When we eat, food sends a signal that promotes the release of insulin, which delivers nutrients to our bodies. When we don’t eat, we don’t get that signal in our brains and our bodies start to use fat stores to deliver the nutrition.
That’s what we thought. But it’s not the whole story because it’s leaving out two important players. The molecules called FLP-7 in the brain and INS-7 in the gut.
“The INS-7 peptide that’s secreted from the gut functions in the neurons that release FLP-7 and acts as a gate and says, ‘Stop!’” said Supriya Srinivasan, professor of neuroscience at Scripps Research in San Diego.
Thus, the body stops burning fat and INS-7 earns the name “insulin antagonist.”
It may seem strange that anything would tell the brains to stop burning fat during a fast, when we would seem to need it. Maybe the function evolved to make our fat, and our food supplies, last longer.
Whatever the case, the effect of INS-7 is eventually ultimately overridden, and the hormone FLP-7 (scientists pronounce it Flip-7) is released and goes about its job of stimulating fat use.
But, Srinivasan says, understanding the power of INS-7 could provide new medical ways to begin fat loss among people with obesity. You can imagine a drug that blocked INS-7 and its effects would promote the burning of fat, not prevent it.
“What the study allows us to start thinking about is how insulin antagonism in mammals may be a physiologically relevant tool that could be harnessed for metabolic benefits,” Srinivasan said.
Srinivasan was the lead author of an article about the research published in Nature Communications.
The experiments at Scripps Research were done on worms called C. elegans. They’re great to study since they have such a remarkable physical similarity to humans. The insulin antagonist INS-7 in worms has what’s called an ortholog, or equivalent, in humans called INSL-5.
Fasting has shown many health benefits. A study of firefighters in San Diego — who did a daily 14-hour fast — showed they had lower blood pressure and lower blood sugar. And that’s not all.
“Both fasting and calorie restrictions have beneficial effects on lifespan. That’s been shown,” Srinivasan said.
And scientific advances could make those health benefits more within reach of people who have suffered the effects of weight gain.
