Hyperglycemia Aggravates Cerebral Vasospasm after Subarachnoid Hemorrhage in a Rat Model

BACKGROUND: Hyperglycemia is common and showed to be risky for poor prognosis in patients with subarachnoid hemorrhage (SAH). However, the causality and mechanism underlying this observation are not well established. OBJECTIVE: To investigate the relationship between hyperglycemia and cerebral vasospasm with its pathogenesis in a rat model of SAH. METHODS: One-shot SAH model was employed in male Sprague-Dawley rats. Hyperglycemia was triggered by intraperitoneal streptozotocin administration (50 mg/kg) 7 days before SAH induction. The severity of cerebral vasospasm was determined by the cross-sectional area of basilar artery (BA) in male rats randomly assigned to 1 of 4 groups: control, hyperglycemia only, SAH only, and SAH with hyperglycemia. The expression of endothelial nitric oxide synthase (eNOS) and induced nitric oxide synthase (iNOS) in the BA were analyzed by immunohistochemistry. RESULTS: The mean (standard deviation) blood glucose level was 433.0 (98.3) and 156.5 (31.7) mg/dL in streptozotocin-treated and untreated rats, respectively. Hyperglycemic rats exhibited poorer neurobehavioral performance than normoglycemic rats when subjected to SAH. Hyperglycemia-mediated exacerbation of vasospasm was evident by the greater decrease in the BA cross-sectional area in the hyperglycemic SAH group than in the SAH only group. Furthermore, there was more decreased expression of eNOS and increased expression of iNOS within the vessels of the hyperglycemic SAH rats. CONCLUSION: Hyperglycemia exacerbated cerebral vasospasm and was associated with poorer neurological outcomes following SAH. Our findings also suggested the nitric oxide pathway as a potential underlying mechanism via the dysregulation of eNOS and iNOS.