College of Agriculture & Natural Resources

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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.

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    Regulation of Mitochondrial Metabolism and Lipogenesis
    (2021) Surugihalli, Chaitra; Sunny, Nishanth E; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Non-alcoholic fatty liver disease is one of the most common liver disorders with a global prevalence of over 25%. Fatty liver is the most common comorbidity of insulin resistance, obesity, and type 2 diabetes mellitus. During fatty liver, nutrient overload and the associated hyperinsulinemia results in elevated circulating free fatty acids and lipid accumulation in the liver. High rates of lipid accumulation in the liver is partly attributed to high rates of lipogenesis from carbohydrates, together with dysfunctional lipid oxidation. Further, these dysfunctional metabolic networks will induce oxidative stress and inflammation. Thus, understanding the metabolic mechanisms contributing towards the etiology of fatty liver and its associated morbidities is of major interest towards developing prevention and management strategies. This dissertation utilizes a combination of in-vivo (chicken and mice) and in-vitro (isolated mitochondria) systems with stable isotope-based methodologies to study metabolic regulation.Chicken embryos utilize yolk lipids (>45%), deriving over 90% of their energy through lipid oxidation for development. However, during the last few days of incubation and immediately after hatch, there is a substantial induction of lipogenesis. Despite the hepatic lipid overload, the synergistic remodeling of hepatic metabolic networks during embryonic-to-neonatal development blunted inflammatory onset, prevented accumulation of lipotoxic intermediates, and reduced reactive oxygen species production. Elevated plasma branched-chain amino acids (BCAAs) are a characteristic of insulin resistance and are relevant in predicting T2DM. Defects in BCAA degradation networks are also evident in several tissues during insulin resistance and associated co-morbidities. Furthermore, alterations in BCAA metabolism are associated with changes in lipogenesis and mitochondrial oxidative networks. We utilize a combination of isolated mitochondrial systems and stable isotope tracers in diet-induced mouse models of fatty liver, to determine its impact on mitochondrial metabolism and lipogenesis. In summary, the dissertation highlights i) the importance of the natural but dynamic remodeling of hepatic mitochondrial metabolism and lipogenesis during the efficient embryonic-to-neonatal transition in chicken ii) the significance of BCAAs as important regulators of hepatic mitochondrial lipid metabolism. Thus, these studies provide a platform to modulate hepatic metabolic networks and utilize the embryonic-to-neonatal transition phase and dietary intervention of BCAAs as management strategies to alleviate metabolic dysfunctions. 
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    INVESTIGATING THE ASSOCIATION OF PHTHALATE EXPOSURES AND ADVERSE REPRODUCTIVE HEALTH OUTCOMES IN A REPRESENTATIVE SAMPLE OF U.S. WOMEN
    (2017) Bibb, Katrina Alexandra; Alcala, Lesliam Q; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Phthalates are endocrine disrupting chemicals present in a large variety of consumer goods. There is supporting evidence from animal studies that exposure to phthalates affect the female reproductive system by disrupting the epigenome and folliculogenesis/oogenesis. Although women of reproductive age experience higher phthalate exposures versus males due to frequent use of cosmetics and personal care products (PCP), studies investigating reproductive health effects of these chemicals are scarce. In this study, a nationally representative sample was used to investigate the association between exposure to phthalates (primarily in PCPs and cosmetics) and subfertility in women aged 18-44. We observed significantly higher phthalate levels among minority women and positive associations between DBP exposure and subfertility in regressions when adjusted for important covariates This is the first study to use such a sample of women to study the effects of phthalates on subfertility. More epidemiological studies are needed to investigate phthalate levels among minorities.