Abstract 03: High-Dose Intranasal Insulin During CPR Improves Neurological Outcomes in a Rat Model of Cardiac Arrest

Abstract

Introduction: Post-cardiac arrest brain injury is a major cause of mortality and morbidity. Insulin has well-established CNS neuroprotecive properties mediated by the AKT survival signaling pathway, and known transnasal transport mechanisms make it possible to rapidly achieve therapeutic brain insulin levels after intranasal delivery. Hypothesis: We hypothesize that high-dose intranasal insulin (HD-IN-I) administered during CPR, could improve neurologic outcomes in a rat model of asphyxial cardiac arrest. Methods: Male Long Evans rats were subjected to 8-minute asphyxial cardiac arrest then block randomized to HD-IN-I (1.92 U/g brain wet weight) or placebo (PL) given at the onset of CPR by an experimental operator blinded to treatment. Sham operated rats were used as uninjured controls. For the long-term outcome study (n = 14/group), rats with return of spontaneous circulation (ROSC) were maintained at 37.0 ±0.5 °C for 72 hours and neurologic function was assessed on days 7 - 10. For the mechanistic study (n = 6/group), rats with ROSC were euthanized 30 minutes after ROSC and regional brain homogenates were analyzed by western blot for AKT phosporylation. Results: HD-IN-I during CPR had no statistically significant effect on ROSC rate (93% (13/14) HD-IN-I vs. 86% (12/14) PL, p > 0.05) or 10-day survival (71% (10/14) HD-INI vs. 43% (6/14) PL, p > 0.05). HD-IN-I had no significant impact on serum glucose concentrations. At 10 days post-ROSC, rats in the HD-IN-I group had significantly improved performance on rotarod (latency to fall 87±27 sec HD-IN-I vs. 41±18 sec PL, p < 0.05), Barnes maze (latency to escape box 27±15 sec HD-IN-I vs. 298±5 sec PL, p < 0.05), and passive avoidance (latency to re-enter shock chamber 300±0 sec HD-IN-I vs. 142±46 sec PL, p < 0.05) testing. Hippocampal phosph-AKT/total AKT ratio increased 2-fold in the placebo group and 5.7-fold in the HD-IN-I group relative to shams (p < 0.05). Conclusions: HD-IN-I administered during CPR causes rapid activation of brain AKT survival signaling and improves recovery of neurologic function in a rat cardiac arrest model. Additional studies are warranted to determine dose optimization, therapeutic window and effectiveness in large animal models to advance this novel therapy toward clinical trials.