IDENTIFICATION AND CHOLESTEROL QUANTIFICATION OF LOW-DENSITY-LIPOPROTEIN SUBCLASSES IN YOUNG-ADULTS BY VAP-II METHODOLOGY

Low density lipoprotein (LDL) particles are heterogeneous in size, den sity, and chemical composition; small, dense LDL may be more atherogen ic than large, buoyant LDL. We have developed a rapid microscale metho d called LDL VAP-II (Vertical Auto Profile-II) for quantification of c holesterol in LDL subclasses. The method is based upon a short (1 h) s ingle vertical spin density-gradient ultracentrifugation and on-line V AP-II analyzer. LDL VAP-II is rapid and reproducible. Using this metho d five LDL subclasses, designated as LDL-1 (most buoyant) through LDL- B (most dense), have been identified in a population consisting of 195 medical students (ages, 22-29 years). The R(f)(relative position of t he major LDL peak in the density gradient; the higher the R(f) value, the lower the peak density) was significantly positively correlated wi th cholesterol levels of high density lipoprotein (HDL) (r = 0.594), H DL(3) (0.350) and HDL(2) (0.625), and significantly negatively correla ted with triglycerides (TG) (-0.355) and cholesterol levels of very lo w density lipoprotein (VLDL) (-0.386) and intermediate density lipopro tein (IDL) (-0.432). These results are consistent with those obtained by other investigators. The R(f) value was significantly correlated wi th peak particle diameter as determined by non-denaturing gradient gel electrophoresis (r = 0.859). In a forward stepwise multivariate analy sis comparing R(f) with sex, VLDL, LDL, Lp[a], IDL, HDL(3), HDL(2), an d triglyceride, only HDL(2) remained in the model.