Regulation and functional relevance of GLP-2 in sepsis

全身感染和脓毒症是危重病患者常见的并发症。在许多情况下，没有发现感染病灶，这表明生理微生物区系在应激生物体中充当感染源。危重病损害肠道屏障功能，并允许微生物易位到有机体。改善肠道屏障功能可能为预防危重患者的细菌移位和通过封闭细菌进入部位来减少感染负担提供有价值的策略。在本研究中，我们旨在评价GLP-2作为从肠道和胰腺释放的前胰高血糖素原裂解产物的调节和机制相关性，以改善炎症条件下的肠道屏障功能。在初步结果中，我们证明了重症患者的GLP-2水平显著升高，而GLP-2在小鼠中以IL 6依赖性方式响应于炎症刺激而增加。使用组织特异性前胰高血糖素原表达小鼠，我们发现炎性GLP-2分泌来源于胰腺而不是肠道。在功能上，GLP-2的应用强烈地改变了结肠结扎穿刺（CLP）或内毒素诱导的脓毒症激发的小鼠的炎症反应，而在前胰高血糖素原敲除小鼠中缺乏GLP-2则导致相反的结果。 本提案旨在阐明内源性GLP-2分泌与脓毒症炎症反应和结局的相关性。在第一步中，我们将通过使用前胰高血糖素原报告小鼠来表征导致小鼠中内毒素依赖性GLP-2分泌的炎症级联反应（目的1）。然后，我们将通过使用功能获得和丧失模型来研究GLP-2在鼠脓毒症中的抗炎能力（目的2），研究胰腺与肠GLP-2产生的相关性（目的3），并研究IL 6作为鼠脓毒症中的GLP-2诱导刺激的功能相关性（目的4）。

Systemic infection and sepsis are frequent complications of critical ill patients. In many cases no infectious focus can be found, suggesting the physiological microflora to act as an infectious source in the stressed organism. Critical illness impairs intestinal barrier function and allows translocation of microorganisms to the organism. Improvement of gut barrier function might provide a valuable strategy to prevent bacterial translocation of critical ill patients and to reduce infectious burden by sealing bacterial entry sites. In this study we are aiming to evaluate the regulation and mechanistic relevance of GLP-2 as a preproglucagon cleavage product released from the gut and the pancreas to improve gut barrier function under inflammatory conditions. In preliminary results we demonstrate marked elevation of GLP-2 levels in critical ill patients, while GLP-2 was increased in response to inflammatory stimuli in an IL6 dependent manner in mice. Using tissue specific preproglucagon expressing mice we found inflammatory GLP-2 secretion to originate from the pancreas but not from the gut. Functionally, GLP-2 application strongly modified the inflammatory response of mice challenged by colon ligation puncture (CLP) or endotoxin induced sepsis, while absence of GLP-2 in preproglucagon knockout mice caused the opposite. It is the aim of this proposal to characterise the relevance of endogenous GLP-2 secretion for inflammatory response and outcome in sepsis. In the first step we will characterize the inflammatory cascade leading to endotoxin dependent GLP-2 secretion in mice by employing preproglucagon reporter mice (Aim 1). We will then study the anti-inflammatory capacities of GLP-2 in murine sepsis by use of gain and loss of function models (Aim 2), investigate the relevance of pancreatic vs. intestinal GLP-2 production (Aim 3) and study the functional relevance of IL6 as a GLP-2 inducing stimulus in murine sepsis (Aim 4).