Abstract
Rosmarinus officinalis (rosemary) is widely used as a food ingredient. Rosemary extract (containing 40% carnosic acid) exhibited potent antiobesity activity. However, the relationship between carnosic acid (CA) and changes in the gut microbiota of high-fat diet (HFD)-induced obese mice has not been fully investigated. C57BL/6 mice were fed a normal diet, an HFD, or an HFD containing 0.1% or 0.2% CA for 10 weeks. CA exhibited promising antiobesity effects and caused marked alterations in the gut microbiota of HFD-induced obese mice. CA caused the prevalence of probiotics and functional bacteria, including Akkermansia muciniphila, Muribaculaceae unclassified, and Clostridium innocuum group, and inhibited diabetes-sensitive bacteria, including Proteobacteria and Firmicutes. The ratio of Firmicutes to Bacteroidetes was regulated by CA in a dose-dependent manner, decreasing it from 13.22% to 2.42%. Additionally, CA reduced bile acid-metabolizing bacteria, such as Bilophila, Clostridium, Lactobacillus, and Leuconostoc. The results of the linear discriminant analysis and effect size analysis indicated that CA attenuated the microbial changes caused by HFD. The high CA (HCA) group (HFD containing 0.2% CA) exhibited a greater abundance of Verrucomicrobiae (including Akkermansia muciniphila, genus Akkermansia, family Akkermansiaceae, and order Verrucomicrobiales), Eubacterium, and Erysipelatoclostridium, and the low CA (LCA) group (HFD containing 0.1% CA) exhibited a greater abundance of Eisenbergiella, Intestinimonas, and Ruminococcaceae. Our results demonstrate that the antiobesity effects of CA might be strongly related to its prebiotic effects.