Circulating nicotinamide adenine dinucleotide-ubiquinone oxidoreductase chain 6 is associated with disease activity of anti-neutrophil cytoplasmic antibody-associated vasculitis.

BACKGROUND Increased serum and urinary mitochondrial DNA have been demonstrated in antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Here we investigated the significance of serum nicotinamide adenine dinucleotide-ubiquinone oxidoreductase chain 6 (ND6), which is encoded by mtDNA and can attract neutrophils, in AAV. METHODS Thirty-seven AAV patients (32 patients with positive myeloperoxidase-ANCA and 5 patients with proteinase 3-ANCA) were enrolled. Relationship between serum ND6 and clinico-laboratory characteristics were analyzed. RESULTS The ND6 level of patients was higher than normal people (46.56 ± 23.67 pg/mL vs. 4.95 ± 2.45 pg/mL, P < 0.001) The ND6 levels of patients who needed hemodialysis at disease onset and who had pulmonary hemorrhage (PH) were higher than that of the corresponding controls (P = 0.004 and 0.044 respectively). The ND6 level negatively correlated with the percentages of normal glomeruli in kidney biopsy. The AUC of ROC curve to diagnose hemodialysis and PH was 0.804 and 0.750 respectively. ND6 level positively correlated with Birmingham Vasculitis Activity Score in active disease, and returned to normal after remission. Patients with higher serum ND6 had higher mortality (P = 0.023). CONCLUSIONS Serum ND6 increases in active AAV, and its level correlates with the severity of disease. High ND6 level is associated with severe organ injury and predicts poor prognosis of AAV.