Berberine ameliorates ovariectomy-induced anxiety-like behaviors by enrichment in equol generating gut microbiota

The gut microbiota is recognized as a promising therapeutic target for anxiety. Berberine (BBR) has shown efficacy in the treatment of diseases such as postmenopausal osteoporosis, obesity, and type 2 diabetes through regulating the gut microbiota. However, the effects of BBR on postmenopausal anxiety are still unclear. The purpose of the study is to test whether BBR ameliorates anxiety by modulating intestinal microbiota under estrogen-deficient conditions. Experimental anxiety was established in specific pathogen-free (SPF) ovariectomized (OVX) rats, which were then treated with BBR for 4 weeks before undergoing behavioral tests. Open field and elevated plus maze tests demonstrated that BBR treatment significantly ameliorated anxiety-like behaviors of OVX rats compared with vehicle-treated counterparts. Moreover, as demonstrated by 16S rRNA sequencing and liquid chromatography/mass spectrometry (LC/MS) analysis, BBR-treated OVX rats harbored a higher abundance of beneficial gut microbes, such as Bacteroides, Bifidobacterium, Lactobacillus, and Akkermansia, and exhibited increased equol generation. Notably, gavage feeding of BBR had no significant anti-anxiety effects on germ-free (GF) rats that underwent ovariectomy, whereas GF rats transplanted with fecal microbiota from SPF rats substantially phenocopied the donor rats in terms of anxiety-like symptoms and isoflavone levels. This study indicates that the gut microbiota is critical in the treatment of ovariectomy-aggravated anxiety, and that BBR modulation of the gut microbiota is a promising therapeutic strategy for treating postmenopausal symptoms of anxiety.