Increased sodium dependent glucose transport in the ischemic brain

描述（由申请人提供）：中风是美国第三大死亡和残疾原因。考虑到至少三分之一的中风患者在入院时患有高血糖，其中大多数是糖尿病患者，65%的糖尿病患者死于某种形式的心脏病或中风，糖尿病中风患者为改善中风预后提供了独特的药物干预机会。缺血发作后葡萄糖供应的增加也与细胞酸中毒和自由基的产生有关，这可以加剧水肿。我们实验室最近发表的和初步的数据表明，在缺血和糖尿病大脑中，除了传统的葡萄糖载体（GLUT1）外，血-脑葡萄糖运输部分由钠依赖性葡萄糖共转运蛋白（SGLT1）携带。血脑屏障激活SGLT1蛋白可能对脑缺血产生有害影响，因为已知SGLT1每转运一个葡萄糖分子就转运2Na+和210个水分子，因此有可能导致血管源性和细胞性脑水肿，这是中风死亡的主要原因。我们的数据表明，抑制SGLT1，在缺血后给药，导致SGLT1底物在缺血脑中的转运减少，并改善神经变性、自由基损伤、梗死和水肿比率。因此，我们假设SGLT1在缺血/再灌注（IR）和糖尿病（DM）期间的诱导在缺血性损伤和水肿形成中起核心作用。我们将通过体外和体内IR损伤模型以及糖尿病模型来验证这一假设。目的1：通过体外和体内脑缺血和糖尿病模型阐明血脑屏障SGLT1的功能性“运输”作用。工作假设：脑内皮细胞受到高糖（HG）和/或IR会增加SGLT1介导的运输。目的2：确定IR和HG条件下血脑屏障处SGLT1活性的调节机制。工作假设：HG和IR条件将通过Na的可用性和PKC对SGLT1膜插入的控制来调节SGLT1活性。目的3：评估SGLT1抑制对伴有和不伴有糖尿病的体内局灶性缺血后脑ECF[葡萄糖]、水肿和梗死比率、行为终点和半脑损伤的影响。工作假设：SGLT1抑制会降低链脲佐菌素（STZ）治疗小鼠和年龄匹配对照组的脑ECF[葡萄糖]并改善卒中结局。了解脑卒中和糖尿病期间血脑屏障SGLT1功能的改变、调节和抑制的神经保护作用是至关重要的，为开发phenlorizin和其他SGLT1特异性抑制剂作为治疗糖尿病和非糖尿病脑卒中患者脑缺血的潜在神经保护策略提供基础。

DESCRIPTION (provided by applicant): Stroke is the third leading cause of death and disability in USA. Given that at least one third of stroke patients are hyperglycemic on admission, with most being diabetic, and 65 percent of diabetic patients die from some form of heart disease or stroke, the diabetic stroke patient provides opportunity for unique pharmacologic interventions to improve stroke outcome. Increased glucose supply post ischemic attack has also been associated with cellular acidosis and free radical generation which can exacerbate edema. Recent published and preliminary data from our lab suggest that blood-to-brain glucose transport in both the ischemic and diabetic brain is partially carried by the sodium dependent glucose cotransporter (SGLT1) in addition to the traditional glucose carrier (GLUT1). Blood-brain barrier activation of SGLT1 protein can have deleterious effects in brain ischemia since SGLT1 is known to transport 2Na+ and 210 water molecules for each glucose molecule transported, thus having the propensity to contribute to both vasogenic and cellular brain edema, a leading cause of stroke death. Our data suggests that SGLT1 inhibition, with phlorizin administration post ischemia, resulted in reduced SGLT1 substrate transport across the ischemic brain and improved neurodegeneration, free radical damage, and infarction and edema ratios. Thus we hypothesize that SGLT1 induction during ischemia/reperfusion (IR) and diabetes mellitus (DM) plays a central role in ischemic damage and edema formation. We will test this hypothesis in three specific aims using both in vitro and in vivo models of IR injury and a model of DM. AIM 1: Elucidate the functional "transport" role of BBB SGLT1 using in vitro and in vivo models of brain ischemia and DM. Working Hypothesis: Brain endothelial cells subjected to high glucose (HG) and/or IR will increase SGLT1 mediated transport. AIM 2: Determine the regulatory mechanisms for SGLT1 activity at the BBB during conditions of both IR and HG. Working Hypothesis: Conditions of HG and IR will regulate SGLT1 activity by availability of Na and PKC control of SGLT1 membrane insertion. AIM 3: Evaluate the effects of SGLT1 inhibition on brain ECF [glucose], edema and infarction ratios, behavioral endpoints, and penumbral injury after in vivo focal ischemia with and without DM. Working Hypothesis: SGLT1 inhibition will decrease brain ECF [glucose] and improve stroke outcome in streptozotocin (STZ) treated mice and age matched controls. An understanding of altered blood-brain barrier SGLT1 function, regulation and neuroprotective effects of inhibition during stroke and DM is vital to provide a foundation for the development of phlorizin and other SGLT1 specific inhibitors as potential neuroprotective strategies to treat brain ischemia in both diabetic and non-diabetic stroke patients.