Saudi Cultural Missions Theses & Dissertations
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Item Restricted Exposure to Allergens and Proinflammatory Mediators Modulate Airway Epithelial Cell Innate Responses, Metabolism, and Physiology(University of Alberta, 2024) Alzahrani, Khadija Rashed; Vliagoftis, HarissiosLungs and airways health and protection depend on the integrity of airway epithelium. Insulin is a growth hormone that through activation of several signaling pathways play a central role to maintain cellular growth and activate metabolism. Airway epithelium is in constant exposure to inhaled agents like pathogens, allergens, pollutants, and particular matters. Airborne allergens like cockroach or house dust mite (HDM) contain proteases that can interact with airway epithelium and initiate immune responses through activation of airway epithelial cells and innate immune cells. Airway epithelium cytokines and innate immune cells promote activation of adaptive immune cells like Th2 lymphocytes that produce proinflammatory mediators like interleukin-4 (IL-4), IL-13, and IL-5. T helper 2 (Th2) cytokines amplify the immune responses and stimulate airway epithelial cells to release CCL chemotactic factors/eotaxins that attract eosinophils to the site of inflammation. Airway epithelium exposure to inhaled irritants and excessive inflammatory responses is known to disrupt epithelium integrity and exacerbate inflammatory responses. Th2 inflammation in asthma is associated with epithelial injury, epithelial remodeling, and metabolic alterations. Increased expression of inflammatory mediators tumor necrosis factor (TNF) and IL-6 in metabolically active tissues have been associated with cellular damage and insulin resistance. Inducible AECs local inflammation was shown to trigger systemic inflammation, insulin resistance, and impaired glucose metabolism, and the severity of inflammation correlated with impaired glucose metabolism. Several studies showed that insulin resistance increased the risk of aeroallergen sensitization and developing asthma-like symptoms. In this project we hypothesized that exposure of airway epithelial cells (AECs) to allergens and proinflammatory mediators may modulate Th2 immune cell responses, induce insulin resistance and metabolic shifts. First, we examined the effect of cockroach and house dust mite on IL-13 and IL-4-induced inflammatory responses. AECs were cultured and stimulated with cockroach or house dust mite, IL-13, IL-4, or a combination of an allergen and IL-13 or IL-4. IL-13 and IL-4 induced effects were measured. Then, we tested the effect of cockroach, house dust mite, TNF or IL-6-induced inflammatory responses on physiological epithelial changes and insulin-induced effects. Epithelial proliferation, resistance, energetic phenotype changes, and insulin induced activation of PI3K/Akt were examined. We showed that serine proteases of cockroach extract prevented IL-13-induced expression of eosinophil chemokine CCL26 from AECs. Depletion of CCL26 was previously shown to delay resolution of airway allergic inflammation which may result in prolonged eosinophilia. Prolonged inflammation was linked to altered metabolism and insulin action in several studies. We showed for the first time that house duct mite and TNF modulated insulin effects in AECs. TNF and HDM changed insulin-induced ATP production in AECs. Additionally, TNF reduced insulin-induced Akt phosphorylation, reduced epithelial barrier function and recovery after injury. Our data suggest that cockroach serine proteases and TNF may interfere with the Th2-mediated proinflammatory effects, regulate AECs energetic phenotype, and induce insulin resistance. These inflammatory and metabolic changes exacerbate the pathogenesis of asthma which may alter immune cell responses.5 0Item Restricted Effects of Physical Activity, Exercise and Breakfast Timing Manipulations on Glucose Metabolism in Healthy Adolescents(Saudi Digital Library, 2025-10-27) Afeef, Sahar; Tolfrey, Keith; Barrett, Laura A; Zakrzewski-Fruer, Julia KPostprandial hyperglycaemia is associated with an increased risk of type 2 diabetes (T2D) and cardiovascular disease (CVD). Even in healthy individuals, hyperglycaemia can adversely impact cardiometabolic health. Multiple rises and falls in glucose concentrations (i.e., glycaemic variability) may harm vascular health. Since most of the day is often spent in a postprandial state, measuring glucose concentrations over this critical period is vital to assess glycaemic profile. The novelty of continuous glucose monitoring (CGM) systems enables the assessment of glycaemic variability and postprandial glycaemia with reduced invasiveness and under free-living conditions. Since cardiometabolic risk factors were found to begin early in life, interventions focusing on moderating postprandial glycaemia and glycaemic variability through physical activity (PA) and diet manipulations should start early in life. Therefore, this thesis aimed to investigate postprandial glycaemic responses and glycaemic variability in relation to PA, exercise and breakfast timing manipulations in healthy adolescents aged 11 to 14 years. The first experimental study, Chapter 4, compared interstitial fluid glucose concentration ([ISFG]) obtained by CGM (i.e., FreeStyle Libre) against capillary plasma glucose concentration ([CPG], reference method) in response to an oral glucose tolerance test (OGTT, 5 time points including fasting) and treadmill exercise at different intensities (5 time points) in 17 healthy adolescents (9 girls, mean ± SD age 12.8 ± 0.9 y, BMI 18.4 ± 2.1 kg∙m−2). The overall mean absolute relative difference was 13.1 ± 8.5%. The [ISFG] was significantly lower than [CPG] 15 (−1.16 mmol·L−1, −9.7%) and 30 min (−0.74 mmol·L−1, −4.6%) after OGTT. Yet, post-OGTT glycaemic responses assessed by total (tAUC) and incremental (iAUC) area under the curves were not significantly different with trivial to small effect sizes (P ≥ 0.084, d = 0.14 – 0.45). These results indicate that CGM is an acceptable device reflecting postprandial glycaemic responses (i.e., AUC) that have high relevance to CVD risk. Non-significant site by timepoint interactions were observed during the treadmill exercise tests (P ≥ 0.614), indicating that the pattern of [ISFG] assessed by CGM was similar to [CPG] across the time points. Consequently, CGM were used in the two subsequent studies (Chapters 5 & 6). Using objective monitoring devices (i.e., Actigraph and CGM), Chapter 5 examined the associations of daily glycaemic variability with sedentary time and PA levels measured under free-living conditions in 37 healthy adolescents (24 girls, 12.7 ± 1.0 y, 20.1 ± 3.7 kg∙m−2). Glycaemic variability measures were not significantly associated with time spent sedentary and PA levels after accounting for age, sex, maturity status, accelerometer wear time and % body fat (P ≥ 0.071). However, there are some potential associations between glycaemic variability measures and sedentary time and MVPA. The findings suggest that accumulating 60 min MVPA daily tended to associate with 0.04 mmol∙L−1 reduction in StDevG (β = –0.00068, P = 0.087) and 0.7% reduction in glucose CV (β = –0.012038, P = 0.086). The magnitude of changes is small, and the metabolic health implications of such reductions are not known. Furthermore, the results suggest that accumulating 60 min of sedentary time seems to be associated with 0.3% higher glucose CV (β = 0.005692, P = 0.071), yet the same duration spent in MVPA tends to be associated with 0.7% lower glucose CV (β = –0.012038, P = 0.086), suggesting a greater impact of MVPA on glycaemic variability. Thus, encouraging reduced sedentary time combined with participation in MVPA may reduce glycaemic variability in healthy adolescents with small variations in blood glucose concentrations. Using CGM, Chapter 6 investigated the acute effect of school-based exercise bouts on postprandial glycaemia and 24 h glycaemic variability in 14 healthy adolescents (6 girls, 12.8 ± 1.0 y, 18.0 ± 1.6 kg∙m−2). The participants performed three experimental conditions in a fixed pre-determined order on three consecutive days: day 1) moderate intensity exercise condition (MIE, 30-min continuous brisk walking); day 2) no-exercise control condition (CON); day 3) high intensity intermittent exercise condition (HIIE, 30-min of 10 × 30-s sprints interspersed with 2.5-min brisk walking bouts). They performed the exercise conditions or no-exercise then consumed three standardised meals (breakfast and lunch at school and dinner at home) at fixed times. Thirty-minute bouts of MIE and HIIE did not change postprandial glycaemia (P ≥ 0.203) or 24-h glycaemic variability (P ≥ 0.281) significantly in this small sample of healthy adolescents. Although non-significant, the reduction in post-breakfast glucose iAUC was moderate for MIE (−0.24 mmol·L−1; P = 0.589; d = 0.77) and large for HIIE (−0.26 mmol·L−1; P = 0.444; d = 0.86) compared with CON. Non-significant, moderate (0.37 mmol·L−1; P = 0.219; d = 0.70) and large (0.42 mmol·L−1; P = 0.203; d = 0.81) increases in post-lunch glucose iAUC were observed for MIE and HIIE compared with CON. Furthermore, the effect size in post-dinner glucose iAUC were trivial to small between conditions, suggesting a short residual effect of exercise lasting for two meals. The mismatch between the probability values and effect sizes was a consequence of the COVID-reduced sample. The ramifications of these exercise effects are unclear and need to be confirmed in a larger sample of adolescents. The last experimental study, Chapter 7, examined the effect of early morning (EM-BC, 08:30) and mid-morning (MM-BC, 10:30) breakfast consumption compared with breakfast omission (BO) on the glycaemic and insulinaemic responses to the second meal (i.e., lunch) in 15 healthy adolescent girls (13.1 ± 0.8 y, 19.8 ± 3.1 kg∙m−2) who skipped breakfast habitually. The main finding from this study was that MM-BC significantly reduced post-lunch glucose tAUC (–10%; P = 0.002, d = 0.68) and iAUC (–36%; P < 0.001, d = 1.44) compared with BO, with moderate to large effects. However, the EM-BC resulted in non-significant reductions in post-lunch glucose tAUC (–5%; P = 0.195, d = 0.36) and iAUC (–15%; P = 0.077, d = 0.52) compared with BO, with small to moderate effects. Furthermore, MM-BC resulted in moderate reductions in post-lunch peak glucose compared with both BO (–1.03 mmol·L−1; P = 0.001, d = 0.74) and EM-BC (–1.03 mmol·L−1; P = 0.001, d = 0.74), with no significant difference between EM-BC and BO (P = 1.00, d = 0.001). Lastly, MM-BC resulted in a moderate, significant reduction in glycaemic variability across the 6 h experimental period compared with BO (–4.4%; P = 0.008, d = 0.56) yet the difference was trivial between EM-BC and BO (–1.1%; P = 1.00, d = 0.14). Although a second-meal effect was not found after EM-BC, the results of this study are important because they demonstrate that the timing of breakfast or the interval between the 1st and 2nd meals may be important for breakfast skipping girls. In summary, the information presented in this thesis extends the knowledge on glycaemic variability in relation to daily PA, exercise bouts and breakfast timing interventions in healthy adolescents. This thesis demonstrates an acceptable performance of FreeStyle Libre and the practicality of using this tool under free-living conditions with adolescents. This thesis provides further evidence of the potential benefit of engaging in daily MVPA and reducing sedentary time to lower glycaemic variability. In addition, thirty-minute bouts of MIE and HIIE reduced postprandial glycaemic response to a breakfast meal consumed in close proximity to exercise, but not to lunch or dinner, suggesting a short-term effect of exercise on glycaemia. Finally, consuming breakfast in the mid-morning (e.g., during the school break) may promote the metabolic health of girls who habitually skip breakfast by moderating the post-lunch glycaemic response.8 0Item Restricted Coordinated Oscillations In Glucose-Stimulated Insulin Secretion And Protein Phosphorylation In Clonal Pancreatic Β-Cells: Exploring Metabolic Control Of Exocytosis(2023) Alnuwaiser, Mohammad; Deeney, Jude T; Torentheim, Keith; Corkey, Barbara E.Introduction: Diabetes Mellitus affects 415 million people worldwide. It causes hyperglycemia due to impaired insulin production or action. It has been known for a long time that insulin secretion oscillates in vivo and in vitro. These oscillations in insulin release are impaired in diabetic patients. Oscillations in insulin secretion are driven by oscillations in metabolic coupling factors including the ATP/ADP ratio and intracellular Ca2+. The Aim of this thesis is to determine whether phosphorylation of proteins regulating β-cell lipid metabolism correlates with oscillations in insulin secretion. Methods: INS-1 cells were cultured in 4 and 11 mM glucose in 48-well plates. Insulin secretion was initiated with 12 mM glucose at timed intervals to generate an oscillation profile over 22 min. Media was collected and insulin was assayed by fluorescence based HTRF insulin assay. Cell protein was extracted with SDS-PAGE sample buffer, separated by electrophoresis and transferred to PVDF membrane for western blotting after SDS PAGE electophoresis. Phosphorylated and unphosphorylated acetyl-CoA carboxylase (ACC) and AMP-activated protein kinase (AMPK) were detected with specific rabbit antibodies (Cell Signaling). Protein bands were detected on a GE LAS-4000 gel imager using enhanced chemiluminescence. Bands were analyzed using ImageJ software (Schneider, Rasband and Eliceiri 2012). Results: Insulin oscillations were detected over the 22 min time course with at least three resolved peaks of insulin secretion for cells cultured in either 4 or 11 mM glucose. The oscillations were of a 5 min period under both culture conditions while the amplitude was 10-20 fold higher in 4 mM glucose cells. The amplitude was dependent on the insulin content of the cells such that when normalized to insulin content the average insulin secretion was well matched between the high and low glucose conditions. Oscillations in pACC/ACC and pAMPK/AMPK ratios were detected in cells cultured in both 4 mM and 11 mM glucose. In cells cultured at 4 mM glucose the pACC/ACC ratio oscillated with a similar period to insulin but was slightly left shifted such that pACC peaked before insulin. This correlation was not as strictly adhered to in cells cultured at high glucose. Oscillations in pAMPK/AMPK tracked well with those of pACC/ACC in cells cultured at both 4 and 11 mM. pAMPK/AMPK peaks were left-shifted relative to peaks in insulin secretion in cells cultured at 4 mM glucose while they seemed to be coincident with insulin peaks in cells cultured at 11 mM glucose. Conclusion: Oscillations in insulin secretion are accompanied by oscillations in ACC and AMPK phosphorylation to regulate lipid signals that amplify normal glucose-stimulated insulin secretion. Chronic excess nutrients may alter changes in ACC and AMPK phosphorylation resulting in impaired oscillations in insulin secretion. Regulation of lipid signals in the pancreatic β-cell may provide therapeutic benefit in the treatment of hyperinsulinemia, insulin resistance and Type 2 diabetes.10 0Item Restricted Thermal Stability Of Starch-Proanthocyanidin Complexes(Texas A&M University, 2023-03-03) Althawab, Suleiman Abdullah; Awika, Joseph MProanthocyanidins (PA) form poorly digestible complexes with starch via non-covalent linkages, showing promising potential to reduce the caloric density of the starch-rich products. The present study examined amylase degradation mechanism and hydrothermal stability of starch-PA complexes. Additionally, this study aimed to demonstrate the effect of Ebeam irradiation on enhancing the stability of starch-PA complex physiochemical properties and in vitro digestibility. Methylating PA as a means to enhance their hydrophobic interactions with starch was also investigated. Sorghum-derived PA was complexed with wheat starch, reconstituted into flour (10% gluten added) and processed into crackers and pancakes. In vitro digestion profile of the complexes and products were characterized. The molecular weight (MW) distribution after 20 min and 120 min of digestion revealed higher proportions of medium and high MW for PA treatments compared to controls. Debranching amylopectin further revealed higher retention of DP 11 – 30 chains in the digested starch-PA complexes than controls, suggesting amylopectin complexation contributed to reduced starch digestion. Starch-PA complexes retained reduced digestibility (50-56% higher resistant starch vs. controls) in the cracker, but not pancake model. However, removing gluten from the pancake formulation restored the reduced digestibility of the starch-PA complexes. This indicates the starch-PA complexes are stable to hydrothermal processing, but can be disrupted by hydrophobic gluten proteins under excess moisture conditions. Subjecting starch-PA treatments to Ebeam (2-50 kGy) increased MW compared to their controls (P<0.05) suggesting covalent crosslinking of starch polymers by PA. Amylose fraction of starch-PA treatments had the highest MW increase vs. controls (15-102%) after Ebeam treatment. Ebeam starch-PA treatments had significantly (P<0.01) lower starch digestibility compared to their controls (resistant starch of 2 kGy PA treatment was 85.9% vs. 44.4%, in the control). Our findings indicates that Ebeam likely facilitated PA-starch crosslinking via redox mediated reaction. Methylation conditions led to PA-PA crosslinking leading to polymers that were sterically bulky and unable to form V-complexed with starch. This work demonstrates that starch-PA complexes are stable under hydrothermal food processing, and that Ebeam can covalently crosslinking them and further expand their functionality.15 0