RESUMO
Protein-tyrosine phosphatase 1B (PTP1B, EC 3.1.3.48) is an important regulator of insulin signalling. Herein, we employed experimental and computational biology techniques to investigate the inhibitory properties of phenolics, identified from four in vitro gastrointestinal digested (IVGD) soft fruits, on PTP1B. Analysis by LC-MS/MS identified specific phenolics that inhibited PTP1B in vitro. Enzyme kinetics identified the mode of inhibition, while dynamics, stability and binding mechanisms of PTP1B-ligand complex were investigated through molecular modelling, docking, molecular dynamics (MD) simulations, and MM/PBSA binding free energy estimation. IVGD extracts and specific phenolics identified from the four soft fruits inhibited PTP1B (P < 0.0001) activity. Among the phenolics tested, the greatest inhibition was shown by malvidin-3-glucoside (P < 0.0001) and gallic acid (P < 0.0001). Malvidin-3-glucoside (Ki = 3.8 µg/mL) was a competitive inhibitor and gallic acid (Ki = 33.3 µg/mL) a non-competitive inhibitor of PTP1B. Malvidin-3-glucoside exhibited better binding energy than gallic acid and the synthetic inhibitor Dephostatin (-7.38 > -6.37 > -5.62 kcal/mol) respectively. Principal component analysis demonstrated malvidin-3-glucoside PTP1B-complex occupies more conformational space where critical WPD-loop displayed a higher degree of motion. MM/PBSA binding free energy for malvidin-3-glucoside to PTP1B was found to be higher than other complexes mediated by Van der Waals energy rather than electrostatic interaction for the other two inhibitors (-80.32 ± 1.25 > -40.64 ± 1.43 > -21.63 ± 1.73 kcal/mol) respectively. Altogether, we have established novel insights into the specific binding of dietary phenolics and have identified malvidin-3-glucoside as an PTP1B inhibitor, which may be further industrially developed for the treatment of type-2 diabetes.
Assuntos
Antocianinas/química , Glucosídeos/química , Polifenóis/química , Proteína Tirosina Fosfatase não Receptora Tipo 1/antagonistas & inibidores , Ribes/química , Vaccinium myrtillus/química , Antocianinas/isolamento & purificação , Sítios de Ligação , Frutas/química , Ácido Gálico/química , Ácido Gálico/isolamento & purificação , Glucosídeos/isolamento & purificação , Humanos , Hidroquinonas/química , Cinética , Simulação de Dinâmica Molecular , Extratos Vegetais/química , Polifenóis/isolamento & purificação , Análise de Componente Principal , Ligação Proteica , Conformação Proteica em alfa-Hélice , Conformação Proteica em Folha beta , Domínios e Motivos de Interação entre Proteínas , Proteína Tirosina Fosfatase não Receptora Tipo 1/química , Especificidade por Substrato , TermodinâmicaRESUMO
The hypoglycaemic effects of two Ribes sp. i.e., anthocyanin-rich black currants (BC) were compared to green currants (GC), which are low in anthocyanins to establish which compounds are involved in the regulation of postprandial glycaemia. We determined the effect of the currants on inhibiting carbohydrate digestive enzymes (α-amylase, α-glucosidase), intestinal sugar absorption and transport across CaCo-2 cells. The digestion of these currants was modelled using in vitro gastrointestinal digestion (IVGD) to identify the metabolites present in the digested extracts by LC-MS/MS. Freeze-dried BC and IVDG extracts inhibited yeast α-glucosidase activity (P<.0001) at lower concentrations than acarbose, whereas GC and IVDG GC at the same concentrations showed no inhibition. BC and GC both showed significant inhibitory effects on salivary α-amylase (P<.0001), glucose uptake (P<.0001) and the mRNA expression of sugar transporters (P<.0001). Taken together this suggests that the anthocyanins which are high in BC have their greatest effect on postprandial hyperglycaemia by inhibiting α-glucosidase activity. Phytochemical analysis identified the phenolics in the currants and confirmed that freeze-dried BC contained higher concentrations of anthocyanins compared to GC (39.80 vs. 9.85 g/kg dry weight). Specific phenolics were also shown to inhibit salivary α-amylase, α-glucosidase, and glucose uptake. However, specific anthocyanins identified in BC which were low in GC were shown to inhibit α-glucosidase. In conclusion the anthocyanins in BC appear to regulate postprandial hyperglycaemia primarily but not solely by inhibiting α-glucosidase while other phenolics modulate salivary α-amylase, glucose uptake and sugar transporters which together could lower the associated risk of developing type-2 diabetes.
Assuntos
Antocianinas/química , Glucose/metabolismo , Inibidores de Glicosídeo Hidrolases/farmacologia , Hiperglicemia/metabolismo , Ribes/química , alfa-Amilases Salivares/metabolismo , Glicemia/análise , Células CACO-2 , Sobrevivência Celular , Cromatografia Líquida , Diabetes Mellitus Tipo 2/tratamento farmacológico , Diabetes Mellitus Tipo 2/metabolismo , Frutas/química , Trato Gastrointestinal/metabolismo , Humanos , Fenol/química , Fenol/metabolismo , Fenóis/química , Período Pós-Prandial , Açúcares/química , Espectrometria de Massas em Tandem , alfa-Glucosidases/metabolismoRESUMO
The aim of the present study was to determine if the enzyme Aspergillus niger prolyl endoprotease (ANPEP), which degrades the immunogenic proline-rich residues in gluten peptides, can be used in the development of new wheat products, suitable for gluten-sensitive (GS) individuals. We have carried out a double-blind, randomised, cross-over trial with two groups of adults; subjects, self-reporting benefits of adopting a gluten-free or low-gluten diet (GS, n 16) and a control non-GS group (n 12). For the trial, volunteers consumed four wheat breads: normal bread, bread treated with 0·8 or 1 % ANPEP and low-protein bread made from biscuit flour. Compared with controls, GS subjects had a favourable cardiovascular lipid profile - lower LDL (4·0 (sem 0·3) v. 2·8 (sem 0·2) mmol/l; P=0·008) and LDL:HDL ratio (3·2 (sem 0·4) v. 1·8 (sem 0·2); P=0·005) and modified haematological profile. The majority of the GS subjects followed a low-gluten lifestyle, which helps to reduce the gastrointestinal (GI) symptoms severity. The low-gluten lifestyle does not have any effect on the quality of life, fatigue or mental state of this population. Consumption of normal wheat bread increased GI symptoms in GS subjects compared with their habitual diet. ANPEP lowered the immunogenic gluten in the treated bread by approximately 40 %. However, when compared with the control bread for inducing GI symptoms, no treatment effects were apparent. ANPEP can be applied in the production of bread with taste, texture and appearance comparable with standard bread.
Assuntos
Aspergillus niger/enzimologia , Pão/análise , Dieta Livre de Glúten , Digestão , Intolerância Alimentar/dietoterapia , Glutens , Serina Endopeptidases/metabolismo , Doenças Cardiovasculares/sangue , HDL-Colesterol/sangue , LDL-Colesterol/sangue , Estudos Cross-Over , Método Duplo-Cego , Comportamento Alimentar , Feminino , Farinha/análise , Intolerância Alimentar/complicações , Proteínas Fúngicas/metabolismo , Gastroenteropatias/etiologia , Gastroenteropatias/prevenção & controle , Glutens/administração & dosagem , Glutens/efeitos adversos , Glutens/metabolismo , Hematologia , Humanos , Masculino , Pessoa de Meia-Idade , Prolil Oligopeptidases , Triticum/químicaRESUMO
The causes of post-restriction hyperphagia (PRH) represent a target for drug-based therapies to prevent obesity. However, the factors causing PRH are poorly understood. We show that, in mice, the extent of PRH was independent of the time under restriction, but depended on its severity, suggesting that PRH was driven by signals from altered body composition. Signals related to fat mass were important drivers. Circulating levels of leptin and TNFα were significantly depleted following caloric restriction (CR). We experimentally repleted their levels to match those of controls, and found that in both treatment groups the level of PRH was significantly blunted. These data establish a role for TNFα and leptin in the non-pathological regulation of energy homeostasis. Signals from adipose tissue, including but not limited to leptin and TNFα, regulate PRH and might be targets for therapies that support people engaged in CR to reduce obesity.
Assuntos
Restrição Calórica , Hiperfagia/sangue , Leptina/sangue , Fator de Necrose Tumoral alfa/sangue , Adiposidade , Animais , Composição Corporal , Dieta , Regulação da Expressão Gênica , Hiperfagia/genética , Hipotálamo/metabolismo , Hipotálamo/patologia , Masculino , CamundongosRESUMO
Hypothalamic energy balance genes have been examined in the context of seasonal body weight regulation in the Siberian hamster. Most of these long photoperiod (LD)/short photoperiod (SD) comparisons have been of tissues collected at a single point in the light-dark cycle. We examined the diurnal expression profile of hypothalamic genes in hamsters killed at 3-h intervals throughout the light-dark cycle after housing in LD or SD for 12 wk. Gene expression of neuropeptide Y, agouti-related peptide, proopiomelanocortin, cocaine- and amphetamine-regulated transcript, long-form leptin receptor, suppressor of cytokine signaling-3, melanocortin-3 receptor, melanocortin-4 receptor, and the clock gene Per1 as control were measured by in situ hybridization in hypothalamic nuclei. Effects of photoperiod on gene expression and leptin levels were generally consistent with previous reports. A clear diurnal variation was observed for Per1 in the suprachiasmatic nucleus in both photoperiods. Temporal effects on expression of energy balance genes were restricted to long-form leptin receptor in the arcuate nucleus and ventromedial nucleus, where similar diurnal expression profiles were observed, and melanocortin-4 receptor in the paraventricular nucleus; these effects were only observed in LD hamsters. There was no variation in serum leptin concentration. The 24-h profiles of hypothalamic energy balance gene expression broadly confirm photoperiodic differences that were observed previously, based on single time point comparisons, support the growing consensus that these genes have a limited role in seasonal body weight regulation, and further suggest limited involvement in daily rhythms of food intake.
Assuntos
Peso Corporal/genética , Ritmo Circadiano , Metabolismo Energético/genética , Regulação da Expressão Gênica , Hipotálamo/metabolismo , Proteínas do Tecido Nervoso/genética , Fotoperíodo , Animais , Cricetinae , Ingestão de Alimentos/genética , Leptina/sangue , Masculino , Proteínas do Tecido Nervoso/metabolismo , Neuropeptídeos/genética , Neuropeptídeos/metabolismo , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Phodopus , RNA Mensageiro/metabolismo , Receptores de Superfície Celular/genética , Receptores de Superfície Celular/metabolismo , Estações do Ano , Proteínas Supressoras da Sinalização de Citocina/genética , Proteínas Supressoras da Sinalização de Citocina/metabolismo , Núcleo Supraquiasmático/metabolismoRESUMO
Previously, 40% food restriction of male Siberian hamsters over 21 days in short-day (SD) photoperiod induced characteristic changes in expression of hypothalamic arcuate nucleus energy balance genes; mRNAs for neuropeptide Y, agouti-related peptide, and leptin receptor were upregulated, and those of proopiomelanocortin and cocaine- and amphetamine-regulated transcript were depressed. The present study examined the effect of refeeding hamsters for 6 days (approximately 50% recovery of weight differential) or 19 days (resumption of appropriate weight trajectory). Hyperphagia continued throughout refeeding, but differences in fat pad weights and leptin levels had disappeared after 19 days. Cocaine- and amphetamine-regulated transcript gene expression was depressed by prior restriction in both refed groups. The depressive effect of prior restriction on proopiomelanocortin gene expression had disappeared after 19 days of refeeding. There was no effect of prior food restriction on neuropeptide Y or agouti-related peptide gene expression. Expression of the anorexigenic brain-derived neurotrophic factor was downregulated in the ventromedial nucleus after SD exposure for 12 wk. In the SD food restriction study, there were effects of photoperiod on brain-derived neurotrophic factor gene expression but not of prior food restriction. Hypothalamic energy balance genes in the hamster respond asynchronously to return to a seasonally appropriate body weight. The achievement of this weight rather than the weight at which caloric restriction was imposed is the critical factor. The differential responses of hypothalamic energy balance genes to food restriction and refeeding are poorly characterized in any species, a critical issue given their potential relevance to human weight loss strategies that involve caloric restriction.
Assuntos
Restrição Calórica , Hipotálamo/metabolismo , Neuropeptídeos/biossíntese , Neuropeptídeos/genética , Fotoperíodo , Redução de Peso/fisiologia , Animais , Peso Corporal/fisiologia , Fator Neurotrófico Derivado do Encéfalo/genética , Fator Neurotrófico Derivado do Encéfalo/fisiologia , Cricetinae , Ingestão de Alimentos/fisiologia , Expressão Gênica , Leptina/sangue , Masculino , Tamanho do Órgão/fisiologia , Phodopus , RadioimunoensaioRESUMO
Contemporary foods and beverages that constitute the diets of adults and children almost certainly contribute to the obesity problem. To develop a model of childhood obesity, we examined the effects of feeding juvenile rats 2 solid diets, either alone or in combination [nonpurified control diet (C), high-energy (HE), or C+HE] with or without the liquid supplement Ensure (EN). Rats were fed C until 4 wk of age and then were assigned to 1 of 6 weight-matched groups that were fed C, HE, C+HE, C+EN, HE+EN, or C+HE+EN for 5 wk. EN accelerated weight gain and increased energy intake and adiposity irrespective of the solid diet consumed. Serum leptin concentrations were increased after the consumption of all diets when compared with C rats, but there was dissociation between leptin levels and adiposity. The type of solid diet had no effect on the expression of a panel of hypothalamic genes except for glutamate-decarboxylase-67. EN decreased mRNA for agouti-related peptide and neuropeptide Y in the arcuate nucleus and DYN in the paraventricular nucleus. Dynorphin and CART mRNA were decreased in the supraoptic retrochiasmatic nucleus. The reduction in orexigenic signaling in the hypothalamus suggests that overconsumption of EN is sensed by the hypothalamus but that any initiated physiological responses fail to compensate effectively and may be negated or overwhelmed by other systems. Providing diets in solid and liquid form, with choice, mimics more closely the human environment. Understanding the interactions between these diets and peripheral and central energy balance systems could be crucial in unraveling the events underlying human obesity and its early development.
Assuntos
Dieta , Hipotálamo/metabolismo , Obesidade/etiologia , Tecido Adiposo/metabolismo , Animais , Glicemia , Ingestão de Energia , Regulação da Expressão Gênica/genética , Leptina/sangue , Masculino , Obesidade/genética , Ratos , Ratos Sprague-Dawley , Triglicerídeos/sangueRESUMO
Nutritional factors have a critical influence during prenatal life on the development and regulation of networks involved in body weight and feeding regulation. To establish the influence of the macronutrient type on feeding regulatory mechanisms and more particularly on stimulatory pathways (galanin and orexins), we fed female rats on either a high-carbohydrate (HC), a high-fat (HF), or a well-balanced control diet during gestation and lactation, and measured peptide expression in the hypothalamus and important hormones (leptin, insulin) in their pups at weaning. HF weanlings were 30% lighter than control and HC pups (P<0.001). They were characterized by reduced plasma glucose and insulin levels (P<0.01 or less). Their galanin and orexin systems were upregulated as shown by the significant augmentation of mRNA expression in the paraventricular nucleus and lateral hypothalamus, respectively. Inhibitory peptides like corticotropin-releasing hormone and neurotensin were not affected by this dietary treatment during early life. There was, therefore, a more intense drive to eat in HF pups, perhaps to compensate for the lower body weight at weaning. HF diets during early life had meanwhile some positive consequences: the lower metabolic profile might be beneficial in precluding the development of obesity and metabolic syndrome later in life. This is however valid only if the orexigenic drive is normalized after weaning.
Assuntos
Envelhecimento/fisiologia , Gorduras na Dieta/administração & dosagem , Gorduras na Dieta/metabolismo , Hipotálamo/metabolismo , Neuropeptídeos/biossíntese , Peptídeos/metabolismo , Envelhecimento/genética , Animais , Peso Corporal/genética , Feminino , Galanina/biossíntese , Galanina/genética , Hipotálamo/química , Hipotálamo/fisiologia , Peptídeos e Proteínas de Sinalização Intracelular/genética , Neuropeptídeos/genética , Neuropeptídeos/metabolismo , Neurotensina/metabolismo , Orexinas , Hormônios Peptídicos/metabolismo , Peptídeos/genética , RNA Mensageiro/metabolismo , Ratos , Ratos Long-EvansRESUMO
To survive winter the Siberian hamster has evolved profound physiological and behavioral adaptations, including a moult to winter pelage, regression of the reproductive axis, onset of daily torpor and increased capacity for thermogenesis. However, one of the most striking adaptations is the catabolism of intraabdominal and sc fat reserves contributing to the loss of up to 40% of body weight. These physiological and behavioral adaptations are photoperiodically driven, yet neither the site(s) in the brain nor the molecular mechanism(s) involved in the regulation of these profound adaptations is known. Here we report a dynamic regulation of gene expression in a dorsal region of the medial posterior area of the arcuate nucleus (dmpARC) of the Siberian and Syrian hamster brain in response to altered photoperiod. We show mRNA for the histamine H3 receptor is down-regulated and VGF is up-regulated in the dmpARC in hamsters switched from long- to short-day photoperiod. These data provide further evidence to support the view that the dmpARC is a major site to relay photoperiodic changes and as a site for the long-term regulation of seasonal physiology and behavior.
Assuntos
Núcleo Arqueado do Hipotálamo/metabolismo , Regulação da Expressão Gênica , Fotoperíodo , Proteínas/genética , RNA Mensageiro/análise , Receptores Histamínicos H3/genética , Animais , Cricetinae , Histamina/análise , Histidina Descarboxilase/genética , Humanos , Masculino , Mesocricetus , Glândula Pineal/fisiologia , Receptores Histamínicos H3/fisiologia , Transdução de SinaisRESUMO
This study reports novel events related to photoperiodic programming of the neuroendocrine hypothalamus. To investigate photoperiod-responsive genes, Siberian hamsters were maintained in long or short photoperiods that generate physiological states of obesity or leanness. Microarray expression analysis first identified CRBP1 as a photoperiod-responsive gene, and then further studies using in situ hybridization and immunocytochemistry revealed that expression levels of several related retinoid-signaling genes were modulated in response to photoperiod changes. Genes of the retinoid-signaling pathway, encoding nuclear receptors (RXR/RAR) and retinoid binding proteins (CRBP1 and CRABP2) are photoperiodically regulated in the dorsal tuberomamillary nucleus (DTM): Their expression is significantly lower in short photoperiods and parallels body weight decreases. Studies in pinealectomized hamsters confirm that the pineal melatonin rhythm is necessary for these seasonal changes, and studies in testosterone-treated hamsters reveal that these changes in gene expression are not the secondary consequence of photoperiod-induced changes in steroid levels. Comparative studies using Syrian hamsters, which show divergent seasonal body weight responses to Siberian hamsters when exposed to short photoperiods, showed a distinct pattern of changes in retinoid gene expression in the DTM in response to a change in photoperiod. We infer that the DTM may be an important integrating center for photoperiodic control of seasonal physiology and suggest that the changes in retinoid X receptor gamma expression may be associated with seasonal changes in body weight and energy metabolism.
Assuntos
Peso Corporal/fisiologia , Hipotálamo/fisiologia , Fotoperíodo , Receptores do Ácido Retinoico/genética , Fatores de Transcrição/genética , Animais , Cricetinae , Metabolismo Energético/fisiologia , Expressão Gênica/fisiologia , Masculino , Phodopus , RNA Mensageiro/análise , Receptores X de Retinoides , Proteínas de Ligação ao Retinol/genética , Proteínas Celulares de Ligação ao Retinol , Transdução de Sinais/fisiologiaRESUMO
We present the first evidence that suppressor of cytokine signaling-3 (SOCS3), a protein inhibiting Janus kinase/signal transducer and activator of transcription (STAT) signaling distal of the leptin receptor, conveys seasonal changes in leptin sensitivity in the Siberian hamster. Food deprivation (48 h) reduced SOCS3 gene expression in hamsters acclimated to either long (LD) or short (SD) photoperiods, suggesting that leptin signals acute starvation regardless of photoperiod. However, SOCS3 mRNA levels were substantially lower in the hypothalamic arcuate nucleus of hamsters acclimated to SD than in those raised in LD. In juveniles raised in LD, a rapid increase in SOCS3 mRNA was observed within 4 d of weaning, which was completely prevented by transfer to SD on the day of weaning. The early increase in SOCS3 gene expression in juvenile hamsters in LD clearly preceded the establishment of different body weight trajectories in LD and SD. In adult LD hamsters, SOCS3 mRNA was maintained at an elevated level despite the chronic food restriction imposed to lower body weight and serum leptin to or even below SD levels. A single injection of leptin in SD hamsters elevated SOCS3 mRNA to LD levels, whereas leptin treatment had no effect on SOCS3 gene expression in LD hamsters. Our results suggest that the development of leptin resistance in LD-acclimated hamsters involves SOCS3-mediated suppression of leptin signaling in the arcuate nucleus. Increased SOCS3 expression in LD hamsters is independent of body fat and serum leptin levels, suggesting that the photoperiod is able to trigger the biannual reversible switch in leptin sensitivity.
Assuntos
Núcleo Arqueado do Hipotálamo/fisiologia , Leptina/fisiologia , Fotoperíodo , Proteínas Repressoras/genética , Fatores de Transcrição/genética , Aclimatação/fisiologia , Fatores Etários , Animais , Peso Corporal/fisiologia , Cricetinae , Metabolismo Energético/fisiologia , Feminino , Privação de Alimentos/fisiologia , Expressão Gênica/efeitos dos fármacos , Expressão Gênica/fisiologia , Leptina/farmacologia , Masculino , Phodopus , RNA Mensageiro/análiseRESUMO
In young (35- to 56-day-old) and middle-aged (9-mo-old) wild-type (+/+) and melanocortin-4 receptor (MC4R)-deficient (+/-, -/-) mice, expressions of neuropeptide Y (NPY), agouti-related protein (AGRP), pro-opiomelanocortin (POMC), and cocaine-and-amphetamine-regulated transcript (CART) were analyzed in the arcuate nucleus (ARC) and adjacent regions comprising the dorsomedial (DMN) and ventromedial (VMN) nucleus. In the ARC of young mice, NPY and AGRP expression increased and POMC and CART expression decreased with body fat content. Adjusting for the influence of body fat content by ANCOVA showed that the levels of NPY, POMC, and CART were highest and of AGRP lowest in young -/- mice. In the middle-aged mice, feedback from body fat content was weakened. For -/- mice ANCOVA revealed higher NPY and AGRP, lower POMC, and unchanged CART expression levels relative to young -/- mice. In the DMN and VMN, POMC and AGRP signals were absent at each age. CART was expressed in the DMN independent of age, fat content, and genotype. For NPY expression, an age-dependent induction was found in the DMN and VMN; it was absent in the young but present in the middle-aged mice, showing close positive correlations between body fat content and the numbers of NPY-labeled cells which were further enhanced in -/- mice. Thus MC4R deficiency augments age-induced NPY expression in the DMN and VMN with no feedback from body fat content. Negative feedback control by body fat content on ARC neuropeptide expression is present in young animals but vanishes with age and is modulated by MC4R deficiency.
Assuntos
Tecido Adiposo/metabolismo , Envelhecimento/metabolismo , Deleção de Genes , Hipotálamo/metabolismo , Neuropeptídeos/metabolismo , Receptor Tipo 4 de Melanocortina/deficiência , Receptor Tipo 4 de Melanocortina/metabolismo , Proteína Relacionada com Agouti , Animais , Núcleo Arqueado do Hipotálamo/metabolismo , Genótipo , Peptídeos e Proteínas de Sinalização Intercelular , Leptina/sangue , Camundongos , Camundongos Knockout , Modelos Animais , Proteínas do Tecido Nervoso/análise , Proteínas do Tecido Nervoso/metabolismo , Neuropeptídeo Y/análise , Neuropeptídeo Y/metabolismo , Obesidade/sangue , Obesidade/genética , Obesidade/metabolismo , Pró-Opiomelanocortina/análise , Pró-Opiomelanocortina/metabolismo , Proteínas/análise , Proteínas/metabolismo , Receptor Tipo 4 de Melanocortina/genéticaRESUMO
Cocaine- and amphetamine-regulated transcript (CART) mRNA is expressed in a number of hypothalamic nuclei including the arcuate nucleus (ARC). An increase in CART gene expression in the ARC of juvenile female Siberian hamsters (Phodopus sungorus) 14 days after transfer to short photoperiod at weaning and prior to major divergence of body weight trajectory in this seasonal mammal implicates CART in the induction of programmed weight change. In the current series of experiments, elevated CART mRNA in short photoperiod juvenile female animals relative to long photoperiod controls was apparent throughout the caudal-rostral extent of the ARC after 14 days, but was not observed when short photoperiod exposure was limited to 4-7 days. Elevated CART gene expression was also observed in juvenile males 14 days after transfer to short photoperiod at weaning, in adult female hamsters 14 days after transfer to short photoperiod and in adult male hamsters 21 days after transfer to short photoperiod. There were no consistent trends in expression levels of other energy balance-related genes with these relatively short duration photoperiod manipulations, suggesting that CART may be involved in short photoperiod-programmed body weight regulation.
Assuntos
Núcleo Arqueado do Hipotálamo/fisiologia , Regulação da Expressão Gênica/efeitos da radiação , Proteínas do Tecido Nervoso/biossíntese , Proteínas do Tecido Nervoso/genética , Fotoperíodo , Animais , Núcleo Arqueado do Hipotálamo/metabolismo , Peso Corporal/fisiologia , Cricetinae , Feminino , Masculino , Neuropeptídeos/genética , Neuropeptídeos/metabolismo , Neurotransmissores/genética , Neurotransmissores/metabolismo , Pró-Opiomelanocortina/genética , Pró-Opiomelanocortina/metabolismo , RNA Mensageiro/análise , RNA Mensageiro/biossíntese , Receptores de Neuropeptídeos/genética , Receptores de Neuropeptídeos/metabolismo , Fatores Sexuais , DesmameRESUMO
Previous studies on mice with melanocortin-4 receptor gene (MC4r) knockout have focused on obese adults. Because humans with functional MC4r mutations show early-onset obesity, we determined the onset of excessive fat deposition in 10- to 56-day-old mice, taking into account sex and litter influences. Total body fat content of MC4r-/- on day 35 and MC4r+/- on day 56 significantly exceeds that of MC4r+/+. Plasma leptin levels increase in proportion to fat mass. According to cumulative food intake and energy expenditure measurements from day 21 to 35, onset of excessive fat deposition in MC4r-/- is fueled by hyperphagia and counteracted partially by hypermetabolism. In 35- to 56-day-old mice, arcuate nucleus neuropeptide Y (NPY) mRNA decreases and pro-opiomelanocortin (POMC) mRNA increases with fat content and plasma leptin levels independently of genotype. Taking into account fat content by ANCOVA reveals, however, increases in both NPY mRNA and POMC mRNA due to melanocortin-4 receptor (MC4R) deficiency. We conclude that hyperphagia, not hypometabolism, is the primary disturbance initiating excessive fat deposition in MC4R-deficient mice at weaning and that the overall changes in NPY and POMC expression tend to antagonize the onset of excessive fat deposition.
Assuntos
Metabolismo Energético/genética , Hiperfagia/genética , Obesidade/genética , Receptores da Corticotropina/deficiência , Receptores da Corticotropina/genética , Tecido Adiposo/crescimento & desenvolvimento , Animais , Composição Corporal/genética , Ingestão de Alimentos/genética , Ingestão de Energia/genética , Feminino , Genótipo , Hiperfagia/sangue , Hiperfagia/fisiopatologia , Leptina/sangue , Masculino , Camundongos , Camundongos Knockout , Neuropeptídeo Y/biossíntese , Obesidade/sangue , Obesidade/fisiopatologia , Fragmentos de Peptídeos/biossíntese , Pró-Opiomelanocortina/biossíntese , Receptor Tipo 4 de Melanocortina , Receptores da Corticotropina/fisiologiaRESUMO
The pars tuberalis (PT) region of the anterior pituitary plays a physiological role in seasonal animals. The primary signal transduction mechanism of the melatonin receptor in this tissue is an inhibition of cAMP signaling. However, nothing is known about the endocrine signals that activate cAMP synthesis in the cells of the PT, as previous studies relied on the pharmacological tool, forskolin, to stimulate cAMP synthesis. Here we show that pituitary adenylate cyclase-activating polypeptide (PACAP) activates cAMP synthesis in the cells of the PT. The pharmacology of cAMP activation by PACAP peptides suggests that cAMP activation is mediated by the type I PACAP receptor. PACAP treatment of PT cells results in cellular responses that are consistent with cAMP activation in these cells, including activation of MAPK and elevation of melatonin receptor mt1 mRNA expression. These responses can be inhibited by melatonin, demonstrating that activation of cAMP occurs within the melatonin-responsive cells. However, although PACAP activates cAMP in the cells of the PT, the effect of PACAP may not be direct, as colocalization in situ hybridization studies demonstrates that the type I PACAP receptor and the melatonin mt1 receptor do not colocalize on the cells of the PT.