Decreased plasma cysteinylglycine and taurine levels in branch retinal vein occlusion.

Purpose: Our aim was to determine the plasma levels of the sulfur-containing amino acids homocysteine, cysteine, cysteinylglycine, glutamylcysteine, glutathione and taurine in patients with branch retinal vein occlusion (BRVO) and in healthy subjects and to ascertain whether there are statistically significant differences between patients and controls.

Methods: Homocysteine, cysteine, cysteinylglycine, glutamylcysteine, glutathione and taurine plasma levels were measured in 40 patients with BRVO and 80 age- and gender-matched control subjects by using laser-induced fluorescence capillary electrophoresis methods. Wilcoxon's or Student's t test was used, when appropriate, to determine differences between the groups. Conditional logistic regression analysis was performed to determine the risk factors for BRVO.

Results: BRVO patients showed significantly lower plasma concentrations of cysteinylglycine (p = 0.02) and taurine (p < 0.0001) than controls. Conversely, there were no significant differences in plasma homocysteine, cysteine, glutamylcysteine and glutathione between patients with BRVO and controls. Conditional logistic regression analysis revealed an odds ratio of 0.95 (95% confidence interval: 0.92-0.98, p = 0.001) for taurine and 0.86 (95% confidence interval: 0.78-0.96, p = 0.006) for cysteinylglycine.

Conclusions: This study failed to demonstrate an association between BRVO and the plasma levels of homocysteine, cysteine, glutamylcysteine and glutathione. Cysteinylglycine and taurine were significantly lower in BRVO patients, thus suggesting that reduced plasma levels of these sulfur-containing amino acids may contribute to the pathogenesis of BRVO.