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Effects of eight weeks of high-intensity interval training on blood glucose control, endothelial function, and visceral fat in obese adults

Description

Cardiovascular disease (CVD) is the number one cause of death in the United States and type 2 diabetes (T2D) and obesity lead to cardiovascular disease. Obese adults are more susceptible to CVD compared to their non-obese counterparts. Exercise training leads to large reductions in the risk of CVD and T2D. Recent evidence suggests high-intensity interval training (HIT) may yield similar or superior benefits in a shorter amount of time compared to traditional continuous exercise training. The purpose of this study was to compare the effects of HIT to continuous (CONT) exercise training for the improvement of endothelial function, glucose control, and visceral adipose tissue. Seventeen obese men (N=9) and women (N=8) were randomized to eight weeks of either HIT (N=9, age=34 years, BMI=37.6 kg/m2) or CONT (N=8, age=34 years, BMI=34.6 kg/m2) exercise 3 days/week for 8 weeks. Endothelial function was assessed via flow-mediated dilation (FMD), glucose control was assessed via continuous glucose monitoring (CGM), and visceral adipose tissue and body composition was measured with an iDXA. Incremental exercise testing was performed at baseline, 4 weeks, and 8 weeks. There were no changes in weight, fat mass, or visceral adipose tissue measured by the iDXA, but there was a significant reduction in body fat that did not differ by group (46±6.3 to 45.4±6.6%, P=0.025). HIT led to a significantly greater improvement in FMD compared to CONT exercise (HIT: 5.1 to 9.0%; CONT: 5.0 to 2.6%, P=0.006). Average 24-hour glucose was not improved over the whole group and there were no group x time interactions for CGM data (HIT: 103.9 to 98.2 mg/dl; CONT: 99.9 to 100.2 mg/dl, P>0.05). When statistical analysis included only the subjects who started with an average glucose at baseline > 100 mg/dl, there was a significant improvement in glucose control overall, but no group x time interaction (107.8 to 94.2 mg/dl, P=0.027). Eight weeks of HIT led to superior improvements in endothelial function and similar improvements in glucose control in obese subjects at risk for T2D and CVD. HIT was shown to have comparable or superior health benefits in this obese sample with a 36% lower total exercise time commitment.

ContributorsSawyer, Brandon J (Author) / Gaesser, Glenn A (Thesis advisor) / Shaibi, Gabriel (Committee member) / Lee, Chong (Committee member) / Swan, Pamela (Committee member) / Buman, Matthew (Committee member) / Arizona State University (Publisher)

Created2013

Contra-Insulin Effect in Gestational Diabetes on Glucose Uptake and Insulin Use for Human Placental Cells

Description

A significant amount of prior research has been conducted to investigate type 2 diabetes, the most prevalent form afflicting over 90% of diabetic individuals [6]. Yet, gestational diabetes is an understudied form of diabetes that is thought to share various attributes with type 2 diabetes. It was the aim of this project to investigate a proposed mechanism of the disease, the contra-insulin effect, through a cell-culture experiment. To address the question of whether glycemic and hormonal conditions of cell-culture media affect Hs 795.Pl morphology, cellular growth, and glucose uptake, immunocytochemistry (ICC) and a glucose uptake assay was performed. It was hypothesized that higher the presence of hormones, specifically lactogen, in cell culture media will exacerbate the contra-insulin effect, decreasing the glucose uptake of the Hs 795.Pl cells and inducing abhorrent cell morphology. Qualitatively, estradiol and cortisol had a severe impact on cellular morphology indicative of stress and death. As for glucose uptake, it was decreased when the hormones were isolated compared to all together with estradiol thought to be majorly inhibitory to insulin’s proper functioning. It was concluded that cell morphology, growth, and glucose uptake were detrimentally impacted by the gestational hormones, especially those of cortisol and estrogen.

ContributorsPickett, Sydney (Author) / Gilchrist, Alex (Co-author) / Holechek, Susan (Thesis director) / Clarke, Richard (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)

Created2023-05

Intramyocellular Lipids and the Progression of Muscular Insulin Resistance

Description

Diabetes is a disease characterized by reduced insulin action and secretion, leading to elevated blood glucose. In the 1990s, studies showed that intravenous injection of fatty acids led to a sharp negative response in insulin action that subsided hours after the injection. The molecule associated with diminished insulin signalling response was a byproduct of fatty acids, diacylglycerol. This dissertation is focused on the formulation of a model built around the known mechanisms of glucose and fatty acid storage and metabolism within myocytes, as well as downstream effects of diacylglycerol on insulin action. Data from euglycemic-hyperinsulinemic clamp with fatty acid infusion studies are used to validate the qualitative behavior of the model and estimate parameters. The model closely matches clinical data and suggests a new metric to determine quantitative measurements of insulin action downregulation. Analysis and numerical simulation of the long term, piecewise smooth system of ordinary differential equations demonstrates a discontinuous bifurcation implicating nutrient excess as a driver of muscular insulin resistance.

ContributorsBurkow, Daniel Harrison (Author) / Li, Jiaxu (Thesis advisor) / Castillo-Chavez, Carlos (Thesis advisor) / Kuang, Yang (Committee member) / Holechek, Susan (Committee member) / Arizona State University (Publisher)

Created2017