RESUMEN
BACKGROUND: Pharmacology has provided efficient tools to improve insulin effect/secretion but the decrease in ß-cell mass remains elusive. INGAP-PP could provide a therapeutic alternative to meet that challenge. AIM: To further understand the mechanism that links INGAP-PP effects upon ß-cell mass and function with islet angiogenesis. METHODOLOGY: Normal male Wistar rats were divided into 2 groups and injected with a single dose of 100 mg/Kg suramin or saline. Both groups were divided into 2 subgroups that received daily doses of 2 mg/kg INGAP-PP or saline for ten days. Plasma glucose, triacylglycerol, TBARS, and insulin levels were measured. Pancreas immunomorphometric analyses were also performed. Pancreatic islets were isolated to measure glucose-stimulated insulin secretion (GSIS). Specific islet mRNA levels were studied by qRT-PCR. Statistical analysis was done using ANOVA. RESULTS: No differences were recorded in body weight, food intake, or any other plasma parameter measured in all groups. Islets from INGAP-PP-treated rats significantly increased GSIS, ß-cell mass, and mRNA levels of Bcl-2, Ngn-3, VEGF-A, VEGF-R2, CD31, Ang1 and Ang2, Laminin ß-1, and Integrin ß-1, and decreased mRNA levels of Caspase-8, Bad, and Bax. Islets from suramin-treated rats showed significant opposite effects, but INGAPP-PP administration rescued most of the suramin effects in animals treated with both compounds. CONCLUSION: Our results reinforce the concept that INGAP-PP enhances insulin secretion and ß-cell mass, acting through PI3K/Akt/mTOR pathways and simultaneously activating angiogenesis through HIF-1α-mediated VEGF-A secretion. Therefore, INGAP-PP might be a suitable antidiabetic agent able to overcome two major alterations present in T2D.
Asunto(s)
Citocinas/farmacología , Regulación de la Expresión Génica/efectos de los fármacos , Subunidad alfa del Factor 1 Inducible por Hipoxia/metabolismo , Células Secretoras de Insulina/metabolismo , Fragmentos de Péptidos/farmacología , Transducción de Señal/efectos de los fármacos , Factor A de Crecimiento Endotelial Vascular/biosíntesis , Animales , Diabetes Mellitus Tipo 2/tratamiento farmacológico , Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/patología , Células Secretoras de Insulina/patología , Masculino , Fosfatidilinositol 3-Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Ratas , Ratas Wistar , Serina-Treonina Quinasas TOR/metabolismoRESUMEN
The aim of the present study was to test the possible presence and expression of islet neogenesis-associated protein (INGAP) in islet cells of normal adult hamsters. Pancreata from normal male Syrian hamsters were removed to perform the following studies. (i) Western blot analysis using the cytosolic fraction from homogenates of isolated islets, exocrine tIssue and whole pancreas, and rabbit INGAP-specific antibody. (ii) Immunohistochemical identification of INGAP-positive cells in fixed sections of intact pancreata, fresh and 72 h cultured islets (isolated by collagenase digestion), and smears of exocrine pancreatic cells, using the same INGAP-specific antibody and streptavidin-biotin complex. (iii) RT-PCR using total RNA extracted from isolated islets and from exocrine tIssue as template, and a specific pair of primers. (iv) Control of the sequence of the PCR products. INGAP protein was identified by Western blot in the cytosolic fraction of homogenates from fresh isolated islets, exocrine cells and whole fresh pancreas. INGAP-immunopositive cells were observed in duct, exocrine and islet cells in either fixed intact or digested pancreatic tIssue. INGAP mRNA was identified in samples of total RNA from fresh and cultured isolated islets and from exocrine cells. Our data demonstrate that INGAP is present and expressed in islets and in exocrine pancreatic cells of normal hamsters. The ubiquitous localization of INGAP suggests its possible role in the physiological process of islet growth and its protective effect upon streptozotocin-induced diabetes.
Asunto(s)
Antígenos de Neoplasias , Biomarcadores de Tumor , Islotes Pancreáticos/química , Lectinas Tipo C , Proteínas/análisis , Animales , Western Blotting/métodos , Células Cultivadas , Cricetinae , Citosol/química , Inmunohistoquímica/métodos , Masculino , Mesocricetus , Páncreas/química , Páncreas/citología , Proteínas Asociadas a Pancreatitis , Proteínas/genética , ARN Mensajero/análisis , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
The aim of this work was to study the possible relationship between pancreatic duodenal homeobox-1 (Pdx-1) and islet neogenesis-associated protein (INGAP) during induced islet neogenesis. Pregnant hamsters were fed with (S) and without (C) sucrose, and glycemia, insulin secretion in vitro, and pancreas immunomorphometric parameters were measured in their 7-day-old offspring. S offspring had significantly lower glycemic levels than C animals. Insulin release in response to increasing glucose concentrations in the incubation medium (2-16 mM glucose) did not increase in pancreata from either C or S offspring. However, pancreata from S offspring released more insulin than those from C animals. In S offspring, beta-cell mass, beta-cell replication rate and islet neogenesis increased significantly, with a simultaneous decrease in beta-cell apoptotic rate. INGAP- and Pdx-1-positive cell mass also increased in the islets and among acinar and duct cells. We found two subpopulations of Pdx-1 cells: INGAP-positive and INGAP-negative. Pdx-1/INGAP-positive cells did not stain with insulin, glucagon, somatostatin, pancreatic polypeptide, or neurogenin 3 antibodies. The increment of Pdx-1/INGAP-positive cells represented the major contribution to the Pdx-1 cell mass increase. Such increments varied among pancreas subsectors: ductal>insular>extrainsular. Our results suggested that INGAP participates in the regulation of islet neogenesis, and Pdx-1/INGAP-positive cells represent a new stem cell subpopulation at an early stage of development, highly activateable in neogenesis.
Asunto(s)
Antígenos de Neoplasias , Biomarcadores de Tumor , Proteínas de Homeodominio , Lectinas Tipo C , Páncreas/metabolismo , Proteínas/análisis , Células Madre/metabolismo , Transactivadores/análisis , Animales , Animales Recién Nacidos , Apoptosis , Biomarcadores/análisis , Peso Corporal , Cricetinae , Femenino , Inmunohistoquímica/métodos , Insulina/metabolismo , Secreción de Insulina , Islotes Pancreáticos/citología , Islotes Pancreáticos/metabolismo , Páncreas/citología , Proteínas Asociadas a Pancreatitis , EmbarazoRESUMEN
We perform a systematic experimental study of the influence of the type of base on the avalanche dynamics of slowly driven 1D ball piles. The control of base details allows us to explore a wide spectrum of pile structures and dynamics. The scaling properties of the observed avalanche distributions suggest that self-organized critical behavior is approached as the "base-induced" disorder at the pile profile increases.
RESUMEN
The aim of this work was to demonstrate the possible direct effect of several hormones upon glucose-induced insulin secretion in amphibians. Hence, pancreas pieces of Bufo arenarum were incubated for 60 min at 25 degrees with 2 and 8 mM glucose plus the addition of hormones known to affect insulin secretion in mammals, measuring the release of insulin by radioimmunoassay. Glucagon (1 microM), ACTH (2.5 microM), human and bovine growth hormone (4.6 and 2.1 microM), prolactin (0.27 microM), corticosterone (0.4 microM), androstanolone (10(-2) microM), estradiol and estrone (10 microM), triiodothyronine and thyroxine (1 microM) enhanced significantly the glucose-induced insulin secretion. Androstanolone, human and bovine growth hormone, triiodothyronine and thyroxine only exerted such effect in the presence of 8 mM glucose. Conversely, somatostatin (1 microM), adrenalin (1 microM), clonidine (2 microM), dexamethasone (0.4 microM), and 2-hydroxyestradiol (5 microM) decreased significantly the glucose-induced insulin release. However, the effect of somatostatin was only apparent in the presence of high glucose. The direct effect of all these hormones--tested for the first time in the amphibian pancreas--was similar to that described in the mammalian pancreas, thus suggesting that such hormones might participate, at least in vitro, in the fine-tuning of insulin secretion in amphibians.