Abstract WP321: The Role of Neuronal Sirt1 in Ischemic Stroke: Regulation of the Metabolic Imbalance

Abstract

Introduction: Sirt1 is a NAD+ dependent deacetylase that is known as an important metabolic regulator for type 2 diabetes melitus. To determine the role of Sirt1 in ischemic stroke-induced metabolic imbalance, we generated the neuronal specific Sirt1 knock-in (nSirt1 KI) and knock-out (Sirt1 KO) mice and examined its effect and mechanism. Methods: To determine the role of Sirt1 in ischemic stroke-induced impaired metabolic actions including insulin and glucose abnormality, we tested the pharmacological effects of Metformin and Sirtinol as Sirt1 activator and inhibitor. To determine the genetic role of neuronal Sirt1 in the brain, we generated the nSirt1 KI mice and Sirt1 KO. We used the Ischemia/Reperfusion (I/R: 1h middle cerebral artery occlusion (MCAO)/23h reperfusion) injury model to induce the abnormal metabolic changes. Infarction volume was measured by TTC staining and we determined neurological deficit score (NDS) at 23h after 1h MCAO. The level of glucose and insulin were measured by a drop of tail blood using test-strip and ELISA Kit before, during (every 10 minutes interval), and after MCAO. Results: Metformin reduced infarction volume and Sirtinol worsened the infarction volume via Sirt1 signaling pathway. Heterozygous Sirt1 KO (Sirt1 +/-) mice showed decreased relative cerebral blood flow (rCBF) and worsen infarction volume in ischemic areas, whereas nSirt1 KI mice exhibited increased rCBF, improved NDS, regulating abnormal blood glucose and insulin, and reduced infarction volume by 42% compare to that of littermate control in I/R injury model (n=7, p<0.05). Based on western blotting analysis of brain lysates in nSirt1 KI mice, the expression of Sirt1 was significantly increased. Glucose regulation by overexpression of Sirt1 and reduced infarction volume in nSirt1 KI mice were reversed by Sirtinol. Conclusion: These findings indicate that the important neuroprotective effect of neuronal cells is mediated by Sirt1 overexpression and suggest that upregulation of neuronal Sirt1 may be an important therapeutic target for ischemic stroke via regulating metabolic imbalance.