Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
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Item Effect of weight gain , diet and exercise on insulin sensitivity in Thoroughbred geldings.(2007-08-01) Quinn, Rachael; Hartsock, Thomas G; Burk, Amy O; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Insulin sensitivity (SI) in horses is affected by diet, exercise and obesity and has been implicated in metabolic disease. The objectives of this research were to assess the impact of BW gain on SI utilizing two diets known to differentially impact glucose dynamics, evaluate the contribution of light exercise to overall SI and relate changes in SI to BCS to identify the threshold at which SI declines to a level consistent with an increased risk of metabolic disease. Fifteen mature Thoroughbred geldings (BW 516 ± 13 kg, BCS 4.3 ± 0.1) were fed to gain 90.8 kg on a diet high in fat and fiber (HF, n = 6) starch and sugar (HS, n = 9). To assess SI, frequently sampled i.v. glucose tolerance tests were performed before treatment initiation (CFMM), at the start (TXMM) and end (ENDMM) of weight gain and following a period of minimal exercise. Using the minimal model of glucose dynamics, data from each test was used to estimate SI, glucose effectiveness (Sg) and the acute insulin response to glucose (AIRg). Final BW was 608 ± 12 kg and BCS was 7 ± 0.1. Diet had no effect on SI, AIRg or glucose effectiveness at CFMM. Within HF, SI, Sg and AIRg were unchanged at CFMM, TXMM and ENDMM. SI decreased at TXMM in HS (P = 0.05) and remained unchanged through ENDMM. SI in HS was lower than HF at TXMM (P = 0.01) and ENDMM (P = 0.07). At ENDMM, AIRg was higher in HS than HF (P = 0.01) and glucose effectiveness was reduced in both diets (P < 0.05). Following the minimal exercise period, SI decreased in HF (P = 0.03). These results indicate that diet may be more influential on SI than weight gain in mature Thoroughbred geldings. The higher SI in HF appears to be partially dependent on some level of physical activity. Because a BCS increase of 3 scores was not associated with a reduction in SI, the BCS where the perceived risk of metabolic disease is increased likely lies above that achieved in this study (BCS 7).Item EFFECT OF ENDURANCE EXERCISE TRAINING ON FASTING AND POSTPRANDIAL PLASMA ADIPONECTIN LEVELS(2005-07-12) Brandauer, Josef; Hagberg, James M; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The purpose of this study was to investigate the postprandial response of plasma adiponectin (AN) levels to a high-calorie, high-fat meal, in relatively healthy (free of diabetes, overt heart disease) sedentary 50- to 75-year-old men and women before and after a six-month endurance exercise training program (approximately 70% of VO2 max, three times per week). AN is an adipocyte-released polypeptide ("adipokine") whose physiological significance in insulin sensitivity and other health risk factors is well documented. VO2 max was significantly increased with training in both men and women (men, 27.0 ± 0.9 vs. 32.2 ± 1.2 mL/kg/min, p < 0.0001; women, 23.3 ± 1.0 vs. 27.1 ± 1.4 mL/kg/min, p = 0.0002), while % body fat was decreased (men, 29.9 ± 1.2 vs. 26.0 ± 1.3 %, p = 0.0010 ; women, 42.3 ± 1.5 vs. 39.5 ± 1.8 %, p < 0.0001). Fasting AN levels were higher in women than in men (gender main effect, p = 0.0138), and fasting as well as postprandial adiponectin levels decreased significantly with training in men (p = 0.014) but not in women. No postprandial changes in plasma AN levels were observed in either gender. Stepwise regression analysis showed insulin sensitivity to be the strongest predictor of fasting AN levels. Postprandial AN levels were mainly dependent on fasting AN concentrations. In conclusion, fasting plasma adiponectin levels decreased with exercise training in men in the present study, whereas they remained unchanged in women. Postprandial adiponectin levels did not change following consumption of a high-fat meal either before or after exercise training.Item Influence of Vitamin D Receptor Gene Polymorphisms on Changes in Insulin Sensitivity with Aerobic Exercise Training(2005-01-24) Harne, Amanda Janel; Hagberg, James M; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The purpose of the study was to examine the influence of the FokI and BsmI polymorphisms of the vitamin D receptor gene on changes in insulin sensitivity with aerobic exercise training in men and women at increased risk for type 2 diabetes mellitus (T2DM). Subjects were genotyped and underwent oral glucose tolerance tests before and after six months of training. Due to mis-genotyping of the BsmI polymorphism, results for that variant were not reported. There were no significant differences between FokI genotype groups in insulin sensitivity before or after training. However, among subjects who completed training, FF homozygotes had significantly higher baseline fasting glucose and insulin levels than f allele carriers. While the FokI polymorphism does not appear to mediate training-induced changes in indices of glucose and insulin metabolism, it may influence fasting glucose and insulin levels and the development of insulin resistance in individuals at increased risk for T2DM.