DIETARY-EFFECTS ON GROWTH, LIVER PEROXIDES, AND SERUM AND LIPOPROTEINLIPIDS IN RATS FED A THERMOXIDISED AND POLYMERIZED SUNFLOWER OIL

The effect on food intake, weight gain, liver lipid peroxides, lipemia and lipoprotein composition was determined in rats fed a diet with 15 % sunflower oil used repeatedly for frying and containing similar to 1 9% polar material (group 2). These dietary effects were compared over a 4 week study period with those found in rats fed a control diet that contained 15% unused sunflower oil with similar to 5% polar material (group 1). Both groups had similar food and nutrient intakes (except f or linoleic acid, significantly lower (P < 0.01) in group 2), yet the final weight gain and food efficiency and protein efficiency ratios we re significantly lower in group 2, As a consequence of thermoxidised o il ingestion, liver homogenates from group 2 presented higher (P < 0.0 2) levels of thiobarbituric acid reactive substances (TBARS) Liver TEA RS levels were significantly correlated (P < 0.01) with the amount of thermoxidised substances ingested. No treatment effect was found on VL DL lipid composition. However, the LDL fraction of group 2 animals app ears enriched (P < 0.05) in total and free cholesterol. In group 2 rat s, phospholipids, and total and esterified cholesterol were significan tly increased (P < 0.05) in HDL. As a consequence of the changes in th e lipoprotein composition, the amount of all forms of serum cholestero l, and serum phospholipids was significantly higher (at least P < 0.05 ) while the amount of serum triacylglycerols remained unchanged in rat s fed the used oil, HDL-phospholipids were significantly correlated (P < 0.02) with the amount of thermoxidised compounds ingested. The incr ease in serum cholesterol and phospholipids, and in HDL-cholesterol an d HDL-phospholipid concentration seens in group 2 rats may be a protec tive mechanism against the peroxidative stress produced by the: ingest ion of used sunflower oil. (C) 1998 SCI.