Combined effects of small apolipoprotein (a) isoforms and small, dense LDL on coronary artery disease risk.
OBJECTIVE
Lipoprotein (a) [Lp(a)] consists of low-density lipoprotein (LDL) and apolipoprotein (a) [apo(a)]. Both Lp(a) constituents are well-recognized risk factors for coronary artery disease (CAD). This study investigates the interrelationship of apo(a) and LDL size, as well as their possible synergistic effect on the increase of CAD risk.


METHODS
One hundred nine CAD patients and 102 apparently healthy subjects were included in the study. Lp(a) concentration was measured using immunoturbidimetry. The sizes of apo(a) isoforms were determined by SDS-agarose gel electrophoresis followed by immunoblotting. LDL particle size was determined by gradient gel electrophoresis.


RESULTS
We found an inverse correlation between apo(a) size and Lp(a) concentration (r(2) = 31%, p <0.001 in the control group and r(2) = 35%, p <0.001 in the CAD group). Individuals with smaller apo(a) isoforms and small, dense LDL (sdLDL) >50% had the highest risk of CAD development (OR = 4.23, p = 0.017). The synergy index (SIM) for the combination of smaller apo(a) isoforms and sdLDL >50% was 1.2. Adjustment for Lp(a) and triacylglycerol concentrations eliminated smaller apo(a)/sdLDL >50% related risk (p = 0.233 and p = 0.09, respectively).


CONCLUSIONS
Smaller apo(a) isoforms appear to be superior to sdLDL for the assessment of CAD risk. Their combined effect is synergistic.
Zeljkovic
Aleksandra
A
Institute of Medical Biochemistry, Faculty of Pharmacy, Belgrade, Serbia.
Bogavac-Stanojevic
Natasa
N
Jelic-Ivanovic
Zorana
Z
Spasojevic-Kalimanovska
Vesna
V
Vekic
Jelena
J
Spasic
Slavica
S
D053241:Apoprotein(a) / Q000502:physiology*; D016022:Case-Control Studies; D003324:Coronary Artery Disease / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008077:Lipoproteins, LDL / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D020033:Protein Isoforms / Q000502:physiology*; D012307:Risk Factors
D008077:Lipoproteins, LDL; D020033:Protein Isoforms; D053241:Apoprotein(a)