This study is a pilot study to evaluate the safety and efficacy of administering butyrate supplement on rheumatoid arthritis patients. Thirty participants will be included to receive butyrate supplement for 12 weeks. Changes of immune cell subtypes, markers of intestinal damage, intestinal flora and other laboratory indicators will be monitored.

This is a single center, uncontrolled, open-label study to assess the efficacy and safety of butyrate supplement plus standard therapy in rheumatoid arthritis(RA). The patients will be given 2 sodium butyrate capsules (containing 1200 mg of sodium butyrate) daily as supplemental therapy. The objective is to assess the effects of 12 weeks of sodium butyrate supplementation on intestinal inflammation and immune regulation in patients with RA, specifically changes in T-cell subtypes and biomarkers associated with intestinal injury. Clinical manifestations and other laboratory indices will also be monitored.

Inclusion Criteria:

• Male or female ≥18 years of age at the time of screening, weight≥35 kg.
• Diagnosed with rheumatoid arthritis satisfying the 1987 American College of Rheumatology classification criteria.
• Stable treatment, including DMARDs (disease-modifying anti-rheumatic drugs) and glucocorticoids, was stable in dose for at least 4 weeks, and no biological agents were used during the first 12 weeks of enrollment.
• Have given written informed consent

Exclusion Criteria:

• Patient presenting or having a history of other autoimmune diseases (such as Sjogren's syndrome, systemic lupus erythematosus, systemic sclerosis, vasculitis, etc.) and other arthritic diseases (such as spinal arthritis, psoriatic arthritis, reactive arthritis, etc.)
• Patient with ongoing or previous Stevens-Johnson syndrome, toxic epidermal necrolysis or erythema multiforme
• Patient with significantly impaired bone marrow function or significant anemia, leucopenia or thrombocytopenia induced by other disease
• Patient with persistent or severe infection within 3 months before enrollment
• Patient with uncontrolled hypertension, uncontrolled diabetes, unstable ischemic heart disease, active inflammatory bowel disease, active peptic ulcer disease, terminal illness or other medical condition which would put the patient at risk of participating in the study according to the opinion of investigator
• Patient with cardiovascular, hepatic, neurological, endocrine, or other major systemic disease, which may make implementation of the protocol or interpretation of the study results difficult
• Patient who has severe hypoproteinemia (e.g., in case of severe liver disease or nephrotic syndrome), with serum albumin < 30 g/L)
• Patient who has moderate or severe impairment of renal function (the estimated glomerular filtration rate was < 60 mL/min/1.73 m2)
• Patient with impairment of liver function or persisting Alanine transaminase (ALT) or Aspartate aminotransferase (AST) elevations of more than 2-fold the upper limit of normal
• Patient with Known HIV positive status or positive serology for hepatitis B or C
• Pregnant or breastfeeding woman
• Women of childbearing potential
• Men wishing to father children during the course of the study or within the 24 months thereafter (or 3 months with the washout procedure)
• Patient with a congenital or acquired severe immuno-deficiency, a history of cancer or lymphoproliferative disease, or any patient who has received total lymphoid irradiation.
• Patient who enrolled in any other clinical trial involving off-label use of an investigational drug or device, or any other type of medical research
• Patient using any biologic agent such as anti-tumor necrosis factor, IL-6 receptor antagonist, anti-CD20 monoclonal antibody within 3 months prior to the first dose of treatment.
• Patient whose BMI (body mass index) is under 18.5 kg/m2 or more than 30 kg/m2
• Patient with history of drug or alcohol abuse