Ketogenic diet exposure during the juvenile period increases social behaviors and forebrain neural activation in adult Engrailed 2 null mice

Abstract

Prolonged consumption of ketogenic diets (KD) has reported neuroprotective benefits. Several studies suggest KD interventions could be useful in the management of neurological and developmental disorders. Alterations in the Engrailed (En) genes, specifically Engrailed 2 (En2), have neurodevelopmental consequences and produce autism-related behaviors. The following studies used En2 knockout (KO; En2(-/-)), and wild-type (WT; En2(+/+)), male mice fed either KD (80% fat, 0.1% carbohydrates) or control diet (CD; 10% fat, 70% carbohydrates). The objective was to determine whether a KD fed from weaning at postnatal day (PND) 21 to adulthood (PND 60) would alter brain monoamines concentrations, previously found dysregulated, and improve social outcomes. In WT animals, there was an increase in hypothalamic norepinephrine content in the KD-fed group. However, regional monoamines were not altered in KO mice in KD-fed compared with CD-fed group. In order to determine the effects of juvenile exposure to KD in mice with normal blood ketone levels, separate experiments were conducted in mice removed from the KD or CD and fed standard chow for 2days (PND 62). In a three-chamber social test with a novel mouse, KO mice previously exposed to the KD displayed similar social and self-grooming behaviors compared with the WT group. Groups previously exposed to a KD, regardless of genotype, had more c-Fos-positive cells in the cingulate cortex, lateral septal nuclei, and anterior bed nucleus of the stria terminalis. In the novel object condition, KO mice previously exposed to KD had similar behavioral responses and pattern of c-Fos immunoreactivity compared with the WT group. Thus, juvenile exposure to KD resulted in short-term consequences of improving social interactions and appropriate exploratory behaviors in a mouse model that displays autism-related behaviors. Such findings further our understanding of metabolic-based therapies for neurological and developmental disorders.

The effect of ketogenic diet on behaviors and synaptic functions of naive mice

“…We also tested the social behaviors of KD‐fed mice with three‐chamber apparatus and found no change in the social exploration preference, suggesting the social behavior is little affected by long‐term feeding of KD. These results are interesting in light that numerous studies have reported beneficial effect of KD in social behaviors in autism patients, animal models of autism and wildtype young adult rats (Ruskin et al, ; Ahn et al, ; Verpeut et al, ; Castro et al, ; Kasprowska‐Liskiewicz et al, ). The real reason for the discrepancy is not clear.…”

“…In addition, KD is shown to increase sociability in young male rats (Kasprowska‐Liskiewicz et al, ). However, it exhibited minimal effect in other studies (Ruskin et al, ; Verpeut, DiCicco‐Bloom, & Bello, ; Castro, Baronio, Perry, Riesgo, & Gottfried, ). The reasons for these inconsistencies are not very clear, possibly due to variation in animal husbandry and/or experimental designs.…”

Ketogenic diet improves behaviors in a maternal immune activation model of autism spectrum disorder

“…In both male and female MIA offspring a KD increased time spent in direct social contact with another mouse during the three-chamber test; in females this increase resulted in higher social contact time than control animals [ 34 ]. Studies using rodent ASD models with diverse etiologies [strain (mouse: BTBR and EL), genetic (mouse: Engrailed 2 knockout), gestational exposure (rat: valproic acid)] have also shown elevated sociability after KD feeding in three-chamber tests [ 24 – 26 , 28 ]. In addition, a KD normalizes play behavior in juvenile rats in the gestational valproic acid model [ 27 ].…”

“…This includes case studies in children describing improvements in core symptoms (as well as seizures) [ 19 , 20 ] and small pilot studies reporting varied responses including improvements during KD use [ 21 – 23 ]. More recently, studies have shown that KD treatment improves sociability and reduces self-directed repetitive behavior in animal models of ASD such as the BTBR T+ tf/J mouse strain [ 24 ], the EL mouse strain [ 25 ] and mice with genetic inactivation of the Engrailed 2 gene [ 26 ]. Specifically for environmentally-induced ASD, KD feeding improves sociability and repetitive behavior in the gestational valproic acid model in rats [ 27 , 28 ].…”

Ketone-Based Metabolic Therapy: Is Increased NAD+ a Primary Mechanism?

“…It is becoming apparent that beneficial effects of ketogenic therapy extend beyond epilepsy, neurodegenerative disorders, and brain/spinal cord injury. The KD is broadly effective in improving core behavioral symptoms in animal models of autism spectrum disorder (Ruskin et al, 2013b , 2017a , b ; Ahn et al, 2014 ; Verpeut et al, 2016 ; Castro et al, 2017 ; Dai et al, 2017 ), and in autistic patients (Evangeliou et al, 2003 ; Masino et al, 2011b ; Spilioti et al, 2013 ). The KD is receiving growing interest in oncology as tumors are highly glucose-dependent (the Warburg effect; Seyfried and Mukherjee, 2005 ; Zuccoli et al, 2010 ; Schmidt et al, 2011 ; Klement et al, 2016 ; Lussier et al, 2016 ; Khodadadi et al, 2017 ).…”