Background & aims: Carboxyethyl-hydroxychromans (CEHC) are hydrosoluble vitamin E metabolites excreted through the renal filter. In this study we investigated the effect of the kidney damage on the blood levels of CEHC.
Methods: Plasma levels of a-CEHC, g-CEHC and their precursors (namely, α-tocopherol and γ-tocopherol) were measured by HPLC with electrochemical detection in chronic (CRF) and end-stage renal failure patients on regular hemodialysis (HD) before and after dialysis. CRF patients (n=26) were divided into three subgroups with different extent of kidney damage as measured by the intervals of creatinine clearance (CrCl, in ml/min): (a) 2–10, (b) 10–20, and (c) 20–45. HD patients (n=8) did not show residual renal function. In all the subjects the intake of vitamin E
(as α-tocopherol) was assessed using a food frequency questionnaire. In the HD group, the plasma concentrations of ascorbic and uric acid (AA and UA, respectively), total thiols, the total antioxidant status (TAS) and reactive carbonyls were also measured.
Results: The progressive deterioration of the kidney function in the different groups of patients produced an exponential increase of both α-CEHC and γ-CEHC in plasma. Compared with healthy controls (α-CEHC¼20.1713.4 and γ-CEHC=230.6±83.0 nmol/l) the levels of CEHC approximately doubled in patients with CrCl<20 ml/min (42.4±20.2 and 424.5.5±174.4; P<0:05 or higher in both) and reached a 3-fold maximum increase in HD patients (77.3±45.7 and 636.6±219.3). The hemodialysis provided a significant, but only a transient, correction of CEHC accumulation (44.8±23.5, 364.2±189.9). The HD patients showed lower intake and levels of vitamin E (α-tocopherol=5.17=±1.0 and γ-tocopherol=0.32±0.11 mmol/mmol cholesterol; P<0:05) compared to healthy controls (5.8±0.8 and 0.43±0.14), but in the CRF patients tocopherol levels were normal or only slightly decreased even though approximately half of the subject had lowered vitamin E intake. When the entire patient population was considered, the blood concentrations of parental tocopherols and CEHC did not correlate. The HD patients before dialysis showed a marked decrease of TAS/UA, AA and thiols levels, while UA and free carbonyls significantly increased. After dialysis, the depletion of AA and thiols further worsened and also UA and TAS/UA decreased, but free carbonyls slightly increased.