Homocysteine, vitamin B12, serum and erythrocyte folate in peritoneal dialysis patients

Plasma homocysteine (tHcy) is an important risk factor for atherosclerosis in dialysis patients. Few data were reported on the prevalence and severity of hyperhomocysteinemia in peritoneal dialysis (PD) patients. In addition, little attention was paid to the search of factors possibly involved in the pathogenesis of hyperhomocysteinemia in these patients. A cross-sectional study was performed in 107 stable PD patients. None of them was given folate or vitamin B12 supplementation before or during the study. Plasma tHcy, serum vitamin B12, serum and erythrocyte folate were measured by immunoenzymatic methods. Genetic analysis of the methylentetrahydrofolate-reductase thermolabile mutation (tMTHFR) was performed in 61 patients. 97% of patients had tHcy levels higher than normal. tHcy was not different between men and women, patients with or without malnutrition, with or without clinically evident atherosclerotic vasculopathy, with or without anemia. tHcy levels were significantly higher in homozygotes for the tMTHFR mutation than in patients carrying the wild type form. Significant univariate correlation was found between hyperhomocysteinemia and time since the start of dialysis, serum and erythrocyte folate and vitamin B12. The best fitted model equation was log tHcy = 108.53 + 0.1606 (duration of dialysis) -1.1053 (s-F) -0.7980 (age) - 0.0215 (vitamin B12). Our results agree with those reported by other authors in hemodialysis patients. Despite the large number of PD patients with normal serum vitamin B12 and folate status, the relation between tHcy and vitamin B12 or folate suggests that the supplementation of these vitamins could be useful irrespective of their serum levels, especially in younger patients or in those treated for a long period of time with peritoneal dialysis. The important role of homocysteine (tHcy) as an independent risk factor for atherosclerotic vascular disease [Welch and Loscalzo 1998] prompted clinical investigators to measure plasma levels of this aminoacid in different categories of patients, including patients with chronic renal failure or on chronic dialysis [Dennis and Robinson 1996]. However, little informations are available for patients on peritoneal dialysis (PD) [Kim et al. 1994, Moustapha et al. 1999, Van Guldener et al. 1998, Vychytil et al. 1998]. The aim of the study was to evaluate the prevalence of hyperhomocysteinemia and defects in metabolically related vitamins (B12 and folate) in a large population of PD patients. Furthermore, we tried to correlate plasma tHcy levels with clinical and biochemical parameters which could influence tHcy metabolism and therefore, increase the level of this aminoacid.