Altered Gut Microbiome Composition in Dogs with Hyperadrenocorticism: Key Bacterial Genera Analysis

Abstract

Hyperadrenocorticism (HAC) is a common endocrine disorder in dogs, which is associated with diverse metabolic abnormalities. We hypothesized that elevated cortisol levels in dogs with HAC disrupt the gut microbiome (GM), and this disruption persists even after trilostane treatment. This study explored GM composition in dogs with HAC. We included 24 dogs, 15 with HAC and 9 healthy controls, and followed up with 5 dogs with HAC who received trilostane treatment. The GM analysis revealed significant compositional changes in dogs with HAC, including reduced microbiome diversity compared to healthy controls, particularly in rare taxa, as indicated by the Shannon index (p = 0.0148). Beta diversity analysis further showed a distinct clustering of microbiomes in dogs with HAC, separating them from healthy dogs (p < 0.003). Specifically, an overrepresentation of Proteobacteria (Pseudomonadota), Actinobacteria, Bacteroides, Enterococcus, Corynebacterium, Escherichia, and Proteus populations occurred alongside a decreased Firmicutes (Bacillota) population. Despite trilostane treatment, gut dysbiosis persisted in dogs with HAC at a median of 41 d post treatment, suggesting its potential role in ongoing metabolic issues. We identified GM dysbiosis in dogs with HAC by examining key bacterial genera, offering insights into potential interventions like probiotics or fecal microbiota transplants for better HAC management.

Keywords: cortisol; dysbiosis; hyperadrenocorticism; hypercortisolism; microbiome; trilostane.

Figure 1

Study design.

Figure 2

Gut microbiome alpha diversity analysis. Boxplot illustrating the differences in gut microbial alpha diversity. (A) The Chao1 index, a richness estimator focused on the total number of species, showed no significant difference between healthy dogs and dogs with HAC (Mann–Whitney test, p = 0.086). (B) In contrast, the Shannon index, which accounts for species richness and evenness, revealed significantly lower diversity in dogs with HAC (Mann–Whitney test, p = 0.0148 *). Boxplots depicting gut microbial alpha diversity before and after trilostane treatment, as measured by (C) the Chao 1 index and (D) the Shannon index, showed no significant differences (Wilcoxon signed-rank test, p > 0.05). Boxes represent the 25th–75th percentile of the distribution, the median is indicated by a thick line in the middle of the box, whiskers extend to 1.5 times the interquartile range, and individual data points are represented as dots. P-values are provided below each graph. HAC, hypercortisolism. * p < 0.05.

Figure 3

Distinct gut microbiome composition in dogs with HAC. Principal coordinate analysis plots demonstrate significant differences in microbial community composition between healthy dogs (n = 9) and dogs with HAC (n = 15) across all three distance metrics: (A) Bray-Curtis, (B) unweighted UniFrac, and (C) weighted UniFrac dissimilarity at the genus level. HAC, hypercortisolism.

Figure 4

There were no significant differences in gut microbiome according to age, diet, sex, or body condition score across all dogs. Principal coordinate analysis with Bray-Curtis distance metrics of the microbiome in dogs across various categories-(A) age, (B) diet, (C) sex, and (D) BCS-revealed no significant differences. R/C, Royal Canin; CM, castrated male; IF, intact female; SF, spayed female; BCS, body condition score.

Figure 5

Gut microbiome composition remains stable in dogs with HAC after trilostane treatment. Principal coordinate analysis plots show no significant differences in microbial community composition of dogs with HAC pre- and post treatment (n = 5) across all three-distance metrics: (A) Bray-Curtis, (B) unweighted UniFrac, and (C) weighted UniFrac dissimilarity at the genus level (PERMANOVA, p > 0.05). HAC, hypercortisolism.

Figure 6

Comparison of microbiome taxa in healthy dogs (n = 9) and dogs with HAC (n = 15) at the phylum level. (A) A stacked bar graph showing the mean relative abundance of the gut microbiome at the phylum level. (B) Dogs with HAC have a significantly higher relative abundance of Proteobacteria and significantly lower levels of Firmicutes, with a significant increase in Actinobacteria compared to healthy controls. HAC, hypercortisolism.

Figure 7

Comparison of microbiome taxa in healthy dogs (n = 9) and dogs with HAC (n = 15) at the genus level. (A) A stacked bar graph showing the mean relative abundance of the gut microbiome at the genus level. (B) Dogs with HAC show significantly higher levels of Bacteroides, Enterococcus, Corynebacterium, Escherichia, and Proteus compared to healthy controls. HAC, hypercortisolism.

Figure 8

Analysis of bacterial communities in dogs with HAC before and after trilostane treatment. A stacked bar graph showing the mean relative abundance of the gut microbiome. At the phylum (A) and genus (B) levels, no significant changes were observed (DESeq2, p > 0.05). (C) Stacked bar plot of the 10 most abundant genera in HAC treatment dogs (n = 5). The mean relative abundance profiles of individual microbiomes before and after treatment are shown in sets, with no discernible trend between pre-treatment (left) and post-treatment (right) compositions. HAC, hypercortisolism.