Diet and lipoprotein oxidation: analysis of oxidized triacylglycerols in pig lipoproteins.

Oxidized lipoproteins have a recognized role in atherogenesis, but molecular-level research on oxidized lipids in lipoproteins and the effect of diet on these molecules have been limited. In the present study, the effects of three sunflower seed oil diets differing in oxidation levels (PV in oils 1, 84, and 223 mequiv O2/kg) on lipoprotein lipid oxidation in growing pigs were investigated. The emphasis was on the investigation of oxidized TAG molecules found in chylomicrons and VLDL. A method based on RP-HPLC and electrospray ionization-MS was used for the analysis of oxidized TAG molecules. The baseline diene conjugation method was used for the estimation of in vivo levels of lipoprotein lipid oxidation. Several oxidized TAG structures were found in the samples. These products consisted of TAG molecules with a hydroxy, an epoxy, or a keto group attached to a FA, and of TAG molecules containing an aldehyde structure derived from a FA. The lipoprotein lipids and TAG were more oxidized in the pigs fed on the most oxidized oil compared with those fed on nonoxidized oil. Oxidation of dietary fat was reflected in the lipoprotein oxidation. New, detailed information on oxidized TAG molecules of chylomicrons and VLDL was obtained.

Triacylglycerol molecular weight and to a lesser extent, fatty acid positional distribution, affect chylomicron triacylglycerol composition in women.

Postprandial composition of chylomicron triacylglycerols (TAG) and their clearance may be affected by the molecular weight of TAG, their fatty acid (FA) combinations and the positional distribution of FA in TAG. Delayed postprandial TAG clearance is a risk factor for cardiovascular disease. However, due to the complexity of traditional analysis methods, the composition of individual TAG molecules is frequently overlooked. In this study, chylomicron TAG molecular weight distribution and regioisomerism were followed in 10 healthy female volunteers after two fat loads with identical FA composition but different positional distributions (palm oil and transesterified palm oil). An efficient tandem mass spectrometric method of analysis was applied. During the 6-h observation period, the relative concentrations of TAG with 48:2 [48 acyl carbons and 2 double bonds (ACN:DB)], 50:3 and 50:2 decreased, whereas the proportions of 48:0 (tripalmitin), 52:3 and 54:4 remained constant and the proportion of 54:3 (triolein) increased (P < 0.05). The existence of seven regioisomers containing palmitic, oleic and linoleic acids in different sn-positions was studied. The amount of 1,3-dipalmitoyl-2-oleoyl-sn-glycerol was less (P < 0.05) 1.5 h postprandially than at 2-5 h after palm oil, and less (P < 0.05) at 1.5 h than at 2-6 h after transesterified palm oil. This may be an indication of a loss of palmitic acid in the gut. Taken together, TAG molecular weight composition and to a lesser extent, positional distribution, seem to affect the rates of chylomicron TAG clearance in humans.