3 The Lighter Side of BDNF 4 5

24 Brain-derived neurotrophic factor (BDNF) mediates energy metabolism and 25 feeding behavior. As a neurotrophin, BDNF promotes neuronal differentiation, 26 survival during early development, adult neurogenesis and neural plasticity; thus 27 there is the potential that BDNF could modify circuits important to eating behavior 28 and energy expenditure. The possibility that " faulty " circuits could be remodeled by 29 BDNF is an exciting concept for new therapies for obesity and eating disorders. In 30 the hypothalamus, BDNF and its receptor, tropomyosin-related kinase B (trkB), are 31 extensively expressed in areas associated with feeding and metabolism. 32 Hypothalamic BDNF and trkB appear to inhibit food intake and increase energy 33 expenditure leading to negative energy balance. In the hippocampus, the 34 involvement of BDNF in neural plasticity and neurogenesis is important to learning 35 and memory, but less is known about how BDNF participates in energy homeostasis. 36 We review current research about BDNF in specific brain locations related to energy 37 balance, environmental and behavioral influences on BDNF expression and the 38 possibility that BDNF may influence energy homeostasis via its role in neurogenesis 39 and neural plasticity.