Liver X receptor (LXR) agonists have the potential to alleviate obesity related diseases, particularly atherosclerosis. However, LXRs are transcriptional regulators that induce de novo lipogenesis and lipid accumulation in hepatocytes which represents a serious adverse effect. In this work, we sought to characterize the LXR agonist GW3965 effects on fatty acid (FA) and phospholipid (PL) remodelling and the correlation with gene expression in order to better understand the underlying effects leading to hepatic pathology upon LXR activation. Human primary hepatocytes treated for 48 h with GW3965 were analysed for changes in lipid metabolism gene expression by qPCR, variations in the FA profile was evaluated by GC-FID and in PL profiles using thin layer chromatography, ESI-MS and MS/MS analysis. Changes in cell membrane biochemical properties were studied using bilayer models generated with CHARMM-GUI. ELOLV6 and SCD1 mRNA increase was consistent with higher C16:1 and C18:1n9 at the expense of C16:0 and C18:0. The reduction of C18:2n6 and increase in C20:2n6 was in agreement with ELOVL5 upregulation. Phosphatydilethanolamine (PE) levels tended to decrease and phosphatidylinositol to increase; although differences did not reach significance, they correlated with changes in AGXT2L1, CDS1 and LPIN1 mRNA levels that were increased. The overall effect of GW3965 on PEs molecular profiles was an increase of long-chain polyunsaturated FA chains and a decrease of C16/C18 saturated and monounsaturated FAs chains. Additionally, PC (32:1) and PC (34:2) were decreased, and PC (36:1) and PC (34:1) were increased. AGXT2L1 is an enzyme with strict substrate specificity for phosphoethanolamine, which is converted into ammonia in GW3965-treated hepatocytes and could explain the PE reduction. In summary, LXR activation by GW3965 targets PE biosynthesis and FA elongation/desaturation, which tends to decrease PE in relation to total PL levels, and remodelling of PC and PE molecular species. We identified the human AGXT2L1 gene as induced by LXR activation by both synthetic and endogenous agonist treatment. The increase in acetaldehyde-induced oxidative stress, and in the lipid species identified have the potential to enhance the inflammatory process and impair membrane function. Future studies should focus on inhibition of AGXT2L1 activity with the aim of reverting the steatosis induced by LXR activation.

中文翻译：

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用GW3965激活LXR后对人原代肝细胞的血脂分析确定AGXT2L1是与磷脂酰乙醇胺变化有关的主要靶标。

肝X受体（LXR）激动剂具有减轻与肥胖有关的疾病（尤其是动脉粥样硬化）的潜力。但是，LXR是转录调节因子，可诱导从头开始的脂肪生成和肝细胞脂质蓄积，这是一种严重的不良反应。在这项工作中，我们试图表征LXR激动剂GW3965对脂肪酸（FA）和磷脂（PL）重塑的作用以及与基因表达的相关性，以便更好地了解导致LXR活化的肝脏病理的潜在作用。用qPCR分析了用GW3965处理48 h的人原代肝细胞的脂质代谢基因表达变化，通过薄层色谱，ESI-MS和MS / MS分析，通过GC-FID和PL谱评估了FA谱的变化。使用CHARMM-GUI生成的双层模型研究了细胞膜生化特性的变化。ELOLV6和SCD1 mRNA的增加与更高的C16：1和C18：1n9一致，但以C16：0和C18：0为代价。C18：2n6的减少和C20：2n6的增加与ELOVL5的上调一致。磷脂酰乙醇胺（PE）含量趋于降低，磷脂酰肌醇含量升高；尽管差异没有达到显着性，但它们与AGXT2L1，CDS1和LPIN1 mRNA水平增加的变化相关。GW3965对PE分子分布的总体影响是长链多不饱和FA链增加，C16 / C18饱和和单不饱和FA链减少。此外，PC（32：1）和PC（34：2）减少，PC（36：1）和PC（34：1）增加。AGXT2L1是一种对磷乙醇胺具有严格底物特异性的酶，该酶在经过GW3965处理的肝细胞中转化为氨，可以解释PE的降低。总之，GW3965激活LXR的目标是PE的生物合成和FA延伸/去饱和，这相对于总PL含量往往会降低PE，并对PC和PE分子种类进行重塑。我们确定了人类AGXT2L1基因是由LXR激活通过合成和内源性激动剂治疗诱导的。乙醛诱导的氧化应激的增加以及所鉴定的脂质种类的增加可能会增强炎症过程并损害膜功能。未来的研究应集中在抑制AGXT2L1活性上，以恢复LXR激活引起的脂肪变性。在经过GW3965处理的肝细胞中被转化为氨，这可以解释PE的降低。总之，GW3965激活LXR的目标是PE的生物合成和FA延伸/去饱和，这相对于总PL含量往往会降低PE，并对PC和PE分子种类进行重塑。我们确定了人类AGXT2L1基因是由合成和内源性激动剂治疗的LXR激活诱导的。乙醛诱导的氧化应激的增加以及所鉴定的脂质种类的增加可能会增强炎症过程并损害膜功能。未来的研究应集中在抑制AGXT2L1活性上，以恢复LXR激活引起的脂肪变性。在经过GW3965处理的肝细胞中被转化为氨，这可以解释PE的降低。总之，GW3965激活LXR的目标是PE的生物合成和FA延伸/去饱和，这相对于总PL含量往往会降低PE，并对PC和PE分子种类进行重塑。我们确定了人类AGXT2L1基因是由LXR激活通过合成和内源性激动剂治疗诱导的。乙醛诱导的氧化应激的增加以及所鉴定的脂质种类的增加可能会增强炎症过程并损害膜功能。未来的研究应集中在抑制AGXT2L1活性上，以恢复LXR激活引起的脂肪变性。GW3965激活LXR的目标是PE的生物合成和FA延伸/去饱和，这会相对于总PL含量降低PE，并对PC和PE分子种类进行重塑。我们确定了人类AGXT2L1基因是由LXR激活通过合成和内源性激动剂治疗诱导的。乙醛诱导的氧化应激的增加以及所鉴定的脂质种类的增加可能会增强炎症过程并损害膜功能。未来的研究应集中在抑制AGXT2L1活性上，以恢复LXR激活引起的脂肪变性。GW3965激活LXR的目标是PE的生物合成和FA延伸/去饱和，这会相对于总PL含量降低PE，并对PC和PE分子种类进行重塑。我们确定了人类AGXT2L1基因是由LXR激活通过合成和内源性激动剂治疗诱导的。乙醛诱导的氧化应激的增加以及所鉴定的脂质种类的增加可能会增强炎症过程并损害膜功能。未来的研究应集中在抑制AGXT2L1活性上，以恢复LXR激活引起的脂肪变性。我们确定了人类AGXT2L1基因是由LXR激活通过合成和内源性激动剂治疗诱导的。乙醛诱导的氧化应激的增加以及所鉴定的脂质种类的增加可能会增强炎症过程并损害膜功能。未来的研究应集中在抑制AGXT2L1活性上，以恢复LXR激活引起的脂肪变性。我们确定了人类AGXT2L1基因是由合成和内源性激动剂治疗的LXR激活诱导的。乙醛诱导的氧化应激的增加以及所鉴定的脂质种类的增加可能会增强炎症过程并损害膜功能。未来的研究应集中在抑制AGXT2L1活性上，以恢复LXR激活引起的脂肪变性。