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Rôle de l'acide polysialique (PSA) dans le contrôle hypothalamique de la prise alimentaire et du poids corporel

Abstract : Hypothalamus plays a major role in the regulation of energy homeostasis by the presence of neural circuits controlling food intake. These circuits are plastic and can be rewired during adulthood. We hypothesized that synaptic plasticity can occur during physiological conditions. We have shown that synaptic contact on hypothalamic anorexigen POMC neurons are rewired in mouse upon high fat diet (HFD). This synaptic process is mandatory to adjust energy intake and requires the glycan PSA (polysialic acid). PSA promotes synaptic plasticity in the brain by the weakening of cell-to-cell interaction by addition on NCAM (neural cell adhesion molecule). We hypothesized that a defect in brain synaptic plasticity capacity could be a risk factor in the etiology of metabolic diseases. We show that homeostatic feeding response to HFD ingestion was predictive to weight gain observed three months after HFD introduction. The feeding response to HFD was correlated with the hypothalamus PSA level. We show that chronic depletion of hypothalamic PSA accelerate the onset of diet induced obesity. These results indicate that a low hypothalamic PSA level prone to diet induced obesity. In parallel, we focus on the hypothalamic regulation of circulating cholesterol. Melanocortin system control level of circulating cholesterol. Using our model of diet induced synaptic plasticity; we show that there is a link between hypothalamic PSA and circulating cholesterol. A long term reduction of hypothalamic PSA level, lead to an accumulation of fat deposit in blood vessels. This whole work allows us to underscore the role of diet induced synaptic plasticity in the regulation of energy homeostasis.
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Xavier Brenachot. Rôle de l'acide polysialique (PSA) dans le contrôle hypothalamique de la prise alimentaire et du poids corporel. Neurosciences [q-bio.NC]. Université de Bourgogne, 2013. Français. ⟨NNT : 2013DIJOS096⟩. ⟨tel-01698812⟩

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