Triglyceride as a risk factor for coronary artery disease
The data for an independent association between triglyceride concentrations and risk for coronary artery disease (CAD) are equivocal, unlike the data for low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol, which show strong, consistent, and opposing correlations with CAD risk. There is some evidence for triglyceride as an independent risk factor in certain subgroups, for example, women 50-69 years of age (Framingham Heart Study) and in patients with noninsulin-dependent diabetes. However, the evidence is stronger for triglyceride as a synergistic CAD risk factor. For example, patients with the "lipid triad" of high LDL cholesterol, low HDL cholesterol, and high triglyceride accounted for most of the event reduction with lipid-lowering therapy in the Helsinki Heart Study. An important confounder of the correlation between triglyceride and CAD risk is the heterogeneity of triglyceride-rich lipoproteins: the larger triglyceride-rich particles are thought not to be associated with CAD risk, whereas the smaller (and denser) particles are believed to be atherogenic. At present, measurement of fasting triglyceride levels and triglyceride assessment in conjunction with LDL cholesterol and HDL cholesterol concentrations are the most practical methods of evaluating hypertriglyceridemia in CAD risk, although postprandial lipemia may prove a better indicator of atherogenicity. Management of hypertriglyceridemia should initially focus on nonpharmacologic therapy (i.e., diet, exercise, weight control, and alcohol reduction). In diabetic patients, meticulous glycemic control is also important. However, if this approach proves inadequate, there are several pharmacologic options. Fibrates may be effective in decreasing triglyceride and increasing HDL cholesterol. Nicotinic acid (niacin) has been shown to decrease triglyceride, increase HDL cholesterol, lower LDL cholesterol, and decrease lipoprotein(a); it also decreases fibrinogen. The statins appear to be effective in decreasing triglyceride and LDL cholesterol in hypertriglyceridemia; however, they do not normalize metabolism of apolipoprotein B, and HDL cholesterol may remain low. Therefore, combination with a fibrate or niacin may be appropriate. Attention to hypertriglyceridemia with respect to increased CAD risk represents an important step in assessing global risk for CAD development.