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1.
Adv Exp Med Biol ; 1131: 943-963, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31646540

RESUMO

Insulin secretion in humans is usually induced by mixed meals, which upon ingestion, increase the plasma concentration of glucose, fatty acids, amino acids, and incretins like glucagon-like peptide 1. Beta-cells can stay in the off-mode, ready-mode or on-mode; the mode-switching being determined by the open state probability of the ATP-sensitive potassium channels, and the activity of enzymes like glucokinase, and glutamate dehydrogenase. Mitochondrial metabolism is critical for insulin secretion. A sound understanding of the intermediary metabolism, electrophysiology, and cell signaling is essential for comprehension of the entire spectrum of the stimulus-secretion coupling. Depolarization brought about by inhibition of the ATP sensitive potassium channel, together with the inward depolarizing currents through the transient receptor potential (TRP) channels, leads to electrical activities, opening of the voltage-gated calcium channels, and exocytosis of insulin. Calcium- and cAMP-signaling elicited by depolarization, and activation of G-protein-coupled receptors, including the free fatty acid receptors, are intricately connected in the form of networks at different levels. Activation of the glucagon-like peptide 1 receptor augments insulin secretion by amplifying calcium signals by calcium induced calcium release (CICR). In the treatment of type 2 diabetes, use of the sulfonylureas that act on the ATP sensitive potassium channel, damages the beta cells, which eventually fail; these drugs do not improve the cardiovascular outcomes. In contrast, drugs acting through the glucagon-like peptide-1 receptor protect the beta-cells, and improve cardiovascular outcomes. The use of the glucagon-like peptide 1 receptor agonists is increasing and that of sulfonylurea is decreasing. A better understanding of the stimulus-secretion coupling may lead to the discovery of other molecular targets for development of drugs for the prevention and treatment of type 2 diabetes.


Assuntos
Diabetes Mellitus Tipo 2 , Células Secretoras de Insulina , Cálcio/metabolismo , Diabetes Mellitus Tipo 2/fisiopatologia , Glucose , Humanos , Insulina , Células Secretoras de Insulina/enzimologia , Células Secretoras de Insulina/patologia
2.
Ecotoxicol Environ Saf ; 188: 109875, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31706244

RESUMO

Previous works showed that chronic exposure to Aroclor 1254 disrupted glucose homeostasis and induced insulin resistance in male mice. To further observe the different effects of Aroclor 1254 exposure on the pancreatic α-cells and ß-cells, male mice were exposed to Aroclor 1254 (0, 0.5, 5, 50, 500 µg/kg) for 60 days, the pancreas was performed a histological examination. The results showed that the percentage of apoptosis cell (indicated by TUNEL assay) was increased in both α-cells and ß-cells, as the Aroclor 1254 dose was increased; the proliferation (indicated by PCNA expression) rate of ß-cells was elevated while that of α-cells was not affected, resulting in an increased ß-cell mass and a decreased α-cell mass in a dose-depend manner. The number of Pdx-1 positive ß-cells was significantly increased whereas that of Arx positive α-cells was markedly decreased, indicating an enhanced ß-cell neogenesis and a weakened α-cell neogenesis. The drastically reduction of serum testosterone levels in all the treatments suggested an anti-androgenic potency of Aroclor 1254. The up-regulation of estrogen receptors (ERα and ERß) and androgen receptor in ß-cells might be responsible for the increased ß-cell mass and neogenesis.


Assuntos
Antitireóideos/toxicidade , Células Secretoras de Glucagon/efeitos dos fármacos , Células Secretoras de Insulina/efeitos dos fármacos , Animais , Apoptose/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Células Secretoras de Glucagon/metabolismo , Células Secretoras de Glucagon/patologia , Proteínas de Homeodomínio/metabolismo , Células Secretoras de Insulina/metabolismo , Células Secretoras de Insulina/patologia , Masculino , Camundongos , Receptores Androgênicos/metabolismo , Receptores Estrogênicos/metabolismo , Testosterona/sangue , Transativadores/metabolismo , Fatores de Transcrição/metabolismo
3.
Nat Genet ; 51(11): 1588-1595, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31676868

RESUMO

The early stages of type 1 diabetes (T1D) are characterized by local autoimmune inflammation and progressive loss of insulin-producing pancreatic ß cells. Here we show that exposure to proinflammatory cytokines reveals a marked plasticity of the ß-cell regulatory landscape. We expand the repertoire of human islet regulatory elements by mapping stimulus-responsive enhancers linked to changes in the ß-cell transcriptome, proteome and three-dimensional chromatin structure. Our data indicate that the ß-cell response to cytokines is mediated by the induction of new regulatory regions as well as the activation of primed regulatory elements prebound by islet-specific transcription factors. We find that T1D-associated loci are enriched with newly mapped cis-regulatory regions and identify T1D-associated variants disrupting cytokine-responsive enhancer activity in human ß cells. Our study illustrates how ß cells respond to a proinflammatory environment and implicate a role for stimulus response islet enhancers in T1D.


Assuntos
Cromatina/genética , Citocinas/farmacologia , Diabetes Mellitus Tipo 1/genética , Regulação da Expressão Gênica/efeitos dos fármacos , Redes Reguladoras de Genes , Células Secretoras de Insulina/metabolismo , Transcriptoma , Cromatina/química , Diabetes Mellitus Tipo 1/tratamento farmacológico , Diabetes Mellitus Tipo 1/patologia , Elementos Facilitadores Genéticos , Estudo de Associação Genômica Ampla , Humanos , Células Secretoras de Insulina/efeitos dos fármacos , Células Secretoras de Insulina/patologia , Fatores de Transcrição
4.
Nat Med ; 25(11): 1739-1747, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31700183

RESUMO

Type 2 diabetes is characterized by insulin resistance and a gradual loss of pancreatic beta cell mass and function1,2. Currently, there are no therapies proven to prevent beta cell loss and some, namely insulin secretagogues, have been linked to accelerated beta cell failure, thereby limiting their use in type 2 diabetes3,4. The adipokine adipsin/complement factor D controls the alternative complement pathway and generation of complement component C3a, which acts to augment beta cell insulin secretion5. In contrast to other insulin secretagogues, we show that chronic replenishment of adipsin in diabetic db/db mice ameliorates hyperglycemia and increases insulin levels while preserving beta cells by blocking dedifferentiation and death. Mechanistically, we find that adipsin/C3a decreases the phosphatase Dusp26; forced expression of Dusp26 in beta cells decreases expression of core beta cell identity genes and sensitizes to cell death. In contrast, pharmacological inhibition of DUSP26 improves hyperglycemia in diabetic mice and protects human islet cells from cell death. Pertaining to human health, we show that higher concentrations of circulating adipsin are associated with a significantly lower risk of developing future diabetes among middle-aged adults after adjusting for body mass index (BMI). Collectively, these data suggest that adipsin/C3a and DUSP26-directed therapies may represent a novel approach to achieve beta cell health to treat and prevent type 2 diabetes.


Assuntos
Complemento C3a/genética , Fator D do Complemento/farmacologia , Diabetes Mellitus Tipo 2/tratamento farmacológico , Fosfatases de Especificidade Dupla/genética , Células Secretoras de Insulina/efeitos dos fármacos , Fosfatases da Proteína Quinase Ativada por Mitógeno/genética , Animais , Índice de Massa Corporal , Desdiferenciação Celular/efeitos dos fármacos , Fator D do Complemento/genética , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/patologia , Glucose/metabolismo , Humanos , Hiperglicemia/tratamento farmacológico , Hiperglicemia/genética , Hiperglicemia/patologia , Insulina/genética , Resistência à Insulina/genética , Células Secretoras de Insulina/patologia , Camundongos , Camundongos Endogâmicos NOD
5.
Int J Mol Sci ; 20(18)2019 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-31505737

RESUMO

Hyperglycemia is the major characteristic of diabetes mellitus, and a chronically high glucose (HG) level causes ß-cell glucolipotoxicity, which is characterized by lipid accumulation, impaired ß-cell function, and apoptosis. TXNIP (Thioredoxin-interacting protein) is a key mediator of diabetic ß-cell apoptosis and dysfunction in diabetes, and thus, its regulation represents a therapeutic target. Recent studies have reported that p90RSK is implicated in the pathogenesis of diabetic cardiomyopathy and nephropathy. In this study, we used FMK (a p90RSK inhibitor) to determine whether inhibition of p90RSK protects ß-cells from chronic HG-induced TXNIP expression and to investigate the molecular mechanisms underlying the effect of FMK on its expression. In INS-1 pancreatic ß-cells, HG-induced ß-cell dysfunction, apoptosis, and ROS generation were significantly diminished by FMK. In contrast BI-D1870 (another p90RSK inhibitor) did not attenuate HG-induced TXNIP promoter activity or TXNIP expression. In addition, HG-induced nuclear translocation of ChREBP and its transcriptional target molecules were found to be regulated by FMK. These results demonstrate that HG-induced pancreatic ß-cell dysfunction resulting in HG conditions is associated with TXNIP expression, and that FMK is responsible for HG-stimulated TXNIP gene expression by inactivating the regulation of ChREBP in pancreatic ß-cells. Taken together, these findings suggest FMK may protect against HG-induced ß-cell dysfunction and TXNIP expression by ChREBP regulation in pancreatic ß-cells, and that FMK is a potential therapeutic reagent for the drug development of diabetes and its complications.


Assuntos
Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/metabolismo , Proteínas de Ciclo Celular/biossíntese , Regulação da Expressão Gênica/efeitos dos fármacos , Glucose/farmacologia , Células Secretoras de Insulina/metabolismo , Inibidores de Proteínas Quinases/farmacologia , Proteínas Quinases S6 Ribossômicas 90-kDa/antagonistas & inibidores , Animais , Linhagem Celular Tumoral , Diabetes Mellitus/tratamento farmacológico , Diabetes Mellitus/metabolismo , Diabetes Mellitus/patologia , Células Secretoras de Insulina/patologia , Ratos , Proteínas Quinases S6 Ribossômicas 90-kDa/metabolismo
6.
Life Sci ; 233: 116704, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31369761

RESUMO

AIMS: Doxorubicin, an anticancer drug, has a toxic effect on many tissues such as heart, pancreas, liver, kidney, and testis. The aim of current study is to investigate whether melatonin would be protective in doxorubicin-induced beta (ß) cell toxicity via HMGB1/TLR2/TLR4/MAPK/NF-қB signaling pathway. MAIN METHODS: Human pancreatic ß cell (1.1B4) was used in the present study. Four experimental groups were created as control, melatonin (10 µM), doxorubicin (2 µM) and the combination of melatonin with doxorubicin. Following 24-h treatment, Mitogen-activated protein kinase (MAPKs), Toll like receptors (TLRs) including TLR2 and TLR4, pro-and anti-apoptotic protein expression levels were determined by western blotting. Total antioxidant (TAS), oxidant status (TOS) and oxidative stress index (OSI) of the cells as well as superoxide dismutase (SOD) levels were determined. Active caspase-8 activity was measured and TUNEL staining was performed to study apoptotic pathways. Mitochondrial membrane potential (MMP), some protein expressions and F-actin distribution were analyzed. KEY FINDINGS: Doxorubicin caused to depolarize MMP, resulting in enhancing apoptosis by activation of caspase-8 via MAPKs/NF-кB pathway via elevation of TOS and decreasing TAS. Also, doxorubicin destroyed F-actin distribution and elevated TLR2 and some apoptotic proteins, including Bax. However, co-treatment of melatonin with doxorubicin could reverse depolarization of MMP and inhibition of apoptosis through MAPK/NF-кB signaling by decreasing TOS and increasing TAS. The co-treatment reversed the alternations of TLR2, TLR4, MAPKs and apoptotic protein expressions induced by doxorubicin. SIGNIFICANCE: Melatonin could be a good candidate against pancreatic ß cell toxicity-induced by doxorubicin through TLR2/TLR4/MAPK/NF-кB pathways.


Assuntos
Doxorrubicina/efeitos adversos , Células Secretoras de Insulina/efeitos dos fármacos , Melatonina/farmacologia , Substâncias Protetoras/farmacologia , Receptor 2 Toll-Like/metabolismo , Receptor 4 Toll-Like/metabolismo , Antibióticos Antineoplásicos/efeitos adversos , Antioxidantes/farmacologia , Apoptose/efeitos dos fármacos , Células Cultivadas , Proteína HMGB1/metabolismo , Humanos , Células Secretoras de Insulina/metabolismo , Células Secretoras de Insulina/patologia , Potencial da Membrana Mitocondrial/efeitos dos fármacos , NF-kappa B/metabolismo , Oxidantes/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Receptor 2 Toll-Like/genética , Receptor 4 Toll-Like/genética , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo
7.
BMC Endocr Disord ; 19(1): 85, 2019 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-31382941

RESUMO

BACKGROUND: Older patients with type 2 diabetes mellitus represent a heterogeneous group in terms of metabolic profile. It makes glucose-lowering-therapy (GLT) complex to manage, as it needs to be individualised according to the patient profile. This study aimed to identify and characterize subgroups existing among older patients with diabetes. METHODS: Retrospective observational cohort study of outpatients followed in a Belgian diabetes clinic. Included participants were all aged ≥75 years, diagnosed with type 2 diabetes, Caucasian, and had a Homeostasis Model Assessment (HOMA2). A latent profile analysis was conducted to classify patients using the age at diabetes diagnosis and HOMA2 variables, i.e. insulin sensitivity (HOMA2%-S), beta-cell-function (HOMA2%-ß), and the product between both (HOMA2%-ßxS; as a measure of residual beta-cell function). GLT was expressed in defined daily dose (DDD). RESULTS: In total, 147 patients were included (median age: 80 years; 37.4% women; median age at diabetes diagnostic: 62 years). The resulting model classified patients into 6 distinct cardiometabolic profiles. Patients in profiles 1 and 2 had an older age at diabetes diagnosis (median: 68 years) and a lesser decrease in HOMA2%-S, as compared to other profiles. They also presented with the highest HOMA2%-ßxS values. Patients in profiles 3, 4 and 5 had a moderate decrease in HOMA2%-ßxS. Patients in profile 6 had the largest decrease in HOMA2%-ß and HOMA2%-ßxS. This classification was associated with significant differences in terms of HbA1c values and GLT total DDD between profiles. Thus, patients in profiles 1 and 2 presented with the lowest HbA1c values (median: 6.5%) though they received the lightest GLT (median GLT DDD: 0.75). Patients in profiles 3 to 5 presented with intermediate values of HbA1c (median: 7.3% and GLT DDD (median: 1.31). Finally, patients in profile 6 had the highest HbA1c values (median: 8.4%) despite receiving the highest GLT DDD (median: 2.28). Other metabolic differences were found between profiles. CONCLUSIONS: This study identified 6 groups among patients ≥75 years with type 2 diabetes by latent profile analysis, based on age at diabetes diagnosis, insulin sensitivity, absolute and residual ß-cell function. Intensity and choice of GLT should be adapted on this basis in addition to other existing recommendations for treatment individualisation.


Assuntos
Biomarcadores/análise , Índice de Massa Corporal , Doenças Cardiovasculares/diagnóstico , Diabetes Mellitus Tipo 2/complicações , Resistência à Insulina , Células Secretoras de Insulina/patologia , Doenças Metabólicas/diagnóstico , Idoso , Idoso de 80 Anos ou mais , Glicemia/análise , Doenças Cardiovasculares/etiologia , Doenças Cardiovasculares/metabolismo , Diagnóstico Diferencial , Feminino , Seguimentos , Hemoglobina A Glicada/análise , Humanos , Incidência , Masculino , Doenças Metabólicas/etiologia , Doenças Metabólicas/metabolismo , Prognóstico , Estudos Retrospectivos
8.
Mol Med Rep ; 20(2): 2030-2038, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31257494

RESUMO

Neuropeptide B (NPB) regulates food intake, body weight and energy homeostasis by interacting with NPBW1/NPBW2 in humans and NPBW1 in rodents. NPB and NPBW1 are widely expressed in the central nervous system and peripheral tissues including pancreatic islets. Although previous studies have demonstrated a prominent role for NPB and NPBW1 in controlling glucose and energy homeostasis, it remains unknown as to whether NPB modulates pancreatic ß­cell functions. Therefore, the aim of the present study was to investigate the effects of NPB on insulin expression and secretion in vitro. Furthermore, the role of NPB in the modulation of INS­1E cell growth, viability and death was examined. Gene expression was assessed by reverse transcription­quantitative PCR. Cell proliferation and viability were determined by BrdU or MTT tests, respectively. Apoptotic cell death was evaluated by relative quantification histone­complexed DNA fragments (mono­and oligonucleosomes). Insulin secretion was studied using an ELISA test. Protein phosphorylation was assessed by western blot analysis. NPB and NPBW1 mRNA was expressed in INS­1E cells and rat pancreatic islets. In INS­1E cells, NPB enhanced insulin 1 mRNA expression via an ERK1/2­dependent mechanism. Furthermore, NPB stimulated insulin secretion from INS­1E cells and rat pancreatic islets. By contrast, NPB failed to affect INS­1E cell growth or death. We conclude that NPB may regulate insulin secretion and expression in INS­1E cells and insulin secretion in rat pancreatic islets.


Assuntos
Células Secretoras de Insulina/metabolismo , Insulina/biossíntese , Neuropeptídeos/genética , Receptores de Neuropeptídeos/genética , Animais , Proliferação de Células/genética , Glucose/metabolismo , Humanos , Insulina/genética , Secreção de Insulina/genética , Células Secretoras de Insulina/patologia , Ilhotas Pancreáticas/metabolismo , Neuropeptídeos/metabolismo , Fosforilação , RNA Mensageiro/genética , Ratos
9.
Eur J Pharmacol ; 860: 172569, 2019 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-31351037

RESUMO

Type 1 diabetes mellitus (DM) remains an intractable disease with a limited number of therapeutic options. Recently, some studies have reported the role of inflammation in DM-induced ß-cell destruction. Nilotinib hydrochloride, a tyrosine kinase inhibitor is a well-known anticancer with numerous medical benefits. In the present study, DM was induced by single I.P. injection of streptozotocin (STZ) (50 mg/kg). Daily oral nilotinib (10 mg/kg) and (20 mg/kg) for 4 weeks induced a significant attenuation of DM signs in rats and their assessed lab values. Nilotinib induced a dose-dependent significant escalation in serum insulin level with a significant reduction in blood glucose and glucagon levels. Nevertheless, biomarkers of cell injury, tissue necrosis, and apoptosis; caspase-3 were significantly reduced. Moreover, pancreatic antioxidants defenses of which; thioredoxin, superoxide dismutase (SOD) and catalase activities, reduced glutathione (GSH) concentration, and total antioxidant capacity significantly improved with a simultaneous reduction in malondialdehyde (MDA) content. Histopathologically, nilotinib treatment was associated with a minimal pancreatic injury with a significant restoration of insulin content in ß-islets. In addition, nilotinib treatment revealed a significant reduction in infiltration of macrophages in ß-cells. In conclusion: nilotinib's ameliorative impact on DM may be attributed to both nilotinib's mediated protection and preservation of pancreatic ß islets function and the improvement in serum insulin levels and hence the improvement of blood glucose.


Assuntos
Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Experimental/patologia , Células Secretoras de Insulina/metabolismo , Células Secretoras de Insulina/patologia , Pirimidinas/farmacologia , Animais , Antígenos CD/metabolismo , Antígenos de Diferenciação Mielomonocítica/metabolismo , Apoptose/efeitos dos fármacos , Glicemia/metabolismo , Peso Corporal/efeitos dos fármacos , Caspase 3/metabolismo , Catalase/metabolismo , Diabetes Mellitus Experimental/sangue , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Glucagon/sangue , Glutationa/metabolismo , Insulina/metabolismo , Células Secretoras de Insulina/efeitos dos fármacos , Masculino , Malondialdeído/metabolismo , Tamanho do Órgão/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Superóxido Dismutase/metabolismo
10.
Diabetes Metab Syndr ; 13(3): 2094-2096, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31235142

RESUMO

Insulin resistance (IR) and ß-cell dysfunction are key pathological features of type 2 diabetes mellitus, the aim of this study was to investigate the role of proinsulin level and proinsulin/insulin ratio in early prediction of beta cell dysfunction and insulin resistance in obese Egyptian adolescent. PATIENTS AND METHODS: This Case control study was conducted from June 2017 to March 2018. Total of 60 patients were divided into 2 groups after exclusion of patients with diabetes: normal body weight group and Obese group. Demographic, clinical data were collected. Laboratory investigation included fasting insulin, proinsulin, and estimation of HOMA IR and HOMA-B were done. RESULTS: There are highly statistically significant increase in obese group regarding insulin, proinsulin, proinsulin/insulin ratio and HOMA-IR while there is significant decrease in HOMA-B in this group. The best cutoff value of Proinsulin in prediction of beta cell function was ≥7.829 pmol/L with sensitivity 95.8, specificity 72.2. The best cutoff value of Proinsulin/insulin ratio in prediction of insulin resistance was ≥0.1545 with sensitivity 87.5, specificity 61.1. CONCLUSION: both beta cell dysfunction and insulin resistance increased in obese group and so increased risk of type 2 diabetes. We found that Pro insulin/insulin ratio is a significant predictor for insulin resistance and Proinsulin is good predictor for beta cell dysfunction.


Assuntos
Biomarcadores/sangue , Peso Corporal , Resistência à Insulina , Células Secretoras de Insulina/patologia , Insulina/sangue , Obesidade/fisiopatologia , Proinsulina/sangue , Adulto , Estudos de Casos e Controles , Egito/epidemiologia , Jejum , Feminino , Seguimentos , Humanos , Células Secretoras de Insulina/metabolismo , Masculino , Pessoa de Meia-Idade , Obesidade/epidemiologia , Prognóstico
11.
J Diabetes Res ; 2019: 9536032, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31179344

RESUMO

Thyrotropin (TSH) is a modulator of glucose metabolism by binding to its receptor on pancreatic cells. We used thyrotropin receptor (TSHR) knockout mice (Tshr -/-) as a model of TSH deletion to study its function in pancreatic ß cells. Tshr -/- mice had a similar body weight at birth compared with Tshr +/+ mice, but grew at a significantly slower rate until adulthood with adequate thyroxine supplementation. TSH deletion led to lower fasting and postprandial blood glucose, insulin secretion impairment, and atrophy of islets in adult mice. Transcription factors and markers of pancreatic ß cell maturation, Pdx1, Nkx6.1, Glut2, and insulin, together with cell proliferation marker Ki67 showed no differences at the mRNA level between the two groups. However, the Bax/Bcl-2 ratio was remarkably elevated in Tshr -/- mice at both mRNA and protein levels. We hypothesized that pancreatic cell apoptosis, rather than abnormal cell proliferation and maturation, is associated with pancreatic dysfunction and glucose intolerance in the absence of TSH modulation.


Assuntos
Células Secretoras de Insulina/patologia , Tireotropina/fisiologia , Animais , Apoptose , Peso Corporal , Proliferação de Células , Feminino , Deleção de Genes , Perfilação da Expressão Gênica , Glucose/metabolismo , Teste de Tolerância a Glucose , Transportador de Glucose Tipo 2/metabolismo , Heterozigoto , Proteínas de Homeodomínio/metabolismo , Homeostase , Insulina/metabolismo , Masculino , Camundongos , Camundongos Knockout , Tamanho do Órgão , Pâncreas/fisiopatologia , Receptores da Tireotropina/genética , Tiroxina/uso terapêutico , Transativadores/metabolismo
12.
Mol Cell Biochem ; 460(1-2): 81-92, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31183735

RESUMO

High levels of circulating free fatty acids often trigger pancreatic ß cell dysfunction during the development of type 2 diabetes. Silibinin, the main component of Silybum marianum fruit extract (silymarin), is reported to have anti-diabetic effect. This study is designed to determine the protective effect of silibinin on palmitic acid-induced damage in a rat pancreatic ß-cell line, INS-1 cells. Our results demonstrate that silibinin improves cell viability, enhances insulin synthesis and secretion, and resumes normal mitochondrial function in palmitic acid-treated INS-1 cells. An accumulating body of evidence has shown that the estrogen receptors are key molecules involved in glucose and lipid metabolism. Our results suggest that silibinin upregulates ERα signaling pathway from the finding that ERα-specific inhibitors abolish the anti-lipotoxic effect of silibinin. In conclusion, these findings suggest that silibinin protects INS-1 cells against apoptosis and mitochondrial damage through upregulation of ERα pathway.


Assuntos
Apoptose/efeitos dos fármacos , Receptor alfa de Estrogênio/metabolismo , Células Secretoras de Insulina/metabolismo , Células Secretoras de Insulina/patologia , Mitocôndrias/patologia , Ácido Palmítico/toxicidade , Silibina/farmacologia , Animais , Linhagem Celular Tumoral , Citoproteção/efeitos dos fármacos , Células Secretoras de Insulina/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Substâncias Protetoras/farmacologia , Ratos , Silibina/química , Regulação para Cima/efeitos dos fármacos
13.
Nat Commun ; 10(1): 2679, 2019 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-31213603

RESUMO

The islet in type 2 diabetes (T2D) is characterized by amyloid deposits derived from islet amyloid polypeptide (IAPP), a protein co-expressed with insulin by ß-cells. In common with amyloidogenic proteins implicated in neurodegeneration, human IAPP (hIAPP) forms membrane permeant toxic oligomers implicated in misfolded protein stress. Here, we establish that hIAPP misfolded protein stress activates HIF1α/PFKFB3 signaling, this increases glycolysis disengaged from oxidative phosphorylation with mitochondrial fragmentation and perinuclear clustering, considered a protective posture against increased cytosolic Ca2+ characteristic of toxic oligomer stress. In contrast to tissues with the capacity to regenerate, ß-cells in adult humans are minimally replicative, and therefore fail to execute the second pro-regenerative phase of the HIF1α/PFKFB3 injury pathway. Instead, ß-cells in T2D remain trapped in the pro-survival first phase of the HIF1α injury repair response with metabolism and the mitochondrial network adapted to slow the rate of cell attrition at the expense of ß-cell function.


Assuntos
Diabetes Mellitus Tipo 2/patologia , Estresse do Retículo Endoplasmático/fisiologia , Células Secretoras de Insulina/patologia , Polipeptídeo Amiloide das Ilhotas Pancreáticas/metabolismo , Resposta a Proteínas não Dobradas/fisiologia , Adulto , Animais , Animais Geneticamente Modificados , Apoptose , Linhagem Celular Tumoral , Diabetes Mellitus Tipo 2/metabolismo , Modelos Animais de Doenças , Glicólise/fisiologia , Humanos , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Polipeptídeo Amiloide das Ilhotas Pancreáticas/genética , Masculino , Pessoa de Meia-Idade , Fosforilação Oxidativa , Fosfofrutoquinase-2/metabolismo , Agregados Proteicos/fisiologia , Ratos
14.
Mol Cell Biol ; 39(17)2019 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-31208980

RESUMO

The pancreatic-islet-enriched transcription factors MafA and MafB have unique expression patterns in ß cells in rodents. MafA is specifically expressed in ß cells and is a key regulatory factor for maintaining adult ß-cell function, whereas MafB plays an essential role in ß-cell development during embryogenesis, and its expression in ß cells gradually decreases and is restricted to α cells after birth in rodents. However, it was previously observed that MafB started to be reexpressed in insulin-positive (insulin+) ß cells in MafA-deficient adult mice. To elucidate how MafB functions in the adult ß cell under MafA-deficient conditions, we generated MafA and MafB double-knockout (A0B0) mice in which MafB was specifically deleted from ß cells. As a result, the A0B0 mice became more vulnerable to diabetes under a high-fat diet (HFD) treatment, with impaired islet formation and a decreased number of insulin+ ß cells because of increased ß-cell apoptosis, indicating MafB can take part in the maintenance of adult ß cells under certain pathological conditions.


Assuntos
Diabetes Mellitus/genética , Células Secretoras de Insulina/citologia , Fatores de Transcrição Maf Maior/genética , Fator de Transcrição MafB/genética , Animais , Apoptose , Células Cultivadas , Diabetes Mellitus/induzido quimicamente , Diabetes Mellitus/metabolismo , Diabetes Mellitus/patologia , Dieta Hiperlipídica/efeitos adversos , Modelos Animais de Doenças , Desenvolvimento Embrionário , Células Secretoras de Insulina/metabolismo , Células Secretoras de Insulina/patologia , Fator de Transcrição MafB/metabolismo , Camundongos , Camundongos Knockout
15.
Oxid Med Cell Longev ; 2019: 1826303, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31249641

RESUMO

Pancreatic ß-cells are vulnerable to oxidative stress due to their low content of redox buffers, such as glutathione, but possess a rich content of thioredoxin, peroxiredoxin, and other proteins capable of redox relay, transferring redox signaling. Consequently, it may be predicted that cytosolic antioxidants could interfere with the cytosolic redox signaling and should not be recommended for any potential therapy. In contrast, mitochondrial matrix-targeted antioxidants could prevent the primary oxidative stress arising from the primary superoxide sources within the mitochondrial matrix, such as at the flavin (IF) and ubiquinone (IQ) sites of superoxide formation within respiratory chain complex I and the outer ubiquinone site (IIIQ) of complex III. Therefore, using time-resolved confocal fluorescence monitoring with MitoSOX Red, we investigated various effects of mitochondria-targeted antioxidants in model pancreatic ß-cells (insulinoma INS-1E cells) and pancreatic islets. Both SkQ1 (a mitochondria-targeted plastoquinone) and a suppressor of complex III site Q electron leak (S3QEL) prevented superoxide production released to the mitochondrial matrix in INS-1E cells with stimulatory glucose, where SkQ1 also exhibited an antioxidant role for UCP2-silenced cells. SkQ1 acted similarly at nonstimulatory glucose but not in UCP2-silenced cells. Thus, UCP2 can facilitate the antioxidant mechanism based on SkQ1+ fatty acid anion- pairing. The elevated superoxide formation induced by antimycin A was largely prevented by S3QEL, and that induced by rotenone was decreased by SkQ1 and S3QEL and slightly by S1QEL, acting at complex I site Q. Similar results were obtained with the MitoB probe, for the LC-MS-based assessment of the 4 hr accumulation of reactive oxygen species within the mitochondrial matrix but for isolated pancreatic islets. For 2 hr INS-1E incubations, some samples were influenced by the cell death during the experiment. Due to the frequent dependency of antioxidant effects on metabolic modes, we suggest a potential use of mitochondria-targeted antioxidants for the treatment of prediabetic states after cautious nutrition-controlled tests. Their targeted delivery might eventually attenuate the vicious spiral leading to type 2 diabetes.


Assuntos
Antioxidantes/farmacologia , Células Secretoras de Insulina/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Membranas Mitocondriais/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Animais , Células Cultivadas , Células Secretoras de Insulina/metabolismo , Células Secretoras de Insulina/patologia , Camundongos , Camundongos Endogâmicos C57BL , Mitocôndrias/metabolismo , Mitocôndrias/patologia , Membranas Mitocondriais/metabolismo , Membranas Mitocondriais/patologia , Compostos Organofosforados , Oxirredução , Fenantridinas , Proteína Desacopladora 2/metabolismo
16.
PLoS One ; 14(5): e0217110, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31145732

RESUMO

Maturity-onset diabetes of the young (MODY) is a heterozygous monogenic diabetes; more than 14 disease genes have been identified. However, the pathogenesis of MODY is not fully understood because the patients' pancreatic beta cells are inaccessible. To elucidate the pathology of MODY, we established MODY3 patient-derived iPS (MODY3-iPS) cells using non-integrating Sendai virus (SeV) vector and examined the mutant mRNA and protein of HNF1A (Hepatocyte Nuclear factor 1A) after pancreatic lineage differentiation. Our patient had a cytosine insertion in the HNF1A gene (P291fsinsC) causing frameshift and making a premature termination codon (PTC). We confirmed these MODY3-iPS cells possessed the characteristics of pluripotent stem cells. After we differentiated them into pancreatic beta cells, transcripts of HNF1A gene were cloned and sequenced. We found that P291fsinsC mutant transcripts were much less frequent than wild ones, but they increased after adding cycloheximide (CHX) to the medium. These results suggested that mutant mRNA was destroyed by nonsense-mediated mRNA decay (NMD). Moreover, we were not able to detect any band of mutant proteins in pancreatic lineage cells which were differentiated from MODY3-iPSCs by western blot (WB) analysis. A scarcity of the truncated form of mutant protein may indicate that MODY3 might be caused by a haplo-insufficiency effect rather than a dominant negative manner.


Assuntos
Diabetes Mellitus Tipo 2/metabolismo , Fator 1-alfa Nuclear de Hepatócito/metabolismo , Células-Tronco Pluripotentes Induzidas/patologia , Células Secretoras de Insulina/patologia , Mutação , RNA Mensageiro/genética , Células Cultivadas , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/patologia , Feminino , Haploinsuficiência , Fator 1-alfa Nuclear de Hepatócito/genética , Humanos , Células-Tronco Pluripotentes Induzidas/metabolismo , Células Secretoras de Insulina/metabolismo , RNA Mensageiro/metabolismo
17.
J Biol Chem ; 294(21): 8452-8463, 2019 05 24.
Artigo em Inglês | MEDLINE | ID: mdl-30975901

RESUMO

The islet amyloid polypeptide (IAPP) is a 37-residue peptide hormone whose deposition as amyloid fibrils in the pancreatic islets is associated with type 2 diabetes. Previous studies have suggested that residue Asn-21 plays a critical role in the in vitro self-assembly of IAPP. Herein, we studied structure-self-assembly relationships focusing on position 21 to gain detailed insights into the molecular mechanisms of IAPP self-assembly and to probe the conformational nature of the toxic assemblies associated with ß-cell death. Thioflavin T (ThT) fluorescence, CD spectroscopy, and transmission EM analysis revealed that the Asn-21 amide side chain is not required for IAPP nucleation and amyloid elongation, as N21A and N21G variants assembled into prototypical fibrils. In contrast, Asn-21 substitution with the conformationally constrained and turn-inducing residue Pro accelerated IAPP self-assembly. Successive substitutions with hydrophobic residues led to the formation of ThT-negative ß-sheet-rich aggregates having high surface hydrophobicity. Cell-based assays revealed no direct correlation between the in vitro amyloidogenicity of these variants and their toxicity. In contrast, leakage of anionic lipid vesicles disclosed that membrane disruption is closely associated with cytotoxicity. We observed that the N21F variant self-assembles into worm-like aggregates, causing loss of lipid membrane structural integrity and inducing ß-cell apoptosis. These results indicate that specific intra- and intermolecular interactions involving Asn-21 promote IAPP primary nucleation events by modulating the conformational conversion of the oligomeric intermediates into amyloid fibrils. Our study identifies position 21 as a hinge residue that modulates IAPP amyloidogenicity and cytotoxicity.


Assuntos
Apoptose/efeitos dos fármacos , Membrana Celular/metabolismo , Células Secretoras de Insulina/metabolismo , Polipeptídeo Amiloide das Ilhotas Pancreáticas , Peptídeos , Animais , Linhagem Celular Tumoral , Membrana Celular/patologia , Humanos , Interações Hidrofóbicas e Hidrofílicas , Células Secretoras de Insulina/patologia , Polipeptídeo Amiloide das Ilhotas Pancreáticas/química , Polipeptídeo Amiloide das Ilhotas Pancreáticas/metabolismo , Polipeptídeo Amiloide das Ilhotas Pancreáticas/farmacologia , Peptídeos/química , Peptídeos/metabolismo , Peptídeos/farmacologia , Estrutura Secundária de Proteína , Ratos
18.
Acta Histochem ; 121(4): 508-515, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31014904

RESUMO

The role of mast cells (MCs) in type 2 diabetes (T2D) is not thoroughly studied as much as in T1D. Therefore in the current study we investigated correlation between these cells and various parameters of islets of Langerhans (IOL) in rats which were equally divided (n = 40) into; control and diabetic groups. We detected a significantly increased (p < 0.05) MC count (MCC) in the diabetic IOL compared to the control, together with a noticeable intra-islet seeding of these cells which displayed a tryptase positive immunostaining. A significant positive correlation (p < 0.05) between MCC and the % of glucagon cells per islet was detected in DM, unlike mass of the islets, mass of ß-cells, and % of ß-cells per islet which were negatively correlated with MCC. Similarly, there was a negative correlation between MCC with ß-cell proliferation and neogenesis frequency in DM. This highlights the potential association between the increased MC number and the diminished islet`s mass as well as regeneration which may fasten the progression of T2D.


Assuntos
Diabetes Mellitus Tipo 2/patologia , Células Secretoras de Glucagon/fisiologia , Células Secretoras de Insulina/fisiologia , Animais , Proliferação de Células/fisiologia , Células Secretoras de Glucagon/patologia , Imuno-Histoquímica , Células Secretoras de Insulina/patologia , Masculino , Mastócitos , Ratos , Ratos Sprague-Dawley , Triptases/metabolismo
19.
Environ Pollut ; 249: 822-830, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30953944

RESUMO

Polychlorinated biphenyls (PCBs) are a class of persistent organic pollutants that have been shown to be related to the occurrence of type 2 diabetes mellitus (T2DM). Nevertheless, it is necessary to further explore the development of T2DM caused by PCBs and its underlying mechanisms. In the present study, 21-day-old C57BL/6 male mice were orally treated with Aroclor 1254 (0.5, 5, 50 or 500 µg kg-1) once every three days. After exposure for 66 d, the mice showed impaired glucose tolerance, 13% and 14% increased fasting serum insulin levels (FSIL), and 63% and 69% increases of the pancreatic ß-cell mass in the 50 and 500 µg kg-1 groups, respectively. After stopping exposure for 90 d, treated mice returned to normoglycemia and normal FSIL. After re-exposure of these recovered mice to Aroclor 1254 for 30 d, fasting plasma glucose showed 15%, 28% and 16% increase in the 5, 50 and 500 µg kg-1 treatments, FSIL exhibited 35%, 27%, 30% and 32% decrease in the 0.5, 5, 50 or 500 µg kg-1 groups respectively, and there was no change in pancreatic ß-cell mass. Transcription of the pancreatic insulin gene (Ins2) was significantly down-regulated in the 50 and 500 µg kg-1 groups, while DNA-methylation levels were simultaneously increased in the Ins2 promoter during the course of exposure, recovery and re-exposure. Reduced insulin levels were initially rescued by a compensative increase in ß-cell mass. However, ß-cell mass eventually failed to make sufficient levels of insulin, resulting in significant increases in fasting blood glucose, and indicating the development of T2DM.


Assuntos
Glicemia/efeitos dos fármacos , Poluentes Ambientais/toxicidade , Homeostase/efeitos dos fármacos , Células Secretoras de Insulina/efeitos dos fármacos , Animais , Glicemia/metabolismo , Metilação de DNA/efeitos dos fármacos , Diabetes Mellitus Experimental/sangue , Diabetes Mellitus Experimental/patologia , Diabetes Mellitus Experimental/fisiopatologia , Poluentes Ambientais/administração & dosagem , Insulina/sangue , Insulina/genética , Células Secretoras de Insulina/patologia , Masculino , Camundongos Endogâmicos C57BL
20.
Cell Biochem Funct ; 37(3): 139-147, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30883865

RESUMO

Lin28, which is highly expressed during embryogenesis, has been shown to play an important role in cell growth and embryonic development. Meanwhile, Lin28 represses let-7 miRNA biogenesis and block pre-let-7 processing in the cytoplasm. The let-7 family of miRNAs is known to repress oncogenesis and cell cycle progression by targeting oncogenic genes and signalling pathways. Consequently, Lin28 acts as an oncogene by upregulating let-7 targets through the repression of let-7 biogenesis. A recent genome-wide association study (GWAS) showed that many genes related to Type 2 diabetes (T2D) are also oncogenes or cell cycle regulators. The role of Lin28 in mouse growth and glucose metabolism in metabolic-related tissues has also been studied. In these studies, whole-body Lin28 overexpression was found to promote glucose utilization and prevent weight gain by inhibiting let-7 biogenesis. Furthermore, Lin28 has been found to directly stimulate skeletal myogenesis and cell growth. Therefore, we determined whether similar effects mediated by Lin28a, which is essential for cell growth and proliferation, may also apply to pancreatic ß-cells. We found that overexpression of Lin28a protects pancreatic ß-cells from streptozotocin (STZ)-induced ß-cell destruction in vitro and in vivo. Furthermore, Lin28a-overexpressing transgenic (Tg) mice had higher insulin secretion in the presence of glucose than in control mice. Our findings suggest that the Lin28/let-7 axis is an important regulator of pancreatic ß-cell functions and that precise modulation of this axis may be helpful in treating metabolic diseases such as diabetes. SIGNIFICANCE OF THE STUDY: We demonstrate that Lin28a prevents pancreatic ß-cell death against streptozotocin (STZ)-induced ß-cell destruction in vitro and in vivo. Furthermore, Lin28a promotes cell survival and proliferation by activating the PI3K-Akt signalling pathway, which may be dependent on let-7 regulation. Taken together, our results imply that the Lin28a/let-7 axis is an important regulator of pancreatic ß-cell functions and that precise modulation of this axis may be helpful in treating metabolic diseases such as diabetes.


Assuntos
Diabetes Mellitus Experimental/prevenção & controle , Células Secretoras de Insulina/efeitos dos fármacos , Proteínas de Ligação a RNA/genética , Animais , Diabetes Mellitus Experimental/induzido quimicamente , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Experimental/patologia , Modelos Animais de Doenças , Células Secretoras de Insulina/patologia , Masculino , Camundongos , Proteínas de Ligação a RNA/metabolismo , Estreptozocina , Células Tumorais Cultivadas
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