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Role of ATP-binding cassette transporter A1 in suppressing lipid accumulation by glucagon-like peptide-1 agonist in hepatocytes.
Molecular Metabolism ( IF 7.0 ) Pub Date : 2020-01-07 , DOI: 10.1016/j.molmet.2019.12.015
Jingya Lyu 1 , Hitomi Imachi 2 , Kensaku Fukunaga 2 , Seisuke Sato 2 , Toshihiro Kobayashi 2 , Tao Dong 2 , Takanobu Saheki 2 , Mari Matsumoto 2 , Hisakazu Iwama 3 , Huanxiang Zhang 4 , Koji Murao 2
Affiliation  

Objective

Adenosine triphosphate (ATP)-binding cassette transporter A1 (ABCA1) influences hepatic cholesterol transportation. Accumulation of hepatic cholesterol leads to fatty liver disease, which is improved by glucagon-like peptide 1 (GLP-1) in diabetes. Therefore, we analyzed the molecular mechanism in the regulation of hepatic ABCA1 by GLP-1 analogue exendin-4.

Methods

Hepatic ABCA1 expression and transcription were checked by western blotting, real-time polymerase chain reaction (PCR), and luciferase assay in HepG2 cells. Chromatin immunoprecipitation (ChIP) and site-directed mutagenesis were employed to determine transcriptional regulation of the ABCA1 gene. Prolactin regulatory element-binding (PREB)-transgenic mice were generated to access the effect of exendin-4 on improving lipid accumulation caused by a high-fat diet (HFD).

Results

Exendin-4 stimulated hepatic ABCA1 expression and transcription via the Ca2+/calmodulin (CaM)-dependent protein kinase kinase/CaM-dependent protein kinase IV (CaMKK/CaMKIV) pathway, whereas GLP-1 receptor antagonist exendin9-39 cancelled this effect. Therefore, exendin-4 decreased hepatic lipid content. ChIP showed that PREB could directly bind to the ABCA1 promoter, which was enhanced by exendin-4. Moreover, PREB stimulated ABCA1 promoter activity, and mutation of PREB-binding site in ABCA1 promoter cancelled exendin-4-enhanced ABCA1 promoter activity. Silencing of PREB attenuated the effect of exendin-4 and induced hepatic cholesterol accumulation. Blockade of CaMKK by STO-609 or siRNA cancelled the upregulation of ABCA1 and PREB induced by exendin-4. In vivo, exendin-4 or overexpression of PREB increased hepatic ABCA1 expression and decreased hepatic lipid accumulation and high plasma cholesterol caused by a HFD.

Conclusions

Our data shows that exendin-4 stimulates hepatic ABCA1 expression and decreases lipid accumulation by the CaMKK/CaMKIV/PREB pathway, suggesting that ABCA1 and PREB might be the therapeutic targets in fatty liver disease.



中文翻译:

ATP结合盒转运蛋白A1在胰高血糖素样肽1激动剂在肝细胞中抑制脂质蓄积中的作用。

目的

结合三磷酸腺苷(ATP)的盒式转运蛋白A1(ABCA1)影响肝胆固醇的转运。肝胆固醇的积累导致脂肪肝疾病,在糖尿病患者中,胰高血糖素样肽1(GLP-1)可以改善脂肪肝疾病。因此,我们分析了GLP-1类似物exendin-4调节肝ABCA1的分子机制。

方法

通过Western印迹,实时聚合酶链反应(PCR)和萤光素酶测定法检测HepG2细胞中肝ABCA1的表达和转录。染色质免疫沉淀(ChIP)和定点诱变被用来确定ABCA1基因的转录调控。生成催乳素调节元件结合(PREB)转基因小鼠,以获取exendin-4对改善高脂饮食(HFD)引起的脂质蓄积的作用。

结果

Exendin-4 stimulated hepatic ABCA1 expression and transcription via the Ca2+/calmodulin (CaM)-dependent protein kinase kinase/CaM-dependent protein kinase IV (CaMKK/CaMKIV) pathway, whereas GLP-1 receptor antagonist exendin9-39 cancelled this effect. Therefore, exendin-4 decreased hepatic lipid content. ChIP showed that PREB could directly bind to the ABCA1 promoter, which was enhanced by exendin-4. Moreover, PREB stimulated ABCA1 promoter activity, and mutation of PREB-binding site in ABCA1 promoter cancelled exendin-4-enhanced ABCA1 promoter activity. Silencing of PREB attenuated the effect of exendin-4 and induced hepatic cholesterol accumulation. Blockade of CaMKK by STO-609 or siRNA cancelled the upregulation of ABCA1 and PREB induced by exendin-4. In vivo,exendin-4或PREB的过表达增加了由HFD引起的肝ABCA1表达,并减少了肝脂质蓄积和高血浆胆固醇。

结论

我们的数据显示,exendin-4通过CaMKK / CaMKIV / PREB途径刺激肝ABCA1表达并减少脂质蓄积,表明ABCA1和PREB可能是脂肪肝疾病的治疗靶标。

更新日期:2020-01-07
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