Effect of long-term consumption of oxidized polyunsaturated fatty acids on atherosclerotic lesion in LDL receptor knockout mice

Abstract

The consumption of lipids containing higher amount of saturated or trans-fatty acids has been associated to the higher risk for cardiovascular diseases, while mono or polyunsaturated fatty acids have showed cardiovascular protection. Among the polyunsaturated fatty acids (PUFA), n-6 FA are associated to a more pro-inflammatory condition, caused by eicosanoids produced from the enzymatic oxidation of arachidonic fatty acid. On the other side, n-3 FA have shown several benefic effects, such as reduction of the triacylglycerol and VLDL (very low density lipoprotein) concentration, anti-thrombotic, anti-inflammatory and other effects. For this reason, the replacement of saturated, trans or n-6 FA by n-3 FA represents an alternative to develop functional oils and foods. However, PUFA are very susceptible to oxidative degradation. This chemical reaction can produce secondary compounds potentially toxic, that when chronically consumed could even be pro-atherogenic. Thus, although food companies are already adding n-3 FA and n-6 FA in their products, there is no information if the long term intake of these partially oxidized PUFA would increase or decrease the atherosclerotic process. On the other side, some studies have reported that some n-3 FA products formed by non-enzymatic oxidation could contribute to reduce inflammation. Due to the pro-inflammatory characteristic of n-6 FA, our hypothesis is that long-term consumption of oxidized n-6 FA but not n-3 FA increases atherosclerotic lesion in an animal model. In order to evaluate this hypothesis, three assays will be carried out. Initially, different oils containing n-3 and n-6 PUFA will be submitted to the "temperature/time" conditions that simulate the oils transport, storage and consume. Secondary products of oils oxidation will be identified during this period. For the in vivo assay, 65 LDLr (-/-) mice will be allocated into 5 groups. CONT- and CONT+ groups will be kept under standard and atherogenic diet, respectively, without any supplementation for 24 weeks. Three groups will be fed with an atherogenic diet in which corn oil will be replaced by an oil containing n-6 FA in three different conditions: fresh (N6), weakly oxidized (N6C) and strongly oxidized (N6FR). In a third protocol, other 50 LDLr (-/-) mice will be allocated into 5 groups, where fresh and oxidized oils containing higher amount of n-3 and n-6 FA will be given to the animals by gavage for 16 weeks. After the period of treatment, all groups will be euthanized. Blood and tissues samples will be collected and kept at -80 oC for further analysis. Several clinical and biochemical biomarkers will be evaluated, such as Fn-isoprostanes, MDA, 4-HNE, 4-HHE, lipid profile, activity and expression of proteins associated to the redox condition, inflammatory cytokines and others. (AU)