Identification of functional estrogen response elements in glycerol channel Aquaporin-7 gene

Abstract

Objective: We previously reported that tissue-specific effects of estrogen on Aquaporin-7 (AQP7) expression are associated with the development of menopausal obesity. The current study was designed to identify the estrogen response elements (EREs) in the promoter of Aqp7 and investigate the role of AQP7 in the regulation of estrogen-induced anti-adipogenesis.

Methods: We measured AQP7 expression and intracellular fat accumulation in 3T3-L1 adipocytes either silenced with shRNA or treated with estrogen receptor (ER)-specific antagonists or agonists before exposure to estrogen. EREs were predicted by Bioinformatics, assessed by chromatin immunoprecipitation, and verified by luciferase reporter assay.

Results: We found that regulation of AQP7 expression was mainly via ERα, as confirmed by the use of ER selective antagonists and agonists. In addition, the induction of AQP7 expression by estrogen was linked to ER binding with two EREs in the promoter region of Aqp7. Furthermore, we found that the regulation of adipogenesis by 17β-estradiol was AQP7 dependent, as evidenced by the increase in fat accumulation after silencing AQP7.

Conclusions: Estrogen induces AQP7 expression by binding EREs in the promoter of the Aqp7 gene, resulting in fat catabolism of adipocyte. These results provide new insights into the molecular mechanisms underpinning the anti-adipogenic effect of estrogen.

Chinese abstract

目的：我们曾报道雌激素对水通道蛋白-7（AQP7）表达的组织特异性作用与绝经期肥胖的发展有关。此研究旨在鉴定Aqp7启动子中的雌激素反应元件（EREs）, 并研究AQP7在调节雌激素诱导的抗脂肪形成中的作用。

方法：我们测量了3T3-L1脂肪细胞中的AQP7表达和细胞内脂肪积累, 用shRNA沉默或用雌激素受体（ER）特异性拮抗剂或激动剂处理, 然后暴露于雌激素。通过生物信息学预测ERE, 通过染色质免疫沉淀评估, 并通过荧光素酶报告基因测定验证。

结果：我们发现AQP7表达的调节主要通过ERα, 如通过采用ER选择性拮抗剂和激动剂所证实的。此外, 雌激素对AQP7表达的诱导与ER与Aqp7启动子区域中两个ERE的结合有关。此外, 我们发现17β-雌二醇对脂肪生成的调节依赖于AQP7, 这可通过沉默AQP7后脂肪积累的增加来证明。

结论：雌激素通过结合Aqp7基因的启动子中的ERE诱导AQP7表达, 导致脂肪细胞的脂肪分解代谢。这些结果为支持雌激素抗脂肪形成作用的分子机制提供了新的见解。

Keywords:

• Menopause
• obesity
• estrogen
• aquaglyceroporin 7
• estrogen response element
• 3T3-L1 adipocyte

Potential conflict of interest

The authors declare no conflict of interest.

Additional information

Funding

This work was supported by grants from National Natural Science Foundation of China [81200251 (J. S.)], [81601226 (X. F.)], [81701460 (X. C.)]; Natural Science Foundation of Zhejiang Province [Y17H040052 (J. S)]; Key Platform Plan for Medicine and Health of Zhejiang Province [2015ZDA003 (J. S.)]; General Research Program for Medicine and Health of Zhejiang Province [2016KYA029 (J. Z.)], [2018KY220 (B. J.)]; Excellent Young Scientist Foundation of Zhejiang Provincial People’s Hospital [ZRY2016A002 (X. C.)].