New technique may help measure how full or hungry you are

November 14th, 2007 - 10:15 am ICT by admin  
The study, by Professor Jimmy Bell, corresponding author of the study from the MRC Clinical Sciences Centre at Imperial College London and his team, was conducted on a mouse model using a technique they developed.

As a part of the technique, the researchers used imaging to reveal how neurons behave in the part of the brain, which regulates appetite.

Satiety, which is the psychological feeling of being full and satisfied rather than physical fullness had been previously very difficult to measure.

In the new study, the researchers discovered that they could see the neurons firing in the hypothalamus area of the brain, which regulates appetite, if they used a contrast agent of manganese ion to make the neurons visible on a magnetic resonance imaging scan.

However, when the mouse was hungry, the neurons showed increased activity, the contrast agent was taken up, making the neurons ‘light up’ on the scan.

The intensity of the signal decreased as the mouse became less hungry and the neurons became less active.

In the study, the team used different contrast agents to look at the anatomy of different cells in the body.

Mice given the contrast agent were also given one of two types of hormone. These were either pancreatic peptide YY (PYY), which is known to inhibit appetite, or ghrelin, which is known to increase it.

The scientists then monitored the reactions of the ‘hunger’ neurons to these stimuli.

Expectedly, the intensity of the neurons’ signals increased when ghrelin was administered and decreased with PYY.

The new study is the first to identify which contrast agent is taken up by the ‘hunger’ neurons and hence allowed the researchers to observe how they behaved in response to different stimuli.

“Appetite and appetite control are important components of why people put on weight. We know very little about the mechanisms behind these processes and why they can vary so much between individuals.

” In the past we have had to rely on asking people how hungry they feel, this can be very subjective. Furthermore, sometimes your sense of satiety can be significantly affected by other factors such as your mood.

“Our new method is much more reliable and completely objective. With murine models, we can now look directly at neuronal activity in the brain. We are working on developing similar methods to study neuronal activity in the appetite centres in people,” Bell said.

The team hopes that the technique would enable a far greater understanding of why certain people become obese when others do not, and why different people have different appetites.

The study is published in the Journal of Neuroscience. (ANI)

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