Cocaine- and amphetamine-regulated transcript in the rat vagus nerve: A putative mediator of cholecystokinin-induced satiety

Cocaine- and amphetamine-regulated transcript (CART) is widely expressed in the central nervous system. Recent studies have pointed to a role for CART-derived peptides in inhibiting feeding behavior. Although these actions have generally been attributed to hypothalamic CART, it remains to be determined whether additional CART pathways exist that link signals from the gastrointestinal tract to the central control of food intake. In the present study, we have investigated the presence of CART in the rat vagus nerve and nodose ganglion. In the viscerosensory nodose ganglion, half of the neuron profiles expressed CART and its predicted peptide, as determined by in situ hybridization and immunohistochemistry. CART expression was markedly attenuated after vagotomy, but no modulation was observed after food restriction or high-fat regimes. A large proportion of CART-labeled neuron profiles also expressed cholecystokinin A receptor mRNA. CART-peptide-like immunoreactivity was transported in the vagus nerve and found in a dense fiber plexus in the nucleus tractus solitarii. Studies on CART in the spinal somatosensory system revealed strong immunostaining of the dorsal horn but only a small number of stained cell bodies in dorsal root ganglia. The present results suggest that CART-derived peptides are present in vagal afferent neurons sensitive to cholecystokinin, suggesting that the role of these peptides in feeding may be explained partly by mediating postprandial satiety effects of cholecystokinin.

Disappearance of body fat in normal rats induced by adenovirus-mediated leptin gene therapy

Sustained hyperleptinemia of 8 ng/ml was induced for 28 days in normal Wistar rats by infusing a recombinant adenovirus containing the rat leptin cDNA (AdCMV-leptin). Hyperleptinemic rats exhibited a 30–50% reduction in food intake and gained only 22 g over the experimental period versus 115–132 g in control animals that received saline infusions or a recombinant virus containing the β-galactosidase gene (AdCMV-βGal). Body fat was absent in hyperleptinemic rats, whereas control rats pair-fed to the hyperleptinemic rats retained ≈50% body fat. Further, plasma triglycerides and insulin levels were significantly lower in hyperleptinemic versus pair-fed controls, while fatty acid and glucose levels were similar in the two groups, suggestive of enhanced insulin sensitivity in the hyperleptinemic animals. Thus, despite equivalent reductions in food intake and weight gain in hyperleptinemic and pair-fed animals, identifiable fat tissue was completely ablated only in the former group, raising the possibility of a specific lipoatrophic activity for leptin.

Correction of obesity and diabetes in genetically obese mice by leptin gene therapy

The ob/ob mouse is genetically deficient in leptin and exhibits both an obese and a mild non-insulin-dependent diabetic phenotype. To test the hypothesis that correction of the obese phenotype by leptin gene therapy will lead to the spontaneous correction of the diabetic phenotype, the ob/ob mouse was treated with a recombinant adenovirus expressing the mouse leptin cDNA. Treatment resulted in dramatic reductions in both food intake and body weight, as well as the normalization of serum insulin levels and glucose tolerance. The subsequent diminishment in serum leptin levels resulted in the rapid resumption of food intake and a gradual gain of body weight, which correlated with the gradual return of hyperinsulinemia and insulin resistance. These results not only demonstrated that the obese and diabetic phenotypes in the adult ob/ob mice are corrected by leptin gene treatment but also provide confirming evidence that body weight control may be critical in the long-term management of non-insulin-dependent diabetes mellitus in obese patients.

Corticotropin-releasing factor-binding protein ligand inhibitor blunts excessive weight gain in genetically obese Zucker rats and rats during nicotine withdrawal

Elevation of the neuropeptide corticotropin-releasing factor (CRF) in the brain is associated with a reduction of food intake and body weight gain in normal and obese animals. A protein that binds CRF and the related peptide, urocortin, with high affinity, CRF-binding protein (CRF-BP), may play a role in energy homeostasis by inactivating members of this peptide family in ingestive and metabolic regulatory brain regions. Intracerebroventricular administration in rats of the high-affinity CRF-BP ligand inhibitor, rat/human CRF (6-33), which dissociates CRF or urocortin from CRF-BP and increases endogenous brain levels of “free” CRF or urocortin significantly blunted exaggerated weight gain in Zucker obese subjects and in animals withdrawn from chronic nicotine. Chronic administration of CRF suppressed weight gain nonselectively by 60% in both Zucker obese and lean control rats, whereas CRF-BP ligand inhibitor treatment significantly reduced weight gain in obese subjects, without altering weight gain in lean control subjects. Nicotine abstinent subjects, but not nicotine-naive controls, experienced a 35% appetite suppression and a 25% weight gain reduction following acute and chronic administration, respectively, of CRF-BP ligand inhibitor. In marked contrast to the effects of a CRF-receptor agonist, the CRF-BP ligand inhibitor did not stimulate adrenocorticotropic hormone secretion or elevate heart rate and blood pressure. These results provide support for the hypothesis that the CRF-BP may function within the brain to limit selected actions of CRF and/or urocortin. Furthermore, CRF-BP may represent a novel and functionally selective target for the symptomatic treatment of excessive weight gain associated with obesity of multiple etiology.

Regulation of fatty acid homeostasis in cells: Novel role of leptin

It is proposed that an important function of leptin is to confine the storage of triglycerides (TG) to the adipocytes, while limiting TG storage in nonadipocytes, thus protecting them from lipotoxicity. The fact that TG content in nonadipocytes normally remains within a narrow range, while that of adipocytes varies enormously with food intake, is consistent with a system of TG homeostasis in normal nonadipocytes. The facts that when leptin receptors are dysfunctional, TG content in nonadipocytes such as islets can increase 100-fold, and that constitutively expressed ectopic hyperleptinemia depletes TG, suggest that leptin controls the homeostatic system for intracellular TG. The fact that the function and viability of nonadipocytes is compromised when their TG content rises above or falls below the normal range suggests that normal homeostasis of their intracellular TG is critical for optimal function and to prevent lipoapoptosis. Thus far, lipotoxic diabetes of fa/fa Zucker diabetic fatty rats is the only proven lipodegenerative disease, but the possibility of lipotoxic disease of skeletal and/or cardiac muscle may require investigation, as does the possible influence of the intracellular TG content on autoimmune and neoplastic processes.

Leptin as a modulator of sweet taste sensitivities in mice

Leptin acts as a potent inhibitory factor against obesity by regulating energy expenditure, food intake, and adiposity. The obese diabetic db/db mouse, which has defects in leptin receptor, displays enhanced neural responses and elevated behavioral preference to sweet stimuli. Here, we show the effects of leptin on the peripheral taste system. An administration of leptin into lean mice suppressed responses of peripheral taste nerves (chorda tympani and glossopharyngeal) to sweet substances (sucrose and saccharin) without affecting responses to sour, salty, and bitter substances. Whole-cell patch-clamp recordings of activities of taste receptor cells isolated from circumvallate papillae (innervated by the glossopharyngeal nerve) demonstrated that leptin activated outward K+ currents, which resulted in hyperpolarization of taste cells. The db/db mouse with impaired leptin receptors showed no such leptin suppression. Taste tissue (circumvallate papilla) of lean mice expressed leptin-receptor mRNA and some of the taste cells exhibited immunoreactivities to antibodies of the leptin receptor. Taken together, these observations suggest that the taste organ is a peripheral target for leptin, and that leptin may be a sweet-sensing modulator (suppressor) that may take part in regulation of food intake. Defects in this leptin suppression system in db/db mice may lead to their enhanced peripheral neural responses and enhanced behavioral preferences for sweet substances.

Enhancing leptin response by preventing SH2-containing phosphatase 2 interaction with Ob receptor

Leptin is an adipocyte-derived cytokine that regulates food intake and body weight via interaction with its Ob receptor (ObR). Serum leptin levels are chronically elevated in obese humans, suggesting that obesity may be associated with leptin resistance and the inability to generate an adequate ObR response. Evidence suggests that transcriptional activation of target genes by STAT3 (signal transducer and activator of transcription) in the hypothalamus is a critical pathway that mediates leptin’s action. Herein we report that activation of ObR induces the tyrosine phosphorylation of the tyrosine phosphatase SH2-containing phosphatase 2 (SHP-2) and demonstrate that Tyr986 within the ObR cytoplasmic domain is essential to mediate phosphorylation of SHP-2 and binding of SHP-2 to ObR. Surprisingly, mutation of Tyr986 to Phe, which abrogates SHP-2 phosphorylation and binding to the receptor, dramatically increases gene induction mediated by STAT3. Our findings indicate that SHP-2 is a negative regulator of STAT3-mediated gene induction after activation of ObR and raise the possibility that blocking the interaction of SHP-2 with ObR could overcome leptin resistance by boosting leptin’s weight-reducing effects in obese individuals.

Obesity and mild hyperinsulinemia found in neuropeptide Y-Y1 receptor-deficient mice

To elucidate the role of neuropeptide Y (NPY)-Y1 receptor (Y1-R) in food intake, energy expenditure, and other possible functions, we have generated Y1-R-deficient mice (Y1-R−/−) by gene targeting. Contrary to our hypothesis that the lack of NPY signaling via Y1-R would result in impaired feeding and weight loss, Y1-R−/− mice showed a moderate obesity and mild hyperinsulinemia without hyperphagia. Although there was some variation between males and females, typical characteristics of Y1-R−/− mice include: greater body weight (females more than males), an increase in the weight of white adipose tissue (WAT) (approximately 4-fold in females), an elevated basal level of plasma insulin (approximately 2-fold), impaired insulin secretion in response to glucose administration, and a significant changes in mitochondrial uncoupling protein (UCP) gene expression (up-regulation of UCP1 in brown adipose tissue and down-regulation of UCP2 in WAT). These results suggest either that the Y1-R in the hypothalamus is not a key molecule in the leptin/NPY pathway, which controls feeding behavior, or that its deficiency is compensated by other receptors, such as NPY-Y5 receptor. We believe that the mild obesity found in Y1-R−/− mice (especially females) was caused by the impaired control of insulin secretion and/or low energy expenditure, including the lowered expression of UCP2 in WAT. This model will be useful for studying the mechanism of mild obesity and abnormal insulin metabolism in noninsulin-dependent diabetes mellitus.

Integrated control of appetite and fat metabolism by the leptin-proopiomelanocortin pathway

Leptin deficiency results in a complex obesity phenotype comprising both hyperphagia and lowered metabolism. The hyperphagia results, at least in part, from the absence of induction by leptin of melanocyte stimulating hormone (MSH) secretion in the hypothalamus; the MSH normally then binds to melanocortin-4 receptor expressing neurons and inhibits food intake. The basis for the reduced metabolic rate has been unknown. Here we show that leptin administered to leptin-deficient (ob/ob) mice results in a large increase in peripheral MSH levels; further, peripheral administration of an MSH analogue results in a reversal of their abnormally low metabolic rate, in an acceleration of weight loss during a fast, in partial restoration of thermoregulation in a cold challenge, and in inducing serum free fatty acid levels. These results support an important peripheral role for MSH in the integration of metabolism with appetite in response to perceived fat stores indicated by leptin levels.

Ciliary neurotrophic factor activates leptin-like pathways and reduces body fat, without cachexia or rebound weight gain, even in leptin-resistant obesity

Ciliary Neurotrophic Factor (CNTF) was first characterized as a trophic factor for motor neurons in the ciliary ganglion and spinal cord, leading to its evaluation in humans suffering from motor neuron disease. In these trials, CNTF caused unexpected and substantial weight loss, raising concerns that it might produce cachectic-like effects. Countering this possibility was the suggestion that CNTF was working via a leptin-like mechanism to cause weight loss, based on the findings that CNTF acts via receptors that are not only related to leptin receptors, but also similarly distributed within hypothalamic nuclei involved in feeding. However, although CNTF mimics the ability of leptin to cause fat loss in mice that are obese because of genetic deficiency of leptin (ob/ob mice), CNTF is also effective in diet-induced obesity models that are more representative of human obesity, and which are resistant to leptin. This discordance again raised the possibility that CNTF might be acting via nonleptin pathways, perhaps more analogous to those activated by cachectic cytokines. Arguing strongly against this possibility, we now show that CNTF can activate hypothalamic leptin-like pathways in diet-induced obesity models unresponsive to leptin, that CNTF improves prediabetic parameters in these models, and that CNTF acts very differently than the prototypical cachectic cytokine, IL-1. Further analyses of hypothalamic signaling reveals that CNTF can suppress food intake without triggering hunger signals or associated stress responses that are otherwise associated with food deprivation; thus, unlike forced dieting, cessation of CNTF treatment does not result in binge overeating and immediate rebound weight gain.

Glucocorticoids have state-dependent stimulant effects on the mesencephalic dopaminergic transmission.

An increase in the activity of mesencephalic dopaminergic neurons has been implicated in the appearance of pathological behaviors such as psychosis and drug abuse. Several observations suggest that glucocorticoids might contribute to such an increase in dopaminergic activity. The present experiments therefore analyzed the effects of corticosterone, the major glucocorticoid in the rat, both on dopamine release in the nucleus accumbens of freely moving animals by means of microdialysis, and on locomotor activity, a behavior dependent on accumbens dopamine. Given that glucocorticoids have certain state-dependent neuronal effects, their action on dopamine was studied in situations differing in dopaminergic tonus, including during the light and dark phases of the circadian cycle, during eating, and in groups of animals differing in their locomotor reactivity to novelty. Dopaminergic activity is increased in the dark period, further increased during food-intake, and is higher in rats defined as high responders to novelty than in low responders. Corticosterone, peripherally administered in a dose that approximates stress-induced plasma concentrations, increased extracellular concentrations of dopamine, and this increase was augmented in the dark phase, during eating, and in high responder rats. Corticosterone had little or no effects in the light phase and in low responder rats. Corticosterone also stimulated locomotor activity, an effect that paralleled the release of dopamine and was abolished by neurochemical (6-hydroxydopamine) depletion of accumbens dopamine. In conclusion, glucocorticoids have state-dependent stimulant effects on mesencephalic dopaminergic transmission, and an interaction between these two factors might be involved in the appearance of behavioral disturbances.

Alimentação de adolescentes de três regiões administrativas do município de Vitória - ES: qualidade e fatores associados

Introdução: A adolescência é uma fase importante para formação e consolidação de hábitos alimentares adequados à promoção da saúde. Entretanto, dados estatísticos recentes indicam enorme comprometimento no padrão alimentar de indivíduos nesse período da vida. Objetivo: Avaliar a qualidade da dieta e identificar seus fatores associados em adolescentes de três regiões administrativas do município de Vitória. Métodos: Estudo transversal de base populacional com 396 adolescentes de ambos os sexos, de 8 a 17 anos, de escolas públicas e privadas de três regiões administrativas de Vitória-ES. Foram coletados dados antropométricos, socioeconômicos, demográficos e alimentares. Para a entrevista alimentar utilizou-se o método de Recordatório de 24h. A qualidade da dieta foi avaliada pelo Índice de Qualidade da Dieta adaptado (IQDa). Análises de regressão logística foram utilizadas para verificar a associação das variáveis independentes sobre a qualidade da dieta dos adolescentes. Resultados: A média do IQDa foi de 35,6 pontos. Os componentes verduras e legumes, leite e derivados e frutas apresentaram os mais baixos valores médios de pontos; e carnes e ovos apresentaram a pontuação média mais alta do IQDa. Na análise de regressão observou-se que quanto maior a idade, menor a pontuação do IQDa e que os adolescentes do sexo masculino apresentaram IQDa maior que as do sexo feminino. Conclusão: A qualidade da dieta está associada ao sexo e a idade e necessita de melhorias. Conhecendo esses fatores associados é possível analisar e identificar as práticas alimentares não saudáveis e abordá-las em programas de educação nutricional, proporcionando melhores condições de saúde a essa população.

Dieta e fatores de riscos metabólicos para doença cardiovascular em adultos e idosos residentes no município de São Paulo: uma análise por modelos de equações estruturais

Introdução: As doenças cardiovasculares são a principal causa de morte no Brasil e no mundo e apresentam importante contribuição para a carga global de doenças. A dieta tem sido considerada um dos determinantes primários do estado de saúde dos indivíduos, atuando na modulação dos fatores de risco metabólicos para doença cardiovascular. Objetivos: Desenvolver um modelo conceitual para a relação entre fatores de risco metabólicos e investigar sua associação com padrões de dieta de adultos e idosos residentes no município de São Paulo. Métodos: Estudo transversal de base populacional com amostra probabilística de adultos e idosos, residentes em área urbana do município de São Paulo, que participaram do Inquérito de Saúde do Município de São Paulo, realizado em duas fases entre os anos de 2008 e 2011 (estudo ISA Capital 2008). Na primeira fase do estudo, 1.102 adultos e idosos, de ambos os sexos, foram entrevistados no domicílio, por meio da aplicação de questionário estruturado e do recordatório alimentar de 24 horas. Na segunda fase, 642 indivíduos adultos e idosos foram reavaliados quanto ao consumo alimentar por meio da aplicação, por telefone, do segundo recordatório alimentar, e, destes, 592 participaram da coleta domiciliar de amostras de sangue venoso, da medição antropométrica e da aferição da pressão arterial por técnico de enfermagem. Os alimentos relatados em ambos os recordatórios foram agrupados segundo a similaridade do valor nutricional e hábitos alimentares da população, e corrigidos pela variância intrapessoal da ingestão por procedimentos estatísticos da plataforma online Multiple Source Method. Os grupos de alimentos foram analisados por meio de análise fatorial exploratória e confirmatória (manuscrito 1) e por modelos de equações estruturais exploratórios (manuscrito 3), a fim de obter os padrões de dieta. O modelo conceitual da relação entre os fatores de risco metabólicos (leptina sérica, proteína C-reativa de alta sensibilidade sérica, pressão arterial sistólica e diastólica, razão colesterol total/lipoproteína de alta densidade, razão triacilglicerol/lipoproteína de alta densidade, glicemia de jejum plasmática, circunferência da cintura e peso corporal) foi obtido por modelos de equações estruturais estratificados por sexo (manuscrito 2). Por fim, a associação dos padrões de dieta com o modelo conceitual proposto (manuscrito 3) foi investigada por modelos de equações estruturais exploratórios. Índices de qualidade de ajuste foram estimados para avaliar a adequação de todos os modelos. As análises foram realizadas no programa Mplus versão 6.12. Resultados: No manuscrito 1, a análise fatorial exploratória revelou a existência de dois padrões de dieta, os quais apresentaram boa qualidade de ajuste na análise fatorial confirmatória quando aplicados os pontos de corte de cargas fatoriais |0,25| na rotação oblíqua Promax. No manuscrito 2, a relação entre os fatores de risco metabólicos foi diferente entre os sexos. Nas mulheres, a leptina sérica apresentou efeitos indiretos e positivos, mediados pelo peso corporal e pela circunferência da cintura, em todos os fatores de risco avaliados. Já nos homens, a leptina sérica apresentou efeitos diretos e positivos sobre a proteína C-reativa de alta sensibilidade e efeitos indiretos e positivos (mediados pelo peso corporal e pela circunferência da cintura) sobre a razão triacilglicerol/lipoproteína de alta densidade, colesterol total/lipoproteína de alta densidade e glicemia de jejum plasmática. No manuscrito 3, foram obtidos três padrões de dieta, dos quais o Tradicional apresentou relação direta e negativa com a leptina sérica e relação indireta e negativa com o peso corporal e a circunferência da cintura, bem como com os demais fatores de risco metabólicos. Já o padrão Prudente apresentou relação direta e negativa com a pressão arterial sistólica, enquanto o padrão Moderno não se associou aos fatores de risco metabólicos investigados. Conclusão: Diferenças nos padrões de dieta de acordo com o tipo de rotação fatorial empregada foram observadas. A relação entre os fatores de risco metabólicos para doença cardiovascular foi distinta entre homens e mulheres, sendo a leptina um dos possíveis hormônios envolvidos. Os padrões de dieta Tradicional e Prudente associaram-se inversamente com os fatores de risco metabólicos, desempenhando uma importante estratégia de prevenção e controle às doenças cardiovasculares no país.

Efeitos do treinamento de força no músculo esquelético em ratos com caquexia induzida pelo câncer

A ausência de terapias eficazes para a caquexia permanece como um problema central para o tratamento do câncer no mundo. Em contrapartida, o treinamento de força (i.e. também conhecido como treinamento resistido) tem sido amplamente utilizado como uma estratégia não farmacológica anticatabólica, prevenindo a perda da massa e da função da musculatura esquelética. Entretanto, o papel terapêutico do treinamento de força na caquexia do câncer permanece apenas especulativo. Portanto, nesse estudo avaliamos se o treinamento de força poderia atenuar a perda da massa e da função da musculatura esquelética em um severo modelo de caquexia do câncer em ratos. Para isso, ratos machos da linhagem Wistar foram randomizados em quatro grupos experimentais: 1) ratos sedentários injetados com solução salina na medula óssea (Controle); 2) ratos injetados com solução salina na medula óssea e submetidos ao treinamento de força (Controle + T); 3) ratos sedentários injetados com células do tumor Walker 256 na medula óssea (Tumor); e 4) ratos injetados com células do tumor Walker 256 na medula óssea e submetidos ao treinamento de força (Tumor + T). Foram avaliados a massa e a área de secção transversa da musculatura esquelética, marcadores de disfunção metabólica e do turnover proteico, a função da musculatura esquelética in vivo e ex vivo, o consumo alimentar, o crescimento tumoral e a sobrevida dos grupos experimentais com tumor. O grupo Tumor apresentou atrofia muscular após quinze dias da injeção das células tumorais como pode ser observado pela redução na massa dos músculos Plantaris (- 20,5%) e EDL (-20%). A atrofia no músculo EDL foi confirmada por análises histológicas, demonstrando uma redução de 43,8% na área de secção transversa. Embora o treinamento de força tenha aumentado o conteúdo proteico da lactato desidrogenase e revertido totalmente o conteúdo da forma fosforilada de 4EBP-1 (i.e. repressor da transcrição de mRNA), ele não atuou na morfologia da musculatura esquelética nos animais com tumor. Além disso, o treinamento de força não atenuou a perda de função da musculatura esquelética, a anorexia, o crescimento tumoral ou a taxa de mortalidade. Contudo, a força muscular, avaliada pelo teste de 1RM, apresentou uma correlação negativa com a sobrevida dos animais (p = 0,02), sugerindo que a perda de força prediz a mortalidade nesse modelo experimental de caquexia do câncer. Em suma, a injeção de células do tumor Walker 256 na medula óssea induz caquexia do câncer em ratos. O treinamento de força não foi eficaz em atenuar a perda de massa e função da musculatura esquelética nesse modelo. Entretanto, a força muscular prediz a sobrevida dos animais, sugerindo que novos estudos são necessários para elucidar o possível efeito terapêutico do treinamento de força para atenuar a caquexia do câncer e a progressão tumoral

¿Siguen patrones de dieta mediterránea los universitarios españoles?

Objetivo: Determinar el patrón de consumo de alimentos del alumnado de la Universidad de Alicante (UA) mediante el grado de adecuación a la dieta mediterránea. Método: Estudio transversal descriptivo para estimar la ingesta individual a través de un cuestionario de frecuencia de consumo de alimentos (CFCA) en una muestra representativa de 380 universitarios. Variables a estudio: edad, sexo, área geográfica de procedencia, peso y talla autoreferidos. Así como los alimentos y frecuencias de consumo que componen el CFCA. Se determinó el porcentaje de adecuación teniendo en cuenta, consumo real sobre consumo recomendado por la guía dieta mediterránea tradicional: (100 x raciones consumidas/raciones recomendadas). Se establecieron 5 rangos de porcentaje adecuación: consumo óptimo (80%-119%), consumo aceptable (60%-79%), consumo deficiente (40%-59%), consumo muy deficiente (< 39%), consumo excesivo (> 120%). Se realizó contraste de diferencia de proporciones y la prueba t-Student con EPIDAT 3.1, y SPSS 15.0. Resultados: Prevalencia de sobrepeso-obesidad, es mayor en hombres (34,6%) que en mujeres (9,8%), p < 0,001. Mientras que las mujeres presentan mayor prevalencia de bajo peso (7,0%) que hombres (0,7%), p < 0,05. El consumo de cereales y derivados es muy deficiente (mujeres = 90,6; hombres = 94,9), y el consumo de carnes rojas (mujeres = 90,6; hombres = 92,7) y embutidos (mujeres = 95,9%, hombres = 96,3%) es excesivo. Ningún alumno cubre un “consumo óptimo” o un “consumo aceptable” de todos los grupos de alimentos (n = 12). Discusión: El nivel educativo y el acceso a la información no protegen a la población universitaria de factores socioambientales que influencian sus hábitos alimentarios. Deben reforzarse estrategias de salud pública dirigidas a este grupo de población.