Small dense LDL develops through interactions with TRLs, particularly large very low density lipoprotein (VLDL) in the postprandial phase. The small size of LDL and its concomitant increased density and particle number, is also a recognized atherogenic stimulus. The induction of endothelial dysfunction, as well as a prothrombic state, contributes to cardiovascular dysfunction. The size and lipid composition of TRL particles in chylomicrons may be involved in pro-inflammatory atherogenic processes. Elevated TAG, resulting from a fat-rich meal, triggers a chain of metabolic events that reduces HDL-C, promotes formation of small dense LDL particles, and activates factor VII (FVII). The metabolism of TRLs and their effects on remodeling LDL and HDL during reverse cholesterol transport plays a major role in the later stages of atherothrombotic progression. In non-diabetics with moderate hypertriglyceridemia, about 75% of plasma TAG increase was attributed to the increased number of TRLs, with small particle sizes (Sf 12 to 60). In type 2 diabetes, angiographic severity of CAD was positively related to the numbers of circulating TRL particles in plasma, and this relationship was stronger in women than men, and independent of high density lipoprotein (HDL) and LDL. The progression of coronary atherosclerosis amongst non-diabetics in the Monitored Atherosclerosis Regression Study (MARS) was related to TRL levels, whilst angiographic severity of coronary artery disease (CAD) in another non-diabetic population was reported to be greater with higher plasma TAG levels. This landscape changed in the 1990s, when serum triacylglycerol (TAG) was identified as an independent cardiovascular risk factor, and triacylglycerol-rich lipoproteins (TRL) became implicated in the development of atherosclerosis. Both human and animal studies are discussed with implications for human health.įor almost two decades, studies on lipid lowering diets examined the role of saturated, monounsaturated and polyunsaturated fatty acids in affecting plasma low density lipoprotein-cholesterol (LDL-C) concentrations, since foam cell formation triggered by elevated LDL-C lays the foundation for atherosclerotic plaques. The positioning of unsaturated versus saturated fatty acids in the sn-2 position of TAGs indicate differences in early metabolic processing and postprandial clearance, which may explain modulatory effects on atherogenecity and thrombogenecity. A comparison between native and randomized TAGs is the subject of this review with regards to the role of stereospecificity of fatty acids in metabolic processing and effects on fasting lipids and postprandial lipemia. Fat randomization or interesterification is a process involving the positional redistribution of fatty acids, which leads to the generation of new TAG molecular species. However, the distribution of these fatty acids on the triacylglycerol (TAG) molecule and the molecular TAG species generated by this stereospecificity are characteristic for various native dietary TAGs. Most studies on lipid lowering diets have focused on the total content of saturated, polyunsaturated and monounsaturated fatty acids.
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