Streptococcus thermophilus alleviates fatty liver disease by regulating gut microbiota, lipid metabolism, and inflammation.

Alcoholic fatty liver disease (AFLD) is a liver disease caused by long-term excessive alcohol consumption, and there remains no effective treatment beyond alcohol abstinence. Streptococcus thermophilus (S. thermophilus), a traditional probiotic, is widely used in yogurt and other fermented dairy products. This study investigated the therapeutic effects of S. thermophilus in AFLD mice. The results demonstrated that S. thermophilus significantly reduced serum ALT and AST levels, improving liver function. It also regulates PPAR signaling pathway-related genes, reduces serum TG and T-CHO levels, and alleviates hepatic lipid accumulation. Additionally, S. thermophilus intervention effectively restored gut microbiota dysbiosis, improved microbial diversity and richness, and increased the abundance of beneficial bacteria such as Akkermansia muciniphila. Furthermore, S. thermophilus also inhibited the TLR4/NF-κB pathway, reducing the release of pro-inflammatory factors such as TNF-α and IL-1β and alleviating liver inflammation. Overall, these findings indicate that S. thermophilus can improve gut microbiota disorders, suppresses PPAR-γ and TLR4 expression, reduces hepatic lipid accumulation and inflammation, and thus ameliorates AFLD.