The content of the direct methyl donor SAM possibly generated from the above elevating gut bacteria was raised, and subsequently increased the methylation degree of specific colonic epithelial genes reportedly associated with RA including Dpep3, Gstm6, Slc27a2, Col11a2, Sycp2, SNORA22, Tnni1, Gpnmb, Mypn and Acsl6, and further inhibited their expressions. The gene discussed is GPNMB; the disease is rheumatoid arthritis.