The protective effect of the ketogenic diet on traumatic brain injury-induced cell death in juvenile rats

Clinical review: ketones and brain injury

Although much feared by clinicians, the ability to produce ketones has allowed humans to withstand prolonged periods of starvation. At such times, ketones can supply up to 50% of basal energy requirements. More interesting, however, is the fact that ketones can provide as much as 70% of the brain's energy needs, more efficiently than glucose. Studies suggest that during times of acute brain injury, cerebral uptake of ketones increases significantly. Researchers have thus attempted to attenuate the effects of cerebral injury by administering ketones exogenously. Hypertonic saline is commonly utilized for management of intracranial hypertension following cerebral injury. A solution containing both hypertonic saline and ketones may prove ideal for managing the dual problems of refractory intracranial hypertension and low cerebral energy levels. The purpose of the present review is to explore the physiology of ketone body utilization by the brain in health and in a variety of neurological conditions, and to discuss the potential for ketone supplementation as a therapeutic option in traumatic brain injury.

Does ketogenic diet alter seizure sensitivity and cell loss following fluid percussion injury?

Traumatic brain injury (TBI) frequently leads to epilepsy. The process of epileptogenesis - the development of that seizure state - is still poorly understood, and effective antiepileptogenic treatments have yet to be identified. The ketogenic diet (KD) has been shown to be effective as an antiepileptic therapy, but has not been extensively tested for its efficacy in preventing the development of the seizure state, and certainly not within the context of TBI-induced epileptogenesis. We have used a rat model of TBI - fluid percussion injury (FPI) - to test the hypothesis that KD treatment is antiepileptogenic and protects the brain from neuronal cell loss following TBI. Rats fed a KD had a higher seizure threshold (longer latency to flurothyl-induced seizure activity) than rats fed a standard diet (SD); this effect was seen when KD was in place at the time of seizure testing (3 and 6 weeks following FPI), but was absent when KD had been replaced by SD at time of testing. FPI caused significant hippocampal cell loss in both KD-fed and SD-fed rats; the degree of cell loss appeared to be reduced by KD treatment before FPI but not after FPI. These results are consistent with prior demonstrations that KD raises seizure threshold, but do not provide support for the hypothesis that KD administered for a limited time directly before or after FPI alters later seizure sensitivity; that is, within the limits of this model and protocol, there is no evidence for KD-induced antiepileptogenesis.

Neuroprotection by glucagon: role of gluconeogenesis

OBJECT

The severity of neurological impairment following traumatic brain injury (TBI) is exacerbated by several endogenous processes, including hyperglycemia, hypotension, and the generation of glutamate. However, in addition to controlling hyperglycemia, insulin has pleiotropic effects on tissue metabolism, which include reducing the concentration of the neurotoxic amino acid glutamate, making it unclear whether insulin's beneficial effects are attributable to the establishment of euglycemia per se. In the present study, the authors asked if reducing glutamate via approaches that do not lower glucose levels would improve neurological outcome following TBI.

METHODS

Glucagon activates gluconeogenesis by increasing the hepatic uptake of amino acids such as glutamate and facilitating their conversion to glucose. Glucagon was administered as a single intraperitoneal injection before or after closed head injury (CHI). Neurological function, brain histological features, blood glutamate and glucose levels, and CSF glutamate concentrations were measured.

RESULTS

A single intraperitoneal injection of glucagon (25 μg) into mice 10 minutes before or after CHI reduced lesion size by about 60% (p < 0.0001) and accelerated neurological recovery. The neuroprotective effect of glucagon was related to gluconeogenesis by decreasing the concentration of the neuroexcitatory amino acid glutamate in the circulation from 207 ± 32.1 μmol/L in untreated mice to 101.11 ± 21.6 μmol/L in treated mice (p < 0.001); a similar effect occurred in the CSF. The neuroprotective effect of glucagon was seen notwithstanding the attendant increase in blood glucose, the final substrate of gluconeogenesis.

CONCLUSIONS

Glucagon exerts a marked neuroprotective effect post-TBI by decreasing CNS glutamate. Glucagon was beneficial despite increasing blood glucose. Favorable effects also occurred when glucagon was given prior to TBI, suggesting its involvement in the preconditioning process. Thus, glucagon may be of value in providing neuroprotection when administered after TBI or prior to certain neurosurgical or cardiac interventions in which the incidence of perioperative ischemia is high.

Low-level blast raises intracranial pressure and impairs cognitive function in rats: prophylaxis with processed cereal feed

There is increasing evidence that even low levels of blast cause brain injury, but little is known about their thresholds and mechanisms. Exposure of rats to 10-60 kPa blasts elevate intracranial pressure (ICP) in a dose-dependent manner and impair cognitive function. We have evaluated a prophylactic measure against these brain injuries in a rat animal model, consisting of feeding them processed cereal. This type of feed is known to ameliorate disturbances in secretion of body fluids and to have anti-inflammatory effects. In humans, intake of processed cereals is effective against intestinal diarrhea and also reduces the symptoms of Ménière's disease. Rats were given either standard laboratory feed or processed cereal feed for 2 weeks before exposure to blast in a shock tube. The ICP was monitored at different time points up to 1 week after exposure to a 60-kPa blast, and for up to 24 h after exposure to a 30-kPa blast. Maximal ICP elevation was reached at 10 h in both groups. In the group of rats on standard feed exposed to 60 kPa, an ICP increase of 145% was noted at 10 h, and the corresponding increase in the rats fed processed cereal feed was only 50%. In rats exposed to a 30-kPa blast, those fed standard feed and processed cereal feed demonstrated increases of ICP of 80% and 40%, respectively. Cognitive function as measured by the Morris water maze was assessed in other groups of rats at 2 days after exposure to 10- or 30-kPa blasts. Their performance was significantly impaired at both exposure levels in rats on standard feed, but no functional impairment was seen in rats fed processed cereal feed.

Neuroprotective and anti-inflammatory activities of ketogenic diet on MPTP-induced neurotoxicity

Ketogenic diet (KD) is a high-fat, low-protein and low-carbohydrate diet. It is reported that KD can provide the neuroprotection for the neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease (PD) and amyotrophic lateral sclerosis. The main clinical symptom of PD is motor dysfunction derived from the loss of dopaminergic neurons in the substantia nigra (SN) and dopamine content in the striatum subsequently. It is well known that treatments with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in mice produce motor dysfunction, biochemical, and neurochemical changes remarkably similar to idiopathic PD patients. In this study, we investigated the neuroprotective and anti-inflammatory effects of KD in MPTP-treated mice. The data showed that pretreatment with KD alleviated the motor dysfunction induced by MPTP. The decrease of Nissl-staining and tyrosine hydroxylase (TH)-positive neurons induced by MPTP was inhibited in the SN. The change of dopamine was very similar to dopaminergic neurons in the SN. KD inhibited the activation of microglia induced by MPTP in the SN. The levels of proinflammatory cytokines (interleukin-1 beta, interleukin-6, and tumor necrosis factor-alpha) in the SN were also decreased and induced by MPTP. So, we concluded that KD was neuroprotective and anti-inflammatory against MPTP-neurotoxicity.

D-beta-hydroxybutyrate prevents MPP+-induced neurotoxicity in PC12 cells

Numerous studies show that D-beta-Hydroxybutyrate (DbetaHB) is neuroprotective. The present study was to explore the neuroprotective effects of DbetaHB against the cell death and apoptosis induced by 1-methyl-4-phenylpyridinium ion (MPP+) in PC12 cells. PC12 cells were pretreated with DbetaHB and followed by MPP+ exposure. The cell viability was determined by MTT assay. The morphological characteristics of apoptosis was observed by Acridine Orange (AO) staining and apoptotic rates were measured by flow cytometer. The product of lipid peroxidation, malondialdehyde (MDA), was measured using thiobarbituric acid method. The mitochondrial membrane potential (MMP), intracellular ROS and total glutathione were detected by microplate reader. In PC12 cells, pretreatment with DbetaHB significantly reduced MPP+-induced the decrease of cell viability. AO staining and flow cytometric analysis found DbetaHB inhibited MPP+-induced apoptosis. The measurement of MDA formation showed that DbetaHB alleviated lipid peroxidation induced by MPP+. The loss of MMP induced by MPP+ was preventive by DbetaHB. The changes of intracellular ROS and total glutathione induced by MPP+ were reversed by DbetaHB. DbetaHB protected PC12 cells against MPP+-induced death and apoptosis.