Lactococcus lactis Subsp. lactis LL-1 and Lacticaseibacillus paracasei LP-16 Influence the Gut Microbiota and Metabolites for Anti-Obesity and Hypolipidemic Effects in Mice.

This study utilized a high-fat diet-induced obese male C57BL/6 mice model to investigate the anti-obesity and lipid-lowering effects of Lactococcus lactis subsp. lactis LL-1 and Lacticaseibacillus paracasei LP-16. A gut microbiota analysis via 16S rRNA sequencing, along with measurements of body weight, lipids, inflammation markers, and gut metabolites, revealed that lactic acid bacteria (LAB) significantly reduced body weight, blood lipid levels, and liver oxidative stress. They also enhanced gut microbiota diversity and evenness, potentially by modulating the Firmicutes/Bacteroidetes ratio to limit excess energy absorption. Malondialdehyde (MDA) showed extremely significant positive correlations with Lachnospiraceae, Blautia, and Colidextribacter, and a significant positive correlation with Helicobacter, while superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) exhibited opposite trends. Specifically, Muribaculaceae, Bacteroides, and Lactobacillus showed negative correlations with MDA levels and positive correlations with SOD and GSH-Px. Short-chain fatty acids (SCFAs) positively correlated with Muribaculaceae, Bacteroides, Mucispirillum, and Lactobacillus, but negatively correlated with Lachnospiraceae, Blautia, Colidextribacter, Alistipes, and Helicobacter. They increased SCFA levels by promoting beneficial bacteria and reducing pathogens, alleviating obesity and hyperlipidemia. Additionally, they regulated the gut microbiota, decreasing bile acids and long-chain fatty acids while increasing SCFAs, short peptides, and vitamins, thereby improving gut metabolic disorders and enhancing host gut health.