This study is a study to evaluate the safety and efficacy of administering niacin sustained-release capsules to rheumatoid arthritis with hyperlipidemia patients. Sixty patients were randomly assigned to niacin or placebo for 12 weeks, followed by niacin for 12 weeks. Changes in disease activity score, immune cell subtypes, markers of intestinal damage, intestinal flora, and other laboratory indicators will be monitored.

In this study, a randomized double-blind placebo study was conducted to treat patients with rheumatoid arthritis (RA) complicated with dyslipidemia with niacin sustained-release capsules. This study intends to include 60 patients, who are randomly divided into the control group and niacin group in a 1:1 ratio. With the basic treatment of RA unchanged, the administration plan of the two groups is as follows: divided into two stages, the first stage: the niacin group is given a niacin sustained-release capsule orally for 3 months, and the control group is given a placebo orally for 3 months. The second stage: Both groups were given niacin sustained-release capsules for 3 months.The primary endpoint was the change of immune cell subsets, which clarified the immunomodulatory effect of niacin. The secondary end point was to observe the changes in blood lipid, improvement of joint symptoms, effect on intestinal barrier, the effect on intestinal flora, and safety of taking niacin sustained-release capsules.

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 or ACR/EULAR 2010 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.
• Dyslipidemia (5.2≤TC≤7.2mmol/L, 3.4≤LDL-c≤4.9mmol/L or 1.7≤TG≤5.1 mmol/L)
• Have given written informed consent.

Exclusion Criteria:

• a. Patients with other autoimmune diseases (such as systemic lupus erythematosus, Sjogren's syndrome, ankylosing spondylitis, etc.).
• b. Patients with uncontrolled hyperuricemia and gout.
• c. Patients who take lipid-lowering drugs such as statins or fibrates orally, cardiovascular medications (such as aspirin, nitrates, calcium channel blockers, epinephrine blockers).
• d. Patients with Stevens-Johnson syndrome, toxic epidermal necrolysis, or multiple erythema.
• e. Patients with significantly impaired bone marrow function or significant anemia, leukopenia, or thrombocytopenia, excepting those secondary to active rheumatoid arthritis.
• f. Persistent or severe infection within 3 months prior to enrollment.
• g. Uncontrolled high blood pressure, diabetes, atherosclerotic cardiovascular disease, inflammatory bowel disease, peptic ulcer and other digestive diseases, end-stage diseases, or diseases that investigators believe would put patients at risk for study participation.
• h. Clinically relevant cardiovascular, liver, neurological, endocrine, or other major systemic disease that makes the implementation of the protocol or the interpretation of the findings difficult.
• i. Severe liver and kidney function impairment (severe hypoproteinemia with serum albumin <30g/L, elevated aminotransferase more than 2 times the upper limit of normal, moderate or severe renal function impairment, such as creatinine >133 μ/L, etc.).
• j. Patients with a recent and clinically severe history of drug or alcohol abuse.
• k. Pregnant.
• l. Breastfeeding.
• m. Subjects who wish to become fathers during the study or within 24 months (or 3 months washout period) after the study;
• n. Patients with congenital or acquired severe immunodeficiency, a history of cancer or lymphoproliferative disease, or patients who have received total lymphoid radiation.
• o. Known HIV-positive status.
• p. Patients with known hepatitis B or hepatitis C positive serology and patients with hepatobiliary diseases such as chronic active liver disease.
• q. Use any biologics, such as anti-tumor necrosis factor, abaxipril, tuximab, or rituximab, within 3 months prior to the first dose.
• r. Enroll in any other clinical trial involving the off-label use of investigational drugs or devices, or enroll in any other type of medical research.
• s. Body mass index (BMI) less than 18.5kg/m2 or greater than 30 kg/m2.