Lipid peroxidation and antioxidant status in adults receiving lipid-based home parenteral nutrition

Background: Infusion of lipid emulsions rich in polyunsaturated fatty acids (PUFAs) may increase lipid peroxidation, which is counteracted mainly by superoxide dismutase (SOD) (a zinc-, copper-, and manganese-dependent enzyme), selenium-dependent glutathione peroxidase (Se-GSHPx), and alpha-tocopherol. Objective: We investigated lipid peroxidation and antioxidant status in patients receiving home parenteral nutrition (HPN) providing variable amounts of a lipid emulsion rich in PUFAs, and alpha-tocopherol, zinc, copper, and manganese as recommended by the American Medical Association, and no selenium. Design: Serum malondialdehyde, plasma alpha-tocopherol, selenium, Se-GSHPx, PUFAs, and red blood cell Se-GSHPx and SOD were evaluated in 12 patients and in 25 healthy control subjects. Malondialdehyde was also assessed in a group of 40 healthy control subjects. Results: Patients had significantly higher concentrations of malondialdehyde and SOD and lower alpha-tocopherol concentrations and selenium nutritional status. Linear regression analysis showed that malondialdehyde was associated with the daily PUFA load (r = 0.69, P< 0.03) and with plasma alpha-tocopherol (r = -0.59, P< 0.05), but stepwise multiple regression analysis confirmed only the association between malondialdehyde and alpha-tocopherol; plasma alpha-tocopherol was associated with the daily PUFA load (r = -0.65, P < 0.04) and with the duration of HPN (r = -0.74, P < 0.92). Conclusions: In HPN patients, the peroxidative stress due to lipid emulsions rich in PUFAs is counteracted primarily by alpha-tocopherol. The dosages of alpha-tocopherol, zinc, copper, and manganese recommended by the American Medical Association appear sufficient to sustain SOD activity but inadequate to maintain alpha-tocopherol nutritional status. HPN formulations should be supplemented with selenium.