Mark V. Sorensen

The Influence of Basal Metabolic Rate on Blood Pressure Among Indigenous Siberians

Hypertension is an important global health issue and is currently increasing at a rapid pace in most industrializing nations. Although a number of risk factors have been linked with the development of hypertension, including obesity, high dietary sodium, and chronic psychosocial stress, these factors cannot fully explain the variation in blood pressure and hypertension rates that occurs within and between populations. The present study uses data collected on adults from three indigenous Siberian populations (Evenki, Buryat, and Yakut [Sakha]) to test the hypothesis of Luke et al. (Hypertension 43 (2004) 555-560) that basal metabolic rate (BMR) and blood pressure are positively associated independent of body size. When adjusted for body size and composition, as well as potentially confounding variables such as age, smoking status, ethnicity, and degree of urbanization, BMR was positively correlated with systolic blood pressure (SBP; P < 0.01) and pulse pressure (PP; P < 0.01); BMR showed a trend with diastolic blood pressure (DBP; P = 0.08). Thus, higher BMR is associated with higher SBP and PP; this is opposite the well-documented inverse relationship between physical activity and blood pressure. If the influence of BMR on blood pressure is confirmed, the systematically elevated BMRs of indigenous Siberians may help explain the relatively high blood pressures and hypertension rates documented among native Siberians in the post-Soviet period. These findings underscore the importance of considering the influence of biological adaptation to regional environmental conditions in structuring health changes associated with economic development and lifestyle change.

Lifestyle Incongruity, Stress and Immune Function in Indigenous Siberians : The Health Impacts of Rapid Social and Economic Change

The purpose of this study was to investigate the impact of economic and cultural change on immune function and psychosocial stress in an indigenous Siberian population. We examined Epstein-Barr virus antibodies (EBV), an indirect biomarker of cell-mediated immune function, in venous whole blood samples collected from 143 Yakut (Sakha) herders (45 men and 98 women) in six communities using a cross-sectional study design. We modeled economic change through the analysis of lifestyle incongruity (LI), calculated as the disparity between socioeconomic status and material lifestyle, computed with two orthogonal scales: market and subsistence lifestyle. EBV antibody level was significantly negatively associated with both a market and a subsistence lifestyle, indicating higher cell-mediated immune function associated with higher material lifestyle scores. In contrast, LI was significantly positively associated with EBV antibodies indicating lower immune function, and suggesting higher psychosocial stress, among individuals with economic status in excess of material lifestyle. Individuals with lower incongruity scores (i.e., economic status at parity with material resources, or with material resources in excess of economic status) had significantly lower EBV antibodies. The findings suggest significant health impacts of changes in material well-being and shifting status and prestige markers on health during the transition to a market economy in Siberia. The findings also suggest that relative, as opposed to absolute, level of economic status or material wealth is more strongly related to stress in the Siberian context.

Reduced fat oxidation and obesity risks among the Buryat of Southern Siberia

Over the last 20 years, obesity and associated metabolic diseases have emerged as major global health problems. Among urbanizing populations of developing regions of the world, childhood undernutrition often coexists with adult overnutrition, a phenomenon known as the “dual nutritional burden”. A recent work (Frisancho 2003 : Am J Hum Biol 15:522–532) suggests that linear growth stunting in early childhood may contribute to adult obesity by reducing the bodys ability to oxidize fat. We test central aspects of this model drawing on data from 112 adult Buryat herders (53 males; 59 females) from Southern Siberia. The results are consistent with the predictions of the model, but only for women. Shorter Buryat women (height‐for‐age Z‐scores ≤ −1) have significantly lower fasting fat oxidation levels compared to their taller counterparts. Shorter women are also significantly heavier and fatter, and have higher serum lipid levels. Among all Buryat women, reduced fat oxidation is significantly correlated with percent body fatness, serum triglyceride levels, and serum leptin levels, after controlling for relevant covariates. Additionally, Buryat women with high dietary fat intakes and low fat oxidation are significantly fatter and have higher lipid and leptin levels than those with low fat intakes and high fat oxidation. These results suggest that developmental changes in fat oxidation may play a role in the origins of obesity among populations with high rates of linear growth stunting. Further longitudinal research is necessary to elucidate the pathways through which early‐life undernutrition may increase risks for adulthood obesity and cardiovascular disease. Am. J. Hum. Biol. 2009.

Coalescent simulations of Yakut mtDNA variation suggest small founding population

The Yakuts are a Turkic-speaking population from northeastern Siberia who are believed to have originated from ancient Turkic populations in South Siberia, based on archaeological and ethnohistorical evidence. In order to better understand Yakut origins, we modeled 25 demographic scenarios and tested by coalescent simulation whether any are consistent with the patterns of mtDNA diversity observed in present-day Yakuts. The models consist of either two simulated demes that represent Yakuts and a South Siberian ancestral population, or three demes that also include a regional Northeast Siberian population that served as a source of local gene flow into the Yakut deme. The model that produced the best fit to the observed data defined a founder group with an effective female population size of only 150 individuals that migrated northwards approximately 1,000 years BP and who experienced significant admixture with neighboring populations in Northeastern Siberia. These simulation results indicate a pronounced founder effect that was primarily kin-structured and reconcile reported discrepancies between Yakut mtDNA and Y chromosome diversity levels.

The effects of market integration on childhood growth and nutritional status: the dual burden of under- and over-nutrition in the Northern Ecuadorian Amazon.

Market integration is an important source of cultural change exposing indigenous populations to epidemiologic and nutrition transitions. As children and adolescents are biologically sensitive to the health effects of market integration, we examine community variation of anthropometric indicators of nutritional status and growth among a cross‐cultural sample of Kichwa, Shuar, Huaorani, and Cofán indigenous groups in the northern Ecuadorian Amazon.

Crude, Cash and Culture Change: The Huaorani of Amazonian Ecuador

In the Ecuadorian Amazon, the Huaorani are the indigenous group most recently assimilated into the country’s social, political, and economic order. With vast reserves of oil located under Huaorani land, this Native Amazonian population has quickly become integrated into national and international markets. The focus of this study is on one Huaorani community, Gareno, which is located along an oil road a few hours from the town of Tena, the capital of Napo Province. Community members were interviewed in order to better understand why they lived along the oil road and how they felt it impacted their daily lives. Responses showed that the residents have chosen to live and stay in Gareno specifically because of the health and education opportunities the road provides. The fact that they have chosen these benefits and economic opportunity over a pristine forest refutes the idea of the “noble savage,” which has been ingrained into Western society ever since Europeans first stepped on New World soil in the 15 th century. The image of the noble savage portrays indigenous people living in a so called “wilderness” as romanticized innocents in ecological harmony, isolated from the outside world, and uncorrupted by civilization. This view is inappropriate for groups like the Huaorani because it places them on an ecological pedestal and distorts their true condition. Rather than perpetuating this romanticized Western view of indigenous peoples, studies need to be conducted to better understand their contemporary challenges, responses, and opinions. As the people of Gareno look to further improve their quality of life through development, it is important to consider sustainable methods by which this can be completed as well as how national and international non-governmental organizations can facilitate such progress.

The origins of the yakut people: Evidence from mitochondrial DNA diversity

Abstract The Yakuts are a Turkic-speaking population of northeastern Siberia and based on archaeological and ethnohistorical evidence are believed to have originated from Turkic populations in south Siberia. To investigate this model, the HVS-I of the mitochondrial DNA control region was sequenced for 144 Yakut individuals representing seven communities from central Yakutia and compared to HVS-I data for other Asian populations. Haplogroups C and D comprise 75.7% of the Yakut sample, with only 9.7% assigned to west Eurasian lineages. The Ewens-Watterson homozygosity test revealed a significant deviation (P = 0.045) in the observed frequencies of common haplotypes relative to the expected values, indicating the genetic effects of a founder event. This is supported by a fragmented MJ network dominated by high-frequency haplotypes within haplogroups C and D. Nested cladistic analysis identified subhaplogroup D5a as the product of a long distance colonization event and potential founder lineage for the Yakuts, dating to approximately 1,630 years BP. SAMOVA analyses and MDS plot of genetic distances show close genetic affinities between the Yakuts and south Siberian populations, and thus affirming the south origin model.