The Effects of a Ketogenic Medium-Chain Triglyceride Diet on the Feces in Dogs With Idiopathic Epilepsy

Abstract

Consumption of diets containing medium chain triglycerides have been shown to confer neuroprotective and behavior modulating effects. We aimed to identify metabolic and microbiome perturbations in feces that are associated with consumption of a medium chain triglyceride ketogenic diet (MCT-KD) in dogs with idiopathic epilepsy. We used 16S rRNA gene sequencing to generate microbiome profiles and ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) to generate lipidomic profiles of canine feces. We made comparisons between the MCT-KD, standardized placebo diet and baseline pre-trial diet phases. Consumption of the MCT-KD resulted in a significant increase in the species richness (α-diversity) of bacterial communities found in the feces when compared to the baseline diet. However, phylogenetical diversity between samples (beta-diversity) was not affected by diet. An unnamed Bacteroidaceae species within genus 5-7N15 was identified by LEfSe as a potential biomarker associated with consumption of the MCT-KD, showing an increased abundance (p = 0.005, q = 0.230) during consumption of MCT-KD. In addition, unclassified members of families Erysipelotrichaceae (p = 0.013, q = 0.335) and Fusobacteriaceae (p = 0.022, q = 0.358) were significantly increased during MCT-KD consumption compared to baseline. Blautia sp. and Megamonas sp. instead were decreased during consumption of either placebo or MCT-KD (p = 0.045, q = 0.449, and p = 0.039, q = 0.449, respectively). Bacteroidaceae, including genus 5-7N15, have previously been associated with non-aggressive behavior in dogs. In addition, 5-7N15 is correlated in humans with Akkermansia, a genus known to be involved in the neuroprotective effect of ketogenic diets in mice models of seizures. Five metabolite features, tentatively identified as long chain triglycerides, were significantly higher after consumption of the placebo diet, but no unique features were identified after consumption of the MCT-KD. The data presented in this study highlight significant changes shown in both the fecal microbiome and lipidome as a result of consumption of the MCT-KD. Elucidating the global canine gut response to MCT consumption will improve our understanding of the potential mechanisms which confer anti-seizure and behavior modulating effects. Further studies should aim to characterize the gut microbiome of both dogs with epilepsy and healthy controls.

Keywords: dogs; epilepsy; ketogenic diet; medium-chain triglyceride; microbiome.

Figure 1

Effect of the medium-chain TAG ketogenic diet (MCT-KD) on (A) seizure frequencies per month (P = 0.148) and (B) seizure days per month (P = 0.054) compared with the placebo-standardized diet (n = 11). Data are shown as box-and-whisker plots (central lines of the box represent the median, lower and upper limits of the box represent the 25th and 75th percentiles and whiskers represent the minimum and maximum). Two-sided Wilcoxon's matched-pairs rank tests were used to compare placebo and MCTD groups.

Figure 2

Effects of the medium chain triglyceride diet (MCT-KD) on concentrations of β-hydroxybutyrate (BHB). BHB concentrations were measured after dogs (n = 11) were fed the MCT-KD for a period 90 ± 2 days and the placebo diet for a period 90 ± 2 days. Figure shows a respective increase in BHB levels when dogs were on the MCT-KD in comparison to the placebo diet (p = 0.0498). Data are shown as scatter plot (central line represent mean with standard deviations). Two-sided matched paired students t-test was used to compare the placebo and MCT-KD group.

Figure 3

Alpha diversity indices Observed species (A), Chao1 (B), and Shannon (C), measured before (normal) and after diet trial with placebo or MCT-KD diets. Red bars indicate the median, red asterisk indicates significance (p < 0.05) compared to baseline.

Figure 4

Principal Coordinates Analysis (PCoA) of unweighted (A) and weighted (B) UniFrac distances. Blue circles indicate baseline samples, gray squares indicate samples collected after placebo diet consumption, and red diamonds indicate samples collected after MCT-KD diet consumption.

Figure 5

Relative abundance of the most relevant species affected by diet: 5-7N15 sp. (A) was increased by MCTD, while Blautia sp. (B) and Megamonas sp. (C) showed a trend toward decrease by both the placebo and MCTD diets. Overall p- and q-values are indicated in the graphs, red bars indicate median.

Figure 6

Principal components analysis (PCA) scores plot showing fecal data acquired by lipid profiling UPLC-MS. Scores represent samples belonging to MCT-KD, Placebo and pre-trial baseline samples. Key: t[1], principal component (PC) 1; t[2], principle component 2; R2X[1], PC1 variation within variables modeled; R2X[2], PC2 variation within variables modeled; MCT-KD, medium chain triglyceride ketogenic diet.