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Lp (a) levels and apo (a) phenotypes in urban black South African men
M E Carstens1, L J Burgess, J J Taljaard
1Department of Chemical Pathology, University of Stellenbosch, Tygerberg, W Cape.
Objective:
To investigate the lipoprotein (a) (Lp (a)) levels and apolipoprotein (a) (apo (a)) phenotypes in a group of urban black South African men.
Design:
Cross-sectional design.
Setting:
Lead acid battery plant, East London, Eastern Cape.
Participants:
Blood samples from a study on the association between lead and renal failure were kindly donated for the present study and 111 of the donors participated (K Steyn-personal communication).
Outcome Measures:
Lp (a) levels and apo (a) phenotypes.
Results:
Three groups were identified: those with normal (< 300 U/l), intermediate (300-700 U/l) and high (> 700 U/l) plasma Lp (a) concentrations. Nine apo (a) phenotypes and 26 combinations thereof could be discerned. Apart from the single- and double-band phenotypes described before, triple-band phenotypes were also present. As the Lp (a) values increased, the relative frequency of the single-band phenotype decreased, whereas the relative frequency of the double-band phenotype increased. The relative frequency of the triple-band phenotype was highest in the group with high Lp (a) concentrations. No correlation was evident between the size of the apo (a) isoforms and the Lp (a) concentrations.
Conclusions:
Raised plasma Lp (a) levels have been associated with coronary heart disease (CHD). In addition, it has been proposed that the apo (a) gene determined plasma Lp (a) concentrations. These studies were performed using plasma from white subjects. CHD is uncommon in black South Africans. The reason may be that, given the lack of relationship between the size of the apo (a) isoforms and the Lp (a) concentrations observed in the present study, factors other than the isoform size may determine the Lp (a) levels in this particular ethnic group.