In positive news for people with diabetes who struggle to control sugar cravings, a new study identifies a hormone that suppresses “sweet tooth”.
The research, conducted at the University of Iowa, found that the hormone, fibroblast growth factor 21 (FGF21), is released in response to high carbohydrate levels. Once it has been released, FGF21 signals to the brain that sweet foods are no longer needed.
Although it is far from the only hormone that regulates appetite, FGF21 is the first hormone that affects a specific macronutrient – in this case, carbohydrate. Sugar is a highly refined form of carbohydrate.
“This is the first liver-derived hormone we know that regulates sugar intake specifically,” says Matthew Potthoff, assistant professor of pharmacology at the University of Iowa Carver College of Medicine.
“We’ve known for a while that FGF21 can enhance insulin sensitivity,” said Lucas BonDurant, of the Interdisciplinary Graduate Program in Molecular and Cellular Biology and co-first author in the study. “Now, there’s this dimension where FGF21 can help people who might not be able to sense when they’ve had enough sugar, which may contribute to diabetes.”
The study is based on previous research that found a link between certain DNA mutations and intake of certain macronutrients. Because two mutations were located next to the FGF21 gene, the researchers were interested in its potential role in regulating macronutrient intake.
FGF21 was tested on mouse models. Normal mice were injected with FGF21, then allowed to choose between a normal diet and one high in sugar. The mice didn’t stop eating sugar altogether, but they did eat seven times less after being injected with FGF21.
The, the researchers genetically modified mice to either produce no FGF21 or excessive amounts of it. Again, the mice were allowed to choose between a normal diet and a high sugar diet. The mice that didn’t produce any FGF21 ate far more sugar than those that produced excessive amounts, who ate less than normal.
The results are promising; FGF21 could play a significant role in curbing sugar cravings. However, it doesn’t affect all sugar equally, and it doesn’t affect complex carbohydrates – only simple ones such as sugar.
More work is needed to explain exactly how FGF21 works. The researchers don’t know which specific neural pathways allow FGF21 to manage macronutrient intake. For now, the researchers are examining the hypothalamus, a part of the brain that regulates feeding behaviour.
“In addition to identifying these neural pathways, we would like to see if additional hormones exist to regulate appetite for specific macronutrients like fat and protein, comparable to the effects of FGF21 on carbohydrate intake,” said Potthoff. “If so, how do those signal intertwine to regulate the neural sensing of different macronutrients.”
The findings are published in Cell Metabolism.

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