RESUMO
In the present study, two approaches were followed to evaluate the metabolic responses of tambaqui (Colossoma macropomum), a frugivorous species, to intraperitoneal (IP) administration of glucose (GLU) and fructose (FRU) in fed (FED) and 10-day fasted (FAST) fish. Glucose and fructose tolerance tests were performed to assess the carbohydrate utilization and complementary NMR-metabolomics analyses were done to elucidate the impacts of sugar mobilization on the metabolic profile of plasma, liver and muscle. Blood was sampled from FED groups at 0, 3, 6 and 24 h; and at 0 and 24 h from FAST groups. Significant differences were observed in the hyperglycaemic peak between sugars at 3 h (GLU - 13.7 ± 2.0 mM vs. FRU - 8.7 ± 1.1 mM; saline 6.3 ± 0.6 mM) and on the return to normoglycaemia (GLU - 8.5 ± 2.2 mM vs. FRU - 5.2 ± 0.9 mM; saline 4.9 ± 0.6 mM) 6 h after IP on the FRU fish. The NMR-metabolomics approach allowed to conclude that tambaqui seems to be more responsive to the feeding regime (FED vs. FAST) than to the injected sugar (FRU vs. GLU). From the studied tissues, plasma showed no significant variations between feeding regimes at 24 h after IP, while muscle and liver revealed some variations on the final metabolome profile between FED and FAST groups. The metabolome variations between feeding regimes are indicative of changes on the amino acid utilization. Fish from FAST group seem to utilize amino acids as energy source rather than for protein synthesis and muscle growth. Variations on glucose concentration in muscle can also indicate different utilization of the sugars depending on the feeding regime.
Assuntos
Caraciformes , Frutas , Aminoácidos , Animais , Caraciformes/fisiologia , Frutose , Glucose , Metabolômica , AçúcaresRESUMO
Glutathione S-transferases are a family of detoxifying enzymes that catalyze the conjugation of reduced glutathione (GSH) with different xenobiotic compounds using either Ser, Tyr, or Cys as a primary catalytic residue. We identified a novel GST in the genome of the shrimp pathogen V. parahaemolyticus FIM- S1708+, a bacterial strain associated with Acute Hepatopancreatic Necrosis Disease (AHPND)/Early Mortality Syndrome (EMS) in cultured shrimp. This new GST class was named Gtt2. It has an atypical catalytic mechanism in which a water molecule instead of Ser, Tyr, or Cys activates the sulfhydryl group of GSH. The biochemical properties of Gtt2 from Vibrio parahaemolyticus (VpGSTT2) were characterized using kinetic and crystallographic methods. Recombinant VpGSTT2 was enzymatically active using GSH and CDNB as substrates, with a specific activity of 5.7 units/mg. Low affinity for substrates was demonstrated using both Michaelis-Menten kinetics and isothermal titration calorimetry. The crystal structure showed a canonical two-domain structure comprising a glutathione binding G-domain and a hydrophobic ligand H domain. A water molecule was hydrogen-bonded to residues Thr9 and Ser 11, as reported for the yeast Gtt2, suggesting a primary role in the reaction. Molecular docking showed that GSH could bind at the G-site in the vicinity of Ser11. G-site mutationsT9A and S11A were analyzed. S11A retained 30% activity, while T9A/S11A showed no detectable activity. VpGSTT2 was the first bacterial Gtt2 characterized, in which residues Ser11 and Thr9 coordinated a water molecule as part of a catalytic mechanism that was characteristic of yeast GTT2. The GTT2 family has been shown to provide protection against metal toxicity; in some cases, excess heavy metals appear in shrimp ponds presenting AHPND/EMS. Further studies may address whether GTT2 in V. parahaemolyticus pathogenic strains may provide a competitive advantage as a novel detoxification mechanism.
Assuntos
Glutationa Transferase/genética , Penaeidae/microbiologia , Vibrio parahaemolyticus/genética , Animais , Genoma , Filogenia , Análise de SequênciaRESUMO
OBJECTIVE: Recent data show that iNOS has an essential role in ER stress in obesity. However, whether iNOS is sufficient to account for obesity-induced ER stress and Unfolded Protein Response (UPR) has not yet been investigated. In the present study, we used iNOS knockout mice to investigate whether high-fat diet (HFD) can still induce residual ER stress-associated insulin resistance. METHODS: For this purpose, we used the intraperitoneal glucose tolerance test (GTT), euglycemic-hyperinsulinemic clamp, western blotting and qPCR in liver, muscle, and adipose tissue of iNOS KO and control mice on HFD. RESULTS: The results of the present study demonstrated that, in HFD fed mice, iNOS-induced alteration in insulin signaling is an essential mechanism of insulin resistance in muscle, suggesting that iNOS may represent an important target that could be blocked in order to improve insulin sensitivity in this tissue. However, in liver and adipose tissue, the insulin resistance induced by HFD was only partially dependent on iNOS, and, even in the presence of genetic or pharmacological blockade of iNOS, a clear ER stress associated with altered insulin signaling remained evident in these tissues. When this ER stress was blocked pharmacologically, insulin signaling was improved, and a complete recovery of glucose tolerance was achieved. CONCLUSIONS: Taken together, these results reinforce the tissue-specific regulation of insulin signaling in obesity, with iNOS being sufficient to account for insulin resistance in muscle, but in liver and adipose tissue ER stress and insulin resistance can be induced by both iNOS-dependent and iNOS-independent mechanisms.
Assuntos
Estresse do Retículo Endoplasmático/fisiologia , Óxido Nítrico Sintase Tipo II/antagonistas & inibidores , Tecido Adiposo/metabolismo , Animais , Glicemia/metabolismo , Dieta Hiperlipídica , Gorduras na Dieta/metabolismo , Insulina/genética , Resistência à Insulina/fisiologia , Fígado/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Óxido Nítrico Sintase Tipo II/deficiência , Óxido Nítrico Sintase Tipo II/genética , Óxido Nítrico Sintase Tipo II/metabolismo , Obesidade/genética , Transdução de Sinais/fisiologia , Resposta a Proteínas não DobradasRESUMO
Overweight and obesity have become epidemic worldwide and are linked to sedentary lifestyle and the consumption of processed foods and drinks. Citrate is a metabolite that plays central roles in carbohydrate and lipid metabolism. In addition, citrate is the additive most commonly used by the food industry, and therefore is highly consumed. Extracellular citrate can freely enter the cells via the constitutively expressed plasma membrane citrate transporter. Within the cytosol, citrate is readily metabolised by ATP-citrate lyase into acetyl-CoA - the metabolic precursor of endogenously produced lipids and cholesterol. We therefore hypothesised that the citrate ingested from processed foods and drinks could contribute to increased postprandial fat production and weight gain. To test our hypothesis, we administered citrate to mice through their drinking water with or without sucrose and monitored their weight gain and other metabolic parameters. Our results showed that mice receiving citrate or citrate+sucrose did not show increased weight gain or an increase in the weight of the liver, skeletal muscles or adipose tissues (AT). Moreover, the plasma lipid profiles (TAG, total cholesterol, LDL and HDL) were similar across all groups. However, the group receiving citrate+sucrose showed augmented fasting glycaemia, glucose intolerance and the expression of pro-inflammatory cytokines (TNF-α, IL-1ß, IL-6 and IL-10) in their AT. Therefore, our results suggest that citrate consumption contributes to increased AT inflammation and altered glucose metabolism, which is indicative of initial insulin resistance. Thus, citrate consumption could be a previously unknown causative agent for the complications associated with obesity.
Assuntos
Ácido Cítrico/efeitos adversos , Sacarose Alimentar/efeitos adversos , Aditivos Alimentares/efeitos adversos , Intolerância à Glucose/etiologia , Resistência à Insulina , Gordura Intra-Abdominal/imunologia , Paniculite/etiologia , Animais , Citocinas/sangue , Dieta Ocidental/efeitos adversos , Intolerância à Glucose/imunologia , Intolerância à Glucose/metabolismo , Intolerância à Glucose/patologia , Gordura Intra-Abdominal/metabolismo , Gordura Intra-Abdominal/patologia , Lipídeos/sangue , Fígado/imunologia , Fígado/metabolismo , Fígado/patologia , Masculino , Camundongos , Músculo Esquelético/imunologia , Músculo Esquelético/metabolismo , Músculo Esquelético/patologia , Tamanho do Órgão , Paniculite/imunologia , Paniculite/metabolismo , Paniculite/patologia , Distribuição AleatóriaRESUMO
OBJECTIVE: During pregnancy, women normally increase their food intake and body fat mass, and exhibit insulin resistance. However, an increasing number of women are developing metabolic imbalances during pregnancy, including excessive gestational weight gain and gestational diabetes mellitus. Despite the negative health impacts of pregnancy-induced metabolic imbalances, their molecular causes remain unclear. Therefore, the present study investigated the molecular mechanisms responsible for orchestrating the metabolic changes observed during pregnancy. METHODS: Initially, we investigated the hypothalamic expression of key genes that could influence the energy balance and glucose homeostasis during pregnancy. Based on these results, we generated a conditional knockout mouse that lacks the suppressor of cytokine signaling-3 (SOCS3) only in leptin receptor-expressing cells and studied these animals during pregnancy. RESULTS: Among several genes involved in leptin resistance, only SOCS3 was increased in the hypothalamus of pregnant mice. Remarkably, SOCS3 deletion from leptin receptor-expressing cells prevented pregnancy-induced hyperphagia, body fat accumulation as well as leptin and insulin resistance without affecting the ability of the females to carry their gestation to term. Additionally, we found that SOCS3 conditional deletion protected females against long-term postpartum fat retention and streptozotocin-induced gestational diabetes. CONCLUSIONS: Our study identified the increased hypothalamic expression of SOCS3 as a key mechanism responsible for triggering pregnancy-induced leptin resistance and metabolic adaptations. These findings not only help to explain a common phenomenon of the mammalian physiology, but it may also aid in the development of approaches to prevent and treat gestational metabolic imbalances.
RESUMO
Therapies that improve leptin sensitivity have potential as an alternative treatment approach against obesity and related comorbidities. We investigated the effects of Socs3 gene ablation in different mouse models to understand the role of SOCS3 in the regulation of leptin sensitivity, diet-induced obesity (DIO) and glucose homeostasis. Neuronal deletion of SOCS3 partially prevented DIO and improved glucose homeostasis. Inactivation of SOCS3 only in LepR-expressing cells protected against leptin resistance induced by HFD, but did not prevent DIO. However, inactivation of SOCS3 in LepR-expressing cells protected mice from diet-induced insulin resistance by increasing hypothalamic expression of Katp channel subunits and c-Fos expression in POMC neurons. In summary, the regulation of leptin signaling by SOCS3 orchestrates diet-induced changes on glycemic control. These findings help to understand the molecular mechanisms linking obesity and type 2 diabetes, and highlight the potential of SOCS3 inhibitors as a promising therapeutic approach for the treatment of diabetes.
RESUMO
Dehydroepiandrosterone (DHEA) and the dehydroepiandrosterone sulfate (DHEA-S) are steroids produced mainly by the adrenal cortex. There is evidence from both human and animal models suggesting beneficial effects of these steroids for obesity, diabetes mellitus, hypertension, and osteoporosis, conditions associated with the post-menopausal period. Accordingly, we hypothesized that DHEA supplementation in ovariectomized (OVX) female rats fed a high-fat diet would maintain glucose-induced insulin secretion (GSIS) and pancreatic islet function. OVX resulted in a 30% enlargement of the pancreatic islets area compared to the control rats, which was accompanied by a 50% reduction in the phosphorylation of AKT protein in the pancreatic islets. However, a short-term high-fat diet induced insulin resistance, accompanied by impaired GSIS in isolated pancreatic islets. These effects were reversed by DHEA treatment, with improved insulin sensitivity to levels similar to the control group, and with increased serine phosphorylation of the AKT protein. These data confirm the protective effect of DHEA on the endocrine pancreas in a situation of diet-induced overweight and low estrogen concentrations, a phenotype similar to that of the post-menopausal period.
RESUMO
The objective of this study was to investigate the impact of elevated tissue omega-3 (n-3) polyunsaturated fatty acids (PUFA) status on age-related glucose intolerance utilizing the fat-1 transgenic mouse model, which can endogenously synthesize n-3 PUFA from omega-6 (n-6) PUFA. Fat-1 and wild-type mice, maintained on the same dietary regime of a 10% corn oil diet, were tested at two different ages (2 months old and 8 months old) for various glucose homeostasis parameters and related gene expression. The older wild-type mice exhibited significantly increased levels of blood insulin, fasting blood glucose, liver triglycerides, and glucose intolerance, compared to the younger mice, indicating an age-related impairment of glucose homeostasis. In contrast, these age-related changes in glucose metabolism were largely prevented in the older fat-1 mice. Compared to the older wild-type mice, the older fat-1 mice also displayed a lower capacity for gluconeogenesis, as measured by pyruvate tolerance testing (PTT) and hepatic gene expression of phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6 phosphatase (G6Pase). Furthermore, the older fat-1 mice showed a significant decrease in body weight, epididymal fat mass, inflammatory activity (NFκ-B and p-IκB expression), and hepatic lipogenesis (acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) expression), as well as increased peroxisomal activity (70-kDa peroxisomal membrane protein (PMP70) and acyl-CoA oxidase1 (ACOX1) expression). Altogether, the older fat-1 mice exhibit improved glucose homeostasis in comparison to the older wild-type mice. These findings support the beneficial effects of elevated tissue n-3 fatty acid status in the prevention and treatment of age-related chronic metabolic diseases.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Ácidos Graxos Dessaturases/metabolismo , Ácidos Graxos Ômega-3/metabolismo , Intolerância à Glucose/metabolismo , Acetil-CoA Carboxilase/genética , Acetil-CoA Carboxilase/metabolismo , Fatores Etários , Animais , Glicemia/metabolismo , Proteínas de Caenorhabditis elegans/genética , Ácidos Graxos Dessaturases/genética , Ácido Graxo Sintases/genética , Ácido Graxo Sintases/metabolismo , Expressão Gênica , Gluconeogênese/genética , Glucose/metabolismo , Intolerância à Glucose/genética , Glucose-6-Fosfatase/genética , Glucose-6-Fosfatase/metabolismo , Homeostase/genética , Immunoblotting , Insulina/sangue , Lipogênese/genética , Fígado/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Fosfoenolpiruvato Carboxiquinase (ATP)/genética , Fosfoenolpiruvato Carboxiquinase (ATP)/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Introducción: La nutrición enteral (NE) es la entrega de nutrientes al tracto gastrointestinal mediante una sonda nasogástrica (SNG), nasoyeyunal (SNY) o de gastrostomía (GTT); siendo la ruta preferida para satisfacer las necesidades nutricionales cuando la vía oral está contraindicada o es insuficiente. Objetivo: Describir el perfil de pacientes pediátricos que requirieron NE domiciliaria y su efecto en el estado nutritivo. Sujetos y Método: Estudio analítico retrospectivo, en 37niños hospitalizados en el Servicio de Pediatría del Hospital Clínico Universidad Católica (UC) que fueron dados de alta con soporte nutricional enteral durante el período de Abril 2010 a Abril 2011. Resultados: La indicación principal para iniciar soporte nutricional fue trastorno de deglución (n=27), siendo la mayoría de los pacientes menores de 1 año al momento de recibir la indicación (n=27). El tipo de dispositivo más utilizado fue GTT (n=20). No hubo complicaciones asociadas al uso de SNG. Las complicaciones asociadas al uso de GTT fueron: granuloma periostomal (n=7), neumonía por aspiración (n=3) y retiro accidental (n=1). Del total de pacientes evaluados, un 62% presentaba desnutrición calórico-proteica al inicio de la NE versus 30% al último control (p<0,001). Conclusión: El uso de soporte nutricional enteral permite recuperar y/o mantener el estado nutricional de losniños con trastornos de la deglución y alteraciones en la curva del crecimiento, mejora la calidad de vida, y presenta una tasa baja de complicaciones mayores.
Enteral nutrition (EN) is the delivery ofnutrients to the gastrointestinal tract by nasogastric (SNG), nasojejunal (SNY) or gastrostomy (GTT), being the preferred route to fulfill nutritional needs when the oral route is contraindicated or inadequate. Objective: To describe the clinical profile of pediatric patients with home EN and to assess their nutritional status. Subjects and methods: A retrospective analytic study in 37 children from the Pediatric Service Hospital Clinico UC, discharged with enteral nutrition support from April 2010 to April 2011. Results: The main indication to use EN was swallowing disorder (n=27). 73% began EN before one year of life. GTT was the principal route to EN (n=20). There were no complications associated to NGT or OGT. The reported complications associated with GTT were periosteal granuloma (n=7), aspiration pneumonia (n=3) and accidental removal (n=1). 62% ofpatients had protein-calorie malnutrition (z-score W/H) at baseline vs. 30% at the last control (p<0,001). Conclusion: The use of enteral nutrition allows to restore and/ or to maintain nutritional status in children with swallowing disorder or undernutrition. This feeding procedure also improves the quality of life and promotes a proper development without major complications.