Zhaowei Huang,1,2,* Changming Chen,3,* Linlin Tan,4 Yi Ling,3 Wukai Ma,3 Jinan Zhang1,2 

1Graduate School, Shanghai University of Traditional Chinese Medicine, Shanghai, People’s Republic of China; 2Department of Endocrinology & Rheumatology, Shanghai University of Medicine & Health Sciences Affiliated Zhoupu Hospital, Shanghai, People’s Republic of China; 3Department of Rheumatology & Immunology, The Second Affiliated Hospital of Guizhou University of Chinese Medicine, Guiyang, Guizhou, People’s Republic of China; 4Department of Internal Medicine, Jinshazhou Hospital Affiliated to Guangzhou University of Chinese Medicine, Guangzhou, Guangdong, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Jinan Zhang, Email zhangjinan@hotmail.com

Background: Rheumatoid arthritis (RA) is a common autoimmune disease with the main symptoms being joint swelling and pain. In severe cases, joint deformity or even complete loss of function occurs. Technetium methylene diphosphonate (99Tc-MDP) is widely used for RA treatment in China, but there are no studies on the effects of 99Tc-MDP on intestinal flora.
Objective: To explore the effects of 99Tc-MDP treatment on the composition and function of the intestinal flora and to provide new information on the mechanism of 99Tc-MDP in RA treatment.
Methods: Stool samples from RA patients before and after 99Tc-MDP treatment were collected to form two groups (Before and After). Total genomic DNA of the samples was extracted for 16S rRNA gene sequencing. The altered composition of the intestinal flora, the key target bacteria regulated by 99Tc-MDP, and the pathways of action of 99 Tc-MDP were analyzed by bioinformatics.
Results: A total of 64 fresh stool samples were collected from 32 RA patients. Compared to the Before group, the After group showed increased Bacteroidetes abundance and decreased Firmicutes abundance. At the genus level, Prevotella increased whereas Escherichia decreased. Both α and β diversity analyses showed that 99Tc-MDP treatment did not affect gut microbial diversity in RA patients. LEfSe analyses and random forest analyses showed Bacteroidetes, Prevotella, Enterococcus, Escherichia and Ruminococcaceae were the main 99Tc-MDP regulating bacteria. Functional enrichment analysis revealed that the functional differences in gut flora of the two groups centered on Metabolism and Genetic Information Processing.
Conclusion: This study revealed differences in the composition of the gut microbiota in RA patients before and after 99Tc-MDP treatment. The therapeutic effect of 99Tc MDP is mainly achieved through Bacteroidetes, Prevotella, and Enterococcus. Regulating metabolism and genetic information processing of gut flora may be the mechanism of 99Tc-MDP in treating RA.

Keywords: rheumatoid arthritis, 99Tc-MDP, gut microbiota, 16S rRNA, bioinformatics