Phagocyte-induced lipid peroxidation of different intravenous fat emulsions and counteractive effect of vitamin E

Unsaturated fatty acids, a major component of fat emulsions used in parente ral nutrition, are prone to peroxidation which is an important feature of o xygen-associated tissue damage. We used the nitroblue tetrazolium (NBT) red uction test to measure the production of superoxide radicals by stimulated polymorphonuclear neutrophils (PMN) in the presence of different fat emulsi ons: Intralipid (containing 100% long-chain triacylglycerols, LCT), Vasolip id (a physical mixture of 50% LCT and 50% medium-chain triacylglycerols, MC T) and StructoLipid (structured triacylglycerols containing 63% LCT and 37% MCT). We measured the amount of malonaldehyde (MDA) and 4-hydroxyalkenal t o determine the lipid peroxidation of the three fat emulsions in the presen ce of stimulated neutrophils. Further, we investigated the role of vitamin E (alpha-tocopherol) in preventing lipid peroxidation in vitro. The results showed that the values of NET reduction of PMN were significantly decrease d in each of the three fat emulsions and that increasing concentrations of fat emulsions were associated with decreased values of NET reductions, in a dose-dependent way (P < 0.001). There were, however, no statistically sign ificant differences between the values of the three different types of fat emulsions (P > 0.05). Lipid peroxidation increased significantly in the pre sence of all three types of fat emulsions, and was more pronounced for Intr alipid than for Vasolipid and Structolipid after 1 and 2 h of incubation wi th resting as well as with stimulated phagocytes. The increased lipid perox idation of the fat emulsions was markedly reduced by vitamin E, and the inh ibition was concentration dependent. In conclusion, lipid peroxidation in v itro is more pronounced when PMNs are incubated with fat emulsions. This in crease in lipid peroxidation can be reduced by adding vitamin E to the fat emulsions. (C) Elsevier Science Inc. 1999.