The ketone ester, 3-hydroxybutyl-3-hydroxybutyrate, attenuates neurobehavioral deficits and improves neuropathology following controlled cortical impact in male rats

Traumatic brain injury (TBI) is a leading cause of human death and disability with no effective therapy to fully prevent long-term neurological deficits in surviving patients. Ketone ester supplementation is protective in animal models of neurodegeneration, but its efficacy against TBI pathophysiology is unknown. Here, we assessed the neuroprotective effect of the ketone monoester, 3-hydroxybutyl-3-hydroxybutyrate, (KE) in male Sprague Dawley rats (n=32). TBI was induced using the controlled cortical impact (CCI) with Sham animals not receiving the brain impact. KE was administered daily by oral gavage (0.5 ml/kg/day) and provided ad libitum at 0.3% (v/v) in the drinking water. KE supplementation started immediately after TBI and lasted for the duration of the study. Motor and sensory deficits were assessed using the Neurobehavioral Severity Scale-Revised (NSS-R) at four weeks post-injury. The NSS-R total score in CCI + KE (1.2 +/- 0.4) was significantly lower than in CCI + water (4.4 +/- 0.5). Similarly, the NSS-R motor scores in CCI + KE (0.6 +/- 0.7) were significantly lower than CCI + water (2.9 +/- 1.5). Although the NSS-R sensory score in the CCI + KE group (0.5 +/- 0.2) was significantly lower compared to CCI + water (1.8 +/- 0.4), no difference was observed between CCI + water and Sham + water (1.0 +/- 0.2) groups. The lesion volume was smaller in the CCI + KE (10 +/- 3 mm(3)) compared to CCI + water (47 +/- 11 mm(3); p < 0.001). KE significantly decreased Iba1(+) stained areas in the cortex and hippocampus, and GFAP(+) stained areas in all brain regions analyzed - prefrontal cortex, hippocampus, cortex, amygdala (p < 0.01). In summary, our results indicate that KE can protect against TBI-induced morphological and functional deficits when administered immediately after an insult.