Insulin in the midbrain influences eating behaviour

Still hungry - or already full? The brain controls eating behaviour and curbs our appetite when the body has consumed enough energy. It obtains its information about the degree of satiety from various messenger substances, of which insulin plays an important role.

Scientists at the Max Planck Institute for Neurological Research and the Cluster of Excellence in Cellular Stress Responses in Aging-associated Diseases (CECAD) at the University of Cologne have now discovered that in mice, insulin not only acts as a metabolic signal transmitter in the hypothalamus, a fact that is already known, but also in the dopamine-producing cells of the midbrain.

The switching off of the insulin receptors in these neurons causes gluttony and overweight.

The hormone insulin, which is produced in the pancreas, plays a key role in the regulation of blood sugar levels. Malfunctions of this system can result in overweight and diabetes mellitus. Researchers have already known for some years that this regulation of the body's energy balance is not limited to muscle and fat tissue.

The research team working with Jens Brüning, Director of the Max Planck Institute for Neurological Research and scientific coordinator of the Cluster of Excellence in Cellular Stress Responses in Aging-associated Diseases (CECAD) at the University of Cologne, succeeded in demonstrating that insulin receptors are found in certain cells of the hypothalamus – an important 'command centre' in the midbrain. Insulin thus passes the blood-brain barrier, binds to nerve cells and gives the signal for satiety.

If these receptors are not available, the brain lacks the crucial information that enables it to set the course for satiety: more food is consumed, the result of which is weight gain.