The Relationship between Haptoglobin Polymorphism and Oxidative Stress in Hemodialysis Patients

Abstract

Summary Background: The relationship between haptoglobin polymorphism and oxidative stress in hemodialysis patients is not fully understood. In this study, total antioxidant capacity and ce ru - loplasmin ferroxidase activity were evaluated in relation to haptoglobin phenotype distribution in hemodialysis patients. Methods: Serum samples collected from 161 patients and 84 healthy controls were haptoglobin-typed by electrophoresis. Ceruloplasmin ferroxidase activity and total antioxidant capacity were assayed using colorimetric methods. Results: Irrespective of the haptoglobin phenotype, patients exhibited significantly lower total antioxidant capacity (1.42± 0.29 vs. 1.55±0.28 mmol/L, P=0.002) and higher ferroxidase activity than controls. Frequency of Hp1-1 and Hp2-1 in patients was 15.5% and 36% as compared with 9.5% and 41.7% in controls. While ferroxidase activity was lower in Hp2-2 patients than in controls (142±61 vs. 179±47 U/L, P=0.002), it was higher in Hp2-1 (173±56 U/L) and Hp1-1 (170±54 U/L) patients than in controls (141±43 and 99±30 U/L respectively) (P=0.002 and 0.009). Ferroxidase activity in Hp2-2 patients was significantly lower than that of Hp2-1 or Hp1-1 patients (P=0.004 and 0.034). Total antioxidant capacity was significantly lower only in Hp2-2 patients (1.44±0.25) compared to that in Hp2-2 controls (1.65±0.22) (P=0.000). Conclusions:These findings suggest that haptoglobin polymorphism can differentially impact oxidative stress levels in hemodialysis patients.