The comparison of the hydrophobic properties of thoracic lymph ıntestinal VLDL from rat fed various dietary oils and fats

Throacic lymph contains, in addition to chylomicrons, a significant amount of another more dense, triacylglycerol rich fraction, the intestinal VLDL (or small chylomicrons). Intestinal VLDL differ from chylomicrons in terms of flotation, lipid and apolipoprotein composition as well as metabolism. They are synthesized by enterocytes during fasting state and lipid absorption. Absorbed dietary fatty acids are used to from triacylglycerol via the ?-glycerophosphate pathway which is then packed into preVLDL particles and further processed in Golgi. The resulting particles are then secreted into thoracic lymph.A typical lipoprotein structure e.g. intestinal VLDL, comprises a lipid core containing mainly apolar lipids e.g. triacylglycerols and cholesterol esters, which is surrounded by amphipathic lipids including free cholesterol, phopholipids and apolipoproteins. Polar groups of amphipathic lipids expose to aqueous phase whereas their apolar groups are located towards hydrophobic lipid core. Lipoprotein structure mimics micellar organization in this respect.Hydrophobic properties of a lipoprotein give rise to lipoprotein aggregation. Aggregation of lipoproteins have been reported to be one of the underlying causes of atherosclerosis. To this end, intestinal VLDL were isolated by ultracentrifugation from rats given, sunflower, olive oil, palm oil, butter, margarine and fish oil and their hydrophobic properties were compared by vortex induced aggregation and hydrophobic interaction chromatography. Reponses of intestinal VLDL from different dietary fats to vortex induced aggregation under different conditions known to have a effect on the miscellar structure e.g. pH, salt addition and dilution, were also compared. Although statistically insignificant, intestinal VLDL from satrured fats aggregated more than that from unsatured fats.On the contrary, intestinal VLDL from satured fats interacted with hydrophobic stationary phase (butyl-sepharose) less than the others whereas fish oil intestinal VLDL interacted more strongly compared to the lipoproteins from other dietary fats. Intestinal VLDL from fish oil exhibited more susceptibility to factors affecting miscellar structure.As a result saturation degree of a lipoproteins may not be a unique factor determining the hydrophobic properties. Minor components of lipids may also take part in lipoproteins? hydrophobic properties. Considering the beneficial effect of fish oil for the prevention of atherosclerosis, susceptibility of a lipoprotein to the factors effecting miscellar structure might be an additional factor determining the atherogenecity of a lipoprotein particle but this can be understood more clearly with the future investigations.