Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
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- Creators: School of Life Sciences
Description
There has been an alarming rise in the prevalence of obesity which has been attributed to the paralleled rise in consumption of high-fat foods. It’s commonly accepted that high-fat diets can lead to increased weight gain, however not all fats have the same physiological action. This study primarily focuses on the effect of canola oil, a monounsaturated fat, on energy homeostasis and body composition when it’s given as a supplement to a high-fat diet composed of saturated fatty acid. Rodent models were divided into three dietary groups: 1) low-fat diet (LFD), 2) high-fat diet (HFD) and 3) canola oils supplemented HFD (HF+CAN). After 4 weeks of dietary intervention, samples of epididymal fat, perinephric fat, and liver were analyzed across the three groups to see if the changes in energy homeostasis could be explained by the cellular behavior and composition of these tissues. Interestingly, the supplement of canola oil appeared to reverse the deleterious effects of a saturated fat diet, reverting energy intake, body weight gain and adipose tissue sizes to that (if not lower than that) of the LFD group. The only exception to this effect was the liver: the livers remained larger and fattier than those of the HFD. This occurrence is possibly due to a decrease in free fatty acid uptake in the adipose tissues—resulting in smaller adipose tissue sizes—and increased fatty acid uptake in the liver. The mechanism by which this occurs has yet to be elucidated and will be the primary focus of upcoming studies on the effect of monounsaturated fat on other diets.
ContributorsZuo, Connie Wanda (Author) / Washo-Krupps, Delon (Thesis director) / Deviche, Pierre (Committee member) / Herman, Richard (Committee member) / Barrett, The Honors College (Contributor) / Department of Chemistry and Biochemistry (Contributor) / School of Life Sciences (Contributor)
Created2015-05
Description
Type II diabetes is a serious, chronic metabolic disease that has serious impacts on both the health and quality of life in patients diagnosed with the disease. Type II diabetes is also a very prevalent disease both in the United States and around the world. There is still a lot that is unknown about Type II diabetes, and this study will aim to answer some of these questions. The question posed in this study is whether insulin resistance changes as a function of time after the start of a high fat diet. We hypothesized that peripheral insulin resistance would be observed in animals placed on a high fat diet; and peripheral insulin resistance would have a positive correlation with time. In order to test the hypotheses, four Sprague-Dawley male rats were placed on a high fat diet for 8 weeks, during which time they were subjected to three intraperitonal insulin tolerance tests ((NovoLogTM 1 U/kg). These three tests were conducted at baseline (week 1), week 4, and week 8 of the high fat diet. The test consisted of serially determining plasma glucose levels via a pin prick methodology, and exposing a droplet of blood to the test strip of a glucometer (ACCUCHEKTM, Roche Diagnostics). Two plasma glucose baselines were taken, and then every 15 minutes following insulin injection for one hour. Glucose disposal rates were then calculated by simply dividing the glucose levels at each time point by the baseline value, and multiplying by 100. Area under the curve data was calculated via definite integral. The area under the curve data was then subjected to a single analysis of variance (ANOVA), with a statistical significance threshold of p<0.05. The results of the study did not indicate the development of peripheral insulin resistance in the animals placed on a high fat diet. Insulin-mediated glucose disposal was about 50% at 30 minutes in all four animals, during all three testing periods. Furthermore, the ANOVA resulted in p=0.92, meaning that the data was not statistically significant. In conclusion, peripheral insulin resistance was not observed in the animals, meaning no determination could be made on the relation between time and insulin resistance.
ContributorsBrown, Kellen Andrew (Author) / Caplan, Michael (Thesis director) / Herman, Richard (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
It is presently believed that brown adipose tissue (BAT) is an important tissue in the control of obesity because it has the propensity to increase energy expenditure. The purpose of this study was to attempt to quantify the thermogenesis of BAT when four rats were exposed to a progression of low-fat to high-fat diet. Exogenous norepinephrine (NE) injections (dose of 0.25 mg/kg i.p.) were administered in order to elicit a temperature response, where increases in temperature indicate increased activity. Temperatures were measured via temperature sensing transponders that had been inserted at the following three sites: interscapular BAT (iBAT), the abdomen (core), and lower back (reference). Data showed increased BAT activity during acute (2-3 weeks) high fat diet (HFD) in comparison to low fat diet (LFD), but a moderate to marked decrease in BAT activity during chronic HFD (6-8 weeks) when compared to acute HFD. This suggests that while a HFD may initially stimulate BAT in the short-term, a long-term HFD diet may have negative effects on BAT activation.
ContributorsSivak, Hanna (Author) / Sweazea, Karen (Thesis director) / Herman, Richard (Committee member) / Caplan, Michael (Committee member) / School of Life Sciences (Contributor) / College of Integrative Sciences and Arts (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
Preliminary studies indicate that the use of dietary menthol may prevent excessive weight gain through the activation of the transient receptor potential melastatin family member 8 (TRPM8) ion channel. It has also been expressed that elevation of the core temperature (Tc) inducing mild hyperthermia via an increase in ambient temperature aids in a marked reduction of the drive to eat and weight gain. While caloric restriction (CR) aims to treat obesity and secondary sicknesses, weight regain is a common result during long term weight maintenance. The goal of these studies was to evaluate and identify if the menthol and mild hyperthermia mechanisms could couple synergistically to reduce or abrogate weight gain. Ambient temperature (Ta) was increased incrementally to identify the threshold in which rodents display mild hyperthermia. Our initial attempts at hyperthermia induction failed because of limitations in the environmental chamber. These trials fail to note a threshold at which elevated Tc is sustained for any period of time. The data suggests an ambient temperature of 36-38 °C would be appropriate to induce a mild hyperthermia. A mild hyperthermia is described as the elevation of Tc 2-3 ° above the hypothalamic set point. To facilitate future hyperthermia studies, an environmental chamber was designed. A wine cooler was converted to withstand the desired temperatures, through the use of heat tape, a proportional controller, and a translucent Plexiglas custom fit door. Beyond leveraging temperature to regulate weight gain, dietary changes including a comparison between standard chow food, high fat diet, and menthol supplemented chow food treatment illustrate a strong likelihood of weight gain variability. In this pilot study, weight gain expression when given a diet supplemented with menthol (1%) showed no statistical significance relative to a high fat diet nor chow food, however, it revealed a trend of reduced weight gain. It is assumed the combination of supplemental menthol and mild hyperthermia induction will exacerbate their effects.
ContributorsJohnsson, Kailin Alexis (Author) / Van Horn, Wade (Thesis director) / Herman, Richard (Committee member) / Towe, Bruce (Committee member) / Sanford School of Social and Family Dynamics (Contributor) / School of Life Sciences (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
This study was conducted to observe the effects of varying diets on weight regain after caloric restriction. Touted as a potentially effective non-invasive treatment to obesity, caloric restriction uses the gradual decrease in caloric intake to aid in weight loss. However, once a patient is taken off caloric restriction, a marked regain of weight regain occurs, nullifying the weight loss from caloric restriction. To find ways to suppress this weight regain, this study observed the effects of four different diets: low-fat diet (chow), high-fat diet (HFD), 0.5% concentration menthol infused chow, and 1% concentration menthol infused chow. Over a span of 3 years, 43 male Sprague-Dawley rats were placed through a strict feeding protocol: 3 weeks of chow food (3.1 kcal/gram), 8 or 12 weeks of HFD (5.42 kcal/gram), and caloric restriction for 4 weeks. Separate data analysis was conducted for the year 2017-2018, due to a slightly different protocol when compared to 2018-2019 and 2019-2020.
In 2017-2018, the results showed that 0.5% menthol (n=4) suppressed weight gain more effectively than both the baseline chow diet (n=4, p=0.022) and the HFD (n=4, p=0.027). Again in 2018-2020, the 0.5% menthol (n=6) showed promising results, showing significant suppression of weight gain when compared to chow (n=13, p=0.022). Unfortunately, the difference in weight gain in 1% menthol (n=6) was inconclusive when comparing to both chow and HFD. Although 1% menthol was inconclusive in its efficacy in suppressing weight regain, the promising results on 0.5% menthol show that menthol has the potential to be an effective treatment to both prevent rapid weight gain and maintain weight loss from caloric restriction.
In 2017-2018, the results showed that 0.5% menthol (n=4) suppressed weight gain more effectively than both the baseline chow diet (n=4, p=0.022) and the HFD (n=4, p=0.027). Again in 2018-2020, the 0.5% menthol (n=6) showed promising results, showing significant suppression of weight gain when compared to chow (n=13, p=0.022). Unfortunately, the difference in weight gain in 1% menthol (n=6) was inconclusive when comparing to both chow and HFD. Although 1% menthol was inconclusive in its efficacy in suppressing weight regain, the promising results on 0.5% menthol show that menthol has the potential to be an effective treatment to both prevent rapid weight gain and maintain weight loss from caloric restriction.
ContributorsLee, Justin (Author) / Van Horn, Wade (Thesis director) / Baluch, Debra (Committee member) / Herman, Richard (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05