The present invention relates to a method for measuring the cholesterol uptake capacity of lipoproteins. The present invention also relates to a reagent kit for measuring the cholesterol uptake capacity of lipoproteins. The present invention further relates to a tagged cholesterol which can be used in the method and the reagent kit.

BACKGROUND ART

Cholesterol metabolic disorder is involved in various diseases, and the blood cholesterol concentration is known to be an indicator of the disorder. However, the cholesterol concentration may not reflect the presence of the diseases, the risk of the diseases, and the like. Therefore, there is interest in the qualitative indicator which is focused on the functions of cholesterols as well as the quantitative indicator such as the cholesterol concentration.

For example, even if the high-density lipoprotein cholesterol (HDL-C) concentration in blood is high, the risk of the cardiovascular disease (CVD) may not be decreased. Therefore, the possibilities in which the HDL-C concentration does not reflect the risk of CVD completely are pointed out. There is interest in the functions of high-density lipoprotein (HDL). It is reported that the excretion of cholesterol from peripheral tissues by HDL is a negative prognostic factor against the risk of CVD.

As a method for determining the functions of HDL, for example, PCT International Application Publication No. 2012/104411 describes a method for diagnosing dyslipidemia by using a fluorescently labeled cholesterol without using cultured cells. In the method, a monolayer surrounding the various lipoprotein including low-density lipoprotein (LDL) or HDL is labeled with a fluorescently labeled cholesterol (cholesterol pyrene), and a subject is diagnosed with dyslipidemia based on the resulting fluorescent spectrum by measuring the labeled lipoprotein. The literature describes that the labeled lipoprotein can be separated from free fluorescently labeled cholesterol by ultracentrifugal separation, dialysis, or FPLC by using gel filtration column.

SUMMARY

The present invention provides a method for measuring the cholesterol uptake capacity of lipoproteins, comprising the steps of:

forming a complex by contacting a lipoprotein in a sample, a tagged cholesterol, and an antibody which specifically binds to the lipoprotein, the complex comprising the lipoprotein, the tagged cholesterol incorporated into the lipoprotein, and the antibody;

labeling the complex by bonding a capture body which specifically binds to the tag and a label with the complex;

detecting a signal resulted from the label which has been bound to the complex.

The present invention also provides a reagent kit for measuring the cholesterol uptake capacity of lipoproteins, comprising:

a tagged cholesterol;

an antibody which specifically binds to the lipoprotein;

a capture body which specifically binds to the tag; and

a label.

The present invention also provides a tagged cholesterol represented by the following formula (III):


where R1is an alkylene group having 1 to 6 carbon atoms, which may have a methyl group,

X and Y are identical or different and each represents —R2—NH—, —NH—R2—, —R2—(C═O)—NH—, —(C═O)—NH—R2—, —R2—NH—(C═O)—, —NH—(C═O)—R2—, —R2—(C═O)—, —(C═O)—R2—, —R2—(C═O)—O—, —(C═O)—O—R2—, —R2—O—(C═O)—, —O—(C═O)—R2—, —R2—(C═S)—NH—, —(C═S)—NH—R2—, —R2—NH—(C═S)—, —NH—(C═S)—R2—, —R2—O—, —O—R2—, —R2—S—, or —S—R2—, wherein each R2is independently an atomic bonding; an alkylene group having 1 to 10 carbon atoms, which may have a substituent group; an arylene group or a heteroarylene group having 6 to 12 carbon atoms, each of which may have a substituent group; or a cycloalkylene group or a heterocycloalkylene group having 3 to 8 carbon atoms, each of which may have a substituent group;

L represents —(CH2)d—[R3—(CH2)e]f— or —[(CH2)e—R3]f—(CH2)d—, wherein R3is an oxygen atom, a sulfur atom, —NH—, —NH—(C═O)—, or —(C═O)—NH—;

TAG is a tag;

a and c are identical or different and each represents an integer of 0 to 6;

b is 0 or 1;

d and e are identical or different and each represents an integer of 0 to 12; and

f is an integer of 0 to 24.

