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Thyroid Hormone Action on the Energy Balance in the Brain

http://www.bulletins-electroniques.com/actualites/62530.htm

Expressed in the brain, the gene Mc4r integrating information on the amount of fat stored in peripheral tissues is a key relay in the production of leptin that regulates the appetite by controlling the feeling of satiety, hence its name 'the satiety hormone'. It also regulates the fat stores in the body. Mutations of the gene are known for causing severe obesity in humans, as the activation of its expression reduces food intake and increases energy expenditure.

Barbara Demeneix and her fellow researchers at the Evolution of Endocrine Regulations Joint Research Unit (National Museum of Natural History-CNRS) have shown that the expression of the Mc4r gene is repressed by a signal from the endocrine system, the thyroid hormone that orchestrates energy burn-up in the body. For this purpose, they studied several gene expression zones in the brain, which affect the metabolism and food intake: the paraventricular nucleus, the arcuate nucleus and the brain stem. Actually, the thyroid hormones repress the Mc4r gene in each site.

Published in the early edition (February 25 update, online) of the Proceedings of the National Academy of Sciences (PNAS), research results show that the Mc4r gene in the brain directly connects the information on the state of body energy reserves (leptin) with the information regulating energy expenditure (thyroid hormone). So, the brain has a fine-tuned means of adjusting energy burn-up to energy supply: the negative signals of the thyroid hormone on the expression of gene Mc4r. In a world situation where obesity is on the rise and where one out of eight women suffer thyroid dysregulation, the researchers results are a major breakthrough for human health.

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National Museum of Natural History (Muséum National d'Histoire Naturelle) - Regulation, Development and Molecular Diversity Department (Département Régulation, Développement et Diversité Moléculaire ) - Laboratory of Endocrine Regulation Evolution (Laboratoire d'Evolution des Régulations Endocriniennes )- Barbara Demeneix - email: demeneix@mnhn.fr

Code brève
ADIT : 62530

ADIT - Jean-François Desessard - email: jfd@adit.fr

eTech France numéro 238 (8/03/2010) - ADIT / ADIT - http://www.bulletins-electroniques.com/actualites/62530.htm