Lipid peroxidation in vivo Evaluation and application of methods for measurement

Abstract: Lipid peroxidation is thought to be an important factor in the pathophysiology of a number of diseases and in the process of ageing, but its measurement in vivo has been difficult. The aim of this thesis was to evaluate methods for measurement of lipid peroxidation in vivo that are suitable for clinical investigations, and to apply these methods in animal and human studies investigating basal conditions and situations associated with increased lipid peroxidation.The ferrous oxidation in xylenol orange assay for quantification of total plasma lipid hydroperoxides was re-evaluated regarding sample handling and storage. It was shown to be a useful tool for analyses of fresh but not stored plasma samples.A methodology for measurement of the total amount (sum of free and esterified) of an F2-isoprostane, 8-iso-prostaglandin F2?, in tissues using alkaline hydrolysis in combination with an existing radioimmunoassay was developed. High levels of 8-iso-prostaglandin F2? in rat liver tissue were quantified by this technique both at basal conditions and in an experimental model of increased lipid peroxidation induced by carbon tetrachloride.Supplementation with vitamin E to rats decreased both non-enzymatic and enzymatic lipid peroxidation as measured by 8-iso-prostaglandin F2? and a major prostaglandin F2? metabolite. This was verified both in the urine at basal conditions, and in the urine and liver tissue after carbon tetrachloride induced lipid peroxidation.In a randomised cross-over study in humans, a rapeseed oil-based diet with an increased proportion of easily oxidised polyunsaturated fatty acids was compared to a control diet rich in saturated fats. The rapeseed oil-based diet did not seem to increase the degree of lipid peroxidation in plasma and urine as measured by 8-iso-prostaglandin F2?, hydroperoxides and malondialdehyde, presumably due to a sufficient content of antioxidants in the rapeseed oil diet.In conclusion, the simultaneous measurement of several biomarkers of lipid peroxidation is a promising approach for future studies investigating the possible role of lipid peroxidation in vivo under basal conditions and in the pathology of diseases.