A team of biologists at the Scripps Research Institute in the United States has identified a brain hormone that tells the body to burn fat in the intestine.
According to Supriya Srinivasan , one of the researchers in the study, although it was already known that the neurotransmitter serotonin could lead to fat loss, it was not known exactly how.
To answer this question, the team did some experiments with C. elegans worms, often used in this type of research since their brains produce many of the same signaling molecules as those of humans.
The scientists removed the genes from these worms to see if they could stop the process between brain serotonin and fat loss. When testing one gene after another, they hoped to find the gene without which fat loss would not occur.
This elimination process led to a gene encoding a neuropeptide called FLP-7 . The study was published in the journal Nature Communications.
On the right path
Curiously, scientists found that the mammalian version of FLP-7 was identified 80 years ago as a peptide that triggered muscle contractions in pig intestines.
At the time, the researchers thought it was a hormone that linked the brain to the gut, but no one realized that this neuropeptide also linked to the metabolism of fat .
The next step of the new research was to determine whether this FLP-7 was directly linked to serotonin levels in the brain.
The lead author of the study, Lavinia Palamiuc , led this effort by marking the FLP-7 with a red fluorescent protein so it could be visualized in the transparent worms.
Researchers have discovered how the whole process works: a neural circuitry in the brain produces serotonin in response to sensory cues, such as food availability. This signals another set of neurons to begin producing FLP-7, released in the brain in response to high levels of serotonin .
Then FLP-7 travels through the circulatory system and activates a receptor in the intestinal cells, so that the intestines begin to turn fat into energy.
Fat loss without side effects
The brain hormone specifically and selectively stimulates fat metabolism without any effect on food intake. Therefore, the researchers decided to test the consequences of manipulating FLP-7 levels.
Although increased serotonin may have a major impact on food intake, movement and reproductive behavior of an animal, the team found that increasing FLP-7 levels did not have any obvious side effects – worms continued to function normally while simply burning more fat.
This finding should encourage further research on how FLP-7 levels can be regulated without causing side effects in humans.