To accurately predict the outcome of a late phase study, pharmacometric models can help in drug development. Making informed decision on which models to use will also facilitate drug development. This can depend on the mechanism of action for the drug as well as stability and runtime factors. This is an investigation of four published semi-mechanistic pharmacometric models to predict glycosylated red blood cells (HbA1c) in a late phase study of an anti-diabetic drug together with an assessment of their stability and power to detect drug effects. Mean plasma glucose (MPG), fasting plasma glucose (FPG) or FPG and fasting serum insulin (FSI) are used together with HbA1c as drivers for change in the models. We find that less complex models, with fewer differential equations, are quicker to run and more stable, and that MPG alone is superior to FPG or FPG and FSI to detect a drug effect. The findings are useful for drug development in the anti-diabetic area, and show that a less mechanistic model performs well under these conditions.

Emerging evidence suggests that vitamin D may be associated with type 2 diabetes (T2DM), however current data are inconsistent regarding metabolic disorders underlying T2DM. The objectives of this thesis were to investigate the association of vitamin D with the primary pathophysiological disorders of type 2 diabetes: namely insulin resistance (IR) and beta (β)-cell dysfunction, and the metabolic syndrome (MetS). All studies included individuals participating in the PROspective Metabolism and ISlet cell Evaluation (PROMISE) cohort study, comprising 712 subjects 30 years and older, and at risk of T2DM at baseline. Serum 25-hydroxyvitamin D [25(OH)D] was measured to assess vitamin D nutritional status. Validated oral glucose tolerance test derived indices for IR and β-cell function were calculated. In the first cross-sectional study, multivariate linear regression analyses indicated a significant inverse association of serum 25(OH)D with IR (β=-0.003, p=0.007) and a significant positive association of 25(OH)D with β-cell function (β=0.004, p=0.03) at the baseline PROMISE clinic visit (n=712). In another cross-sectional study also conducted using data from the baseline PROMISE clinic visit, higher 25(OH)D was found to be significantly associated with a reduced presence of the MetS after multivariate adjustment (OR=0.76, 95% CI 0.62-0.93). Low serum 25(OH)D was also significantly associated with various MetS components. In light of the findings in the first cross-sectional study, the third study examined prospective associations of baseline 25(OH)D with 3-year follow-up IR and β-cell function (n=489). Although baseline 25(OH)D was not significantly associated with follow-up IR, a significant positive association of baseline 25(OH)D with β-cell function at follow-up was observed (β=0.005, p=0.015). Lastly, in a longitudinal substudy (n=127), seasonal changes in 25(OH)D over 2.5 years did not significantly affect changes in IR and β-cell function. In conclusion, results indicated that baseline serum 25(OH)D was cross-sectionally related to IR, β-cell function and the MetS, and was prospectively related to β-cell function at the 3-year follow-up. In addition, seasonal changes in 25(OH)D do not adversely affect IR and β-cell function over time. These findings suggest a potential role for higher 25(OH)D levels in reducing diabetes risk, although additional longitudinal studies are warranted.

Coffee consumption has consistently been associated with a reduction in risk of type 2 diabetes mellitus (T2DM), although the mechanism for this association remains unknown. Sub-clinical inflammation, non-alcoholic fatty liver disease (NAFLD), and lipoprotein abnormalities characterize and predict T2DM. Limited evidence suggests that coffee may have a beneficial role in these disorders but further investigation is warranted. Our aim therefore was to investigate the associations of caffeinated and decaffeinated coffee with markers of inflammation, liver injury, and lipoproteins, in a non-diabetic cohort. No significant associations of caffeinated or decaffeinated coffee with inflammatory markers or lipoproteins were identified. Caffeinated coffee consumption however was inversely associated with alanine aminotransferase (β= -0.09, p= 0.0107) and aspartate aminotransferase (β= -0.05, p= 0.0161) in multivariate analysis. Decaffeinated coffee was not associated with liver enzymes. These analyses suggest that caffeinated coffee’s beneficial impact on NAFLD may be a potential mechanism for its inverse association with T2DM.

Obesity is an adverse factor in the development and severity of breast cancer. Obesity is often accompanied by an increase in circulating insulin, which is also associated with poor BC prognosis. Although not expressed in normal breast tissue, the insulin receptor (IR) is highly expressed in BC, therefore insulin signaling in BC cells may be responsible for the negative prognostic effects associated with hyperinsulinemia. This thesis describes the development of a cell-based system to study how insulin affects BC. My work shows that MCF10A, untransformed human breast epithelial cells that express the IR, require insulin for normal proliferation and morphology. Interestingly, I discovered hyperactivation of ERK1/2 in MCF10A cells in response to insulin withdrawal, resulting in a loss of epithelial phenotype. Unexpectedly, while losing epithelial phenotype, MCF10A cells depleted of insulin failed to migrate. In conclusion, breast cells that express IR require insulin for migration and maintenance of epithelial characteristics.

Emerging evidence suggests that vitamin D may be associated with type 2 diabetes (T2DM), however current data are inconsistent regarding metabolic disorders underlying T2DM. The objectives of this thesis were to investigate the association of vitamin D with the primary pathophysiological disorders of type 2 diabetes: namely insulin resistance (IR) and beta (β)-cell dysfunction, and the metabolic syndrome (MetS). All studies included individuals participating in the PROspective Metabolism and ISlet cell Evaluation (PROMISE) cohort study, comprising 712 subjects 30 years and older, and at risk of T2DM at baseline. Serum 25-hydroxyvitamin D [25(OH)D] was measured to assess vitamin D nutritional status. Validated oral glucose tolerance test derived indices for IR and β-cell function were calculated. In the first cross-sectional study, multivariate linear regression analyses indicated a significant inverse association of serum 25(OH)D with IR (β=-0.003, p=0.007) and a significant positive association of 25(OH)D with β-cell function (β=0.004, p=0.03) at the baseline PROMISE clinic visit (n=712). In another cross-sectional study also conducted using data from the baseline PROMISE clinic visit, higher 25(OH)D was found to be significantly associated with a reduced presence of the MetS after multivariate adjustment (OR=0.76, 95% CI 0.62-0.93). Low serum 25(OH)D was also significantly associated with various MetS components. In light of the findings in the first cross-sectional study, the third study examined prospective associations of baseline 25(OH)D with 3-year follow-up IR and β-cell function (n=489). Although baseline 25(OH)D was not significantly associated with follow-up IR, a significant positive association of baseline 25(OH)D with β-cell function at follow-up was observed (β=0.005, p=0.015). Lastly, in a longitudinal substudy (n=127), seasonal changes in 25(OH)D over 2.5 years did not significantly affect changes in IR and β-cell function. In conclusion, results indicated that baseline serum 25(OH)D was cross-sectionally related to IR, β-cell function and the MetS, and was prospectively related to β-cell function at the 3-year follow-up. In addition, seasonal changes in 25(OH)D do not adversely affect IR and β-cell function over time. These findings suggest a potential role for higher 25(OH)D levels in reducing diabetes risk, although additional longitudinal studies are warranted.

Coffee consumption has consistently been associated with a reduction in risk of type 2 diabetes mellitus (T2DM), although the mechanism for this association remains unknown. Sub-clinical inflammation, non-alcoholic fatty liver disease (NAFLD), and lipoprotein abnormalities characterize and predict T2DM. Limited evidence suggests that coffee may have a beneficial role in these disorders but further investigation is warranted. Our aim therefore was to investigate the associations of caffeinated and decaffeinated coffee with markers of inflammation, liver injury, and lipoproteins, in a non-diabetic cohort. No significant associations of caffeinated or decaffeinated coffee with inflammatory markers or lipoproteins were identified. Caffeinated coffee consumption however was inversely associated with alanine aminotransferase (β= -0.09, p= 0.0107) and aspartate aminotransferase (β= -0.05, p= 0.0161) in multivariate analysis. Decaffeinated coffee was not associated with liver enzymes. These analyses suggest that caffeinated coffee’s beneficial impact on NAFLD may be a potential mechanism for its inverse association with T2DM.

Obesity is an adverse factor in the development and severity of breast cancer. Obesity is often accompanied by an increase in circulating insulin, which is also associated with poor BC prognosis. Although not expressed in normal breast tissue, the insulin receptor (IR) is highly expressed in BC, therefore insulin signaling in BC cells may be responsible for the negative prognostic effects associated with hyperinsulinemia. This thesis describes the development of a cell-based system to study how insulin affects BC. My work shows that MCF10A, untransformed human breast epithelial cells that express the IR, require insulin for normal proliferation and morphology. Interestingly, I discovered hyperactivation of ERK1/2 in MCF10A cells in response to insulin withdrawal, resulting in a loss of epithelial phenotype. Unexpectedly, while losing epithelial phenotype, MCF10A cells depleted of insulin failed to migrate. In conclusion, breast cells that express IR require insulin for migration and maintenance of epithelial characteristics.

Type 2 diabetes (T2DM) is a growing concern worldwide, particularly among Aboriginal Canadians. Diet has been associated with diabetes risk, and dietary pattern analysis (DPA) provides a method in which whole dietary patterns may be explored in relation to disease. Factor analysis (FA) and reduced rank regression (RRR) of data from the Sandy Lake Health and Diabetes Project identified patterns associated with incident T2DM at follow-up. A RRR-derived pattern characterized by tea, hot cereal, and peas, and low intake of high-sugar foods and beef was positively associated with diabetes; however, the relationship was attenuated with adjustment for age and other covariates. A FA-derived pattern characterized by processed foods was positively associated with incident T2DM in a multivariate model (OR=1.38; CIs: 1.02, 1.86 per unit), suggesting intake of processed foods may predict T2DM risk.

Type 2 diabetes mellitus (T2DM) is now increasingly diagnosed in children and adolescents at an alarming rate, especially in youth from diverse ethnic backgrounds. Youth diagnosed with T2DM and their families face many challenges associated with the illness and its complications. Given that the prevalence of T2DM in youth is a recent trend, most of the studies examining T2DM have been conducted with adults. The current study expands the literature base of youth with T2DM by collecting demographic and clinical data of youth with T2DM and their families. Regression analyses were used to investigate the relationship among youth's executive function, their body mass index (BMI) and glycosylated hemoglobin (HbA1c) level. Furthermore, the study analyzed the relationship among depressive symptoms and health related quality of life (HRQOL) in youth, and the role of family members in sharing of tasks related to T2DM care and the youth's HRQOL. Results of this study demonstrated that executive function does not predict a youth's HbA1c, nor their BMI. Interestingly, one of the more significant findings to emerge from this study is that youth's rating of their ability to adjust to changes in routine or task demands and their ability to modulate emotions significantly correlated with their BMI. Results also demonstrated that HbA1c does not mediate the relationship between depressive symptoms and HRQOL, nor the relationship between the family sharing of responsibilities related to T2DM tasks and HRQOL. Future research examining the relationship among psychological and family characteristics can aid the development of diabetes prevention and treatment management.

Objective The prevalence of obesity and related diseases such as type 2 diabetes mellitus (T2DM) is increasing worldwide, and the Asian Indian population seems to be particularly susceptible to developing T2DM, even at a low body mass index (BMI). In Sweden, the age-adjusted prevalence of diabetes has not increased despite increasing self-reported obesity. However, modern data on the prevalence of obesity and T2DM in Scandinavia are absent.The biochemical links between obesity and subsequent T2DM are unknown, but the adipocyte-derived hormones leptin and adiponectin (adipokines) have been suggested as potential links because they both are related to insulin and glucose physiology. Some studies have found leptin to be an independent predictor of T2DM in men but not in women, although these results are inconsistent. In contrast, adiponectin has more consistently been linked to development of T2DM in both men and women. Furthermore, the leptin–adiponectin ratio may predict incident T2DM better than either of the two hormones separately.The aims of this thesis were to describe time trends in obesity and T2DM in northern Sweden, to evaluate leptin and adiponectin as predictors of deterioration in glucose metabolism including T2DM, and to evaluate leptin as a risk marker regarding ethnic differences, circ-annual variation, and intra-individual stability. Materials and methods Three large population surveys were used, the Northern Sweden MONICA (MONitoring of Trends and Determinants in CArdiovascular Disease) study, the Västerbotten Intervention Programme (VIP), and the Mauritius Non-Communicable Disease Study. Within the MONICA study, six cross-sectional surveys were performed in Sweden’s two northernmost counties, Norrbotten and Västerbotten, between 1986 and 2009. A total of 1000 men and 1000 women ages 25–64 years, also including from 1994 250 men and 250 women ages 65–74 years, were independently chosen for each survey. The overall participation rate was 75%. In 1999, a reinvestigation was performed in 74% of all participants from the three first surveys. Data from the MONICA surveys were used in papers I and IV and data from the reinvestigation survey in paper II. VIP is an ongoing population intervention program that started in the mid-eighties targeting cardiovascular risk factors and has covered the whole county of Västerbotten since 1991. Inhabitants are invited the years they turn 40, 50, and 60 years old, and the annual participation rate has varied between 48% and 67%. A subset (n=1780) from VIP was used in paper II for the circ-annual leptin analysis, and VIP data linked to the diabetes register in Västerbotten (DiabNorr) were used in a case referent study (640 patients with T2DM) in paper III. The Mauritius Non-Communicable Disease Study was performed in 1987 in 10 randomly selected (with probability proportional to size) population clusters. All eligible adults ages 25–74 years were invited, and the participation rate was 86% (n=5083). In 1992, a follow-up survey was performed in 49% of the initial participants. The Mauritius survey data were used in paper II. Results I. BMI increased in men ages 25–74 years and in women ages 25–44 years in northern Sweden between 1986 and 2004. The prevalence of obesity (BMI 30) increased in men ages 25–44 and 55–74 years and in women ages 25–44 years. The prevalence of obesity increased from 10.4% to 19.1% in men and from 12.9% to 17.9% in women ages 25–64 years. Waist circumference (WC) decreased in women of all ages and in men ages 55–64 years between 1986 and 1990. After 1990, WC increased again, and the prevalence of abdominal obesity rose markedly in women ages 25–64 years. II. Differences in circulating levels of leptin, leptin per BMI unit (leptin/BMI), and leptin per cm in WC (leptin/waist) were tested in men and women of Asian Indian, Creole (African), and Caucasian ethnicity. Asian Indian men and women had the highest leptin concentrations and Caucasian men and women the lowest while Creole men and women had intermediate values for leptin, leptin/BMI, and leptin/waist. No circ-annual variation in leptin concentrations was seen in Caucasians. The intra-individual test– retest stability for leptin was equal in men and women of different ethnicities, over 5–13 years, with an intra-class correlation of 0.65–0.82. III. High adiponectin concentrations predicted decreased risk of T2DM in both insulin-sensitive and insulin-resistant men and women, whereas high leptin levels predicted increased risk for T2DM only in insulinsensitive men. A high leptin–adiponectin ratio predicted T2DM in both men and women, and men with a high ratio had a shorter time to diagnosis than those with a low ratio. IV. In northern Sweden, fasting and post-load glucose increased in women ages 24–65 years with 0.2 mmol/l and 0.7 mmol/l, respectively, between 1990 and 2009. Consequently, the prevalence of impaired fasting glucose and impaired glucose tolerance (IGT) rose from 4.5% to 7.7%, and from 7.8% to 14.5%, respectively. In men, post-load glucose increased at 0.5 mmol/l, and the prevalence of IGT rose from 3.5% to 10.1%. The prevalence of diabetes did not increase. An independent relationship between leptin and changes in fasting and post-load glucose was seen in men but not in women. Conclusion An increasing obesity and concomitant deterioration in glucose metabolism was seen in northern Sweden in the period studied. High adiponectin concentrations predicted a decreased risk of T2DM in both men and women, whereas high leptin concentrations predicted an increase in fasting and post-load glucose as well as an increased risk of T2DM in men but not in women. Individual insulin resistance status modified the association between leptin and T2DM, and the leptin–adiponectin ratio may add further predictive information beyond the measures of the separate hormones. In relation to traditional anthropometric measures of obesity, Asian Indian men and women had the highest and Caucasians the lowest concentrations of leptin while Creole (African) men and women had intermediate levels. As a risk marker, leptin has a high intra-individual stability, equal in men and women and among different ethnicities over 5–13 years with no circ-annual variation.