Abstract
Background/Objectives: Obesity is increasingly recognized as a global health concern due to its association with metabolic disorders and gut microbiota dysbiosis. While probiotics offer promise in regulating gut microbiota and improving host metabolism, strain-specific effects remain underexplored, particularly for canine-derived probiotics. This study aimed to isolate and characterize a novel probiotic strain, Ligilactobacillus animalis LA-1, and evaluate its anti-obesity effects and underlying mechanisms using a high-fat diet (HFD)-induced obese mouse model. Methods: LA-1 was isolated from the feces of a healthy dog and assessed for probiotic potential in vitro, including gastrointestinal tolerance, bile salt hydrolase activity, cholesterol-lowering capacity, and fatty acid absorption. Male C57BL/6J mice were fed either a standard chow diet or an HFD for 16 weeks, with HFD mice receiving oral LA-1 supplementation (2 × 10(9) CFU/day). Multi-omics analyses, including 16S rRNA gene sequencing, short-chain fatty acid (SCFA) quantification, and untargeted liver metabolomics, were employed to investigate the effects of LA-1 on gut microbiota composition, metabolic pathways, and obesity-related phenotypes. Results: LA-1 supplementation significantly alleviated HFD-induced weight gain, hepatic lipid accumulation, and adipose tissue hypertrophy, without affecting food intake. It improved serum lipid profiles, reduced liver injury markers, and partially restored gut microbiota composition, decreasing the Firmicutes/Bacteroidetes ratio and enriching SCFA-producing genera. Total SCFA levels, particularly acetate, propionate, and butyrate, increased following LA-1 treatment. Liver metabolomics revealed that LA-1 modulated pathways involved in lipid and amino acid metabolism, resulting in decreased levels of acetyl-CoA, triglycerides, and bile acids. Conclusions: L. animalis LA-1 exerts anti-obesity effects via gut microbiota modulation, enhanced SCFA production, and hepatic metabolic reprogramming. These findings highlight its potential as a targeted probiotic intervention for obesity and metabolic disorders.