Ketone Ester Supplementation Does Not Impair Cognitive or Motor Performance and Delays CNS Oxygen Toxicity in Male Sprague‐Dawley Rats

Abstract

Oxygen acts as a drug at increased atmospheric pressures, such as occurs during exposure to hyperbaric oxygen (HBO) during hyperbaric and undersea medicine. Use of HBO is limited by the risk of developing CNS oxygen toxicity (CNS‐OT) which manifests as seizures. The ketogenic diet (KD) is used clinically as an anticonvulsant therapy for refractory epilepsy but requires significant dietary restrictions to maintain ketosis. Studies suggest that exogenous ketone ester (KE) induces ketosis and delays the onset of CNS‐OT without the need for dietary restrictions; however, an optimal dose of KE that provides neuroprotection and delays the onset of CNS‐OT without hindering cognitive or motor performance has yet to be elucidated. Sprague Dawley rats received either no gavage, vehicle gavage, or 7.5 g/kg KE gavage and were subjected to a battery of behavioral tests: DigiGait (DG), Light/Dark (LD), open field (OF), and novel object recognition (NOR). No significant differences were observed in motor performance on the DG tests in all treatment groups, suggesting that there is no effect of KE on motor performance. No differences in the time spent in the light or dark zones in the LD test were observed between groups, nor in the latency time to the dark zone. KE‐treated rats exhibited reduced distance traveled in the dark zone, suggesting the KE may be anxiolytic, a property that has been reported previously. No differences in time spent in the perimeter or center zones between the groups in the OF test were noted; however, KE‐treated rats exhibited decreased distance moved and speed, similar to what was seen in the DigiGait test which again may reflect an anxiolytic effect. To further explore this result, we evaluated overall activity level of the rats using the OF test. KE‐treated rats exhibited increased overall activity, indicating that the animals were exploring the areas and were less anxious than vehicle controls. Although there were no significant differences between the groups in the NOR test, KE‐treated rats exhibited a trend in both exploratory preference and discrimination index suggesting that the animals learned and were able to recall that a novel object was present. Additional experiments are currently being conducted in which vehicle‐ or KE‐treated rats are implanted with radio‐telemetry modules, allowing for real‐time monitoring of EEG, ECG, and respiratory EMG during an HBO dive protocol. These experiments are underway but have thus far shown that the KE increases latency time to seizure over vehicle (24.9±6.7; 15.5±6.5, n=8). Together, these findings suggest that a single administration of KE will delay onset of CNS‐OT without hindering performance. This work is funded by the Office of Naval Research.Support or Funding InformationOffice of Naval Research