Introduction
Most people believe that LDL is harmful. The truth, however, is that only some subfractions of LDL are implicated in the pathogenesis of atherosclerosis. This subfraction, which is small and dense, is referred to as pattern B LDL.
Review
Research by Austin et al examined 109 cases and 121 controls and found, “the LDL subclass pattern characterized by a preponderance of small, dense LDL particles was significantly associated with a threefold increased risk of myocardial infarction” (1).
Tribble et al found that the smaller and denser an LDL particle is, the more quickly it becomes oxidized (2).
According to a paper published by Ronald Krauss, “The plasma lipoprotein profile accompanying a preponderance of small, dense LDL particles (specifically LDL-III) is associated with up to a threefold increase in the susceptibility of developing [coronary artery disease]. This has been demonstrated in case-control studies of myocardial infarction and angiographically documented coronary disease” (3).
Scheffer et al concluded that “In agreement with the view that small, dense LDL accelerates atherosclerosis, an inverse relationship was observed between LDL size and circulating in vivo oxidized LDL in Type 2 diabetic patients” (4).
Williams et al concluded that “LDL-IVb was the single best lipoprotein predictor of increased stenosis” (5).
St. Pierre et al concluded “These results indicated that estimated cholesterol levels in the large LDL subfraction were not associated with an increased risk of IHD in men and that the cardiovascular risk attributable to variations in the LDL size phenotype was largely related to markers of a preferential accumulation of small dense LDL particles” (6).
Conclusion
Contrary to popular belief, LDL is not inherently harmful, and the larger, more buoyant particles appear to be relatively benign.
References
1 Austin MA, et al. Low-Density Lipoprotein Subclass Patterns and Risk of Myocardial Infarction. JAMA. 1988 Oct; 260(13): 1917-1921.
2 Tribble DL, Holl LG, Wood PD, Krauss RM. Variations in oxidative susceptibility among six low density lipoprotein subfractions of differing density and particle size. Atherosclerosis. 1992;93:189-99.
3 Krauss RM. Heterogeneity of plasma low-density lipoproteins and atherosclerosis risk. Curr Opin Lipidol. 1994 Oct;5(5):339-49.
4 Scheffer PG, et al. Associations of LDL size with in vitro oxidizability and plasma levels of in vivo oxidized LDL in Type 2 diabetic patients. 2003 Jul; 20(7): 563-567.
5 Williams PT, et al. Smallest ldl particles are most strongly related to coronary disease progression in men. Arterioscler Thromb Vasc Biol. 2003 Feb; 23(2): 314-21.
6 St-Pierre AC, et al. Low-density lipoprotein subfractions and the long-term risk of ischemic heart disease in men: 13-year follow-up data from the Québec Cardiovascular Study. Arterioscler Thromb Vasc Biol. 2005 Mar;25(3):553-9.