Doctoral Dissertation Improvement: Effects of Social, Behavioral, and Biological Exposures on Fetal and Postnatal Skeletal Growth and Body Composition

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Significant differences in health outcomes reflecting social, environmental, and economic disadvantages persist and the biological mechanisms underlying these inequalities remain poorly understood. Descriptive epidemiologic studies identify that both intrauterine and early postnatal environments play a role in the transmission of health disparities across generations. This dissertation project by doctoral student Amanda Mummert (under the supervision of Dr. Michelle Lampl, Emory University) examines whether the specific exposures of chronic psychosocial stress and poor nutrition, fundamental disadvantages noted among populations exhibiting health disparities, have intergenerational effects on fetal and infant skeletal growth and body composition.The primary hypothesis of the study is that fetal and infant exposure to chronic stress and high calorie foods will lead to distinct deficiencies in skeletal growth and bone mineral density, as well as increased adiposity and decreased adiponectin production in infancy. Challenges to conducting this research in humans include our long reproductive periods and the invasiveness of the proposed research plan, which are overcome by testing this hypothesis in a translational model of human health. The research therefore utilizes an appropriate primate model, a sample of 56 Rhesus macaque (Macaca mulatta) maternal-infant pairs housed at the Yerkes National Primate Research Center. Ultrasonography, dual-energy X-ray absorptiometry, anthropometrics, and biomarker assays will be repeated on mothers and infants at 90 and 150 gestational days of age, as well as 3 and 6 postnatal months of age. These biological assessments will be accompanied by behavioral observations to document the occurrence of stress-like behaviors and mother-infant nursing interactions. Additionally, food intake for mothers and weaned infants will be continuously quantified through the use of automated feeders that dispense food in response to microchip signals. By exposing how innate physiology is impacted by two primary social determinants of health, nutrition and chronic stress, this research contributes to the Healthy People 2020 priority to better characterize the complex contributions of environment and biology to human health. While infectious disease remains a significant public health issue, the global burden of morbidity and mortality is deeply rooted in social and structural issues, including unemployment and poverty, a lack of social support, and chronic stress. It is imperative to investigate how these larger social factors 'get under the skin' and impact human health for public health planning purposes, particularly as chronic disease rates and health care costs continue to rise. In particular, this research is anticipated to reveal currently unknown biological mechanisms that contribute to long-term health inequalities that may serve as biomarkers for interpreting the effectiveness of public health interventions.