Saudi Cultural Missions Theses & Dissertations
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Item Restricted The use of plasminogen activator inhibitor-1 specific Affimers as a tool to modulate fibrin clot properties and thrombosis risk(Leeds University, 2024-03-05) Altalhi, Rawan; Ajjan, RamziThe ability to form a blood clot is critical for preventing blood loss following vessel injury. After restoring vascular integrity, the haemostatic system allows for the closure of impaired blood vessels, the preservation of blood in a fluid state, and the removal of clots. Blood clots are made up of a network of fibrin fibres that include platelets, red blood cells, and white blood cells. Imbalances and changes in coagulation factors, as well as the several components of the coagulation cascade, may have an effect on fibrinolysis. This turn may lead to increased risk of unwanted vascular occlusion through the failure to remove intravascular clots and maintain blood flow, consequently resulting in reduced blood supply to an organ. Hypofibrinolysis is a key abnormality in conditions associated with high vascular risk such as diabetes, contributing to the adverse vascular outcome in this population. Plasminogen activator inhibitor (PAI)-1 is an important regulator of the fibrinolytic process and levels of this antifibrinolytic protein are elevated in diabetes and insulin resistant states. An increase in PAI-1 levels results in impaired fibrinolysis and increases the risk of thrombus formation. Therefore, modulating PAI-1 activity has the potential to improve the fibrinolytic process and decrease intravascular clot formation. One difficulty with modulating PAI-1 function is the reliance of this protein on vitronectin that stabilises PAI-1 and enhances its function. I hypothesised that plasminogen activator inhibitor-1 specific Affimers, which are small synthetic proteins, may be used to modulate fibrinolysis, consequently reducing the risk of thrombosis. The main aims of my work were to i) isolate PAI-1- specific Affimers, ii) investigate the effects of PAI-1-specific Affimers on fibrinolysis, and iii) characterise the mechanistic pathways for Affimer-mediated modulation of clot lysis. My work shows that PAI-1 binding Affimers do not adequately modulate protein function and only Affimers that bind both PAI-1 and vitronectin demonstrate an ability to significantly alter both protein function and consequently the fibrinolytic process. I also explore the mechanistic pathways that are responsible for Affimer-mediated PAI- 1 inhibition, in the hope that this may help to develop effective therapies to reverse the hypofibrinolytic environment in high vascular risk conditions.32 0Item Restricted Assessing the in vitro dissolution rate of metformin from different commercially available tablets using distinct physiological pH media at different fast/fed states.(Saudi Digital Library, 2023-06-14) Alanazi, Abdulaziz; Allahham, AymanDiabetes is a chronic metabolic disorder characterized by uncontrolled blood sugar, where the body cannot produce enough insulin to compensate high blood sugar in the body. Metformin is considered first drug for type 2 diabetes in the guidelines, and is available under different brands. These brands must exhibit similar levels of dissolution-derived bioavailability under the same conditions. Hence, comparing the in vitro dissolution rate of different generic metformin brands, including Diabex, Metex, and Apo-metformin, all of which contain 500 mg of metformin in an extended-release formulation and have been approved as interchangeable generics by the FDA and the TGA. An in vitro dissolution test was conducted at different pH levels, namely 2.4, 6.8, and 7.4. Furthermore, the tablets were immersed in 900 ml of media with varying viscosity levels achieved by manipulating the hydroxypropyl methylcellulose (HPMC) concentration. The results revealed that all brands exhibited a reduced release of metformin under acidic pH conditions compared to alkaline conditions, where all brands demonstrated similar behaviour. Additionally, the release of metformin from the same brand in alkaline pH showed insignificant changes at different media viscosities. However, at pH 6.8 in an aqueous solution, there was a significant variation in the release of metformin between Apo-metformin and Diabex, the original brand. These findings suggest a deviation in the release profile of the active ingredient, which could be attributed to the use of different excipients in the matrix as part of the delivery system. Based on these results, it is recommended to conduct further fundamental in vitro analyses before proceeding to in vivo studies. These additional analyses are crucial for better understanding the behaviour and performance of the different generic metformin brands, particularly in terms of their drug release profiles.62 0Item Restricted The Role of the Built Environment in Physical Activity Changes and Cardiometabolic Outcomes Among Lifestyle Modification Intervention Participants(University of Pittsburgh, 2023-06-28) Bu Saad, Mohammed; Rockette-Wagner, BonnyINTRODUCTION: More novel approaches to improve health outcomes for at-risk individuals are needed as type 2 diabetes grows. Neighborhood walkability and physical activity (PA) have been found to be related in adult population research. However, whether walkability influences people's ability to change their lifestyle behaviors and improve their cardiometabolic outcomes as a result of a lifestyle intervention is unknown. METHODS: We examined the association between neighborhood walkability and the six-month changes in (1) physical activity and (2) cardiometabolic outcomes among individuals at risk of diabetes using two cohorts of participants (n=390) who were enrolled in DPP-based community lifestyle interventions (DPP-GLB). In addition, for participants (n=221) undergoing a DPP-based online lifestyle intervention in primary care settings (OCELOT study), we examined participants’ success in (3) meeting a step counts/day equivalent of the program PA goal and the role of neighborhood walkability in PA achievement at 12 months post-intervention. Regression analyses were applied (1: linear; 2: linear and logistic; and 3: logistic). RESULTS: For DPP-GLB participants, self-reported baseline PA levels were positively associated with greater neighborhood walkability. Over 6 months of intervention neighborhood walkability was inversely associated with PA change. Living in a car-dependent neighborhood versus walkable neighborhood was associated with a statistically significant greater increase in self-reported PA, leading to reduced differences in PA levels across neighborhood walkability categories. Neighborhood walkability was also inversely related to improvements in insulin and blood glucose, but positively associated with blood pressure improvements. In the OCELOT cohort, pedometer-measured PA goal achievement did not differ across the study arms (VLM-S: standard coaching; VLM-M: modulated coaching; OGR: control arm). Regarding PA goal achievement by neighborhood walkability, participants living in walkable neighborhoods (Very Walkable and Walker's Paradise) were more likely to meet the PA goal than those living in car-dependent neighborhoods. CONCLUSIONS: This dissertation provides valuable evidence regarding the association between neighborhood walkability and PA goal achievement and changes in cardiometabolic outcomes among adults at risk for or with T2DM while participating in a lifestyle intervention. These results suggest that prevention programs should incorporate contextual factors of participants' neighborhoods in their program materials and start considering multi-level intervention approaches.21 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 0