Lipid peroxidation is one type of oxidative damage that has been extensively studied with respect to age. The allylic hydrogens in the polyunsaturated fatty acid components of phospholipids in cellular membranes make membranes extremely sensitive to free radical oxidation. One of the major problems confronting investigators measuring lipid peroxidation is the accuracy of the assays measuring lipid peroxidation by malondialdehyde (MDA) and 4-hydroxy-2-nonenol (HNE) levels. The Roberts laboratory was the first to describe the non-enzymatic production of a group of prostaglandin-like compounds that arise from free radical attack on membrane phospholipids (Roberts and Morrow, 2000). As shown in Figure 1, arachadonic acid moieties, esterified to membrane phospholipids, are converted to compounds isomeric to prostaglandin F2α and are referred to as F2-isoprostanes (F2-isoPs). Esterified F2-isoPs are released from the membrane, by the action of phospholipase, into the blood stream and are ultimately excreted in the urine (Morrow et al., 1999). Thus, plasma levels of free F2-isoPs provide a measure of the total endogenous production of F2-isoPs from all sites in the body (11). The formation of F2-isoPs provides an excellent marker of oxidative stress because they can be measured with precision down to the picomolar level; they are relatively stable compounds; they do not exhibit diurnal variations; they are present in detectable quantities in all normal biological tissues; and lastly, F2-isoPs levels are modulated by the antioxidant status of the organism but are not affected by the lipid composition of the diet (Roberts and Morrow, 2000; Janssen, 2001).
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Roberts II, L.J. and Reckelhoff, J.F. (2001). Measurement of F2-isoprostanes unveils profound oxidative stress in aged rats. Biochem. Biophys. Res. Comm. 287, 254-256.
Ward, W.F., Qi, W., Van Remmen, H., Zackett, W.E., Roberts II, L.J., and Richardson, A. (2005). Effects of age and caloric restriction on lipid peroxidation: measurement of oxidative stress by F2-isoprostane levels. J. Gerontol. A Biol. Sci. Med. Sci. 60, 847-851.