Effects of Modifying Triglycerides and Triglyceride-rich Lipoproteins on Cardiovascular Outcomes

Abstract

Elevated levels of triglycerides (and triglyceride-rich lipoproteins) are increasingly being recognized as treatment targets to lower cardiovascular risk in certain patient subgroups, including individuals receiving HMG-CoA reductase inhibitors (statins). Evidence suggests that these agents reduce the risk of coronary events more markedly in patients with elevated triglycerides and low levels of high-density lipoprotein cholesterol (HDL-C). Further, intensive long-term statin therapy that reduces both low-density lipoprotein cholesterol (LDL-C) to <70 mg/dL and triglycerides to <150 mg/dL results in a decreased risk of cardiovascular events compared with more moderate statin treatment. Long-term therapy with fibric-acid derivatives, which lower triglycerides and raise HDL-C, appears to reduce mortality in patients with elevated triglycerides and/or those experiencing the most marked reductions in triglycerides on therapy. However, randomized clinical trials involving fibrates have not shown consistent benefit. Niacin (nicotinic acid), which is the most effective available medication for raising HDL-C and also lowers triglycerides, has not been as extensively studied as fibrates in long-term randomized controlled trials. Initial reports (eg, Coronary Drug Project) demonstrated a reduction in coronary disease but not total mortality in patients randomized to niacin. However, a 15-year follow-up demonstrated that all-cause mortality was significantly reduced in those initially randomized to niacin. At the pathophysiologic level, elevated triglycerides and triglyceride-rich lipoproteins are recognized as potential factors in driving atherosclerotic progression, particularly in mild-to-moderate lesions. Elevated triglycerides also constitute a plausible therapeutic target in certain patients with coronary heart disease (and/or insulin resistance) but without profound LDL-C elevations. The foregoing and other evidence has led consensus panels to lower the upper limit for "normal" triglycerides to 150 mg/dL. Adequately powered randomized controlled trials that specifically assess the effects of lowering triglycerides and raising HDL-C, and trials that target individuals with high triglycerides and low HDL-C, may provide data for recommending specific treatment targets for triglycerides and HDL-C, as well as effective and well-tolerated therapies to achieve these goals.