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1.
Am J Physiol Endocrinol Metab ; 317(6): E1081-E1093, 2019 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-31503512

RESUMO

DPP-4 inhibitors, used for treatment of type 2 diabetes, act by increasing the concentrations of intact glucagon-like peptide-1 (GLP-1), but at the same time, they inhibit secretion of GLP-1, perhaps by a negative feedback mechanism. We hypothesized that GLP-1 secretion is feedback regulated by somatostatin (SS) from neighboring D-cells, and blocking this feedback circuit results in increased GLP-1 secretion. We used a wide range of experimental techniques, including gene expression analysis, immunohistochemical approaches, and the perfused mouse intestine to characterize the paracrine circuit controlling GLP-1 and SS. We show that 1) antagonizing the SS receptor (SSTr) 2 and SSTr5 led to increased GLP-1 and SS secretion in the mouse, 2) SS exhibits strong tonic inhibition of GLP-1 secretion preferentially through SSTr5, and 3) the secretion of S was GLP-1 receptor dependent. We conclude that SS is a tonic inhibitor of GLP-1 secretion, and interventions in the somatostain-GLP-1 paracrine loop lead to increased GLP-1 secretion.


Assuntos
Células Enteroendócrinas/metabolismo , Peptídeo 1 Semelhante ao Glucagon/metabolismo , Receptor do Peptídeo Semelhante ao Glucagon 1/metabolismo , Mucosa Intestinal/metabolismo , Comunicação Parácrina , Células Secretoras de Somatostatina/metabolismo , Somatostatina/metabolismo , Animais , Inibidores da Dipeptidil Peptidase IV/farmacologia , Células Enteroendócrinas/efeitos dos fármacos , Peptídeo 1 Semelhante ao Glucagon/efeitos dos fármacos , Mucosa Intestinal/citologia , Intestino Delgado/citologia , Intestino Delgado/metabolismo , Intestinos , Camundongos , Receptores de Somatostatina/antagonistas & inibidores , Receptores de Somatostatina/metabolismo , Somatostatina/farmacologia , Somatostatina-28/farmacologia , Células Secretoras de Somatostatina/efeitos dos fármacos
2.
Folia Histochem Cytobiol ; 57(3): 101-115, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31396945

RESUMO

Insulin-producing cells derived from in vitro differentiation of stem cells and non-stem cells by using different factors can spare the need for genetic manipulation and provide a cure for diabetes. In this context, pancreatic progenitors differentiating to ß-like cells garner increasing attention as ß-cell replacement source. This kind of cell therapy has the potential to cure diabetes, but is still on its way of being clinically useful. The primary restriction for in vitro production of mature and functional ß-cells is developing a physiologically relevant in vitro culture system which can mimic in vivo pathways of islet development. In order to achieve this target, different approaches have been attempted for the differentiation of pancreatic stem/progenitor cells to ß-like cells. Here, we will review some of the state-of-the-art protocols for the differentiation of pancreatic progenitors and differentiated pancreatic cells into ß-like cells with a focus on pancreatic duct cells.


Assuntos
Células Acinares/metabolismo , Diferenciação Celular , Células Secretoras de Glucagon/metabolismo , Células Secretoras de Insulina/metabolismo , Células-Tronco Mesenquimais/metabolismo , Células Secretoras de Somatostatina/metabolismo , Células Acinares/transplante , Animais , Diabetes Mellitus/terapia , Células Secretoras de Glucagon/transplante , Humanos , Insulina/metabolismo , Transplante das Ilhotas Pancreáticas , Transplante de Células-Tronco Mesenquimais
3.
Nat Commun ; 10(1): 3700, 2019 08 16.
Artigo em Inglês | MEDLINE | ID: mdl-31420552

RESUMO

Little is known about the role of islet delta cells in regulating blood glucose homeostasis in vivo. Delta cells are important paracrine regulators of beta cell and alpha cell secretory activity, however the structural basis underlying this regulation has yet to be determined. Most delta cells are elongated and have a well-defined cell soma and a filopodia-like structure. Using in vivo optogenetics and high-speed Ca2+ imaging, we show that these filopodia are dynamic structures that contain a secretory machinery, enabling the delta cell to reach a large number of beta cells within the islet. This provides for efficient regulation of beta cell activity and is modulated by endogenous IGF-1/VEGF-A signaling. In pre-diabetes, delta cells undergo morphological changes that may be a compensation to maintain paracrine regulation of the beta cell. Our data provides an integrated picture of how delta cells can modulate beta cell activity under physiological conditions.


Assuntos
Ilhotas Pancreáticas/ultraestrutura , Comunicação Parácrina , Estado Pré-Diabético/patologia , Pseudópodes/ultraestrutura , Células Secretoras de Somatostatina/ultraestrutura , Animais , Glicemia/metabolismo , Humanos , Fator de Crescimento Insulin-Like I/metabolismo , Células Secretoras de Insulina/citologia , Células Secretoras de Insulina/metabolismo , Células Secretoras de Insulina/ultraestrutura , Microscopia Intravital , Ilhotas Pancreáticas/citologia , Ilhotas Pancreáticas/metabolismo , Ilhotas Pancreáticas/patologia , Camundongos , Camundongos Transgênicos , Microscopia Eletrônica , Imagem Óptica , Optogenética , Estado Pré-Diabético/metabolismo , Pseudópodes/metabolismo , Células Secretoras de Somatostatina/citologia , Células Secretoras de Somatostatina/metabolismo , Fator A de Crescimento do Endotélio Vascular/metabolismo
4.
Acta Histochem ; 121(5): 638-645, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31146895

RESUMO

In the human pancreas, various forms of endocrine cell arrangement are found: single endocrine cells, endocrine cell clusters, and mantel, bipolar and mosaic cell (mixed) islets. Our aim was to analyse the distribution and dynamics of insulin-, glucagon- and somatostatin-containing cells within the various forms of endocrine pancreas arrangement during human prenatal development and in adults and to suggest a mechanism of change in the endocrine cell ratio in adult islets. Pancreatic autopsies derived from human foetuses from the 10th to the 40th weeks of development and from adults were examined using histological, immunohistochemical and morphometric methods. During development, the human endocrine pancreas undergoes not only de novo differentiation of endocrine cells and islet formation, but morphogenetic restructuring, which is revealed as a change of the α-, ß- and δ-cell ratio in the islets. In particular, increased proportion of glucagon- and somatostatin-containing cells and decreased proportion of ß-cells were shown in the largest mosaic islets in adults. Our results indicate that the distribution and proportion of α-, ß- and δ-cells depend on the islets size and vascularisation. Studying of the mechanism of such restructuring may contribute to the development of new approaches in the treatment of diabetes mellitus.


Assuntos
Células Secretoras de Glucagon/citologia , Células Secretoras de Insulina/citologia , Ilhotas Pancreáticas/citologia , Ilhotas Pancreáticas/embriologia , Pâncreas/citologia , Células Secretoras de Somatostatina/citologia , Desenvolvimento Embrionário , Humanos
5.
Biochem Biophys Res Commun ; 512(4): 864-870, 2019 05 14.
Artigo em Inglês | MEDLINE | ID: mdl-30929915

RESUMO

Pancreatic δ-cells, which produce somatostatin, play an indispensable role in glucose homeostasis by inhibiting glucagon and insulin secretion in a paracrine manner. Recent studies have shown that δ-cells are couple with ß-cells to suppress α-cell activity. Under certain circumstances, δ-cells could also be trans-differentiated into insulin-producing ß-cells. Thus, pancreatic islet may benefit from δ-cell hyperplasia. However, an effective way to increase δ-cell mass has been rarely reported. Here, we found that REMD 2.59, a human monoclonal antibody and competitive antagonist of the glucagon receptor, massively boosted δ-cell number and increased plasma somatostatin level in both normoglycemic and type 1 diabetic (T1D) mice. The increased δ-cells were due to both δ-cell proliferation and derivation of duct lining cells. Notably, the enlarged δ-cell mass could reduce ß-cell burdens by inducing FoxO1 nuclear translocation in normoglycemic mice. Moreover, some somatostatin-positive cells were co-localized with C-peptide in T1D mice, suggesting that δ-cells might be a source of the newborn ß-cells. Collectively, these observations suggest that treatment with the glucagon receptor monoclonal antibody can increase pancreatic δ-cell mass by promoting self-replication and inducing duct-derived neogenesis both in normoglycemia and diabetic mice.


Assuntos
Anticorpos Monoclonais/farmacologia , Hipoglicemiantes/farmacologia , Receptores de Glucagon/antagonistas & inibidores , Células Secretoras de Somatostatina/metabolismo , Animais , Animais Recém-Nascidos , Proliferação de Células/efeitos dos fármacos , Forma Celular , Diabetes Mellitus Experimental/tratamento farmacológico , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Experimental/patologia , Diabetes Mellitus Tipo 1/tratamento farmacológico , Diabetes Mellitus Tipo 1/metabolismo , Diabetes Mellitus Tipo 1/patologia , Glucagon/sangue , Humanos , Insulina/sangue , Camundongos Endogâmicos C57BL , Somatostatina/sangue , Células Secretoras de Somatostatina/efeitos dos fármacos
6.
Diabetes ; 68(6): 1197-1209, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30936149

RESUMO

ZnT8 is a zinc transporter enriched in pancreatic ß-cells, and its polymorphism is associated with increased susceptibility to type 2 diabetes. However, the exact role of ZnT8 in systemic energy metabolism remains elusive. In this study, we found that ZnT8 knockout mice displayed increased adiposity without obvious weight gain. We also observed that the intestinal tract morphology, motility, and gut microbiota were changed in ZnT8 knockout mice. Further study demonstrated that ZnT8 was expressed in enteroendocrine cells, especially in 5-hydroxytryptamine (5-HT)-positive enterochromaffin cells. Lack of ZnT8 resulted in an elevated circulating 5-HT level owing to enhanced expression of tryptophan hydroxylase 1. Blocking 5-HT synthesis in ZnT8-deficient mice restored adiposity, high-fat diet-induced obesity, and glucose intolerance. Moreover, overexpression of human ZnT8 diabetes high-risk allele R325W increased 5-HT levels relative to the low-risk allele in RIN14B cells. Our study revealed an unexpected role of ZnT8 in regulating peripheral 5-HT biogenesis and intestinal microenvironment, which might contribute to the increased risk of obesity and type 2 diabetes.


Assuntos
Adiposidade/genética , Células Enterocromafins/metabolismo , Microbioma Gastrointestinal , Motilidade Gastrointestinal/genética , Serotonina/biossíntese , Transportador 8 de Zinco/genética , Animais , Linhagem Celular , Colo/citologia , Colo/metabolismo , Colo/patologia , Diabetes Mellitus Tipo 2/genética , Metabolismo Energético , Células Enteroendócrinas/metabolismo , Humanos , Camundongos , Camundongos Knockout , Serotonina/metabolismo , Células Secretoras de Somatostatina , Triptofano Hidroxilase/metabolismo
7.
Diabetes ; 68(6): 1230-1239, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30936150

RESUMO

Pancreatic ß-cells play a pivotal role in maintaining normoglycemia. Recent studies have revealed that the ß-cell is not a homogeneous cell population but, rather, is heterogeneous in a number of properties such as electrical activity, gene expression, and cell surface markers. Identification of specific ß-cell subpopulations altered in diabetic conditions would open a new avenue to develop targeted therapeutic interventions. As intense studies of ß-cell heterogeneity are anticipated in the next decade, it is important that heterogeneity of the islet be recognized. Many studies in the past were undertaken with a small sample of islets, which might overlook important individual variance. In this study, by systematic analyses of the human islet in two and three dimensions, we demonstrate islet heterogeneity in size, number, architecture, cellular composition, and capillary density. There is no stereotypic human islet, and thus, a sufficient number of islets should be examined to ensure study reproducibility.


Assuntos
Células Secretoras de Glucagon/citologia , Células Secretoras de Insulina/citologia , Ilhotas Pancreáticas/citologia , Células Secretoras de Somatostatina/citologia , Adolescente , Adulto , Idoso , Animais , Células Endócrinas/citologia , Células Endócrinas/metabolismo , Feminino , Células Secretoras de Glucagon/metabolismo , Humanos , Imageamento Tridimensional , Imuno-Histoquímica , Células Secretoras de Insulina/metabolismo , Ilhotas Pancreáticas/irrigação sanguínea , Ilhotas Pancreáticas/metabolismo , Masculino , Camundongos , Microscopia Confocal , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , Células Secretoras de Somatostatina/metabolismo , Adulto Jovem
8.
Eur J Histochem ; 63(1)2019 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-30827082

RESUMO

The Lake Van fish (Alburnus tarichi) is a species that is endemic to Turkey's Lake Van basin. In this study, the regional distribution, volume density, and relative frequency of some pancreatic endocrine cells in Lake Van fish were investigated via immunohistochemistry using specific mammalian antibodies. The pancreatic tissue was observed to be surrounded by adipose tissue, which was adjacent to the gall bladder or extrahepatic bile duct, or dispersed in the adipose tissue ranked among coils of post-esophageal swelling and intestine. The pancreatic endocrine cells were examined, including the islets, exocrine pancreas, and pancreatic ducts. According to the modified aldehyde fuchsin staining and immunohistochemistry, insulin-secreting beta cells were observed to localize throughout the islets. Glucagon immune-reactive (IR) cells were observed to be situated moderately on the islet periphery, and were rarely determined in the islet central region. A small number of somatostatin-IR cells were observed in the islet centers and peripheries. Similar distributions of those 3 endocrine cells were also determined in the secondary islets. Additionally, the endocrine cell percentages did not differ between the primary and secondary islets; insulin-, glucagon- and somatostatin-IR cells comprised approximately 54%, 29%, and 11% of the endocrine cells in the principal islets, whereas they comprised 52%, 27%, and 14% in the secondary islets, respectively. Insulin-, glucagon- and somatostatin-IR cells were also determined among the epithelium and subepithelial connective tissue in the pancreatic ducts or exocrine areas of the pancreas. With this study, the existence, regional distribution, and relative frequency of the insulin-, glucagon- and somatostatin-IR cells were first investigated in the pancreatic tissue of Lake Van fish and the results were discussed.


Assuntos
Células Secretoras de Glucagon/citologia , Células Secretoras de Insulina/citologia , Ilhotas Pancreáticas/anatomia & histologia , Células Secretoras de Somatostatina/citologia , Animais , Cyprinidae , Imuno-Histoquímica , Pâncreas Exócrino/anatomia & histologia , Pâncreas Exócrino/citologia , Turquia
9.
Physiology (Bethesda) ; 33(6): 403-411, 2018 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-30303773

RESUMO

The role of beta and α-cells to glucose control are established, but the physiological role of δ-cells is poorly understood. Delta-cells are ideally positioned within pancreatic islets to modulate insulin and glucagon secretion at their source. We review the evidence for a negative feedback loop between delta and ß-cells that determines the blood glucose set point and suggest that local δ-cell-mediated feedback stabilizes glycemic control.


Assuntos
Glucose/metabolismo , Células Secretoras de Somatostatina/metabolismo , Animais , Glicemia/metabolismo , Humanos , Insulina/metabolismo , Secreção de Insulina/fisiologia , Células Secretoras de Insulina/metabolismo , Ilhotas Pancreáticas/metabolismo
10.
Bioessays ; 40(11): e1800119, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30264410

RESUMO

We recently discovered a novel subset of beta cells that resemble immature beta cells during pancreas development. We named these "virgin" beta cells as they do not stem from existing mature beta cells. Virgin beta cells are found exclusively at the islet periphery in areas that we therefore designated as the "neogenic niche." As beta cells are our only source of insulin, their loss leads to diabetes. Islets also contain glucagon-producing alpha cells and somatostatin-producing delta cells, that are important for glucose homeostasis and form a mantle surrounding the beta cell core. This 3D architecture is important and determines access to blood flow and innervation. We propose that the distinctive islet architecture may also play an important, but hitherto unappreciated role in generation of new endocrine cells, including beta cells. We discuss several predictions to further test the contribution of the neogenic niche to beta cell regeneration.


Assuntos
Transdiferenciação Celular/fisiologia , Células Secretoras de Glucagon/citologia , Células Secretoras de Insulina/citologia , Ilhotas Pancreáticas/citologia , Células Secretoras de Somatostatina/citologia , Diabetes Mellitus Tipo 1/patologia , Células Secretoras de Glucagon/metabolismo , Humanos , Células Secretoras de Insulina/classificação , Células Secretoras de Insulina/metabolismo , Ilhotas Pancreáticas/metabolismo , Células Secretoras de Somatostatina/metabolismo
11.
Diabetes Obes Metab ; 20 Suppl 2: 137-144, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-30230173

RESUMO

While a number of structural and cellular abnormalities occur in the islet of Langerhans in diabetes, and in particular in type 2 diabetes, the focus has been mostly on the insulin producing ß-cells and only more recently on glucagon producing α- and δ-cells. There is ample evidence that in type 2 diabetes mellitus (T2DM), in addition to a progressive decline in ß-cell function and associated insulin resistance in a number of insulin-sensitive tissues, alterations in glucagon secretion are also present and may play an important role in the pathogenesis of hyperglycemia both in the fasting and in the postprandial state. Recently, a number of studies have showed that there are also functional and structural alterations in glucagon-producing α-cells and somatostatin-producing δ-cells. Thus, it is becoming increasingly clear that multiple cellular alterations of multiple cell types occur, which adds even more complexity to our understanding of the pathophysiology of this common and severe disease. We believe that persistent efforts to increase the understanding of the pathophysiology of hormone secretion in the islets of Langerhans will also improve our capability to better prevent and treat diabetes mellitus.


Assuntos
Glicemia/metabolismo , Diabetes Mellitus Tipo 2/patologia , Ilhotas Pancreáticas/citologia , Amiloide/metabolismo , Animais , Células Secretoras de Glucagon/ultraestrutura , Haplorrinos , Humanos , Ilhotas Pancreáticas/ultraestrutura , Camundongos , Modelos Animais , Células Secretoras de Polipeptídeo Pancreático/ultraestrutura , Papio , Ratos , Células Secretoras de Somatostatina/ultraestrutura
12.
Purinergic Signal ; 14(3): 285-298, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29974392

RESUMO

With immunohistochemical and Western blot techniques, P2X1 receptors were detected in the whole mouse gastrointestinal tract and pancreatic islets of mouse and human. (1) δ Cells containing somatostatin (SOM) in the stomach corpus, small intestines, distal colon, pancreatic islets of both mouse and human express P2X1 receptors; (2) strong immunofluorescence of P2X1 receptors was detected in smooth muscle fibers and capillary networks of the villus core of mouse intestine; and (3) P2X1 receptor-immunoreactive neurons were also detected widely in both mouse myenteric and submucosal plexuses, all of which express SOM. The present data implies that ATP via P2X1 receptors is involved in SOM release from pancreatic δ cells, enteric neurons, and capillary networks in villi.


Assuntos
Trato Gastrointestinal/metabolismo , Ilhotas Pancreáticas/metabolismo , Receptores Purinérgicos P2X1/metabolismo , Células Secretoras de Somatostatina/metabolismo , Animais , Trato Gastrointestinal/citologia , Humanos , Ilhotas Pancreáticas/citologia , Camundongos , Plexo Mientérico/citologia , Plexo Mientérico/metabolismo , Células Secretoras de Somatostatina/citologia
13.
Cell Death Dis ; 9(6): 682, 2018 06 07.
Artigo em Inglês | MEDLINE | ID: mdl-29880854

RESUMO

The somatostatin (SST)-secreting cells were mainly distributed in the pancreatic islets, brain, stomach and intestine in mammals and have many physiological functions. In particular, the SST-secreting δ cell is the third most common cell type in the islets of Langerhans. Recent studies have suggested that dysregulation of paracrine interaction between the pancreatic δ cells and ß cells results in impaired glucose homeostasis and contributes to diabetes development. However, direct evidence of the functional importance of SST cells in glucose homeostasis control is still lacking. In the present study, we specifically ablated SST-secreting cells by crossing Sst-cre transgenic mice with R26 DTA mice (Sst Cre R26 DTA ). The Sst Cre R26 DTA mice exhibited neonatal death. The life spans of these mice with severe hypoglycemia were extended by glucose supplementation. Moreover, we observed that SST cells deficiency led to increased insulin content and excessive insulin release, which might contribute to the observed hypoglycemia. Unexpectedly, although SST is critical for the regulation of insulin content, factors other than SST that are produced by pancreatic δ cells via their endogenous corticotropin-releasing hormone receptor 2 (CRHR2) activity play the main roles in maintaining normal insulin release, as well as neonatal glucose homeostasis in the resting state. Taken together, our results identified that the SST cells in neonatal mouse played critical role in control of insulin release and normal islet function. Moreover, we provided direct in vivo evidence of the functional importance of the SST cells, which are essential for neonatal survival and the maintenance of glucose homeostasis.


Assuntos
Ilhotas Pancreáticas/patologia , Ilhotas Pancreáticas/fisiopatologia , Células Secretoras de Somatostatina/metabolismo , Animais , Animais Recém-Nascidos , Glucose/metabolismo , Humanos , Hipoglicemia/patologia , Insulina/biossíntese , Secreção de Insulina , Camundongos Endogâmicos C57BL , Modelos Biológicos , Ratos Wistar , Receptores de Hormônio Liberador da Corticotropina/metabolismo , Receptores de Somatostatina/metabolismo
14.
Nat Rev Endocrinol ; 14(7): 404-414, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29773871

RESUMO

The somatostatin-secreting δ-cells comprise ~5% of the cells of the pancreatic islets. The δ-cells have complex morphology and might interact with many more islet cells than suggested by their low numbers. δ-Cells contain ATP-sensitive potassium channels, which open at low levels of glucose but close when glucose is elevated. This closure initiates membrane depolarization and electrical activity and increased somatostatin secretion. Factors released by neighbouring α-cells or ß-cells amplify the glucose-induced effects on somatostatin secretion from δ-cells, which act locally within the islets as paracrine or autocrine inhibitors of insulin, glucagon and somatostatin secretion. The effects of somatostatin are mediated by activation of somatostatin receptors coupled to the inhibitory G protein, which culminates in suppression of the electrical activity and exocytosis in α-cells and ß-cells. Somatostatin secretion is perturbed in animal models of diabetes mellitus, which might explain the loss of appropriate hypoglycaemia-induced glucagon secretion, a defect that could be mitigated by somatostatin receptor 2 antagonists. Somatostatin antagonists or agents that suppress somatostatin secretion have been proposed as an adjunct to insulin therapy. In this Review, we summarize the cell physiology of somatostatin secretion, what might go wrong in diabetes mellitus and the therapeutic potential of agents targeting somatostatin secretion or action.


Assuntos
Diabetes Mellitus/fisiopatologia , Glucagon/metabolismo , Receptores de Somatostatina/antagonistas & inibidores , Células Secretoras de Somatostatina/metabolismo , Animais , Biomarcadores/metabolismo , Estudos de Casos e Controles , Diabetes Mellitus/metabolismo , Feminino , Humanos , Hipoglicemia/prevenção & controle , Masculino , Prognóstico , Receptores de Somatostatina/metabolismo , Valores de Referência , Somatostatina/metabolismo , Células Secretoras de Somatostatina/efeitos dos fármacos , Resultado do Tratamento
15.
Genetics ; 209(1): 335-356, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29567659

RESUMO

The majority of gene loci that have been associated with type 2 diabetes play a role in pancreatic islet function. To evaluate the role of islet gene expression in the etiology of diabetes, we sensitized a genetically diverse mouse population with a Western diet high in fat (45% kcal) and sucrose (34%) and carried out genome-wide association mapping of diabetes-related phenotypes. We quantified mRNA abundance in the islets and identified 18,820 expression QTL. We applied mediation analysis to identify candidate causal driver genes at loci that affect the abundance of numerous transcripts. These include two genes previously associated with monogenic diabetes (PDX1 and HNF4A), as well as three genes with nominal association with diabetes-related traits in humans (FAM83E, IL6ST, and SAT2). We grouped transcripts into gene modules and mapped regulatory loci for modules enriched with transcripts specific for α-cells, and another specific for δ-cells. However, no single module enriched for ß-cell-specific transcripts, suggesting heterogeneity of gene expression patterns within the ß-cell population. A module enriched in transcripts associated with branched-chain amino acid metabolism was the most strongly correlated with physiological traits that reflect insulin resistance. Although the mice in this study were not overtly diabetic, the analysis of pancreatic islet gene expression under dietary-induced stress enabled us to identify correlated variation in groups of genes that are functionally linked to diabetes-associated physiological traits. Our analysis suggests an expected degree of concordance between diabetes-associated loci in the mouse and those found in human populations, and demonstrates how the mouse can provide evidence to support nominal associations found in human genome-wide association mapping.


Assuntos
Estudos de Associação Genética , Ilhotas Pancreáticas/fisiologia , Locos de Características Quantitativas , Característica Quantitativa Herdável , Alelos , Animais , Biologia Computacional/métodos , Diabetes Mellitus Experimental , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/metabolismo , Perfilação da Expressão Gênica , Regulação da Expressão Gênica , Redes Reguladoras de Genes , Estudo de Associação Genômica Ampla/métodos , Genótipo , Células Secretoras de Glucagon/metabolismo , Haplótipos , Humanos , Camundongos , Células Secretoras de Somatostatina/metabolismo , Transcriptoma , Navegador
16.
Mol Metab ; 9: 84-97, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29402588

RESUMO

OBJECTIVE: Single-cell RNA sequencing studies have revealed that the type-2 diabetes associated two-pore domain K+ (K2P) channel TALK-1 is abundantly expressed in somatostatin-secreting δ-cells. However, a physiological role for TALK-1 in δ-cells remains unknown. We previously determined that in ß-cells, K+ flux through endoplasmic reticulum (ER)-localized TALK-1 channels enhances ER Ca2+ leak, modulating Ca2+ handling and insulin secretion. As glucose amplification of islet somatostatin release relies on Ca2+-induced Ca2+ release (CICR) from the δ-cell ER, we investigated whether TALK-1 modulates δ-cell Ca2+ handling and somatostatin secretion. METHODS: To define the functions of islet δ-cell TALK-1 channels, we generated control and TALK-1 channel-deficient (TALK-1 KO) mice expressing fluorescent reporters specifically in δ- and α-cells to facilitate cell type identification. Using immunofluorescence, patch clamp electrophysiology, Ca2+ imaging, and hormone secretion assays, we assessed how TALK-1 channel activity impacts δ- and α-cell function. RESULTS: TALK-1 channels are expressed in both mouse and human δ-cells, where they modulate glucose-stimulated changes in cytosolic Ca2+ and somatostatin secretion. Measurement of cytosolic Ca2+ levels in response to membrane potential depolarization revealed enhanced CICR in TALK-1 KO δ-cells that could be abolished by depleting ER Ca2+ with sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) inhibitors. Consistent with elevated somatostatin inhibitory tone, we observed significantly reduced glucagon secretion and α-cell Ca2+ oscillations in TALK-1 KO islets, and found that blockade of α-cell somatostatin signaling with a somatostatin receptor 2 (SSTR2) antagonist restored glucagon secretion in TALK-1 KO islets. CONCLUSIONS: These data indicate that TALK-1 reduces δ-cell cytosolic Ca2+ elevations and somatostatin release by limiting δ-cell CICR, modulating the intraislet paracrine signaling mechanisms that control glucagon secretion.


Assuntos
Sinalização do Cálcio , Canais de Potássio de Domínios Poros em Tandem/metabolismo , Células Secretoras de Somatostatina/metabolismo , Somatostatina/metabolismo , Animais , Células Cultivadas , Citoplasma/metabolismo , Retículo Endoplasmático/metabolismo , Glucagon/metabolismo , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Canais de Potássio de Domínios Poros em Tandem/genética
18.
J Physiol ; 596(2): 197-215, 2018 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-28975620

RESUMO

KEY POINTS: We used a mouse expressing a light-sensitive ion channel in ß-cells to understand how α-cell activity is regulated by ß-cells. Light activation of ß-cells triggered a suppression of α-cell activity via gap junction-dependent activation of δ-cells. Mathematical modelling of human islets suggests that 23% of the inhibitory effect of glucose on glucagon secretion is mediated by ß-cells via gap junction-dependent activation of δ-cells/somatostatin secretion. ABSTRACT: Glucagon, the body's principal hyperglycaemic hormone, is released from α-cells of the pancreatic islet. Secretion of this hormone is dysregulated in type 2 diabetes mellitus but the mechanisms controlling secretion are not well understood. Regulation of glucagon secretion by factors secreted by neighbouring ß- and δ-cells (paracrine regulation) have been proposed to be important. In this study, we explored the importance of paracrine regulation by using an optogenetic strategy. Specific light-induced activation of ß-cells in mouse islets expressing the light-gated channelrhodopsin-2 resulted in stimulation of electrical activity in δ-cells but suppression of α-cell activity. Activation of the δ-cells was rapid and sensitive to the gap junction inhibitor carbenoxolone, whereas the effect on electrical activity in α-cells was blocked by CYN 154806, an antagonist of the somatostatin-2 receptor. These observations indicate that optogenetic activation of the ß-cells propagates to the δ-cells via gap junctions, and the consequential stimulation of somatostatin secretion inhibits α-cell electrical activity by a paracrine mechanism. To explore whether this pathway is important for regulating α-cell activity and glucagon secretion in human islets, we constructed computational models of human islets. These models had detailed architectures based on human islets and consisted of a collection of >500 α-, ß- and δ-cells. Simulations of these models revealed that this gap junctional/paracrine mechanism accounts for up to 23% of the suppression of glucagon secretion by high glucose.


Assuntos
Simulação por Computador , Junções Comunicantes/fisiologia , Células Secretoras de Glucagon/fisiologia , Células Secretoras de Insulina/fisiologia , Células Secretoras de Somatostatina/fisiologia , Animais , Cálcio/metabolismo , Comunicação Celular , Células Cultivadas , Feminino , Células Secretoras de Glucagon/citologia , Células Secretoras de Glucagon/metabolismo , Glucose/metabolismo , Insulina/metabolismo , Células Secretoras de Insulina/citologia , Células Secretoras de Insulina/metabolismo , Masculino , Camundongos , Somatostatina/metabolismo , Células Secretoras de Somatostatina/citologia , Células Secretoras de Somatostatina/metabolismo
19.
Sci Rep ; 7(1): 16398, 2017 11 27.
Artigo em Inglês | MEDLINE | ID: mdl-29180621

RESUMO

Pancreatic beta-cell mass is a critical determinant of the progression of diabetes. The loss of beta-cells in various types of diabetes has been documented in comparison to age, sex and body mass index (BMI) matched control subjects. However, the underlying heterogeneity of beta-cell mass in healthy individuals has not been considered. In this study, the inter-individual heterogeneity in beta-cell/islet mass was examined among 10 cases of age-matched non-diabetic male subjects in relation to BMI, pancreas weight, and the percent ratio, volume and number of islets in the whole pancreas. Beta-cell/islet mass was measured using a large-scale unbiased quantification method. In contrast to previous studies, we found no clinically relevant correlation between beta-cell/islet mass and age, BMI or pancreas weight, with large differences in beta-cell/islet mass and islet number among the individuals. Our method extracts the comprehensive information out of individual pancreas providing multifaceted parameters to study the intrinsic heterogeneity of the human pancreas.


Assuntos
Variação Biológica Individual , Contagem de Células , Células Secretoras de Insulina/citologia , Ilhotas Pancreáticas/citologia , Adulto , Diabetes Mellitus Tipo 2/patologia , Feminino , Células Secretoras de Glucagon/citologia , Humanos , Imuno-Histoquímica , Masculino , Microscopia Confocal , Tamanho do Órgão , Células Secretoras de Somatostatina/citologia
20.
Endocrinology ; 158(10): 3526-3539, 2017 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-28977590

RESUMO

Although kisspeptin is the primary stimulator of gonadotropin-releasing hormone secretion and therefore the hypothalamic-pituitary-gonadal axis, recent findings suggest kisspeptin can also regulate additional neuroendocrine processes including release of growth hormone (GH). Here we show that central delivery of kisspeptin causes a robust rise in plasma GH in fasted but not fed sheep. Kisspeptin-induced GH secretion was similar in animals fasted for 24 hours and those fasted for 72 hours, suggesting that the factors involved in kisspeptin-induced GH secretion are responsive to loss of food availability and not the result of severe negative energy balance. Pretreatment with the neuropeptide Y (NPY) Y1 receptor antagonist, BIBO 3304, blocked the effects of kisspeptin-induced GH release, implicating NPY as an intermediary. Kisspeptin treatment induced c-Fos in NPY and GH-releasing hormone (GHRH) cells of the arcuate nucleus. The same kisspeptin treatment resulted in a reduction in c-Fos in somatostatin (SS) cells in the periventricular nucleus. Finally, blockade of systemic ghrelin release or antagonism of the ghrelin receptor eliminated or reduced the ability of kisspeptin to induce GH release, suggesting the presence of ghrelin is required for kisspeptin-induced GH release in fasted animals. Our findings support the hypothesis that during short-term fasting, systemic ghrelin concentrations and NPY expression in the arcuate nucleus rise. This permits kisspeptin activation of NPY cells. In turn, NPY stimulates GHRH cells and inhibits SS cells, resulting in GH release. We propose a mechanism by which kisspeptin conveys reproductive and hormone status onto the somatotropic axis, resulting in alterations in GH release.


Assuntos
Grelina/metabolismo , Hormônio do Crescimento/efeitos dos fármacos , Kisspeptinas/farmacologia , Neuropeptídeo Y/metabolismo , Células Secretoras de Somatostatina/efeitos dos fármacos , Animais , Núcleo Arqueado do Hipotálamo/efeitos dos fármacos , Núcleo Arqueado do Hipotálamo/metabolismo , Arginina/análogos & derivados , Arginina/farmacologia , Atropina/farmacologia , Jejum/metabolismo , Feminino , Imunofluorescência , Hormônio do Crescimento/metabolismo , Hormônio Liberador de Hormônio do Crescimento , Antagonistas Muscarínicos/farmacologia , Oligopeptídeos/farmacologia , Proteínas Proto-Oncogênicas c-fos/efeitos dos fármacos , Proteínas Proto-Oncogênicas c-fos/metabolismo , Receptores de Grelina/antagonistas & inibidores , Receptores de Neuropeptídeo Y/antagonistas & inibidores , Ovinos , Carneiro Doméstico , Células Secretoras de Somatostatina/metabolismo
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