Your gut senses the difference between real sugar and artificial
sweetener
Sugar preference isn't just a matter of taste - it's deeper than that


Date:
January 13, 2022
Source:
Duke University
Summary:
Why do mice without taste buds still prefer real sugar to the
fake stuff? 'We've identified the cells that make us eat sugar,
and they are in the gut,' said one of the researchers. Specialized
cells in the upper gut send different signals to the brain for
sugar and sugar substitute.



FULL STORY ==========================================================================
Your taste buds may or may not be able to tell real sugar from a sugar substitute, but there are cells in your intestines that can and do
distinguish between the two sweet solutions. And they can communicate
the difference to your brain in milliseconds.


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Not long after the sweet taste receptor was identified in the mouths
of mice 20 years ago, scientists attempted to knock those taste buds
out. But they were surprised to find that mice could still somehow
discern and prefer natural sugar to artificial sweetener, even without
a sense of taste.

The answer to this riddle lies much further down in the digestive
tract, at the upper end of the gut just after the stomach, according
to research led by Diego Boho'rquez, an associate professor of medicine
and neurobiology in the Duke University School of Medicine.

In a paper appearing Jan. 13 in Nature Neuroscience, "we've identified the cells that make us eat sugar, and they are in the gut," Boho'rquez said.

Infusing sugar directly into the lower intestine or colon does not have
the same effect. The sensing cells are in the upper reaches of the gut,
he said.

Having discovered a gut cell called the neuropod cell, Boho'rquez with his research team has been pursuing this cell's critical role as a connection between what's inside the gut and its influence in the brain. The gut,
he argues, talks directly to the brain, changing our eating behavior. And
in the long run, these findings may lead to entirely new ways of treating diseases.

Originally termed enteroendrocrine cells because of their ability to
secrete hormones, specialized neuropod cells can communicate with neurons
via rapid synaptic connections and are distributed throughout the lining
of the upper gut. In addition to producing relatively slow-acting hormone signals, the Boho'rquez research team has shown that these cells also
produce fast-acting neurotransmitter signals that reach the vagus nerve
and then the brain within milliseconds.



========================================================================== Boho'rquez said his group's latest findings further show that neuropods
are sensory cells of the nervous system just like taste buds in the
tongue or the retinal cone cells in the eye that help us see colors.

"These cells work just like the retinal cone cells that that are able to
sense the wavelength of light," Boho'rquez said. "They sense traces of
sugar versus sweetener and then they release different neurotransmitters
that go into different cells in the vagus nerve, and ultimately, the
animal knows 'this is sugar' or 'this is sweetener.'" Using lab-grown organoids from mouse and human cells to represent the small intestine and duodenum (upper gut), the researchers showed in a small experiment that
real sugar stimulated individual neuropod cells to release glutamate as
a neurotransmitter. Artificial sugar triggered the release of a different neurotransmitter, ATP.

Using a technique called optogenetics, the scientists were then able
to turn the neuropod cells on and off in the gut of a living mouse to
show whether the animal's preference for real sugar was being driven by
signals from the gut.

The key enabling technology for the optogenetic work was a new flexible waveguide fiber developed by MIT scientists. This flexible fiber delivers
light throughout the gut in a living animal to trigger a genetic response
that silenced the neuropod cells. With their neuropod cells switched off,
the animal no longer showed a clear preference for real sugar.

"We trust our gut with the food we eat," Boho'rquez said. "Sugar has
both taste and nutritive value and the gut is able to identify both."
"Many people struggle with sugar cravings, and now we have a better understanding of how the gut senses sugars (and why artificial sweeteners
don't curb those cravings)," said co-first author Kelly Buchanan, a
former Duke University School of Medicine student who is now an Internal Medicine resident at Massachusetts General Hospital. "We hope to target
this circuit to treat diseases we see every day in the clinic." In future work, Boho'rquez said he will be showing how these cells also recognize
other macronutrients. "We always talk about 'a gut sense,' and say things
like 'trust your gut,' well, there's something to this," Boho'rquez said.

"We can change a mouse's behavior from the gut," Boho'rquez said, which
gives him great hope for new therapies targeting the gut.

Support for this study came from the National Institutes of Health
(R21 AT010818, DP2 MH122402, R01 DK131112), the Howard Hughes Medical Institute, the Hartwell Foundation and the MIT McGovern Institute.

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get wrong about diet and exercise. Claim_yours_now_>>> landing.newscientist.com/what-is-new-scientist-sd/ ========================================================================== Story Source: Materials provided by Duke_University. Original written
by Karl Leif Bates.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Kelly L. Buchanan, Laura E. Rupprecht, M. Maya Kaelberer, Atharva
Sahasrabudhe, Marguerita E. Klein, Jorge A. Villalobos, Winston
W. Liu, Annabelle Yang, Justin Gelman, Seongjun Park, Polina
Anikeeva, Diego V.

Boho'rquez. The preference for sugar over sweetener depends
on a gut sensor cell. Nature Neuroscience, 2022; DOI:
10.1038/s41593-021-00982-7 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220113111410.htm
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