FIT Is The Reason Proteins Make (Female) Flies Full

Consuming proteins triggers the release of FIT, which signals fullness to the brain and prevents the consumption of more proteins.

AsianScientist (Feb. 17, 2017) – Researchers at the Institute of Biophysics of the Chinese Academy of Sciences have identified a gene that makes flies feel full after eating proteins. Interestingly, their findings published in Nature Communication also showed that the gene is specific to females.

Feeding is an innate behavior in the animal kingdom. Proper amount of food consumption is critical for survival and health, as well as for producing high-quality progeny. Although appetite signals for promoting eating have been widely investigated, the mechanisms underlying feeding termination are poorly understood.

Among the three macronutrients (proteins, carbohydrates and fat), proteins are known to exert the greatest inhibitory effect in feeding control. Nevertheless, protein-specific nutrient sensing signals have not been identified.

In previous research, Professor Li Yan and her team identified a gene called female-specific independent of transformer (Fit) whose expression is dramatically elevated following pre-feeding of protein food, but not other types of food.

In the current study, they showed that overexpression of FIT suppressed protein consumption, while Fit mutant flies fail to stop eating after a big meal of protein.

Using both bioinformatics and experimental evidence, they revealed that FIT is a fat body-secreted peptide circulating in the fly hemolymph. Secreted FIT promoted the release of Drosophila insulin-like peptide 2 (DIPL2) in the brain, thereby regulating feeding behavior through the insulin signaling.

FIT conveys the signal of internal amino acid (AA) levels from the fat body (FB) to the brain for nutrient sensing and feeding control. Credit: Institute of Biophysics.

Interestingly, Fit is a sexually dimorphic gene, with about ten-fold higher levels in females than that in males. Accordingly, protein intake-induced DILP2 release and feeding inhibition were also much more evident in female flies than in males.

The article can be found at: Sun et al. (2017) Drosophila FIT is a Protein-specific Satiety Hormone Essential for Feeding Control.


Source: Chinese Academy of Sciences; Photo: Shutterstock.
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