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GHS-R 介导的胰岛葡萄糖刺激胰岛素分泌的机制研究。

Mechanistic Investigation of GHS-R Mediated Glucose-Stimulated Insulin Secretion in Pancreatic Islets.

机构信息

USDA/ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA.

Interdepartmental Program in Translational Biology and Molecular Medicine, Baylor College of Medicine, Houston, TX 77030, USA.

出版信息

Biomolecules. 2022 Mar 6;12(3):407. doi: 10.3390/biom12030407.

Abstract

Ghrelin receptor, a growth hormone secretagogue receptor (GHS-R), is expressed in the pancreas. Emerging evidence indicates that GHS-R is involved in the regulation of glucose-stimulated insulin secretion (GSIS), but the mechanism by which GHS-R regulates GSIS in the pancreas is unclear. In this study, we investigated the role of GHS-R on GSIS in detail using global mice (in vivo) and -ablated pancreatic islets (ex vivo). GSIS was attenuated in both mice and -ablated islets, while the islet morphology was similar between WT and mice. To elucidate the mechanism underpinning -mediated GSIS, we investigated the key steps of the GSIS signaling cascade. The gene expression of glucose transporter 2 () and the glucose-metabolic intermediate-glucose-6-phosphate (G6P) were reduced in -ablated islets, supporting decreased glucose uptake. There was no difference in mitochondrial DNA content in the islets of WT and mice, but the ATP/ADP ratio in islets was significantly lower than that of WT islets. Moreover, the expression of pancreatic and duodenal homeobox 1 (Pdx1), as well as insulin signaling genes of insulin receptor (IR) and insulin receptor substrates 1 and 2 (IRS1/IRS2), was downregulated in islets. Akt is the key mediator of the insulin signaling cascade. Concurrently, Akt phosphorylation was reduced in the pancreas of mice under both insulin-stimulated and homeostatic conditions. These findings demonstrate that GHS-R ablation affects key components of the insulin signaling pathway in the pancreas, suggesting the existence of a cross-talk between GHS-R and the insulin signaling pathway in pancreatic islets, and GHS-R likely regulates GSIS via the Akt-Pdx1-GLUT2 pathway.

摘要

生长激素促分泌素受体(GHS-R)是一种胃饥饿素受体,在胰腺中表达。新出现的证据表明,GHS-R 参与了葡萄糖刺激的胰岛素分泌(GSIS)的调节,但 GHS-R 调节胰腺中 GSIS 的机制尚不清楚。在这项研究中,我们使用全身性 GHS-R 基因敲除(KO)小鼠(体内)和 GHS-R 基因敲除胰岛(离体)详细研究了 GHS-R 在 GSIS 中的作用。在 GHS-R KO 小鼠和 GHS-R 基因敲除胰岛中,GSIS 均减弱,而 WT 和 GHS-R KO 小鼠的胰岛形态相似。为了阐明 GHS-R 介导的 GSIS 的机制,我们研究了 GSIS 信号级联的关键步骤。葡萄糖转运蛋白 2()和葡萄糖代谢中间物-葡萄糖-6-磷酸(G6P)的基因表达在 GHS-R 基因敲除胰岛中减少,支持葡萄糖摄取减少。WT 和 GHS-R KO 小鼠胰岛中的线粒体 DNA 含量没有差异,但 GHS-R KO 胰岛中的 ATP/ADP 比值明显低于 WT 胰岛。此外,胰岛中胰腺十二指肠同源盒 1(Pdx1)以及胰岛素受体(IR)和胰岛素受体底物 1 和 2(IRS1/IRS2)的胰岛素信号基因的表达在 GHS-R KO 胰岛中下调。Akt 是胰岛素信号级联的关键介质。同时,在胰岛素刺激和稳态条件下,GHS-R KO 小鼠胰腺中的 Akt 磷酸化减少。这些发现表明,GHS-R 缺失会影响胰腺中胰岛素信号通路的关键组成部分,提示 GHS-R 和胰腺胰岛中的胰岛素信号通路之间存在交叉对话,并且 GHS-R 可能通过 Akt-Pdx1-GLUT2 途径调节 GSIS。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/585e/8945998/b21776def995/biomolecules-12-00407-g001.jpg

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