Determination of Oxidized Lipids in Commonly Consumed Foods and a Preliminary Analysis of Their Binding Affinity to PPARγ

Foods rich in poly unsaturated fatty acids (PUFA) are vulnerable to oxidation. While it is well established that endogenously derived oxidized lipids are ligands of the transcription factor PPAR gamma, the binding ability of diet-derived oxidized lipids is unknown. Our two-fold objective was to determine the oxidized lipid content and PPAR gamma binding ability of commonly consumed foods. Extracted food lipids were assayed for the peroxide value, conjugated dienes, and aldehydes, and PPAR gamma binding was assessed by an in vitro PPAR gamma ligand screening assay. Oxidized lipids were present in all foods tested at the time of purchase, and oxidation did not increase during storage. The peroxide values for walnuts, sunflower seeds, and flax meal were significantly lower at the end of three months as compared to the day of purchase (peroxide value: 1.26 +/- 0.13 vs. 2.32 +/- 0.4; 1.65 +/- 0.23 vs. 2.08 +/- 0.09; 3.07 +/- 0.22 vs. 9.94 +/- 0.75 mEq/kg fat, p <= 0.05, respectively). Lipids extracted from French fries had the highest binding affinity (50.87 +/- 11.76%) to PPAR gamma compared to other foods. Our work demonstrates that oxidized lipids are present in commonly consumed foods when purchased, and for the first time demonstrates that some contain ligands of PPAR gamma.

Automated summary

This study found that oxidized lipids are present in commonly consumed foods and some of them contain ligands of PPAR gamma. The oxidative levels of some foods decreased after three months, with French fries showing the highest PPAR gamma binding affinity among the tested foods.