Introduction: Our previous work demonstrates that resveratrol, a naturally occurring polyphenol, protects against cerebral ischemia when administered 2 or 14 days prior to injury. Resveratrol activates Sirt1, an NAD+-dependent deacylase that regulates cellular metabolism. It has been postulated that neuronal Sirt1 directly mediates this neuroprotection but it remains to be empirically tested.
Objective: The objective of this study was to generate an inducible, neuronal-specific Sirt1 knockout mouse and determine whether neuronal Sirt1 is necessary for resveratrol-induced ischemic tolerance.
Methods: Twenty to twenty-five gram neuronal-specific Sirt1 knockout mice (Sirt1neu-/-) and WTs were induced with tamoxifen. Mice were randomized for 1) western blot; 2) resveratrol preconditioning (RPC; 10 mg/kg resveratrol i.p.) or vehicle (1.5% DMSO; 0.9% saline) treatment 2 days prior to 60 minute middle cerebral artery occlusion (MCAo); 3) untargeted primary metabolomics by GC-TOF-MS; or 4) transcription factor activation profiling. Twenty-four hours following MCAo, neurological score was used to assess functional outcome and infarct volume was quantified by TTC staining.
Results: Tamoxifen treatment removed WT Sirt1 protein from major brain regions but not from heart (Figure 1A, n=3). In WT, RPC reduced infarct volume by 43.7% and improved neurological score by nearly 3 points, however these effects were lost in Sirt1neu-/- (Figure 1B, n=5-9). Compared to WT, metabolic profiles from Sirt1neu-/- displayed significantly altered glycolysis metabolites (Figure 1C, n=8). Activation of hypoxia inducible factor (HIF) was reduced by 48% in Sirt1neu-/- (Figure 1D, n=3).
Conclusions: We generated and utilized an inducible, neuronal-specific knockout mouse to demonstrate that neuronal Sirt1 specifically is required for RPC-induced ischemic tolerance. Additionally, Sirt1 regulates glycolysis in the brain, possibly through its interaction with HIF.