Xenobiotic receptors

在全球范围内，肥胖及其相关的代谢紊乱正以惊人的速度增加。能量摄入和消耗之间的不平衡导致肥胖，在啮齿动物模型中，脂肪褐变诱导是一种有吸引力的策略，可以增强非寒战产热，从而抵消多余的能量摄入。核受体已经成为治疗代谢性疾病的药物靶点，尽管对它们在调节脂肪褐变中的作用知之甚少。细胞色素P450 (CYP) 2E1的表达与代谢性疾病的病理过程密切相关。在糖尿病、禁食、肥胖和高脂肪饮食（HFD）治疗的条件下，人类和实验性啮齿动物模型中CYP2E1活性均显著升高。cyp2e1缺失小鼠免受hfd诱导的肥胖和非酒精性脂肪性肝炎的影响。过氧化物酶体增殖物激活受体α (pparα)在脂质稳态和能量调节中起着重要作用，肝脏中pparα的主要靶基因肝成纤维细胞生长因子（FGF）21的表达和分泌可能作为一种内分泌刺激剂来缓解肥胖。然而，CYP2E1影响代谢性疾病的机制尚未被探索。CYP2E1是cypp超家族的一员，最初被认为是一种乙醇诱导酶，参与多种低分子量异种生物的代谢，包括乙醇、苯、四氯化碳和对乙酰氨基酚。值得注意的是，除了这些外源药物，CYP2E1还代谢包括脂肪酸在内的内源性底物，而据报道，包括脂肪酸在内的各种内源性配体也能激活ppar。因此，CYP2E1的一些内源性底物也可能作为pparα激动剂。然而，CYP2E1和ppar α的共享底物和配体如何作为信号转导分子调节代谢性疾病在很大程度上是未知的。为了探索CYP2E1和pparα之间潜在的串扰，我们利用全球基因组学、代谢组学、CYP2E1缺失小鼠和肝脏特异性pparα缺失小鼠以及CYP2E1抑制剂二乙基二硫代氨基甲酸酯来揭示CYP2E1缺失是否以及如何通过cyp2e - pparα串扰和共享底物作为信号转导分子来调节白色脂肪褐变，从而降低肥胖。结果。虽然代谢酶和核受体在控制生理稳态中的作用已经确立，但它们在调节代谢疾病中的相互作用尚未被探索。基因消融小鼠外源代谢细胞色素P450酶CYP2E1显著诱导脂肪褐变和增加能量消耗以改善肥胖。CYP2E1缺乏激活肝脏过氧化物酶体增殖物激活受体α (ppar α)靶基因的表达，包括成纤维细胞生长因子（FGF）21，该基因从肝脏释放后，增加脂肪褐变和能量消耗，以减少肥胖。全球非靶向代谢组学结果显示，CYP2E1缺失小鼠中19种代谢物增加，其中溶血磷脂酰胆碱和3种多不饱和脂肪酸被CYP2E1直接代谢并作为pparα激动剂，从而解释了CYP2E1缺乏如何通过增加内源性pparα激动剂的细胞水平导致肝脏pparα活化。翻译，CYP2E1抑制剂被发现激活pparα - fgf21 -米色脂肪轴并减少野生型小鼠的肥胖，但在肝脏特异性Ppara-null小鼠中没有。目前的研究结果建立了ppar - α和CYP2E1之间的代谢串扰，支持了一种新的抗肥胖策略的潜力，即通过靶向CYP2E1来调节内源性代谢物，从而激活脂肪组织褐变，而不是其在外源代谢中的典型作用。项目2，ppar和FABP1：介绍。非酒精性脂肪性肝病（NAFLD）是一种常见的慢性肝病。持续性NAFLD可发展为非酒精性脂肪性肝炎（NASH），并增加发生肝硬化和肝细胞癌等终末期肝病的风险。到目前为止，还没有药物被批准用于治疗NASH，因此，NASH的药物治疗是有必要的。pparα激动剂如贝特类在临床上作为降脂药物广泛用于治疗血脂异常，但其在人类NASH治疗中的应用尚未获得批准。小鼠pparα基因敲除可显著增强NASH，但可防止胰岛素抵抗。提示ppar - α具有多效性作用。肝细胞特异性pparα基因敲除仅部分反映了NAFLD和禁食诱导的肝脂肪变性中全局pparα基因敲除的表型。了解肝外pparα的组织特异性作用可以指导pparα调节剂的药物发现。膳食脂肪被肠细胞以游离脂肪酸和由膳食甘油三酯（TG）产生的2-单酰基甘油的形式吸收，而被吸收的脂肪酸和单酰基甘油再酯化成TG并输出到血液中。已知脂肪酸结合蛋白1 （FABP1）促进脂肪酸和其他疏水分子在肝脏中的运输，而肠道FABP1在调节膳食脂肪吸收和NASH中的作用尚不清楚。结果。采用肠道特异性pparα或FABP1敲除小鼠、肠道特异性pparα /FABP1双敲除小鼠、ppara人源化小鼠、PPRE-Luc小鼠、原代肠道类器官和pparα特异性拮抗剂GW6471，结合全局转录组和分子生物学分析，研究了肠道pparα -FABP1信号在调节NASH进展中的作用。在人肠道样本上进行了ppar - α /FABP1信号与肥胖的相关性研究。过氧化物酶体增殖物激活受体α (ppar α)调节脂肪酸在肝脏中的转运和分解代谢。然而，肠道ppar在脂质稳态中的作用在很大程度上是未知的。本研究研究了肠道ppar对肥胖和非酒精性脂肪性肝炎（NASH）的调节作用。通过使用人类肠道标本或高脂肪饮食（HFD）或高脂肪、高胆固醇、高果糖饮食（HFCFD）喂养的C57BL/6N小鼠或ppara人源化的PPRE-Luciferase小鼠，肥胖者和高脂肪饮食喂养的小鼠肠道pparα被激活，FABP1上调。小鼠肠道特异性Ppara或Fabp1紊乱可降低肥胖相关代谢紊乱和NASH。荧光素酶报告基因法和染色质免疫沉淀法结合原代肠道类器官脂肪酸摄取测定的分子分析显示，肠道pparα靶向介导肠道pparα调节脂肪酸摄取作用的FABP1。pparα拮抗剂GW6471依赖于肠道pparα或FABP1改善肥胖和NASH。pparα和FABP1双敲除小鼠显示，肠道Ppara破坏未能在缺乏肠道FABP1的情况下进一步减少肥胖和NASH。反过来，GW6471减少了人类ppara驱动的肠道脂肪酸摄取，并改善了ppara人源化小鼠的肥胖相关代谢功能障碍，而不是ppara缺失小鼠。这项研究显示t *TRUNCATED*

Project 1, PPARalpha and CYP2E1: : Introduction Obesity and the associated metabolic disorders are increasing at an alarming rate globally. An imbalance between energy intake and expenditure results in obesity, and adipose browning induction is one attractive strategy in rodent models for enhancing non-shivering thermogenesis and thus countering the excess energy intake. Nuclear receptors have become drug targets for the treatment of metabolic diseases, although less is known about their roles in the modulation of adipose browning. Cytochrome P450 (CYP) 2E1 expression was suggested to be closely related to the pathological process of metabolic diseases. CYP2E1 activity is significantly increased in both humans and experimental rodent models under conditions of diabetes, fasting, obesity, and high-fat diet (HFD) treatment. Cyp2e1-null mice are protected from HFD-induced obesity and nonalcoholic steatohepatitis. Peroxisome proliferator-activated receptor alpha (PPARalpha) plays an essential role in lipid homeostasis and energy regulation, and the expression and excretion of hepatic fibroblast growth factor (FGF)21, a major PPARalpha target gene in liver, could act as an endocrinal beige stimulator to alleviate the obesity. However, the mechanism by which CYP2E1 affects metabolic diseases has not been explored. CYP2E1, a member of the CYP superfamily, was initially identified as an ethanol-inducible enzyme involved in the metabolism of various low-molecular weight xenobiotics including ethanol, benzene, carbon tetrachloride, and acetaminophen. Notably beyond these xenobiotics, CYP2E1 also metabolizes endogenous substrates including fatty acids, while various endogenous ligands also including fatty acids were reported to activate PPARalpha. Thus, it is possible that some of the endogenous substrates of CYP2E1 also serve as PPARalpha agonists. However, how the shared substrates and ligands of CYP2E1 and PPARalpha could act as signaling-transducing molecules in modulating the metabolic diseases are largely unknown. To explore the potential crosstalk between CYP2E1 and PPARalpha, global genomics, metabolomics in combination with Cyp2e1-null mice and liver-specific Ppara-null mice as well as the CYP2E1 inhibitor diethyldithiocarbamate were employed to uncover whether and how CYP2E1 deficiency decreased obesity by modulating white adipose browning through the CYP2E-PPARalpha crosstalk with shared substrates as signaling-transducing molecules. Results. Although the functions of metabolic enzymes and nuclear receptors in controlling physiological homeostasis have been established, their crosstalk in modulating metabolic disease has not been explored. Genetic ablation of the xenobiotic-metabolizing cytochrome P450 enzyme CYP2E1 in mice markedly induced adipose browning and increased energy expenditure to improve obesity. CYP2E1 deficiency activated the expression of hepatic peroxisome proliferator-activated receptor alpha (PPARalpha) target genes, including fibroblast growth factor (FGF)21, that upon release from the liver, enhanced adipose browning and energy expenditure to decrease obesity. Nineteen metabolites were increased in Cyp2e1-null mice as revealed by global untargeted metabolomics, among which four compounds, lysophosphatidylcholine and three polyunsaturated fatty acids were found to be directly metabolized by CYP2E1 and to serve as PPARalpha agonists, thus explaining how CYP2E1 deficiency causes hepatic PPARalpha activation through increasing cellular levels of endogenous PPARalpha agonists. Translationally, a CYP2E1 inhibitor was found to activate the PPARalpha-FGF21-beige adipose axis and decrease obesity in wild-type mice, but not in liver-specific Ppara-null mice. The present results establish a metabolic crosstalk between PPARalpha and CYP2E1 that supports the potential for a novel anti-obesity strategy of activating adipose tissue browning by targeting the CYP2E1 to modulate endogenous metabolites beyond its canonical role in xenobiotic-metabolism. Project 2, PPARalpha and FABP1: Introduction. Nonalcoholic fatty liver disease (NAFLD) is a common chronic liver diseases. Persistent NAFLD could progress to nonalcoholic steatohepatitis (NASH) and increase the risk of the end-stage liver diseases such as cirrhosis and hepatocellular carcinoma. To date, no drug has been approved for the treatment of NASH, and thus, pharmacological therapies for NASH treatment are warranted. PPARalpha agonists such as fibrates are widely prescribed for the treatment of dyslipidemias as lipid-lowering drugs in clinic, however, their use in human NASH treatment has not been approved. Global PPARalpha knockout in mice markedly enhances NASH but protects against insulin resistance. suggesting the pleiotropic roles of PPARalpha. Hepatocyte-specific PPARalpha knockout was found to only partially phenocopy the phenotype of global PPARalpha knockout in NAFLD and fasting-induced hepatic steatosis. Understanding the tissue-specific role of extrahepatic PPARalpha may guide drug discovery from PPARalpha modulators. Dietary fat is absorbed by the enterocytes in the form of free fatty acids and 2-monoacylglycerols that are produced from dietary triglycerides (TG), while the absorbed fatty acids and monoacylglycerols are re-esterified into TG and exported to the blood. Fatty acid-binding protein 1 (FABP1) is known to facilitate transport of fatty acids and other hydrophobic molecules in the liver, while the role of intestinal FABP1 in modulating dietary fat absorption and NASH is still unknown. Results. The role of intestine PPARalpha-FABP1 signaling in modulating the NASH progression was studied using intestine-specific PPARalpha or FABP1 knockout mice, intestine-specific PPARalpha/FABP1 double knockout mice, PPARA-humanized mice, PPRE-Luc mice, primary intestinal organoids, and PPARalpha-specific antagonist GW6471 in combination with global transcriptome and molecular biological analyses. Correlative studies on PPARalpha/FABP1 signaling with obesity were carried out on human intestine samples. Peroxisome proliferator-activated receptor alpha (PPARalpha) regulates fatty acid transport and catabolism in liver. However, the role of intestinal PPARalpha in lipid homeostasis is largely unknown. Here, intestinal PPARalpha was examined for its modulation of obesity and nonalcoholic steatohepatitis (NASH). Intestinal PPARalpha was activated and FABP1 upregulated in obese humans and high-fat diet-fed mice by using human intestine specimens or high-fat diet (HFD) or high-fat, high-cholesterol, high-fructose diet (HFCFD)-fed C57BL/6N mice or PPARA-humanized PPRE-Luciferase mice. Intestine-specific Ppara or Fabp1 disruption in mice fed a HFD or HFCFD decreased obesity-associated metabolic disorders and NASH. Molecular analyses by luciferase reporter assays and chromatin-immunoprecipitation assays in combination with fatty acid uptake assay in primary intestinal organoids revealed that intestinal PPARalpha targeted FABP1 that mediated the effects of intestinal PPARalpha in modulating fatty acid uptake. The PPARalpha antagonist GW6471 improved obesity and NASH, dependent on intestinal PPARalpha or FABP1. PPARalpha and FABP1 double-knockout mice revealed that intestinal Ppara disruption failed to further decrease obesity and NASH in the absence of intestinal FABP1. Translationally, GW6471 reduced human PPARA-driven intestinal fatty acid uptake and improved obesity-related metabolic dysfunctions in PPARA-humanized, but not Ppara-null, mice. This study revealed t *TRUNCATED*