RESUMO
AIMS: To explore the impact of GC administration periconceptionally on the glucose metabolism of adult offspring (male and female) and whether this periconception exposure might influence the metabolic outcomes when the offspring are also treated with dexamethasone in adult life. MATERIALS AND METHODS: Rats received a daily injection of dexamethasone (1â¯mg/kg, body mass) or saline solution (1â¯mL/kg body mass) for 7 consecutive days prior became pregnant. Male and female offspring had glucose homeostasis assessed at 3- and 6-month-old and after dexamethasone treatment (1â¯mg/kg, body mass) or vehicle for 5 consecutive days. Then, murinometric, functional, biochemical, and histomorphometric analyses were performed. KEY FINDINGS: Male and female offspring born from rats treated with GC prior to becoming pregnant had none of the murinometric and metabolic outcomes (i.e., body mass, food intake, blood glucose, plasma triacylglycerol, and glucose tolerance) changed up to 6-month-old. None of the expected diabetogenic effects caused by dexamethasone treatment at 6-month of age (i.e., elevation in fasting blood glucose, plasma insulin, triacylglycerol, and albumin, glucose intolerance, insulin insensitivity, augmentation in hepatic glycogen content, and increase in pancreatic islet mass) was observed in offspring born from rats treated with dexamethasone in the prepregnancy period. However, periconceptional exposure to GC predisposed the offspring of both sexes to a higher prevalence of augmented fed blood glucose values. SIGNIFICANCE: These results give validity for the use of GC as anti-inflammatory purposes in this critical periconceptional period, but highlight the importance to consider all parental habits when interpreting adult outcomes.
Assuntos
Dexametasona/administração & dosagem , Intolerância à Glucose/tratamento farmacológico , Homeostase , Secreção de Insulina/efeitos dos fármacos , Cuidado Pré-Concepcional , Animais , Glicemia/análise , Peso Corporal , Feminino , Glucocorticoides/administração & dosagem , Ilhotas Pancreáticas/efeitos dos fármacos , Ilhotas Pancreáticas/crescimento & desenvolvimento , Masculino , Estresse Oxidativo/efeitos dos fármacos , Gravidez , Prenhez , Ratos , Ratos WistarRESUMO
This chapter describes the propagation and characterization of transplantable insulinoma cells as model of insulin-producing pancreatic islet cells in the rat. Here, the cells are propagated by transplantation into rats followed by harvesting after growth for approximately 1 month. The cells are then purified by Percoll density gradient centrifugation and characterized by pulse-chase radiolabelling and immunoprecipitation of the insulin-related peptides. The results show that the transplantable insulinoma cells produce insulin in a manner similar to that found in normal pancreatic islets.
Assuntos
Técnicas de Cultura de Células/métodos , Imunoprecipitação/métodos , Insulinoma/patologia , Neoplasias Pancreáticas/genética , Animais , Proliferação de Células/genética , Humanos , Insulina/genética , Secreção de Insulina/genética , Insulinoma/genética , Ilhotas Pancreáticas/crescimento & desenvolvimento , Ilhotas Pancreáticas/patologia , Neoplasias Pancreáticas/patologia , RatosRESUMO
During maturation, pancreatic islets achieve their full capacity to secrete insulin in response to glucose, undergo morphological changes in which alpha-cells decrease and beta-cell mass increases, and they acquire the normal alpha- and beta-cell proportion changes that are important for islet functions later in life. In rodents, the first week of postweaning is critical for islet maturation. Multiple studies have documented the detrimental effects of several conditions on pancreatic maturation; however, few studies have addressed the use of pharmacological agents to enhance islet maturation. Biotin might have a potential action on islet maturation. Pharmacological concentrations of biotin have been found to modify islet morphology and function. In a previous study, we found that mice fed a biotin-supplemented diet for 8 weeks after weaning showed an increase in basal and glucose stimulated insulin secretion, enlarged islet size, and modified islet structure. In the present study, we investigated the effect of biotin on maturation features during the first week postweaning. Female BALB/cAnN Hsd mice were fed a control or a biotin-supplemented diet for 1 week after weaning. Compared with the control, biotin-supplemented mice showed an increase in pancreatic islet number and area in addition to an augmented proportion of beta-cells in the islet. These effects were related to an increase in beta-cell proliferation. No differences were found in insulin secretion, blood glucose concentrations, or serum insulin levels. These results indicate that biotin supplementation is capable of affecting beta-cell proliferation and might be a therapeutic agent for establishing strategies for regenerative medicine.
Assuntos
Biotina/administração & dosagem , Diferenciação Celular , Proliferação de Células , Suplementos Nutricionais , Células Secretoras de Insulina/citologia , Ilhotas Pancreáticas/crescimento & desenvolvimento , Complexo Vitamínico B/administração & dosagem , Animais , Apoptose , Biotina/efeitos adversos , Biotina/metabolismo , Biotina/uso terapêutico , Glicemia/análise , Contagem de Células , Suplementos Nutricionais/efeitos adversos , Feminino , Insulina/sangue , Insulina/metabolismo , Secreção de Insulina , Células Secretoras de Insulina/metabolismo , Ilhotas Pancreáticas/citologia , Ilhotas Pancreáticas/metabolismo , Camundongos Endogâmicos BALB C , Tamanho do Órgão , Concentração Osmolar , Estado Pré-Diabético/prevenção & controle , Distribuição Aleatória , Técnicas de Cultura de Tecidos , Complexo Vitamínico B/efeitos adversos , Complexo Vitamínico B/metabolismo , Complexo Vitamínico B/uso terapêutico , DesmameRESUMO
A maternal low-protein (LP) diet programs fetal pancreatic islet ß-cell development and function and predisposes offspring to metabolic dysfunction later in life. We hypothesized that maternal protein restriction during pregnancy differentially alters ß- and α-cell populations in offspring by modifying islet ontogeny and function throughout life. We aimed to investigate the effect of an LP maternal diet on pancreatic islet morphology and cellular composition in female offspring on postnatal days (PNDs) 7, 14, 21, 36, and 110. Mothers were divided into 2 groups: during pregnancy, the control group (C) was fed a diet containing 20% casein, and the LP group was fed an isocaloric diet with 10% casein. Offspring pancreases were obtained at each PND and then processed. ß and α cells were detected by immunohistochemistry, and cellular area and islet size were quantified. Islet cytoarchitecture and total area were similar in C and LP offspring at all ages studied. At the early ages (PNDs 7-21), the proportion of ß cells was lower in LP than C offspring. The proportion of α cells was lower in LP than C offspring on PND 14 and higher on PND 21. The ß/α-cell ratio was lower in LP compared with C offspring on PNDs 7 and 21 and higher on PND 36 (being similar on PNDs 14 and 110). We concluded that maternal protein restriction during pregnancy modifies offspring islet cell ontogeny by altering the proportions of islet sizes and by reducing the number of ß cells postnatally, which may impact pancreatic function in adult life.
Assuntos
Dieta com Restrição de Proteínas/efeitos adversos , Pâncreas/crescimento & desenvolvimento , Fenômenos Fisiológicos da Nutrição Animal , Animais , Feminino , Células Secretoras de Glucagon/citologia , Células Secretoras de Insulina/citologia , Células Secretoras de Insulina/fisiologia , Ilhotas Pancreáticas/citologia , Ilhotas Pancreáticas/crescimento & desenvolvimento , Lactação , Fenômenos Fisiológicos da Nutrição Materna , Gravidez , Efeitos Tardios da Exposição Pré-Natal , Ratos , Ratos Wistar , Maturidade Sexual , DesmameRESUMO
Adult mice lacking functional GABAB receptors (GABAB1KO) have glucose metabolism alterations. Since GABAB receptors (GABABRs) are expressed in progenitor cells, we evaluated islet development in GABAB1KO mice. Postnatal day 4 (PND4) and adult, male and female, GABAB1KO, and wild-type littermates (WT) were weighed and euthanized, and serum insulin and glucagon was measured. Pancreatic glucagon and insulin content were assessed, and pancreas insulin, glucagon, PCNA, and GAD65/67 were determined by immunohistochemistry. RNA from PND4 pancreata and adult isolated islets was obtained, and Ins1, Ins2, Gcg, Sst, Ppy, Nes, Pdx1, and Gad1 transcription levels were determined by quantitative PCR. The main results were as follows: 1) insulin content was increased in PND4 GABAB1KO females and in both sexes in adult GABAB1KOs; 2) GABAB1KO females had more clusters (<500 µm(2)) and less islets than WT females; 3) cluster proliferation was decreased at PND4 and increased in adult GABAB1KO mice; 4) increased ß-area at the expense of the α-cell area was present in GABAB1KO islets; 5) Ins2, Sst, and Ppy transcription were decreased in PND4 GABAB1KO pancreata, adult GABAB1KO female islets showed increased Ins1, Ins2, and Sst expression, Pdx1 was increased in male and female GABAB1KO islets; and 6) GAD65/67 was increased in adult GABAB1KO pancreata. We demonstrate that several islet parameters are altered in GABAB1KO mice, further pinpointing the importance of GABABRs in islet physiology. Some changes persist from neonatal ages to adulthood (e.g., insulin content in GABAB1KO females), whereas other features are differentially regulated according to age (e.g., Ins2 was reduced in PND4, whereas it was upregulated in adult GABAB1KO females).
Assuntos
Resistência à Insulina/fisiologia , Ilhotas Pancreáticas/fisiologia , Receptores de GABA-B/deficiência , Animais , Animais Recém-Nascidos , Peso Corporal/fisiologia , Feminino , Regulação da Expressão Gênica , Glucagon/sangue , Glucagon/genética , Glucagon/fisiologia , Glutamato Descarboxilase/fisiologia , Insulina/sangue , Insulina/genética , Insulina/fisiologia , Ilhotas Pancreáticas/crescimento & desenvolvimento , Ilhotas Pancreáticas/metabolismo , Ilhotas Pancreáticas/ultraestrutura , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Knockout , Tamanho do Órgão/fisiologia , Antígeno Nuclear de Célula em Proliferação/análise , Antígeno Nuclear de Célula em Proliferação/fisiologia , RNA/química , RNA/genética , Reação em Cadeia da Polimerase em Tempo RealRESUMO
OBJECTIVES: To study the chronological appearance of pancreatic islet neogenesis-associated protein (INGAP)-positive cells and its correlation with the increase in ß-cell mass and function in fetal and neonatal rats. METHODS: Normal Wistar rat embryos (E) at gestational days 15, 17, and 19 (E15, E17, E19) and 7-day-old postnatal rats (P7) were humanely killed to determine body and pancreas weight; blood glucose; glucose and arginine-induced insulin secretion; real-time polymerase chain reaction of Pdx1 and Ngn3; quantitative immunomorphometric analysis of ß-cell replication and apoptosis rate, cytokeratin and INGAP cell mass, and Pdx-1- and Ngn3-positive cells. RESULTS: Body and pancreas weight increased with age (P7 > E19 > E17 > E15; P < 0.05). Neonates had higher blood glucose concentrations than embryos (P < 0.05). We recorded a simultaneous and significant age-dependent trend of increase in the number of ß- and Pdx-1-positive cells, ß- and cytokeratin-positive cell mass and ß-cell capacity to release insulin in response to glucose and arginine, and decreased ß-cell apoptotic rate. These changes closely paralleled the increase in INGAP-positive cell mass. CONCLUSIONS: These findings suggest that INGAP exerts a positive modulatory effect on ß-cell mass and its secretory function in fetal and neonatal rats, thus becoming a new component in the multifactorial regulation of such processes.
Assuntos
Antígenos de Neoplasias/genética , Biomarcadores Tumorais/genética , Células Secretoras de Insulina/metabolismo , Insulina/metabolismo , Ilhotas Pancreáticas/metabolismo , Lectinas Tipo C/genética , Animais , Animais Recém-Nascidos , Antígenos de Neoplasias/metabolismo , Apoptose/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Biomarcadores Tumorais/metabolismo , Peso Corporal , Contagem de Células , Feminino , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Imuno-Histoquímica , Secreção de Insulina , Células Secretoras de Insulina/citologia , Ilhotas Pancreáticas/embriologia , Ilhotas Pancreáticas/crescimento & desenvolvimento , Queratinas/metabolismo , Lectinas Tipo C/metabolismo , Masculino , Morfogênese/genética , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Tamanho do Órgão , Proteínas Associadas a Pancreatite , Gravidez , Ratos , Ratos Wistar , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fatores de Tempo , Transativadores/genética , Transativadores/metabolismoRESUMO
AIMS/HYPOTHESIS: Cell-cell coupling mediated by gap junctions formed from connexin (CX) contributes to the control of insulin secretion in the endocrine pancreas. We investigated the cellular production and localisation of CX36 and CX43, and gap junction-mediated beta cell coupling in pancreatic islets from rats of different ages, displaying different degrees of maturation of insulin secretion. METHODS: The presence and distribution of islet connexins were assessed by immunoblotting and immunofluorescence. The expression of connexin genes was evaluated by RT-PCR and quantitative real-time PCR. The ultrastructure of gap junctions and the function of connexin channels were assessed by freeze-fracture electron microscopy and tracer microinjection, respectively. RESULTS: Young and adult beta cells, which respond to glucose, expressed significantly higher levels of Cx36 (also known as Gjd2) than fetal and newborn beta cells, which respond poorly to the sugar. Accordingly, adult beta cells also showed a significantly higher membrane density of gap junctions and greater intercellular exchange of ethidium bromide than newborn beta cells. Cx43 (also known as Gja1) was not expressed by beta cells, but was located in various cell types at the periphery of fetal and newborn islets. CONCLUSIONS/INTERPRETATION: These findings show that the pattern of connexins, gap junction membrane density and coupling changes in islets during the functional maturation of beta cells.
Assuntos
Conexinas/metabolismo , Células Secretoras de Insulina/metabolismo , Ilhotas Pancreáticas/metabolismo , Animais , Animais Recém-Nascidos , Conexina 43/genética , Conexina 43/metabolismo , Conexinas/genética , Feminino , Imunofluorescência , Junções Comunicantes/metabolismo , Immunoblotting , Células Secretoras de Insulina/ultraestrutura , Ilhotas Pancreáticas/crescimento & desenvolvimento , Ilhotas Pancreáticas/ultraestrutura , Masculino , Microscopia Eletrônica , Ratos , Ratos Wistar , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Proteína delta-2 de Junções ComunicantesRESUMO
Objetivos: revisar dados da literatura sobre isolamento de ilhotas pancreáticas para transplante e sobre as ações da frutose-1,6-bisfosfato. Fonte de dados: revisão de artigos publicados, a partir da pesquisa em bancos de dados nacionais e internacionais (SciELO, Lilacs, PubMed). Síntese dos dados: o transplante de ilhotas surge como uma alternativa para o tratamento do diabetes mellitus tipo 1. Entretanto, durante o processo de isolamento, há grande perda celular, principalmente na periferia da ilhota pancreática. As espécies reativas de oxigênio contribuem significativamente nesse processo, afetando a viabilidade das células para transplante. Vários esforços estão sendo feitos na tentativa de minimizar os danos causados pela liberação e produção destes compostos químicos. Conclusões: frente às importantes ações da frutose-1,6-bisfosfato descritas na literatura, seu emprego durante o processo de isolamento das ilhotas pancreáticas parece ser uma alternativa bastante atraente. O efeito da frutose-1,6-bisfosfato na redução da formação e liberação de radicais livres, assim como a sua ação citoprotetora, poderiam viabilizar um maior número de células, otimizando o processo de isolamento, além de auxiliar na enxertia, por diminuir a liberação de citocinas pró-inflamatórias.
Aims: To review the literature data about pancreatic islet isolation and fructose-1,6-bisphosfate. Source of data: Review of specific articles on the issue published in national and internacional databases (SciELO,Lilacs, PubMed). Summary of findings: Islets transplantation is an alternative for the treatment of type 1 diabetes mellitus. However, during the process of isolation, cell loss, mainly on the periphery of the pancreatic islet, ensues. Reactive oxygen species seem to contribute significantly in this process, affecting the viability of these cells. Various efforts are being made in an attempt to minimize the damage caused by the release and production of reactive oxygen species. Conclusions: Considering the important actions of fructose-1,6-bisphosphate which are described in the literature, its use in pancreatic islet isolation may represent an attractive alternative. The effect of fructose-1,6-bisphosphate in reducing the production and release of free radicals, as well as its role in cellular protection, could enable a greater number of viable cells, optimizing the isolation process, and also protecting the graft process, by reducing the release of proinflammatory cytokines.
Assuntos
Humanos , Masculino , Feminino , Diabetes Mellitus Tipo 1 , Frutose-Bifosfatase , Ilhotas Pancreáticas/crescimento & desenvolvimento , Transplante das Ilhotas PancreáticasRESUMO
BACKGROUND: Pancreatic islets are not fully developed at birth and it is not clear how they are vascularised and innervated. Nerve Growth Factor (NGF) is required to guide sympathetic neurons that innervate peripheral organs and also in cardiovascular system and ovary angiogenesis. Pancreatic beta cells of a transgenic mouse that over-expressed NGF in attracts sympathetic hyper-innervation towards them. Moreover, we have previously demonstrated that adult beta cells synthesize and secrete NGF; however, we do not know how is NGF secreted during development, nor if it might be trophic for sympathetic innervation and survival in the pancreas.We analyzed sympathetic innervation and vasculature development in rat pancreatic islets at different developmental stages; foetal (F19), early postnatal (P1), weaning period (P20) and adults. We temporarily correlated these events to NGF secretion by islet cells. RESULTS: Sympathetic fibres reached pancreatic islets in the early postnatal period, apparently following blood vessels. The maximal number of sympathetic fibres (TH immunopositive) in the periphery of the islets was observed at P20, and then fibres entered the islets and reached the core where beta cells are mainly located. The number of fibres decreased from that stage to adulthood. At all stages studied, islet cells secreted NGF and also expressed the high affinity receptor TrkA. Foetal and neonatal isolated islet cells secreted more NGF than adults. TrkA receptors were expressed at all stages in pancreatic sympathetic fibres and blood vessels. These last structures were NGF-immunoreactive only at early stages (foetal and P0). CONCLUSION: The results suggest that NGF signalling play an important role in the guidance of blood vessels and sympathetic fibres toward the islets during foetal and neonatal stages and could also preserve innervation at later stages of life.
Assuntos
Ilhotas Pancreáticas/inervação , Sistema Nervoso Simpático/crescimento & desenvolvimento , Sistema Nervoso Simpático/fisiologia , Animais , Animais Recém-Nascidos , Células Cultivadas , Feminino , Feto , Imunofluorescência , Regulação da Expressão Gênica no Desenvolvimento , Glucagon/metabolismo , Insulina/metabolismo , Ilhotas Pancreáticas/embriologia , Ilhotas Pancreáticas/crescimento & desenvolvimento , Ilhotas Pancreáticas/metabolismo , Masculino , Microscopia Confocal , Modelos Biológicos , Fatores de Crescimento Neural/metabolismo , Gravidez , Ratos , Ratos Wistar , Receptor trkA/metabolismo , Vimentina/metabolismoRESUMO
Function and structure of adult pancreatic islets are determined by early postnatal development, which in rats corresponds to the first month of life. We analyzed changes in blood glucose and hormones during this stage and their association with morphological and functional changes of alpha and beta cell populations during this period. At day 20 (d20), insulin and glucose plasma levels were two- and six-fold higher, respectively, as compared to d6. Interestingly, this period is characterized by physiological hyperglycemia and hyperinsulinemia, where peripheral insulin resistance and a high plasmatic concentration of glucagon are also observed. These functional changes were paralleled by reorganization of islet structure, cell mass and aggregate size of alpha and beta cells. Cultured beta cells from d20 secreted the same amount of insulin in 15.6 mM than in 5.6 mM glucose (basal conditions), and were characterized by a high basal insulin secretion. However, beta cells from d28 were already glucose sensitive. Understanding and establishing morphophysiological relationships in the developing endocrine pancreas may explain how events in early life are important in determining adult islet physiology and metabolism.
Assuntos
Insulina/metabolismo , Ilhotas Pancreáticas/crescimento & desenvolvimento , Ilhotas Pancreáticas/metabolismo , Fatores Etários , Animais , Glicemia/metabolismo , Agregação Celular , Contagem de Células , Células Cultivadas , Dieta , Glucagon/sangue , Células Secretoras de Glucagon/metabolismo , Células Secretoras de Glucagon/fisiologia , Insulina/sangue , Resistência à Insulina/fisiologia , Secreção de Insulina , Células Secretoras de Insulina/metabolismo , Células Secretoras de Insulina/fisiologia , Ilhotas Pancreáticas/citologia , Ilhotas Pancreáticas/fisiologia , Masculino , Ratos , Ratos Wistar , DesmameRESUMO
Cell-cell contacts mediated by intercellular junctions are crucial for proper insulin secretion in the endocrine pancreas. The biochemical composition of the intercellular junctions in this organ and the role of junctional proteins in endocrine pancreatic dysfunctions are still unclear. In this study, we investigated the expression and cellular location of junctional and cytoskeletal proteins in cultured neonatal rat pancreatic islets. Neonatal B-cells had an impaired insulin secretion compared to adult cells. Cultured neonatal islets showed a time-dependent increase in the glucose-induced secretory response. The maturation of B-cells in vitro was accompanied by upregulation of the expression of some junctional proteins in islet cells. Neonatal islets cultured for only 24 h showed a low expression and a diffuse cytoplasmic location of the tight junctional proteins occludin and ZO-1 and of the adherens junctional proteins alpha- and beta-catenins, as demonstrated by immunoblotting and immunocytochemistry. Culturing islets for up to 8 days significantly increased the cell expression of these junctional proteins but not of the cytoskeletal proteins vinculin and alpha-actinin. A translocation of ZO-1 and catenins to the cell-cell contact region, as well as a higher association of F-actin with the intercellular junction, were also observed in neonatal islets following prolonged culturing. ZO-1 and beta-catenin were immunolocated in the endocrine pancreas of adult rats indicating that these junctional proteins are also expressed in this organ in situ. In conclusion, endocrine pancreatic cells express several junctional proteins that are upregulated following differentiation of the endocrine pancreas in vitro.
Assuntos
Junções Aderentes/metabolismo , Ilhotas Pancreáticas/citologia , Ilhotas Pancreáticas/metabolismo , Proteínas de Membrana/metabolismo , Junções Íntimas/metabolismo , Regulação para Cima , Junções Aderentes/química , Animais , Animais Recém-Nascidos , Linfócitos B/citologia , Linfócitos B/fisiologia , Adesão Celular , Células Cultivadas , Feminino , Imuno-Histoquímica , Insulina/metabolismo , Ilhotas Pancreáticas/crescimento & desenvolvimento , Masculino , Ratos , Ratos Wistar , Junções Íntimas/químicaRESUMO
Ponderal, morphometric and morphological assessments were used to study the Syrian golden hamster pancreas development during the first 70 days of postnatal life. The body mass increased 41.74 times in a single growth phase and a mean duplication time calculated by linear equation y = 1.76 x - 1.87 (r2 = 0.95), was 13.4 days. The pancreatic mass increased 44.60 times in two growth phases, the first from 2 to 21 days and the second from 28 to 70 days of age. The exponential equation obtained by regression analysis for these periods, were: y = 5.21. e (0.1810.x) (r2 = 0.95) and y = 156.64. e(0.0094.x (r2 = 0.72), respectively, and the calculated duplication times were: 3.8 and 73.7 days, respectively. This marked pancreatic growth was due to the increase in all theirs morphological compartments, especially of the acini. An inverse relationship was observed in the volume density evolution between the acini and the stroma, with a 2.30 times increase in the fraction of pancreatic volume occupied by the acini and a 0.26 times reduction in the connective tissue spaces during studied period. The volume density of pancreatic islets increased 4.47 times from 21 to 35 days of age. The morphological analysis showed a significant increase in the height and width of the acinar cells and in the size of the acini especially from 14 to 21 days of age, a relative reduction in the stromal volume, an increase in the size of the pancreatic islets and the end of parenchymal cell maturation and lobar and lobular organization, so glandular maturity was obtained.
Assuntos
Envelhecimento/fisiologia , Diferenciação Celular/fisiologia , Mesocricetus/anatomia & histologia , Mesocricetus/crescimento & desenvolvimento , Pâncreas/citologia , Pâncreas/crescimento & desenvolvimento , Animais , Animais Recém-Nascidos , Peso Corporal/fisiologia , Tamanho Celular/fisiologia , Cricetinae , Glândulas Exócrinas/citologia , Glândulas Exócrinas/crescimento & desenvolvimento , Glândulas Exócrinas/fisiologia , Ilhotas Pancreáticas/citologia , Ilhotas Pancreáticas/crescimento & desenvolvimento , Ilhotas Pancreáticas/fisiologia , Masculino , Mesocricetus/fisiologia , Tamanho do Órgão/fisiologia , Pâncreas/fisiologiaRESUMO
The presence of thioredoxin peroxidase (TPx), also known as thiol specific antioxidant (TSA), was investigated in neonatal and adult rat islets, and in the beta-cell line HIT-T15. Western blotting of extracts from neonatal and adult pancreatic islets and from the tumoral cell line HIT-T15 revealed the presence of a 25 kDa protein that comigrated with purified yeast TPx. Endocrine pancreatic TPx accounted for approximately 0.01% of the total protein content. Treatment with H2O2 for 3 h increased the expression of TPx in HIT-T15 cells. The distribution of TPx throughout the islet cells was confirmed by immunocytochemistry. Since pancreatic beta-cells possess a weak antioxidant enzyme defense system, especially with regard to hydrogen peroxidase-decomposing enzymes, the presence of a TPx analog in islets suggests that this enzyme may play a role in protecting pancreatic cells against reactive oxygen species.
Assuntos
Ilhotas Pancreáticas/enzimologia , Proteínas de Neoplasias , Peroxidases/metabolismo , Envelhecimento , Animais , Animais Recém-Nascidos , Células Cultivadas , Insulinoma , Ilhotas Pancreáticas/citologia , Ilhotas Pancreáticas/crescimento & desenvolvimento , Estresse Oxidativo/fisiologia , Neoplasias Pancreáticas , Peroxirredoxinas , Ratos , Ratos Wistar , Células Tumorais CultivadasRESUMO
OBJECTIVE: To review the literature on beta-cell neogenesis and regeneration, with special interest in substances that regulate such processes. DESIGN: Representative papers were selected through a computer MEDLINE search from 1990 to 2000. RESULTS: Several studies showed that once islets of Langerhans developed from small pancreatic ducts, this process did not continue in normal adult individuals. However, it has been published that new beta-cell formation can occur in vivo in certain experimental models through neogenesis, in which gene pax 4 is extremely important. On the other hand, substances that stimulate the regenerative process of beta-cells include glucose, several hormones and certain growth factors. CONCLUSIONS: Substances that stimulate the regenerative process commonly express this effect in elevated, non-physiologic concentrations; thus, their possible therapeutic importance is not yet clear. Nevertheless, the Reg protein, present in regenerative pancreas and implied in neogenesis process, has actual possibilities of becoming therapeutically important.
Assuntos
Ilhotas Pancreáticas/citologia , Ilhotas Pancreáticas/crescimento & desenvolvimento , Animais , Divisão Celular/efeitos dos fármacos , Glucose/farmacologia , Hormônio do Crescimento/farmacologia , Substâncias de Crescimento/farmacologia , Proteínas de Homeodomínio , Humanos , Lectinas/farmacologia , Fatores de Transcrição Box Pareados , Prolactina/farmacologia , Fatores de TranscriçãoRESUMO
Maternal malnutrition was shown to affect early growth and leads to permanent alterations in insulin secretion and sensitivity of offspring. In addition, epidemiological studies showed an association between low birth weight and glucose intolerance in adult life. To understand these interactions better, we investigated the insulin secretion by isolated islets and the early events related to insulin action in the hind-limb muscle of adult rats fed a diet of 17% protein (control) or 6% protein [low (LP) protein] during fetal life, suckling and after weaning, and in rats receiving 6% protein during fetal life and suckling followed by a 17% protein diet after weaning (recovered). The basal and maximal insulin secretion by islets from rats fed LP diet and the basal release by islets from recovered rats were significantly lower than that of control rats. The dose-response curves to glucose of islets from LP and recovered groups were shifted to the right compared to control islets, with the half-maximal response (EC50) occurring at 16.9 +/- 1.3, 12.4 +/- 0.5 and 8.4 +/- 0.1 mmol/L, respectively. The levels of insulin receptor, as well as insulin receptor substrate-1 and phosphorylation and the association between insulin receptor substrate-1 and phosphatidylinositol 3-kinase were greater in rats fed a LP diet than in control rats. In recovered rats, these variables were not significantly different from those of the other two groups. These results suggest that glucose homeostasis is maintained in LP and recovered rats by an increased sensitivity to insulin as a result of alterations in the early steps of the insulin signal transduction pathway.