THE ENDOTHELIAL PPARy-RXR TRANSCRIPTIONAL COMPLEX IN THE CONTROL OF METABOLISM

过氧化物酶体增殖物激活受体-视黄酸X受体(PPARy-RXR) 转录复合体通过控制与脂肪酸和葡萄糖的新陈代谢、摄取、氧化燃烧和储存有关的基因来调节能量平衡。PPARy-RXR复合体还调节炎症、氧化应激和动脉粥样硬化，包括通过它们对内皮的影响。尽管血管内皮功能通常是根据血管运动反应性来定义的，但我们 假设内皮细胞也参与了系统新陈代谢的控制。我们发现 与对照组相比，喂食高脂饮食的内皮PPARy缺陷小鼠表现出减少肥胖和改善胰岛素敏感性，但显著提高FA和甘油三酯(TG)水平和受损的内皮反应性。因此，这些小鼠(接受和不接受骨髓移植的Tie2Cre/FLOXED PPARy小鼠)分离了内皮功能的代谢和血管成分，为研究代谢的内皮控制提供了机会。目的1研究内皮细胞PPARy对脂肪酸和甘油水平的控制如何影响内皮细胞的反应、肝脏甘油三酯蓄积和胰岛素敏感性。目的2探讨内皮PPARy缺陷小鼠氧化应激增加的来源，包括氧化在内源性PPARy配体形成中的作用。尽管我们和其他人已经证明PPARy可以抑制内皮炎性反应，包括内皮趋化因子的表达，但这种反式抑制的机制尚不清楚。目的3研究PPARy翻译后SUMO化参与PPARy介导的特定趋化因子亚群的抑制和白细胞募集，包括炎症细胞向脂肪组织募集的证据。尽管所有这些和其他PPARy作用都需要RXR作为专有的异二聚体PPARy伙伴，但对RXR在内皮细胞中的作用和RXR的激活知之甚少。我们最近报道了视黄醛，它由视黄醛转化而来 脱氢酶(RAIDH)转化为维甲酸(RA)，存在于脂肪中，可以抑制PPARy-RXR的活性。 Raldhi基因缺陷的小鼠增加了脂肪的摄入，完全可以预防饮食引起的肥胖和糖尿病。目的4将研究血管内皮细胞的维甲酸代谢途径和Raldhi缺陷小鼠氧化应激增加的来源。这些研究将通过与其他项目和核心实验室的密切合作，确定内皮PPARy-RXR复合体如何参与整合内皮功能的代谢和血管成分。

The peroxisome proliferator-activated receptor gamma-retinoid X receptor (PPARy-RXR) transcriptional complex regulates energy balance by controlling genes involved in the metabolism, uptake, oxidative combustion and storage of fatty acids (FAs) and glucose. The PPARy-RXR complex also modulates inflammation, oxidant stress and atherosclerosis, including through their effects in the endothelium. Although endothelial function is usually defined in terms of vasomotor reactivity, we hypothesize the endothelium is also involved in the control of systemic metabolism. We found that endothelial PPARy-deficient mice fed a high fat diet manifest decreased adiposity and improved insulin sensitivity but markedly elevated FA and triglyceride (TG) levels and impaired endothelial reactivity, all as compared to control mice. As such, these mice (Tie2Cre/floxed PPARy mice with and without bone marrow transplantation) disassociate metabolic and vascular components of endothelial function, providing opportunities for studying endothelial control of metabolism. Aim 1 will investigate how endothelial PPARy's control of FA and glycerol levels influences endothelial responses, hepatic TG accumulation and insulin sensitivity. Aim 2 will investigate the source of the increased oxidant stress evident in endothelial PPARydeficient mice, including the role of oxidation in endogenous PPARy ligand formation. Although we and others have shown that PPARy can inhibit endothelial inflammatory responses, including endothelial chemokine expression, the mechanisms for this trans-repression have remained unclear. Aim 3 will investigate the evidence provided here that post-translatioiial SUMOylation of PPARy is involved in PPARymediated repression of specific chemokine subsets and leukocyte recruitment, including inflammatory cell recruitment to adipose tissue. Although all these and other PPARy actions require RXR as an obligate heterodimeric PPARy partner, very little is known about the role of retinoid metabolism and RXR activation in the endothelium. We recently reported that retinaldehyde, which is converted by retinaldehyde dehydrogenase (RaIdh) to retinoic acid (RA), is present in fat where it can repress PPARy-RXR activity. Raldhi-deficient mice, which have increased Raid in fat, are completely protected against diet-induced obesity and diabetes. Aim 4 will investigate pathways of retinoid metabolism in endothelial cells and the sources of the increased oxidant stress in Raldhi-deficient mice shown here. Together these studies, through close collaboration with the other Projects and Core Laboratories, will identify how the endothelial PPARy-RXR complex is involved in integrating metabolic and vascular components of endothelial function.