Previous study found that lipid extract from hard-shelled mussel (HMLE) at a dose of 100mg/kg possessed strong anti-inflammatory activity by diminishing the hind paw swelling and arthritis index in rat model. In the present study, HMLE was processed to capsules under strict food safety supervision and patients with active rheumatoid arthritis (RA）were selected to examine whether supplementation with HMLE could improve clinical and laboratory parameters of disease activity. The validated disease activity score that include 28 joint counts and ESR (DAS28) and validated clinical disease activity index (CDAI) were primary outcome measure. Laboratory parameters including IL-1β, IL-6, IL-10, TNF-α,PGE2 and COX-2 were also measured to explore the mechanisms.

In this randomized controlled design, patients continued receiving background medications (slow-acting anti-rheumatic drugs and non-steroidal anti-inflammatory drugs) without change and were assigned to two groups. The first group (G1) received daily four mussel oil capsules (containing 800mg mussel oil and 800mg corn oil) for first two months and two mussel oil capsules per day thereafter. The second group (G2) received corn oil capsules (400mg corn oil per capsule) according to the same regimen. All patients were asked to keep a 7-day food diary before intervention and during wk 12. Dietary energy and nutrient intake of each subject during the preexperimental and study period were assessed from the dietary records by using "Diet Analysis" software (Cao Aihong, Taiyuan, China). All the enrolled patients visited Zhejiang Sir Run Run Shaw Hospital in the morning following an overnight fast at baseline and 3-month intervals, and underwent anthropometric measurements including height, body weight, waist circumference, hip circumference, heart rate and blood pressure. Then clinical evaluations were performed during face-to-face interview by a professional attending doctor and ten milliliter of peripheral venous blood was drawn. Serum and erythrocyte samples were also promptly processed and frozen at -80℃ until analysis.

Inclusion Criteria:

• According to the American College of Rheumatology criteria, patients from Zhejiang province with active RA were included in this study and all participants were Chinese. Patients had at least 3 swollen joints and 6 tender joints or had an erythrocyte sedimentation rate (ESR) of >28mm/hr or morning stiffness of at least 45 min were classified as with active disease.

Exclusion Criteria:

• Subjects suffering hyperlipidemia, hyperglycemia, diabetes mellitus, cardiovascular diseases, gastrointestinal problems, liver and renal failure.