Predictors of lipoprotein(a) levels in a European and South Asian population in the Newcastle Heart Project.

Abstract

Understanding of the higher susceptibility of South Asians to coronary heart disease is limited. One explanation is the combination of high prevalence of insulin resistance with higher lipoprotein(a) levels. Lipoprotein(a) levels and genotypes in three South Asian groups aged 25-74 years (Indian, Pakistani, Bangladeshi) were compared with a European population in a cross-sectional study. Biochemical measurements included lipids, apolipoprotein A1 and B, glucose, insulin and fibrinogen. Insulin sensitivity was calculated using the homoeostasis model assessment method (HOMA). There was no significant difference in lipoprotein(a) levels between South Asian and European men. South Asian women combined had higher lipoprotein(a) levels than European women, a difference probably resulting from higher lipoprotein(a) levels in Pakistani women compared with Indian and Bangladeshi women. Fasting insulin and HOMA were negatively associated with Lp(a) in South Asians though the associations were statistically significant only in men. There were only modest associations between most cardiovascular risk factors and Lp(a). Twenty-seven apolipoprotein(a) size alleles were detected in the three South Asian groups ranging from 16 to 43 kringle-IV repeats. The apolipoprotein(a) size polymorphism explained 23% of the variability in lipoprotein(a) levels in South Asians. There were few nongenetic predictors of lipoprotein(a) levels in South Asians and Europeans. The lack of difference in Lp(a) between the South Asian and European men and the fact that differences between the women seemed to be confined to the Pakistani group offer little support to the hypothesis that higher Lp(a) levels contribute to the increased risk of heart disease in South Asians. Our findings do not support the hypothesis that susceptibility to heart disease in South Asians results from a combination of high insulin resistance and high Lp(a) levels.