Role of ATP-binding cassette transporter A1 in suppressing lipid accumulation by glucagon-like peptide-1 agonist in hepatocytes.,Molecular Metabolism

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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。