Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 3.333
Filtrar
1.
Nat Commun ; 12(1): 5991, 2021 10 13.
Artigo em Inglês | MEDLINE | ID: mdl-34645803

RESUMO

The reticulon-3 (RTN3)-driven targeting complex promotes clearance of misfolded prohormones from the endoplasmic reticulum (ER) for lysosomal destruction by ER-phagy. Because RTN3 resides in the cytosolic leaflet of the ER bilayer, the mechanism of selecting misfolded prohormones as ER-phagy cargo on the luminal side of the ER membrane remains unknown. Here we identify the ER transmembrane protein PGRMC1 as an RTN3-binding partner. Via its luminal domain, PGRMC1 captures misfolded prohormones, targeting them for RTN3-dependent ER-phagy. PGRMC1 selects cargos that are smaller than the large size of other reported ER-phagy substrates. Cargos for PGRMC1 include mutant proinsulins that block secretion of wildtype proinsulin through dominant-negative interactions within the ER, causing insulin-deficiency. Chemical perturbation of PGRMC1 partially restores WT insulin storage by preventing ER-phagic degradation of WT and mutant proinsulin. Thus, PGRMC1 acts as a size-selective cargo receptor during RTN3-dependent ER-phagy, and is a potential therapeutic target for diabetes.


Assuntos
Proteínas de Transporte/genética , Retículo Endoplasmático/metabolismo , Células Secretoras de Insulina/metabolismo , Proteínas de Membrana/genética , Proteínas do Tecido Nervoso/genética , Proinsulina/genética , Receptores de Progesterona/genética , Animais , Autofagia/genética , Proteínas de Transporte/metabolismo , Linhagem Celular Tumoral , Retículo Endoplasmático/genética , Expressão Gênica , Células HEK293 , Humanos , Células Secretoras de Insulina/citologia , Ilhotas Pancreáticas/citologia , Ilhotas Pancreáticas/metabolismo , Lisossomos/metabolismo , Proteínas de Membrana/metabolismo , Camundongos , Mutação , Proteínas do Tecido Nervoso/metabolismo , Cultura Primária de Células , Proinsulina/metabolismo , Ligação Proteica , Domínios Proteicos , Dobramento de Proteína , Proteólise , Ratos , Receptores de Progesterona/metabolismo
2.
Elife ; 102021 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-34467852

RESUMO

The endoplasmic reticulum (ER) is composed of sheets and tubules. Here we report that the COPII coat subunit, SEC24C, works with the long form of the tubular ER-phagy receptor, RTN3, to target dominant-interfering mutant proinsulin Akita puncta to lysosomes. When the delivery of Akita puncta to lysosomes was disrupted, large puncta accumulated in the ER. Unexpectedly, photobleach analysis indicated that Akita puncta behaved as condensates and not aggregates, as previously suggested. Akita puncta enlarged when either RTN3 or SEC24C were depleted, or when ER sheets were proliferated by either knocking out Lunapark or overexpressing CLIMP63. Other ER-phagy substrates that are segregated into tubules behaved like Akita, while a substrate (type I procollagen) that is degraded by the ER-phagy sheets receptor, FAM134B, did not. Conversely, when ER tubules were augmented in Lunapark knock-out cells by overexpressing reticulons, ER-phagy increased and the number of large Akita puncta was reduced. Our findings imply that segregating cargoes into tubules has two beneficial roles. First, it localizes mutant misfolded proteins, the receptor, and SEC24C to the same ER domain. Second, physically restraining condensates within tubules, before they undergo ER-phagy, prevents them from enlarging and impacting cell health.


Assuntos
Proteínas de Transporte/metabolismo , Retículo Endoplasmático/metabolismo , Proteínas de Membrana/metabolismo , Proinsulina/metabolismo , Animais , Autofagia , Linhagem Celular Tumoral , Células HEK293 , Humanos , Lisossomos , Camundongos Knockout , Agregados Proteicos , Dobramento de Proteína
3.
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
4.
Cell Mol Life Sci ; 78(16): 6017-6031, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34245311

RESUMO

A precondition for efficient proinsulin export from the endoplasmic reticulum (ER) is that proinsulin meets ER quality control folding requirements, including formation of the Cys(B19)-Cys(A20) "interchain" disulfide bond, facilitating formation of the Cys(B7)-Cys(A7) bridge. The third proinsulin disulfide, Cys(A6)-Cys(A11), is not required for anterograde trafficking, i.e., a "lose-A6/A11" mutant [Cys(A6), Cys(A11) both converted to Ser] is well secreted. Nevertheless, an unpaired Cys(A11) can participate in disulfide mispairings, causing ER retention of proinsulin. Among the many missense mutations causing the syndrome of Mutant INS gene-induced Diabetes of Youth (MIDY), all seem to exhibit perturbed proinsulin disulfide bond formation. Here, we have examined a series of seven MIDY mutants [including G(B8)V, Y(B26)C, L(A16)P, H(B5)D, V(B18)A, R(Cpep + 2)C, E(A4)K], six of which are essentially completely blocked in export from the ER in pancreatic ß-cells. Three of these mutants, however, must disrupt the Cys(A6)-Cys(A11) pairing to expose a critical unpaired cysteine thiol perturbation of proinsulin folding and ER export, because when introduced into the proinsulin lose-A6/A11 background, these mutants exhibit native-like disulfide bonding and improved trafficking. This maneuver also ameliorates dominant-negative blockade of export of co-expressed wild-type proinsulin. A growing molecular understanding of proinsulin misfolding may permit allele-specific pharmacological targeting for some MIDY mutants.


Assuntos
Diabetes Mellitus Tipo 2/metabolismo , Proinsulina/metabolismo , Adolescente , Células Cultivadas , Cisteína/genética , Cisteína/metabolismo , Diabetes Mellitus Tipo 2/genética , Dissulfetos/metabolismo , Retículo Endoplasmático/genética , Retículo Endoplasmático/metabolismo , Humanos , Insulina/genética , Insulina/metabolismo , Células Secretoras de Insulina/metabolismo , Mutação de Sentido Incorreto/genética , Proinsulina/genética , Dobramento de Proteína
5.
Nat Rev Endocrinol ; 17(8): 455-467, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34163039

RESUMO

Diabetes mellitus is characterized by the failure of insulin-secreting pancreatic ß-cells (or ß-cell death) due to either autoimmunity (type 1 diabetes mellitus) or failure to compensate for insulin resistance (type 2 diabetes mellitus; T2DM). In addition, mutations of critical genes cause monogenic diabetes. The endoplasmic reticulum (ER) is the primary site for proinsulin folding; therefore, ER proteostasis is crucial for both ß-cell function and survival under physiological and pathophysiological challenges. Importantly, the ER is also the major intracellular Ca2+ storage organelle, generating Ca2+ signals that contribute to insulin secretion. ER stress is associated with the pathogenesis of diabetes mellitus. In this Review, we summarize the mutations in monogenic diabetes that play causal roles in promoting ER stress in ß-cells. Furthermore, we discuss the possible mechanisms responsible for ER proteostasis imbalance with a focus on T2DM, in which both genetics and environment are considered important in promoting ER stress in ß-cells. We also suggest that controlled insulin secretion from ß-cells might reduce the progression of a key aspect of the metabolic syndrome, namely nonalcoholic fatty liver disease. Finally, we evaluate potential therapeutic approaches to treat T2DM, including the optimization and protection of functional ß-cell mass in individuals with T2DM.


Assuntos
Diabetes Mellitus Tipo 2/tratamento farmacológico , Estresse do Retículo Endoplasmático/fisiologia , Células Secretoras de Insulina/fisiologia , Animais , Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/fisiopatologia , Retículo Endoplasmático/metabolismo , Humanos , Hipoglicemiantes/uso terapêutico , Secreção de Insulina/fisiologia , Terapia de Alvo Molecular/métodos , Terapia de Alvo Molecular/tendências , Proinsulina/metabolismo
6.
Diabetes ; 70(5): 1038-1050, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33947721

RESUMO

Analysis of data from clinical cohorts, and more recently from human pancreatic tissue, indicates that reduced prohormone processing is an early and persistent finding in type 1 diabetes. In this article, we review the current state of knowledge regarding alterations in islet prohormone expression and processing in type 1 diabetes and consider the clinical impact of these findings. Lingering questions, including pathologic etiologies and consequences of altered prohormone expression and secretion in type 1 diabetes, and the natural history of circulating prohormone production in health and disease, are considered. Finally, key next steps required to move forward in this area are outlined, including longitudinal testing of relevant clinical populations, studies that probe the genetics of altered prohormone processing, the need for combined functional and histologic testing of human pancreatic tissues, continued interrogation of the intersection between prohormone processing and autoimmunity, and optimal approaches for analysis. Successful resolution of these questions may offer the potential to use altered prohormone processing as a biomarker to inform therapeutic strategies aimed at personalized intervention during the natural history of type 1 diabetes and as a pathogenic anchor for identification of potential disease-specific endotypes.


Assuntos
Diabetes Mellitus Tipo 1/metabolismo , Células Secretoras de Insulina/metabolismo , Animais , Diabetes Mellitus Tipo 1/imunologia , Humanos , Células Secretoras de Insulina/imunologia , Ilhotas Pancreáticas/metabolismo , Proinsulina/metabolismo
7.
FASEB J ; 35(5): e21515, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33811688

RESUMO

The conserved endoplasmic reticulum (ER) membrane protein TRAPα (translocon-associated protein, also known as signal sequence receptor 1, SSR1) has been reported to play a critical but unclear role in insulin biosynthesis. TRAPα/SSR1 is one component of a four-protein complex including TRAPß/SSR2, TRAPγ/SSR3, and TRAPδ/SSR4. The TRAP complex topologically has a small exposure on the cytosolic side of the ER via its TRAPγ/SSR3 subunit, whereas TRAPß/SSR2 and TRAPδ/SSR4 function along with TRAPα/SSR1 largely on the luminal side of the ER membrane. Here, we have examined pancreatic ß-cells with deficient expression of either TRAPß/SSR2 or TRAPδ/SSR4, which does not perturb mRNA expression levels of other TRAP subunits, or insulin mRNA. However, deficient protein expression of TRAPß/SSR2 and, to a lesser degree, TRAPδ/SSR4, diminishes the protein levels of other TRAP subunits, concomitant with deficient steady-state levels of proinsulin and insulin. Deficient TRAPß/SSR2 or TRAPδ/SSR4 is not associated with any apparent defect of exocytotic mechanism but rather by a decreased abundance of the proinsulin and insulin that accompanies glucose-stimulated secretion. Amino acid pulse labeling directly establishes that much of the steady-state deficiency of intracellular proinsulin can be accounted for by diminished proinsulin biosynthesis, observed in a pulse-labeling as short as 5 minutes. The proinsulin and insulin levels in TRAPß/SSR2 or TRAPδ/SSR4 null mutant ß-cells are notably recovered upon re-expression of the missing TRAP subunit, accompanying a rebound of proinsulin biosynthesis. Remarkably, overexpression of TRAPα/SSR1 can also suppress defects in ß-cells with diminished expression of TRAPß/SSR2, strongly suggesting that TRAPß/SSR2 is needed to support TRAPα/SSR1 function.


Assuntos
Proteínas de Ligação ao Cálcio/deficiência , Retículo Endoplasmático/metabolismo , Glucose/metabolismo , Insulina/biossíntese , Insulinoma/patologia , Glicoproteínas de Membrana/deficiência , Proinsulina/biossíntese , Receptores Citoplasmáticos e Nucleares/deficiência , Receptores de Peptídeos/deficiência , Animais , Células Cultivadas , Células Secretoras de Insulina/citologia , Insulinoma/metabolismo , Neoplasias Pancreáticas/metabolismo , Neoplasias Pancreáticas/patologia , Ratos
8.
Front Immunol ; 12: 645817, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33841427

RESUMO

T-cell responses to insulin and its precursor proinsulin are central to islet autoimmunity in humans and non-obese diabetic (NOD) mice that spontaneously develop autoimmune diabetes. Mice have two proinsulin genes proinsulin -1 and 2 that are differentially expressed, with predominant proinsulin-2 expression in the thymus and proinsulin-1 in islet beta-cells. In contrast to proinsulin-2, proinsulin-1 knockout NOD mice are protected from autoimmune diabetes. This indicates that proinsulin-1 epitopes in beta-cells maybe preferentially targeted by autoreactive T cells. To study the contribution of proinsulin-1 reactive T cells in autoimmune diabetes, we generated transgenic NOD mice with tetracycline-regulated expression of proinsulin-1 in antigen presenting cells (TIP-1 mice) with an aim to induce immune tolerance. TIP-1 mice displayed a significantly reduced incidence of spontaneous diabetes, which was associated with reduced severity of insulitis and insulin autoantibody development. Antigen experienced proinsulin specific T cells were significantly reduced in in TIP-1 mice indicating immune tolerance. Moreover, T cells from TIP-1 mice expressing proinsulin-1 transferred diabetes at a significantly reduced frequency. However, proinsulin-1 expression in APCs had minimal impact on the immune responses to the downstream antigen islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) and did not prevent diabetes in NOD 8.3 mice with a pre-existing repertoire of IGRP reactive T cells. Thus, boosting immune tolerance to proinsulin-1 partially prevents islet-autoimmunity. This study further extends the previously established role of proinsulin-1 epitopes in autoimmune diabetes in NOD mice.


Assuntos
Diabetes Mellitus Tipo 1/prevenção & controle , Tolerância Imunológica , Proinsulina/fisiologia , Animais , Autoanticorpos/análise , Glucose-6-Fosfatase/fisiologia , Insulina/imunologia , Camundongos , Camundongos Endogâmicos NOD , Proinsulina/genética , Proinsulina/imunologia
9.
Front Immunol ; 12: 648021, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33889155

RESUMO

Introduction: Insulin and proinsulin autoantibodies (IAA/PAA) are usually the first markers to appear in patients with type 1 Diabetes Mellitus (T1DM) and their prevalence ranges from 10 to 60% in the child-adolescent population. The reference method for IAA/PAA detection is the Radioligand Binding Assay (RBA), a highly specific and sensitive technique, but expensive and polluting. The aim of this work was to develop a novel flow cytometric microsphere-based immunoassay (FloCMIA) for PAA detection, employing recombinant human proinsulin (PI), as an alternative method to RBA, less expensive and harmful to the environment. Materials and Methods: Human PI was expressed as Thioredoxin fusion protein (TrxPI) in E. coli and a fraction was biotinylated. A double paratope model was used in which samples were incubated with TrxPI-biotin and microspheres adsorbed with TrxPI. The immune complexes were revealed using Streptavidin-Phycoerythrin. The geometric mean of the signals was analyzed, and the results were expressed as Standard Deviation scores (SDs). Sera from 100 normal human control and from 111 type 1 diabetic patients were evaluated by FloCMIA. To correlate the novel assay with RBA, 51 diabetic patients were selected, spanning a wide range of PAA reactivity by RBA. Results: The study of ROC curves allowed choosing a cut-off value of 3.0 SDs and the AUC was 0.705, indicating that FloCMIA has fair ability to distinguish between samples from each group. A prevalence of 50% for PAA was obtained in the population of diabetic patients studied. The specificity was 96% and the analytical sensitivity (percentage of patients RBA positive, also positive by FloCMIA) was 69%. There was a substantial agreement between methods (kappa statistic=0.700). Conclusions: A novel immunoassay based on flow cytometry that uses easy-to produce recombinant PI was developed. This assay constitutes an innovative and cost-effective alternative to RBA for the determination of PAA in patients' sera. The method developed here, presents good performance and a wide dynamic range together with a small required sample volume. Furthermore, these results make it possible to develop multiplex immunoassays that allow the combined detection of autoantibodies present in T1DM and other related autoimmune diseases.


Assuntos
Autoanticorpos/imunologia , Autoantígenos/metabolismo , Diabetes Mellitus Tipo 1/imunologia , Escherichia coli/metabolismo , Citometria de Fluxo/métodos , Proinsulina/imunologia , Proinsulina/metabolismo , Adolescente , Adulto , Autoanticorpos/sangue , Autoantígenos/genética , Biomarcadores/sangue , Estudos de Casos e Controles , Criança , Pré-Escolar , Diabetes Mellitus Tipo 1/sangue , Escherichia coli/genética , Feminino , Humanos , Imunoensaio/métodos , Lactente , Masculino , Microesferas , Pessoa de Meia-Idade , Proinsulina/genética , Proteínas Recombinantes/imunologia , Proteínas Recombinantes/metabolismo , Adulto Jovem
10.
Khirurgiia (Mosk) ; (3): 5-10, 2021.
Artigo em Russo | MEDLINE | ID: mdl-33710820

RESUMO

OBJECTIVE: To report own experience in the treatment of patients with proinsulinoma. MATERIAL AND METHODS: There were 10 patients with increased proinsulin production and normal insulin level since 2017. Most of them were young women. RESULTS: Fasting hypoglycemia in all patients was severe (up to 0.7 mmol/l). Clinical picture consisted of typical symptoms similar to those in insulinoma. The main difference in the course of proinsulinoma was the absence of weight gain in 7 patients and rapid weight loss (from 210 to 90 kg within 9 months) in 1 patient. All patients with proinsulinoma underwent surgery. In most cases, minimally aggressive surgery was performed. CONCLUSION: Proinsulinoma is an extremely rare endocrine-active neuroendocrine pancreatic tumor. Differential features of proinsulinoma are the absence of weight gain and normal insulin levels in the presence of hypoglycemia. Surgery is the only radical method of treatment.


Assuntos
Insulinoma , Neoplasias Pancreáticas , Proinsulina/biossíntese , Feminino , Humanos , Hipoglicemia/etiologia , Insulina/análise , Insulinoma/complicações , Insulinoma/diagnóstico , Insulinoma/metabolismo , Insulinoma/cirurgia , Masculino , Pâncreas/metabolismo , Pâncreas/patologia , Pâncreas/cirurgia , Neoplasias Pancreáticas/complicações , Neoplasias Pancreáticas/diagnóstico , Neoplasias Pancreáticas/metabolismo , Neoplasias Pancreáticas/cirurgia
11.
Sci Rep ; 11(1): 6062, 2021 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-33723361

RESUMO

Men and women are sexually dimorphic but whether common anthropometric and biochemical parameters predict type 2 diabetes (T2D) in different ways has not been well studied. Here we recruit 1579 participants in Hainan Province, China, and group them by sex. We compared the prediction power of common parameters of T2D in two sexes by association, regression, and Receiver Operating Characteristic (ROC) analysis. HbA1c is associated with FPG stronger in women than in men and the regression coefficient is higher, consistent with higher prediction power for T2D. Age, waist circumference, BMI, systolic and diastolic blood pressure, triglyceride levels, total cholesterol, LDL, HDL, fasting insulin, and proinsulin levels all predict T2D better in women. Except for diastolic blood pressure, all parameters associate or tend to associate with FPG stronger in women than in men. Except for diastolic blood pressure and fasting proinsulin, all parameters associate or tend to associate with HbA1c stronger in women than in men. Except for fasting proinsulin and HDL, the regression coefficients of all parameters with FPG and HbA1c were higher in women than in men. Together, by the above anthropometric and biochemical measures, T2D is more readily predicted in women than men, suggesting the importance of sex-based subgroup analysis in T2D research.


Assuntos
Pressão Sanguínea , Diabetes Mellitus Tipo 2 , Hemoglobina A Glicada/metabolismo , Lipídeos/sangue , Proinsulina/sangue , Caracteres Sexuais , Adulto , Idoso , China/epidemiologia , Diabetes Mellitus Tipo 2/sangue , Diabetes Mellitus Tipo 2/epidemiologia , Diabetes Mellitus Tipo 2/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
12.
J Clin Endocrinol Metab ; 106(8): e3049-e3057, 2021 07 13.
Artigo em Inglês | MEDLINE | ID: mdl-33738477

RESUMO

CONTEXT: Small-for-gestational-age (SGA) is an indicator of poor fetal growth "programming" an elevated risk of type 2 diabetes in adulthood. Little is known about early-life endocrine characteristics in SGA subtypes. Stunting (short) and wasting (skinny) are considered distinct SGA phenotypes in neonatal prognosis. OBJECTIVES: This work aimed to assess whether SGA infants with stunting or wasting have similar alterations in neonatal endocrine metabolic health biomarkers. METHODS: This was a nested case-control study based on the 3D (Design, Develop, and Discover) birth cohort in Canada. The study subjects were 146 SGA (birth weight < 10th percentile) and 155 optimal-for-gestational age (OGA, 25th-75th percentiles) infants. Stunting was defined as birth length less than the 10th percentile, and wasting as body mass index less than the 10th percentile for sex and gestational age, respectively. Main outcome measures included cord plasma concentrations of insulin-like growth factor I (IGF-I), proinsulin, leptin, high-molecular-weight (HMW) adiponectin, and ghrelin. RESULTS: Comparing to OGA infants adjusted for maternal and neonatal characteristics, SGA infants with either stunting only or wasting only had lower cord plasma IGF-I and leptin concentrations. HMW adiponectin concentrations were lower in SGA infants with wasting only (P = .004), but similar in SGA infants with stunting only (P = .816). Only SGA infants with both stunting and wasting had substantially lower proinsulin (P < .001) and higher ghrelin concentrations (P < .001) than OGA infants. CONCLUSION: This study is the first to demonstrate that SGA infants with wasting only are characterized by low HMW adiponectin concentrations, whereas those with stunting only are not. SGA with both stunting and wasting are characterized by low proinsulin and high ghrelin concentrations.


Assuntos
Adiponectina/sangue , Sangue Fetal , Grelina/sangue , Fator de Crescimento Insulin-Like I/metabolismo , Leptina/sangue , Proinsulina/sangue , Biomarcadores , Estudos de Casos e Controles , Feminino , Humanos , Recém-Nascido , Recém-Nascido Pequeno para a Idade Gestacional , Masculino
13.
BMC Endocr Disord ; 21(1): 18, 2021 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-33485357

RESUMO

BACKGROUND: Currently, there is a lack of data relating to glycemic parameters and their relationship with C-peptide (CP) and proinsulin (PI) during the partial remission period (PRP) in type 1 diabetes mellitus (T1D). The aim of this study was to evaluate glycemic parameters in children with T1D who are in the PRP using intermittently scanned continuous glucose monitoring systems (isCGMS) and to investigate any relationships between CP and PI levels. METHODS: The study included 21 children who were in the PRP and 31 children who were not. A cross-sectional, non-randomized study was performed. Demographic, clinical data were collected and 2 week- isCGMS data were retrieved. RESULTS: The Serum CP showed a positive correlation with time-in-range in the PRP (p:0.03), however PI showed no correlations with glycemic parameters in both periods. The Serum CP and PI levels and the PI:CP ratio were significantly higher in the PRP group than in the non-PRP group. In the non-PRP group, the PI level was below 0.1 pmol/L (which is the detectable limit) in only 2 of the 17 cases as compared with none in the PRP group. Similarly, only 2 of the 17 children in the non-PRP group had CP levels of less than 0.2 nmol / L, although both had detectable PI levels. Overall time-in-range (3. 9-1.0 mmol/L) was significantly high in the PRP group. In contrast, the mean sensor glucose levels, time spent in hyperglycemia, and coefficient of variation levels (32.2vs 40.5%) were significantly lower in the PRP group. CONCLUSIONS: Although the mean glucose and time in range during the PRP was better than that in the non-PRP group, the glycemic variability during this period was not as low as expected. While the CP levels showed an association with TIR during the PRP, there was no correlation between PI levels and glycemic parameters. Further studies are needed to determine if PI might prove to be a useful parameter in clinical follow-up.


Assuntos
Peptídeo C/sangue , Diabetes Mellitus Tipo 1/sangue , Proinsulina/sangue , Adolescente , Glicemia , Automonitorização da Glicemia , Criança , Pré-Escolar , Estudos Transversais , Feminino , Humanos , Hiperglicemia/sangue , Hipoglicemiantes/uso terapêutico , Insulina/uso terapêutico , Masculino , Remissão Espontânea
14.
Am J Physiol Endocrinol Metab ; 320(1): E7-E18, 2021 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-33103448

RESUMO

Dietary carbohydrate restriction may improve the phenotype of Type 2 diabetes (T2D) patients. We aimed to investigate 6 wk of carbohydrate restriction on postprandial glucose metabolism, pancreatic α- and ß-cell function, gut hormone secretion, and satiety in T2D patients. Methods In a crossover design, 28 T2D patients (mean HbA1c: 60 mmol/mol) were randomized to 6 wk of carbohydrate-reduced high-protein (CRHP) diet and 6 wk of conventional diabetes (CD) diet (energy-percentage carbohydrate/protein/fat: 30/30/40 vs. 50/17/33). Twenty-four-hour continuous glucose monitoring (CGM) and mixed-meal tests were undertaken and fasting intact proinsulin (IP), 32,33 split proinsulin concentrations (SP), and postprandial insulin secretion rates (ISR), insulinogenic index (IGI), ß-cell sensitivity to glucose (Bup), glucagon, and gut hormones were measured. Gastric emptying was evaluated by postprandial paracetamol concentrations and satiety by visual analog scale ratings. A CRHP diet reduced postprandial glucose area under curve (net AUC) by 60% (P < 0.001), 24 h glucose by 13% (P < 0.001), fasting IP and SP concentrations (both absolute and relative to C-peptide, P < 0.05), and postprandial ISR (24%, P = 0.015), while IGI and Bup improved by 31% and 45% (both P < 0.001). The CRHP diet increased postprandial glucagon net AUC by 235% (P < 0.001), subjective satiety by 18% (P = 0.03), delayed gastric emptying by 15 min (P < 0.001), decreased gastric inhibitory polypeptide net AUC by 29% (P < 0.001), but had no significant effect on glucagon-like-peptide-1, total peptide YY, and cholecystokinin responses. A CRHP diet reduced glucose excursions and improved ß-cell function, including proinsulin processing, and increased subjective satiety in patients with T2D.


Assuntos
Diabetes Mellitus Tipo 2/dietoterapia , Diabetes Mellitus Tipo 2/metabolismo , Dieta com Restrição de Carboidratos , Hormônios Gastrointestinais/metabolismo , Glucose/metabolismo , Hiperglicemia/metabolismo , Células Secretoras de Insulina/metabolismo , Resposta de Saciedade , Adulto , Glicemia/metabolismo , Diabetes Mellitus Tipo 2/psicologia , Dieta com Restrição de Carboidratos/efeitos adversos , Proteínas na Dieta , Feminino , Esvaziamento Gástrico , Humanos , Secreção de Insulina , Masculino , Proinsulina/sangue , Resultado do Tratamento
15.
Diabetes ; 70(2): 529-537, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33122391

RESUMO

Lymph node stromal cells (LNSC) are essential for providing and maintaining peripheral self-tolerance of potentially autoreactive cells. In type 1 diabetes, proinsulin-specific CD8+ T cells, escaping central and peripheral tolerance, contribute to ß-cell destruction. Using G9Cα-/-CD8+ T cells specific for proinsulin, we studied the mechanisms by which LNSC regulate low-avidity autoreactive cells in the NOD mouse model of type 1 diabetes. Whereas MHC-matched NOD-LNSC significantly reduced G9Cα-/-CD8+ T-cell cytotoxicity and dendritic cell-induced proliferation, they failed to sufficiently regulate T cells stimulated by anti-CD3/CD28. In contrast, non-MHC-matched, control C57BL/6 mouse LNSC suppressed T-cell receptor engagement by anti-CD3/CD28 via MHC-independent mechanisms. This C57BL/6-LNSC suppression was maintained even after removal of the LNSC, demonstrating a direct effect of LNSC on T cells, modifying antigen sensitivity and effector function. Thus, our results suggest that a loss of NOD-LNSC MHC-independent suppressive mechanisms may contribute to diabetes development.


Assuntos
Linfócitos T CD8-Positivos/metabolismo , Diabetes Mellitus Tipo 1/metabolismo , Antígenos de Histocompatibilidade Classe II/metabolismo , Linfonodos/metabolismo , Proinsulina/metabolismo , Células Estromais/metabolismo , Animais , Células Dendríticas/metabolismo , Camundongos , Camundongos Endogâmicos NOD
16.
J Diabetes Investig ; 12(1): 63-66, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32531868

RESUMO

Serum high-molecular-weight adiponectin (HMWA) has a positive correlation with insulin secretion in the Japanese population. To validate this correlation, we investigated the correlation between serum HMWA and proinsulin, a marker of ß-cell dysfunction, in this population. A total of 488 participants (53.9% women) aged 35-79 years not taking oral hypoglycemic agents and/or insulin were enrolled. HMWA was significantly and inversely correlated with proinsulin adjusted for age and sex (partial regression coefficient ß = -0.37; 95% confidence interval -0.46 to -0.28). When the participants were divided into two groups by median values of body mass index (23.2 kg/m2 ), serum insulin (4.3 µU/mL) or homeostasis model assessment of insulin resistance (1.0), similar inverse correlations were observed adjusted for age and sex in both groups. Our results showed that the HMWA level was inversely correlated with the proinsulin level in a general Japanese population.


Assuntos
Adiponectina/sangue , Secreção de Insulina , Estilo de Vida , Obesidade/fisiopatologia , Proinsulina/sangue , Adulto , Idoso , Biomarcadores/sangue , Estudos Transversais , Feminino , Seguimentos , Humanos , Japão , Masculino , Pessoa de Meia-Idade , Obesidade/sangue , Prognóstico
17.
Biochem Biophys Res Commun ; 534: 680-686, 2021 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-33208230

RESUMO

Type 1 diabetes (T1D) is an autoimmune disease caused by destruction of insulin-producing ß cells. The response of autoreactive T cells to ß cell antigens plays a central role in the development of T1D. Recently, fusion peptides composed by insulin C-peptide fragments and other proteins were reported as ß cell target antigens for diabetogenic CD4+ T cells in non-obese diabetic (NOD) mice. In this study, we generated a T cell-receptor (TCR)-like monoclonal antibody (mAb) against a fusion peptide bound to major histocompatibility complex (MHC) class II component to elucidate the function of the fusion peptides in T1D. In addition, we developed a novel NFAT-GFP TCR reporter system to evaluate the TCR-like mAb. The NFAT-GFP reporter T cells expressing the diabetogenic TCR were specifically activated by the fusion peptide presented on the MHC class II molecules. By using the NFAT-GFP reporter T cells, we showed that the TCR-like mAb blocks the diabetogenic T cell response against the fusion peptide presented on the MHC class II molecules. Furthermore, the development of T1D was ameliorated when pre-diabetic NOD mice were treated with this mAb. These findings suggest that NFAT-GFP reporter T cells are useful to assess the function of specific TCR and the recognition of fusion peptides by T cells is crucial for the pathogenesis of T1D.


Assuntos
Anticorpos Monoclonais/farmacologia , Diabetes Mellitus Tipo 1/prevenção & controle , Proinsulina/antagonistas & inibidores , Proinsulina/imunologia , Receptores de Antígenos de Linfócitos T/imunologia , Animais , Peptídeo C/antagonistas & inibidores , Peptídeo C/genética , Peptídeo C/imunologia , Diabetes Mellitus Experimental/etiologia , Diabetes Mellitus Experimental/imunologia , Diabetes Mellitus Experimental/prevenção & controle , Diabetes Mellitus Tipo 1/etiologia , Diabetes Mellitus Tipo 1/imunologia , Progressão da Doença , Antígenos de Histocompatibilidade Classe II/genética , Antígenos de Histocompatibilidade Classe II/imunologia , Camundongos , Camundongos Endogâmicos NOD , Proinsulina/genética , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/imunologia , Linfócitos T/imunologia
18.
Rheumatology (Oxford) ; 60(8): 3826-3833, 2021 08 02.
Artigo em Inglês | MEDLINE | ID: mdl-33369681

RESUMO

OBJECTIVES: To investigate how markers of beta-cell secretion (proinsulin-processing metabolites) are expressed in SLE patients and their potential relation to features associated with the disease such as activity or damage. METHODS: One hundred and forty-four SLE patients and 69 nondiabetic sex- and age-matched controls were assessed. Beta-cell secretion molecules, as measured by insulin, split and intact proinsulins, and C-peptide levels were analysed in both groups. Multiple regression analysis was performed to compare proinsulin propeptides between groups and to explore the interrelations with SLE features. Analyses were adjusted for glucocorticoid intake and for insulin resistance classic risk factors. RESULTS: Fully multivariable analysis demonstrated that regardless of glucocorticoid use, SLE patients exhibited higher levels of split proinsulin. Likewise, the split proinsulin-to-insulin ratio was upregulated in patients with SLE undergoing glucocorticoid therapy [beta coeficient 0.19 (95% Confidence Interval 0.07, 0.30), P = 0.002] or not [beta coef. 0.09 (95% CI: 0.01, 0.17), P = 0.025]. Similar results were found for the intact proinsulin-to-insulin ratio, although differences were only statistically significant for patients taking glucocorticoids [beta coef. 0.08 (95% CI: 0.03, 0.12), P = 0.001]. SLE damage score was associated with higher serum levels of intact [beta coef. 0.51 (95% CI 0.17, 0.86) pmol/l, P = 0.004] and split proinsulins [beta coef. 1.65 (95% CI 0.24, 3.06) pmol/l, P = 0.022] after multivariable analysis, including disease duration and prednisone use. CONCLUSION: Among patients with SLE, proinsulin-processing metabolites, a marker of beta-cell disruption, are upregulated compared with matched controls. This disproportionate hyperproinsulinemia can be explained by the damage produced by the disease and occurs independently of prednisone use.


Assuntos
Peptídeo C/metabolismo , Diabetes Mellitus/metabolismo , Secreção de Insulina , Células Secretoras de Insulina/metabolismo , Insulina/metabolismo , Lúpus Eritematoso Sistêmico/metabolismo , Proinsulina/metabolismo , Adulto , Feminino , Glucocorticoides/uso terapêutico , Humanos , Resistência à Insulina , Lúpus Eritematoso Sistêmico/tratamento farmacológico , Masculino , Pessoa de Meia-Idade
19.
Biomolecules ; 10(12)2020 12 16.
Artigo em Inglês | MEDLINE | ID: mdl-33339173

RESUMO

Type 1 diabetes (T1D) is a chronic metabolic disease characterized by insulin deficiency, generally resulting from progressive autoimmune-mediated destruction of pancreatic beta cells. While the phenomenon of beta cell autoimmunity continues to be an active area of investigation, recent evidence suggests that beta cell stress responses are also important contributors to disease onset. Here we review the pathways driving different kinds of beta cell dysfunction and their respective therapeutic targets in the prevention of T1D. We discuss opportunities and important open questions around the effectiveness of beta cell therapies and challenges for clinical utility. We further evaluate ways in which beta cell drug therapy could be combined with immunotherapy for preventing T1D in light of our growing appreciation of disease heterogeneity and patient endotypes. Ultimately, the emergence of pharmacologic beta cell therapies for T1D have armed us with new tools and closing the knowledge gaps in T1D etiology will be essential for maximizing the potential of these approaches.


Assuntos
Diabetes Mellitus Tipo 1/prevenção & controle , Células Secretoras de Insulina/citologia , Animais , Apoptose , Autoimunidade , Dano ao DNA , Estresse do Retículo Endoplasmático , Humanos , Sistema Imunitário , Imunoterapia , Insulina/metabolismo , Camundongos , Camundongos Endogâmicos NOD , Proinsulina/metabolismo , Pesquisa Médica Translacional , Resposta a Proteínas não Dobradas
20.
Proc Natl Acad Sci U S A ; 117(47): 29618-29628, 2020 11 24.
Artigo em Inglês | MEDLINE | ID: mdl-33154160

RESUMO

Proteins have evolved to be foldable, and yet determinants of foldability may be inapparent once the native state is reached. Insight has emerged from studies of diseases of protein misfolding, exemplified by monogenic diabetes mellitus due to mutations in proinsulin leading to endoplasmic reticulum stress and ß-cell death. Cellular foldability of human proinsulin requires an invariant Phe within a conserved crevice at the receptor-binding surface (position B24). Any substitution, even related aromatic residue TyrB24, impairs insulin biosynthesis and secretion. As a seeming paradox, a monomeric TyrB24 insulin analog exhibits a native-like structure in solution with only a modest decrement in stability. Packing of TyrB24 is similar to that of PheB24, adjoining core cystine B19-A20 to seal the core; the analog also exhibits native self-assembly. Although affinity for the insulin receptor is decreased ∼20-fold, biological activities in cells and rats were within the range of natural variation. Together, our findings suggest that the invariance of PheB24 among vertebrate insulins and insulin-like growth factors reflects an essential role in enabling efficient protein folding, trafficking, and secretion, a function that is inapparent in native structures. In particular, we envision that the para-hydroxyl group of TyrB24 hinders pairing of cystine B19-A20 in an obligatory on-pathway folding intermediate. The absence of genetic variation at B24 and other conserved sites near this disulfide bridge-excluded due to ß-cell dysfunction-suggests that insulin has evolved to the edge of foldability. Nonrobustness of a protein's fitness landscape underlies both a rare monogenic syndrome and "diabesity" as a pandemic disease of civilization.


Assuntos
Insulina/metabolismo , Substituição de Aminoácidos/fisiologia , Animais , Linhagem Celular , Linhagem Celular Tumoral , Diabetes Mellitus/metabolismo , Dissulfetos/metabolismo , Redes Reguladoras de Genes/fisiologia , Células HEK293 , Humanos , Células Secretoras de Insulina/metabolismo , Células MCF-7 , Proinsulina/metabolismo , Ligação Proteica/fisiologia , Dobramento de Proteína , Ratos , Receptor de Insulina/metabolismo , Relação Estrutura-Atividade
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...