Question

Which proprieties of leptin allow it to cross the blood-brain barrier? How does leptin regulate energy balance?

Answer 1

Answer:

Leptin being a large protein is too big to cross the Blood-Brain Barrier via simple diffusion or facilitated diffusion. It requires a unique protein that helps in facilitating the transport of leptin across the Blood-Brain Barrier (BBB). From fat cells, it gets released into the blood where it binds with specific receptors present in the central nervous system and it crosses the BBB.

Regulation of Energy:

Leptin works on a negative feedback mechanism and acts in the brain. In the case of an increased level of leptin, it constrains the fat mass, limits the intake of energy, and promotes the expenditure of energy. When there is a signal reflecting decreasing leptin level, it signals the brain to increase the intake of food and increase the fat accumulation.