Genome-Wide Characterization of Arabian Peninsula Populations: Shedding Light on the History of a Fundamental Bridge between Continents

The Arabian Peninsula (AP) was an important crossroad between Africa, Asia, and Europe, being the cradle of the structure defining these main human population groups, and a continuing path for their admixture. The screening of 741,000 variants in 420 Arabians and 80 Iranians allowed us to quantify the dominant sub-Saharan African admixture in the west of the peninsula, whereas South Asian and Levantine/European influence was stronger in the east, leading to a rift between western and eastern sides of the Peninsula. Dating of the admixture events indicated that Indian Ocean slave trade and Islamization periods were important moments in the genetic makeup of the region. The western–eastern axis was also observable in terms of positive selection of diversity conferring lactose tolerance, with the West AP developing local adaptation and the East AP acquiring the derived allele selected in European populations and existing in South Asia. African selected malaria resistance through the DARC gene was enriched in all Arabian genomes, especially in the western part. Clear European influences associated with skin and eye color were equally frequent across the Peninsula.

Alterations in Hemoglobin and Serum 25-hydroxyvitamin D are Related Before and After Weight Loss Independent of African Admixture

African American (AA) and European American (EA) women often exhibit differences in hemoglobin (Hb) and 25-hydroxyvitamin D [25(OH)D], both of which can be altered by calorie restriction leading to weight loss. Given these known differences, it is of clinical interest to examine the potential for race-specific, adverse responses to weight loss. Sixty-four overweight (BMI 27–29.9 kg/m2), premenopausal women consumed a standardized, very-low calorie diet to reduce BMI < 25 kg/m2. Ancestry informative markers provided estimates of African admixture, an objective mean of expressing race. Blood sampling and anthropometric measures were performed at baseline and upon meeting target BMI. At baseline, in the overweight state, Hb (g/dL) (AA, 11.7 ± 0.9 vs. EA, 12.5 ± 0.8; p < .01) and 25(OH)D (nmol/L) (AA, 35.7 ± 12.9 vs. EA, 57.0 ± 20.0; p < .01) were lower in AAs. After weight loss, Hb decreased (AA, -0.5 ± 0.7 vs. EA, -0.4 ± 0.6; p = .48) to a similar extent among races. Conversely, 25(OH)D increased (AA, 43.4 ± 14.0 vs. EA 68.2 ± 24.3; p < .01) though the magnitude of change (Δ) was not different (AA, +7.8 ± 13.5 vs. EA, +11.2 ± 16.7; p = .37) between races. Multiple linear regression revealed a positive association between ΔHb and Δ25(OH)D (r = .386; p < .01) adjusted for African admixture, Δtestosterone, and Δbody fat%. Path analyses revealed a significant indirect effect of Δbody fat% on ΔHb through Δ25(OH)D, β =-0.023, CI [-0.06, -0.004]. Following 15% weight loss, participants with the largest increase in serum 25(OH)D exhibited the smallest decrease in Hb. Future research should clarify the optimal degree of calorie restriction to stimulate weight loss while mitigating the potential risk of anemia associated with dieting efforts.