RESUMEN
Guanosine is a purinergic nucleoside that has been shown to have neuroprotective effects, mainly through its ability to modulate the glutamatergic system. An increase in pro-inflammatory cytokine levels triggers the activation of the enzyme indoleamine 2,3-dioxygenase 1 (IDO-1), leading to glutamatergic excitotoxicity, which has important roles in the pathophysiology of depression. The aim of this study was to investigate the possible antidepressant-like effects and underlying mechanisms of action of guanosine against lipopolysaccharide (LPS)-induced depression in a mouse model. Mice were orally pre-treated with saline (0.9% NaCl), guanosine (8 or 16 mg/kg), or fluoxetine (30 mg/kg) for 7 days before LPS (0.5 mg/kg, intraperitoneal) injection. One day after LPS injection, mice were subjected to the forced swim test (FST), tail suspension test (TST), and open field test (OFT). After the behavioral tests, mice were euthanized and the levels of tumor necrosis factor-α (TNF-α), IDO-1, glutathione, and malondialdehyde in the hippocampus were measured. Pretreatment with guanosine was able to prevent LPS- induced depressive-like behaviors in the TST and FST. In the OFT, no locomotor changes were observed with any treatment. Both guanosine (8 and 16 mg/kg/day) and fluoxetine treatment prevented the LPS-induced increase in TNF-α and IDO expression and lipid peroxidation as well as decrease of reduced glutathione levels in the hippocampus. Taken together, our findings suggest that guanosine may have neuroprotective effects against LPS-induced depressive-like behavior through preventing oxidative stress and the expression of IDO-1 and TNF-α in the hippocampus.
Asunto(s)
Depresión , Fármacos Neuroprotectores , Ratones , Animales , Depresión/inducido químicamente , Depresión/tratamiento farmacológico , Depresión/metabolismo , Lipopolisacáridos/farmacología , Fluoxetina/farmacología , Factor de Necrosis Tumoral alfa/metabolismo , Guanosina/farmacología , Fármacos Neuroprotectores/farmacología , Conducta Animal , Hipocampo/metabolismoRESUMEN
NEW FINDINGS: What is the central question of this study? Does protein restriction in early life modify glucose-induced insulin secretion by altering [Ca2+ ]i and the expression of SNARE proteins in pancreatic islets from pregnant rats? What is the main finding and its importance? Protein restriction in early life increased the first phase of glucose-induced insulin secretion and [Ca2+ ]i without altering the expression of SNARE proteins during pregnancy. This finding contributes to our understanding of the mechanisms of altered insulin secretion and might provide new perspectives for the development of therapeutic tools for gestational diabetes. ABSTRACT: We investigated the kinetics of glucose-induced insulin secretion and their relationship with [Ca2+ ]i and the expression of protein from exocytotic machinery in islets from recovered pregnant and long-term protein-deficient pregnant rats. Isolated islets were evaluated from control-fed pregnant (CP), protein-deficient pregnant (DP), control-fed non-pregnant (CNP) and protein-deficient non-pregnant (DNP) female adult rats, and from protein-deficient pregnant (RP) and non-pregnant (RNP) rats that were recovered after weaning. The insulin responses to glucose during the first phase of secretion were higher in RP than in CP groups, and both were higher than in the DP group. Islets from RP rats displayed a rapid increase in insulin release (first phase), followed by a plateau that was maintained thereafter. The [Ca2+ ]i in islets from the protein-deficient groups was lower than in the control groups, and both were lower than in the RP and RNP groups. SNAP-25 was increased in islets from pregnant rats independently of their nutritional status, and the syntaxin-1A content was reduced in islets from the RP rats compared with the RNP rats. The VAMP2 content was similar among the groups. Thus, protein restriction during intrauterine life and lactation increased insulin secretion during pregnancy, attributable, in part, to increased [Ca2+ ]i , and independent of an alteration of expression of SNARE proteins.
Asunto(s)
Calcio/metabolismo , Dieta con Restricción de Proteínas/tendencias , Regulación del Desarrollo de la Expresión Génica , Secreción de Insulina/fisiología , Líquido Intracelular/metabolismo , Proteínas SNARE/biosíntesis , Animales , Glucemia/metabolismo , Femenino , Islotes Pancreáticos/metabolismo , Masculino , Embarazo , Ratas , Ratas Wistar , Proteínas SNARE/genéticaRESUMEN
PURPOSE: To evaluate the role of miR-124a in the regulation of genes involved in insulin exocytosis and its effects on the kinetics of insulin secretion in pancreatic islets from pregnant rats submitted to a low-protein diet. METHODS: Adult control non-pregnant (CNP) and control pregnant (CP) rats were fed a normal protein diet (17%), whereas low-protein non-pregnant (LPNP) and low-protein pregnant (LPP) rats were fed a low-protein diet (6%) from days 1 to 15 of pregnancy. Kinetics of the glucose-induced insulin release and measurement of [Ca2+]i in pancreatic islets were assessed by standard protocols. The miR-124a expression and gene transcriptions from pancreatic islets were determined by real-time polymerase chain reaction. RESULTS: In islets from LPP rats, the first phase of insulin release was abrogated. The AUC [Ca2+]i from the LPP group was lower compared with the other groups. miR-124a expression was reduced by a low-protein diet. SNAP-25 mRNA, protein expression, and Rab3A protein content were lower in the LPP rats than in CP rats. Syntaxin 1A and Kir6.2 mRNA levels were decreased in islets from low-protein rats compared with control rats, whereas their protein content was reduced in islets from pregnant rats. CONCLUSIONS: Loss of biphasic insulin secretion in islets from LPP rats appears to have resulted from reduced [Ca2+]i due, at least in part, to Kir6.2 underexpression and from the changes in exocytotic elements that are influenced either directly or indirectly by miR-124a.
Asunto(s)
Dieta con Restricción de Proteínas , Insulina/metabolismo , Islotes Pancreáticos/metabolismo , MicroARNs/metabolismo , Animales , Femenino , Glucosa , Masculino , Embarazo , Ratas , Ratas WistarRESUMEN
BACKGROUND: Gap junctions between ß-cells participate in the precise regulation of insulin secretion. Adherens junctions and their associated proteins are required for the formation, function and structural maintenance of gap junctions. Increases in the number of the gap junctions between ß-cells and enhanced glucose-stimulated insulin secretion are observed during pregnancy. In contrast, protein restriction produces structural and functional alterations that result in poor insulin secretion in response to glucose. We investigated whether protein restriction during pregnancy affects the expression of mRNA and proteins involved in gap and adherens junctions in pancreatic islets. An isoenergetic low-protein diet (6% protein) was fed to non-pregnant or pregnant rats from day 1-15 of pregnancy, and rats fed an isocaloric normal-protein diet (17% protein) were used as controls. RESULTS: The low-protein diet reduced the levels of connexin 36 and ß-catenin protein in pancreatic islets. In rats fed the control diet, pregnancy increased the levels of phospho-[Ser(279/282)]-connexin 43, and it decreased the levels of connexin 36, ß-catenin and beta-actin mRNA as well as the levels of connexin 36 and ß-catenin protein in islets. The low-protein diet during pregnancy did not alter these mRNA and protein levels, but avoided the increase of levels of phospho-[Ser(279/282)]-connexin 43 in islets. Insulin secretion in response to 8.3 mmol/L glucose was higher in pregnant rats than in non-pregnant rats, independently of the nutritional status. CONCLUSION: Short-term protein restriction during pregnancy prevented the Cx43 phosphorylation, but this event did not interfer in the insulin secretion.
Asunto(s)
Comunicación Celular/fisiología , Diabetes Gestacional/dietoterapia , Dieta con Restricción de Proteínas , Uniones Intercelulares/metabolismo , Islotes Pancreáticos/metabolismo , ARN Mensajero/metabolismo , Actinas/metabolismo , Uniones Adherentes/metabolismo , Análisis de Varianza , Animales , Glucemia/análisis , Conexina 43/metabolismo , Conexinas/metabolismo , Diabetes Gestacional/prevención & control , Femenino , Uniones Comunicantes/metabolismo , Glucosa/administración & dosificación , Insulina/metabolismo , Secreción de Insulina , Embarazo , Ratas Wistar , Reacción en Cadena en Tiempo Real de la Polimerasa , beta Catenina/metabolismo , Proteína delta-6 de Union ComunicanteRESUMEN
We investigated if whether intrauterine protein restriction in combination with overfeeding during lactation would cause adult-onset obesity and metabolic disorders. After birth, litters from dams fed with control (17% protein) and low protein (6% protein) diets were adjusted to a size of four (CO and LO groups, respectively) or eight (CC and LC groups, respectively) pups. All of the offspring were fed a diet containing 12% protein from the time of weaning until they were 90 d old. Compared to the CC and LC groups, the CO and LO groups had higher relative and absolute food intakes, oxygen consumption and carbon dioxide production; lower brown adipose tissue weight and lipid content and greater weight gain and absolute and relative white adipose tissue weight and absolute lipid content. Compared with the CO and CC rats, the LC and LO rats exhibited higher relative food intake, brown adipose tissue weight and lipid content, reduced oxygen consumption, carbon dioxide production and spontaneous activity, increased relative retroperitoneal adipose tissue weight and unaltered absolute white adipose tissue weight and lipid content. The fasting serum glucose was similar among the groups. The area under the glucose curve was higher in the LO and CO rats than in the LC and CC rats. The basal insulinemia and homeostasis model assessment of insulin resistance (HOMA-IR) were lower in the LO group than in the other groups. The total area under the insulin curve for the LO rats was similar to the CC rats, and both were lower than the CO and LC rats. Kitt was higher in the LO, LC and CO groups than in the CC group. Thus, intrauterine protein restriction followed by overfeeding during lactation did not induce obesity, but produced glucose intolerance by impairing pancreatic function in adulthood.
RESUMEN
Nutritional recovery with a soyabean diet decreases body and fat weights when compared with a casein diet. We investigated whether the reduced adiposity observed in rats recovering from early-life malnutrition with a soyabean diet results from alterations in lipid metabolism in white adipose tissue (WAT) and/or brown adipose tissue (BAT). Male rats from mothers fed either 17 or 6 % protein during pregnancy and lactation were maintained on 17 % casein (CC and LC groups), 17 % soyabean (CS and LS groups) or 6 % casein (LL group) diets over 60 d. The rats maintained on a soyabean diet had similar relative food intakes, but lower body and retroperitoneal WAT weights and a reduced lipid content in the retroperitoneal WAT. The insulin levels were lower in the recovered rats and were elevated in those fed a soyabean diet. Serum T3 concentration and uncoupling protein 1 content in the BAT were decreased in the recovered rats. The thermogenic capacity of the BAT was not affected by the soyabean diet. The lipogenesis rate in the retroperitoneal WAT was similar in all of the groups except for the LL group, which had exacerbated lipogenesis. The enhancement of the lipolysis rate by isoproterenol was decreased in white adipocytes from the soyabean-recovered rats and was elevated in adipocytes from the soyabean-control rats. Thus, in animals maintained on a soyabean diet, the proportions of fat deposits are determined by the lipolysis rate, which differs depending on the previous nutritional status.