Hunger hormone can cross the blood-brain barrier, impact brain: Study

A study on mice has shown how gut-produced hunger hormones can influence decision-making and drive an animal's behaviour.

The researchers said that the findings demonstrate how the hunger hormone can cross the blood-brain barrier and directly impact the brain to drive activity, controlling a circuit in the brain that is likely to be the same or similar in humans.

The blood-brain barrier is known to strictly restrict many substances in the blood from reaching the brain. The study findings are published in the journal, Neuron

Researchers put mice in an arena that had some food, and looked at how the mice acted when they were hungry or full.

While all the mice spent time investigating the food, only the hungry ones would begin eating, the researchers at University College London, UK, found.

They also used brain imaging to study activity in the mice's ventral hippocampus, which is a decision-making part of the brain understood to help form and use memories to guide behaviour.

The researchers found that activity in a subset of brain cells in the ventral hippocampus increased when the mice approached the food and that this neural activity inhibited them from eating.

However, when the mice were hungry, less neural activity in this brain region was observed and therefore, they were not inhibited from eating.

The researchers also found that this corresponded to high levels of the hunger hormone ghrelin circulating in the blood.

Further, by activating these ventral hippocampal neurons, the researchers were able to experimentally make mice behave as if they were full and therefore stopped eating.

Researchers also said that the findings could contribute to research into the mechanisms of eating disorders, along with other links between diet and other health outcomes such as risk of mental illnesses.

The scientists said they are continuing their research by investigating whether hunger can impact learning or memory by checking if mice perform non-food-specific tasks differently depending on how hungry they are.

They also said additional research might also shed light on whether there are similar mechanisms at play for stress or thirst.