SYSTEM AND METHOD FOR ASSESSING QUANITITES OR SIZES OF LIPOPROTEIN PARTICLES FROM LIPOPROTEIN PARTICLE COMPOSITIONS
This invention relates to methods for assessing quantities of spherical or substantially spherical lipoprotein particles or portions thereof present in a biological sample based on the measurement of free cholesterol and/or phospholipid content in the lipoprotein particles. The invention also relates to the use of the assessed quantities of the lipoprotein particles or portions thereof to determine whether a subject is at increased risk for cardiovascular diseases and cardiodiabetes.
1 . A method for assessing the quantities of one or more classes or subclasses of spherical or substantially spherical lipoprotein particles present in a biological sample, comprising:
isolating one or more classes or subclasses of lipoprotein particles from the non-lipoprotein components in the biological sample, wherein the lipoprotein particles are spherical or substantially spherical;
separating at least one of free cholesterol and phospholipid from the isolated spherical or substantially spherical lipoprotein particles;
measuring the amount of the at least one of free cholesterol and phospholipid that has been separated from the isolated spherical or substantially spherical lipoprotein particles; and
determining the quantities of the one or more classes or subclasses of spherical or substantially spherical lipoprotein particles based on the measured amount of the at least one of free cholesterol and phospholipid.
2 . The method of claim 1 , wherein the quantities of a plurality of different classes or subclasses of spherical or substantially spherical lipoprotein particles in the biological sample are accurately determined.
3 . The method of claim 1 , further comprising, prior to the separating step:
isolating the lipoprotein particles into two or more classes and/or subclasses, wherein the subsequent separating step is performed on one or more lipoprotein particles in one or more of the isolated classes and/or subclasses.
4 . The method of claim 1 , wherein either or both of the isolating steps are carried out by precipitation, electrophoresis, centrifugation, ultracentrifugation, using a surfactant, using a detergent, or a combination thereof.
5 . The method of claim 3 , wherein the step of isolating the lipoprotein particles into two or more classes and/or subclasses comprises:
isolating HDL particles from non-HDL particles, wherein the at least one of free cholesterol and phospholipid separated from the isolated HDL particles is measured to determine the quantities of the HDL particles.
6 . The method of claim 5 , wherein the HDL particles are isolated from the non-HDL particles by precipitation with a precipitant.
7 . The method of claim 6 , wherein the precipitant is dextran sulfate.
8 . The method of claim 5 , further comprising
fractionating the isolated HDL particles into one or more subclasses, wherein the at least one of free cholesterol and phospholipid separated from each fractionated HDL subclass particle is measured to determine the quantity of the fractionated HDL subclass particle.
9 . The method of claim 8 , wherein the HDL subclasses comprise one or more of HDL-1, HDL-2 and HDL-3.
10 . The method of claim 8 , wherein the fractionating is carried out by precipitation, electrophoresis, centrifugation, ultracentrifugation, using a surfactant, using a detergent, or a combination thereof.
11 . The method of claim 8 , wherein fractionating by precipitation is carried out in sequential steps, precipitating one HDL subclass particle at a time.
12 . The method of claim 1 , wherein isolating lipoprotein particles is carried out by electrophoresis to isolate all or nearly all classes of the lipoprotein particles from the non-lipoprotein components in the biological sample, and to isolate different classes or subclasses of the lipoprotein particles from each other simultaneously.
13 . The method of claim 12 , wherein the resulting electrophoretic gel for each isolated lipoprotein particle is used for measuring amount of the at least one of free cholesterol and phospholipid in the lipoprotein particle, whereby the quantities of all isolated classes or subclasses of the lipoprotein particles can be determined simultaneously or nearly simultaneously.
14 . The method of claim 13 , wherein the lipoprotein particles simultaneously determined comprises two or more different classes or subclasses of spherical or nearly spherical lipoprotein particles.
15 . The method of claim 13 , wherein the lipoprotein particles simultaneously determined comprises two or more of HDL-P, VLDL-P, IDL-P, and LDL-P.
16 . The method of claim 1 , wherein the lipoprotein particles or portions thereof are each selected from the group consisting lipoprotein (a) (LP(a)), high density lipoprotein (HDL), intermediate density lipoprotein (IDL), low density lipoprotein (LDL), very low density lipoprotein (VLDL), chylomicron, and mixtures thereof.
17 . The method of claim 1 , wherein separating free cholesterol from the isolated spherical or substantially spherical lipoprotein particles is carried out by subjecting the lipoprotein particles to a cholesterol oxidase.
18 . The method of claim 1 , wherein a cholesterol esterase is not used in separating free cholesterol from the isolated spherical or substantially spherical lipoprotein particles, whereby esterified cholesterol in the core of the lipoprotein particle is not released as free cholesterol.
19 . The method of claim 1 , wherein the determining step is based on empirically derived algorithms determined experimentally from population studies relating amounts of at least one of free cholesterol and phospholipid to lipoprotein particle numbers.
20 . The method of claim 1 , wherein the radii of the spherical or substantially spherical lipoprotein particles are predetermined; and the determining step is based on the measured amount of at least one of free cholesterol and phospholipid and the predetermined radii.
21 . The method of claim 20 , wherein the radii of the spherical or substantially spherical lipoprotein particles are predetermined based on theoretical estimation.
22 . The method of claim 20 , wherein the radii of the spherical or substantially spherical lipoprotein particles are predetermined based on experimental measurement of the average sizes of the classes and subclasses of the lipoprotein particles in an individual or in a population of individuals.
23 . The method of claim 1 , wherein a measured amount of phospholipid is used in determining the quantities of the one or more classes or subclasses of spherical or substantially spherical lipoprotein particles.
24 . The method of claim 1 , wherein a measured amount of free cholesterol is used in determining the quantities of the one or more classes or subclasses of spherical or substantially spherical lipoprotein particles.
25 . The method of claim 1 , wherein the biological sample is human biological matrix, human lipoprotein fraction, blood component, urine, plasma, serum, synovial fluid, or ascitic fluid.
26 . A method of determining whether a subject is at increased risk for at least one of cardiovascular disease and cardiodiabetes, comprising:
a) assessing the quantities of one or more classes or subclasses of spherical or substantially spherical lipoprotein particles present in a biological sample, comprising:
isolating one or more classes or subclasses of lipoprotein particles from the non-lipoprotein components in the biological sample, wherein the lipoprotein particles are spherical or substantially spherical;
separating at least one of free cholesterol and phospholipid from the isolated spherical or substantially spherical lipoprotein particles;
measuring the amount of the at least one of free cholesterol and phospholipid that has been separated from the isolated spherical or substantially spherical lipoprotein particles; and
determining the quantities of the one or more classes or subclasses of spherical or substantially spherical lipoprotein particles based on the measured amount of the at least one of free cholesterol and phospholipid; and
b) comparing the determined quantities of the one or more classes or subclasses of spherical or substantially spherical lipoprotein particles to a control or reference value to determine if the subject is at an increased risk for cardiovascular disease and/or cardiodiabetes.
27 . The method of claim 26 , further comprising, prior to the separating step:
isolating the lipoprotein particles into two or more classes and/or subclasses, wherein the subsequent separating step is performed on one or more lipoprotein particles in one or more isolated classes and/or subclasses.
28 . A method of determining whether a subject is at increased risk for cardiovascular disease comprising:
a) assessing the average sizes of one or more classes or subclasses of spherical or substantially spherical lipoprotein particles present in a biological sample, comprising:
isolating one or more classes or subclasses of lipoprotein particles from the non-lipoprotein components in the biological sample, wherein the lipoprotein particles are spherical or substantially spherical;
separating at least one of free cholesterol and phospholipid from the isolated spherical or substantially spherical lipoprotein particles;
measuring the amount of the at least one of free cholesterol and phospholipid that has been separated from the isolated spherical or substantially spherical lipoprotein particles; and
determining the average sizes of the one or more classes or subclasses of spherical or substantially spherical lipoprotein particles based on the measured amount of the at least one of free cholesterol and phospholipid; and
b) comparing the average sizes of the one or more classes or subclasses of spherical or substantially spherical lipoprotein particles to a control or reference value to determine if the subject is at an increased risk for cardiovascular disease.
29 . The method of claim 28 , further comprising, prior to the separating step:
isolating the lipoprotein particles into two or more classes and/or subclasses, wherein the subsequent separating step is performed on one or more lipoprotein particles in one or more isolated classes and/or subclasses.
30 . The method of claim 3 , wherein the step of isolating the lipoprotein particles into two or more classes and/or subclasses comprises:
isolating LDL particles from non-LDL particles, wherein the at least one of free cholesterol and phospholipid separated from the isolated LDL particles is measured to determine the quantities of the LDL particles.
31 . The method of claim 30 , further comprising:
fractionating the isolated LDL particles into one or more subclasses, wherein the at least one of free cholesterol and phospholipid separated from each fractionated LDL subclass particle is measured to determine the quantity of the fractionated LDL subclass particle.