Association of serum renalase with disease activity in lupus nephritis

Abstract

Objective To investigate the relationship between serum renalase and disease activity in lupus nephritis (LN). Methods Total of 70 patients with LN and 35 healthy volunteers admitted in Renji Hospital of Shanghai Jiao Tong University from March 2012 to March 2013 were enrolled in the study. LN patients were classified into two groups according to their systemic lupus erythematosus disease activity index (SLEDAI) scores: patients with SELDAI score lower than 8 were defined as inactive LN while others were defined as active LN. Serum samples were collected after an overnight fast and serum renalase level was determined by ELISA. Twenty active LN patients were followed up for six-months, and serum renalase was also determined before and after treatment. The differences in serum renalase level between LN patients and healthy controls were assessed, as well as the association of serum renalase with disease activity in LN. Results In 70 LN patients, 35 were classified active LN while others were inactive LN. Serum renalase level was significantly higher in LN patients than than in healthy controls (P<0.01). Moreover, active LN patients had higher serum renalase level compared to patients with inactive LN (P<0.01). Active LN patients had higher 24-hour urine protein excretion, erythrocyte sedimentation rate and anti-dsDNA antibody titers than inactive LN patients. Serum albumin was lower in inactive LN patients compared to active LN patients. There were no differences in gender, age, blood pressure and C-reactive protein between the two groups. Serum renalase levels were positively correlated with SLEDAI, 24-hour urine protein excretion, ds-DNA and ESR but inversely correlated with serum albumin and C3. Renalase amounts decreased significantly after six-months of standard therapy. The performance of renalase as a marker for diagnosis of active LN was 0.894 with a cutoff value of 66.67 mg/L. Logistic regression showed that serum renalase (OR=1.078, 95%CI 1.031-1.120, P=0.001) and complement C3 (OR=0.022, 95%CI 0.002-0.326, P=0.005) is independent indicators for disease activity in LN. Conclusions Serum renalase level was correlated with disease activity in LN. Serum renalase may serve as a potential indicator for disease activity in LN. Key words: Lupus nephritis; Disease activity; Renalase