The effect of a moderately thermoxidized dietary fat on the vitamin E status, the fatty acid composition of tissue lipids, and the susceptibility of low-density lipoproteins to lipid peroxidation in rats
K. Eder et M. Kirchgessner, The effect of a moderately thermoxidized dietary fat on the vitamin E status, the fatty acid composition of tissue lipids, and the susceptibility of low-density lipoproteins to lipid peroxidation in rats, FETT-LIPID, 101(5), 1999, pp. 178-184
Several studies demonstrated that dietary oxidized oils markedly affect the
vitamin E status and alter the fatty acid composition of tissue lipids in
animals. It must however be emphasized that highly oxidized oils reduce the
feed intake of animals, which makes it difficult to interpret the results.
Therefore, the present study used a moderately thermoxidized soybean oil (
peroxide value: 75 mEq O-2/kg), having a similar fatty acid composition as
fresh soybean oil (peroxide value: 9.5 mEq O-2/kg) which was used as contro
l. Moreover, according to a bifactorial design, two different vitamin E sup
plementary levels (11 vs. 511 mg alpha-tocopherol equivalents per kg diet)
were used. The experiment was conducted with male Sprague-Dawley rats. The
feeding period lasted for 40 days. In order to assess the vitamin E status,
the vitamin E concentrations in plasma, liver, heart, kidney, and adipose
tissue were determined. The Vitamin E supply had a pronounced effect on the
vitamin E concentrations of those tissues whereas the type of fat had only
a slight effect, The fatty acid composition of total lipids from liver, er
ythrocytes, and low-density lipoproteins was also only slightly influenced
by the oxidized fat. The osmotic fragility of erythrocytes was even reduced
by feeding the oxidized oil. with a low vitamin E supply; the ia vitro sus
ceptibility of low-density lipoproteins to lipid peroxidation was slightly
increased by feeding the oxidized oil. In contrast, with a high vitamin E s
upply, there was no adverse effect of the dietary oxidized oil on the susce
ptibility of low-density lipoproteins to lipid peroxidation. Feeding the ox
idized oil, however, increased the concentrations of malondialdehyde in low
-density lipoproteins suggesting an increased in vivo Lipid peroxidation. T
herefore, it cannot be ruled out that moderately oxidized dietary fats incr
ease the atherogenicity of low-density lipoproteins. In contrast, a moderat
ely oxidized oil scarcely affected the vitamin E status and the fatty acid
composition of tissue lipids.