Probiotic interventions with highly acid-tolerant Levilactobacillus brevis strains improve lipid metabolism and gut microbial balance in obese mice†

Abstract

Many studies have shown that specific lactic acid bacteria (LAB) strains can delay obesity, offering a viable alternative to medications and surgeries. However, the mining and development of highly effective LAB strains for obesity control is still limited. In this study, the naturally highly acid-tolerant and gamma-aminobutyric acid-producing Levilactobacillus brevis D17 and its glnR deletion strain were used to investigate their anti-obesity effects. In an 8-week mouse experiment, L. brevis D17 and its glnR-deletion strain D17ΔglnR significantly reduced weight gain by 28.4% and 29.1%, respectively, improving abnormal serum indicators and glucose metabolism caused by a high-fat diet. Furthermore, L. brevis D17 and its glnR-deletion strain D17ΔglnR successfully colonized in the gut. Both D17 and D17ΔglnR interventions significantly restored the relative abundance of Muribaculaceae, Ileibacterium valens, Lactobacillus, Faecalibaculum, Bifidobacterium globosum, Akkermansia muciniphila, and Romboutsia ilealis, whereas they significantly reduced potentially harmful bacteria like Leptogranulimonas, Flintibacter, and Alistipes. Additionally, L. brevis intervention effectively decreased the levels of primary bile acids and increased secondary bile acids in the gut, thus balancing bile acid metabolism. The transcriptional analysis suggested that D17 and D17ΔglnR interventions may activate the AMPK signaling pathway in the liver to inhibit lipogenesis, activate the cAMP pathway to promote lipolysis, and inhibit pro-inflammatory macrophage infiltration to block inflammatory responses. These results indicate that L. brevis D17 and its glnR-deletion mutant strain D17ΔglnR show great potential in combating obesity. Moreover, these results also provide insights into the underlying mechanism behind their anti-obesity properties.