Leptin and Alzheimer's Disease

It is well documented that the hormone leptin regulates several hypothalamic-driven functions, including energy homeostasis and reproductive function. However, recent studies indicate that leptin receptor expression is not restricted to hypothalamic sites and that leptin has widespread action in the central nervous system (CNS). Indeed, evidence is growing that leptin has the capacity to modulate higher brain functions, including its ability to markedly influence hippocampal synaptic function and in particular learning and memory processes. It is known that diet and lifestyle are key factors influencing the risk of developing neurodegenerative disorders, and recent evidence has found a link for midlife obesity and Alzheimer's disease (AD). As obesity is attributed to leptin resistance, the hormone leptin may be an important factor linking obesity and AD. Indeed, recent studies indicate that dysfunctions in the leptin system are associated with an increased incidence of AD. Here we review the evidence that leptin is a potential cognitive enhancer and also examine the possibility of utilizing leptin replacement therapy in the treatment of AD.