Role of Type 2 Deiodinase in Hy- pothalamic Control of Feeding Behavior

The amount of energy in the body is highly regulated. The hypothalamus is a key neural structure involved in this process, keeping the intake of food in step with the energy expenditure. The main hypothalamic nuclei involved in energetic metabolism regulation are the arcuate, periventricular, dorsomedial and ventromedial that integrates several peripheral signals, such as leptin and adiponectin. Although is well known that T3 regulates basal metabolism, it also has an important role in feeding behavior regulation since it stimulates neurons that express orexigenic neuropeptides, such as AgRP and NPY found in the arcuate hypothalamic nuclei. The amount of T3 available in the brain depends on the activity of the type 2 deiodinase (D2) that transforms T4 in T3. D2 is expressed in glial cells that are in close contact with the AgRP/NPY expressing neurons in the arcuate hypothalamic nuclei, suggesting that D2 has an important role in the regulation of the feeding behavior and in the body weight.