How Fat Signals Us to Eat More of It

Charles S. Zuker
Columbia University Neuroscience Physiology
Source: HHMI

Scientists discover how fat triggers a gut-to-brain mechanism that drives us to keep consuming more of it. Their findings could one day lead to interventions to help treat obesity and associated disorders.

Short ribs glazed in a sweet sticky sauce and slow-cooked to perfection, potato chips hand-fried and tossed with a generous coating of sour cream, chicken wings battered and double-fried so that they stay crispy for hours. What is it about these, and other, mouth-watering — but incredibly fatty — foods that makes us reach out, and keep coming back for more?

How they taste on the tongue is one part of the story, but to really understand what drives “our insatiable appetite for fat,” we have to examine what happens after fat is consumed, says Columbia University’s Charles Zuker, a neuroscientist and molecular geneticist who has been a Howard Hughes Medical Institute (HHMI) Investigator since 1989.

Two years ago, Zuker and his team reported how sugar, upon reaching the gut, triggers signals that are sent to the brain, thus fueling cravings for sweet treats. Now, in an article published in Nature on September 7, 2022, they describe a similar gut-to-brain circuit that underlies a preference for fat.

“The gut is the source of our great desire for fat and sugar,” says Zuker.

The topic in question is an incredibly timely one, given the current global obesity epidemic. An estimated 13 percent of adults worldwide are obese — thrice that in 1975. In the US, that figure is even higher — at a staggering 42 percent. “It’s a very significant and important health problem,” says Zuker.

Having a high body-mass index is a risk factor for stroke, diabetes, and several other diseases. “It’s clear that if we want to help make a difference here, we need to understand the biological basis for our strong appetite for fat and sugar,” he says. Doing so will help us design interventions in the future to “suppress this strong drive to consume” and combat obesity.

Using science to solve ancient Chinese art mystery

UC assistant professor Pietro Strobbia consulted with the Cincinnati Art Museum to solve a mystery about one of its ancient Chinese masterpieces.
Photo credit: Andrew Higley/University of Cincinnati

The Cincinnati Art Museum turned to a scientist at the University of Cincinnati for help solving a mystery 1,300 years in the making.

The museum’s Chinese dancing horse sculpture is so realistic that the fiery steed seems ready to gallop off its pedestal. But East Asian art curator Hou-mei Sung questioned the authenticity of a decorative tassel on the terracotta horse’s forehead that resembles the horn of a mythological unicorn.

The museum reached out to UC College of Arts and Sciences assistant professor of chemistry Pietro Strobbia for help to determine if the tassel was original to the work.

“Many museums have a conservator but not necessarily scientific facilities needed to do this kind of examination,” Strobbia said. “The forehead tassel looks original, but the museum asked us to determine what materials it was made from.”

Strobbia and his collaborators wrote about the project for a paper published in the journal Heritage Science.

Highly reflective mirrors from the inkjet printer

Colored, printed mirror layer on a film. Inkjet printing allows structuring so that large-scale logos can also be printed
Credit: Qihao Jin, KIT

Dielectric mirrors, also called Bragg mirrors, can almost completely reflect light. They are therefore suitable for countless applications, such as in camera systems, in microscopy, in medical technology or in sensor systems. So far, these mirrors had to be manufactured in expensive vacuum devices. Researchers at the Karlsruhe Institute of Technology (KIT) have now printed high quality Bragg mirrors with inkjet printers for the first time. The process could open the way to digital production of tailor-made mirrors. The results appeared in Advanced Materials.

For Bragg mirrors, several layers of material are applied thinly to a carrier. These mirrors, which consist of a large number of thin layers, form an optical mirror that ensures that light of a certain wavelength is specifically reflected. How strongly Bragg mirrors reflect depends on the materials, but also on how many layers you apply and how thick they are. So far, Bragg mirrors have had to be manufactured with expensive vacuum production systems. The Karlsruhe team succeeded for the first time in printing them on different carriers. This can considerably simplify production.

The bean bug brain’s biological clock

 Brain glutamate dynamics photoperiodically change based on the circadian clock gene and mediate the cellular response of oviposition-promoting neurons.
Credit: Masaharu Hasebe and Sakiko Shiga

Did you know that not only does an organism’s body have a biological clock that can tell the time of the day, it can also tell the time of the year? Now, researchers from Japan have found that one capable little molecule may be behind the mechanism by which the biological clock keeps track of the seasons.

In a study that was recently published in PLOS Biology, researchers from Osaka University reveal that glutamate signaling is responsible for the seasonal regulation of reproduction in bean bugs by genes involved in maintaining circadian rhythm.

The circadian rhythm is driven by a biological clock that controls body processes based on time of day. A related process is photoperiod sensitivity, or seasonal regulation, in which body processes are regulated on a seasonal basis based on the length of the daytime and nighttime periods.

“Previous studies have shown that circadian clock genes are involved not only in regulating daily processes, but also in regulating seasonal events, such as reproduction in insects,” states Masaharu Hasebe, first author on the study. “However, the mechanism governing this interaction was unclear.”

Turning carbon dioxide into valuable products

Professor Ariel Furst (center), undergraduate Rachel Ahlmark (left), postdoc Gang Fan (right), and their colleagues are employing biological materials, including DNA, to achieve the conversion of carbon dioxide to valuable products.
Credits: Gretchen Ertl

Carbon dioxide (CO2) is a major contributor to climate change and a significant product of many human activities, notably industrial manufacturing. A major goal in the energy field has been to chemically convert emitted CO2 into valuable chemicals or fuels. But while CO2 is available in abundance, it has not yet been widely used to generate value-added products. Why not?

The reason is that CO2 molecules are highly stable and therefore not prone to being chemically converted to a different form. Researchers have sought materials and device designs that could help spur that conversion, but nothing has worked well enough to yield an efficient, cost-effective system.

Two years ago, Ariel Furst, the Raymond (1921) and Helen St. Laurent Career Development Professor of Chemical Engineering at MIT, decided to try using something different — a material that gets more attention in discussions of biology than of chemical engineering. Already, results from work in her lab suggest that her unusual approach is paying off.

Two new rocky worlds around an ultra-cool star

The telescopes of the SPECULOOS Southern Observatory gaze out into the stunning night sky over the Atacama Desert, Chile.
Credit: ESO/ P. Horålek

An international research team, with the participation of the University of Bern and the National Centre of Competence in Research (NCCR) PlanetS, discovered two "super-Earth" exoplanets. One is located at just the right distance from its star to potentially hold liquid water on its surface.

Most of the planets that have been discovered around other stars – also known as exoplanets – are bad candidates for life as we know it. They are either scorching hot or freezing cold, and the majority consist of nothing but gas. Relatively small terrestrial planets, like our Earth, are difficult to detect. Only a handful are known that receive just the right amount of radiation from their star to allow liquid water on their surface. The reported discovery of a promising candidate for such a world, made by a team of researchers with the participation of the University of Bern and the National Centre of Competence in Research (NCCR) PlanetS, is therefore a significant one. The team published their results in the journal Astronomy & Astrophysics. (As of this posting not yet released)

Endangered Amargosa Voles Begin to Repopulate Desert Habitat

This landscape shows the Amargosa Valley at sunset. Amargosa voles are endemic to unique Mojave Desert marshes fed by natural springs and the Amargosa River.
Credit: University of California, Davis

Seven years of carefully planned habitat restoration on private land in the Mojave Desert have yielded hope for the persistence of the endangered Amargosa vole. In early August, a photograph from a wildlife camera placed by researchers from the University of California, Davis, and dated July 3 revealed the presence of one, possibly two, vole pups born from parents that were reintroduced to restored marsh habitat on private land in Shoshone Village, Inyo County.

The Amargosa vole was first discovered in the marshes of Shoshone in the late 1800s but had disappeared by the early 1900s because of habitat conversion to agriculture and other uses that destroyed the marshes. The only other place in the world where the voles persist in the wild is near the town of Tecopa, about 8 miles south of Shoshone.

Restoration of the Shoshone Spring marsh started in 2015 as a joint effort of Shoshone Village, the Amargosa Conservancy, UC Davis and the California Department of Fish and Wildlife (CDFW). The restoration was funded by U.S. Fish and Wildlife Service (USFWS) Section 6 and Partners in Fish and Wildlife grants.

Photosynthesis copycat may improve solar cells

The diagram shows light hitting the semiconductor (purple) layered over the mirror-like photonic structure. The polaritons—mixtures of light, electrons and “holes”—then travel to the detector (truncated disc), where they generate current.
Image credit: Xinjing Huang and Bin Liu, Optoelectronic Components and Materials Group

A relatively new kind of semiconductor, layered atop a mirror-like structure, can mimic the way that leaves move energy from the sun over relatively long distances before using it to fuel chemical reactions. The approach may one day improve the efficiency of solar cells.

“Energy transport is one of the crucial steps for solar energy harvesting and conversion in solar cells,” said Bin Liu, a postdoctoral researcher in electrical and computer engineering and first author of the study in the journal Optica.

“We created a structure that can support hybrid light-matter mixture states, enabling efficient and exceptionally long-range energy transport.”

One of the ways that solar cells lose energy is in leakage currents generated in the absence of light. This occurs in the part of the solar cell that takes the negatively charged electrons and the positively charged “holes,” generated by the absorption of light, and separates them at a junction between different semiconductors to create an electrical current.

Remote-controllable cyborg cockroach

Cyborg cockroach
An insect developed in this study, equipped with a tiny wireless control module that is powered by a rechargeable battery attached to a solar cell.
Credit: RIKEN

An international team led by researchers at the RIKEN Cluster for Pioneering Research (CPR) has engineered a system for creating remote controlled cyborg cockroaches, equipped with a tiny wireless control module that is powered by a rechargeable battery attached to a solar cell. Despite the mechanical devices, ultrathin electronics and flexible materials allow the insects to move freely. These achievements, reported in the scientific journal npj Flexible Electronics on September 5, will help make the use of cyborg insects a practical reality.

Researchers have been trying to design cyborg insects—part insect, part machine—to help inspect hazardous areas or monitor the environment. However, for the use of cyborg insects to be practical, handlers must be able to control them remotely for long periods of time. This requires wireless control of their leg segments, powered by a tiny rechargeable battery. Keeping the battery adequately charged is fundamental—nobody wants a suddenly out-of-control team of cyborg cockroaches roaming around. While it’s possible to build docking stations for recharging the battery, the need to return and recharge could disrupt time-sensitive missions. Therefore, the best solution is to include an on-board solar cell that can continuously ensure that the battery stays charged.

All of this is easier said than done. To successfully integrate these devices into a cockroach that has limited surface area required the research team to develop a special backpack, ultrathin organic solar cell modules, and an adhesion system that keeps the machinery attached for long periods of time while also allowing natural movements.

Engineers Study Bird Flight

Photo credit: Karin Hiselius on Unsplash

People have been fascinated by bird flight for centuries, but exactly how birds can be so agile in the air remains mysterious. A new study, published the week of Sept. 5 in Proceedings of the National Academy of Sciences, uses modeling and aerodynamics to describe how gulls can change the shape of their wings to control their response to gusts or other disturbances. The lessons could one day apply to uncrewed aerial vehicles or other flying machines.

“Birds easily perform challenging maneuvers and they’re adaptable, so what exactly about their flight is most useful to implement in future aircraft?” said Christina Harvey, assistant professor in the Department of Mechanical and Aerospace Engineering at the University of California, Davis, and lead author on the paper.

Harvey began studying gulls as a master’s student in zoology at the University of British Columbia, after earning her bachelor’s degree in mechanical engineering.

“Gulls are very common and easy to find, and they’re really impressive gliders,” she said.

Harvey continued her work on gulls as a doctoral student at the University of Michigan. She recently joined the faculty at UC Davis after completing her Ph.D. in aerospace engineering.