Gut Molecule Blocks Fat Burning Signal During Fasting

Recent research on Caenorhabditis elegans (C. elegans) has revealed an unexpected mechanism that slows fat burning during fasting, potentially shedding light on similar processes in humans. Scientists at Scripps Research have identified a gut-produced molecule that communicates with the brain to regulate fat metabolism during periods of food scarcity.

The study, published in Nature Communications, focused on INS-7, an insulin-like molecule produced by intestinal cells in C. elegans. Unlike typical insulin, which activates insulin receptors, INS-7 blocks these receptors in brain cells. This blockade triggers a series of events that ultimately halts the production of FLP-7, a hormone known to stimulate fat burning.

Senior author Supriya Srinivasan explains: "INS-7 is essentially a signal from the gut telling the brain to conserve fat stores due to the absence of incoming food." This finding challenges previous understanding of insulin's role and highlights the complexity of gut-brain communication in metabolic regulation.

The discovery of INS-7's function came after an extensive process of eliminating over 100 signaling molecules from C. elegans intestines and observing their effects on FLP-7 production. While the exact equivalent of INS-7 has not been identified in humans, this research opens new avenues for understanding the broader impacts of fasting on health beyond simple calorie restriction. 

This study builds on previous work by Srinivasan's team, which identified FLP-7 as a brain hormone triggering fat burning in C. elegans. The new findings provide insight into the reverse communication pathway from gut to brain, a process that has long puzzled scientists due to C. elegans' lack of sensory nerves in their intestines.

As compounds mimicking gut hormones gain popularity in treating obesity and diabetes, understanding these gut-brain signaling pathways could lead to new therapeutic approaches. Future research will explore how C. elegans gut cells are triggered to produce INS-7 during fasting and which brain cell types are affected by this molecule.