Cardiovascular disease is the most common cause of morbidity and mortality in type 2 diabetes. Short-term studies of glucagon-like peptide-1 (GLP-1)-targeted therapies suggest potential beneficial effects on cardiovascular outcomes. The mechanism behind this unexpectedly rapid effect is not known. In this study, full-length human GLP-1 receptor (GLP-1R) mRNA was cloned and sequenced from a human megakaryocyte cell line. Quantitative RT-PCR results showed that expression levels were comparable to other GLP-1R expressing tissues. Furthermore, incubation with GLP-1 and the GLP-1R agonist exenatide elicited a cAMP response in these cells. As megakaryocytes are the cellular precursors of platelets, the effect of GLP-1 and exenatide were studied in gel-filtered human platelet aggregation, where they were both shown to have an inhibitory effect on thrombin-stimulated platelet aggregation. Platelet inhibition by GLP-1 and GLP-1R agonists presents a potential mechanism for the reduced incidence of atherothrombotic events thought to be associated with GLP-1-targeted therapies.

Emerging evidence has shown that an abnormal postprandial accumulation of dietary tat IS atherogenic. The aim of this study is to measure triacylglycerol (TAG) kinetics in endogenous and exogenous lipoproteins in both fed and fasted states using stable isotopes.

Loss of glucose-stimulated insulin secretion (GSIS) from the pancreatic beta-cells is one of the earliest detectable defects in the pathogenesis of type 2 diabetes. However, despite its relevance, the mechanisms that govern GSIS are still not completely understood. ARNT/HIF-1β is a member of the bHLH-PAS family of transcription factors, with a prominent role in the transcriptional regulation of enzymes required for the metabolism of xenobiotics as well as regulation of genes that are critical for cellular responses to hypoxia. Recent research has uncovered a previously unknown function for ARNT/HIF-1β in the pancreatic beta-cells, where the gene was found to be 90% down-regulated in human type 2 diabetic islets and loss of ARNT/HIF-1β protein leads to defective GSIS in pancreatic beta-cells of mice. The main focus of this thesis was to understand the mechanisms by which ARNT/HIF-1β maintains normal GSIS from pancreatic beta-cells and understand how loss of ARNT/HIF-1β leads to beta-cell dysfunction and type 2 diabetes in mice. ARNT/HIF-1β was found to positively regulate GSIS in both INS-1 derived 832/13 cell line and mice islets. In the 832/13 cells, loss of ARNT/HIF-1β leads to a reduction in glycolysis without affecting the glucose oxidation and the ATP/ADP ratio suggesting that the regulation of GSIS takes place in a manner that is independent of the KATP channels. In order to further assess the mechanism of lowered GSIS in the absence of ARNT/HIF-1β in the 832/13 cells, a metabolite profiling was performed which revealed a significant reduction in the metabolite levels of glycolysis and the TCA cycle intermediates and glucose-induced fatty acid production, suggesting the involvement of ARNT/HIF-1β in regulating glucose-stimulated anaplerosis, which is believed to play a key role in the regulation of GSIS from the pancreatic beta-cells. The changes in metabolite levels in the absence of ARNT/HIF-1β were associated with corresponding changes in the gene expression pattern of key enzymes regulating glycolysis, the TCA cycle and fatty acid synthesis in beta-cells. In an attempt to understand how loss of ARNT/HIF-1β leads to beta-cell dysfunction and type 2 diabetes in mice, a pancreatic beta-cell specific ARNT/HIF-1β knock out mouse (β-ARNT KO) was generated using the Cre-loxP technology. Functional characterization of islets from both male and female β-ARNT KO mice revealed a significant impairment in GSIS, which was attributed due to a small, but significant reduction in rise in intracellular calcium upon glucose stimulation. Further analysis revealed reduced secretory response to glucose in the presence of KCl and diazoxide indicating a defect in the amplifying pathway of GSIS in β-ARNT KO islets. Expression of pyruvate carboxylase (PC) was significantly reduced in β-ARNT KO islets suggesting possible impairments in anaplerosis and consistent with this, defect in GSIS in β-ARNT KO islets could be almost completely rescued by treatment with membrane permeable TCA intermediates. Surprisingly, both male and female β-ARNT KO mice have normal glucose homeostasis. In an attempt to assess how β-ARNT KO mice maintained normal blood glucose levels, indirect calorimetry was used to understand changes in whole-body energy expenditure. This investigation revealed that β-ARNT KO mice exhibited a small but significant increase in respiratory exchange ratio (RER), suggesting a preference in utilizing carbohydrates as a fuel source, possibly leading to improved glucose uptake from the blood stream. Response to exogenous insulin was completely normal in β-ARNT KO mice suggesting intact functioning of the skeletal muscles. To conclude, based on our in vitro data, we believe that ARNT/HIF-1β plays an indispensable role in maintaining normal beta-cell secretory function, however, results from β-ARNT KO mice indicates that these mice are protected from the adverse effects of hyperglycemia. Although loss of ARNT/HIF-1β alone is not sufficient for the genesis of type 2 diabetes, it creates a perfect storm in the pancreatic beta-cells that may eventually lead to an imbalance in the whole body glucose homeostasis. Our study provides significant information to the scientific community that engages in assessing the pharmacological potential of gene targets for the treatment of type 2 diabetes.

Background. Estimates are that one third of children will develop type 2 diabetes in their lifetime. Lifestyle changes, including physical activity are established effective tools to prevent and manage type 2 diabetes in adults but the evidence in youth is lacking. Several key questions remain including: (1) Can youth with type 2 diabetes achieve target glycemic control with lifestyle changes alone? (2) Is type 2 diabetes in youth associated with low physical activity and cardiorespiratory fitness? and (3) What is the appropriate intensity of physical activity to reduce the risk for type 2 diabetes in overweight youth? Methods. Three studies were conducted to answer these questions: i) a retrospective chart review to determine the clinical efficacy of lifestyle monotherapy to manage glycemia in youth newly diagnosed with type 2 diabetes; ii) a cross sectional study to test the association between physical activity, cardiorespiratory fitness and type 2 diabetes risk factors in youth; and iii) a randomized controlled trial of physical activity designed to determine the training intensity required to improve insulin resistance and reduce intrahepatic lipid content in overweight youth at risk for type 2 diabetes (interim results presented). Results. Study A. Over 50% of youth newly diagnosed with type 2 diabetes and glycosylated hemoglobin ≤9% were able to achieve target glycemic control for as long as 12 months with lifestyle monotherapy. Study B. Physical activity levels (4905±2075 vs. 6937±2521 vs. 8908±2949 steps/day, p<0.05 vs. healthy weight youth) and cardiorespiratory fitness (23.4±5.9 vs. 26.7±6.0 vs. 36±6.6 ml/kg/min, ii p<0.05) are lower in youth with type 2 diabetes versus overweight and healthy weight controls. Intrahepatic lipid is significantly higher (13.0%±14.1 vs. 5.6%±6.2 vs. 1.4%±1.4, p<0.05) and inversely associated with insulin sensitivity (r = -0.40, p<0.001). Study C. Interim analyses present promising trends from a 6-month physical activity intervention. Conclusions. Lifestyle therapy can be an effective tool to manage new-onset diabetes in certain youth, and is also important in the prevention of type 2 diabetes in youth. Youth with type 2 diabetes are characterized by low levels of physical activity and cardiorespiratory fitness. Interim results are presented from a randomized controlled physical activity trial that we anticipate at completion will provide promising data to guide development of community-based programming to reduce risk for type 2 diabetes in overweight youth.

Background: A novel mutation (V205M) within the KCNQ1 gene was previously delineated and confirmed to predispose to long QT syndrome (LQTS) in a First Nations community in Northern British Columbia (Gitxsan). LQTS is an autosomal dominant genetic disease that is named for the elongation of the ECG (electrocardiogram) Q-T interval, corrected for rate, but is reflective of delayed repolarization predisposing to LQTS. Clinically, LQTS presents as sudden loss of consciousness (fainting, seizures) and sudden death. KCNQ1 is responsible in part for IKs the slow rectifying potassium channel in the heart, and also accounts for about 30% percent of all genetically confirmed cases of LQTS. The KCNQ1 gene is also expressed in the pancreas, and recent Genome Wide Association Studies (GWAS) have identified variants found within the KCNQ1 gene to be strongly associated with type 2 diabetes (T2D) in Asian and European populations. In Canada, and around the world, Indigenous populations have the higher rates of T2D. We set out to determine if the V205M mutation could influence the development of T2D in this First Nations population. Methods: Participants were recruited from a contact data base from the original study (entitled ‘The Impact of Long QT on First Nations People of Northern British Columbia’) and invited to determine if their KCNQ1 mutation status influenced their HbA1c values, and therefore risk for diabetes. Body mass index (BMI), waist circumference (WC), exercise levels and HbA1c test values were collected from each participant. Sixty-five participants (18 mutation positive and 47 mutation negative) were included in this sub-study. Results: Adjusting for anthropometric measurements, V205M+ participants were almost ten times more likely to attain an ‘at-risk’ (or ‘pre-diabetic’) HbA1c value (adjusted OR: 9.62; p=0.002; CI: 2.23-41.46). Although there was no difference in average HbA1C levels (p=0.963). The distribution of values was markedly different between those in the mutation positive vs mutation negative group. Conclusion: Although it is premature to declare a true risk for diabetes in this cross-sectional study, our results suggest that HbA1C levels are influenced by the presence of the V205M mutation, and further study is indicated to determine if insulin secretion is affected in these individuals. This work has potential implications for others with LQTS who might have altered glycemic control as a result of mutations in KCNQ1. Furthermore, in this First Nations population, broader health implications might need to be considered for those with the V205M mutation. / Graduate

Dietary proteins from Atlantic salmon and cod have previously been shown to have antidiabetic effects. Since dietary proteins are digested into small peptides before being absorbed through the intestinal mucosa, it is reasonable to deduce that the antidiabetic effect is due to enzymatically-digested peptides rather than the proteins themselves. The aim of this study was to develop a protocol to recover peptides with antidiabetic effects from salmon and cod protein digests and then scale up and optimize the salmon protein hydrolysate production process for industrial-scale production. The peptide mixtures were screened using cell culture assays for insulin-modulating activities and were further fractionated and purified for the final identification. Total yields of salmon and cod protein hydrolysates (<1 kDa) as measured by Kjeldahl nitrogen were 16.9% and 40.1%, respectively. The production process used for the salmon protein hydrolysate (<1 kDa) showed good reproducibility and potential for the industrial-scale production.

Both type 2 diabetes (T2D) and the the metabolic syndrome (MetS) have been shown to increase the risk of cardiovascular disease (CVD). Inflammation and insulin resistance have each been associated with the development of MetS and the onset of T2D as well as the risk of CVD. Inflammation and insulin resistance are therefore suitable targets for public health initiatives and interventions in persons at risk for or living with CVD. Physical inactivity is a major risk factor for CVD as well as MetS and T2D. Conversely, increased physical activity is associated with improved health outcomes for individuals with a high risk for developing CVD. Two possible mechanisms for the deleterious effects of inactivity on health are inflammation and insulin resistance. Researchers have hypothesized that increased adiposity and reduced fitness are partially responsible for the associations between inactivity, inflammation, and insulin resistance. However, these relationships have not been studied extensively in overweight/obese individuals, who are often unfit and sedentary. The purpose of this study was to further examine the relationship between baseline measures of walking activity and sedentary behavior, and inflammation and insulin resistance in a sample of adults with type 2 diabetes and/or metabolic syndrome. This thesis examined baseline data from participants enrolled in either of two studies of patients with T2D (n = 116) or MetS without T2D (n = 126). Participants included low income men and women (not pregnant or nursing) between the ages of 18 and 70 who either show depressed affect (BDI > 11), and were overweight (BMI ≥ 27 kg/m2) and had type 2 diabetes or had at least 3 components of the National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III) classification of the metabolic syndrome (MetS). Structural equation modeling was used to determine if physical inactivity is associated with inflammation or insulin resistance in these conditions. Possible mediational roles of adiposity and low cardiorespiratory fitness were also examined. Additional analyses were conducted to determine if these relationships can be estimated equally in MetS and T2D conditions. Activity was indirectly related to abdominal adiposity via an indirect, positive association with cardiorespiratory fitness. Abdominal adiposity was positively related to both inflammation and insulin resistance. There were no direct associations between activity and inflammation or insulin resistance in this population. Therefore, walking may be negatively related to cardiovascular risk, insofar as it reduces abdominal adiposity.

This thesis examines the economic and time barriers to dietary adherence for T2D patients living in Edmonton by using utility theory, household production theory and the concept of health capital. Socio-demographic, food consumption, food purchase and time use information was obtained by administering a questionnaire and a food record; collecting grocery receipts and a blood sample; conducting a telephone interview, and taking measurements. Multivariate regression analysis and correlations showed a negative association between fruit and vegetable expenditure and A1c. Diet quality was negatively associated with A1c and total food expenditure but had an inverted U-shaped association with income. While working time was negatively correlated with diet quality and positively correlated with A1c, regression analysis showed a negative association between working time and diet quality only among higher income participants. Budget constraints and time constraints appear to be the barriers to dietary adherence among low-income and high-income patients, respectively. / Agricultural and Resource Economics

Due to the increase in type 2 diabetes in the child and adolescent population, examining the lifestyle habits of youth has become important. The purpose of this research was to examine the presence of dietary and physical activity risk factors for type 2 diabetes among youth in Alberta and to evaluate their relationship with insulin sensitivity. Lifestyle habits of Alberta youth with type 2 diabetes (n = 28), and age, sex and BMI matched controls (n = 28) were assessed by a chart review method. Those with diabetes had a higher intake of several nutrients (i.e. protein intake) and were less likely to be physically active. Dietary and physical activity risk factors for diabetes of a large sample of Alberta youth (n = 4981) were also assessed using the Web Survey of Physical Activity and Nutrition (Web-SPAN) and insulin sensitivity was measured in a sub-group (n = 318) using a C-13 glucose breath test. High Glycemic Index (GI) and Glycemic Load (GL) diets were common among Alberta adolescents and dietary patterns associated with dietary GI and GL were assessed. Dietary and physical activity risk factors for type 2 diabetes, including overweight and obesity, high GI, high GL, low fibre, low magnesium, low vegetable and fruit intake, high fat intake and low physical activity levels, were commonly reported among Alberta teens; with some risk factors, such as low fibre intake and high GI being reported by over half of all participants. Youth reported having an average of 3 diabetes risk factors. Boys reported more risk factors than girls, older students reported more risk factors than younger students and students with a higher BMI reported more risk factors than students with a lower BMI. Age, sex, BMI and dietary GI were associated with Insulin Sensitivity Score as measured by a C-13 glucose breath test. In summary, this research has shown that the dietary and physical activity habits of Alberta adolescents are sub-optimal for type 2 diabetes prevention and the relationship between diabetes risk factors and insulin sensitivity in this group suggests that these behaviours are related to early changes in carbohydrate metabolism. / Nutrition and Metabolism

New Zealand is currently in the midst of a diabetes epidemic and it has become clear that the increasing prevalence of obesity and a sedentary lifestyle are inextricably linked to this escalating health crisis. Extensive research has long made clear that people of all ages can enhance their health by incorporating moderate levels of physical activity as part of their normal daily routine and physical activity is now recognised as a major therapeutic modality for type 2 diabetes. Despite such evidence, most people in the western world do not engage in sufficient regular physical activity and there remains a paucity of evidence that elucidates effective methods of achieving the required behaviour change over time. This study set out to demonstrate meaningful correlations between the psychosocial constructs optimism, exercise self-efficacy, goal-directness, stage of change, anxiety and depression, the biochemical measures HbA1c and BMI and also the behavioural outcomes of general physical activity and physical exercise participation, all within a newly diagnosed type 2 diabetic population. Participants (n=30, newly diagnosed adults with type 2 diabetes; mean age 61.46 years; BMI 31.43 Kg/m²[range 18.8-50.95 Kg/m²]) were recruited from attendees of the Christchurch Diabetes Centre's education seminars. The recruitment strategy was designed to search out diabetic patients as near as practicable to the point in time when they first became cognisant of their disease state. A battery of instruments was assembled into a researcher-administered retrospective questionnaire and this was completed with all subjects at baseline and again at six month follow-up. Additional data comprised subject's demographics and selected bio-chemical measures (subject height, weight, and blood Haemoglobin A1c). Descriptive, correlational and qualitative statistics were evaluated. The level of physical activity reported was significantly less than is required to facilitate the biochemical and psychological changes that are generally considered necessary to support optimal health. On average, study participants did not perform their planned physical activity tasks as well as they might have, despite being relatively optimistic and goal-directed at baseline. Many participants clearly indicated an inadequate understanding of exercise modalities and the intensity, duration and frequency of physical activity required to support optimal health. Generally, participants tended to overestimate their physical activity levels. Exercise self-efficacy emerged as an especially important psychological construct, and one that appeared to be among those central to the participants' relationships with physical activity and exercise. The study group demonstrated a relatively high prevalence of low level anxiety and depression, and even at these sub-clinical levels, anxiety and depression were significantly inversely related to optimism, goal-directness, goal-attainment, exercise self-efficacy and stage of change. The study findings illuminate the wide contextual variability among patients who are suffering from the same chronic condition. Further, the implications of conducting detailed pre-assessments of patients' personal characteristics and their psychological profiles, in order to guide intervention tailoring, are also outlined and discussed. Areas for future research are highlighted. In conclusion, meso and macro-level policy implications are discussed, with reference to an array of the broader determinants of health.