Citrate diminishes hypothalamic acetyl-CoA carboxylase phosphorylation and modulates satiety signals and hepatic mechanisms involved in glucose homeostasis in rats.

The hypothalamic AMP-activated protein kinase (AMPK)/acetyl-CoA carboxylase (ACC) pathway is known to play an important role in the control of food intake and energy expenditure. Here, we hypothesize that citrate, an intermediate metabolite, activates hypothalamic ACC and is involved in the control of energy mobilization. Initially, we showed that ICV citrate injection decreased food intake and diminished weight gain significantly when compared to control and pair-fed group results. In addition, we showed that intracerebroventricular (ICV) injection of citrate diminished (80% of control) the phosphorylation of ACC, an important AMPK substrate. Furthermore, citrate treatment inhibited (75% of control) hypothalamic AMPK phosphorylation during fasting. In addition to its central effect, ICV citrate injection led to low blood glucose levels during glucose tolerance test (GTT) and high glucose uptake during hyperglycemic-euglycemic clamp. Accordingly, liver glycogen content was higher in animals given citrate (ICV) than in the control group (23.3+/-2.5 vs. 2.7+/-0.5 microg mL(-1) mg(-1), respectively). Interestingly, liver AMPK phosphorylation was reduced (80%) by the citrate treatment. The pharmacological blockade of beta3-adrenergic receptor (SR 59230A) blocked the effect of ICV citrate and citrate plus insulin on liver AMPK phosphorylation. Consistently with these results, rats treated with citrate (ICV) presented improved insulin signal transduction in liver, skeletal muscle, and epididymal fat pad. Similar results were obtained by hypothalamic administration of ARA-A, a competitive inhibitor of AMPK. Our results suggest that the citrate produced by mitochondria may modulate ACC phosphorylation in the hypothalamus, controlling food intake and coordinating a multiorgan network that controls glucose homeostasis and energy uptake through the adrenergic system.

TNF-alpha acts in the hypothalamus inhibiting food intake and increasing the respiratory quotient--effects on leptin and insulin signaling pathways.

Acting in the hypothalamus, tumor necrosis factor-alpha (TNF-alpha) produces a potent anorexigenic effect. However, the molecular mechanisms involved in this phenomenon are poorly characterized. In this study, we investigate the capacity of TNF-alpha to activate signal transduction in the hypothalamus through elements of the pathways employed by the anorexigenic hormones insulin and leptin. High dose TNF-alpha promotes a reduction of 25% in 12h food intake, which is an inhibitory effect that is marginally inferior to that produced by insulin and leptin. In addition, high dose TNF-alpha increases body temperature and respiratory quotient, effects not reproduced by insulin or leptin. TNF-alpha, predominantly at the high dose, is also capable of activating canonical pro-inflammatory signal transduction in the hypothalamus, inducing JNK, p38, and NFkappaB, which results in the transcription of early responsive genes and expression of proteins of the SOCS family. Also, TNF-alpha activates signal transduction through JAK-2 and STAT-3, but does not activate signal transduction through early and intermediary elements of the insulin/leptin signaling pathways such as IRS-2, Akt, ERK and FOXO1. When co-injected with insulin or leptin, TNF-alpha, at both high and low doses, partially impairs signal transduction through IRS-2, Akt, ERK and FOXO1 but not through JAK-2 and STAT-3. This effect is accompanied by the partial inhibition of the anorexigenic effects of insulin and leptin, when the low, but not the high dose of TNF-alpha is employed. In conclusion, TNF-alpha, on a dose-dependent way, modulates insulin and leptin signaling and action in the hypothalamus.

Phosphoinositide-specific inositol polyphosphate 5-phosphatase IV inhibits inositide trisphosphate accumulation in hypothalamus and regulates food intake and body weight.

The enzyme phosphatidylinositol 3-kinase (PI3-kinase) exerts an important role in the transduction of the anorexigenic and thermogenic signals delivered by insulin and leptin to first-order neurons of the arcuate nucleus in the hypothalamus. The termination of the intracellular signals generated by the activation of PI3-kinase depends on the coordinated activity of specific inositol phosphatases. Here we show that phosphoinositide-specific inositol polyphosphate 5-phosphatase IV (5ptase IV) is highly expressed in neurons of the arcuate and lateral nuclei of the hypothalamus. Upon intracerebroventricular (ICV) treatment with insulin, 5ptase IV undergoes a time-dependent tyrosine phosphorylation, which follows the same patterns of canonical insulin signaling through the insulin receptor, insulin receptor substrate-2, and PI3-kinase. To evaluate the participation of 5ptase IV in insulin action in hypothalamus, we used a phosphorthioate-modified antisense oligonucleotide specific for this enzyme. The treatment of rats with this oligonucleotide for 4 d reduced the hypothalamic expression of 5ptase IV by approximately 80%. This was accompanied by an approximately 70% reduction of insulin-induced tyrosine phosphorylation of 5ptase IV and an increase in basal accumulation of phosphorylated inositols in the hypothalamus. Finally, inhibition of hypothalamic 5ptase IV expression by the antisense approach resulted in reduced daily food intake and body weight loss. Thus, 5ptase IV is a powerful regulator of signaling through PI3-kinase in hypothalamus and may become an interesting target for therapeutics of obesity and related disorders.

Aminoguanidine prevented impairment of blood antioxidant system in insulin-dependent diabetic rats.

Non-enzymatic glycation is implicated in the development of various diseases such as Alzheimer's and diabetes mellitus. However, it is also observed during the physiologic process of aging. There is considerable interest in the contribution of oxidative stress to diabetes mellitus. An increase in the generation of reactive oxygen species can occur by non-enzymatic glycation and glucose autoxidation. Both of these processes lead to the formation of AGEs (Advanced glycation end-products) that contribute to the irreversible modification of enzymes, proteins, lipids and DNA. In this study, the effect of chronic hyperglycemia on the antioxidant system of diabetic rats was evaluated. The working hypothesis is that the loss of glucose homeostasis reduces the capacity to respond to oxidative damage. The enzymatic activities of CAT (catalase), GPx (gluthatione peroxidase), GR (gluthatione reductase) and GSH (reduced gluthatione) were increased in the blood of healthy rats subjected to endurance training, whereas, in diabetic rats the activities of CAT, GPx and GR were unaltered by similar training. SOD showed low activity in endurance-trained rats. The administration of aminoguanidine (an inhibitor of glycation reactions) in the drinking water increased the activities of CAT, GPx and GR, suggesting that glycation may be responsible for the partial inactivation of these enzymes. These results indicate that the association of hyperglycemia with strenuous physical exercise may induce cellular damage by impairing the antioxidant defense system.

Acompanhamento do perfil glicêmico de indivíduos obesos submetidos à cirurgia bariátrica / Seguimiento del perfil glucémico de los sujetos obesos sometidos a cirugía bariátrica / Follow-up of glycemic profile of obese individuals submitted to bariatric surgery

Introdução: A obesidade é uma enfermidade crônica que acomete bilhões de indivíduos e está associada ao desequilíbrio nutricionalentre o ganho calórico e o gasto energético, decorrente de distúrbios genéticos ou endocrinometabólicos, do ambiente, do estilo de vidae de fatores emocionais. Dentre as alterações metabólicas consequentes da obesidade destacam-se a resistência à insulina, hipertensão,dislipidemia, síndrome metabólica e diabetes mellitus tipo 2. A cirurgia bariátrica, como estratégia de restrição calórica, é uma alternativapara diminuição do peso corporal e redução das comorbidades decorrentes da obesidade. Objetivo: Avaliar o efeito da cirurgia bariátrica“Fobi-Capella” sobre a glicemia em jejum e no período pós-operatório de trinta dias a 12 meses e a correlação da normalização daglicemia com a perda de adiposidade. Material e Método: Estudo realizado pela análise de prontuários clínicos não nominais, de trintaindivíduos obesos Graus II e III, submetidos à cirurgia bariátrica de “Fobi-Capella” e que tiveram registrados os índices glicêmicos,em jejum de oito horas, em momentos pré-operatório, um mês, seis meses e um ano de pós-operatório. Resultados: A glicemia dosindivíduos atingiu valores considerados normais pela Sociedade Brasileira de Diabetes, nos primeiros trinta dias após a cirurgia bariátricae foi mantida até um ano. A avaliação nos períodos pré e pós-cirúrgicos de um mês demonstrou a redução gradativa de 35,78% dopeso; de 36,38% do IMC e 35,01% da glicemia. Conclusão: Os resultados indicaram uma normalização duradoura dos níveis glicêmicos,mantida pelo período de um ano após a cirurgia bariátrica e acompanhada da perda de adiposidade corporal, o que comprova a eficáciada cirurgia bariátrica para normalizar a absorção de glicose e, provavelmente, minimizar o quadro de diabetes.

Introduction: Obesity is a chronic disease affecting billions of people and related to the nutritional imbalance between energy intakeand energy expenditure due to genetic, endocrine-metabolic, environmental, behavioral, and emotional factors. Insulin resistance,hypertension, dyslipidemia, metabolic syndrome and type 2 diabetes are included among the metabolic disorders caused by obesity.Bariatric surgery, as a strategy of calories restriction, is a way to reduce body weight and comorbidities due to obesity. Objective: Evaluatethe effect of Fobi-Capella bariatric surgery on fasting glycaemia during the period from 30 days to 12 months after surgery and thecorrelation between glycemic normalization and adiposity loss. Materials and Method: The study was performed through the analysis ofplasma glucose records of thirty obese individuals (class II and III) submitted to “Fobi-Capella” bariatric surgery, who had their 8 hoursfasting glycemic indexes recorded before surgery, as well as one, six and twelve months after. Results: A return to euglycemia, accordingwith Diabetes Brazilian Society criteria, occurred within thirty days after surgery and was maintained for at least one year. Data analysisperformed before and 30 days after surgery showed a gradual decrease of 35.78% in body weight, 36.38% in BMI (Body Mass Index),and 35.01 % in plasma glucose level. Conclusion: These results suggest that bariatric surgery effectively normalizes glycemic levels, forat least one year, associated with a decrease of body adiposity, showing that bariatric surgery is effective for normalization of glucoseuptake and, possibly, for minimizing diabetes picture.

Introducción: La obesidades es una enfermedad crónica que afecta a miles de millones de personas y está asociado con el desequilibrionutricional entre la ganancia, la ingesta calórica y el gasto energético, debido a trastornos genéticos o endocrinometabólicos, medioambiente, estilo de vida y factores emocionales. Entre los cambios metabólicos derivados de la obesidade se incluyen la resistenciaa la insulina, hipertensión, dislipidemia, síndrome metabólico y diabetes mellitus tipo 2. La cirugía bariátrica como una estrategiade restricción calórica es una alternativa para disminuir el peso corporal y la reducción de comorbilidades derivadas de la obesidad.Objetivo: Evaluar, a través de la recopilación de datos en los registros clínicos, el efecto de la cirugía bariátrica “Fobi-Capella” sobrelos niveles de glucosa en plasma en ayunas y en el post operatorio de 30 días a 12 meses y verificar la correlación de la normalizaciónde los niveles de glucosa en la sangre con la pérdida de grasa corporal. Material y Método: Estudio realizado mediante el análisis delos registros médicos no nominales, 30 individuos obesos de grado II y III, sometidos a cirugía bariátrica “Fobi-Capella” y que habíaregistrado los índices (índice glucémico, el ayuno durante 8 horas, a veces pre-operatorio, treinta días, seis meses y doce meses despuésde la cirugía. Resultados: La glucosa en la sangre de indivíduos alcanzaron valores considerados normales por la Sociedad Brasileña deDiabetes, dentro de los primeros 30 días después de la cirugía bariátrica y...

Intracerebroventricular injection of citrate inhibits hypothalamic AMPK and modulates feeding behavior and peripheral insulin signaling.

We hypothesized that citrate might modulate the AMP-activated protein kinase/acetyl-CoA carboxylase (AMPK)/(ACC) pathway and participate in neuronal feeding control and glucose homeostasis. To address this issue, we injected citrate into the lateral ventricle of rats. Intracerebroventricular (ICV) injection of citrate diminished the phosphorylation of hypothalamic AMPK/ACC, increased the expression of anorexigenic neuropeptide (pro-opiomelanocortin and corticotropin-releasing hormone), elevated the level of malonyl-CoA in the hypothalamus, and reduced food intake. No change was observed in the concentration of blood insulin after the injection of citrate. With a euglycemic-hyperinsulinemic clamp, the glucose infusion rate was higher in the citrate group than in the control group (28.6+/-0.8 vs 19.3+/-0.2 mU/kg body weight/min respectively), and so was glucose uptake in skeletal muscle and the epididymal fat pad. Concordantly, insulin receptor (IR), IR substrate type 1 (IRS1), IRS2, and protein kinase B (AKT) phosphorylation in adipose tissue and skeletal muscle was improved by citrate ICV treatment. Moreover, the treatment with citrate for 7 days promoted body weight loss and decreased the adipose tissue. Our results suggest that citrate and glucose may serve as signals of energy and nutrient availability to hypothalamic cells.

Activation of AMPK in rat hypothalamus participates in cold-induced resistance to nutrient-dependent anorexigenic signals.

The exposure of homeothermic animals to a cold environment leads to a powerful activation of orexigenic signalling which is accompanied by molecular and functional resistance to insulin-induced inhibition of feeding. Recent evidence suggests that AMPK participates in nutrient-dependent control of satiety and adiposity. The objective of the present study was to evaluate the effect of cold exposure upon the molecular activation of AMPK signalling in the hypothalamus of rats. Immunoblotting demonstrated that cold exposure per se is sufficient for inducing, on a time-dependent basis, the molecular activation of the serine/threonine kinase AMP-activated protein kinase (AMPK) and inactivation of the acetyl-CoA carboxylase (ACC). These molecular phenomena were accompanied by resistance to nutrient-induced inactivation of AMPK and activation of ACC. Moreover, cold-exposure led to a partial inhibition of a feeding-induced anorexigenic response, which was paralleled by resistance to insulin-induced suppression of feeding. Finally, cold exposure significantly impaired insulin-induced inhibition of AMPK through a mechanism dependent on the molecular cross-talk between phosphatidylinositol-3(PI3)-kinase/Akt and AMPK. In conclusion, increased feeding during cold exposure results, at least in part, from resistance to insulin- and nutrient-dependent anorexigenic signalling in the hypothalamus.