Long-term effects of unsaturated fatty acid dominance on the release of free radicals in the rat

Abstract

The aim of this study was to investigate the effects of an abundance of unsaturated fatty acids, hyperoxia, and vitamin E on free radical formation in vitamin E-deficient rats. The excess of unsaturated fatty acids was achieved by i.v. administration of a lipid emulsion (Intralipid). To assess free radical formation, we measured the autooxidative susceptibility of red blood cells (AOS) and the thiobarbituric acid reacting substrates (TBARS) in LDL and HDL. Intralipid significantly increased all the measured parameters compared with controls (AOS: 1385 +/- 73 versus 1056 +/- 55; LDL-TBARS: 4955 +/- 422 versus 1050 +/- 33; HDL-TBARS: 6855 +/- 573 versus 1033 +/- 26 nmol TBARS/mmol). Hyperoxia alone increased AOS more than Intralipid alone, whereas LDL- and HDL-TBARS concentrations were affected less by hyperoxia than lipid emulsion. The combination of hyperoxia and Intralipid was most effective in raising all measured parameters (AOS: 2285 +/- 141; LDL-TBARS: 6716 +/- 318; HDL-TBARS: 14614 +/- 1000 nmol TBARS/mmol). Vitamin E completely prevented the increase in AOS, LDL-TBARS, and HDL-TBARS without fully reversing the increase in free radical formation caused either by Intralipid or by the combination of hyperoxia and Intralipid. These findings suggest that vitamin E supplementation is beneficial to counter increased free radical formation, such as that in response to hyperoxic attacks or lipid-containing parenteral nutrition, which is frequently encountered in the treatment of premature infants.