Relationship between triglyceride concentrations and LDL size evaluated bymalondialdehyde-modified LDL

Background: Hypertriglyceridemia is associated with decreased HDL-cholester ol (HDL-C) and increased small dense LDL. In addition, small dense LDL is k nown to be susceptible to oxidation. Methods: We measured LDL, particle size, using gradient gel electrophoresis , and malondialdehyde-modified LDL (MDA-LDL), using an E L ISA, and investi gated the association between triglyceride (TG) concentrations, LDL size, a nd MDA-LDL. Results: TG concentrations correlated negatively with the predominant LDI, size (r = -0.650) and HDL-C concentration (I = -0.556). The relationship be tween TG concentration and LDL, size, evaluated by measuring MDA-LDL, disti nguished subgroups derived from four subfractions of TG concentrations and four distribution ranges of LDL size. These experiments indicated that ther e is a threshold for oxidation susceptibility at an LDL size of 25.5 nm and a TG concentration of 1500 mg/L. To investigate the relationship between L DL size, MDA-LDL concentration, and other lipids (TGs, HDL-C, apolipoprotei n B, and total cholesterol), we evaluated them in control subjects and pati ents with diabetes mellitus or hypertriglyceridemia. When the size range fo r normal LDL was postulated to be 25.5 less than or equal to phi (LDL diame ter) < 26.5 nm, the MDA-LDL concentration was significantly higher in the s ubgroups of patients with LDL in the size range 24.5 less than or equal to phi < 25.5 nm compared with patients with normal LDL. This result also sugg ests that the threshold is at a LDL size of 25.5 nm. Conclusion: The threshold for oxidation susceptibility coincided with the p oint of I;DL size separation between the LDL. subclass patterns A and B as an atherosclerotic risk. (C) 2001 American Association for Clinical Chemist ry.