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1.
Int J Mol Sci ; 22(17)2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34502413

RESUMO

Type 2 Diabetes Mellitus (T2DM) is one of the most prevalent chronic metabolic disorders, and insulin has been placed at the epicentre of its pathophysiological basis. However, the involvement of impaired alpha (α) cell function has been recognized as playing an essential role in several diseases, since hyperglucagonemia has been evidenced in both Type 1 and T2DM. This phenomenon has been attributed to intra-islet defects, like modifications in pancreatic α cell mass or dysfunction in glucagon's secretion. Emerging evidence has shown that chronic hyperglycaemia provokes changes in the Langerhans' islets cytoarchitecture, including α cell hyperplasia, pancreatic beta (ß) cell dedifferentiation into glucagon-positive producing cells, and loss of paracrine and endocrine regulation due to ß cell mass loss. Other abnormalities like α cell insulin resistance, sensor machinery dysfunction, or paradoxical ATP-sensitive potassium channels (KATP) opening have also been linked to glucagon hypersecretion. Recent clinical trials in phases 1 or 2 have shown new molecules with glucagon-antagonist properties with considerable effectiveness and acceptable safety profiles. Glucagon-like peptide-1 (GLP-1) agonists and Dipeptidyl Peptidase-4 inhibitors (DPP-4 inhibitors) have been shown to decrease glucagon secretion in T2DM, and their possible therapeutic role in T1DM means they are attractive as an insulin-adjuvant therapy.


Assuntos
Comunicação Autócrina , Diabetes Mellitus Tipo 1/metabolismo , Diabetes Mellitus Tipo 2/metabolismo , Células Secretoras de Glucagon/metabolismo , Células Secretoras de Insulina/metabolismo , Comunicação Parácrina , Animais , Diabetes Mellitus Tipo 1/tratamento farmacológico , Diabetes Mellitus Tipo 1/patologia , Diabetes Mellitus Tipo 2/tratamento farmacológico , Diabetes Mellitus Tipo 2/patologia , Inibidores da Dipeptidil Peptidase IV/uso terapêutico , Glucagon/metabolismo , Peptídeo 1 Semelhante ao Glucagon/antagonistas & inibidores , Peptídeo 1 Semelhante ao Glucagon/metabolismo , Células Secretoras de Glucagon/patologia , Humanos , Hipoglicemiantes/uso terapêutico , Células Secretoras de Insulina/patologia
2.
Cells ; 10(9)2021 09 21.
Artigo em Inglês | MEDLINE | ID: mdl-34572144

RESUMO

Incretin-potentiated glucose-stimulated insulin secretion (GSIS) is critical to maintaining euglycemia, of which GLP-1 receptor (GLP-1R) on ß-cells plays an indispensable role. Recently, α-cell-derived glucagon but not intestine-derived GLP-1 has been proposed as the critical hormone that potentiates GSIS via GLP-1R. However, the function of glucagon receptors (GCGR) on ß-cells remains elusive. Here, using GCGR or GLP-1R antagonists, in combination with glucagon, to treat single ß-cells, α-ß cell clusters and isolated islets, we found that glucagon potentiates insulin secretion via ß-cell GCGR at physiological but not high concentrations of glucose. Furthermore, we transfected primary mouse ß-cells with RAB-ICUE (a genetically encoded cAMP fluorescence indicator) to monitor cAMP level after glucose stimulation and GCGR activation. Using specific inhibitors of different adenylyl cyclase (AC) family members, we revealed that high glucose concentration or GCGR activation independently evoked cAMP elevation via AC5 in ß-cells, thus high glucose stimulation bypassed GCGR in promoting insulin secretion. Additionally, we generated ß-cell-specific GCGR knockout mice which glucose intolerance was more severe when fed a high-fat diet (HFD). We further found that ß-cell GCGR activation promoted GSIS more than GLP-1R in HFD, indicating the critical role of GCGR in maintaining glucose homeostasis during nutrient overload.


Assuntos
Glucagon/farmacologia , Secreção de Insulina/fisiologia , Receptores de Glucagon/fisiologia , Animais , Glucagon/metabolismo , Peptídeo 1 Semelhante ao Glucagon/metabolismo , Receptor do Peptídeo Semelhante ao Glucagon 1/antagonistas & inibidores , Receptor do Peptídeo Semelhante ao Glucagon 1/metabolismo , Receptor do Peptídeo Semelhante ao Glucagon 1/fisiologia , Glucose/metabolismo , Intolerância à Glucose/metabolismo , Insulina/metabolismo , Secreção de Insulina/efeitos dos fármacos , Células Secretoras de Insulina/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Receptores de Glucagon/antagonistas & inibidores , Transdução de Sinais
3.
Nat Commun ; 12(1): 4818, 2021 08 10.
Artigo em Inglês | MEDLINE | ID: mdl-34376687

RESUMO

The enteroendocrine cell (EEC)-derived incretins play a pivotal role in regulating the secretion of glucagon and insulins in mammals. Although glucagon-like and insulin-like hormones have been found across animal phyla, incretin-like EEC-derived hormones have not yet been characterised in invertebrates. Here, we show that the midgut-derived hormone, neuropeptide F (NPF), acts as the sugar-responsive, incretin-like hormone in the fruit fly, Drosophila melanogaster. Secreted NPF is received by NPF receptor in the corpora cardiaca and in insulin-producing cells. NPF-NPFR signalling resulted in the suppression of the glucagon-like hormone production and the enhancement of the insulin-like peptide secretion, eventually promoting lipid anabolism. Similar to the loss of incretin function in mammals, loss of midgut NPF led to significant metabolic dysfunction, accompanied by lipodystrophy, hyperphagia, and hypoglycaemia. These results suggest that enteroendocrine hormones regulate sugar-dependent metabolism through glucagon-like and insulin-like hormones not only in mammals but also in insects.


Assuntos
Drosophila melanogaster/metabolismo , Células Enteroendócrinas/metabolismo , Glucagon/metabolismo , Hormônios/metabolismo , Insulina/metabolismo , Neuropeptídeos/metabolismo , Animais , Animais Geneticamente Modificados , Drosophila melanogaster/citologia , Drosophila melanogaster/genética , Feminino , Peptídeo 1 Semelhante ao Glucagon/metabolismo , Humanos , Hipoglicemia/genética , Hipoglicemia/metabolismo , Incretinas/metabolismo , Secreção de Insulina , Metabolismo dos Lipídeos/genética , Mutação , Neuropeptídeos/genética , Receptores de Neuropeptídeos/genética , Receptores de Neuropeptídeos/metabolismo , Açúcares/metabolismo
4.
Nat Commun ; 12(1): 5068, 2021 08 20.
Artigo em Inglês | MEDLINE | ID: mdl-34417460

RESUMO

p53 regulates several signaling pathways to maintain the metabolic homeostasis of cells and modulates the cellular response to stress. Deficiency or excess of nutrients causes cellular metabolic stress, and we hypothesized that p53 could be linked to glucose maintenance. We show here that upon starvation hepatic p53 is stabilized by O-GlcNAcylation and plays an essential role in the physiological regulation of glucose homeostasis. More specifically, p53 binds to PCK1 promoter and regulates its transcriptional activation, thereby controlling hepatic glucose production. Mice lacking p53 in the liver show a reduced gluconeogenic response during calorie restriction. Glucagon, adrenaline and glucocorticoids augment protein levels of p53, and administration of these hormones to p53 deficient human hepatocytes and to liver-specific p53 deficient mice fails to increase glucose levels. Moreover, insulin decreases p53 levels, and over-expression of p53 impairs insulin sensitivity. Finally, protein levels of p53, as well as genes responsible of O-GlcNAcylation are elevated in the liver of type 2 diabetic patients and positively correlate with glucose and HOMA-IR. Overall these results indicate that the O-GlcNAcylation of p53 plays an unsuspected key role regulating in vivo glucose homeostasis.


Assuntos
Acetilglucosamina/metabolismo , Glucose/metabolismo , Fígado/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Animais , Sequência de Bases , Restrição Calórica , Linhagem Celular , Colforsina/farmacologia , Diabetes Mellitus Tipo 2/complicações , Diabetes Mellitus Tipo 2/metabolismo , Epinefrina/metabolismo , Glucagon/metabolismo , Glucocorticoides/metabolismo , Gluconeogênese/efeitos dos fármacos , Glicosilação , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Humanos , Hidrocortisona/metabolismo , Hiperglicemia/complicações , Hiperglicemia/metabolismo , Resistência à Insulina , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Fígado/efeitos dos fármacos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Obesidade/complicações , Obesidade/metabolismo , Fosfoenolpiruvato Carboxiquinase (GTP)/metabolismo , Regiões Promotoras Genéticas/genética , Ligação Proteica/efeitos dos fármacos , Estabilidade Proteica/efeitos dos fármacos , Ácido Pirúvico/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Transcrição Genética/efeitos dos fármacos , Proteína Supressora de Tumor p53/genética
5.
Eur J Endocrinol ; 185(4): 565-576, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34374650

RESUMO

Objective: Progressive beta-cell dysfunction is a hallmark of type 2 diabetes (T2D). Increasing evidence indicates that over-stimulating proinsulin synthesis causes proinsulin misfolding and impairs insulin maturation and storage in db/db mice. However, defective insulin maturation in patients with T2D remains unknown. Methods: We examined intra-islet and intra-cellular distributions of proinsulin and insulin and proinsulin to insulin ratio in the islets of patients with T2D. The expression of transcription factor NKX6.1 and dedifferentiation marker ALDH1A3, as well as glucagon, were detected by immunofluorescence. Results: We identified a novel subgroup of beta cells expressing only proinsulin but not insulin. Importantly, significantly increased proinsulin positive and insulin negative (PI+/INS-) cells were evident in T2D, and this increase was strongly correlated with levels of hemoglobin A1C (HbA1c) in T2D and prediabetes. The percentages of beta cells expressing prohormone convertase 1/3 and carboxypeptidase E were not reduced. Indeed, while proinsulin displayed a higher degree of co-localization with the golgi markers GM130/TGN46 in control beta cells, it appeared to be more diffused within the cytoplasm and less co-localized with GM130/TGN46 in PI+/INS- cells. Furthermore, the key functional transcription factor NKX6.1 markedly decreased in the islets of T2D, especially in the cells with PI+/INS-. The decreased NKX6.1+/PI+/INS+ was strongly correlated with levels of HbA1c in T2D. Almost all PI+/INS- cells showed absence of NKX6.1. Moreover, the percentages of PI+/INS- cells expressing ALDH1A3 were elevated along with an increased acquisition of glucagon immunostaining. Conclusion: Our data demonstrate defective insulin maturation in patients with T2D.


Assuntos
Diabetes Mellitus Tipo 2/metabolismo , Proinsulina/metabolismo , Processamento de Proteína Pós-Traducional/fisiologia , Adulto , Aldeído Oxirredutases/metabolismo , Estudos de Casos e Controles , Desdiferenciação Celular/fisiologia , China , Diabetes Mellitus Tipo 2/patologia , Feminino , Glucagon/metabolismo , Proteínas de Homeodomínio/metabolismo , Humanos , Insulina/metabolismo , Células Secretoras de Insulina/metabolismo , Células Secretoras de Insulina/patologia , Células Secretoras de Insulina/fisiologia , Masculino , Pessoa de Meia-Idade , Estado Pré-Diabético/metabolismo , Estado Pré-Diabético/patologia
6.
Nutrients ; 13(7)2021 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-34209449

RESUMO

Interactions between endocrine α and ß cells are critical to their secretory function in vivo. The interactions are highly regulated, although yet to be fully understood. In this study, we aim to assess the impact of α and ß cell co-culture on hormone secretion. Mouse clonal cell lines α-TC6-1 (α cell line) and MIN-6 (ß cell line) were cultured independently or in combination in a medium containing 5.5, 11.1, or 25 mM glucose, respectively. After 72 h, hormone release was measured using insulin and glucagon secretion assays, the cell distribution was visualized by inverted microscopy and an immunocytochemistry assay, and changes in gene expressions were assessed using the RT-PCR technique. The co-culture of the two cell lines caused a decrease in glucagon secretion from α-TC1-6 cells, while no effect on insulin secretion from MIN-6 cells was revealed. Both types of cells were randomly scattered throughout the culture flask, unlike in mice islets in vivo where ß cells cluster in the core and α cells are localized at the periphery. During the α-ß cell co-culture, the gene expression of glucagon (Gcg) decreased significantly. We conclude that islet ß cells suppress glucagon secretion from α cells, apparently via direct cell-to-cell contact, of which the molecular mechanism needs further verification.


Assuntos
Comunicação Celular , Células Secretoras de Glucagon/citologia , Células Secretoras de Glucagon/metabolismo , Glucagon/metabolismo , Células Secretoras de Insulina/citologia , Células Secretoras de Insulina/metabolismo , Animais , Sobrevivência Celular/efeitos dos fármacos , Regulação da Expressão Gênica , Glucose/farmacologia , Secreção de Insulina , Camundongos
7.
Biomolecules ; 11(7)2021 06 23.
Artigo em Inglês | MEDLINE | ID: mdl-34201418

RESUMO

Allosteric modulators have emerged with many potential pharmacological advantages as they do not compete the binding of agonist or antagonist to the orthosteric sites but ultimately affect downstream signaling. To identify allosteric modulators targeting an extra-helical binding site of the glucagon-like peptide-1 receptor (GLP-1R) within the membrane environment, the following two computational approaches were applied: structure-based virtual screening with consideration of lipid contacts and ligand-based virtual screening with the maintenance of specific allosteric pocket residue interactions. Verified by radiolabeled ligand binding and cAMP accumulation experiments, two negative allosteric modulators and seven positive allosteric modulators were discovered using structure-based and ligand-based virtual screening methods, respectively. The computational approach presented here could possibly be used to discover allosteric modulators of other G protein-coupled receptors.


Assuntos
Sistemas de Liberação de Medicamentos/métodos , Descoberta de Drogas/métodos , Receptor do Peptídeo Semelhante ao Glucagon 1/química , Receptor do Peptídeo Semelhante ao Glucagon 1/metabolismo , Sítio Alostérico/efeitos dos fármacos , Sítio Alostérico/fisiologia , Animais , Sítios de Ligação/efeitos dos fármacos , Sítios de Ligação/fisiologia , Células CHO , Cricetinae , Cricetulus , Glucagon/administração & dosagem , Glucagon/química , Glucagon/metabolismo , Humanos , Ligantes , Simulação de Acoplamento Molecular/métodos , Ligação Proteica/efeitos dos fármacos , Ligação Proteica/fisiologia , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína
8.
Am J Physiol Regul Integr Comp Physiol ; 321(3): R303-R316, 2021 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-34259034

RESUMO

Neonatal antibiotics administered to human infants initiate gut microbiota dysbiosis that may have long-term effects on body weight and metabolism. We examined antibiotic-induced adaptations in pancreatic islets of the piglet, a well-accepted model of human infant microbiota and pancreas development. Neonatal piglets randomized to amoxicillin [30 mg/kg body wt/day; n = 7, antibiotic (ANTI)] or placebo [vehicle control; n = 7, control (CON)] from postnatal day (PND)0-13 were euthanized at PND7, 14, and 49. The metabolic phenotype along with functional, immunohistological, and transcriptional phenotypes of the pancreatic islets were studied. The gut microbiome was characterized by 16S rRNA gene sequencing, and microbial metabolites and microbiome-sensitive host molecules were measured. Compared with CON, ANTI PND7 piglets had elevated transcripts of genes involved in glucagon-like peptide 1 ((GLP-1) synthesis or signaling in islets (P < 0.05) coinciding with higher plasma GLP-1 (P = 0.11), along with increased tumor necrosis factor α (Tnf) (P < 0.05) and protegrin 1 (Npg1) (P < 0.05). Antibiotic-induced relative increases in Escherichia, Coprococcus, Ruminococcus, Dehalobacterium, and Oscillospira of the ileal microbiome at PND7 normalized after antibiotic withdrawal. In ANTI islets at PND14, the expression of key regulators pancreatic and duodenal homeobox 1 (Pdx1), insulin-like growth factor-2 (Igf2), and transcription factor 7-like 2 (Tcf7l2) was downregulated, preceding a 40% reduction of ß-cell area (P < 0.01) and islet insulin content at PND49 (P < 0.05). At PND49, a twofold elevated plasma insulin concentration (P = 0.07) was observed in ANTI compared with CON. We conclude that antibiotic treatment of neonatal piglets elicited gut microbial changes accompanied by phasic alterations in key regulatory genes in pancreatic islets at PND7 and 14. By PND49, reduced ß-cell area and islet insulin content were accompanied by elevated nonfasted insulin despite normoglycemia, indicative of islet stress.


Assuntos
Antibacterianos/farmacologia , Microbioma Gastrointestinal/efeitos dos fármacos , Peptídeo 1 Semelhante ao Glucagon/metabolismo , Células Secretoras de Insulina/efeitos dos fármacos , Animais , Microbioma Gastrointestinal/fisiologia , Glucagon/efeitos dos fármacos , Glucagon/metabolismo , Insulina/sangue , Células Secretoras de Insulina/metabolismo , Ilhotas Pancreáticas/efeitos dos fármacos , Ilhotas Pancreáticas/metabolismo , Suínos
9.
Front Immunol ; 12: 633540, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34295325

RESUMO

Sepsis is one of the most common comorbidities observed in diabetic patients, associated with a deficient innate immune response. Recently, we have shown that glucagon possesses anti-inflammatory properties. In this study, we investigated if hyperglucagonemia triggered by diabetes might reduce the migration of neutrophils, increasing sepsis susceptibility. 21 days after diabetes induction by intravenous injection of alloxan, we induced moderate sepsis in Swiss-Webster mice through cecum ligation and puncture (CLP). The glucagon receptor (GcgR) antagonist des-his1-[Glu9]-glucagon amide was injected intraperitoneally 24h and 1h before CLP. We also tested the effect of glucagon on CXCL1/KC-induced neutrophil migration to the peritoneal cavity in mice. Neutrophil chemotaxis in vitro was tested using transwell plates, and the expression of total PKA and phospho-PKA was evaluated by western blot. GcgR antagonist restored neutrophil migration, reduced CFU numbers in the peritoneal cavity and improved survival rate of diabetic mice after CLP procedure, however, the treatment did no alter hyperglycemia, CXCL1/KC plasma levels and blood neutrophilia. In addition, glucagon inhibited CXCL1/KC-induced neutrophil migration to the peritoneal cavity of non-diabetic mice. Glucagon also decreased the chemotaxis of neutrophils triggered by CXCL1/KC, PAF, or fMLP in vitro. The inhibitory action of glucagon occurred in parallel with the reduction of CXCL1/KC-induced actin polymerization in neutrophils in vitro, but not CD11a and CD11b translocation to cell surface. The suppressor effect of glucagon on CXCL1/KC-induced neutrophil chemotaxis in vitro was reversed by pre-treatment with GcgR antagonist and adenylyl cyclase or PKA inhibitors. Glucagon also increased PKA phosphorylation directly in neutrophils in vitro. Furthermore, glucagon impaired zymosan-A-induced ROS production by neutrophils in vitro. Human neutrophil chemotaxis and adherence to endothelial cells in vitro were inhibited by glucagon treatment. According to our results, this inhibition was independent of CD11a and CD11b translocation to neutrophil surface or neutrophil release of CXCL8/IL-8. Altogether, our results suggest that glucagon may be involved in the reduction of neutrophil migration and increased susceptibility to sepsis in diabetic mice. This work collaborates with better understanding of the increased susceptibility and worsening of sepsis in diabetics, which can contribute to the development of new effective therapeutic strategies for diabetic septic patients.


Assuntos
Movimento Celular/efeitos dos fármacos , Diabetes Mellitus Experimental/complicações , Suscetibilidade a Doenças/etiologia , Glucagon/administração & dosagem , Neutrófilos/efeitos dos fármacos , Sepse/etiologia , Sepse/imunologia , Adulto , Animais , Movimento Celular/imunologia , Quimiotaxia de Leucócito/efeitos dos fármacos , Diabetes Mellitus Experimental/imunologia , Diabetes Mellitus Experimental/microbiologia , Feminino , Glucagon/metabolismo , Humanos , Masculino , Camundongos , Camundongos Endogâmicos , Neutrófilos/imunologia
10.
Nat Commun ; 12(1): 3340, 2021 06 07.
Artigo em Inglês | MEDLINE | ID: mdl-34099657

RESUMO

Hepatic gluconeogenesis is essential for glucose homeostasis and also a therapeutic target for type 2 diabetes, but its mechanism is incompletely understood. Here, we report that Sam68, an RNA-binding adaptor protein and Src kinase substrate, is a novel regulator of hepatic gluconeogenesis. Both global and hepatic deletions of Sam68 significantly reduce blood glucose levels and the glucagon-induced expression of gluconeogenic genes. Protein, but not mRNA, levels of CRTC2, a crucial transcriptional regulator of gluconeogenesis, are >50% lower in Sam68-deficient hepatocytes than in wild-type hepatocytes. Sam68 interacts with CRTC2 and reduces CRTC2 ubiquitination. However, truncated mutants of Sam68 that lack the C- (Sam68ΔC) or N-terminal (Sam68ΔN) domains fails to bind CRTC2 or to stabilize CRTC2 protein, respectively, and transgenic Sam68ΔN mice recapitulate the blood-glucose and gluconeogenesis profile of Sam68-deficient mice. Hepatic Sam68 expression is also upregulated in patients with diabetes and in two diabetic mouse models, while hepatocyte-specific Sam68 deficiencies alleviate diabetic hyperglycemia and improves insulin sensitivity in mice. Thus, our results identify a role for Sam68 in hepatic gluconeogenesis, and Sam68 may represent a therapeutic target for diabetes.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Gluconeogênese/fisiologia , Fígado/metabolismo , Proteínas de Ligação a RNA/metabolismo , Fatores de Transcrição/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Animais , Glicemia/metabolismo , Proteínas de Ligação a DNA , Diabetes Mellitus Tipo 2/metabolismo , Regulação da Expressão Gênica , Glucagon/metabolismo , Gluconeogênese/genética , Glucose/metabolismo , Hepatócitos/metabolismo , Homeostase , Humanos , Hiperglicemia , Resistência à Insulina , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas de Ligação a RNA/genética , Fatores de Transcrição/genética , Regulação para Cima
11.
Med Sci Sports Exerc ; 53(7): 1326-1333, 2021 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-34127632

RESUMO

PURPOSE: This study aimed to investigate the influence of residual ß-cell function on counterregulatory hormonal responses to hypoglycemia during acute physical exercise in people with type 1 diabetes (T1D). A secondary aim was to explore relationships between biomarkers of pancreatic ß-cell function and indices of glycemia following acute exercise including the nocturnal period. METHODS: This study involved an exploratory, secondary analysis of data from individuals with T1D who partook in a four-peroid, randomized, cross-over trial involving a bout of evening exercise followed by an overnight stay in a clinical laboratory facility. Participants were split into two groups: (i) a stimulated C-peptide level of ≥30 pmol⋅L-1 (low-level secretors [LLS], n = 6) or (ii) <30 pmol⋅L-1 (microsecretors [MS], n = 10). Pancreatic hormones (C-peptide, proinsulin, and glucagon), catecholamines (epinephrine [EPI] and norepinephrine [NE]), and metabolic biomarkers (blood glucose, blood lactate, and ß-hydroxybutyrate) were measured at rest, during exercise with and without a hypoglycemic (blood glucose ≤3.9 mmol⋅L-1) episode, and throughout a 13-h postexercise period. Interstitial glucose monitoring was used to assess indices of glycemic variability. RESULTS: During in-exercise hypoglycemia, LLS presented with greater sympathoadrenal (EPI and NE P ≤ 0.05) and ketone (P < 0.01) concentrations. Glucagon remained similar (P = 0.09). Over exercise, LLS experienced larger drops in C-peptide and proinsulin (both P < 0.01) as well as greater increases in EPI (P < 0.01) and ß-hydroxybutyrate (P = 0.03). LLS spent less time in the interstitial-derived hypoglycemic range acutely postexercise and had lower glucose variability throughout the nocturnal period. CONCLUSION: Higher residual ß-cell function was associated with greater sympathoadrenal and ketonic responses to exercise-induced hypoglycemia as well as improved glycemia leading into and throughout the nocturnal hours. Even a minimal amount of residual ß-cell function confers a beneficial effect on glycemic outcomes during and after exercise in people with T1D.


Assuntos
Peptídeo C/metabolismo , Diabetes Mellitus Tipo 1/fisiopatologia , Exercício Físico/fisiologia , Hipoglicemia/fisiopatologia , Células Secretoras de Insulina/metabolismo , Adulto , Biomarcadores/sangue , Estudos Cross-Over , Feminino , Glucagon/metabolismo , Humanos , Masculino , Pessoa de Meia-Idade , Adulto Jovem
12.
Compr Physiol ; 11(3): 2191-2225, 2021 06 30.
Artigo em Inglês | MEDLINE | ID: mdl-34190340

RESUMO

Blood glucose homeostasis requires proper function of pancreatic islets, which secrete insulin, glucagon, and somatostatin from the ß-, α-, and δ-cells, respectively. Each islet cell type is equipped with intrinsic mechanisms for glucose sensing and secretory actions, but these intrinsic mechanisms alone cannot explain the observed secretory profiles from intact islets. Regulation of secretion involves interconnected mechanisms among and between islet cell types. Islet cells lose their normal functional signatures and secretory behaviors upon dispersal as compared to intact islets and in vivo. In dispersed islet cells, the glucose response of insulin secretion is attenuated from that seen from whole islets, coordinated oscillations in membrane potential and intracellular Ca2+ activity, as well as the two-phase insulin secretion profile, are missing, and glucagon secretion displays higher basal secretion profile and a reverse glucose-dependent response from that of intact islets. These observations highlight the critical roles of intercellular communication within the pancreatic islet, and how these communication pathways are crucial for proper hormonal and nonhormonal secretion and glucose homeostasis. Further, misregulated secretions of islet secretory products that arise from defective intercellular islet communication are implicated in diabetes. Intercellular communication within the islet environment comprises multiple mechanisms, including electrical synapses from gap junctional coupling, paracrine interactions among neighboring cells, and direct cell-to-cell contacts in the form of juxtacrine signaling. In this article, we describe the various mechanisms that contribute to proper islet function for each islet cell type and how intercellular islet communications are coordinated among the same and different islet cell types. © 2021 American Physiological Society. Compr Physiol 11:2191-2225, 2021.


Assuntos
Glucagon , Ilhotas Pancreáticas , Glucagon/metabolismo , Glucose/metabolismo , Humanos , Insulina/metabolismo , Secreção de Insulina , Ilhotas Pancreáticas/metabolismo
13.
Metabolism ; 122: 154821, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34174327

RESUMO

Optimal metabolic homeostasis requires precise temporal and quantitative control of insulin secretion. Both in vivo and in vitro studies have often focused on the regulation by glucose although many additional factors including other nutrients, neurotransmitters, hormones and drugs, modulate the secretory function of pancreatic ß-cells. This review is based on the analysis of clinical investigations characterizing the effects of non-glucose modulators of insulin secretion in healthy subjects, and of experimental studies testing the same modulators in islets isolated from normal human donors. The aim was to determine whether the information gathered in vitro can reliably be translated to the in vivo situation. The comparison evidenced both convincing similarities and areas of discordance. The lack of coherence generally stems from the use of exceedingly high concentrations of test agents at too high or too low glucose concentrations in vitro, which casts doubts on the physiological relevance of a number of observations made in isolated islets. Future projects resorting to human islets should avoid extreme experimental conditions, such as oversized stimulations or inhibitions of ß-cells, which are unlikely to throw light on normal insulin secretion and contribute to the elucidation of its defects.


Assuntos
Glucose/metabolismo , Secreção de Insulina/fisiologia , Células Secretoras de Insulina/metabolismo , Insulina/metabolismo , Glucagon/metabolismo , Homeostase/fisiologia , Humanos , Células Secretoras de Insulina/fisiologia
14.
Biochemistry ; 60(25): 2033-2043, 2021 06 29.
Artigo em Inglês | MEDLINE | ID: mdl-34124902

RESUMO

The peptide hormone glucagon is prescribed as a pharmaceutical compound to treat diabetic hypoglycemia. However, at the acidic pH where it is highly soluble, glucagon rapidly aggregates into inactive and cytotoxic amyloid fibrils. The recently determined high-resolution structure of these fibrils revealed various stabilizing molecular interactions. On the basis of this structure, we have now designed four arginine mutants of glucagon that resist fibrillization at pharmaceutical concentrations for weeks. An S2R, T29R double mutant and a T29R single mutant remove a hydrogen-bonding interaction in the wild-type fibril, whereas a Y13R, A19R double mutant and a Y13R mutant remove a cation-π interaction. 1H solution nuclear magnetic resonance spectra and ultraviolet absorbance data indicate that these mutants remain soluble in pH 2 buffer under quiescent conditions at concentrations of ≤4 mg/mL for weeks. Under stressed conditions with high salt concentrations and agitation, these mutants fibrillize significantly more slowly than the wild type. The S2R, T29R mutant and the T29R mutant exhibit a mixture of random coil and α-helical conformations, while the Y13R mutant is completely random coil. The mutation sites are chosen to be uninvolved in strong interactions with the glucagon receptor in the active structure of the peptide. Therefore, these arginine mutants of glucagon are promising alternative compounds for treating hypoglycemia.


Assuntos
Proteínas Amiloidogênicas/metabolismo , Glucagon/metabolismo , Hipoglicemiantes/metabolismo , Multimerização Proteica , Proteínas Amiloidogênicas/química , Arginina/química , Dicroísmo Circular , Desenho de Fármacos , Glucagon/química , Temperatura Alta , Hipoglicemiantes/química , Mutação , Ressonância Magnética Nuclear Biomolecular , Conformação Proteica em alfa-Hélice , Engenharia de Proteínas , Multimerização Proteica/efeitos dos fármacos , Cloreto de Sódio/química , Solubilidade
15.
Diabetes Res Clin Pract ; 176: 108846, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-33951481

RESUMO

AIMS: The objective of this study was to compare the islet cell function, insulin sensitivity, and incretin axis between Asian-Indian subjects with either impaired fasting glucose (IFG), or impaired glucose tolerance (IGT), and normal glucose tolerance (NGT). MATERIALS AND METHODS: Prediabetes subjects underwent a mixed meal tolerance test(MMTT) after overnight fasting. Samples for glucose, insulin, glucagon, and glucagon-like peptide-1 (GLP-1) were collected at 0, 30, 60, and 120 min. Insulin secretion sensitivity index -2 (ISSI-2) for beta-cell function and Matsuda index for insulin sensitivity were assessed. Alpha cell function was assessed by measuring the area under the curve (AUC) 0-120 glucagon/AUC0-120 glucose. RESULTS: A total of sixty subjects were recruited with 20 in each group. The beta-cell function represented by ISSI-2 was impaired in prediabetes subjects as compared to NGT group (IFG: 2.09 ± 0.44 vs. NGT: 3.04 ± 0.80, P < 0.0001, and IGT: 2.33 ± 0.59 vs. NGT: 3.04 ± 0.80, P = 0.002). Similarly, AUC0-120 glucagon/AUC0-120 glucose was also lower in prediabetes group as compared to healthy controls (IFG: 0.41(0.54) vs. NGT: 1.07(0.39), P = 0.003 and IGT: 0.57(0.38) vs. NGT: 1.07(0.39), P = 0.001). CONCLUSION: Asian-Indian prediabetes subjects have reduced beta-cell function with lesser glucagon secretion during MMTT as compared to normal healthy controls.


Assuntos
Intolerância à Glucose/metabolismo , Intolerância à Glucose/fisiopatologia , Incretinas/metabolismo , Resistência à Insulina/fisiologia , Células Secretoras de Insulina/fisiologia , Adulto , Idoso , Grupo com Ancestrais do Continente Asiático , Glicemia/metabolismo , Estudos de Casos e Controles , Jejum/sangue , Feminino , Glucagon/metabolismo , Intolerância à Glucose/etnologia , Teste de Tolerância a Glucose , Humanos , Índia/etnologia , Insulina/metabolismo , Resistência à Insulina/etnologia , Secreção de Insulina/fisiologia , Células Secretoras de Insulina/metabolismo , Masculino , Pessoa de Meia-Idade , Estado Pré-Diabético/etnologia , Estado Pré-Diabético/metabolismo , Estado Pré-Diabético/fisiopatologia , Transdução de Sinais/fisiologia
16.
Sci Rep ; 11(1): 11283, 2021 05 28.
Artigo em Inglês | MEDLINE | ID: mdl-34050242

RESUMO

The potential to treat diabetes by increasing beta-cell mass is driving a major effort to identify beta-cell mitogens. Demonstration of mitogen activity in human beta cells is frequently performed in ex vivo assays. However, reported disparities in the efficacy of beta-cell mitogens led us to investigate the sources of this variability. We studied 35 male (23) and female (12) human islet batches covering a range of donor ages and BMI. Islets were kept intact or dispersed into single cells and cultured in the presence of harmine, glucose, or heparin-binding epidermal growth factor-like growth factor (HB-EGF), and subsequently analyzed by immunohistochemistry or flow cytometry. Proliferating cells were identified by double labeling with EdU and Ki67 and glucagon, c-peptide or Nkx6.1, and cytokeratin-19 to respectively label alpha, beta, and ductal cells. Harmine and HB-EGF stimulated human beta-cell proliferation, but the effect of glucose was dependent on the assay and the donor. Harmine potently stimulated alpha-cell proliferation and both harmine and HB-EGF increased proliferation of insulin- and glucagon-negative cells, including cytokeratin 19-positive cells. Given the abundance of non-beta cells in human islet preparations, our results suggest that assessment of beta-cell mitogens requires complementary approaches and rigorous identification of cell identity using multiple markers.


Assuntos
Células Secretoras de Insulina/metabolismo , Ilhotas Pancreáticas/metabolismo , Mitógenos/farmacologia , Peptídeo C/metabolismo , Divisão Celular , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/fisiologia , Fator de Crescimento Epidérmico/metabolismo , Feminino , Glucagon/metabolismo , Glucose/metabolismo , Harmina/farmacologia , Fator de Crescimento Semelhante a EGF de Ligação à Heparina/metabolismo , Fator de Crescimento Semelhante a EGF de Ligação à Heparina/farmacologia , Humanos , Insulina/metabolismo , Células Secretoras de Insulina/fisiologia , Ilhotas Pancreáticas/fisiologia , Masculino , Mitógenos/imunologia , Mitógenos/metabolismo , Ductos Pancreáticos/metabolismo , Cultura Primária de Células , Transdução de Sinais/efeitos dos fármacos
17.
Sci Rep ; 11(1): 11129, 2021 05 27.
Artigo em Inglês | MEDLINE | ID: mdl-34045505

RESUMO

Diabetes is a metabolic syndrome rooted in impaired insulin and/or glucagon secretory responses within the pancreatic islets of Langerhans (islets). Insulin secretion is primarily regulated by two key factors: glucose-mediated ATP production and G-protein coupled receptors (GPCRs) signaling. GPCR kinase 2 (GRK2), a key regulator of GPCRs, is reported to be downregulated in the pancreas of spontaneously obesogenic and diabetogenic mice (ob/ob). Moreover, recent studies have shown that GRK2 non-canonically localizes to the cardiac mitochondrion, where it can contribute to glucose metabolism. Thus, islet GRK2 may impact insulin secretion through either mechanism. Utilizing Min6 cells, a pancreatic ß-cell model, we knocked down GRK2 and measured glucose-mediated intracellular calcium responses and insulin secretion. Silencing of GRK2 attenuated calcium responses, which were rescued by pertussis toxin pre-treatment, suggesting a Gαi/o-dependent mechanism. Pancreatic deletion of GRK2 in mice resulted in glucose intolerance with diminished insulin secretion. These differences were due to diminished insulin release rather than decreased insulin content or gross differences in islet architecture. Furthermore, a high fat diet feeding regimen exacerbated the metabolic phenotype in this model. These results suggest a new role for pancreatic islet GRK2 in glucose-mediated insulin responses that is relevant to type 2 diabetes disease progression.


Assuntos
Cálcio/metabolismo , Quinase 2 de Receptor Acoplado a Proteína G/metabolismo , Intolerância à Glucose/metabolismo , Glucose/metabolismo , Secreção de Insulina/fisiologia , Células Secretoras de Insulina/metabolismo , Animais , Linhagem Celular , AMP Cíclico , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/metabolismo , Dieta Hiperlipídica , Regulação para Baixo , Quinase 2 de Receptor Acoplado a Proteína G/genética , Glucagon/metabolismo , Intolerância à Glucose/genética , Teste de Tolerância a Glucose , Ilhotas Pancreáticas/metabolismo , Peroxidação de Lipídeos/fisiologia , Camundongos , Camundongos Knockout , Obesidade/genética , Obesidade/metabolismo
18.
J Biol Chem ; 296: 100646, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33839150

RESUMO

Dysregulated glucagon secretion deteriorates glycemic control in type 1 and type 2 diabetes. Although insulin is known to regulate glucagon secretion via its cognate receptor (insulin receptor, INSR) in pancreatic alpha cells, the role of downstream proteins and signaling pathways underlying insulin's activities are not fully defined. Using in vivo (knockout) and in vitro (knockdown) studies targeting insulin receptor substrate (IRS) proteins, we compared the relative roles of IRS1 and IRS2 in regulating alpha cell function. Alpha cell-specific IRS1-knockout mice exhibited glucose intolerance and inappropriate glucagon suppression during glucose tolerance tests. In contrast, alpha cell-specific IRS2-knockout animals manifested normal glucose tolerance and suppression of glucagon secretion after glucose administration. Alpha cell lines with stable IRS1 knockdown could not repress glucagon mRNA expression and exhibited a reduction in phosphorylation of AKT Ser/Thr kinase (AKT, at Ser-473 and Thr-308). AlphaIRS1KD cells also displayed suppressed global protein translation, including reduced glucagon expression, impaired cytoplasmic Ca2+ response, and mitochondrial dysfunction. This was supported by the identification of novel IRS1-specific downstream target genes, Trpc3 and Cartpt, that are associated with glucagon regulation in alpha cells. These results provide evidence that IRS1, rather than IRS2, is a dominant regulator of pancreatic alpha cell function.


Assuntos
Células Secretoras de Glucagon/patologia , Glucagon/metabolismo , Intolerância à Glucose/patologia , Proteínas Substratos do Receptor de Insulina/fisiologia , Resistência à Insulina , Animais , Feminino , Células Secretoras de Glucagon/metabolismo , Intolerância à Glucose/etiologia , Intolerância à Glucose/metabolismo , Masculino , Camundongos , Camundongos Knockout , Fosforilação , Transdução de Sinais
19.
Diabetes ; 70(7): 1443-1457, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33883213

RESUMO

The counterregulatory response to hypoglycemia is an essential survival function. It is controlled by an integrated network of glucose-responsive neurons, which trigger endogenous glucose production to restore normoglycemia. The complexity of this glucoregulatory network is, however, only partly characterized. In a genetic screen of a panel of recombinant inbred mice we previously identified Fgf15, expressed in neurons of the dorsomedial hypothalamus (DMH), as a negative regulator of glucagon secretion. Here, we report on the generation of Fgf15CretdTomato mice and their use to further characterize these neurons. We show that they were glutamatergic and comprised glucose-inhibited and glucose-excited neurons. When activated by chemogenetics, Fgf15 neurons prevented the increase in vagal nerve firing and the secretion of glucagon normally triggered by insulin-induced hypoglycemia. On the other hand, they increased the activity of the sympathetic nerve in the basal state and prevented its silencing by glucose overload. Higher sympathetic tone increased hepatic Creb1 phosphorylation, Pck1 mRNA expression, and hepatic glucose production leading to glucose intolerance. Thus, Fgf15 neurons of the DMH participate in the counterregulatory response to hypoglycemia by a direct adrenergic stimulation of hepatic glucose production while suppressing vagally induced glucagon secretion. This study provides new insights into the complex neuronal network that prevents the development of hypoglycemia.


Assuntos
Fatores de Crescimento de Fibroblastos/fisiologia , Glucagon/metabolismo , Gluconeogênese/fisiologia , Hipotálamo/metabolismo , Fígado/metabolismo , Neurônios/fisiologia , Animais , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/fisiologia , Feminino , Hipoglicemia/prevenção & controle , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Sistema Nervoso Simpático/fisiologia
20.
Cells ; 10(4)2021 04 14.
Artigo em Inglês | MEDLINE | ID: mdl-33919776

RESUMO

Glucose metabolism plays a crucial role in modulating glucagon secretion in pancreatic alpha cells. However, the downstream effects of glucose metabolism and the activated signaling pathways influencing glucagon granule exocytosis are still obscure. We developed a computational alpha cell model, implementing metabolic pathways of glucose and free fatty acids (FFA) catabolism and an intrinsically activated cAMP signaling pathway. According to the model predictions, increased catabolic activity is able to suppress the cAMP signaling pathway, reducing exocytosis in a Ca2+-dependent and Ca2+ independent manner. The effect is synergistic to the pathway involving ATP-dependent closure of KATP channels and consequent reduction of Ca2+. We analyze the contribution of each pathway to glucagon secretion and show that both play decisive roles, providing a kind of "secure double switch". The cAMP-driven signaling switch plays a dominant role, while the ATP-driven metabolic switch is less favored. The ratio is approximately 60:40, according to the most recent experimental evidence.


Assuntos
AMP Cíclico/metabolismo , Glucagon/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Células Secretoras de Glucagon/metabolismo , Glucose/metabolismo , Humanos , Ácido Láctico/metabolismo , Metaboloma , Modelos Biológicos , Transdução de Sinais
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