Restoration of Cerebral Vasoreactivity by an L-Type Calcium Channel Blocker following Fluid Percussion Brain Injury

Mitigating Traumatic Brain Injury: A Narrative Review of Supplementation and Dietary Protocols

Traumatic brain injuries (TBIs) constitute a significant public health issue and a major source of disability and death in the United States and worldwide. TBIs are strongly associated with high morbidity and mortality rates, resulting in a host of negative health outcomes and long-term complications and placing a heavy financial burden on healthcare systems. One promising avenue for the prevention and treatment of brain injuries is the design of TBI-specific supplementation and dietary protocols centred around nutraceuticals and biochemical compounds whose mechanisms of action have been shown to interfere with, and potentially alleviate, some of the neurophysiological processes triggered by TBI. For example, evidence suggests that creatine monohydrate and omega-3 fatty acids (DHA and EPA) help decrease inflammation, reduce neural damage and maintain adequate energy supply to the brain following injury. Similarly, melatonin supplementation may improve some of the sleep disturbances often experienced post-TBI. The scope of this narrative review is to summarise the available literature on the neuroprotective effects of selected nutrients in the context of TBI-related outcomes and provide an evidence-based overview of supplementation and dietary protocols that may be considered in individuals affected by-or at high risk for-concussion and more severe head traumas. Prophylactic and/or therapeutic compounds under investigation include creatine monohydrate, omega-3 fatty acids, BCAAs, riboflavin, choline, magnesium, berry anthocyanins, Boswellia serrata, enzogenol, N-Acetylcysteine and melatonin. Results from this analysis are also placed in the context of assessing and addressing important health-related and physiological parameters in the peri-impact period such as premorbid nutrient and metabolic health status, blood glucose regulation and thermoregulation following injury, caffeine consumption and sleep behaviours. As clinical evidence in this research field is rapidly emerging, a comprehensive approach including appropriate nutritional interventions has the potential to mitigate some of the physical, neurological, and emotional damage inflicted by TBIs, promote timely and effective recovery, and inform policymakers in the development of prevention strategies.

The protective effects of statins in traumatic brain injury

Traumatic brain injury (TBI), often referred to as the "silent epidemic", is the most common cause of mortality and morbidity worldwide among all trauma-related injuries. It is associated with considerable personal, medical, and economic consequences. Although remarkable advances in therapeutic approaches have been made, current treatments and clinical management for TBI recovery still remain to be improved. One of the factors that may contribute to this gap is that existing therapies target only a single event or pathology. However, brain injury after TBI involves various pathological mechanisms, including inflammation, oxidative stress, blood-brain barrier (BBB) disruption, ionic disturbance, excitotoxicity, mitochondrial dysfunction, neuronal necrosis, and apoptosis. Statins have several beneficial pleiotropic effects (anti-excitotoxicity, anti-inflammatory, anti-oxidant, anti-thrombotic, immunomodulatory activity, endothelial and vasoactive properties) in addition to promoting angiogenesis, neurogenesis, and synaptogenesis in TBI. Supposedly, using agents such as statins that target numerous and diverse pathological mechanisms, may be more effective than a single-target approach in TBI management. The current review was undertaken to investigate and summarize the protective mechanisms of statins against TBI. The limitations of conducted studies and directions for future research on this potential therapeutic application of statins are also discussed.

NS1619 Alleviate Brain-Derived Extracellular Vesicle-Induced Brain Injury by Regulating BKca Channel and Nrf2/HO-1/NF-ĸB Pathway

Brain induced extracellular vesicle (BDEV) elevates after traumatic brain injury (TBI) and contributes to secondary brain injury. However, the role of BDEV in TBI remains unclear. In this study, we determined the mechanisms of BDEV in brain injury and explored whether neuroprotective drug BKca channel opener NS1619 may attenuate BDEV-induced brain injury. We injected BDEV and lactadherin, respectively, to mimic the up and downregulation of BDEV after TBI and illustrated the role of BDEV in vivo. In vitro, the membrane potential and calcium concentration of HT-22, bEnd3, and BV-2 were measured by fluorescent staining. The effects of BDEV and NS1619 on HT-22 were evaluated by CCK-8, LDH release assay, Na⁺/k⁺-ATPase activity, JC-1 staining, DHE staining, and 4-HNE staining, respectively. The role of BDEV and NS1619 on the Nrf2/HO-1/p65 pathway was also evaluated in HT-22. Finally, we administrated TBI mice with NS1619 to clarify the role of NS1619 against BDEV in vivo. Our results suggested that BDEV aggravated and lactadherin mitigated TBI-induced EB leakage, brain edema, neuronal degeneration, apoptosis, ROS level, microgliosis, MMP-9 activity, and NF-κB activation. In vitro, BDEV-caused depolarized membrane potential and calcium overload were significantly attenuated by NS1619 in HT-22, bEnd3, and BV-2. BDEV markedly decreased cell viability, Na⁺/k⁺-ATPase activity, and caused mitochondrial dysregulation, oxidative stress, and NF-ĸB activation. NS1619 pretreatment alleviated above process and enhanced antioxidant system Nrf2/HO-1 in HT-22. Finally, NS1619 administration significantly inhibited neuroinflammation response and improved TBI outcome after TBI. NS1619 treatment also reduced 4-HNE content and NF-ĸB activation and enhanced Nrf2/HO-1 pathway. Our data showed that BDEV aggravated brain injury by perturbing cell membrane potential, calcium homeostasis, oxidative stress, and neuroinflammation. The BKca channel opener NS1619 attenuated BDEV-induced pathological process in vitro and in vivo by modulating the BKca channel and Nrf2/HO-1/NF-ĸB pathway.

Traumatic Brain Injury and Alzheimer's Disease: The Cerebrovascular Link

Traumatic brain injury (TBI) and Alzheimer's disease (AD) are devastating neurological disorders, whose complex relationship is not completely understood. Cerebrovascular pathology, a key element in both conditions, could represent a mechanistic link between Aβ/tau deposition after TBI and the development of post concussive syndrome, dementia and chronic traumatic encephalopathy (CTE). In addition to debilitating acute effects, TBI-induced neurovascular injuries accelerate amyloid β (Aβ) production and perivascular accumulation, arterial stiffness, tau hyperphosphorylation and tau/Aβ-induced blood brain barrier damage, giving rise to a deleterious feed-forward loop. We postulate that TBI can initiate cerebrovascular pathology, which is causally involved in the development of multiple forms of neurodegeneration including AD-like dementias. In this review, we will explore how novel biomarkers, animal and human studies with a focus on cerebrovascular dysfunction are contributing to the understanding of the consequences of TBI on the development of AD-like pathology.

•

Cerebrovascular dysfunction (CVD) is emerging as a key element in the development of neurodegeneration after TBI.

•

We propose that TBI initiates CVD, accelerating Aβ/tau deposition and leading to neurodegeneration and dementias.

•

Clarifying this connection will support the development of novel biomarkers and therapeutic approaches for both TBI and AD.

Clinical relevance of midline fluid percussion brain injury: Acute deficits, chronic morbidities and the utility of biomarkers

BACKGROUND

After 30 years of characterisation and implementation, fluid percussion injury (FPI) is firmly recognised as one of the best-characterised reproducible and clinically relevant models of TBI, encompassing concussion through diffuse axonal injury (DAI). Depending on the specific injury parameters (e.g. injury site, mechanical force), FPI can model diffuse TBI with or without a focal component and may be designated as mild-to-severe according to the chosen mechanical forces and resulting acute neurological responses. Among FPI models, midline FPI may best represent clinical diffuse TBI, because of the acute behavioural deficits, the transition to late-onset behavioural morbidities and the absence of gross histopathology.

REVIEW

The goal here was to review acute and chronic physiological and behavioural deficits and morbidities associated with diffuse TBI induced by midline FPI. In the absence of neurodegenerative sequelae associated with focal injury, there is a need for biomarkers in the diagnostic, prognostic, predictive and therapeutic approaches to evaluate outcomes from TBI.

CONCLUSIONS

The current literature suggests that midline FPI offers a clinically-relevant, validated model of diffuse TBI to investigators wishing to evaluate novel therapeutic strategies in the treatment of TBI and the utility of biomarkers in the delivery of healthcare to patients with brain injury.

Catecholaminergic based therapies for functional recovery after TBI

Among the many pathophysiologic consequences of traumatic brain injury are changes in catecholamines, including dopamine, epinephrine, and norepinephrine. In the context of TBI, dopamine is the one most extensively studied, though some research exploring epinephrine and norepinephrine have also been published. The purpose of this review is to summarize the evidence surrounding use of drugs that target the catecholaminergic system on pathophysiological and functional outcomes of TBI using published evidence from pre-clinical and clinical brain injury studies. Evidence of the effects of specific drugs that target catecholamines as agonists or antagonists will be discussed. Taken together, available evidence suggests that therapies targeting the catecholaminergic system may attenuate functional deficits after TBI. Notably, it is fairly common for TBI patients to be treated with catecholamine agonists for either physiological symptoms of TBI (e.g. altered cerebral perfusion pressures) or a co-occuring condition (e.g. shock), or cognitive symptoms (e.g. attentional and arousal deficits). Previous clinical trials are limited by methodological limitations, failure to replicate findings, challenges translating therapies to clinical practice, the complexity or lack of specificity of catecholamine receptors, as well as potentially counfounding effects of personal and genetic factors. Overall, there is a need for additional research evidence, along with a need for systematic dissemination of important study details and results as outlined in the common data elements published by the National Institute of Neurological Diseases and Stroke. Ultimately, a better understanding of catecholamines in the context of TBI may lead to therapeutic advancements. This article is part of a Special Issue entitled SI:Brain injury and recovery.

Voltage-gated calcium channel antagonists and traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of death and disability in the United States. Despite more than 30 years of research, no pharmacological agents have been identified that improve neurological function following TBI. However, several lines of research described in this review provide support for further development of voltage gated calcium channel (VGCC) antagonists as potential therapeutic agents. Following TBI, neurons and astrocytes experience a rapid and sometimes enduring increase in intracellular calcium ([Ca²⁺]_i). These fluxes in [Ca²⁺]_i drive not only apoptotic and necrotic cell death, but also can lead to long-term cell dysfunction in surviving cells. In a limited number of in vitro experiments, both L-type and N-type VGCC antagonists successfully reduced calcium loads as well as neuronal and astrocytic cell death following mechanical injury. In rodent models of TBI, administration of VGCC antagonists reduced cell death and improved cognitive function. It is clear that there is a critical need to find effective therapeutics and rational drug delivery strategies for the management and treatment of TBI, and we believe that further investigation of VGCC antagonists should be pursued before ruling out the possibility of successful translation to the clinic.

Edaravone increases regional cerebral blood flow after traumatic brain injury in mice

Traumatic brain injury (TBI) is a major cause of preventable death and serious morbidity, with subsequent low cerebral blood flow (CBF) considered to be associated with poor prognosis. In the present study, we demonstrated the effect of the free radical scavenger edaravone on regional CBF (rCBF) after TBI. Male mice (C57/BL6) were subjected to TBI using a controlled cortical impactor device. Immediately after TBI, the animals were intravenously administered 3.0 mg/kg of edaravone or a vehicle saline solution. Two-dimensional rCBF images were acquired before and 24 h post-TBI, and were quantified in the ipsilateral and contralateral hemispheres (n = 5 animals per group). CBF in the vehicle-treated animals decreased broadly over the ipsilateral hemisphere, with the region of low rCBF spreading from the frontal cortex to the occipital lobe. The zone of lowest rCBF matched that of the contusion area. The mean rCBF at 24 h for a defined elliptical region between the bregma and lambda was 73.7 ± 5.8 %. In comparison, the reduction of rCBF in edaravone-treated animals was significantly attenuated (93.4 ± 5.7 %, p < 0.05). The edaravone-treated animals also exhibited higher rCBF in the contralateral hemisphere compared with that seen in -vehicle-treated animals. It is suggested that edaravone reduces neuronal damage by scavenging reactive oxygen species (ROS) and by maintaining intact the autoregulation of the cerebral vasculature.

Tight glycemic control increases metabolic distress in traumatic brain injury: a randomized controlled within-subjects trial

OBJECTIVE

To determine the effects of tight glycemic control on brain metabolism after traumatic brain injury using brain positron emission tomography and microdialysis.

DESIGN

Single-center, randomized controlled within-subject crossover observational trial.

SETTING

Academic intensive care unit.

METHODS

We performed a prospective, unblinded randomized controlled within-subject crossover trial of tight (80-110 mg/dL) vs. loose (120-150 mg/dL) glycemic control in patients with severe traumatic brain injury to determine the effects of glycemic control on brain glucose metabolism, as measured by [18F] deoxy-D-glucose brain positron emission tomography. Brain microdialysis was done simultaneously.

MEASUREMENTS AND MAIN RESULTS

Thirteen severely injured traumatic brain injury patients underwent the study between 3 and 8 days (mean 4.8 days) after traumatic brain injury. In ten of these subjects, global brain and gray matter tissues demonstrated higher glucose metabolic rates while glucose was under tight control as compared with loose control (3.2 ± 0.6 vs. 2.4 + 0.4, p = .02 [whole brain] and 3.8 ± 1.4 vs. 2.9 ± 0.8, p = .05 [gray matter]). However, the responses were heterogeneous with pericontusional tissue demonstrating the least state-dependent change. Cerebral microdialysis demonstrated more frequent critical reductions in glucose (p = .02) and elevations of lactate/pyruvate ratio (p = .03) during tight glycemic control.

CONCLUSION

Tight glycemic control results in increased global glucose uptake and an increased cerebral metabolic crisis after traumatic brain injury. The mechanisms leading to the enhancement of metabolic crisis are unclear, but delivery of more glucose through mild hyperglycemia may be necessary after traumatic brain injury.

Postinjury treatment with rolipram increases hemorrhage after traumatic brain injury

The pathology caused by traumatic brain injury (TBI) is exacerbated by the inflammatory response of the injured brain. Two proinflammatory cytokines that contribute to inflammation after TBI are tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). From previous studies using the parasagittal fluid-percussion brain injury model, we reported that the anti-inflammatory drug rolipram, a phosphodiesterase 4 inhibitor, reduced TNF-α and IL-1β levels and improved histopathological outcome when administered 30 min prior to injury. We now report that treatment with (±)-rolipram given 30 min after injury significantly reduced TNF-α levels in the cortex and hippocampus. However, postinjury administration of (±)-rolipram significantly increased cortical contusion volume and increased atrophy of the cortex compared with vehicle-treated animals at 10 days postinjury. Thus, despite the reduction in proinflammatory cytokine levels, histopathological outcome was worsened with post-TBI (±)-rolipram treatment. Further histological analysis of (±)-rolipram-treated TBI animals revealed significant hemorrhage in the contused brain. Given the well-known role of (±)-rolipram of increasing vasodilation, it is likely that (±)-rolipram worsened outcome after fluid-percussion brain injury by causing increased bleeding.

Traumatic brain injury in adult rats causes progressive nigrostriatal dopaminergic cell loss and enhanced vulnerability to the pesticide paraquat

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of nigrostriatal dopaminergic neurons and the accumulation of alpha-synuclein. Both traumatic brain injury (TBI) and pesticides are risk factors for PD, but whether TBI causes nigrostriatal dopaminergic cell loss in experimental models and whether it acts synergistically with pesticides is unknown. We have examined the acute and long-term effects of TBI and exposure to low doses of the pesticide paraquat, separately and in combination, on nigrostriatal dopaminergic neurons in adult male rats. In an acute study, rats received moderate TBI by lateral fluid percussion (LFP) injury, were injected with saline or paraquat (10 mg/kg IP) 3 and 6 days after LFP, were sacrificed 5 days later, and their brains processed for immunohistochemistry. TBI alone increased microglial activation in the substantia nigra, and caused a 15% loss of dopaminergic neurons ipsilaterally. Paraquat increased the TBI effect, causing a 30% bilateral loss of dopaminergic neurons, reduced striatal tyrosine hydroxylase (TH) immunoreactivity more than TBI alone, and induced alpha-synuclein accumulation in the substantia nigra pars compacta. In a long-term study, rats received moderate LFP, were injected with saline or paraquat at 21 and 22 weeks post-injury, and were sacrificed 4 weeks later. At 26 weeks post injury, TBI alone induced a 30% bilateral loss of dopaminergic neurons that was not exacerbated by paraquat. These data suggest that TBI is sufficient to induce a progressive degeneration of nigrostriatal dopaminergic neurons. Furthermore, TBI and pesticide exposure, when occurring within a defined time frame, could combine to increase the PD risk.

Blast-induced phenotypic switching in cerebral vasospasm

Vasospasm of the cerebrovasculature is a common manifestation of blast-induced traumatic brain injury (bTBI) reported among combat casualties in the conflicts in Afghanistan and Iraq. Cerebral vasospasm occurs more frequently, and with earlier onset, in bTBI patients than in patients with other TBI injury modes, such as blunt force trauma. Though vasospasm is usually associated with the presence of subarachnoid hemorrhage (SAH), SAH is not required for vasospasm in bTBI, which suggests that the unique mechanics of blast injury could potentiate vasospasm onset, accounting for the increased incidence. Here, using theoretical and in vitro models, we show that a single rapid mechanical insult can induce vascular hypercontractility and remodeling, indicative of vasospasm initiation. We employed high-velocity stretching of engineered arterial lamellae to simulate the mechanical forces of a blast pulse on the vasculature. An hour after a simulated blast, injured tissues displayed altered intracellular calcium dynamics leading to hypersensitivity to contractile stimulus with endothelin-1. One day after simulated blast, tissues exhibited blast force dependent prolonged hypercontraction and vascular smooth muscle phenotype switching, indicative of remodeling. These results suggest that an acute, blast-like injury is sufficient to induce a hypercontraction-induced genetic switch that potentiates vascular remodeling, and cerebral vasospasm, in bTBI patients.

Acute neuroprotection to pilocarpine-induced seizures is not sustained after traumatic brain injury in the developing rat

Following CNS injury there is a period of vulnerability when cells will not easily tolerate a secondary insult. However recent studies have shown that following traumatic brain injury (TBI), as well as hypoxic-ischemic injuries, the CNS may experience a period of protection termed "preconditioning." While there is literature characterizing the properties of vulnerability and preconditioning in the adult rodent, there is an absence of comparable literature in the developing rat. To determine if there is a window of vulnerability in the developing rat, post-natal day 19 animals were subjected to a severe lateral fluid percussion injury followed by pilocarpine (Pc)-induced status epilepticus at 1, 6 or 24 h post TBI. During the first 24 h after TBI, the dorsal hippocampus exhibited less status epilepticus-induced cell death than that normally seen following Pc administration alone. Instead of producing a state of hippocampal vulnerability to activation, TBI produced a state of neuroprotection. However, in a second group of animals evaluated 20 weeks post injury, double-injured animals were statistically indistinguishable in terms of seizure threshold, mossy fiber sprouting and cell survival when compared to those treated with Pc alone. TBI, therefore, produced a temporary state of neuroprotection from seizure-induced cell death in the developing rat; however, this ultimately conferred no long-term protection from altered hippocampal circuit rearrangements, enhanced excitability or later convulsive seizures.

Emerging treatments for traumatic brain injury

BACKGROUND

This review summarizes promising approaches for the treatment of traumatic brain injury (TBI) that are in either preclinical or clinical trials.

OBJECTIVE

The pathophysiology underlying neurological deficits after TBI is described. An overview of select therapies for TBI with neuroprotective and neurorestorative effects is presented.

METHODS

A literature review of preclinical TBI studies and clinical TBI trials related to neuroprotective and neurorestorative therapeutic approaches is provided.

RESULTS/CONCLUSION

Nearly all Phase II/III clinical trials in neuroprotection have failed to show any consistent improvement in outcome for TBI patients. The next decade will witness an increasing number of clinical trials that seek to translate preclinical research discoveries to the clinic. Promising drug- or cell-based therapeutic approaches include erythropoietin and its carbamylated form, statins, bone marrow stromal cells, stem cells singularly or in combination or with biomaterials to reduce brain injury via neuroprotection and promote brain remodeling via angiogenesis, neurogenesis, and synaptogenesis with a final goal to improve functional outcome of TBI patients. In addition, enriched environment and voluntary physical exercise show promise in promoting functional outcome after TBI, and should be evaluated alone or in combination with other treatments as therapeutic approaches for TBI.

An analysis of regional microvascular loss and recovery following two grades of fluid percussion trauma: a role for hypoxia-inducible factors in traumatic brain injury

Secondary hypoxic/ischemic injuries, stemming from reductions in cerebral blood flow are important contributing factors in progressive neuronal dysfunction after brain trauma. A greater preclinical understanding of how brain trauma leads to secondary hypoxia/ischemia is necessary in the development of posttraumatic brain injury (TBI) therapeutics. To this end, we examined the density of microvascular coverage in the injured and contralateral cortical hemispheres using two intensities of fluid percussion trauma in rats. A silicone microangiography technique showed a significant loss in microvascular density in 2 atmosphere (atm) (16.9+/-3.8%) and 3 atm (15.7+/-1.3%) injured animals relative to sham animals (29.9+/-2.5%; P<0.01). RECA-1 immunohistochemistry indicated that capillary changes involved a reduction in capillary number and diameter. Reduction in microvascular density was shown to be a diffuse phenomenon occurring up to 4 mm rostral and caudal to the injury epicenter. Recovery of microvasculature occurred by 2 weeks after injury only in the 2 atm injury group. Expression of HIF1alpha and increased vascular endothelial growth factor expression were observed in the ipsilateral hippocampus suggesting sufficiently impaired microcirculation resulting in the expression of hypoxic-response proteins. Collectively, the results indicate diffuse and heterogeneous microvascular alterations as well as endogenous expression of neuroprotective and neovascularization pathways after TBI.

Statins increase neurogenesis in the dentate gyrus, reduce delayed neuronal death in the hippocampal CA3 region, and improve spatial learning in rat after traumatic brain injury

Traumatic brain injury (TBI) remains a major public health problem globally. Presently, there is no way to restore cognitive deficits caused by TBI. In this study, we seek to evaluate the effect of statins (simvastatin and atorvastatin) on the spatial learning and neurogenesis in rats subjected to controlled cortical impact. Rats were treated with atorvastatin and simvastatin 1 day after TBI and daily for 14 days. Morris water maze tests were performed during weeks 2 and 5 after TBI. Bromodeoxyuridine (BrdU; 50 mg/kg) was intraperitoneally injected 1 day after TBI and daily for 14 days. Brain tissue was processed for immunohistochemical staining to identify newly generated cells and vessels. Our data show that (1) treatment of TBI with statins improves spatial learning on days 31-35 after onset of TBI; (2) in the non-neurogenic region of the hippocampal CA3 region, statin treatment reduces the neuronal loss after TBI, demonstrating the neuroprotective effect of statins; (3) in the neurogenic region of the dentate gyrus, treatment of TBI with statins enhances neurogenesis; (4) statin treatment augments TBI-induced angiogenesis; and (5) treatment with simvastatin at the same dose provides a therapeutic effect superior to treatment with atorvastatin. These results suggest that statins may be candidates for treatment of TBI.

Multi-modal magnetic resonance imaging alterations in two rat models of mild neurotrauma

Magnetic resonance imaging (MRI) is increasingly used in the assessment of the severity and progression of neurotrauma. We evaluated temporal and regional changes after mild fluid percussion (FPI) and controlled cortical impact (CCI) injury using T2-weighted-imaging (T2WI) and diffusion-weighted imaging (DWI) MRI over 7 days. Region of interest analysis of brain areas distant to the injury site (such as the hippocampus, retrosplenial and piriform cortices, and the thalamus) was undertaken. In the hippocampus of CCI animals, we found a slow increase (51%) in apparent diffusion coefficients (ADC) over 72 h, which returned to control values. The hippocampal T2 values in the CCI animals were elevated by 18% over the 7-day time course compared to control, indicative of edema formation. Histological analysis supported the lack of overt cellular loss in most brain regions after mild CCI injury. FPI animals showed a generalized decrease in hippocampal ADC values over the first 72 h, which then returned to sham levels, with decreased T2 values over the same period, which remained depressed at 7 days. Histological assessment of FPI animals revealed numerous shrunken cells in the hippocampus and thalamus, but other regions showed little damage. Increased immunohistochemical staining for microglia and astroglia at 7 days post-injury was greater in FPI animals within the affected brain regions. In summary, traumatic brain injury is less severe in mild CCI than FPI, based on the temporal events assessed with MRI.

Age-dependent reduction of cortical contusion volume by ketones after traumatic brain injury

Although the adult brain primarily metabolizes glucose, the evidence from the starvation literature has demonstrated that the adult brain retains some potential to revert to ketone metabolism. This attribute has been exploited recently to shift the adult brain toward ketone metabolism after traumatic brain injury (TBI), resulting in increased cerebral uptake and oxidation of exogenously administered ketones and improved cerebral energy. The ability to utilize ketones as an alternative substrate decreases with cerebral maturation, suggesting that the younger brain has a greater ability to metabolize this substrate and may be more receptive to this therapy. It was hypothesized that the administration of ketones after TBI in the developing brain will decrease lesion size in an age-dependent manner. Postnatal day (PND) 17, 35, 45, and 65 rats were placed on either a standard or ketogenic (KG) diet after controlled cortical impact (CCI) injury. PND35 and PND45 KG-fed animals showed a 58% and 39% reduction in cortical contusion volume, respectively, at 7 days post-injury. The KG diet had no effect on contusion volume in PND17 and PND65 injured rats. Both PND35 and PND45 KG-fed groups revealed fewer Fluoro-Jade-positive cells in the cortex and hippocampus at 6 hr and showed earlier decreases in plasma lactate compared to standard-fed animals. The age-dependent ketogenic neuroprotection is likely related to age-related differences in cerebral metabolism of ketones and suggests that alternative substrate therapy has potential applications for younger head-injured patients.