Ghrelin: All About the Hunger Hormone

Discovered in 1999, ghrelin plays a key role in the appetite.

Peptide of gastric origin, ghrelin stimulates the secretion of growth hormone and increases adiposity (accumulation of fat in the subcutaneous cellular tissue).

According to new research, this intestinal hormone increases the response to food and promotes conditioning to food-related odors.

The results of the study are published in Cell Reports, December 4, 2018.

GHRELIN MAKES US MORE VULNERABLE TO STIMULI THAT CAUSES HUNGER

Whatever the season, it is difficult to monitor your weight if you are sensitive to some yoyo effect, even more during the holiday season, with the images and smells of food that it is sometimes hard to resist.

A factor in this response to hunger is a hormone found in the stomach. It makes us more vulnerable to smells of tasty food, encouraging overeating and obesity.

Previous research has shown that ghrelin encourages the feeding and production of dopamine, an important neurotransmitter for reward response.

In this study, the researchers injected 38 subjects with ghrelin and exposed them to various odors, both food and non-food, while showing them neutral images of random objects, so that subjects associated with odors.

GHRELIN IMPROVES CONDITIONING OF FOOD ODORS

Using functional magnetic resonance imaging (fMRI), the researchers recorded activity in brain regions involved in the response to the dopamine reward.

They found that activity in these areas was higher in subjects who received a ghrelin injection, but only in response to images associated with food odors.

This means that ghrelin can "control" the brain that associates a reward with food odors.

Subjects also assessed the quality of images associated with food odor, and the results showed that ghrelin reduced response time and increased the perceived quality of images associated with food, but had no effect on their response to foods. images associated with non-food odors.

People suffering from obesity often have an abnormal reactivity to the food signals that abound in our environment, for example in the face of advertising fast food or prepared dishes, and the ton of TV shows on culinary themes.

Finally, this study shows that ghrelin can be a major factor in their increased response to food signals.

The regions of the brain identified have been linked to a neural endophenotype that confers vulnerability to obesity, suggesting a genetic-induced hypersensitivity to images and odors associated with food.

"Obesity is becoming more common around the world and causes health problems such as heart disease and diabetes. This study describes the mechanism by which ghrelin makes people more vulnerable to hunger stimuli, and the more knowledge we have, the easier it will be to develop treatments that counteract this effect, "the authors conclude.

SOURCES

"Ghrelin Enhances Food Odor Conditioning in Healthy Humans: An fMRI Study. Cell Reports, 2018; 25 (10): 2643 DOI: 10.1016 / j.celrep.2018.11.026