Associations of serum citrate levels with knee structural changes and cartilage enzymes in patients with knee osteoarthritis.

OBJECTIVE: The aim of this study was to investigate cross-sectional associations between serum levels of citrate and knee structural changes and cartilage enzymes in patients with knee osteoarthritis (OA). METHOD: A total of 137 subjects with symptomatic knee OA (mean age 55.0 years, range 34-74, 84% female) were included. Knee radiography was used to assess knee osteophytes, joint space narrowing (JSN) and radiographic OA assessed by Kellgren-Lawrence (K-L) grading system. T2-weighted fat-suppressed fast spin echo magnetic resonance imaging (MRI) was used to determine knee cartilage defects, bone marrow lesions (BMLs) and infrapatellar fat pad (IPFP) signal intensity alternations. Colorimetric fluorescence was used to measure the serum levels of citrate. Enzyme-linked immunosorbent assay was used to measure the serum cartilage enzymes including matrix metalloproteinase (MMP)-3 and MMP-13. RESULTS: After adjustment for potential confounders (age, sex, body mass index), serum citrate was negatively associated with knee osteophytes at the femoral site, cartilage defects at medial femoral site, total cartilage defects, and total BMLs (odds ratio [OR] 0.17-0.30, all P < .05). Meanwhile, serum citrate was negatively associated with IPFP signal intensity alteration (OR 0.30, P = .05) in multivariable analyses. Serum citrate was significantly and negatively associated with MMP-13 (ß -3106.37, P < .05) after adjustment for potential confounders. However, citrate was not significantly associated with MMP-3 in patients with knee OA. CONCLUSION: Serum citrate was negatively associated with knee structural changes including femoral osteophytes, cartilage defects, and BMLs and also serum MMP-13 in patients with knee OA, suggesting that low serum citrate may be a potential indicator for advanced knee OA.

Associations between serum IL-8 and knee symptoms, joint structures, and cartilage or bone biomarkers in patients with knee osteoarthritis.

OBJECTIVE: The aim of this study was to investigate cross-sectional associations between serum levels of IL-8 and the above outcomes in patients with knee osteoarthritis (OA). METHODS: A total of 160 subjects with clinical knee OA were included. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score and Lequesne index were used to assess the joint symptom. Magnetic resonance imaging was used to measure knee structural abnormalities including infrapatellar fat pad (IPFP) signal intensity alternation. Knee radiographic OA was assessed by radiography using the Kellgren-Lawrence (K-L) grading system. Enzyme-linked immunosorbent assay was used to measure the serum levels of IL-8 and cartilage or bone biomarkers. RESULTS: In multivariable analyses, serum IL-8 was positively associated with WOMAC weight-bearing pain (ß 2.85, P = 0.028), WOMAC physical dysfunction (ß 12.71, P = 0.048), and Lequesne index (ß 1.65, P = 0.015), and had positive associations with IPFP signal intensity alteration (OR 3.18, P = 0.011) and serum levels of N-telopeptide of type I collagen (NTXI), N-terminal procollagen III propeptide (PIIINP), matrix metalloproteinase (MMP)3, and MMP13 (ß 0.24-1.44, all P < 0.05) in patients with clinical knee OA. Furthermore, there were positive associations between IL-8 and WOMAC score (ß 22.49, P = 0.037), K-L grades (OR 3.88, P = 0.013), and IPFP signal intensity alteration (OR 3.20, P = 0.033) in patients with radiographic OA. CONCLUSIONS: Serum levels of IL-8 were positively associated with increased knee symptoms, IPFP signal intensity alteration, and serum levels of bone and/or cartilage biomarkers, suggesting that IL-8 may have a role to play in knee OA.Key Point• This study systemically investigates the associations between serum IL 8 and knee symptoms, joint structures, and cartilage or bone biomarkers in patients with knee osteoarthritis, and some significant associations have been found, suggesting that IL 8 may have a role to play in knee OA.