Abstract
The apolipoprotein (a) [apo(a)] gene encodes a protein component of lipoprotein (a) [Lp(a)] . To study the implications of Lp (a), we examined plasma Lp (a) levels and molecular weights (MW) of apo (a) in patients with cerebrovascular disease (CVD), or central retinal artery occlusion (CRAO). Mean Lp (a) concentrations were higher in the CVD cases with atherothrombotic brain infarction than in those with brain hemorrhage and lacunar infarction. Mean Lp (a) concentrations were also significantly higher in the CRAO cases than in the controls. Lp (a) levels higher than 30 mg/dl were more frequent in the CRAO cases than in the controls. Lp (a) concentrations correlated significantly with low-MW isoforms of apo (a) in these patients. We subclassified the apo (a) gene into four types (A-D) by polymorphisms in the 5'-flanking region, measured plasma Lp (a) concentrations, and examined the expression of the gene by in vitro assay. Homozygotes of type C had higher Lp (a) levels than those of type D in vivo, and the relative expression of type C was higher than that of type D in vitro. Thus, Lp (a) concentrations are genetically determined by extensive polymorphisms in both the 5'-alleles and the numbers of Kringle 4 repeats, and hyper-Lp (a) -emia is a risk factor for thrombosis of various types of vessels.
