Ketogenic Diet Induced Shifts in the Gut Microbiome Associate with Changes to Inflammatory Cytokines and Brain-Related miRNAs in Children with Autism Spectrum Disorder.

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• Given the impact of neuro-inflammation on metabolic pathways, gut microbiome and ASD patients’ social behaviour, an anti-inflammatory diet is an important consideration for this cohort.
• Supplementation options such as butyric acid might also be considered given its effect on inflammation, gut dysbiosis, and BDNF.

Introduction

This children’s interventional pilot study evaluated the change in inflammatory markers that has consistently been shown to be elevated in individuals within the autism spectrum disorder (ASD) following a ketogenic dietary (KD) intervention. The study furthermore assessed gut microbiome composition given that gastrointestinal problems have additionally been shown to be notable in this cohort.

Methods

The initial cohort included 47 children (aged 7-19 years). Analysis was based on 11 children’s non-fasting blood samples and 7 children’s at-home collected stool samples. Samples were collected pre-and post a 4-month KD intervention that included daily medium-chain triglyceride (MCT) oil supplementation with carbohydrate intake restricted to 20-25 g/day and protein intake based on weight and age of each participant. There was no clearly defined targeted level of ketosis to be maintained. Blood plasma was used both in ketone body- and 14-plex cytokine Luminex assays. Stool samples were subjected to DNA and RNA isolation using 16S sequencing and BUK/BAC qPCR assays.

Results

• The authors noted a significant increase in concentrations of acetoacetic acid (by 0.97 nM ± 0.66; p = 0.02) and hydroxybutyric acid (by 0.63 nM ± 0.38; p = 0.02) ketone bodies.
• Significant bacterial changes included Lactobacillales order (p = 0.02), Bacteroidaceae family (p = 0.03), Oscillospiraceae family (p = 0.04), Ruminococcus genus (p = 0.04), Bacteroides genus (p = 0.03), Ruminococcus gnavus (p = 0.03), and Clostridium cocleatum (p = 0.04).
• Additional observations included significantly decreased plasma levels of brain-derived neurotrophic factor (BDNF). Observed changes in miRNAs that have been linked with BDNF regulation in the brain included significant reduction of miR-134 (p = 0.008) and miR-132 (p = 0.027).

Conclusion

A KD may directly target brain activity via its effect on metabolic pathways, particularly those that impact on sociability in ASD patients. This children’s study showed that a short KD intervention can reduce certain inflammatory markers and furthermore improve gut microbiome composition whilst also increasing the production of butyrate. Butyrate is shown to reduce inflammation through its effect on cytokines, neurotransmitters, and miRNAs associated with BDNF.

• A comprehensive stool analysis should be considered for any ASD suggested dietary intervention protocol to assess the specific needs of the individual in terms of gut microbiome status.
• A carefully balanced KD or at least a gluten-free diet should be considered for ASD individuals to address inflammation and gut microbiome dysbiosis shown to be elevated in ASD patients.

• Larger studies are needed to elicit whether a KD should form part of a standardised treatment protocol for ASD individuals.
• Cohorts need to include an even distribution between age and sex to determine the effect of a KD on both neuro-inflammatory and gut microbiome markers for the individual.
• The direct impact on improvement of social behaviour in ASD individuals following a KD requires further investigation.