Cytochrome P4501B1 and basal liver PPARa activity

描述(申请人提供)：细胞色素P450 1b1(细胞色素P450 1b1)参与胚胎发育，表达于内皮细胞、成纤维细胞和脂肪细胞。尽管在肝细胞中只有很少的表达，但参与肝脏脂肪酸代谢的基因在小鼠中的缺失会受到显著的影响。两个基因簇，根据对饮食脂肪的反应而不同，都受到CYP1B1缺失的抑制和PPAR的调节？初步数据表明，CYP1B1参与了内源性PPAR？将进一步探索配体。CYP1B1缺失还可以抑制饮食诱导的肥胖和非酒精性肝脏脂肪变性。肝脏脂肪酸代谢增加可能与氧化应激降低有关，如胰岛素敏感性的改善所表明的那样。因此，CYP1B1可能是导致2型糖尿病的一个意想不到的因素。许多饮食中的类黄酮类化合物都是细胞色素P1B1的有效抑制剂。选择CYP1B1抑制剂，包括天然化合物，可能对糖尿病有治疗价值。抑制人类细胞色素P1B1也可增强肝腺瘤，这与发育过程中的作用一致。这项拟议的研究比较了接受低脂肪/高碳水化合物或高脂肪/低碳水化合物饮食的WT和CyP1B1-Ko小鼠的肝脏基因表达、代谢反应和脂肪变化。其目的是确定在其他类型的细胞中，尤其是肝窦和脂肪组织的内皮细胞中，肝细胞如何受到CYP1B1代谢的间接影响。细胞色素P1B1在非实质性肝细胞和胎肝中的表达将被描述。为了确定Cypb1干预的位置和时机，我们在小鼠中引入了一种Floating的CYP1B1等位基因。这最终将为受控的小鼠细胞色素P1B1基因缺失提供手段。我们将使用这一组明确的肝脏和脂肪反应来确定Tie2-CRE针对内皮细胞的CYP1B1缺失的有效性。我们已经证明，在体内，CYP1B1缺失会影响内皮细胞的功能，并抑制血管生成。CYP1B1的缺失可能通过积极参与胎儿肝脏发育而导致这些成人的变化，从而印记成人肝脏的调节。在发育过程中的特定时间，将通过他莫昔芬依赖的启动子激活Cre靶向的FLOXY CYP1B1，以测试这种早期表达是否有助于一般的缺失效应。分别对肝脏和血清提取物进行2D-核磁共振和质谱分析的代谢组学研究将侧重于确定CYP1B1缺失会增加线粒体脂肪酸氧化和糖原合成，同时降低氧化应激。PPAR的角色是什么？PPAR呢？将通过与删除小鼠肝脏中这些PPAR基因的效果进行比较，来测试这些肝脏基因变化的丢失情况。可用于临床研究的血清标志物将用于探测这些肝脏变化。 公共卫生相关性：人类细胞色素P450 1b1(CYP1B1)的缺失与青光眼和肝脏肿瘤有关。CYP1B1变异体在人类中很常见。我们发现，CYP1B1的缺失可以对抗肥胖，改善胰岛素敏感性。这些研究阐述了CYP1B1缺失如何通过抑制PPAR？活性显著增加肝脏脂肪氧化和糖原合成。该途径提供了治疗的可能性，包括通过与CYP1B1结合的饮食化合物。

DESCRIPTION (provided by applicant): Cytochrome P450 1b1 (Cyp1b1) participates in embryogenesis and is expressed in endothelia, fibroblasts and adipocytes. Genes involved in liver fatty acid metabolism are remarkably affected by deletion of Cyp1b1 in mice, despite only minimal expression in hepatocytes. Two gene clusters, distinguished by responses to dietary fat, are both suppressed by Cyp1b1 deletion and regulated by PPAR? Preliminary data that indicates that Cyp1b1 participates in the generation of endogenous PPAR? ligands will be explored further. Cyp1b1 deletion also suppresses diet-induced obesity and non-alcoholic hepatic steatosis. The increased liver fatty acid metabolism may be associated with decreased oxidative stress, as indicated by improved insulin sensitivity. Cyp1b1 may, therefore, be an unexpected contributor to Type 2 diabetes. Many dietary flavanoids are potent inhibitors of Cyp1b1. Select Cyp1b1 inhibitors, including natural compounds, may have therapeutic value for diabetes. Human Cyp1b1 suppression also enhances liver adenomas, consistent with a role in developmental processes. The proposed research compares the liver gene expression, metabolism responses and adiposity changes in WT and Cyp1b1-ko mice administered low fat/high carbohydrate or high fat/low carbohydrate diets. The goal is to determine how hepatocytes can be indirectly affected by Cyp1b1 metabolism in other cell types, particularly the endothelia of liver sinusoids and adipose tissue. The expression of Cyp1b1 in non-parenchymal liver cells and in fetal liver will be characterized. In order to define the site and timing of Cypb1 intervention, we have introduced a Floxed Cyp1b1 allele into mice. This will ultimately provide the means for controlled Cyp1b1 deletions in mice. We will use this defining set of liver and adipose responses to determine the effectiveness of Cyp1b1 deletions specifically targeted to endothelia by Tie2-Cre. We have shown that Cyp1b1 deletion affects the functions of endothelial cells and suppresses angiogenesis in vivo. Cyp1b1 deletion may cause these adult changes through active participation of Cyp1b1 in the fetal liver development that imprints adult liver regulation. Cre-targeting of Floxed Cyp1b1 will be activated through a tamoxifen-dependent promoter at selected times during development, in order to test whether this early expression contributes to the general deletion effects. Metabolomic studies using 2D-NMR and mass spectrometry analyses on, respectively, liver and serum extracts will focus on establishing that Cyp1b1 deletion increases mitochondrial fatty acid oxidation and glycogen synthesis, while lowering oxidative stress. The roles of PPAR? and PPAR? loss in these liver gene changes of Cyp1b1-ko mice will be tested by comparisons to effects of deleting these PPAR genes in mouse liver. Serum markers applicable to clinical studies will be used in probing these liver changes. PUBLIC HEALTH RELEVANCE: Loss of Cytochrome P450 1B1 (CYP1B1) in humans is linked to Glaucoma and Liver tumors. CYP1B1 variants are common in humans. We find that CYP1B1 losses can counter obesity and improve insulin sensitivity. These studies address how CYP1B1 deletion remarkably increases liver fat oxidation and glycogen synthesis through suppression of PPAR?activity. The pathway offers therapeutic possibilities, including through dietary compounds that bind to CYP1B1.