A team of scientists at The Scripps Research Institute (TSRI) has identified a brain hormone that appears to trigger fat burning in the human gut.

The researchers studied roundworms since their brain produces similar signaling molecules as humans. They discovered a hormone called "FLP-7," which is secreted by neurons to trigger fat burning in response to high levels of a gut regulating neurotransmitter called "serotonin."

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Supriya Srinivasan, an assistant professor at the institute and a senior author of the study, said that this was basic science that unlocked an interesting mystery.

Studies have shown in the past that the neurotransmitter serotonin can drive fat loss but no one was sure exactly how. To answer the question, Srinivasan and her colleagues experimented with roundworms called C. elegans, which are often used as model organisms in biology. The researchers deleted genes from the roundworms to see if they could interrupt the path between brain serotonin and fat burning. The process of elimination involved testing one gene after another in a hope to find the gene without which fat burning. They finally found a gene that codes for a neuropeptide hormone which they named FLP-7 (pronounced "flip 7").

Interestingly, in the study published in the journal Nature Communications, they found that the mammalian version of FLP-7 (called Tachykinin) had been identified 80 years ago as a peptide that triggered muscle contractions when dribbled on pig intestines.

The next step was to determine if FLP-7 was directly linked to serotonin levels in the brain.

Lavinia Palamiuc, a TSRI research associate and first author of the study, spearheaded this effort by tagging FLP-7 with a fluorescent red protein to make it visible in living animals, possible because the roundworm body is transparent. Her effort revealed that FLP-7 was indeed secreted from neurons in the brain in response to elevated serotonin levels. It then traveled through the circulatory system to start the fat burning process in the gut.

This study was supported by the National Institutes of Health's National Institute of Diabetes and Digestive and Kidney Diseases and the NIH Office of Research Infrastructure Programs.