Association of hypotalamic POMC, NPY and IRS2 with feeding behavior in norma and overweight Wistar rats / Associação do PMOC, NPY e IRS2 hipotalâmicos com padrões de comportamento alimentar em ratos wistar normais e sobrepeso

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

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 natural 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 extremely 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 model of Plagemann (1999) animals with 25% of overweight in relation to the control animals were obtained, hyperphagics, and with different size patterns and meal circadian rhythm. In spite of the high hormonal levels of leptin (>100%, p <0,001) and insulin (>90%, p <0,05) in relation to the control groups, these animals presented low expression in the hunger state, and high expression in the satiation of hypothalamic NPY, suggesting that POMC would be more committed, in the long term, with the regulation of the feeding rhythm. The hyperinsulinemia and plasmatic hyperleptinemia associated to the reduced POMC and IRS2 expression in the ARC, corroborated this conclusion. We also demonstrated different feeding patterns. The feeding registration method, based on the gnaw sound was validated as excellent, when comparedto a gold pattern, the registrations obtained in the videos, and it were considered efficient. When the hunger-satiation states were discriminated in the control and overweight groups, the results of the hypothalamic neuroreceptors expression studied showed association to the feeding patterns.

ASSUNTO(S)

neuropeptide y neurofisiologia hiperfagia metabolic programming hypothalamus obesity hyperphagia insulin-receptor substratum 2 neuropeptídeo y pró-ópiomelanocortina feeding behavior comportamento alimentar obesidade circadian rhythm hipotálamo receptor de insulina substrato 2 ritmo circadiano pro-ópiomelanocortin programação metabólica

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