Novel apoc-i isoforms and their use as biomarkers and risk factors of atherosclerotic disease

A method of diagnosing or determining risk of developing coronary artery disease in a subject, comprising any one of:

• (i) assessing a serum sample from the subject for presence of a first isoform of apolipoprotein C-I comprising 20 or more consecutive amino acids of SEQ ID NO:6, wherein the first isoform has a molecular weight of between 6.7 kD and 6.8 kD and presence of the first isoform in the sample indicates that the subject has coronary artery disease or is at increased risk of developing coronary artery disease compared to a subject without presence of the isoform;
• (ii) assessing a serum sample from the subject for presence of a second isoform of apolipoprotein C-I comprising 20 or more consecutive amino acids of SEQ ID NO:7, wherein the second isoform has a molecular weight of between 6.5 kD and 6.55 kD and presence of the second isoform in the sample indicates that the subject has coronary artery disease or is at increased risk of developing coronary artery disease compared to a subject without presence of the isoform;
• (iii) determining the molecular weight of apolipoprotein C-I isoforms of apolipoprotein C-I associated with high density lipoprotein2 (HDL2) or high density lipoprotein3 (HDL3) in a biological sample from the subject, and identifying the subject as being at risk for developing coronary artery disease if the apolipoprotein C-I isoforms associated with HDL2 or HDL3 in the sample have a molecular weight that is 50 daltons to 150 daltons greater than native apolipoprotein C-I (SEQ ID NO:6) or native apolipoprotein C-I′ (SEQ ID NO:7), respectively;
• (iv) assessing whether a mass spectrum for HDL apolipoprotein C-I proteins recovered from the HDL2 or HDL3 fractions from a serum sample from the subject comprises a peak in the mass spectrum at between 6.7 kD and 6.8 kD, wherein presence of the peak indicates that the subject has coronary artery disease or is at increased risk of developing coronary artery disease compared to a subject without the peak in the mass spectrum at between 6.7 kD and 6.8 kD;
• (v) assessing whether a mass spectrum for HDL apolipoprotein C-I or C-I′ proteins recovered from the HDL2 or HDL3 fractions from a biological sample obtained from the subject comprises a peak in the mass spectrum at between 6.5 kD and 6.55 kD, wherein presence of the peak indicates that the subject has coronary artery disease or is at increased risk of developing coronary artery disease compared to a subject without the peak in the mass spectrum at between 6.5 kD and 6.55 kD;
• (vi) contacting HDL2 or HDL3 sub-fractions from a biological sample from the subject with an aortic smooth muscle cell, wherein the ability of the HDL2 or HDL3 sub-fractions to induce apoptosis of the aortic smooth muscle cell is indicative of the subject having or being at risk for developing coronary artery disease;
• or
• (vii) contacting HDL2 or HDL3 sub-fractions from a biological sample from the subject with an endothelial cell, wherein the ability of the HDL2 or HDL3 sub-fractions to induce expression of nitric oxide and/or ICAM-1 at a greater level than HDL2 or HDL3 sub-fractions from a biological sample from a subject without coronary artery disease is indicative of the subject having or being at risk for developing coronary artery disease.

A method for identifying a compound that inhibits the development of coronary artery disease and/or is useful in the treatment of coronary artery disease, the method comprising:

• (a) administering the compound to a subject exhibiting coronary artery disease;
• (b) obtaining a high density lipoprotein (HDL2) or high density lipoprotein3 (HDL3) sub-fraction from a biological sample from the subject;
• and
• (c) determining the molecular weight of the apolipoprotein C-I isoforms in the HDL2 or HDL3 sub-fractions of the sample,
• wherein the compound is determined to inhibit the development of coronary artery disease and/or be useful in the treatment of coronary artery disease if the molecular weight of the apolipoprotein C-I isoforms in the HDL2 or HDL3 sub-fractions of the sample is about the same molecular weight as apolipoprotein C-I isoforms in the HDL2 or HDL3 sub-fractions of an angiographically-normal subject.