Influence of nutritional status on plasma and erythrocyte sulphur amino acids, sulph-hydryls, and inorganic sulphate in end-stage renal disease.

BACKGROUND: The metabolism of sulphur amino acids and sulph-hydryls is altered in end-stage renal disease (ESRD). Previous studies have focused on the role of vitamin status in the development of hyperhomocysteinaemia in such patients, but little information exists about the influence of global nutritional status and hypoalbuminaemia on sulphur-containing compounds in ESRD. As considerable fractions of sulph-hydryls in blood are present in erythrocytes (RBC), which among others participate in intra-organ amino acid transport, the relationship between plasma and RBC levels of several of these compounds and various nutritional parameters were evaluated in the present study. METHODS: Thirty-seven ESRD patients (24 males, 13 females) on dialysis treatment (18 haemodialysis, 19 continuous ambulatory peritoneal dialysis) and 21 healthy subjects (seven males, 14 females) were examined. The subjective global nutritional assessment (SGNA) showed that 10 (27%) patients were malnourished and 27 (73%) had normal nutritional status. RESULTS: All the ESRD patients had high plasma total homocysteine (tHcy) levels. The plasma concentrations of methionine (Met) and taurine (Tau) were low, but the levels of the other sulphur-containing compounds were high. In the RBC, the patients had higher levels of tHcy and Tau than in healthy subjects, but no difference was seen in the concentrations of glutathione (GSH), cysteinylglycine (Cys-Gly), Met, and Cys. The plasma inorganic sulphate concentrations were five times higher in the patients than in healthy subjects, but the levels did not differ significantly between the malnourished patients and those with normal nutritional status. The malnourished patients had lower plasma, but not RBC, levels of tHcy, GSH, and Cys-Gly than those with normal SGNA. Plasma tHcy correlated positively with serum (s)-albumin and anthropometric parameters and negatively with SGNA. RBC and whole blood, but not plasma, GSH concentrations were correlated with haematocrit and were significantly lower in low haematocrit patients (< or = 37%, n = 19) than in those with a high haematocrit (> 37%, n = 18). CONCLUSIONS: These results show that nutritional status and s-albumin influence plasma, but not RBC, concentrations of sulph-hydryls in ESRD patients. This should be considered when the relationships between cardiovascular disease and plasma tHcy or other sulphur-containing compounds are assessed. The study also shows that GSH concentrations in RBC and whole blood are related to haematocrit and not to nutritional parameters, indicating that anaemia status rather than nutritional status determines RBC and whole blood GSH levels in ESRD patients.