Erythrocyte glutathione transferase: a potential new biomarker in chronic kidney diseases which correlates with plasma homocysteine.

Glutathione transferases (GSTs) are a superfamily of enzymes involved in cell detoxification. Previous studies reported an increased expression of erythrocyte glutathione transferase (e-GST) in end-stage renal disease patients on maintenance hemodialysis (MHD), but physiological e-GST levels in chronic kidney diseases patients under conservative therapy (CKD). We re-evaluated the e-GST levels in 72 CKD patients and studied the correlation between this enzyme and the plasma homocysteine (Hcy) in 62 MHD patients. This amino acid is an important cardiovascular risk factor and it is present at high concentrations in more than 90% uremic patients. A new automated procedure for GST activity, validated by intra-assay and inter-assay measurements and by recovery experiments, confirmed an increased e-GST activity in HD patients (10.24 ± 2.74 U/gr Hb) compared to healthy subjects (5.8 ± 1.8 U/gr Hb). Interestingly, a significant increase of e-GST activity was also observed in pre-dialysis patients related to the NK-DOQI stages (7.4 ± 2.43 U/gr Hb, 8.13 ± 4.55 U/gr Hb, 9.46 ± 2.49 U/gr Hb, 12.35 ± 2.74 U/gr Hb in stages from I to IV, respectively). No correlation has been found between e-GST activity and hemoglobin, transferrin, sideremia and markers of systemic inflammation. For the first time a significant correlation was observed between increased plasma Hcy levels and e-GST activity (P < 0.0001) in MHD patients. Thus, e-GST proposes as new biomarker in CKD and MHD patients.