Triglycerides and atherogenic lipoproteins: rationale for lipid management

Epidemiologic and clinical studies have demonstrated a relation between plasma triglyceride levels and risk of coronary artery disease and an amplification of risk with combined elevations of triglyceride and low-density lipoprotein (LDL) cholesterol. In patients with coronary disease, angiographic progression and clinical events have been correlated with concentrations of smaller very-low-density lipoproteins (VLDL) and intermediate-density lipoproteins (IDL), consistent with evidence for enhanced atherogenicity of lipolytic products of triglyceride-rich lipoprotein metabolism, including postprandial lipoproteins. IDL levels also have been shown to be strongly and independently predictive of progression of carotid artery intimal-medial thickness, a measure of early atherogenesis that is related to coronary disease risk. Although there is evidence that these triglyceride-rich lipoprotein species may have direct atherogenic effects, other lipoprotein changes associated with altered triglyceride metabolism may be of particular importance in the development of coronary artery disease. These include reductions in high-density lipoprotein (HDL) and increases in small, dense LDL particles (LDL subclass pattern B). Because of the strong interrelations among elevated triglyceride, reduced HDL, and small dense LDL, it is difficult to use statistical techniques to determine the independent contributions of these traits to coronary disease risk. Based on their biologic properties, it is likely that each are involved in multiple steps of the disease process. Moreover, this cluster of lipoprotein changes is associated with other conditions that can promote vascular disease, including increases in coagulation factors and reduced insulin sensitivity. Analyses from intervention trials in patients with coronary disease have indicated that measurement of plasma triglyceride and LDL particle distributions can be of value in predicting the benefits of specific lipid-altering therapies on disease progression.