Dissecting mechanisms by which GI surgery delays diabetes onset in UCD-T2DM rats

描述（由申请人提供）：随着2型糖尿病（T2DM）患病率的增加，迫切需要新的糖尿病预防策略。我们开发了一种新的T2DM大鼠模型，UCD-T2DM大鼠，它比其他可用的啮齿动物模型更准确地模拟了人类T2DM的病理生理。通过这个大鼠模型，我们已经证明回肠介入（IT）和垂直袖胃切除术（VSG）可以将糖尿病的发病延迟4-6个月（相当于人类寿命的10-15年）。与人类临床研究类似，这种发病延迟与餐后GLP-1分泌和循环胆汁酸增加有关。此外，vsg操作的UCD-T2DM大鼠循环胃饥饿素明显降低。所有这3种术后变化（GLP-1、胆胆酸和胃饥饿素）都被认为在减肥手术后葡萄糖稳态的改善中发挥作用，然而，这些变化是否与任何或全部因果关系尚未得到证实。评估每一种机制（GLP-1、胆汁酸和胃饥饿素）对IT和VSG手术后观察到的糖脂代谢改善的贡献，是了解减肥手术后观察到的代谢改善机制的必要步骤。因此，我们提出以下具体目的：1：研究GLP-1升高、胆胆酸升高和胃饥饿素降低对VSG改善UCD-T2DM大鼠葡萄糖稳态和延缓糖尿病发病的作用的相对贡献。为此，将进行3项涉及变化的添加和消融的研究。研究1a将包括：假药、假药+西格列汀、VSG、VSG + exendin 9-39。研究1b将包括：假手术、假手术+胆酸、VSG、VSG +顶端胆盐转运蛋白抑制剂。研究1c将包括：假手术、假手术+胃饥饿素拮抗剂、VSG、VSG +胃饥饿素替代。在所有关于体内葡萄糖稳态、细胞质量、内质网应激和血浆、肝脏和肠道含量的研究中，将评估胆汁酸谱。2：探讨GLP-1和胆汁酸在IT手术改善UCD-T2DM大鼠葡萄糖稳态和延缓糖尿病发病中的相对作用。为此，将按照SA1中研究1a和研究1b的概述进行2项研究。3：验证VSG联合IT手术预防UCD-T2DM大鼠糖尿病发生的假设。为此，将研究6个体重匹配组：sham-IT、sham-VSG、sham-IT/VSG、IT、VSG、IT/VSG。这些动物将被跟踪到糖尿病发作或2岁。将评估体内葡萄糖稳态，并在手术后1.5个月取自一部分动物的组织，以评估血浆、肝脏和肠道内容物的细胞质量、内质网应激和胆汁酸分布。新的治疗靶点将通过从选定的肠道部分进行激光捕获解剖分离的肠内分泌细胞进行微阵列分析，并通过焦磷酸测序分析肠道微生物群。

DESCRIPTION (provided by applicant): With the increased prevalence of type-2 diabetes mellitus (T2DM), new strategies for diabetes prevention are urgently needed. We have developed and characterized a novel rat model of T2DM, the UCD-T2DM rat, which more accurately models the pathophysiology of T2DM in humans than other available rodent models. Using this rat model we have demonstrated that ileal interposition (IT) and vertical sleeve gastrectomy (VSG) delay the onset of diabetes by 4-6 months (equivalent to 10-15 years in a human lifespan). Similar to human clinical studies, this delay in onset is associated with increases of postprandial GLP-1 secretion and circulating bile acids. Furthermore, VSG-operated UCD-T2DM rats exhibit significant decreases of circulating ghrelin. All 3 of these post-operative changes (GLP-1, bile acids and ghrelin) have been suggested to play a role in the improvement of glucose homeostasis after bariatric surgery, however whether any or all of these changes are causally involved has not been previously demonstrated. Evaluation of the contribution of each one of these mechanisms (GLP-1, bile acids and ghrelin) to the observed improvements of glucose and lipid metabolism after IT and VSG surgery is a necessary step in understanding the mechanisms responsible for the metabolic improvements observed after bariatric surgery. Thus, we are proposing the following specific aims: 1: To investigate the relative contribution of increased GLP-1, increased bile acids and decreased ghrelin to the effect of VSG to improve glucose homeostasis and delay diabetes onset in UCD-T2DM rats. To this end, 3 studies involving addition and ablation of the change will be performed. Study 1a will include: sham, sham + sitagliptin, VSG, VSG + exendin 9-39. Study 1b will include: sham, sham + cholic acid, VSG, VSG + apical bile salt transporter inhibitor. Study 1c will include: sham, sham + ghrelin antagonist, VSG, VSG + ghrelin replacement. In all studies in vivo glucose homeostasis, ¿-cell mass, endoplasmic reticulum stress and plasma, liver and intestinal content bile acid profiles will be assessed. 2: To investigate the relative contribution of GLP-1 and bile acids in the effect of IT surgery to improve glucose homeostasis and delay diabetes onset in UCD-T2DM rats. To this end, 2 studies will be performed as outlined for Study 1a and Study 1b in SA1. 3: To test the hypothesis that VSG and IT surgery in combination will prevent the onset of diabetes in UCD-T2DM rats. To this end, 6 weight-matched groups will be studied: sham-IT, sham-VSG, sham-IT/VSG, IT, VSG, IT/VSG. The animals will be followed until diabetes onset or up to 2 years of age. In vivo glucose homeostasis will be assessed and tissues taken from a subset of animals at 1.5 months after surgery for assessment of ¿-cell mass, ER stress and bile acid profiles of plasma, liver and intestinal contents. New therapeutic targets will be pursued by performing microarray analysis of enteroendocrine cells isolated via laser capture dissection from selected gut segments and analyzing gut microbial populations by pyrosequencing.