The link between brain acidosis, breathing and seizures: a novel mechanism of action for the ketogenic diet in a model of infantile spasms

Abstract

Infantile Spasms syndrome is a catastrophic, epileptic encephalopathy of infancy that is often refractory to current antiepileptic therapies. The ketogenic diet has emerged as an alternative treatment for patients with medically intractable epilepsy, though the prospective validity and mechanism of action for Infantile Spasms remains largely unexplored. We investigated the ketogenic diet’s efficacy as well as its mechanism of action in a rodent model of intractable Infantile Spasms. The spasms were induced using the triple-hit paradigm and the animals were then artificially reared and put on either the ketogenic diet (4:1 fats: carbohydrate + protein) or a control-milk diet (CM; 1.7:1). 31Phosphorus magnetic resonance spectroscopy (MRS) and head-out plethysmography were examined in conjunction with continuous video-EEG behavioural recordings in lesioned animals and sham-operated controls. The ketogenic diet resulted in a peripheral ketosis observed both in the blood and urine. The ketogenic diet led to a robust reduction in the frequency of spasms observed, with approximately a 1.5-fold increase in the rate of survival. Intriguingly, the ketogenic diet resulted in an intracerebral acidosis as measured with 31Phosphorus magnetic resonance spectroscopy. In addition, the respiratory profile of the lesioned rats on the ketogenic diet was significantly altered with slower, deeper, and longer breathing, resulting in decreased levels of expired CO2. Sodium bicarbonate supplementation, acting as a pH buffer, partially reversed the ketogenic diet’s protective effects on spasm frequency. There were no differences in the mitochondrial respiratory profiles in the liver and brain frontal cortex measured between the groups, supporting the notion that the effects of the ketogenic diet on breathing are not entirely due to changes in intermediary metabolism. Together, our results indicate that the ketogenic diet produces its anticonvulsant effects through changes in respiration leading to intracerebral acidosis. These findings provide a novel understanding of the mechanisms underlying the anti-seizure effects of the ketogenic diet in Infantile Spasms. Further research is required to determine whether the effects of the ketogenic diet on breathing and intracerebral acid-base balance are seen in other pediatric models of epilepsy.

Addition of Prebiotics to the Ketogenic Diet Improves Metabolic Profile but Does Not Affect Seizures in a Rodent Model of Infantile Spasms Syndrome

“…Data regarding the impact of normal carbohydrate and the KD on spasms, metabolites, and the gut microbiota have been previously published [ 3 , 8 , 26 ]. Both male and female animals were used for the study.…”

“…Both male and female animals were used for the study. The induction of IS and animal rearing were performed as previously described [ 17 , 26 ]. Briefly, at postnatal day (P) 4, male and female neonatal rats were positioned in a stereotaxic apparatus for neonatal rat surgery (Benchmark Angle One, MyNeurolab.com, St. Louis, MO, USA).…”

“…Animals were individually placed in Styrofoam cups warmed in a water bath (45 °C) and filled with bedding material (31–33 °C). Animals were continuously fed either a KD (4:1 ratio by weight of fats to carbohydrate plus protein, Table S1 ) with or without PRE from P5 to P8 through an implanted cheek cannula, as previously described [ 26 ]. The time-frame was chosen as this is a period when animals experience a high rate of seizures and when the antiseizure effects of the KD mimics what is observed in infants with seizure reductions in the range of 50% [ 26 ].…”

“…Animals were continuously fed either a KD (4:1 ratio by weight of fats to carbohydrate plus protein, Table S1 ) with or without PRE from P5 to P8 through an implanted cheek cannula, as previously described [ 26 ]. The time-frame was chosen as this is a period when animals experience a high rate of seizures and when the antiseizure effects of the KD mimics what is observed in infants with seizure reductions in the range of 50% [ 26 ]. All experiments were performed with the aim of keeping animal pain, stress, and numbers to a minimum, as stated in our ethics certification.…”

“…Spasms characterized by sudden extensor and flexor movements were recorded using a video system with Sirenia software (Pinnacle Technology, Lawrence, KS, USA) following previously described methods [ 17 , 26 ]. A total of 4 h of recordings on P7 were quantified per animal.…”