Scientists Discover Brain Hormone That Triggers Fat Burning

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Researchers at The Scripps Research Institute (TSRI) have found a brain hormone that triggers fat burning in the gut. They believe that their findings in animal models could have implications for future pharmaceutical development.

"This was basic science that unlocked an interesting mystery," senior author and TSRI Assistant Professor, Supriya Srinivasan said.  Previous studies on the topic have revealed that the neurotransmitter serotonin can lead to fat loss, but it was not clear how. These findings motivated the researchers at TSRI to conduct the current study so as to determine how the neurotransmitter serotonin aids fat loss.

The researchers conducted a study on a species of roundworm known as C. Elegans. The worms are usually used as model organisms in biology as they have simpler metabolic systems than humans, but their brains produce many similar signaling molecules, thus, prompting the authors to conclude that findings in C. Elegans may also be relevant for humans.

During their experiment, the researchers erased genes in C. Elegans to check whether they could interrupt the path between brain serotonin and fat burning. They tested all the genes in search of one without which fat burning would not occur with the process of elimination leading the authors to a gene that codes for a neuropeptide hormone named FLP-7, according to Science Daily.

However, they discovered that the human version of FLP-7 known as Tachykinin had been identified 80 years ago as a peptide that triggered muscle contractions when dribbled on pig intestines. The researchers during that time believed that it was a hormone that connects the brain to the gut, but no one had linked the neuropeptide to fat metabolism.

The researchers in the current study took steps to check whether FLP-7 was directly linked to serotonin levels in the brain by tagging FLP-7 with a fluorescent red protein so that it could be visualized in living animals, possibly because the body of the roundworm is transparent.

They discovered that FLP-7 was indeed secreted from neurons in the brain in response to elevated serotonin levels and then it travels through the circulatory system to start the fat burning process in the gut. Researchers, for the first time, have found a brain hormone that specifically stimulates fat metabolism, without any negative effect on food intake.

The newly found fat-burning hormone works by a neural circuit in the brain producing serotonin in response to sensory cues like food availability, which then signals another set of neurons to begin producing FLP-7. The FLP-7 activates a receptor in intestinal cells which triggers the process of transforming fat into energy in the intestines, according to Medical Express.

The study authors investigated into the consequences of manipulating FLP-7 levels and found that although, increasing serotonin can have a wide range of effect on animals' food intake, movement, and reproductive behavior, increasing the level of FLP-7 farther downstream is not accompanied by any obvious side effects.

The worms continued to function and carry out their routines normally while they burned fat. The researchers believe that their findings could encourage future studies on how the levels of FLP-7 could be regulated without causing the usual side effects that follow the manipulation of overall serotonin levels. They published their findings in the journal Nature Communications.