Obesity is a major public health concern in both humans and animals, leading to several metabolic complications. Recent human studies have classified obesity into two phenotypes, metabolically healthy (MHO) and metabolically unhealthy (MUO) obesity based on cardiovascular and metabolic risk factors. MHO cases lack these risk factors and are protected from metabolic complications of obesity, whereas MUO cases exhibit the opposite characteristics. Moreover, recent studies have highlighted the possible role of the gut microbiome in determining metabolic health of obese individuals. However, studies on the association between the gut microbiome and obesity and metabolic abnormalities in cats are limited. Therefore, we aimed to examine the association between metabolic health phenotypes and gut microbiota composition and diversity in obese cats. We investigated hormone and serum biochemistry parameters and composition of the gut microbiota in non-obese (NO), MHO, and MUO groups. The abundances of Bifidobacteriaceae, Coriobacteriaceae, and Veillonellaceae were significantly higher in the obese versus NO group, showing a positive correlation with body mass index. The abundance of Ruminococcaceae was significantly higher in the MUO versus NO group, showing a positive correlation with triglyceride and total cholesterol levels. However, obesity, whether MHO or MUO, had only a minimal impact on fecal microbiota. Therefore, further studies are warranted to investigate whether gut microbiota could be a beneficial tool for the treatment or management of this condition.

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.