摘要
Objective
Carbohydrate-response element-binding protein (ChREBP) is the major transcription factor conferring glucose-induced gene expression in pancreatic islets, liver and adipose tissue. Recently, a novel ChREBP isoform, ChREBP-β, was identified in adipose tissue and found to be also expressed in islets and involved in glucose-induced beta cell proliferation. However, the physiological function of this less abundant β-isoform in the islet, and in diabetes, is largely unknown. The aims of the present study, therefore, were to determine how diabetes affects ChREBP-β and elucidate its physiological role in pancreatic beta cells. Methods
Non-obese diabetic and obese, diabetic ob/ob mice were used as models of T1D and T2D and human islets and the rat INS-1 beta cell line were exposed to low/high glucose and used for ChREBP isoform-specific gain-and-loss-of-function experiments. Changes in ChREBP-β and ChREBP-α were assessed by qRT-PCR, immunoblotting, promoter luciferase, and chromatin immunoprecipitation studies. Results
Expression of the ChREBP-β isoform was highly induced in diabetes and by glucose, whereas ChREBP-α was downregulated. Interestingly, ChREBP-β gain-of-function experiments further revealed that it was ChREBP-β that downregulated ChREBP-α through a negative feedback loop. On the other hand, ChREBP-β knockdown led to unabated ChREBP-α activity and glucose-induced expression of target genes, suggesting that one of the physiological roles of this novel β-isoform is to help keep glucose-induced and ChREBP-α-mediated gene expression under control. Conclusions
We have identified a previously unappreciated negative feedback loop by which glucose-induced ChREBP-β downregulates ChREBP-α-signaling providing new insight into the physiological role of islet ChREBP-β and into the regulation of glucose-induced gene expression.
摘要译文
目的糖链反应元件结合蛋白（ChREBP）是胰岛，肝脏和脂肪组织中赋予葡萄糖诱导的基因表达的主要转录因子。最近，在脂肪组织中鉴定出新的ChREBP同种型ChREBP-β，发现其也在胰岛中表达并参与葡萄糖诱导的β细胞增殖。然而，这种不太丰富的β亚型在胰岛和糖尿病中的生理功能在很大程度上是未知的。因此，本研究的目的，确定糖尿病如何影响ChREBP-β并阐明其在胰腺β细胞中的生理学作用。方法非肥胖糖尿病和肥胖，ob小鼠作为T1D和T2D和人胰岛的模型，将大鼠INS-1β细胞系暴露于低/高葡萄糖，并用于ChREBP异构体特异性增益和功能丧失实验。通过qRT-PCR，免疫印迹，启动子荧光素酶和染色质免疫沉淀研究来评估ChREBP-β和ChREBP-α的变化。结果ChREBP-β异构体的表达在糖尿病和葡萄糖中被高度诱导，而ChREBP-α被下调。有趣的是，ChREBP-β功能增益实验进一步揭示ChREBP-β通过负反馈循环下调ChREBP-α。另一方面，ChREBP-β敲低导致ChREBP-α活性和葡萄糖诱导的靶基因的表达，这表明这种新型β-亚型的生理作用之一是有助于保持葡萄糖诱导的和ChREBP-α介导的基因表达处于控制之下。k循环，葡萄糖诱导的ChREBP-β下调ChREBP-α信号，为胰岛ChREBP-β的生理学作用和葡萄糖诱导的基因表达的调节提供新的见解。
Gu Jing; Junqin Chen; Guanlan Xu; Anath Shalev. Islet ChREBP-β is increased in diabetes and controls ChREBP-α and glucose-induced gene expression via a negative feedback loop[J]. Molecular Metabolism, 2016,5(12): 1208–1215