Urinary isoprostane excretion is not confounded by the lipid content of the diet

This study aims to determine if isoprostanes accurately reflect in vivo lip id peroxidation or whether they are influenced by the lipid content of the diet. Isoprostanes were measured in urine of healthy subjects under differe nt conditions of lipid intake and under conditions of oxidative stress (fas ting). We found that isoprostanes were not influenced by the lipid content of the diet: the urinary level remained constant over 24 h as well as over 4 consecutive days when switching from high to low lipid intake. Urinary is oprostane excretion was increased by 40% following a 24 h fast. We conclude d that urinary isoprostane excretion reflects endogenous lipid peroxidation in vivo. (C) 1999 Federation of European Biochemical Societies.