Racial admixture and its impact on BMI and blood pressure in African and Mexican Americans

Abstract

Admixed populations such as African Americans and Hispanic Americans present both challenges and opportunities in genetic epidemiologic research. Because of variation in admixture levels among individuals, case-control association studies may be subject to stratification bias. On the other hand, admixed populations also present special opportunities both for examining the role of genetic and environmental factors for observed racial/ethnic differences, and for possibly mapping alleles that contribute to such differences. Here we examined the distribution and relationship of individual admixture (IA) estimates with BMI and three measures of blood pressure in two admixed populations in the NHLBI Family Blood Pressure Program (FBPP): African Americans and Mexican Americans. For the African Americans, we observed modest but significant differences in average African IA among four recruitment sites. We observed a slight excess of African IA among hypertensives compared to normotensives, and a positive (non-significant) regression of African IA on blood pressure in untreated participants. Within Mexican Americans, we found no difference in average IA between hypertensives and normotensives, but a positive (marginally significant) regression of African IA on diastolic blood pressure. We also observed a significant positive regression of Caucasian IA (and negative regression of Native American IA) on BMI. Our results are suggestive of genetic differences between Africans and non-Africans that influence blood pressure, but such effects are likely to be modest compared to environmental ones. Excess obesity among Native Americans compared to whites is not consistent with a simple genetic explanation.

Relationship between hypertension and admixture in post-menopausal African American and Hispanic American women

“…[2][3][4] Previous studies have also suggested that AFR admixture in AFA was associated with hypertension but either failed to reach statistical significance or showed only a modest effect. [6][7][8] This study shows statistically significant association of AFR admixture and hypertension in both AFA and HA population groups. Our study differs from previous studies with respect to having a much larger sample size and that our participants were restricted to adult post-menopausal women.…”

“…Previous studies have either not shown a statistically significant difference in African admixture within AFA subjects with and without hypertension 6,7 or have shown modest differences. 8 Although one group found hypertension association with specific African inherited chromosomal regions 6 these findings have not been supported by other studies. 7 In addition, these previous studies did not consider socioeconomic status (SES) as a possible confounder.…”

Socioeconomic Position, But Not African Genomic Ancestry, Is Associated With Blood Pressure in the Bambui-Epigen (Brazil) Cohort Study of Aging

“…To our knowledge, previous studies examining the association between hypertension or blood pressure and African [25][26][27][28][29] A large crosssectional study in the United States showed a slight excess of African genomic ancestry in hypertensives relative to normotensives and a modest positive relationship between African ancestry and DBP. 25 Yet another large cross-sectional study in the United States reported that European and African ancestry was not associated with diastolic or systolic blood pressure.…”

“…25 Yet another large cross-sectional study in the United States reported that European and African ancestry was not associated with diastolic or systolic blood pressure. 26 In addition, smaller studies conducted in black Americans and those from the Caribbean showed positive 27 or even absent 28,29 relationships between African ancestry and blood pressure or hypertension.…”

Disruptions in energy balance: Does nature overcome nurture?

“…Admixture mapping has been used to identify genes for cardiovascular disease risk [32], asthma [33], and prostate cancer [34] in African Americans, and genes for blood pressure [35], breast cancer [36], and lupus [37] in Hispanic Americans. In addition, the information of these AIMs is translated into a quantitative value that represents an estimate of the degree of the individual's ancestral background, known as an estimate of genetic admixture.…”