Chanda Dipanjan, Kim Sung-Jin, Lee In-Kyu, Shong Minho, Choi Hueng-Sik
Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Republic of Korea.
Am J Physiol Endocrinol Metab. 2008 Aug;295(2):E368-79. doi: 10.1152/ajpendo.00800.2007. Epub 2008 May 27.
Sodium arsenite has been demonstrated to alter the expression of genes associated with glucose homeostasis in tissues involved in the pathogenesis of type 2 diabetes; however, the underlying molecular mechanism has not been fully elucidated yet. In this study, we report that the sodium arsenite-induced gene expression of the small heterodimer partner (SHP; NR0B2), an atypical orphan nuclear receptor, regulates the expression of hepatic gluconeogenic genes. Sodium arsenite augments hepatic SHP mRNA levels in an AMP-activated protein kinase (AMPK)-dependent manner. Sodium arsenite activated AMPK and was shown to perturb cellular ATP levels. The arsenite-induced SHP mRNA level was blocked by adenoviral overexpression of dominant negative AMPK (Ad-dnAMPKalpha) or by the AMPK inhibitor compound C in hepatic cell lines. We demonstrated the dose-dependent induction of SHP mRNA levels by sodium arsenite and repressed the forskolin/dexamethasone-induced gene expression of the key hepatic gluconeogenic genes phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase). Ad-dnAMPKalpha blocked the repressive effects of arsenite-induced SHP on PEPCK and G6Pase. Sodium arsenite inhibited the promoter activity of PEPCK and G6Pase, and this repression was abolished by small interfering (si)RNA SHP treatments. The knockdown of SHP expression by oligonucleotide siRNA SHP or adenoviral siRNA SHP released the sodium arsenite-mediated repression of forskolin/dexamethasone-stimulated PEPCK and G6Pase gene expression in a variety of hepatic cell lines. Results from our study suggest that sodium arsenite induces SHP via AMPK to inhibit the expression of hepatic gluconeogenic genes and also provide us with a novel molecular mechanism of arsenite-mediated regulation of hepatic glucose homeostasis.
已证实亚砷酸钠可改变与2型糖尿病发病机制相关组织中葡萄糖稳态相关基因的表达；然而，其潜在的分子机制尚未完全阐明。在本研究中，我们报告亚砷酸钠诱导的非典型孤儿核受体小异二聚体伴侣（SHP；NR0B2）基因表达可调节肝糖异生基因的表达。亚砷酸钠以AMP激活的蛋白激酶（AMPK）依赖的方式增加肝脏SHP mRNA水平。亚砷酸钠激活AMPK，并显示会扰乱细胞ATP水平。在肝细胞系中，腺病毒过表达显性负性AMPK（Ad-dnAMPKalpha）或使用AMPK抑制剂化合物C可阻断亚砷酸钠诱导的SHP mRNA水平。我们证明了亚砷酸钠对SHP mRNA水平的剂量依赖性诱导，并抑制了福斯可林/地塞米松诱导的关键肝糖异生基因磷酸烯醇丙酮酸羧激酶（PEPCK）和葡萄糖-6-磷酸酶（G6Pase）的基因表达。Ad-dnAMPKalpha阻断了亚砷酸钠诱导的SHP对PEPCK和G6Pase的抑制作用。亚砷酸钠抑制了PEPCK和G6Pase的启动子活性，而小干扰（si）RNA SHP处理可消除这种抑制作用。通过寡核苷酸siRNA SHP或腺病毒siRNA SHP敲低SHP表达，可解除亚砷酸钠介导的对多种肝细胞系中福斯可林/地塞米松刺激的PEPCK和G6Pase基因表达的抑制。我们的研究结果表明，亚砷酸钠通过AMPK诱导SHP，以抑制肝糖异生基因的表达，同时也为我们提供了亚砷酸盐介导的肝葡萄糖稳态调节的新分子机制。
