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。鉴于至少三分之一的中风患者入院时血糖过高，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，糖尿病中风患者提供了独特的药物干预以改善中风结局的机会。缺血性发作后葡萄糖供应增加也与细胞酸中毒和自由基产生有关，这可能加剧水肿。我们实验室最近发表的初步数据表明，缺血性和糖尿病脑中的血-脑葡萄糖转运除了传统的葡萄糖载体（GLUT 1）外，还部分由钠依赖性葡萄糖协同转运蛋白（SGLT 1）进行。SGLT 1蛋白的血脑屏障激活可对脑缺血产生有害影响，因为已知SGLT 1转运2个Na+和210个水分子（每个转运的葡萄糖分子），因此具有促进血管源性和细胞性脑水肿（卒中死亡的主要原因）的倾向。我们的数据表明，SGLT 1抑制，根皮苷给药缺血后，导致减少SGLT 1底物转运通过缺血性脑和改善神经退行性病变，自由基损伤，梗死和水肿的比例。因此，我们假设缺血/再灌注（IR）和糖尿病（DM）期间的SGLT 1诱导在缺血性损伤和水肿形成中起核心作用。我们将使用IR损伤的体外和体内模型以及DM模型在三个特定目标中检验这一假设。目的1：利用体内外脑缺血和糖尿病模型阐明血脑屏障SGLT 1的功能性“转运”作用。工作假设：高糖（HG）和/或IR条件下的脑内皮细胞将增加SGLT 1介导的转运。目的2：确定在IR和HG条件下，BBB中SGLT 1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SGLT 1膜插入的控制来调节SGLT 1活性。目标3：评价SGLT 1抑制对伴和不伴DM的体内局灶性缺血后脑ECF [葡萄糖]、水肿和梗死比率、行为终点和半影区损伤的影响。工作假设：在链脲佐菌素（STZ）处理的小鼠和年龄匹配的对照组中，SGLT 1抑制将降低脑ECF [葡萄糖]并改善卒中结局。了解中风和糖尿病期间血脑屏障SGLT 1功能的改变、调节以及抑制的神经保护作用对于为根皮苷和其他SGLT 1特异性抑制剂的开发提供基础至关重要，这些抑制剂可作为治疗糖尿病和非糖尿病脑缺血的潜在神经保护策略中风患者。

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.