Free radical theory of aging: Effect of dietary lipids on lipofuscin accumulation in the hippocampus of rats

Abstract

The fatty acid composition of central nervous system lipids is largely independent of the dietary fat except for docosahexanoic acid (22:6ω3) and its precursors, mainly linolenic acid (18:3ω3). Ingestion of these lipids increases peroxidizability of neuronal phospholipids by displacing 22:5ω6 with 22:6ω3. Since lipofuscin (age pigment) is formed by oxidative polymerization of lipid and protein it seemed likely that increases in dietary 22: 6ω3 and/or peroxidizability of the dietary lipids might enhance lipofuscin accumulation. To evaluate these possibilities groups of male Charles River CD strain rats were fed a commercial diet, or semi-synthetic diets containing either 5%w (percent by weight) lard, 20%w olive oil, or 20%w safflower oil for periods up to 28 months of age; the amount of 22:6ω3 in lard is small, but considerably more than that of 22:6ω3 plus its precursors in olive oil or safflower oil. At 24 months of age the lipofuscin content of hippocampal neurons of rats fed the lard diet was significantly greater than for the control, olive oil or safflower oil groups; there was no significant difference between the latter two groups. Thus lipofuscin accumulation in hippocampal neurons was associated with increases in neuronal content of 22:6ω3 and not with the gross peroxidizability of the dietary lipid.