True deficiency of antioxidant vitamins E and A in dialysis patients. Relationship with clinical patterns of atherosclerosis.

ABSTRACT

Atherosclerosis is an important cause of morbidity and mortality in peritoneal dialysis (PD) patients. Oxidative stress plays a role in the pathogenesis of uremic atherosclerosis. Although antioxidant substances (vitamins A and E) are elevated in the plasma of dialysis patients, intracellular and clinical signs of hypovitaminosis are frequently found. Recently, the importance of vitamin/carrier complexes as a marker of vitamin bioavailability has been demonstrated. In the present study, we analyzed vitamin A and E bioavailability, measured as vitamin/carrier complexes, and the relationship of those measurements with clinical atherosclerosis status in PD patients. We studied 45 patients (15 men, 30 women), who were divided into four groups according to clinical atherosclerotic score (CAS). Five cases were scored as CAS grade 1 (low CAS); 9 as CAS-2; 18 as CAS-3; and 13 as CAS-4. Vitamins A and E and their carriers [prealbumin and retinol binding protein (vitamin A), and cholesterol and triglycerides (vitamin E)] were determined. Plasma levels of vitamin A were low in 5 patients, normal in 7 patients, and high in 33 patients. By correcting the values for the carrier levels, we created three groups 24 patients showed low vitamin A/carrier complex (5 from the low plasma vitamin A group, 6 from the normal-value group, and 13 from the high-value group); 11 patients were in the group with normal vitamin A/carrier (1 from the normal plasma vitamin A group, and 10 from the high-value group); and 10 patients were in the group with high vitamin A/carrier. The vitamin A/carrier complex showed a statistically significant, negative linear correlation with CAS and with serum iron. Low vitamin E plasma levels were found in 1 patient, normal levels in 28 patients, and high levels in 16 patients. When those values were corrected using the carrier values, three groups were also created. The group with low vitamin E/carrier complex contained 24 patients (1 from the low-value group, 22 from the normal-value group, and 1 from the high-value group). The group with normal vitamin E/carrier complex contained 21 patients (15 from the group with high vitamin E values, and 6 from the normal-value group). By univariate logistic regression analysis, significant associations between CAS and vitamin E plasma levels, vitamin E/carrier, age, and serum albumin were found. In the multiple logistic regression analysis, we confirmed that vitamin E/carrier complex, age, and serum albumin showed independent associations with CAS, but not with vitamin-only plasma levels. Our results in PD patients show a vitamin/carrier complex disorder that results in elevated vitamin mobilization from pool and target cells. Our results and the findings of other researchers about intracellular vitamin A and E deficiencies may change the traditional concept of hypervitaminosis A and E in uremic patients.