Postprandial changes in LDL phenotypes in patients with myocardial infarction

Low-density lipoprotein (LDL) particle size is strongly affected by both fasting and postprandial triglyceride levels. We report here that the LDL phenotype shifts toward the smaller phenotype during oral fat tolerance tests (OFTTs) in some patients with myocardial infarction (MI); a condition closely associated with postprandial increases of triglyceride and remnant-like particles (RLPs).

Oral fat tolerance tests were performed on 63 MI patients with fasting serum triglyceride levels of less than 2.25 mmol L-1 (= 200 mg dL-1). Remnant-like particles and other serum lipids were compared among patients characterized by three LDL phenotypes based on nondenaturing gradient gel electrophoresis: pattern A (large LDLs, peak LDL particle size > or = 260 A), pattern I (intermediate-sized LDLs, LDL size > 255 A, < 260 A), and pattern B (small, dense LDLs, LDL size < or = 255 A).

The LDL size decreased significantly in patients with the highest tertile of areas under the incremental curves (AUICs) of triglycerides above the fasting levels. The LDL phenotype shifted toward the smaller phenotype after a fat load in three of eight patients with pattern A and in seven of 35 patients with pattern I. The AUICs of triglyceride-rich lipoproteins were significantly higher in these patients than in the patients exhibiting little change in LDL size, whereas the fasting metabolic parameters were similar among the patients of the same LDL phenotype in the fasting state.

These results suggest that alimentary lipaemia plays an important role in the remodeling of LDL particles into the more atherogenic small, dense LDLs in patients with MI.