Pediococcus acidilactici PA-1 Alleviates Diet-Induced Obesity by Modulating Hepatic Amino Acid Metabolism and Gut Microbiota in Mice.

Obesity and type 2 diabetes mellitus are global health challenges often associated with disrupted lipid and amino acid metabolism, as well as gut microbiota dysbiosis. Probiotic interventions offer promising potential in ameliorating metabolic disorders, yet strain-specific mechanisms remain to be elucidated. In this study, a canine-derived Pediococcus acidilactici PA-1 was subjected to in vitro evaluation for probiotic properties, and its anti-obesity effects were investigated in high-fat diet (HFD)-induced obese mice. In vitro, PA-1 exhibited safety and favorable probiotic activity including gastrointestinal tolerance, adhesion potential, bile salt hydrolase activity, α-glucosidase inhibition and fatty acid absorption. In vivo, PA-1 supplementation significantly alleviated body weight gain, hepatic steatosis, and lipid accumulation in HFD-fed mice. Multi-omics analyses of liver revealed that PA‑1 modulated hepatic amino acid metabolism at the pathway level (e.g., alanine, aspartate and glutamate metabolism), and led to significant decreases in D‑serine, glycine, and L‑proline in the targeted panel, whereas several others (e.g., L‑aspartate, L‑alanine) showed trend-level decreases. PA‑1 concomitantly suppressed pyruvate flux into the TCA cycle and reduced several TCA intermediates (e.g., fumarate, malate, citrate), eventually Limiting acetyl-CoA availability for de novo Lipogenesis. Additionally, 16S rRNA sequencing demonstrated that PA-1 reshaped the gut microbiota by reducing the Firmicutes/Bacteroidota ratio and enriching the abundance of short-chain fatty acid-producing genera, leading to elevated SCFA concentrations in the cecal contents. This study suggests that PA-1 ameliorates HFD-induced obesity and metabolic disturbances by modulating hepatic amino acid metabolism and gut microbiota composition, highlighting its potential as a functional probiotic for managing obesity-related metabolic disorders.