Genetic differences in hepatic lipid peroxidation potential and iron levels in mice

Oxidative damage to macromolecules, including lipids, has been hypothesized as a mechanism of aging. One end product of lipid peroxidation, malondialdehyde (MDA), is often quantified as a measure of oxidative damage to lipids. We used a commercial colorimetric assay for MDA (Bioxytech LPO-586, Oxis International, Portland, OR) to measure lipid peroxidation potential in liver tissue from young (2 month) male mice from recombinant inbred (RI) mouse strains from the C57BL/6J (B6)×DBA/2J (D2) series (BXD). The LPO-586 assay (LPO) reliably detected significant differences (P<0.0001) in lipid peroxidation potential between the B6 and D2 parental strains, and yielded a more than two-fold variation across the BXD RI strains. In both B6 and D2 mice, LPO results were greater in old (23 month) mice, with a larger age-related increase in the D2 strain. As the level of iron can influence lipid peroxidation, we also measured hepatic non-heme iron levels in the same strains. Although iron level exhibited a slightly negative overall correlation (r²=0.119) with LPO results among the entire group of BXD RI strains, a sub-group with lower LPO values were highly correlated (r²=0.704). LPO results were also positively correlated with iron levels from a group of 8 other inbred mouse strains (r²=0.563). The BXD RI LPO data were statistically analyzed to nominate quantitaive trait loci (QTL). A single marker, Zfp4, which maps to 55.2 cM on chromosome 8, achieved a significance level of P<0.0006. At least two potentially relevant candidate genes reside close to this chromosomal position. Hepatic lipid peroxidation potential appears to be a strain related trait in mice that is amenable to QTL analysis.