Hyperhomocysteinemia in patients undergoing dialysis: As a risk factor for atherosclerosis

To clarify the sulfur amino acid metabolism in patients undergoing dialysis, we measured plasma levels of methionine, cystine and homocysteine, as well as serum levels of vitamin B6, vitamin B12 and folate, after an overnight fast in 36 CAPD patients (age 48.0±12.3 years), 14 HD patients (54.9±16.4) and 20 normal subjects (40.7±14.5). Plasma levels of total homocysteine were measured by fluoro-HPLC after treatment of plasma with dithioerythritol. Plasma levels of total homocysteine (μmol/l) in both CAPD and HD patients were significantly higher than those of normal subjects (38.2±37.2, 27.3±10.2, 19.0±14.9, respectively). In the normal subjects, plasma levels of total homocysteine were inversely related to serum folate levels. However, this relationship was not noted in CAPD nor HD patients. These findings suggest that plasma levels of total homocysteine are regulated by the degree of conversion from homocysteine to methionine in normal subjects, while other regulatory factors determine plasma levels of total homocysteine in patients undergoing dialysis. There was also a significant correlation between atherosclerotic score and plasma levels of total homocysteine in CAPD patients. These results suggest that hyerhomocysteinemia may play a role in atherosclerosis in patients undergoing dialysis.