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Description
There has long been a link tied between obesity and such pathological conditions as nonalcoholic fatty liver disease and type two diabetes. Studies have shown that feeding rats a diet high in fat results in hepatic steatosis and steatohepatitis. Using a novel short term diet of six weeks with male adolescent Sprague-Dawley rats, our laboratory sought to investigate the early effects of high fat intake on the liver. Prior findings in our laboratory found that a high fat diet (HFD) leads to nonalcoholic fatty liver disease as well as other symptoms of metabolic syndrome. This study hypothesized that rats fed a 60% HFD for 6 weeks, unlike a high sucrose or standard chow diet, would have an elevated expression of pro-inflammatory cytokines associated with steatohepatitis. TNF-α, TLR4 and XBP1 were chosen for their link to hepatic inflammation. The results of this study found that contrary to the hypothesis, the high fat diet did not induce significant changes in the expression of any inflammatory marker in comparison to a high sucrose or control chow diet.
ContributorsCalhoun, Matthew (Author) / Sweazea, Karen (Thesis director) / Deviche, Pierre (Reviewer) / Barrett, The Honors College (Contributor)
Created2015-05
Description
Prior studies of Mourning Doves have observed no changed in glucose in response to either a high fat “chow” diet or a white bread diet. In the current feeding study, we fed doves an urban diet, high in carbohydrates, fat, and sodium, which is representative of typical American nutrition accessible to the avian population in an urbanized environment. Based on studies of other avian species that examined the effects of an urban diet on physiology, I hypothesized that doves fed an urban diet would have increased plasma glucose and sodium, which would promote an increase in plasma osmolality. This hypothesis was based on preliminary data that found birds fed an urban diet developed impaired vasodilation compared to seed diet control birds. Therefore, differences in plasma glucose, sodium, and osmolality were examined as increases may contribute to the impairment. Adult doves of both sexes were captured on the Arizona State University, Tempe campus. Doves were placed in two dietary groups: an urban diet consisting of a 50/50 ratio of French fries and nutritionally-balanced bird seed (n=7) and a control group of only the seed diet (n=6). Following the four-week diets, birds were euthanized, and cardiac plasma samples were collected from birds to measure glucose, sodium, and osmolality. There were no significant differences between the two study groups in plasma glucose concentration (p=0.445), sodium concentration (p=0.731), or osmolality (p=0.692). Sodium concentrations were signficantly more variable in birds consuming a seed diet than those that were provided the mixed French fry and seed diet (p=0.014). These results suggest that glucose, sodium, and osmolality likely do not contribute to the altered vasodilation of doves fed an urban diet and that such a diet may not be as detrimental to the doves health given their phenotypic flexibility.
ContributorsKayata, Lana (Author) / Sweazea, Karen (Thesis director) / Deviche, Pierre (Committee member) / Basile, Anthony (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
Birds have the highest blood glucose concentrations of all vertebrates. Meanwhile, birds do not develop the same physiological complications (e.g., increased oxidative stress and glycation) that mammals do when blood glucose is elevated (i.e., diabetes). Therefore, birds may serve as a negative model animal for hyperglycemic complications. The physiological reason for high blood glucose in birds remains largely unknown although several unique characteristics of birds may contribute including a lack of the insulin responsive glucose transport protein, relatively high glucagon concentrations, as well as reliance on fatty acids to sustain the high energetic demands of flight. In breaking down triglycerides for energy, glycerol is liberated, which can be converted to glucose through a process called gluconeogenesis. In addition, the extent to which birds maintain homeostatic control over blood glucose in response to extreme dietary interventions remains unclear and few dietary studies have been conducted in wild-caught birds. Using Mourning Doves (Zenaida macroura) as a model organism, this dissertation tests four hypotheses: 1) Gluconeogenesis contributes to high circulating blood glucose concentration; 2-4) similar to mammals, a fully refined carbohydrate (i.e., white bread diet); a high saturated fat diet (60% kcal from fat); and an urban-type diet comprised of a 1:1 ratio of French fries and birds seed will increase blood glucose compared to a nutritionally-balanced diet after a four-week duration. Contrary to the hypothesis, 150 mg/kg Metformin (which inhibits glycerol gluconeogenesis) increased blood glucose, but 300 mg/kg resulted in no change. However, when 2.5 mg/kg of 1,4-dideoxy-1,4-imino-D-arabinitol (DAB; a glycogenolysis inhibitor) was given with 150 mg/kg of Metformin, blood glucose was not different from the control (50 ul water). This suggests that glycerol gluconeogenesis does not contribute to the naturally high blood glucose in birds and that a low dose of Metformin may increase the rate of glycogenolysis. In addition, all three experimental diets failed to alter blood glucose compared to control diets. Collectively, these results suggest that, in addition to a negative model for diabetes complications, birds can also serve a negative model for diet-induced hyperglycemia. Future research should further examine dietary manipulation in birds while controlling for and examining different variables (e.g., species, sex, duration, diet composition, urbanization).
ContributorsBasile, Anthony Joseph (Author) / Sweazea, Karen L (Thesis advisor) / Deviche, Pierre (Committee member) / Johnston, Carol (Committee member) / Trumble, Ben (Committee member) / Parrington, Diane J (Committee member) / Arizona State University (Publisher)
Created2022