Neurotransmitter serotonin shown to trigger fat burning

The neurotransmitter serotonin has been shown to play a central role in regulating appetite (amongst other things),  but the reasons for this had eluded scientists.

In an attempt to shed light on the subject, biologists at The Scripps Research Institute (TSRI) conducted experiments on C elegans roundworms and identified a brain hormone that selectively triggered fat burning in the gut, regardless of food intake.

According to scientists, the findings could have implications for humans.

TSRI assistant professor Supriya Srinivasan, senior author of the new study, and her colleagues made the discovery through a process of elimination, starting with C Elegans roundworms, commonly used model organisms in biology because their brains produce many of the same signaling molecules as humans.

They went on to systematically delete one gene after another in the roundworm in an attempt to identify which gene was responsible for fat burning.

They found that the gene that coded for a neuropeptide hormone dubbed FLP-7, the mammalian version of which is called Tachykinin was responsible for fat burning. The gene had been identified 80 years ago for triggering muscle contractions when dribbled on pig intestines.  Scientists at the time believed the hormone connected the brain to the gut, since the link between Tachykinin and fat metabolism had not been identified.

The next step in the new study was to determine whether there existed a direct link between FLP-7 serotonin levels in the brain.

Lavinia Palamiuc, a TSRI research associate, tagged FLP-7 with a fluorescent red protein so that it could be seen in C elegans, due to the transparent body of the roundworm.

She showed that elevated serotonin levels triggered the secretion of FLP-7 from neurons in the brain, which then travelled through the circulatory system to start the fat burning process in the gut.

''That was a big moment for us,'' said Srinivasan, PTI reported. The research for the first time demonstrated that a brain hormone specifically and selectively stimulated fat metabolism, without any effect on food intake.