In order to elucidate how uncoupling protein 2 (UCP2) influences pancreatic β cells and glucose homeostasis, I have generated and characterized an inducible β cell-specific UCP2 deletion model,MIPCreER×loxUCP2 mice. Male littermates were injected with tamoxifen to induce UCP2 deletion(UCP2 iBKO) or with corn oil (CO). The phenotypes of both short-term (3-4 weeks after the last injection) and long-term (8-9 weeks after the last injection) were determined: Short-term iBKO mice displayed no differences in glucose or insulin tolerance, but enhanced in vivo and in vitro insulin secretion and suppressed islet reactive oxygen species (ROS) levels; while long-term iBKO mice displayed no difference in glucose tolerance, but impaired in vivo and in vitro insulin secretion and enhanced islet ROS levels. In conclusion, short-term UCP2 deletion in β cells promotes insulin secretion, while long-term UCP2 deletion impairs insulin secretion, possibly due to the opposite background of islet ROS.

In order to elucidate how uncoupling protein 2 (UCP2) influences pancreatic β cells and glucose homeostasis, I have generated and characterized an inducible β cell-specific UCP2 deletion model,MIPCreER×loxUCP2 mice. Male littermates were injected with tamoxifen to induce UCP2 deletion(UCP2 iBKO) or with corn oil (CO). The phenotypes of both short-term (3-4 weeks after the last injection) and long-term (8-9 weeks after the last injection) were determined: Short-term iBKO mice displayed no differences in glucose or insulin tolerance, but enhanced in vivo and in vitro insulin secretion and suppressed islet reactive oxygen species (ROS) levels; while long-term iBKO mice displayed no difference in glucose tolerance, but impaired in vivo and in vitro insulin secretion and enhanced islet ROS levels. In conclusion, short-term UCP2 deletion in β cells promotes insulin secretion, while long-term UCP2 deletion impairs insulin secretion, possibly due to the opposite background of islet ROS.

Abstract The purpose of this work was to assess the value of humoral and genetic risk markers in the prediction of type 1 diabetes in siblings of children with type 1 diabetes, to characterise preclinical course of beta-cell autoimmunity in siblings, and to investigate the frequency of autoantibodies and their relations to genetic markers, beta-cell function and progression to type 1 diabetes in a schoolchild population. The prevalence and predictive value of autoantibodies was studied in 755 initially unaffected siblings, and the combination of genetic markers and autoantibodies in 701 of these siblings. Islet cell autoantibodies (ICA), insulin autoantibodies (IAA), glutamic acid decarboxylase antibodies (GADA) and IA-2 antibodies (IA-2A) were all shown to be of value in the prediction of type 1 diabetes in siblings initially tested at or close to the diagnosis of type 1 diabetes in the index case in the family. The risk of progression to type 1 diabetes was related to the number of autoantibodies detected, and the PPV of multiple autoantibodies was 55% over a period of 8 years. Autoantibodies were closely associated with HLA risk markers. A combination of the genetic markers and autoantibodies increased the PPVs of all autoantibodies substantially but also markedly reduced the sensitivity. The preclinical course of type 1 diabetes was investigated in 39 initially unaffected siblings who progressed to clinical disease during the follow-up. These individuals were characterised by the high-risk genetic markers, decreased beta-cell function and humoral autoimmunity against multiple beta-cell targets. However, all measures implied a remarkable individual variation in the rate of the disease process and the pattern of humoral beta-cell autoimmunity. Furthermore, the autoimmune process resulting in clinical presentation of type 1 diabetes could not be unambiguously distinguished from autoimmunity not leading to clinical disease within almost 10 years of follow-up. The frequencies of ICA, IA-2A, GADA and IAA in 3652 healthy Finnish schoolchildren were 2.8%, 0.6%, 0.5% and 0.9%, respectively, and multiple antibodies were detected in 0.6% of these children. GADA and multiple antibodies were related to the DQB1*0302 allele and the DQB1*02/0302 genotype. A reduced first-phase insulin reponse (FPIR) was associated with IA-2A, GADA, IAA and multiple antibodies, but not with ICA or any specific DQB1 allele or genotype. Four subjects progressed to type 1 diabetes, all of them having multiple autoantibodies and those two who underwent an intravenous glucose tolerance test had also a reduced FPIR. None of the progressors carried the high risk DQB1*0302 allele and two of them even carried the protective DQB1*0602 or *0603 allele. In conclusion, autoantibodies alone are recommended as first-line screening in siblings, whereas subsequent determination of HLA-DQB1 markers and their combination with autoantibodies provides a valuable tool for more precise risk assessment. Wide heterogeneity in the course of preclinical type 1 diabetes complicates an accurate estimation of the individual risk of progression to type 1 diabetes among siblings of children with type 1 diabetes. Combined screening for autoantibodies is recommended for the assessment of the risk of progression to type 1 diabetes in schoolchild populations, whereas the present observations challenge the value of current genetic risk markers in predictive strategies targeting schoolchildren.

<p> Fetal exposure to cigarette smoke is associated with an increased risk of adult-onset metabolic abnormalities. In Canada, nicotine replacement therapy (NRT) is recommended as a safe smoking cessation aid for pregnant women. However, our laboratory has demonstrated that fetal and neonatal nicotine exposure results in glucose intolerance in adult rats. The goal of this thesis was to determine the mechanism(s) underlying the observed dysglycemia following fetal and neonatal nicotine exposure, with a specific focus on the effects of nicotine on pancreatic development and postnatal beta cell function.</p> <p> Nulliparous female Wistar rats received daily subcutaneous injections of either saline or nicotine bitartrate (1 mg/kg/d) for 2 weeks prior to mating until weaning (postnatal day 21 - PND21 ). Pancreatic tissue was collected from male offspring at birth (PND1), 3, 7, 15 and 26 weeks of age. For the critical windows study, dams received nicotine or saline during different stages of pancreatic development, including: A) pre-mating only, B) pre-mating + pregnancy only, C) pre-mating, pregnancy and lactation, or D) pre-mating + lactation only. For the intervention study, nicotine-exposed dams received either normal chow or diet containing antioxidants (1000 IU/kg vitamin E, 0.25% w/w coenzyme Q10 and 0.05% w/w α-lipoic acid) during mating, pregnancy and lactation.</p> <p> Results from this thesis demonstrate that exposure to nicotine during both fetal and neonatal development (but neither stage alone) causes a permenant loss of beta cell mass beginning at birth, and adult-onset dysglycemia in rodents. Furthermore, nicotine exposure induces pancreatic oxidative stress and mitochondrial-mediated beta cell apoptosis in neonates, followed by a progressive decline in mitochondrial structure and function. Maternal treatment with a dietary antioxidant cocktail during pregnancy and lactation protected the developing beta cells from nicotine-induced apoptosis and mitochondrial swelling. These data indicate that the safety of NRT use during pregnancy should be re-evaluated.</p> / Thesis / Doctor of Philosophy (PhD)

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.

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.

GH and the insulin like growth factor type I (IGF-I) have synergistic functions on protein synthesis and muscle mass. In adipose tissue, GH stimulates lipolysis and lipid oxidation, while IGF-I stimulates the differentiation of pre adipocytes to adipocytes. In glucose metabolism , GH and IGF-I have antagonist opposite actions, been GH antagonist and IGF-I synergetic to insulin sensitivity (IS). Heterozygous adults individuals for the mutation c.104 = 1G> A in the GH releasing hormone receptor gene (MUT/N), present a mild reduction of GH and normal IGF-I levels accompanied by a significant reduction in lean body mass (Kg), with a tendancy of reduction in fat mass (kg), compared to homozygous normal adults individuals (N/N). IS and the beta cell function are unknown in individuals MUT/ N. To evaluate them, it was performed the oral glucose tolerance test with administration of 75g of glucose and serum glucose and insulin were measured at 0, 30, 60, 90, 120 and 180 minutes in 25 individual MUT/ N (12 M / 13 F, 40.08 ± 10.87 years) and 25 N/N (14 M / F 11; 39.96 ± 12.49 years). There was no difference in height, nevertheless weight, BMI, waist and hip circunferences were lower in individuals MUT/N. IS was assessed by HOMAir, where lower values indicate a greater IS and the QUICKI, OGIS 2 and OGIS 3, where higher values indicate higher SI. The beta cell function was assessed by HOMA-beta, insulinogenic index and area under the curve of insulin / glucose ratio (ASC I/G). ANOVA showed no difference between glucose and insulin responses between the groups. The areas under the curve of glucose and insulin were also similar between the number of patients with pre diabetes and diabetes. No changes were observed in the HOMAir, QUICKI, OGIS 2 and OGIS 3, HOMA beta, insulinogenic index and ASC I/G between the two groups. In conclusion, insulin sensitivity and beta cell function in MUT/N individuals are similar to MUT/N individuals. / GH e o fator de crescimento semelhante à insulina tipo I (IGF-I) apresentam funções sinérgicas sobre a síntese protéica e massa muscular. No tecido adiposo, o GH estimula a lipólise e oxidação lípidica, enquanto o IGF-I estimula a diferenciação dos pré adipócitos em adipócitos. No metabolismo glicídico, GH e IGF-I têm ações opostas, sendo o GH antagônico e o IGF-I sinérgico à sensibilidade insulínica (SI). Indivíduos heterozigóticos adultos para a mutação c.104=1G>A gene do receptor do hormônio liberador do GH (MUT/N) no, apresentam discreta redução do GH e níveis normais de IGF-I acompanhada de redução significativa da massa magra (Kg), com tendência à redução da massa gorda (Kg), em relação aos indivíduos homozigóticos normais (N/N). A SI e a função das células beta são desconhecidas nos indivíduos MUT/N. Para avaliá-las, foi realizado o teste de tolerância oral à glicose com administração de 75g de glicose e dosagens de glicose e insulina nos tempos 0, 30, 60, 90, 120 e 180 minutos em 25 indivíduos MUT/N (12 M/ 13 F; 40,08 ± 10,87 anos) e 25 N/N (14 M/ 11 F; 39,96 ± 12,49 anos). Não houve diferença na altura, contudo o peso, o IMC, a cintura e o quadril foram menores nos indivíduos MUT/N. A sensibilidade à insulina (SI) foi avaliada pelo HOMAir, onde menores valores, indicam maior SI e pelos QUICKI, OGIS 2 e OGIS 3, onde maiores valores, indicam maior SI. A função da célula beta foi avaliada pelo HOMA-beta, índice insulinogênico e área sob a curva da razão insulina/ glicose (ASC I/G). ANOVA indicou que não houve diferença entre as respostas glicêmica e insulinêmica entre os grupos. As áreas sob a curva de glicose e insulina foram semelhantes como também entre o número de pacientes com pré diabetes e diabetes. Não foram verificadas variações no HOMAir, QUICK, OGIS 2 e OGIS 3, HOMA beta, índice insulinogênico e ASC I/G entre os dois grupos. Em conclusão, a sensibilidade insulínica e a função de célula beta nos indivíduos MUT/N são semelhantes a dos indivíduos N/N.

No description available.

Type 2 diabetes is characterized by peripheral insulin resistance and insufficient insulin release from pancreatic islet β cells. However, the role and sequence of β cell dysfunction and mass loss for reduced insulin levels in type 2 diabetes pathogenesis are unclear. Here, we exploit freshly explanted pancreas specimens from metabolically phenotyped surgical patients using an in situ tissue slice technology. This approach allows assessment of β cell volume and function within pancreas samples of metabolically stratified individuals. We show that, in tissue of pre-diabetic, impaired glucose-tolerant subjects, β cell volume is unchanged, but function significantly deteriorates, exhibiting increased basal release and loss of first-phase insulin secretion. In individuals with type 2 diabetes, function within the sustained β cell volume further declines. These results indicate that dysfunction of persisting β cells is a key factor in the early development and progression of type 2 diabetes, representing a major target for diabetes prevention and therapy.

Background: Chronic pancreatitis (CP) often leads to recurrent pain as well as exocrine and/or endocrine pancreatic insufficiency. This study aimed to investigate the effect of pancreatic head resections on glucose metabolism in patients with CP. Methods: Patients who underwent pylorus-preserving pancreaticoduodenectomy (PPPD), Whipple procedure (cPD), or duodenum-preserving pancreatic head resection (DPPHR) for CP between January 2011 and December 2020 were retrospectively analyzed with regard to markers of pancreatic endocrine function including steady-state beta cell function (%B), insulin resistance (IR), and insulin sensitivity (%S) according to the updated Homeostasis Model Assessment (HOMA2). Results: Out of 141 pancreatic resections for CP, 43 cases including 31 PPPD, 2 cPD and 10 DPPHR, met the inclusion criteria. Preoperatively, six patients (14%) were normoglycemic (NG), 10 patients (23.2%) had impaired glucose tolerance (IGT) and 27 patients (62.8%) had diabetes mellitus (DM). In each subgroup, no significant changes were observed for HOMA2-%B (NG: p = 0.57; IGT: p = 0.38; DM: p = 0.1), HOMA2-IR (NG: p = 0.41; IGT: p = 0.61; DM: p = 0.18) or HOMA2-%S (NG: p = 0.44; IGT: p = 0.52; DM: p = 0.51) 3 and 12 months after surgery, respectively. Conclusion: Pancreatic head resections for CP, including DPPHR and pancreatoduodenectomies, do not significantly affect glucose metabolism within a follow-up period of 12 months.