Mechanism of Defective Incretin Action in Beta Cells during Type 2 Diabetes Mellitus

2 型糖尿病期间 β 细胞中肠促胰岛素功能缺陷的机制

• 批准号: 10313849
• 负责人: Mehboob A Hussain
• 金额: $ 48.35万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-01 至 2026-05-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10313849
• 关键词: ADRBK1 gene; Acetylcholine; Affect; Alpha Cell; Anti-Inflammatory Agents; Beta Cell; Binding; Biochemical; Blood Circulation; Cell physiology; Cells; Chemosensitization; Chronic; Coupled; Cyclic AMP; Diabetes Mellitus; Electrophysiology (science); Endocrine; Event; Exocytosis; Functional disorder; G-Protein-Coupled Receptors; GLP-I receptor; GTP-Binding Protein alpha Subunits, Gs; GTP-Binding Proteins; Gastric Inhibitory Polypeptide; Gene Expression; Gene Expression Profile; Genetic Transcription; Glucose; Glycerol; Hormones; Human; In Vitro; Inflammation; Inflammatory; Ingestion; Inositol; Insulin; Interleukin-1; Intestines; Islet Cell; Islets of Langerhans; Killer Cells; L Cells; Lead; Ligands; Link; Mediating; Metabolism; Molecular; Mus; Necrosis; Neurotransmitters; Nicotinic Receptors; Non-Insulin-Dependent Diabetes Mellitus; Nutrient; Obesity; Outcome; Pathway interactions; Patients; Peptide Receptor; Peripheral; Pharmacology; Phosphotransferases; Physiological; Proinsulin; Property; Receptor Signaling; Regulation; Resistance; Role; Serine; Signal Pathway; Signal Transduction; Source; Stimulus; Structure of beta Cell of islet; System; TNF gene; TNFRSF1A gene; Tissues; alpha-bungarotoxin receptor; base; cholinergic; cytokine; diet-induced obesity; gastric inhibitory polypeptide receptor; glucagon-like peptide 1; glucose receptor; glycemic control; improved; in vivo; incretin hormone; insight; insulin secretion; islet; macrophage; mouse model; novel; receptor; recruit; response; translational impact; tripolyphosphate; tumor; ADRBK1 gene; Acetylcholine; Affect; Alpha Cell; Anti-Inflammatory Agents; Beta Cell; Binding; Biochemical; Blood Circulation; Cell physiology; Cells; Chemosensitization; Chronic; Coupled; Cyclic AMP; Diabetes Mellitus; Electrophysiology (science); Endocrine; Event; Exocytosis; Functional disorder; G-Protein-Coupled Receptors; GLP-I receptor; GTP-Binding Protein alpha Subunits, Gs; GTP-Binding Proteins; Gastric Inhibitory Polypeptide; Gene Expression; Gene Expression Profile; Genetic Transcription; Glucose; Glycerol; Hormones; Human; In Vitro; Inflammation; Inflammatory; Ingestion; Inositol; Insulin; Interleukin-1; Intestines; Islet Cell; Islets of Langerhans; Killer Cells; L Cells; Lead; Ligands; Link; Mediating; Metabolism; Molecular; Mus; Necrosis; Neurotransmitters; Nicotinic Receptors; Non-Insulin-Dependent Diabetes Mellitus; Nutrient; Obesity; Outcome; Pathway interactions; Patients; Peptide Receptor; Peripheral; Pharmacology; Phosphotransferases; Physiological; Proinsulin; Property; Receptor Signaling; Regulation; Resistance; Role; Serine; Signal Pathway; Signal Transduction; Source; Stimulus; Structure of beta Cell of islet; System; TNF gene; TNFRSF1A gene; Tissues; alpha-bungarotoxin receptor; base; cholinergic; cytokine; diet-induced obesity; gastric inhibitory polypeptide receptor; glucagon-like peptide 1; glucose receptor; glycemic control; improved; in vivo; incretin hormone; insight; insulin secretion; islet; macrophage; mouse model; novel; receptor; recruit; response; translational impact; tripolyphosphate; tumor

PROJECT SUMMARY/ABSTRACT The incretin-mediated potentiation of glucose-stimulated insulin secretion (GSIS) accounts for 50% of postprandial insulin secretion and is essential for physiologic glycemic regulation. Upon nutrient stimulus, the two principal incretin hormones glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide-1 (GLP-1) are secreted, respectively, from intestinal endocrine K- and L-cells and reach β-cells via the circulation, where they bind their receptors, GIP receptor (GIPR) and GLP-1 receptor (GLP-1R) to amplify GSIS. While circulating incretin hormone levels are not impacted by T2DM, incretin effects on β-cell GSIS are significantly diminished in T2DM patients. However, the precise mechanisms underlying diabetes-associated blunting of incretin signaling in β-cells remain unclear. In T2DM, pharmacologic means to increase circulating GLP-1 levels improves GSIS and glycemic control. In contrast, the GIP-mediated incretin effect is notably absent in T2DM; and pharmacologic means to increase circulating GIP concentrations is not met with any GSIS improvement. The molecular mechanisms underlying diminished response to GLP-1 and absent response to GIP in T2DM remain poorly understood. T2DM is in part linked to a chronic inflammatory state with increased levels of local and circulating inflammatory cytokines that negatively impact insulin action in peripheral tissues and negatively impact the endocrine pancreas. We have therefore examined the role of pro-inflammatory cytokines that are elevated in T2DM on incretin signaling in islet -cells. Conversely, we have also interrogated the anti-inflammatory cholinergic signaling system through nicotinic acetylcholine receptors (nAchR) in modulating incretin signaling. Based on our preliminary studies, we hypothesize that TNFα - signaling through its receptor TNFR1 on β- cells - activates the Ser/Thr G-protein receptor kinase 2 (GKR2) in a non-canonical manner to suppress Gαs- activation and cAMP synthesis by ligand activated GIPR and by GLP-1R. Thus, our findings establish a mechanistic link between inflammatory cytokines in T2DM with diminished incretin signaling in β-cells. Our preliminary studies also indicate that in a murine model of T2DM, stimulating the α7 nicotinic acetylcholine receptor (α7-nAchR) reactivates GIPR signaling in β-cells to potentiate GSIS and improve glycemia. Our mechanistic studies indicate that α7-nAchR signaling phosphorylates (TNFα-activated) GRK2 at serine 670 to counteract its inhibitory effects on GIPR and GLP-1R-mediated cAMP synthesis. We now seek to expand our novel and exciting findings specifically a) to understand the role of TNFR1- GRK2-mediated signaling on in vivo β-cell function, on GIP and GLP-1R action as well as how TNFR1 signaling modulates α-cell gene expression in the context of obesity and T2DM; b) to specifically understand the role of GRK2 in mediating resistance to β-cell incretin action in T2DM; and c) to understand the beneficial role of anti- inflammatory α7-nAchR signaling in β-cells in the context of T2DM. We will use complementary in vivo and in vitro approaches to elucidate these important signaling pathways in β-cells using newly generated unique mouse models as well as in vitro in human islets and β-cells. The outcomes of our studies will yield important insights into how inflammatory cytokines of T2DM impact incretin signaling and β-cell function. Our proposed studies will also provide new insights into the effects of nicotinic acetylcholine signaling in β-cells. Finally, our studies identify potentially new receptor targets with the potential to ameliorate β-cell dysfunction in T2DM. .

项目摘要/摘要 肠降直染素介导的葡萄糖刺激的胰岛素分泌（GSIS）的增强占50％的占50％ 餐后胰岛素分泌，对于生理血糖调节至关重要。在营养刺激下， 两种主要的肠降直直射肌肌葡萄糖依赖性胰岛素肽（GIP）和胰高血糖素样肽-1 （GLP-1）分别从肠内内分泌K和L细胞分泌，并通过循环到达β细胞， 它们结合其受体，GIP受体（GIPR）和GLP-1受体（GLP-1R）的地方以扩增GSIS。 尽管T2DM循环中升高的激素水平不受影响，但对β细胞GSI的影响不断增加 T2DM患者明显减少。但是，与糖尿病相关的确切机制 β细胞中降量蛋白信号传导的钝化尚不清楚。 在T2DM中，增加循环GLP-1水平的药理学方法可改善GSIS和血糖控制。 相反，T2DM中明显不存在GIP介导的增加效应。和药理学的方法增加 循环GIP浓度没有任何GSIS改进。分子机制 对GLP-1的响应减少，T2DM中对GIP的缺乏的理解仍然很差。 T2DM部分与慢性炎症状态有关，局部和循环水平升高 炎症性细胞因子对周围组织中的胰岛素作用产生负面影响，并对 内分泌胰腺。因此，我们已经检查了促炎性细胞因子的作用 T2DM在胰岛细胞中的增加信号传导上。相反，我们还审问了抗炎 通过烟碱乙酰胆碱受体（NACHR）调节信号增加的胆碱能信号传导系统。 根据我们的初步研究，我们假设TNFα通过其受体TNFR1信号传导在β-上 细胞 - 以非典型的方式激活Ser/Thr G蛋白受体激酶2（GKR2），以抑制GαS- 配体激活GIPR和GLP-1R的激活和cAMP合成。那，我们的发现建立了一个 T2DM中炎症细胞因子之间的机械联系，β细胞中升高的信号降低。 我们的初步研究还表明，在T2DM的鼠模型中，刺激了α7烟碱 乙酰胆碱受体（α7-NACHR）重新激活β细胞中的GIPR信号传导，并改善 血糖。我们的机械研究表明，α7-NACHR信号传导磷酸化（TNFα激活）GRK2 AT 丝氨酸670可以抵消其对GIPR和GLP-1R介导的CAMP合成的抑制作用。 现在，我们寻求扩大我们的小说和令人兴奋的发现a）了解TNFR1-的作用 GRK2介导的体内β细胞功能上的信号传导，GIP和GLP-1R作用以及TNFR1信号传导的方式 在肥胖和T2DM的背景下调节α细胞基因表达； b）特别了解 GRK2在介导对T2DM中β细胞增加作用的抗性中； c）了解反 - 在T2DM的背景下，β细胞中的炎症α7-NACHR信号传导。 我们将使用体内和体外方法来阐明这些重要的信号通路 在β细胞中，使用新生成的独特小鼠模型以及人类胰岛和β细胞的体外。 我们研究的结果将对T2DM炎症细胞因子的影响产生重要的见解 泌尿素信号传导和β细胞功能。我们提出的研究还将提供有关对的新见解 β细胞中的烟碱乙酰胆碱信号传导。最后，我们的研究确定了潜在的新受体目标 在T2DM中改善β细胞功能障碍的潜力。 。