Tumor Necrosis Factor-Alpha and 8-Hydroxy-2'-Deoxyguanosine are Associated with Elevated Urinary Angiopoietin-2 Level in Type 2 Diabetic Patients with Albuminuria

Background/Aims: We previously showed that urine and serum Angiopoietin-2 (Ang-2) levels increased significantly with the degree of albuminuria in diabetes patients, but the reasons remain unclear. Consequently we aimed to determine whether there was an association between Ang-2, inflammatory cytokines (TNF-α and IL-18) and reactive oxygen species (8-OHdG and SOD) in type 2 diabetes patients with albuminuria. Methods: This retrospective study evaluated 113 patients with type 2 diabetes and normoalbuminuria, microalbuminuria, or macroalbuminuria and 30 healthy controls. Serum and urine TNF-α, IL-18 and 8-OHdG levels were measured by ELISA. Superoxide dismutase (SOD) activity was determined by spectrophotometry. Results: Serum and urine TNF-α, IL-18 and 8-OHdG levels increased significantly with the degree of albuminuria, and were positively correlated with increased Ang-2. In contrast, SOD activity decreased with the degree of albuminuria and was negatively correlated with Ang-2. Multivariable linear regression analysis revealed that serum Ang-2 level was independently associated with serum levels of TNF-α ( P <0.001), 8-OHdG ( P =0.001), and IL-18 ( P =0.003). Urinary Ang-2 level was independently associated with urinary TNF-α ( P <0.001) and 8-OHdG ( P =0.004) levels. Conclusion: TNF-α and 8-OHdG are associated with elevated urinary Angiopoietin-2 levels in type 2 diabetic patients with albuminuria.