR-3在葡萄糖/脂質代謝、前列腺素代謝、粒線體功能和胰島素敏感性的角色。3. 研究PTGR-3所調控的下游基因與參與的訊息傳遞途徑。4. 利用代謝體技術闡明何種PTGR-3相關代謝物調控主要的代謝路徑。5. 以ptgr-3-/-剔除小鼠和ptgr-3-/- ptgr-2-/-雙基因剔除鼠為動物模式,經餵食高脂飲食後,評估其前列腺素代謝、脂質代謝、粒線體功能、血壓、胰島素敏感性以及血糖的變化。6. 評估糖尿病鼠Lepob/ob經PTGR-3抑制劑處理後,前列腺素代謝、脂質代謝、粒線體功能、血壓、胰島素敏感性以及血糖的影響。
Abstract: Obesity and type 2 diabetes have become global epidemic with huge impact on humanhealth. Peroxisome proliferator-activated receptor γ(PPARγ) is a ligand-activated nuclearreceptor that plays an important role in regulating adipocyte differentiation and glucosehomeostasis. However, the endogenous ligand for PPARγ remained uncertain.Prostaglandins and their synthases have been shown to be potent modulators of white/brownadipocyte differentiation, insulin sensitivity and energy homeostasis. Dysregulation ofprostaglandins or prostaglandin synthases lead to metabolic disorders. In our previousresearch, we found that prostaglandin reductase 3 (PTGR-3) is an novel enzyme thatcatalyzes the conversion of 15-keto-PGE2 to 13,14-dihydro-15-keto-PGE2 and alsodemonstrated that 15-keto-PGE2 is potential endogenous ligand for PPARγ. In cultured cellmodel, knockdown of PTGR-3 expression in white preadipocytes increased adipogenesisthrough activation of PPARγ. Furthermore, PTGR-3 expressin is decresed during whiteadipogenesis but increased during brown adipogenesis. This data indicated PTGR-3negatively modulates adipocyte differentiation through regulation ofPPARγ activityin vitro.However, little is known about physiological function of PTGR-3 in vivo.In our preliminary clinical data, we found that PTGR-3 expression in human visceraladipose tissue is positively correlated with body mass index (BMI) and plasma insulin levelbut negatively associated with plasma HDL and adiponectin level. Furthermore, wediscovered that PTGR-3 mRNA expression is decreased in white adipose tissue of obesemice model. Taken together, these findings implied that PTGR-3 may play an important rolein modulating systemic energy homeostasis and white/brown adipocyte differentiation, butthe causal link and the underlying mechanisms remain uncertain. Therefore, in this proposalwe plan to study the followings:1. To test the hypothesis that PTGR-3 affects white/brown adipocyte commitment anddifferentiation2. To test the hypothesis that PTGR-3 plays a role in glucose/lipid metabolism,prostaglandin metabolism, mitochondria function and insulin signaling of white/brownadipocytes, myotubes, and liver cells3. To dissect the downstream signaling pathways regulated by PTGR-34. To confirm that PTGR-3-related metabolites regulates distinct metabolic pathways5. To test the hypothesis that PTGR-3 modulates prostaglandin metabolism, lipidmetabolism, mitochondrial function, blood pressures and insulin sensitivity in vivo6. To confirm the effect of PTGR-3 inhibitors in prostaglandin metabolism, lipidmetabolism, mitochondrial function, blood pressures and insulin sensitivity in vivo