Abstract 13660: Lp(a) is Associated With Coronary Artery Calcification in a Population With Exceptionally Low Cardiovascular Disease Risk

Introduction: The Tsimane forager-horticulturalists of Bolivia are highly physically active, carry high infectious disease burdens, and have the lowest reported population levels of coronary artery calcium (CAC), as well as relatively low cholesterol (LDL, HDL, total) levels. In industrialized populations, lipoprotein(a)—Lp(a)— is strongly predictive of coronary artery and aortic valve calcification (AVC). However, these relationships have not been assessed in this non-urban population. Hypothesis: We hypothesize that, despite the very low levels of CAC seen in the Tsimane, Lp(a) is higher in those with CAC and AVC but overall lower in Tsimane compared to a US comparator population (CARDIA). Methods: CAC and AVC were measured by non-contrast cardiac CT in 917 Tsimane (15.5% CAC positive, 21.0% AVC positive). A subset of 98 Individuals with and without CAC or AVC had serum Lp(a) analyzed (median age 63 yrs, range 41-91 yrs, 67% male) using a standard double monoclonal antibody ELISA at the Northwest Lipid Metabolism and Diabetes Research Laboratory (University of Washington). Individuals with CAC and AVC were oversampled (45.9% CAC positive, and 76.7% with AVC; 10% with neither) to ensure statistical power. Results: Overall, Tsimane had significantly lower levels of Lp(a) than CARDIA white males (Tsimane male median 16.5 nmol/L vs US median 19.4 nmol/L; p<0.001) and CARDIA white females (Tsimane female median 11.5 nmol/L vs US median 21.9 nmol/L; p<0.001), despite oversampling Tsimane with CAC and AVC. While Tsimane Lp(a) was low, individuals with CAC had significantly higher Lp(a) (p=0.030) controlling for age, sex, and body fat. Tsimane with no CAC had a median Lp(a) of 12.2 nmol/L, while those with any CAC signal had a median Lp(a) of 17.7 nmol/L. There was no association between AVC and Lp(a). Conclusions: While the Tsimane have lower levels of both CAC and Lp(a) than US adults, Lp(a) is significantly higher in Tsimane with CAC. The absence of association between Lp(a) and AVC may indicate that among the Tsimane, the etiology of AVC may be less tied to Lp(a) than in industrial populations. These results suggest that Lp(a) is associated with arterial calcification even in patients with low overall cardiovascular disease risk.