Effects of short-chain fatty acid on thyroid function and intestinal flora structure in mice with Graves’ disease

Objective To evaluate the effects of short-chain fatty acid (SCFA) on the pathological changes of thyroid and colon tissues, SCFA content in stool metabolism and intestinal flora of Graves’ disease mice by using the mouse model of Graves’ disease.Methods Graves’ disease mouse model was constructed and randomly divided into Graves’ disease model control group and SCFA intervention group after success, and the mice were compared with the blank control group. After 2 weeks of intervention with exogenous SCFA mixture, blood and tissue samples of mice in each group were collected. The pathological changes of thyroid gland and colon were observed by HE staining. The contents of thyroid stimulating hormone, free thyroxine and thyroid stimulating antibodies in serum were determined by enzyme-linked immunosorbent assay (ELISA). The content of SCFA in feces was determined by gas chromatography. Intestinal flora of mice was detected by 16S rRNA technique.Results Compared with mice in the control group of Graves’ disease model, the serum TSH levels of mice in the SCFA intervention group were increased, and the levels of TSAb and FT4 were decreased. The contents of acetic acid, propionic acid, butyric acid, isobutyric acid and isovaleric acid in the stool of mice in the SCFA intervention group were significantly increased, and the differences were statistically significant (P<0.05). The analysis of intestinal flora structure of the three groups of mice showed that at the phylum level, the dominant phyla were Bacteroidota, Firmicutes and Proteobacteria. Compared with GD model group, the intestinal microbiota of mice in the SCFA intervention group showed an increase in Turicibacter. LEfSe analysis showed that the concentration of Rosebutia was the highest in Graves’ disease model group. The enrichment of Faecalibaculum was the highest in the SCFA intervention group.Conclusions After intervention for 2 weeks, SCFA can alleviate the abnormal changes of thyroid function indexes, and improve the pathological changes of thyroid and colon tissues in GD model mice. The intestinal flora of GD model mice showed characteristic changes, but exogenous SCFA intervention had no significant effect on the intestinal flora of GD model mice.