Interaction of olfaction and feeding behavior and its neural mechanism / 生理学报

Olfaction and food intake are interrelated and regulated. In the process of feeding, the metabolic signals in the body and the feeding signals produced by food stimulation are first sensed by the arcuate nucleus of hypothalamus and the nucleus tractus solitarius of brain stem, and then these neurons project to the paraventricular nucleus of hypothalamus. The paraventricular nucleus transmits the signals to other brain regions related to feeding and regulates feeding behavior. In this process, olfactory signals can be transmitted to hypothalamus through olfactory bulb and olfactory cortex to regulate feeding behavior. At the same time, gastrointestinal hormones (ghrelin, insulin, leptin, etc.) and some neurotransmitters (acetylcholine, norepinephrine, serotonin, endocannabinoid, etc.) produced in the process of feeding act on the olfactory system to regulate olfactory function, which in turn affects the feeding itself. This review summaries the research progress of the interaction between olfaction and food intake and its internal mechanism from the aspects of neuronal and hormonal regulation.

Associação de POMC, NPY e IRS2 hipotalâmicos com padrões de comportamento alimentar em ratos Wistar normais e sobrepeso / Association of POMC, NPY and hypothalamic IRS2 with patterns of eating behavior in overweight and normal Wistar rats

O comportamento alimentar de uma espécie é determinado por um conjunto de características filogenéticas, ontogenéticas, e epigenéticas, e regulado por fatores internos e externos ao organismo. Os fenômenos naturais que regem a vida no nosso planeta são periódicos em sua maioria, e a oferta de alimentos não é exceção. Cada safra é seguida de uma entressafra, e este ritmo sincroniza diversos outros ritmos, exógenos e endógenos, capazes de determinar a sobrevivência de espécies. Uma das estratégias adaptativas mais primitivas e bem sucedidas na dinâmica oscilatória da natureza, é o acúmulo de reservas. Nossa espécie, nos últimos 50 anos, vive uma situação de grande oferta de alimentos, período este extremamente pequeno, se visto sob a ordem de grandeza da evolução humana. Este fenômeno tem sido determinante na prevalência do depósito de energia e em decorrência, do surgimento da obesidade e suas consequentes patologias. O hipotálamo está intimamente associado à homeostase energética e ao comportamento alimentar. No núcleo arqueado hipotalâmico encontram-se populações neuronais orexigênicas e anorexigênicas, dentre as quais, as que expressam os neuroreceptores POMC, NPY e o substrato de receptor de insulina IRS2. A modificação da expressão destas proteínas tem sido associada à alterações do comportamento alimentar, bem como à impressão e programação metabólica, capazes de induzir obesidade em ratos adultos. A correlação desta circuitaria neuronal com o comportamento alimentar, porém, ainda não está suficientemente compreendida. A detecção do estado de fome-saciedade nos ratos, fundamental no estudo da neurofisiologia relacionada ao comportamento alimentar, vem sendo obtida via de regra, por meio de procedimentos complexos de observação comportamental. O presente estudo contribui para o conhecimento de padrões de alimentação determinados por condições nutricionais, e sua relação com a expressão neurofisiológica hipotalâmica dos neurônios POMC, NPY e IRS2 ...

The feeding behavior of a specie is determined by a group of phylogenetic, ontogenetic, and epigenetic features, and regulated by internal and external factors to the organism. The natura phenomena that govern life in our planet are mainly periodic, and the food stocks is not an exception. Each harvest is followed by a time between harvests, and this rhythm synchronizes other several exogenous and endogenous rhythms, capable of determining the survival of species. One of the most primitive strategies of adaptative evolution of species, and what usually happens regarding the oscillatory dynamics of nature, is the reserve accumulation. Our species, in the last 50 years, has been living a situation of great food offer, such period is exremely small if analysed under the greatness order of the human evolution. This phenomenon has been decisive in the prevalence of the energy deposit and, in consequence, determining the appearance of obesity and its consequent pathologies. The hypothalamus is intimately associated to the energy homeostasis and the feeding behavior. In the arcuate nucleous are orexigenic and anorexigenic neuronal populations, that express the neuroreceptors POMC, NPY and insulin receptor substratum IRS2. The modification of these proteins expression, has been associated to alterations of the feeding behavior, as well as to the metabolic imprinting and programming, capable to induce obesity in adult rats. The correlation of this neuronal circuits with the alimentary behavior, however, it is not yet sufficiently understood. The detection of the hunger-satiation state in the rat, crucial in the neurophysiology studies related to the alimentary behavior, has been obtained through complex procedures of behavioral observation. The present study contributed to the knowledge of certain feeding patterns for nutritional conditions, and its relationship with the neurophysiological expression of POMC, NPY and IRS2 neurons. Using the metabolic programming ...

Programação do processo fome-saciedade de animais desnutridos no início da lactação: papel do NPY/AgRP e POMC / Programming hunger-satiety process of malnourished animals in early lactation: role of NPY/AgRP and POMC

A modulação do processo fome-saciedade é um fator determinante para o crescimento normal dos sistemas metabólicos. Tem sido demonstrado que variações nutricionais nos períodos pré e pós-natal induzem modificações nas projeções e/ou contatos dos circuitos neuronais hipotalâmicos, gerando uma "reprogramação" deste sistema que envolve mecanismos de interação da ação primária de hormônios como leptina em neurônios orexigênico (NPY/AgRP) anorexigênicos (POMC) no núcleo arqueado, para regular o comportamento alimentar. O objetivo deste trabalho foi estudar a programação do processo fome-saciedade no núcleo arqueado hipotalâmico, em curto e longo prazos, em animais que foram desnutridos no início da lactação. Para isso, utilizamos ratos Wister desnutridos nos primeiros 10 dias de lactação com a utilização de dieta materna com 0% de proteína e que foram submetidos a novo período de desnutrição protéica na fase adulta (60 dias de idade) por 3 dias. Para o estudo do processo fome-saciedade, as variáveis avaliadas foram peso corporal, razão peso corporal / consumo alimentar, conteúdos de receptores de leptina (Ob-Rb) e de neuropeptídeos hipotalâmicos (NPY/AgRP e POMC). Observamos que ao final de 10 dias de desnutrição na lactação, os animais desnutridos apresentaram menor peso corporal (FD - fêmea desnutrida, 50% e MD - macho desnutrido, 53%) e aumento dos conteúdos de Ob-Rb (FD: 121,67% e MD: 132,73%), NPY/AgRP (FD: 32,31% e MD: 115,62%) e POMC (FD: 71,2% e MD: 26,58%). Aos 60 dias de vida, os animais desnutridos apresentaram maior razão peso corporal / consumo alimentar e não evidenciamos diferença nos conteúdos de Ob-Rb, NPY/AgRP e POMC (p<-0,05). Aos 63 dias de vida, fêmeas (FDD) e machos desnutridos (MDD), após um segundo episódio de desnutrição, apresentaram redução de peso corporal (FDD: 12,4% e MDD: 10,75%) e consumo alimentar (FDD: 57,5% e MDD: 39,88%). O conteúdo dos neuropeptídeos orexigênicos (NPY/AgRP)...

The modulation of the hunger-satiety process is a determining factor for the normal growth of the metabolic systems. It has been demonstrated that nutritional variations during pre- and postnatal lead to modifications in projetions and/or contacts of hypothalamic neuronal circuits generating a "reprogramation" of this system, which involves mechanisms of interation of primary action of hormone as leptin in NPY/AgRP and POMC neurons in the arcuate nucleus, to regulate eating behavior. Our aim was to study the programation in the hunger-satiety process in the arcuate nucleus, in the short and long terms, in animals that were malnourished during the early lactation period. In the present study we used Wistar rats that were malnourished during the first 10 days of lactation (0% protein maternal diet) and that were submitted to new a period of malnutrition at adulthood (60 days-old) for 3 days. To study the hunger-satiety process, the variables evaluated were: body weight, body weight/food intake ratio, hypothalamic content of the leptin receptor (Ob-Rb) and the orexigenic NPY/AgRP and anorexigenic POMC neuropeptides. We observed at the end of 10 days of malnutrition during lactation, that the malnourished animals had lower body weight (MF - malnourished female, 50% and MM - malnourished male, 53%) and higher content of Ob-Rb (MF: 121,67% and MM: 132,73%), NPY/AgRP (MF: 32,31% e MM: 115,62%) and POMC (MF: 71,2% e MM: 26,58%). At 60 days, the malnourished animals had higher body weight/food intake ratio and showed no change in the Ob-Rb, NPY/AgRP and POMC content (p<-0,05). At 63 days of life, malnourished female and male after a second episode of malnutrition, had lower body weight (MMF: 12,4% and MMM: 10,75%) and food intake (MMF: 57,5% and MMM: 39,88%). The content of neuropeptides (NPY/AgRP) was significantly lower (MMF: 22,6% and MMM: 26,58%), while the content of Ob-Rb (MMF: 92,27% and MMM: 28%) and POMC neuropeptide (MMF: 22,34% and MMM:27,27%)...

Changes in orexin-A and neuropeptide Y expression in the hypothalamus of the fasted and high-fat diet fed rats

This study was aimed to investigate the changes of orexin-A (OXA) and neuropeptide Y (NPY) expression in the hypothalamus of the fasted and high-fat diet fed rats. For the experiments, the male Sprague-Dawley (SD) rats were used as the model of high-fat diet-induced obesity. The mean loss of body weight (MLBW) did not show the linear pattern during the fasting; from 24 h to 84 h of fastings, the MLBW was not significantly changed. The numbers of OXA-immunoreactive (IR) neurons were decreased at 84 h of fasting compared with those in other five fasting subgroups. The NPY immunoreactivities in the arcuate nucleus (ARC) and the suprachiasmatic nucleus (SCN) observed at 84 h of fasting were higher than that observed at 24 h of fasting. The number of OXA-IR neurons of the LHA (lateral hypothalamic area) in the high-fat (HF) diet fed group was more increased than that of the same area in the normal-fat (NF) diet fed group. The NPY immunoreactivities of the ARC and the SCN were higher in HF group than those observed in the same areas of NF group. Based on these results, it is noteworthy that the decrease of the body weight during the fast was not proportionate to the time-course, implicating a possible adaptation of the body for survival against starvation. The HF diet might activate the OXA and the NPY in the LHA to enhance food intake.