Selenium kinetics and changes in glutathione peroxidase activities in patients receiving long-term parenteral nutrition and effects of supplementation with selenite

Abstract

Selenium (Se) is an essential trace element in humans. Patients receiving long-term parenteral nutrition (PN) are at risk for Se deficiency. We investigated changes in Se levels and glutathione peroxidase (GSH-Px) activity in serum and tissue (red blood cells, RBC) in addition to urinary excretion of Se in patients receiving long-term PN with and without Se supplementation. In patients without Se supplementation, both Se levels and GSH-Px activity in serum decreased with duration of PN. The serum Se levels were below the lower limits of the control values in 19 of 33 patients (58%) who received PN for less than 1 mo. Conversely, RBC GSH-Px activity remained at a sufficient level in 9 of 12 patients (75%) who received PN for 3–6 mo. The RBC Se levels in all of these patients were lower than the control levels. Urinary Se concentrations were significantly correlated with serum Se concentrations by linear regression analysis ( r = 0.707, P < 0.05). In patients with Se supplementation, urinary Se concentrations increased exponentially with increases in serum Se levels. These findings indicate that a time lag precedes the decrease in levels of serum Se, RBC Se, serum GSH-Px, and RBC GSH-Px in patients without Se supplementation and the increase in excretion of urinary Se in patients with Se supplementation. The monitoring of not only serum Se levels but also RBC GSH-Px activity and urinary Se levels is required for optimal Se supplementation during long-term PN.