Lipoprotein(a) as a potential causal genetic risk factor of cardiovascular disease: a rationale for increased efforts to understand its pathophysiology and develop targeted therapies

Abstract

Recent published studies have provided increasing evidence that lipoprotein(a) [Lp(a)] may be a potential causal, genetic, independent risk factor for cardiovascular disease (CVD). Lp(a) levels >25 mg/dl are present in ∼30% of Caucasians and 60% to 70% of Blacks. Lp(a) is composed of apolipoprotein B-100 and apolipoprotein (a) [(apo(a)]. Circulating Lp(a) levels are primarily influenced by the LPA gene without significant dietary or environmental effects, mediating CVD risk throughout the patient's lifetime. Recent clinical outcomes studies, meta-analyses, and Mendelian randomization studies, in which randomization of Lp(a) levels is achieved through the random assortment of LPA gene variants thereby removing confounders, have shown that genetically determined Lp(a) levels are continuously and linearly related to risk of CVD. Currently, Lp(a) pathophysiology is not fully understood, and specifically targeted therapies to lower Lp(a) are not available. We provide a rationale for increased basic and clinical investigational efforts to further understand Lp(a) pathophysiology and assess whether reducing Lp(a) levels minimizes CVD risk. First, a detailed understanding of Lp(a) synthesis and clearance has not been realized. Second, several mechanisms of atherogenicity are known to varying extent, but the relative contributions of each are not known. Lp(a) may be atherothrombotic through its low-density lipoprotein moiety, but also through apo(a), including its ability to be retained in the vessel wall and mediate pro-inflammatory and proapoptotic effects including those potentiated by its content of oxidized phospholipids, and antifibrinolytic effects. Finally, development of specific Lp(a)-lowering agents to potently lower Lp(a) will allow testing of mechanistic hypotheses in animal models and the design of randomized clinical trials to assess reduction in CVD. A convergence of academic, scientific, pharmaceutical, and National Institutes of Health priorities and efforts can make this a reality in the next decade.