Clinical implications of milk fat globule-epidermal growth factor 8 (MFG-E8) and vitamin D levels in patients with rheumatoid arthritis and primary knee osteoarthritis

Abstract

Aimof the work to determine serum levels of vitamin D and Milk fat globule-epidermal growth factor 8 (MFG-E8) in rheumatoid arthritis (RA) and primary knee osteoarthritis (OA) compared to healthy controls and their possible associations. Patients and methods: The study included 30 RA and 30 primary knee OA patients as well as 25 control. The disease activity was measured by disease activity score 28 (DAS28) in RA. The functional status was estimated by Western Ontario and McMaster Universities index (WOMAC index) in OA. While the assessment of pain was measured by the visual analog scale (VAS) in both RA and OA. Serum vitamin D and MFG-E8 levels were measured using enzyme-linked immunosorbent assay (ELISA). Results: The mean age of RA patients was 41.1 ± 9.2 years; 25 females and 5 males (F:M 5:1) and a disease duration of 6.9 ± 4.6 years. The mean age of OA patients was 48.7 ± 8.3 years; 28 females and 2 males (F:M 14:1) and disease duration was 5.4 ± 3.3 years. The mean vitamin D was significantly lower in RA (9.7 ± 5.04 ng/ml) than OA (16.4 ± 4 ng/ml) and controls (17.7 ± 3.4 ng/ml), p < 0.0001. The mean MFG-E8 serum level was significantly lower in RA and OA patients (4.9 ± 2.4 ng/mland 5.3 ± 1.2 ng/ml) than in controls (9.1 ± 3 ng/ml), p < 0.0001.Vitamin D significantly correlated with MFG-E8 (r = 0.6, p = 0.002) in RA and both inversely correlated with DAS28 (r = -0.66, p < 0.0001 and r = -0.58, p < 0.0001 respectively). Vitamin D (9.7 ng/ml) and MFG-E8 (4.9 ng/ml) significantly predicted RA (p < 0.0001) at specificity (100%) and sensitivity (66.7%). MFG-E8 at cut-off 5.3 ng/ml significantly predicted OA at specificity of 88% and sensitivity 86.7%.Conclusion: An association between low serum vitamin D and MFG-E8 levels with RA and the disease activity has been determined. Low MFG-E8 was associated with OA.