Increased sodium dependent glucose transport in the ischemic brain

描述(申请人提供)：中风是美国第三大致死和致残原因。鉴于至少三分之一的中风患者入院时患有高血糖，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。脑缺血发作后葡萄糖供应增加也与细胞酸化和自由基产生有关，这可能会加剧浮肿。最近发表的和我们实验室的初步数据表明，在缺血和糖尿病脑中，血到脑的葡萄糖转运除了传统的葡萄糖载体(GLUT1)外，还部分由钠依赖的葡萄糖共转运体(SGLT1)携带。SGLT1蛋白的血脑屏障激活可能在脑缺血中产生有害影响，因为已知SGLT1为每个转运的葡萄糖分子运输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，这是导致中风死亡的主要原因。我们的数据表明，抑制SGLT1，在缺血后给予连翘苷，导致SGLT1底物通过缺血脑的转运减少，并改善神经变性、自由基损伤以及脑梗塞和水肿率。因此，我们推测SGLT1在缺血/再灌注(IR)和糖尿病(DM)过程中的诱导在缺血损伤和水肿形成中起中心作用。我们将使用IR损伤的体外和体内模型以及DM的模型在三个特定的目标上检验这一假设。目的1：利用体外和体内脑缺血和糖尿病模型，阐明血脑屏障SGLT1的功能“转运”作用。工作假设：高糖(HG)和/或IR作用下的脑内皮细胞将增加SGLT1介导的转运。目的2：确定IR和HG条件下血脑屏障SGLT1活性的调节机制。工作假说：HG和IR的条件将通过钠的有效性和PKC对SGLT1膜插入的控制来调节SGLT1的活性。目的：研究SGLT1抑制对糖尿病大鼠脑缺血后脑内ECF[葡萄糖]、脑水肿和脑梗死率、行为学终点和半暗带损伤的影响。工作假设：在链脲佐菌素(STZ)治疗的小鼠和年龄匹配的对照组中，抑制SGLT1将降低脑ECF[葡萄糖]并改善中风结果。了解卒中和糖尿病时血脑屏障SGLT1的功能、调节和抑制的神经保护作用，对于开发根茎苷和其他SGLT1特异性抑制剂作为治疗糖尿病和非糖尿病卒中患者脑缺血的潜在神经保护策略是至关重要的。

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.