RESUMO
Introduction: Neuropeptide Y (NPY) signaling in the brain plays an important role in energy regulation, and is altered during diet-induced obesity. Yet, NPY function during the consumption of specific diet components remains to be fully determined. We have previously demonstrated that consumption of a saturated fat component (free-choice high-fat; fcHF), a sucrose solution (high-sugar; fcHS), or both (fcHFHS) combined with a standard diet (chow and water) has diverse effects on Npy expression in the arcuate nucleus and the sensitivity to intraventricular NPY administration. Arcuate NPY neurons project to the lateral hypothalamus (LHA), and NPY administration in the LHA potently promotes chow intake in rats on a standard diet. However, it is currently unclear if short-term consumption of a palatable free-choice diet alters NPY function in the LHA. Therefore, we assessed the effects of intra-LHA NPY administration on intake in rats following one-week consumption of a fcHF, fcHS, or fcHFHS diet.Methods: Male Wistar rats consumed a fcHF, fcHS, fcHFHS, or control (CHOW) diet for one week before NPY (0.3â µg / 0.3â µL) or phosphate-buffered saline (0.3â µL) was administered into the LHA. Intake was measured 2h later. fcHFHS-fed rats were divided into high-fat (fcHFHS-hf) and low-fat (fcHFHS-lf) groups based on differences in basal fat intake.Results: Intra-LHA NPY administration increased chow intake in fcHFHS- (irrespective of basal fat intake), fcHF- and CHOW-fed rats. Intra-LHA NPY infusion increased fat intake in fcHF-, fcHFHS-hf, but not fcHFHS-lf, rats. Intra-LHA NPY infusion did not increase caloric intake in fcHS-fed rats.Discussion: Our data demonstrate that the effects of intra-LHA NPY on caloric intake differ depending on the consumption of a fat or sugar component, or both, in a free-choice diet. Our data also indicate that baseline preference for the fat diet component modulates the effects of intra-LHA NPY in fcHFHS-fed rats.
Assuntos
Região Hipotalâmica Lateral , Neuropeptídeo Y , Animais , Dieta Hiperlipídica , Região Hipotalâmica Lateral/metabolismo , Hipotálamo/metabolismo , Masculino , Neuropeptídeo Y/metabolismo , Ratos , Ratos Wistar , SacaroseRESUMO
Fibroblast growth factor 23 (FGF23) is an endocrine growth factor and known to play a pivotal role in phosphate homeostasis. Interestingly, several studies point towards a function of FGF23 in the hypothalamus. FGF23 classically activates the FGF receptor 1 in the presence of the co-receptor αKlotho, of both gene expression in the brain was previously established. However, studies on gene and protein expression of FGF23 in the brain are scarce and have been inconsistent. Therefore, our aim was to localise FGF23 gene and protein expression in the rat brain with focus on the hypothalamus. Also, we investigated the protein expression of αKlotho. Adult rat brains were used to localise and visualise FGF23 and αKlotho protein in the hypothalamus by immunofluorescence labelling. Furthermore, western blots were used for assessing hypothalamic FGF23 protein expression. FGF23 gene expression was investigated by qPCR in punches of the arcuate nucleus, lateral hypothalamus, paraventricular nucleus, choroid plexus, ventrolateral thalamic nucleus and the ventromedial hypothalamus. Immunoreactivity for FGF23 and αKlotho protein was found in the hypothalamus, third ventricle lining and the choroid plexus. Western blot analysis of the hypothalamus confirmed the presence of FGF23. Gene expression of FGF23 was not detected, suggesting that the observed FGF23 protein is not brain-derived. Several FGF receptors are known to be present in the brain. Therefore, we conclude that the machinery for FGF23 signal transduction is present in several brain areas, indeed suggesting a role for FGF23 in the brain.
Assuntos
Fatores de Crescimento de Fibroblastos , Glucuronidase , Animais , Fator de Crescimento de Fibroblastos 23 , Fatores de Crescimento de Fibroblastos/genética , Fatores de Crescimento de Fibroblastos/metabolismo , Glucuronidase/metabolismo , Hipotálamo/metabolismo , Ratos , Receptores de Fatores de Crescimento de Fibroblastos/metabolismoRESUMO
Recent studies have shown that meal timing throughout the day contributes to maintaining or regaining weight after hypocaloric diets. Although brain serotonin and dopamine are well known to be involved in regulating feeding, it is unknown whether meal timing during energy restriction affects these neurotransmitter systems. We studied the effect of a 4 wk hypocaloric diet with either 50% of daily calories consumed at breakfast (BF group) or at dinner (D group) on hypothalamic and thalamic serotonin transporter (SERT) binding and on striatal dopamine transporter (DAT) binding. The BF and D groups lost a similar amount of weight. Striatal DAT and thalamic SERT binding increased in the BF group, while decreasing in the D group after the diet (ΔDAT 0.37 ± 0.63 vs. -0.53 ± 0.77, respectively; P = 0.005; ΔSERT 0.12 ± 0.25 vs. -0.13 ± 0.26 respectively, P = 0.032). Additional voxel-based analysis showed an increase in DAT binding in the ventral striatum in the BF group and a decrease in the dorsal striatum in the D group. During weight loss, striatal DAT and thalamic SERT binding increased weight independently when 50% of daily calories were consumed at breakfast, whereas it decreased when caloric intake was highest at dinner. These findings may contribute to the earlier reported favorable effect of meal timing on weight maintenance after hypocaloric diets.-Versteeg, R. I., Schrantee, A., Adriaanse, S. M., Unmehopa, U. A., Booij, J., Reneman, L., Fliers, E., la Fleur, S. E., Serlie, M. J. Timing of caloric intake during weight loss differentially affects striatal dopamine transporter and thalamic serotonin transporter binding.
Assuntos
Proteínas da Membrana Plasmática de Transporte de Dopamina/metabolismo , Ingestão de Energia/fisiologia , Obesidade/metabolismo , Proteínas da Membrana Plasmática de Transporte de Serotonina/metabolismo , Redução de Peso/fisiologia , Idoso , Idoso de 80 Anos ou mais , Peso Corporal/fisiologia , Corpo Estriado/metabolismo , Dieta Redutora , Dopamina/metabolismo , Comportamento Alimentar/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Serotonina/metabolismo , Fatores de TempoRESUMO
Consumption of fat and sugar induces hyperphagia and increases the prevalence of obesity and diabetes type 2. Low-grade inflammation in the hypothalamus, a key brain area involved in the regulation of energy homeostasis is shown to blunt signals of satiety after long term high fat diet. The fact that this mechanism can be activated after a few days of hyperphagia before apparent obesity is present led to our hypothesis that hypothalamic inflammation is induced with fat and sugar consumption. Here, we used a free-choice high-fat high-sugar (fcHFHS) diet-induced obesity model and tested the effects of differential overnight nutrient intake during the final experimental night on markers of hypothalamic inflammation. Male Wistar rats were fed a control diet or fcHFHS diet for one week, and assigned to three different feeding conditions during the final experimental night: 1) fcHFHS-fed, 2) fed a controlled amount of chow diet, or 3) fasted. RT-qPCR and Western blot were utilized to measure hypothalamic gene and protein expression, of cytokines and intermediates of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway. Lastly, we investigated the effects of acute fat intake on markers of hypothalamic inflammation in fat-naïve rats. fcHFHS-fed rats consumed more calories, increased adipose tissue, and showed elevated expression of hypothalamic inflammation markers (increased phosphorylation of NF-κB protein, Nfkbia and Il6 gene expression) compared to chow-fed rats. These effects were evident in rats consuming relative high amounts of fat. Removal of the fat and sugar, or fasting, during the final experimental night ameliorated hypothalamic inflammation. Finally, a positive correlation was observed between overnight acute fat consumption and hypothalamic NF-κB phosphorylation in fat-naïve rats. Our data indicate that one week of fcHFHS diet, and especially the fat component, promotes hypothalamic inflammation, and removal of the fat and sugar component reverses these detrimental effects.
Assuntos
Ingestão de Alimentos , Hipotálamo/fisiopatologia , Inflamação/fisiopatologia , Obesidade/fisiopatologia , Adiposidade , Animais , Citocinas/sangue , Citocinas/genética , Dieta Hiperlipídica , Gorduras na Dieta/administração & dosagem , Açúcares da Dieta/administração & dosagem , Modelos Animais de Doenças , Privação de Alimentos , Hiperfagia/dietoterapia , Hiperfagia/etiologia , Leptina/sangue , Masculino , NF-kappa B/genética , NF-kappa B/metabolismo , Fosforilação , Ratos , Ratos WistarRESUMO
BACKGROUND: Altered brain dopaminergic and serotonergic pathways have been shown in obese rodents and humans, but it is unknown whether this is related to obesity per se or to the metabolic derangements associated with obesity. METHODS: We performed a case-control study in insulin-sensitive obese (ISO) and insulin-resistant obese (IRO) subjects (n = 12) and age-matched lean controls (n = 8) and measured serotonin transporter (SERT) binding in the whole diencephalon and specifically in the hypothalamus, as well as dopamine transporter (DAT) binding in the striatum using 123I- FP-CIT single-photon emission computed tomography. We assessed insulin sensitivity using the homeostatic model assessment of insulin resistance. RESULTS: BMI did not differ between the IRO and ISO subjects. SERT binding in the diencephalon was significantly lower in IRO than in ISO subjects, but was not different between lean and obese subjects. SERT binding in the hypothalamus tended to be reduced in obese versus lean subjects, but was not different between IRO and ISO subjects. Striatal DAT binding was similar between lean and obese subjects as well as between ISO and IRO subjects. CONCLUSIONS: We conclude that SERT binding in the diencephalon is reduced in insulin-resistant subjects independently of body weight, while hypothalamic SERT binding tends to be lower in obesity, with no difference between insulin-resistant and insulin-sensitive subjects. This suggests that the metabolic perturbations associated with obesity independently affect SERT binding within the diencephalon.
Assuntos
Diencéfalo/metabolismo , Resistência à Insulina/fisiologia , Obesidade/metabolismo , Proteínas da Membrana Plasmática de Transporte de Serotonina/metabolismo , Adulto , Índice de Massa Corporal , Mapeamento Encefálico , Estudos de Casos e Controles , Diencéfalo/diagnóstico por imagem , Proteínas da Membrana Plasmática de Transporte de Dopamina/metabolismo , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Obesidade/diagnóstico por imagem , Ligação Proteica , Compostos Radiofarmacêuticos , Tomografia Computadorizada de Emissão de Fóton Único , TropanosRESUMO
BACKGROUND: Growing evidence demonstrates the role of the striatal dopamine system in the regulation of glucose metabolism. Treatment with dopamine antagonists is associated with insulin resistance and hyperglycemia, while dopamine agonists are used in treatment of type 2 diabetes. The mechanism underlying striatal dopamine effects in glucose metabolism, however is not fully understood. Here, we provide mechanistic insights into the role of nucleus accumbens shell (sNAc) dopaminergic signaling in systemic glucose metabolism. METHODS: Endogenous glucose production (EGP), blood glucose and mRNA expression in the lateral hypothalamic area (LHA) in male Wistar rats were measured following infusion of vanoxerine (VNX, dopamine reuptake inhibitor) in the sNAc. Thereafter, we analyzed projections from sNAc Drd1-expressing neurons to LHA using D1-Cre male Long-Evans rats, Cre-dependent viral tracers and fluorescence immunohistochemistry. Brain slice electrophysiology in adult mice was used to study spontaneous excitatory postsynaptic currents of sNAc Drd1-expressing neurons following VNX application. Finally, we assessed whether GABAergic LHA activity and hepatic vagal innervation were required for the effect of sNAc-VNX on glucose metabolism by combining infusion of sNAc-VNX with LHA-bicuculline, performing vagal recordings and combining infusion of sNAc-VNX with hepatic vagal denervation. RESULTS: VNX infusion in the sNAc strongly decreased endogenous glucose production, prevented glucose increases over time, reduced Slc17A6 and Hcrt mRNA in LHA, and increased vagal activity. Furthermore, sNAc Drd1-expressing neurons increased spontaneous firing following VNX application, and viral tracing of sNAc Drd1-expressing neurons revealed direct projections to LHA with on average 67 % of orexin cells directly targeted by sNAc Drd1-expressing neurons. Importantly, the sNAc-VNX-induced effect on glucose metabolism was dependent on GABAergic signaling in the LHA and on intact hepatic vagal innervation. CONCLUSIONS: We show that sNAc dopaminergic signaling modulates hepatic glucose metabolism through GABAergic inputs to glutamatergic LHA cells and hepatic vagal innervation. This demonstrates that striatal control of glucose metabolism involves a dopaminergic sNAc-LHA-liver axis and provides a potential explanation for the effects of dopamine agonists and antagonists on glucose metabolism.
Assuntos
Diabetes Mellitus Tipo 2 , Região Hipotalâmica Lateral , Ratos , Masculino , Camundongos , Animais , Região Hipotalâmica Lateral/metabolismo , Núcleo Accumbens/metabolismo , Dopamina/metabolismo , Roedores/metabolismo , Agonistas de Dopamina/metabolismo , Agonistas de Dopamina/farmacologia , Diabetes Mellitus Tipo 2/metabolismo , Ratos Wistar , Ratos Long-Evans , Glucose/metabolismo , Fígado/metabolismo , RNA Mensageiro/metabolismoRESUMO
Physical exercise training has been positioned as a behavioral strategy to prevent or alleviate obesity via promotion of energy expenditure as well as modulation of energy intake resulting from changes in dietary preference. Brain adaptations underlying the latter process are incompletely understood. Voluntary wheel running (VWR) is a self-reinforcing rodent paradigm that mimics aspects of human physical exercise training. Behavioral and mechanistic insight from such fundamental studies can help optimize therapies that improve body weight and metabolic health based on physical exercise training in humans. To assess the effects of VWR on dietary self-selection, male Wistar rats were given access to a two-component "no-choice" control diet (CD; consisting of prefabricated nutritionally complete pellets and a bottle with tap water) or a four-component free-choice high-fat high-sucrose diet (fc-HFHSD; consisting of a container with prefabricated nutritionally complete pellets, a dish with beef tallow, a bottle with tap water, and a bottle with 30% sucrose solution). Metabolic parameters and baseline dietary self-selection behavior during sedentary (SED) housing were measured for 21 days, after which half of the animals were allowed to run on a vertical running wheel (VWR) for another 30 days. This resulted in four experimental groups (SEDCD, SEDfc-HFHSD, VWRCD, and VWRfc-HFHSD). Gene expression of opioid and dopamine neurotransmission components, which are associated with dietary self-selection, was assessed in the lateral hypothalamus (LH) and nucleus accumbens (NAc), two brain regions involved in reward-related behavior, following 51 and 30 days of diet consumption and VWR, respectively. Compared to CD controls, consumption of fc-HFHSD before and during VWR did not alter total running distances. VWR and fc-HFHSD had opposite effects on body weight gain and terminal fat mass. VWR transiently lowered caloric intake and increased and decreased terminal adrenal and thymus mass, respectively, independent of diet. VWR during fc-HFHSD consumption consistently increased CD self-selection, had an acute negative effect on fat self-selection, and a delayed negative effect on sucrose solution self-selection compared to SED controls. Gene expression of opioid and dopamine neurotransmission components in LH and NAc were unaltered by fc-HFHSD or VWR. We conclude that VWR modulates fc-HFHSD component self-selection in a time-dependent manner in male Wistar rats.
Assuntos
Analgésicos Opioides , Atividade Motora , Ratos , Animais , Bovinos , Masculino , Humanos , Ratos Wistar , Analgésicos Opioides/farmacologia , Dopamina/farmacologia , Dieta Hiperlipídica , Peso Corporal , Sacarose/farmacologiaRESUMO
BACKGROUND AND AIMS: Serotonergic and dopaminergic systems in the brain are essential for homeostatic and reward-associated regulation of food intake and systemic energy metabolism. It is largely unknown how fasting influences these systems or if such effects are altered in humans with obesity. We therefore aimed to evaluate the effects of fasting on hypothalamic/thalamic serotonin transporter (SERT) and striatal dopamine transporter (DAT) availability in lean subjects and subjects with obesity. METHODS: In this randomized controlled cross-over trial, we assessed the effects of 12 vs 24â¯h of fasting on SERT and DAT availability in the hypothalamus/thalamus and striatum, respectively, using SPECT imaging in 10 lean men and 10 men with obesity. RESULTS: As compared with the 12-h fast, a 24-h fast increased hypothalamic SERT availability in lean men, but not in men with obesity. We observed high inter-individual variation in the effects of fasting on thalamic SERT and striatal DAT, with no differences between lean men and those with obesity. In all subjects, fasting-induced increases in circulating free fatty acid (FFA) concentrations were associated with an increase in hypothalamic SERT availability and a decrease in striatal DAT availability. Multiple regression analysis showed that changes in plasma insulin and FFAs together accounted for 44% of the observed variation in striatal DAT availability. CONCLUSION: Lean men respond to prolonged fasting by increasing hypothalamic SERT availability, whereas this response is absent in men with obesity. Inter-individual differences in the adaptations of the cerebral serotonergic and dopaminergic systems to fasting may, in part, be explained by changes in peripheral metabolic signals of fasting, including FFAs and insulin.
Assuntos
Jejum , Hipotálamo/fisiopatologia , Obesidade/metabolismo , Proteínas da Membrana Plasmática de Transporte de Serotonina/metabolismo , Idoso , Estudos de Casos e Controles , Corpo Estriado/diagnóstico por imagem , Corpo Estriado/metabolismo , Estudos Cross-Over , Proteínas da Membrana Plasmática de Transporte de Dopamina/metabolismo , Ácidos Graxos não Esterificados/metabolismo , Humanos , Hipotálamo/diagnóstico por imagem , Hipotálamo/metabolismo , Insulina/metabolismo , Masculino , Pessoa de Meia-Idade , Tomografia Computadorizada de Emissão de Fóton ÚnicoRESUMO
OBJECTIVE: Eating out of phase with the endogenous biological clock alters clock and metabolic gene expression in rodents and can induce obesity and type 2 diabetes mellitus. Diet composition can also affect clock gene expression. This study assessed the combined effect of diet composition and feeding time on (1) body composition, (2) energy balance, and (3) circadian expression of hepatic clock and metabolic genes. METHODS: Male Wistar rats were fed a chow or a free-choice high-fat, high-sugar (fcHFHS) diet, either ad libitum or with food access restricted to either the light or dark period. Body weight, adiposity, and hepatic fat accumulation as well as hepatic clock and metabolic mRNA expression were measured after 5 weeks of the diet. Energy expenditure was measured using calorimetric cages. RESULTS: Animals with access to the fcHFHS diet only during the light period showed more hepatic fat accumulation than fcHFHS dark-fed animals despite less calories consumed. In contrast, within the chow-fed groups, light-fed animals showed the lowest hepatic fat content, but they also showed the lowest caloric intake. Locomotor activity and heat production followed feeding times, except in the fcHFHS light-fed group. Hepatic clock and metabolic gene expression rhythms also followed timing of food intake. Yet, in the fcHFHS light-fed animals, clock gene expression appeared 3 hours advanced compared with chow light-fed animals, an effect not observed in the fcHFHS dark-fed animals. CONCLUSIONS: An fcHFHS diet consumed in the light period promotes hepatic fat accumulation and advances clock gene expression in male Wistar rats, likely because of a mismatch between energy intake and expenditure.
Assuntos
Dieta/métodos , Fígado Gorduroso/genética , Fígado Gorduroso/fisiopatologia , Comportamento Alimentar/fisiologia , Expressão Gênica/genética , Animais , Modelos Animais de Doenças , Masculino , Ratos , Ratos WistarRESUMO
The hypothalamic neuropeptide Y (NPY) circuitry is a key regulator of feeding behavior. NPY also acts in the mesolimbic dopaminergic circuitry, where it can increase motivational aspects of feeding behavior through effects on dopamine output in the nucleus accumbens (NAc) and on neurotransmission in the ventral tegmental area (VTA). Endogenous NPY in the NAc originates from local interneurons and afferent projections from the hypothalamic arcuate nucleus (Arc). However, the origin of endogenous NPY in the VTA is unknown. We determined, in normal-weight male Wistar rats, if the source of VTA NPY is local, and/or whether it is derived from VTA-projecting neurons. Immunocytochemistry, in situ hybridization and RT-qPCR were utilized, when appropriate in combination with colchicine treatment or 24 hr fasting, to assess NPY/Npy expression locally in the VTA. Retrograde tracing using cholera toxin beta (CTB) in the VTA, fluorescent immunocytochemistry and confocal microscopy were used to determine NPY-immunoreactive afferents to the VTA. NPY in the VTA was observed in fibers, but not following colchicine pretreatment. No NPY- or Npy-expressing cell bodies were observed in the VTA. Fasting for 24 hr, which increased Npy expression in the Arc, failed to induce Npy expression in the VTA. Double-labeling with CTB and NPY was observed in the Arc and in the ventrolateral medulla. Thus, VTA NPY originates from the hypothalamic Arc and the ventrolateral medulla of the brainstem in normal-weight male Wistar rats. These afferent connections link hypothalamic and brainstem processing of physiologic state to VTA-driven motivational behavior.
Assuntos
Neurônios Aferentes/citologia , Neurônios Aferentes/metabolismo , Neuropeptídeo Y/metabolismo , Área Tegmentar Ventral/citologia , Área Tegmentar Ventral/metabolismo , Vias Aferentes/citologia , Vias Aferentes/metabolismo , Animais , Núcleo Arqueado do Hipotálamo/citologia , Núcleo Arqueado do Hipotálamo/metabolismo , Imuno-Histoquímica , Masculino , Bulbo/citologia , Bulbo/metabolismo , Microscopia Confocal , Técnicas de Rastreamento Neuroanatômico , Pró-Opiomelanocortina/metabolismo , Ratos WistarRESUMO
Humans have engineered a dietary environment that has driven the global prevalence of obesity and several other chronic metabolic diseases to pandemic levels. To prevent or treat obesity and associated comorbidities, it is crucial that we understand how our dietary environment, especially in combination with a sedentary lifestyle and/or daily-life stress, can dysregulate energy balance and promote the development of an obese state. Substantial mechanistic insight into the maladaptive adaptations underlying caloric overconsumption and excessive weight gain has been gained by analysing brains from rodents that were eating prefabricated nutritionally-complete pellets of high-fat diet (HFD). Although long-term consumption of HFDs induces chronic metabolic diseases, including obesity, they do not model several important characteristics of the modern-day human diet. For example, prefabricated HFDs ignore the (effects of) caloric consumption from a fluid source, do not appear to model the complex interplay in humans between stress and preference for palatable foods, and, importantly, lack any aspect of choice. Therefore, our laboratory uses an obesogenic free-choice high-fat high-sucrose (fc-HFHS) diet paradigm that provides rodents with the opportunity to choose from several diet components, varying in palatability, fluidity, texture, form and nutritive content. Here, we review recent advances in our understanding how the fc-HFHS diet disrupts peripheral metabolic processes and produces adaptations in brain circuitries that govern homeostatic and hedonic components of energy balance. Current insight suggests that the fc-HFHS diet has good construct and face validity to model human diet-induced chronic metabolic diseases, including obesity, because it combines the effects of food palatability and energy density with the stimulating effects of variety and choice. We also highlight how behavioural, physiological and molecular adaptations might differ from those induced by prefabricated HFDs that lack an element of choice. Finally, the advantages and disadvantages of using the fc-HFHS diet for preclinical studies are discussed.
Assuntos
Dieta Hiperlipídica , Modelos Animais de Doenças , Ingestão de Energia , Doenças Metabólicas/fisiopatologia , Obesidade/fisiopatologia , Animais , Comportamento de Escolha , Açúcares da Dieta/administração & dosagem , Metabolismo Energético , Humanos , Doenças Metabólicas/etiologia , Doenças Metabólicas/metabolismo , Obesidade/etiologia , Obesidade/metabolismo , Estresse PsicológicoRESUMO
Under normal light-dark conditions, nocturnal rodents consume most of their food during the dark period. Diets high in fat and sugar, however, may affect the day-night feeding rhythm resulting in a higher light phase intake. In vitro and in vivo studies showed that nutrients affect clock-gene expression. We therefore hypothesized that overconsuming fat and sugar alters clock-gene expression in brain structures important for feeding behavior. We determined the effects of a free-choice high-fat high-sugar (fcHFHS) diet on clock-gene expression in rat brain areas related to feeding and reward and compared them with chow-fed rats. Consuming a fcHFHS diet for 6 weeks disrupted day-night differences in Per2 mRNA expression in the nucleus accumbens (NAc) and lateral hypothalamus but not in the suprachiasmatic nucleus, habenula, and ventral tegmental area. Furthermore, short-term sugar drinking, but not fat feeding, upregulates Per2 mRNA expression in the NAc. The disruptions in day-night differences in NAc Per2 gene expression were not accompanied by altered day-night differences in the mRNA expression of peptides related to food intake. We conclude that the fcHFHS diet and acute sugar drinking affect Per2 gene expression in areas involved in food reward; however, this is not sufficient to alter the day-night pattern of food intake.
RESUMO
BACKGROUND: Elevated arginine vasopressin (AVP) plasma levels have been observed in major depression, particularly in relation to the melancholic subtype. Two hypothalamic structures produce plasma vasopressin: the supraoptic nucleus (SON) and the paraventricular nucleus (PVN). The aim of this study was to establish which structure is responsible for the increased vasopressin plasma levels in depression. METHODS: Using in situ hybridization, we determined the amount of vasopressin messenger ribonucleic acid (mRNA) in the PVN and SON in postmortem brain tissue of nine depressed subjects (six with the melancholic subtype) and eight control subjects. RESULTS: In the SON, a 60% increase of vasopressin mRNA expression was found in depressed compared with control subjects. In the melancholic subgroup, AVP mRNA expression was significantly increased in both the SON and the PVN compared with control subjects. CONCLUSIONS: We found increased AVP gene expression in the SON in depressed subjects. This might partly explain the observed increased vasopressin levels in depression.
Assuntos
Arginina Vasopressina/biossíntese , Transtorno Depressivo/metabolismo , Hipotálamo/metabolismo , RNA Mensageiro/biossíntese , Idoso , Idoso de 80 Anos ou mais , Arginina Vasopressina/genética , Feminino , Humanos , Hibridização In Situ , Masculino , Pessoa de Meia-Idade , Núcleo Hipotalâmico Paraventricular/metabolismo , Escalas de Graduação Psiquiátrica , Suicídio/psicologia , Núcleo Supraóptico/metabolismoRESUMO
Most human patients with narcolepsy have no detectable hypocretin-1 in their cerebrospinal fluid. The cause of this hypocretin deficiency is unknown, but the prevailing hypothesis states that an autoimmune-mediated mechanism is responsible. We screened for the presence of autoantibodies against neurons in the lateral hypothalamus in 76 patients and 63 controls, using immunohistochemistry. Autoantibodies were present in two patients, but also in two controls. However, one of the patients had a clearly different staining pattern and nerve endings of immunolabeled cells were found to project onto hypocretin-producing neurons, suggesting a possible pathophysiological role. Humoral immune mechanisms appear not to play a role in the pathogenesis of narcolepsy, at least not in the clinically overt stage of the disease.
Assuntos
Autoanticorpos/metabolismo , Região Hipotalâmica Lateral/patologia , Imuno-Histoquímica/métodos , Narcolepsia , Neurônios/metabolismo , Adulto , Ensaio de Imunoadsorção Enzimática/métodos , Feminino , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Masculino , Pessoa de Meia-Idade , Narcolepsia/imunologia , Narcolepsia/metabolismo , Narcolepsia/patologia , Neuropeptídeos/metabolismo , OrexinasRESUMO
A major change in thyroid setpoint regulation occurs in various clinical conditions such as critical illness and psychiatric disorders. As a first step towards identifying determinants of these setpoint changes, we have studied the distribution and expression of thyroid hormone receptor (TR) isoforms, type 2 and type 3 deiodinase (D2 and D3), and the thyroid hormone transporter monocarboxylate transporter 8 (MCT8) in the human hypothalamus and anterior pituitary. Although the post-mortem specimens used for these studies originated from patients who had died from many different pathologies, the anatomical distribution of these proteins was similar in all patients. D2 enzyme activity was detectable in the infundibular nucleus/median eminence (IFN/ME) region coinciding with local D2 immunoreactivity in glial cells. Additional D2 immunostaining was present in tanycytes lining the third ventricle. Thyrotropin-releasing hormone (TRH) containing neurons in the paraventricular nucleus (PVN) expressed MCT8, TRs as well as D3. These findings suggest that the prohormone thyroxine (T4) is taken up in hypothalamic glial cells that convert T4 into the biologically active triiodothyronine (T3) via the enzyme D2, and that T3 is subsequently transported to TRH producing neurons in the PVN. In these neurons, T3 may either bind to TRs or be metabolized into inactive iodothyronines by D3. By inference, local changes in thyroid hormone metabolism resulting from altered hypothalamic deiodinase or MCT8 expression may underlie the decrease in TRH mRNA reported earlier in the PVN of patients with critical illness and depression. In the anterior pituitary, D2 and MCT8 immunoreactivity occurred exclusively in folliculostellate (FS) cells. Both TR and D3 immunoreactivity was observed in gonadotropes and to a lesser extent in thyrotropes and other hormone producing cell types. Based upon these neuroanatomical findings, we propose a novel model for central thyroid hormone feedback in humans, with a pivotal role for hypothalamic glial cells and pituitary FS cells in processing and activation of T4. Production and action of T3 appear to occur in separate cell types of the human hypothalamus and anterior pituitary.
Assuntos
Retroalimentação Fisiológica/fisiologia , Hipotálamo/metabolismo , Transportadores de Ácidos Monocarboxílicos/biossíntese , Adeno-Hipófise/metabolismo , Receptores dos Hormônios Tireóideos/metabolismo , Hormônios Tireóideos/metabolismo , Estado Terminal , Depressão/metabolismo , Humanos , Hipotálamo/citologia , Iodeto Peroxidase/metabolismo , Modelos Biológicos , Neuroglia/metabolismo , Neurônios/metabolismo , Núcleo Hipotalâmico Paraventricular/metabolismo , Adeno-Hipófise/citologia , Receptores dos Hormônios Tireóideos/biossíntese , Simportadores , Hormônio Liberador de Tireotropina/metabolismo , Tiroxina/metabolismo , Tri-Iodotironina/metabolismo , Iodotironina Desiodinase Tipo IIRESUMO
Sleep impairment is one of the major side effects of glucocorticoid therapy. The mechanism responsible for this circadian disorder is unknown, but alterations in the suprachiasmatic nucleus (SCN), the biological clock of the human brain, are presumed to play a major role. In the present study, the amount of vasopressin mRNA (AVP mRNA) expression in the SCN was investigated in 10 glucocorticoid-exposed patients and 10 glucocorticoid free, age- and clock time of death-matched controls. The total amount of AVP mRNA, expressed as masked silver grains in the SCN, was two times lower in glucocorticoid-exposed patients (n = 10; 5115 +/- 1314 microm(2)) than that in controls (n = 10; 11,021 +/- 1408 microm(2)) (P = 0.006). There was also a 53% decrease in the total number of profiles in the SCN that expressed AVP mRNA in glucocorticoid-exposed patients (16,759 +/- 3110) compared with those in controls (31,490 +/- 3816) (P = 0.01). In conclusion, glucocorticoids have an inhibitory effect on AVP mRNA expression in the human SCN, which may be the biological basis of the circadian rhythm disturbances during glucocorticoid therapy.
Assuntos
Doenças Cardiovasculares/tratamento farmacológico , Expressão Gênica/efeitos dos fármacos , Glucocorticoides/farmacologia , Neoplasias/tratamento farmacológico , Núcleo Supraquiasmático/efeitos dos fármacos , Vasopressinas/antagonistas & inibidores , Adulto , Idoso , Autopsia , Doenças Cardiovasculares/metabolismo , Doenças Cardiovasculares/patologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Neoplasias/metabolismo , Neoplasias/patologia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Núcleo Supraquiasmático/metabolismo , Vasopressinas/genética , Vasopressinas/metabolismoRESUMO
The hypothalamus plays a fundamental role in regulating homeostatic processes including regulation of food intake. Food intake is driven in part by energy balance, which is sensed by specific brain structures through signaling molecules such as nutrients and hormones. Both circulating glucose and fatty acids decrease food intake via a central mechanism involving the hypothalamus and brain stem. Besides playing a role in signaling energy status, glucose and fatty acids serve as fuel for neurons. This review focuses on the effects of glucose and fatty acids on hypothalamic pathways involved in regulation of energy metabolism as well as on the role of the family of peroxisome proliferator activated receptors (PPARs) which are implicated in regulation of central energy homeostasis. We further discuss the effects of different hypercaloric diets on these pathways.
Assuntos
Dieta/métodos , Metabolismo Energético/fisiologia , Regulação da Expressão Gênica/fisiologia , Homeostase , Hipotálamo/metabolismo , Transdução de Sinais/fisiologia , Animais , Tronco Encefálico/metabolismo , Ingestão de Alimentos , Receptores Ativados por Proliferador de Peroxissomo/genética , Receptores Ativados por Proliferador de Peroxissomo/metabolismo , RoedoresRESUMO
CONTEXT: Narcoleptic patients with cataplexy have a general loss of hypocretin (orexin) in the lateral hypothalamus, possibly due to an autoimmune-mediated degeneration of the hypocretin neurons. In addition to excessive daytime sleepiness, Prader-Willi syndrome (PWS) patients may show narcolepsy-like symptoms, such as sleep-onset rapid eye movement sleep and cataplexy, independent of obesity-related sleep disturbances, which suggests a disorder of the hypocretin neurons. OBJECTIVE: We hypothesized that the narcolepsy-like symptoms in PWS are caused by a decline in the number of hypocretin neurons. DESIGN: We estimated the number of hypocretin neurons in postmortem hypothalami using immunocytochemistry and an image analysis system. SETTING: This study was conducted at the Netherlands Institute for Brain Research. PATIENTS: Eight PWS adults, three PWS infants, and 11 controls were studied. MAIN OUTCOME MEASURE: The total number of hypocretin neurons in the lateral hypothalamus was measured. RESULTS: There was no significant difference in the total number of hypocretin-containing neurons among the seven PWS patients (in whom sufficient hypothalamic material was available to quantify total cell number) and seven age-matched controls, either in adults or in infants. A significant decline with age was found in adult PWS patients (r = -0.9; P = 0.037). CONCLUSIONS: We conclude that a decrease in the number of hypocretin neurons does not play a major role in the occurrence of narcolepsy-like symptoms in PWS.
Assuntos
Hipotálamo/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Neuropeptídeos/metabolismo , Síndrome de Prader-Willi/metabolismo , Adulto , Idoso , Envelhecimento , Estudos de Casos e Controles , Contagem de Células , Pré-Escolar , Feminino , Humanos , Hipotálamo/patologia , Imuno-Histoquímica , Lactente , Masculino , Pessoa de Meia-Idade , Narcolepsia/complicações , Neurônios/metabolismo , Neurônios/patologia , Orexinas , Síndrome de Prader-Willi/complicaçõesRESUMO
In the present study, we describe for the first time the distribution of thyroid hormone receptor (TR) isoforms in the human postmortem hypothalamus and anterior pituitary using immunocytochemistry. We used a set of polyclonal antisera raised against the specific isoforms of the human TR. The distribution of TR alpha 1, alpha 2, beta 1, and beta 2 was studied in consecutive sections of six hypothalami and pituitaries. Staining intensity showed strong interindividual variation but was consistently present in the infundibular nucleus, paraventricular nucleus, and supraoptic nucleus. In addition, strong TR immunoreactivity was observed in the anterior pituitary. Neuropeptide Y and proopiomelanocortin mRNA-positive cells in the infundibular nucleus, which were studied in three other hypothalami, appeared not to express TRs, and thus, the neurons expressing TRs in the human mediobasal hypothalamus remain to be characterized.
Assuntos
Hipotálamo/fisiologia , Adeno-Hipófise/fisiologia , Receptores dos Hormônios Tireóideos/metabolismo , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Hipotálamo/parasitologia , Imuno-Histoquímica , Masculino , Pessoa de Meia-Idade , Especificidade de Órgãos , Adeno-Hipófise/parasitologia , Isoformas de Proteínas/análiseRESUMO
CONTEXT: Recent findings point to an increasing number of hypothalamic proteins involved in the central regulation of thyroid hormone feedback. The functional neuroanatomy of these proteins in the human hypothalamus is largely unknown at present. OBJECTIVE: The aim of this study was to report the distribution of type II and type III deiodinase (D2 and D3) as well as the recently identified T(3) transporter, monocarboxylate transporter 8 (MCT8), in the human hypothalamus. DESIGN: The study included enzyme activity assays, immunocytochemical studies, and mRNA in situ hybridizations in postmortem human hypothalamus (n = 9). RESULTS: D2 immunoreactivity is prominent in glial cells of the infundibular nucleus/median eminence, blood vessels, and cells lining the third ventricle. By contrast, both D3 and MCT8 are expressed by neurons of the paraventricular (PVN), supraoptic, and infundibular nucleus (IFN). In support of these immunocytochemical data, D2 and D3 enzyme activities are detectable in the mediobasal human hypothalamus. Combined D2, D3, MCT8, and thyroid hormone receptor immunohistochemistry and TRH mRNA in situ hybridization clearly showed that D3, MCT8, and thyroid hormone receptor isoforms are all expressed in TRH neurons of the PVN, whereas D2 is not. CONCLUSIONS AND IMPLICATIONS: Based on these findings, we propose three possible routes for thyroid hormone feedback on TRH neurons in the human PVN: 1) local thyroid hormone uptake from the vascular compartment within the PVN, 2) thyroid hormone uptake from the cerebrospinal fluid in the third ventricle followed by transport to TRH neurons in the PVN or IFN neurons projecting to TRH neurons in the PVN, and 3) thyroid hormone sensing in the IFN of the mediobasal hypothalamus by neurons projecting to TRH neurons in the PVN.