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[Aims/hypothesis]: Second-generation antipsychotic (SGA) drugs have been associated with the development of type 2 diabetes and the metabolic syndrome in patients with schizophrenia. In this study, we aimed to investigate the effects of two different SGA drugs, olanzapine and aripiprazole, on metabolic state and islet function and plasticity. [Methods]: We analysed the functional adaptation of beta cells in 12-week-old B6;129 female mice fed an olanzapine- or aripiprazole-supplemented diet (5.5–6.0 mg kg−1 day−1) for 6 months. Glucose and insulin tolerance tests, in vivo glucose-stimulated insulin secretion and indirect calorimetry were performed at the end of the study. The effects of SGAs on beta cell plasticity and islet serotonin levels were assessed by transcriptomic analysis and immunofluorescence. Insulin secretion was assessed by static incubations and Ca2+ fluxes by imaging techniques. [Results]: Treatment of female mice with olanzapine or aripiprazole for 6 months induced weight gain (p<0.01 and p<0.05, respectively), glucose intolerance (p<0.01) and impaired insulin secretion (p<0.05) vs mice fed a control chow diet. Aripiprazole, but not olanzapine, induced serotonin production in beta cells vs controls, likely by increasing tryptophan hydroxylase 1 (TPH1) expression, and inhibited Ca2+ flux. Of note, aripiprazole increased beta cell size (p<0.05) and mass (p<0.01) vs mice fed a control chow diet, along with activation of mechanistic target of rapamycin complex 1 (mTORC1)/S6 signalling, without preventing beta cell dysfunction. [Conclusions/interpretation]: Both SGAs induced weight gain and beta cell dysfunction, leading to glucose intolerance; however, aripiprazole had a more potent effect in terms of metabolic alterations, which was likely a result of its ability to modulate the serotonergic system. The deleterious metabolic effects of SGAs on islet function should be considered while treating patients as these drugs may increase the risk for developme

The understanding of metabolic disease and diabetes on a molecular level has increased significantly due to the recent advances in molecular biology and biotechnology. However, in vitro studies and animal models do not always translate to the human disease, perhaps illustrated by the failure of many drug candidates in the clinical phase. Non-invasive biomedical imaging techniques such as Positron Emission Tomography (PET) offer tools for direct visualization and quantification of molecular processes in humans. Developments in this area potentially enable longitudinal in vivo studies of receptors and processes involved in diabetes guiding drug development and diagnosis in the near future. This mini-review focuses on describing the overall perspective of how PET can be used to increase our understanding and improve treatment of diabetes. The methodological aspects and future developments and challenges are highlighted.

[11C]5-Hydroxy-tryptophan ([11C]5-HTP) is a Positron Emission Tomography marker for serotonergic biosynthesis and degradation, with use in imaging of neuroendocrine tumors and recently also the endocrine pancreas in diabetes. In order to further develop [11C]5-HTP as a quantitative in vivo tool for understanding the mechanisms of serotonin signaling in human pancreas, we aimed to develop a kinetic modeling approach sensitive for changes in serotonin biosynthesis, retention and degradation. Cynomolgus monkeys were examined by [11C]5-HTP PET/CT, either at baseline (n=9) or following intravenous pretreatment with 3 mg/kg carbidopa (Dopa Decarboxylase inhibitor, n=3) or 2 mg/kg clorgyline (Monoamine Oxidase-A inhibitor, n=5). The dynamic tissue uptake was analysed by a 2-tissue compartment model including an efflux mechanism from the second tissue compartment (2TC kloss), which theoretically reproduces the known processing of 5-HTP in neuroendocrine cells. The 2TC kloss model could accurately describe all three modes of tissue kinetics depending on the pretreatment regiment. Rate constant k3 (corresponding to DDC activity) and the macro-parameter Flux (Ki) was decreased (P<0.05) by carbidopa pretreatment, while k2 (corresponding to cellular washout of intact [11C]5-HTP) was increased (P<0.05). The efflux parameter kloss (corresponding to MAO-A activity) was decreased (P<0.05) by pretreatment of clorgyline, while the macro-parameter Flux/Efflux ratio (Ki/kloss) was increased (P<0.0001). We present a compartment model analysis method that can quantitatively assess in vivo pharmacological interactions with several of the key enzymatic steps of the serotonergic biosynthesis in pancreas.

Aims/hypothesisIslet amyloid polypeptide (IAPP) misfolding and toxic oligomers contribute to beta cell loss and stress in type 2 diabetes. Pregnancy-related diabetes predicts subsequent risk for type 2 diabetes but little is known about the impact of pregnancy on beta cell mass, turnover and stress. Availability of human pancreas tissue in pregnancy is limited and most widely used mouse models of type 2 diabetes do not develop pregnancy-related diabetes, possibly because rodent IAPP is not prone to form toxic oligomers. We hypothesised that mice transgenic for human IAPP (hIAPP) are prone to pregnancy-related diabetes with beta cell responses reflective of those in type 2 diabetes.MethodsWe evaluated the impact of a first and second pregnancy on glucose homeostasis, beta cell mass and turnover and markers of beta cell stress in hIAPP transgenic (hTG) mice.ResultsPregnancy induced both endoplasmic reticulum stress and oxidative stress and compromised autophagy in beta cells in hTG mice, which are characteristic of beta cells in type 2 diabetes. Beta cell stress persisted after pregnancy, resulting in subsequent diabetes before or during a second pregnancy.Conclusions/interpretationHigh expression of hIAPP in response to pregnancy recapitulates mechanisms contributing to beta cell stress in type 2 diabetes. We hypothesise that, in individuals prone to type 2 diabetes, pregnancy-induced increased expression of IAPP inflicts beta cell damage that persists and is compounded by subsequent additive stress such as further pregnancy. The hTG mouse model is a novel model for pregnancy-related diabetes.

Aims/hypothesis: Genetic studies show coupling of genes affecting beta cell function to type 1 diabetes, but hitherto no studies on whether beta cell dysfunction could precede insulitis and clinical onset of type 1 diabetes are available. Methods: We used 40-day-old BioBreeding (BB) DRLyp/Lyp rats (a model of spontaneous autoimmune type 1 diabetes) and diabetes-resistant DRLyp/+ and DR+/+ littermates (controls) to investigate beta cell function in vivo, and insulin and glucagon secretion in vitro. Beta cell mass was assessed by optical projection tomography (OPT) and morphometry. Additionally, measurements of intra-islet blood flow were performed using microsphere injections. We also assessed immune cell infiltration, cytokine expression in islets (by immunohistochemistry and qPCR), as well as islet Glut2 expression and ATP/ADP ratio to determine effects on glucose uptake and metabolism in beta cells. Results: DRLyp/Lyp rats were normoglycaemic and without traces of immune cell infiltrates. However, IVGTTs revealed a significant decrease in the acute insulin response to glucose compared with control rats (1685.3 +/- 121.3 vs 633.3 +/- 148.7; p < 0.0001). In agreement, insulin secretion was severely perturbed in isolated islets, and both first- and second-phase insulin release were lowered compared with control rats, while glucagon secretion was similar in both groups. Interestingly, after 5-7 days of culture of islets from DRLyp/Lyp rats in normal media, glucose-stimulated insulin secretion (GSIS) was improved; although, a significant decrease in GSIS was still evident compared with islets from control rats at this time (7393.9 +/- 1593.7 vs 4416.8 +/- 1230.5 pg islet-1 h-1; p < 0.0001). Compared with controls, OPT of whole pancreas from DRLyp/Lyp rats revealed significant reductions in medium (4.1 x 109 +/- 9.5 x 107 vs 3.8 x 109 +/- 5.8 x 107 μm3; p = 0.044) and small sized islets (1.6 x 109 +/- 5.1 x 107 vs 1.4 x 109 +/- 4.5 x 107 μm3; p = 0.035). Finally

BACKGROUND: The G-protein-coupled receptor 44 (GPR44) is a beta cell-restricted target that may serve as a marker for beta cell mass (BCM) given the development of a suitable PET ligand. METHODS: The binding characteristics of the selected candidate, AZ12204657, at human GPR44 were determined using in vitro ligand binding assays. AZ12204657 was radiolabeled using 11C- or 3H-labeled methyl iodide ([11C/3H]CH3I) in one step, and the conversion of [11C/3H]CH3I to the radiolabeled product [11C/3H]AZ12204657 was quantitative. The specificity of radioligand binding to GPR44 and the selectivity for beta cells were evaluated by in vitro binding studies on pancreatic sections from human and non-human primates as well as on homogenates from endocrine and exocrine pancreatic compartments. RESULTS: The radiochemical purity of the resulting radioligand [11C]AZ12204657 was > 98%, with high molar activity (MA), 1351 ± 575 GBq/μmol (n = 18). The radiochemical purity of [3H]AZ12204657 was > 99% with MA of 2 GBq/μmol. Pancreatic binding of [11C/3H]AZ12204657 was co-localized with insulin-positive islets of Langerhans in non-diabetic individuals and individuals with type 2 diabetes (T2D). The binding of [11C]AZ12204657 to GPR44 was > 10 times higher in islet homogenates compared to exocrine homogenates. In human islets of Langerhans GPR44 was co-expressed with insulin, but not glucagon as assessed by co-staining and confocal microscopy. CONCLUSION: We radiolabeled [11C]AZ12204657, a potential PET radioligand for the beta cell-restricted protein GPR44. In vitro evaluation demonstrated that [3H]AZ12204657 and [11C]AZ12204657 selectively target pancreatic beta cells. [11C]AZ12204657 has promising properties as a marker for human BCM.

Aims/hypothesis Genetic studies show coupling of genes affecting beta cell function to type 1 diabetes, but hitherto no studies on whether beta cell dysfunction could precede insulitis and clinical onset of type 1 diabetes are available. Methods We used 40-day-old BioBreeding (BB) DRLyp/Lyp rats (a model of spontaneous autoimmune type 1 diabetes) and diabetes-resistant DRLyp/+ and DR+/+ littermates (controls) to investigate beta cell function in vivo, and insulin and glucagon secretion in vitro. Beta cell mass was assessed by optical projection tomography (OPT) and morphometry. Additionally, measurements of intra-islet blood flow were performed using microsphere injections. We also assessed immune cell infiltration, cytokine expression in islets (by immunohistochemistry and qPCR), as well as islet Glut2 expression and ATP/ADP ratio to determine effects on glucose uptake and metabolism in beta cells. Results DRLyp/Lyp rats were normoglycaemic and without traces of immune cell infiltrates. However, IVGTTs revealed a significant decrease in the acute insulin response to glucose compared with control rats (1685.3 +/- 121.3 vs 633.3 +/- 148.7; p < 0.0001). In agreement, insulin secretion was severely perturbed in isolated islets, and both first- and second-phase insulin release were lowered compared with control rats, while glucagon secretion was similar in both groups. Interestingly, after 5-7 days of culture of islets from DRLyp/Lyp rats in normal media, glucose-stimulated insulin secretion (GSIS) was improved; although, a significant decrease in GSIS was still evident compared with islets from control rats at this time (7393.9 +/- 1593.7 vs 4416.8 +/- 1230.5 pg islet(-1) h(-1); p < 0.0001). Compared with controls, OPT of whole pancreas from DRLyp/Lyp rats revealed significant reductions in medium (4.1 x 10(9) +/- 9.5 x 10(7) vs 3.8 x 10(9) +/- 5.8 x 10(7) mu m(3); p = 0.044) and small sized islets (1.6 x 10(9) +/- 5.1 x 10(7) vs 1.4 x 10(9) +/- 4.5 x 10(7) mu m(

Aims/hypothesis: Genetic studies show coupling of genes affecting beta cell function to type 1 diabetes, but hitherto no studies on whether beta cell dysfunction could precede insulitis and clinical onset of type 1 diabetes are available. Methods: We used 40-day-old BioBreeding (BB) DRLyp/Lyp rats (a model of spontaneous autoimmune type 1 diabetes) and diabetes-resistant DRLyp/+ and DR+/+ littermates (controls) to investigate beta cell function in vivo, and insulin and glucagon secretion in vitro. Beta cell mass was assessed by optical projection tomography (OPT) and morphometry. Additionally, measurements of intra-islet blood flow were performed using microsphere injections. We also assessed immune cell infiltration, cytokine expression in islets (by immunohistochemistry and qPCR), as well as islet Glut2 expression and ATP/ADP ratio to determine effects on glucose uptake and metabolism in beta cells. Results: DRLyp/Lyp rats were normoglycaemic and without traces of immune cell infiltrates. However, IVGTTs revealed a significant decrease in the acute insulin response to glucose compared with control rats (1685.3 +/- 121.3 vs 633.3 +/- 148.7; p < 0.0001). In agreement, insulin secretion was severely perturbed in isolated islets, and both first- and second-phase insulin release were lowered compared with control rats, while glucagon secretion was similar in both groups. Interestingly, after 5-7 days of culture of islets from DRLyp/Lyp rats in normal media, glucose-stimulated insulin secretion (GSIS) was improved; although, a significant decrease in GSIS was still evident compared with islets from control rats at this time (7393.9 +/- 1593.7 vs 4416.8 +/- 1230.5 pg islet-1 h-1; p < 0.0001). Compared with controls, OPT of whole pancreas from DRLyp/Lyp rats revealed significant reductions in medium (4.1 x 109 +/- 9.5 x 107 vs 3.8 x 109 +/- 5.8 x 107 μm3; p = 0.044) and small sized islets (1.6 x 109 +/- 5.1 x 107 vs 1.4 x 109 +/- 4.5 x 107 μm3; p = 0.035). Finally

BACKGROUND: The G-protein-coupled receptor 44 (GPR44) is a beta cell-restricted target that may serve as a marker for beta cell mass (BCM) given the development of a suitable PET ligand. METHODS: The binding characteristics of the selected candidate, AZ12204657, at human GPR44 were determined using in vitro ligand binding assays. AZ12204657 was radiolabeled using 11C- or 3H-labeled methyl iodide ([11C/3H]CH3I) in one step, and the conversion of [11C/3H]CH3I to the radiolabeled product [11C/3H]AZ12204657 was quantitative. The specificity of radioligand binding to GPR44 and the selectivity for beta cells were evaluated by in vitro binding studies on pancreatic sections from human and non-human primates as well as on homogenates from endocrine and exocrine pancreatic compartments. RESULTS: The radiochemical purity of the resulting radioligand [11C]AZ12204657 was > 98%, with high molar activity (MA), 1351 ± 575 GBq/μmol (n = 18). The radiochemical purity of [3H]AZ12204657 was > 99% with MA of 2 GBq/μmol. Pancreatic binding of [11C/3H]AZ12204657 was co-localized with insulin-positive islets of Langerhans in non-diabetic individuals and individuals with type 2 diabetes (T2D). The binding of [11C]AZ12204657 to GPR44 was > 10 times higher in islet homogenates compared to exocrine homogenates. In human islets of Langerhans GPR44 was co-expressed with insulin, but not glucagon as assessed by co-staining and confocal microscopy. CONCLUSION: We radiolabeled [11C]AZ12204657, a potential PET radioligand for the beta cell-restricted protein GPR44. In vitro evaluation demonstrated that [3H]AZ12204657 and [11C]AZ12204657 selectively target pancreatic beta cells. [11C]AZ12204657 has promising properties as a marker for human BCM.

BACKGROUND: The G-protein-coupled receptor 44 (GPR44) is a beta cell-restricted target that may serve as a marker for beta cell mass (BCM) given the development of a suitable PET ligand. METHODS: The binding characteristics of the selected candidate, AZ12204657, at human GPR44 were determined using in vitro ligand binding assays. AZ12204657 was radiolabeled using 11C- or 3H-labeled methyl iodide ([11C/3H]CH3I) in one step, and the conversion of [11C/3H]CH3I to the radiolabeled product [11C/3H]AZ12204657 was quantitative. The specificity of radioligand binding to GPR44 and the selectivity for beta cells were evaluated by in vitro binding studies on pancreatic sections from human and non-human primates as well as on homogenates from endocrine and exocrine pancreatic compartments. RESULTS: The radiochemical purity of the resulting radioligand [11C]AZ12204657 was > 98%, with high molar activity (MA), 1351 ± 575 GBq/μmol (n = 18). The radiochemical purity of [3H]AZ12204657 was > 99% with MA of 2 GBq/μmol. Pancreatic binding of [11C/3H]AZ12204657 was co-localized with insulin-positive islets of Langerhans in non-diabetic individuals and individuals with type 2 diabetes (T2D). The binding of [11C]AZ12204657 to GPR44 was > 10 times higher in islet homogenates compared to exocrine homogenates. In human islets of Langerhans GPR44 was co-expressed with insulin, but not glucagon as assessed by co-staining and confocal microscopy. CONCLUSION: We radiolabeled [11C]AZ12204657, a potential PET radioligand for the beta cell-restricted protein GPR44. In vitro evaluation demonstrated that [3H]AZ12204657 and [11C]AZ12204657 selectively target pancreatic beta cells. [11C]AZ12204657 has promising properties as a marker for human BCM.

Aims/hypothesis: Genetic studies show coupling of genes affecting beta cell function to type 1 diabetes, but hitherto no studies on whether beta cell dysfunction could precede insulitis and clinical onset of type 1 diabetes are available. Methods: We used 40-day-old BioBreeding (BB) DRLyp/Lyp rats (a model of spontaneous autoimmune type 1 diabetes) and diabetes-resistant DRLyp/+ and DR+/+ littermates (controls) to investigate beta cell function in vivo, and insulin and glucagon secretion in vitro. Beta cell mass was assessed by optical projection tomography (OPT) and morphometry. Additionally, measurements of intra-islet blood flow were performed using microsphere injections. We also assessed immune cell infiltration, cytokine expression in islets (by immunohistochemistry and qPCR), as well as islet Glut2 expression and ATP/ADP ratio to determine effects on glucose uptake and metabolism in beta cells. Results: DRLyp/Lyp rats were normoglycaemic and without traces of immune cell infiltrates. However, IVGTTs revealed a significant decrease in the acute insulin response to glucose compared with control rats (1685.3 +/- 121.3 vs 633.3 +/- 148.7; p < 0.0001). In agreement, insulin secretion was severely perturbed in isolated islets, and both first- and second-phase insulin release were lowered compared with control rats, while glucagon secretion was similar in both groups. Interestingly, after 5-7 days of culture of islets from DRLyp/Lyp rats in normal media, glucose-stimulated insulin secretion (GSIS) was improved; although, a significant decrease in GSIS was still evident compared with islets from control rats at this time (7393.9 +/- 1593.7 vs 4416.8 +/- 1230.5 pg islet-1 h-1; p < 0.0001). Compared with controls, OPT of whole pancreas from DRLyp/Lyp rats revealed significant reductions in medium (4.1 x 109 +/- 9.5 x 107 vs 3.8 x 109 +/- 5.8 x 107 μm3; p = 0.044) and small sized islets (1.6 x 109 +/- 5.1 x 107 vs 1.4 x 109 +/- 4.5 x 107 μm3; p = 0.035). Finally

Aims/hypothesis Genetic studies show coupling of genes affecting beta cell function to type 1 diabetes, but hitherto no studies on whether beta cell dysfunction could precede insulitis and clinical onset of type 1 diabetes are available. Methods We used 40-day-old BioBreeding (BB) DRLyp/Lyp rats (a model of spontaneous autoimmune type 1 diabetes) and diabetes-resistant DRLyp/+ and DR+/+ littermates (controls) to investigate beta cell function in vivo, and insulin and glucagon secretion in vitro. Beta cell mass was assessed by optical projection tomography (OPT) and morphometry. Additionally, measurements of intra-islet blood flow were performed using microsphere injections. We also assessed immune cell infiltration, cytokine expression in islets (by immunohistochemistry and qPCR), as well as islet Glut2 expression and ATP/ADP ratio to determine effects on glucose uptake and metabolism in beta cells. Results DRLyp/Lyp rats were normoglycaemic and without traces of immune cell infiltrates. However, IVGTTs revealed a significant decrease in the acute insulin response to glucose compared with control rats (1685.3 +/- 121.3 vs 633.3 +/- 148.7; p < 0.0001). In agreement, insulin secretion was severely perturbed in isolated islets, and both first- and second-phase insulin release were lowered compared with control rats, while glucagon secretion was similar in both groups. Interestingly, after 5-7 days of culture of islets from DRLyp/Lyp rats in normal media, glucose-stimulated insulin secretion (GSIS) was improved; although, a significant decrease in GSIS was still evident compared with islets from control rats at this time (7393.9 +/- 1593.7 vs 4416.8 +/- 1230.5 pg islet(-1) h(-1); p < 0.0001). Compared with controls, OPT of whole pancreas from DRLyp/Lyp rats revealed significant reductions in medium (4.1 x 10(9) +/- 9.5 x 10(7) vs 3.8 x 10(9) +/- 5.8 x 10(7) mu m(3); p = 0.044) and small sized islets (1.6 x 10(9) +/- 5.1 x 10(7) vs 1.4 x 10(9) +/- 4.5 x 10(7) mu m(

Aims/hypothesis: Genetic studies show coupling of genes affecting beta cell function to type 1 diabetes, but hitherto no studies on whether beta cell dysfunction could precede insulitis and clinical onset of type 1 diabetes are available. Methods: We used 40-day-old BioBreeding (BB) DRLyp/Lyp rats (a model of spontaneous autoimmune type 1 diabetes) and diabetes-resistant DRLyp/+ and DR+/+ littermates (controls) to investigate beta cell function in vivo, and insulin and glucagon secretion in vitro. Beta cell mass was assessed by optical projection tomography (OPT) and morphometry. Additionally, measurements of intra-islet blood flow were performed using microsphere injections. We also assessed immune cell infiltration, cytokine expression in islets (by immunohistochemistry and qPCR), as well as islet Glut2 expression and ATP/ADP ratio to determine effects on glucose uptake and metabolism in beta cells. Results: DRLyp/Lyp rats were normoglycaemic and without traces of immune cell infiltrates. However, IVGTTs revealed a significant decrease in the acute insulin response to glucose compared with control rats (1685.3 +/- 121.3 vs 633.3 +/- 148.7; p < 0.0001). In agreement, insulin secretion was severely perturbed in isolated islets, and both first- and second-phase insulin release were lowered compared with control rats, while glucagon secretion was similar in both groups. Interestingly, after 5-7 days of culture of islets from DRLyp/Lyp rats in normal media, glucose-stimulated insulin secretion (GSIS) was improved; although, a significant decrease in GSIS was still evident compared with islets from control rats at this time (7393.9 +/- 1593.7 vs 4416.8 +/- 1230.5 pg islet-1 h-1; p < 0.0001). Compared with controls, OPT of whole pancreas from DRLyp/Lyp rats revealed significant reductions in medium (4.1 x 109 +/- 9.5 x 107 vs 3.8 x 109 +/- 5.8 x 107 μm3; p = 0.044) and small sized islets (1.6 x 109 +/- 5.1 x 107 vs 1.4 x 109 +/- 4.5 x 107 μm3; p = 0.035). Finally

Aims/hypothesis Genetic studies show coupling of genes affecting beta cell function to type 1 diabetes, but hitherto no studies on whether beta cell dysfunction could precede insulitis and clinical onset of type 1 diabetes are available. Methods We used 40-day-old BioBreeding (BB) DRLyp/Lyp rats (a model of spontaneous autoimmune type 1 diabetes) and diabetes-resistant DRLyp/+ and DR+/+ littermates (controls) to investigate beta cell function in vivo, and insulin and glucagon secretion in vitro. Beta cell mass was assessed by optical projection tomography (OPT) and morphometry. Additionally, measurements of intra-islet blood flow were performed using microsphere injections. We also assessed immune cell infiltration, cytokine expression in islets (by immunohistochemistry and qPCR), as well as islet Glut2 expression and ATP/ADP ratio to determine effects on glucose uptake and metabolism in beta cells. Results DRLyp/Lyp rats were normoglycaemic and without traces of immune cell infiltrates. However, IVGTTs revealed a significant decrease in the acute insulin response to glucose compared with control rats (1685.3 +/- 121.3 vs 633.3 +/- 148.7; p < 0.0001). In agreement, insulin secretion was severely perturbed in isolated islets, and both first- and second-phase insulin release were lowered compared with control rats, while glucagon secretion was similar in both groups. Interestingly, after 5-7 days of culture of islets from DRLyp/Lyp rats in normal media, glucose-stimulated insulin secretion (GSIS) was improved; although, a significant decrease in GSIS was still evident compared with islets from control rats at this time (7393.9 +/- 1593.7 vs 4416.8 +/- 1230.5 pg islet(-1) h(-1); p < 0.0001). Compared with controls, OPT of whole pancreas from DRLyp/Lyp rats revealed significant reductions in medium (4.1 x 10(9) +/- 9.5 x 10(7) vs 3.8 x 10(9) +/- 5.8 x 10(7) mu m(3); p = 0.044) and small sized islets (1.6 x 10(9) +/- 5.1 x 10(7) vs 1.4 x 10(9) +/- 4.5 x 10(7) mu m(

Aims/hypothesis Genetic studies show coupling of genes affecting beta cell function to type 1 diabetes, but hitherto no studies on whether beta cell dysfunction could precede insulitis and clinical onset of type 1 diabetes are available. Methods We used 40-day-old BioBreeding (BB) DRLyp/Lyp rats (a model of spontaneous autoimmune type 1 diabetes) and diabetes-resistant DRLyp/+ and DR+/+ littermates (controls) to investigate beta cell function in vivo, and insulin and glucagon secretion in vitro. Beta cell mass was assessed by optical projection tomography (OPT) and morphometry. Additionally, measurements of intra-islet blood flow were performed using microsphere injections. We also assessed immune cell infiltration, cytokine expression in islets (by immunohistochemistry and qPCR), as well as islet Glut2 expression and ATP/ADP ratio to determine effects on glucose uptake and metabolism in beta cells. Results DRLyp/Lyp rats were normoglycaemic and without traces of immune cell infiltrates. However, IVGTTs revealed a significant decrease in the acute insulin response to glucose compared with control rats (1685.3 +/- 121.3 vs 633.3 +/- 148.7; p < 0.0001). In agreement, insulin secretion was severely perturbed in isolated islets, and both first- and second-phase insulin release were lowered compared with control rats, while glucagon secretion was similar in both groups. Interestingly, after 5-7 days of culture of islets from DRLyp/Lyp rats in normal media, glucose-stimulated insulin secretion (GSIS) was improved; although, a significant decrease in GSIS was still evident compared with islets from control rats at this time (7393.9 +/- 1593.7 vs 4416.8 +/- 1230.5 pg islet(-1) h(-1); p < 0.0001). Compared with controls, OPT of whole pancreas from DRLyp/Lyp rats revealed significant reductions in medium (4.1 x 10(9) +/- 9.5 x 10(7) vs 3.8 x 10(9) +/- 5.8 x 10(7) mu m(3); p = 0.044) and small sized islets (1.6 x 10(9) +/- 5.1 x 10(7) vs 1.4 x 10(9) +/- 4.5 x 10(7) mu m(

Aims/hypothesis Genetic studies show coupling of genes affecting beta cell function to type 1 diabetes, but hitherto no studies on whether beta cell dysfunction could precede insulitis and clinical onset of type 1 diabetes are available. Methods We used 40-day-old BioBreeding (BB) DRLyp/Lyp rats (a model of spontaneous autoimmune type 1 diabetes) and diabetes-resistant DRLyp/+ and DR+/+ littermates (controls) to investigate beta cell function in vivo, and insulin and glucagon secretion in vitro. Beta cell mass was assessed by optical projection tomography (OPT) and morphometry. Additionally, measurements of intra-islet blood flow were performed using microsphere injections. We also assessed immune cell infiltration, cytokine expression in islets (by immunohistochemistry and qPCR), as well as islet Glut2 expression and ATP/ADP ratio to determine effects on glucose uptake and metabolism in beta cells. Results DRLyp/Lyp rats were normoglycaemic and without traces of immune cell infiltrates. However, IVGTTs revealed a significant decrease in the acute insulin response to glucose compared with control rats (1685.3 +/- 121.3 vs 633.3 +/- 148.7; p < 0.0001). In agreement, insulin secretion was severely perturbed in isolated islets, and both first- and second-phase insulin release were lowered compared with control rats, while glucagon secretion was similar in both groups. Interestingly, after 5-7 days of culture of islets from DRLyp/Lyp rats in normal media, glucose-stimulated insulin secretion (GSIS) was improved; although, a significant decrease in GSIS was still evident compared with islets from control rats at this time (7393.9 +/- 1593.7 vs 4416.8 +/- 1230.5 pg islet(-1) h(-1); p < 0.0001). Compared with controls, OPT of whole pancreas from DRLyp/Lyp rats revealed significant reductions in medium (4.1 x 10(9) +/- 9.5 x 10(7) vs 3.8 x 10(9) +/- 5.8 x 10(7) mu m(3); p = 0.044) and small sized islets (1.6 x 10(9) +/- 5.1 x 10(7) vs 1.4 x 10(9) +/- 4.5 x 10(7) mu m(

The failure of pancreatic islet β-cells is a major contributor to the etiology of type 2 diabetes. β-Cell dysfunction and declining β-cell mass are two mechanisms that contribute to this failure, although it is unclear whether they are molecularly linked. Here, we show that the cell cycle regulator, cyclin-dependent kinase 2 (CDK2), couples primary β-cell dysfunction to the progressive deterioration of β-cell mass in diabetes. Mice with pancreas-specific deletion of Cdk2 are glucose-intolerant, primarily due to defects in glucose-stimulated insulin secretion. Accompanying this loss of secretion are defects in β-cell metabolism and perturbed mitochondrial structure. Persistent insulin secretion defects culminate in progressive deficits in β-cell proliferation, reduced β-cell mass, and diabetes. These outcomes may be mediated directly by the loss of CDK2, which binds to and phosphorylates the transcription factor FOXO1 in a glucose-dependent manner. Further, we identified a requirement for CDK2 in the compensatory increases in β-cell mass that occur in response to age- and diet-induced stress. Thus, CDK2 serves as an important nexus linking primary β-cell dysfunction to progressive β-cell mass deterioration in diabetes., info:eu-repo/semantics/published

AIMS: Radiolabeled Exendin-4 has been proposed as suitable imaging marker for pancreatic beta cell mass quantification mediated by Glucagon-like peptide-1 receptor (GLP-1R). However, noticeable species variations in basal pancreatic uptake as well as uptake reduction degree due to selective beta cell ablation were observed. METHODS: -Exendin4 Positron Emission Tomography (PET) in the same species. In vitro, ex vivo, and in vivo data formed the basis for calculating the theoretical in vivo contribution of each pancreatic compartment. RESULTS: -Exendin4. CONCLUSIONS: IPR as well as the exocrine GLP-1R density is the main determinants of the species variability in pancreatic uptake. Thus, the IPR in human is an important factor for assessing the potential of GLP-1R as an imaging biomarker for pancreatic beta cells.

AIMS: Radiolabeled Exendin-4 has been proposed as suitable imaging marker for pancreatic beta cell mass quantification mediated by Glucagon-like peptide-1 receptor (GLP-1R). However, noticeable species variations in basal pancreatic uptake as well as uptake reduction degree due to selective beta cell ablation were observed. METHODS: -Exendin4 Positron Emission Tomography (PET) in the same species. In vitro, ex vivo, and in vivo data formed the basis for calculating the theoretical in vivo contribution of each pancreatic compartment. RESULTS: -Exendin4. CONCLUSIONS: IPR as well as the exocrine GLP-1R density is the main determinants of the species variability in pancreatic uptake. Thus, the IPR in human is an important factor for assessing the potential of GLP-1R as an imaging biomarker for pancreatic beta cells.

AIMS: Radiolabeled Exendin-4 has been proposed as suitable imaging marker for pancreatic beta cell mass quantification mediated by Glucagon-like peptide-1 receptor (GLP-1R). However, noticeable species variations in basal pancreatic uptake as well as uptake reduction degree due to selective beta cell ablation were observed. METHODS: -Exendin4 Positron Emission Tomography (PET) in the same species. In vitro, ex vivo, and in vivo data formed the basis for calculating the theoretical in vivo contribution of each pancreatic compartment. RESULTS: -Exendin4. CONCLUSIONS: IPR as well as the exocrine GLP-1R density is the main determinants of the species variability in pancreatic uptake. Thus, the IPR in human is an important factor for assessing the potential of GLP-1R as an imaging biomarker for pancreatic beta cells.

AIMS: Radiolabeled Exendin-4 has been proposed as suitable imaging marker for pancreatic beta cell mass quantification mediated by Glucagon-like peptide-1 receptor (GLP-1R). However, noticeable species variations in basal pancreatic uptake as well as uptake reduction degree due to selective beta cell ablation were observed. METHODS: -Exendin4 Positron Emission Tomography (PET) in the same species. In vitro, ex vivo, and in vivo data formed the basis for calculating the theoretical in vivo contribution of each pancreatic compartment. RESULTS: -Exendin4. CONCLUSIONS: IPR as well as the exocrine GLP-1R density is the main determinants of the species variability in pancreatic uptake. Thus, the IPR in human is an important factor for assessing the potential of GLP-1R as an imaging biomarker for pancreatic beta cells.

AIMS: Radiolabeled Exendin-4 has been proposed as suitable imaging marker for pancreatic beta cell mass quantification mediated by Glucagon-like peptide-1 receptor (GLP-1R). However, noticeable species variations in basal pancreatic uptake as well as uptake reduction degree due to selective beta cell ablation were observed. METHODS: -Exendin4 Positron Emission Tomography (PET) in the same species. In vitro, ex vivo, and in vivo data formed the basis for calculating the theoretical in vivo contribution of each pancreatic compartment. RESULTS: -Exendin4. CONCLUSIONS: IPR as well as the exocrine GLP-1R density is the main determinants of the species variability in pancreatic uptake. Thus, the IPR in human is an important factor for assessing the potential of GLP-1R as an imaging biomarker for pancreatic beta cells.

Noninvasive beta cell mass (BCM) quantification is a crucial tool to understand diabetes development and progression. [(111)In]exendin is a promising agent for in vivo beta cell imaging, but tracer testing has been hampered by the lack of well-defined rodent models., SCOPUS: ar.j, info:eu-repo/semantics/published

Diabetes is characterized by a progressive decline of the pancreatic beta cell mass (BCM), which is responsible for insufficient insulin secretion and hyperglycaemia. There are currently no reliable methods to measure non-invasively the BCM in diabetic patients. Our work describes a phage display-derived peptide (P88) that is highly specific to (FXYD2)γa expressed by human beta cells and is proposed as a molecular vector for the development of functionalized imaging probes. P88 does not bind to the exocrine pancreas and is able to detect down to ~156 human pancreatic islets/mm3 in vitro after conjugation to ultra-small particles of iron oxide (USPIO), as proven by the R2 measured on MR images. For in vivo evaluation, MRI studies were carried out on nude mice bearing Capan-2 tumours that also express (FXYD2)γa. A strong negative contrast was obtained subsequent to the injection of USPIO-P88, but not in negative controls. On human histological sections, USPIO-P88 seems to be specific to pancreatic beta cells, but not to duodenum, stomach or kidney tissues. USPIO-P88 thus represents a novel and promising tool for monitoring pancreatic BCM in diabetic patients. The quantitative correlation between BCM and R2 remains to be demonstrated in vivo, but the T2 mapping and the black pixel estimation after USPIO-P88 injection could provide important information for the future pancreatic BCM evaluation by MRI., SCOPUS: ar.j, info:eu-repo/semantics/published

Clinical islet transplantation is being investigated as a permanent cure for type 1 diabetes mellitus (T1DM). Currently, intraportal infusion of islets is the favoured procedure, but several novel implantation sites have been suggested. Noninvasive longitudinal methodologies are an increasingly important tool for assessing the fate of transplanted islets, their mass, function and early signs of rejection. This article reviews the approaches available for islet graft imaging by positron emission tomography and progress in the field, as well as future challenges and opportunities.

AIMS/HYPOTHESIS: Type 2 diabetes is a bi-hormonal disease characterised by relative hypoinsulinaemia and hyperglucagonaemia with elevated blood glucose levels. Besides pancreatic beta cell defects, a low number of beta cells (low beta cell mass) may contribute to the insufficient secretion of insulin. In this study our aim was to determine whether the alpha cell mass is also altered. METHODS: Using a point counting method, we measured the ratio of alpha to beta cell areas in pancreas samples obtained at autopsy from 50 type 2 diabetic subjects, whose beta cell mass had previously been found to be 36% lower than that of 52 non-diabetic subjects. RESULTS: The topography of alpha and beta cells was similar in both groups: many alpha cells were localised in the centre of the islets and the ratio of alpha/beta cell areas increased with islet size. The average ratio was significantly higher in type 2 diabetic subjects (0.72) than in non-diabetic subjects (0.42), with, however, a large overlap between the two groups. In contrast, the alpha cell mass was virtually identical in type 2 diabetic subjects (366 mg) and non-diabetic subjects (342 mg), and was not influenced by sex, BMI or type of diabetes treatment. CONCLUSIONS: The higher proportion of alpha to beta cells in the islets of some type 2 diabetic subjects is due to a decrease in beta cell number rather than an increase in alpha cell number. This imbalance may contribute to alterations in the normal inhibitory influence exerted by beta cells on alpha cells, and lead to the relative hyperglucagonaemia observed in type 2 diabetes

We sought to establish the relationship between fasting plasma glucose concentrations and pancreatic fractional beta cell area in adult cynomolgus monkeys (Macaca fascicularis). Fasting plasma glucose and pancreatic fractional beta cell area were measured in 18 control and 17 streptozotocin-treated adult primates (17.0 ± 1.2 vs 15.4 ± 1.2 years old). Fasting plasma glucose was increased (12.0 ± 2.0 vs 3.4 ± 0.1 mmol/l, p < 0.01) and fractional beta cell area was decreased (0.62 ± 0.13% vs 2.49 ± 0.35%, p < 0.01) in streptozotocin-treated monkeys. The relationship between fasting plasma glucose and pancreatic fractional beta cell area was described by a wide range of beta cell areas in controls. In streptozotocin-treated monkeys there was an inflection of fasting blood glucose at ∼50% of the mean beta cell area in controls with a steep increase in blood glucose for each further decrement in beta cell area. In adult non-human primates a decrement in fractional beta cell area of ∼50% or more leads to loss of glycaemic control.

Systems biology is an emergent field that aims to understand biological systems at system-level. The increasing power of genome sequencing techniques and ranges of other molecular biology techniques is enabling the accumulation of in-depth knowledge of biological systems. This growing information, properly quantified, analysed and presented, will eventually allow the establishment of a system-based cartography of different cellular populations within the organism, and of their interactions at the tissue and organ levels. It will also allow the identification of specific markers of individual cell types. Systems biology approaches to discover diagnostic markers may have an important role in diabetes. There are presently no reliable ways to quantify beta cell mass (BCM) in vivo, which hampers the understanding of the pathogenesis and natural history of diabetes, and the development of novel therapies to preserve BCM. To solve this problem, novel and specific beta cell biomarkers must be identified to enable adequate in vivo imaging by methods such as Positron Emission Tomography (PET). The ideal biomarker should allow measurements by a minimally invasive technology enabling repeated examinations over time, should identify the early stages of decreased BCM, and should provide information on progression of beta cell loss and eventual responses to agents aiming to arrest or revert beta cell loss in diabetes. The present review briefly describes the "state-of-the-art" in the field, and then proposes a step-by-step systems biology approach for the identification and initial testing of novel candidates for beta cell imaging., Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, info:eu-repo/semantics/published

We sought to establish the relationship between fasting plasma glucose concentrations and pancreatic fractional beta cell area in adult cynomolgus monkeys (Macaca fascicularis). Fasting plasma glucose and pancreatic fractional beta cell area were measured in 18 control and 17 streptozotocin-treated adult primates (17.0 ± 1.2 vs 15.4 ± 1.2 years old). Fasting plasma glucose was increased (12.0 ± 2.0 vs 3.4 ± 0.1 mmol/l, p < 0.01) and fractional beta cell area was decreased (0.62 ± 0.13% vs 2.49 ± 0.35%, p < 0.01) in streptozotocin-treated monkeys. The relationship between fasting plasma glucose and pancreatic fractional beta cell area was described by a wide range of beta cell areas in controls. In streptozotocin-treated monkeys there was an inflection of fasting blood glucose at ∼50% of the mean beta cell area in controls with a steep increase in blood glucose for each further decrement in beta cell area. In adult non-human primates a decrement in fractional beta cell area of ∼50% or more leads to loss of glycaemic control.

Systems biology is an emergent field that aims to understand biological systems at system-level. The increasing power of genome sequencing techniques and ranges of other molecular biology techniques is enabling the accumulation of in-depth knowledge of biological systems. This growing information, properly quantified, analysed and presented, will eventually allow the establishment of a system-based cartography of different cellular populations within the organism, and of their interactions at the tissue and organ levels. It will also allow the identification of specific markers of individual cell types. Systems biology approaches to discover diagnostic markers may have an important role in diabetes. There are presently no reliable ways to quantify beta cell mass (BCM) in vivo, which hampers the understanding of the pathogenesis and natural history of diabetes, and the development of novel therapies to preserve BCM. To solve this problem, novel and specific beta cell biomarkers must be identified to enable adequate in vivo imaging by methods such as Positron Emission Tomography (PET). The ideal biomarker should allow measurements by a minimally invasive technology enabling repeated examinations over time, should identify the early stages of decreased BCM, and should provide information on progression of beta cell loss and eventual responses to agents aiming to arrest or revert beta cell loss in diabetes. The present review briefly describes the "state-of-the-art" in the field, and then proposes a step-by-step systems biology approach for the identification and initial testing of novel candidates for beta cell imaging., Journal Article, Research Support, Non-U.S. Gov't, SCOPUS: ar.j, info:eu-repo/semantics/published

Vesicular monoamine transporter 2 (VMAT2) is expressed in pancreatic beta cells and has recently been proposed as a target for measurement of beta cell mass in vivo. We questioned, (1) What proportion of beta cells express VMAT2? (2) Is VMAT2 expressed by other pancreatic endocrine or non-endocrine cells? (3) Is the relationship between VMAT2 and insulin expression disturbed in type 1 (T1DM) or type 2 diabetes (T2DM)? Human pancreas (7 non-diabetics, 5 T2DM, 10 T1DM) was immunostained for insulin, VMAT2 and other pancreatic hormones. Most beta cells expressed VMAT2. VMAT2 expression was not changed by the presence of diabetes. In tail of pancreas VMAT2 immunostaining closely correlated with insulin staining. However, VMAT2 was also expressed in some pancreatic polypeptide (PP) cells. Although VMAT2 was not excluded as a target for beta cell mass measurement, expression of VMAT2 in PP cells predicts residual VMAT2 expression in human pancreas even in the absence of beta cells.

Vesicular monoamine transporter 2 (VMAT2) is expressed in pancreatic beta cells and has recently been proposed as a target for measurement of beta cell mass in vivo. We questioned, (1) What proportion of beta cells express VMAT2? (2) Is VMAT2 expressed by other pancreatic endocrine or non-endocrine cells? (3) Is the relationship between VMAT2 and insulin expression disturbed in type 1 (T1DM) or type 2 diabetes (T2DM)? Human pancreas (7 non-diabetics, 5 T2DM, 10 T1DM) was immunostained for insulin, VMAT2 and other pancreatic hormones. Most beta cells expressed VMAT2. VMAT2 expression was not changed by the presence of diabetes. In tail of pancreas VMAT2 immunostaining closely correlated with insulin staining. However, VMAT2 was also expressed in some pancreatic polypeptide (PP) cells. Although VMAT2 was not excluded as a target for beta cell mass measurement, expression of VMAT2 in PP cells predicts residual VMAT2 expression in human pancreas even in the absence of beta cells.