title: Two subpopulations of intermediate density lipoprotein and their relationship to plasma triglyceride and cholesterol levels.
abstract: We observed the appearance of two intermediate density lipoprotein (IDL) subfractions on gradient gel electrophoresis of lipoproteins in the density range 1.006-1.030 g/ml and estimated their approximate concentrations in plasma in subjects with a wide range of lipid levels, from 0.55 to 28.0 mmol/l plasma triglyceride and 3.75-10.0 mmol/l cholesterol. The larger species, IDL-I (31.7 +/- 0.7 nm, mean +/- SD), showed little variation in size in normal and moderate hyperlipidaemic individuals. The estimated concentration of IDL-I was positively related to plasma triglyceride (r = 0.63, P = 0.0004) and low density lipoprotein (LDL) cholesterol (r = 0.68, P = 0.0003). These findings are consistent with the view that IDL-I is a metabolic intermediate between very low density lipoprotein (VLDL) and LDL. The smaller subfraction, IDL-II (25.7 +/- 2.4 nm) was virtually the only true species observed in subjects with plasma triglyceride < 1.0 mmol/l and its estimated concentration fell as plasma triglyceride increased (r = -0.58, P = 0.0002). IDL-II particle size changed in concert with LDL particle size (r = 0.61, P < 0.0001), suggesting that they were influenced by common metabolic factors. These observations provide further support for the hypothesis outlined by Musliner et al. [1] that IDL-I was part of the delipidation chain from VLDL to LDL, whereas IDL-II arose from a separate source, possibly directly released from the liver. Hence the two subpopulations of IDL differ in their relationship to plasma triglyceride and cholesterol levels.
authors.affiliation: Department of Biomedical Science, University of Wollongong, NSW, Australia. barbara_meyer@uow.edu.au
authors.forename: B J
authors.initials: BJ
authors.lastname: Meyer
authors.forename: M J
authors.initials: MJ
authors.lastname: Caslake
authors.forename: M M
authors.initials: MM
authors.lastname: McConnell
authors.forename: C J
authors.initials: CJ
authors.lastname: Packard
mesh_terms: D000328:Adult; D000368:Aged; D001161:Arteriosclerosis / Q000097:blood*; D002784:Cholesterol / Q000097:blood*; D005260:Female; D006801:Humans; D008074:Lipoproteins / Q000097:blood*; D053419:Lipoproteins, IDL; D008297:Male; D008875:Middle Aged; D014280:Triglycerides / Q000097:blood*
chemical_list: D008074:Lipoproteins; D053419:Lipoproteins, IDL; D014280:Triglycerides; D002784:Cholesterol