Regulating Energy Balance: The Substrate Strikes Back.

BIOENERGETICS; HORMONES; APPETITE; LEPTIN; FATTY acids; LEUCINE; RAPAMYCIN; REGULATION of cell growth; HYPOTHALAMUS

The article reports on the regulation of energy balance in the body. Hormones and dietary nutrients control appetite and metabolism by acting on the brain. The signals which these hormones generate promote hunger or satiety. Neurons in the hypothalamus integrate these signals to maintain energy balance. Hormones, such as the fat-derived hormone leptin influence directly a subset of neurons. Free fatty acids also act on targets in the central nervous system to regulate metabolism. Leucine, a building block for proteins, also regulates the neural circuits that control appetite and energy balance through the mammalian Target of Rapamycin pathway. Rapamycin pathway (mTOR). mTOR is a serine-threonine kinase. Overexpression of mTOR results in aberrant cell growth. Reducing AMP-activated protein kinase activity may increase mTOR activity. Concentrations of extracellular amino acids in the hypothalamus are influenced by dietary composition. The regulation of mTOR by insulin is mediated by the phosphatidylinositol 3-kinase pathway.