Abstract
摘要:肥胖已成為全人類健康的巨大威脅,因為肥胖已被證明和很多慢性疾病有關係。其會導致胰島素抗性,引發身體多種代謝性異常,進一步造成第二型糖尿病、動脈粥狀硬化、甚至是癌症。目前已知脂肪組織所分泌的脂肪因子會影響胰島素阻抗和形成代謝疾病,而其中脂締素(adiponectin)即是重要的脂肪因子之一。脂締素具有增加胰島素敏感度和抗癌作用,而脂肪組織在缺氧下會引起胰島素阻抗性並調控脂締素的生成。激酶Polo-like kinase 3 (PLK3)是個對於細胞週期調控的腫瘤抑制基因。除了多發性腫瘤外,Plk3基因剔除老鼠的體重也有上升現象。同時在缺氧情況下,plk3-/-小鼠胚胎纖維母細胞會超誘導缺氧誘發因子HIF-1α的生成。而我們初步研究發現,抑制PLK3的表現可使人類脂肪細胞中脂締素的mRNA、蛋白質分泌量下降,並降低脂肪細胞分化程度;相反地,大量表現PLK3則會使脂締素表現量增加,並與調控HIF-1 α的生成有關。在人類脂肪組織的臨床統計分析上,我們發現內臟脂肪(VAT)與皮下脂肪(SAT)的PLK3 mRNA量與脂締素的mRNA 及血中脂締素濃度呈現強烈正相關性。同時在校正完年齡,性別及BMI後,SAT的PLK3 mRNA量仍會與胰島素阻抗指標HOMA-IR及發炎指標C-反應蛋白呈負相關性。這些初步結果暗示了PLK3與脂締素表現量有關,同時在胰島素敏感性、脂肪細胞分化、醣類及脂質代謝可能扮演相當重要的角色,我們將試圖找出其可能的作用機制並利用動物實驗來驗證。 本計畫共計執行三年並預計完成下列工作: 1. 研究PLK3在人類脂肪細胞分化下,經由及非經由HIF-1α調控脂締素表現的作用機制。 2. 研究PLK3在影響人類脂肪細胞分化,胰島素敏感性及葡萄糖/脂質代謝所扮演的角色。 3. 利用質譜定量技術分析磷酸化蛋白體研究找出人類脂肪細胞分化中,PLK3的訊息傳遞路徑及其調控標的。 4. 利用免疫沈澱法及質譜技術找出在人類脂肪細胞分化過程中與PLK3交互作用的蛋白質並探討其功能。 5. 利用plk3-/-所分離的脂肪前身細胞探討PLK3於脂肪分化的角色,並於高脂飼料餵養下探討plk3-/-老鼠影響脂締素表現,評估其生理及病理包括胰島素敏感性、醣類及脂質代謝等變化。 6. 於厭氧環境下探討plk3-/-老鼠影響脂締素表現,並評估其生理、病理及基因變化。
Abstract: Obesity is a serious and growing public health problem that contributes to a wide range of disease conditions. Many epidemiological studies and experimental observations have revealed an association between obesity and a number of chronic diseases such as type 2 diabetes, atherosclerosis and cancer. Adipose-secreted adipokines are implicated in the causation of systemic insulin resistance and its related metabolic disorders. One of the major adipokines, the adiponectin, has been shown to possess insulin sensitizing and anti-cancer effects. Adipose tissue hypoxia involves in many metabolic dyresgulation such as insulin resistance and down-regulation of adiponectin expression. Polo-like kinase 3 (PLK3) is a tumor suppressor gene which plays important roles in cell cycle control in responses to genotoxic stress. In addition to the development of multiple tumors, plk3-/ - mice also displayed increase weight. plk3-/ -mouse embryonic fibroblasts (MEF) were hypersensitive to the induction of HIF-1α under hypoxic condition. In our preliminary data, we found that silencing of PLK3 causes a decrease of adiponectin mRNA and protein, followed by a reduction of Oil-red O staining and quantitation during human preadipocyte differentiation; while overexpressed PLK3 displayed vice versa. The regulation was found by partially acting through HIF-1α. Consistently, our clinical data shown that PLK3 mRNA levels in both visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were strongly and positively correlated with adiponectin gene expression, as well as circulating adiponectin concentration. The PLK3 mRNA expression in SAT was negatively correlated with HOMA-IR and CRP levels even after adjustment of age, sex and BMI. These findings implied that PLK3 may play an important role in modulating adiponectin expression, insulin sensitivity, as well as systemic energy homeostasis and adipocyte differentiation. Therefore, in this proposal we attempt to find out causal link and the underlying mechanisms following specific goals in three years: 1. Explore the molecular mechanism of PLK3 regulates adiponectin gene expression under HIF-1α-dependent and -independent pathways in human preadipocyte model. 2. To demonstrate the adipogenic effect, insulin sensitivity and glucose/lipid metabolism of PLK3 in human preadipocyte model. 3. Using quantitative phosphoproteomics to delineate the signaling pathways and identify the novel targets of PLK3 during human preadipocyte differentiation. 4. Using co-immunoprecipitation-coupled mass spectroscopy to identify novel PLK3 interacting partners and related biological functions during human preadipocyte differentiation. 5. To test the potential effects of plk3-/- mice on adiponectin, adipogenesis, glucose/insulin sensitivity, and inflammatory effects under chow/high fat diet animal model. 6. To test the potential effects of plk3-/- mice on adiponectin-raising, gene expression changes, physiological and pathological effects under hypoxic stress.
Keyword(s)
激酶
脂締素
PLK3
肥胖症
胰島素敏感性
Polo-like kinase 3
adiponectin
insulin sensitivity
obesity