Antibodies against Nε-homocysteinylated proteins in patients on different methods of renal replacement therapy.

BACKGROUND

High levels of antibodies against Nε-homocysteinylated (Nε-Hcy) proteins have been observed in patients on long-term hemodialysis (HD). We sought to investigate whether these antibodies are present in patients on peritoneal dialysis (PD) in comparable titers and to characterize the factors that determine levels of those antibodies in both patient groups.

METHODS

The study involved 80 patients on HD and age- and sex-matched 75 subjects on PD. Serum IgG antibodies against Nε-Hcy-albumin and -hemoglobin were determined using in-house enzyme-linked immunosorbent assays. Total homocysteine (tHcy), folate, 8-isoprostaglandin F₂α (8-iso-PGF₂α) and paraoxonase-1 (PON-1) activity were also measured.

RESULTS

Patients on PD and those on HD had similar levels of anti-Nε-Hcy-albumin [absorbancy at 490 nm: 0.571 (0.519-0.609) vs. 0.583 (0.523-0.625), p=0.41, respectively] and anti-Nε-Hcy-hemoglobin antibodies [0.659 (0.597-0.705) vs. 0.664 (0.597-0.722), p=0.60, respectively]. In both groups levels of the antibodies correlated with tHcy (r from 0.54 to 0.77, p<0.0001), 8-iso-PGF₂α (r from 0.57 to 0.77, p<0.0001), and folate (r from -0.59 to -0.74, p<0.0001) levels, but not with the cause of renal disease, dialysis vintage, a history of coronary artery disease or PON-1 activity. In the multivariate logistic regression, after adjustment for potential confounders, plasma tHcy was the independent predictor of antibodies against Nε-Hcy-proteins irrespective of the method of dialysis.

CONCLUSIONS

Levels of antibodies against Nε-Hcy-proteins are similar in patients on long-term PD and HD. The level of tHcy is the only independent predictor of both antibodies irrespective of the dialysis method.