Wednesday, January 10, 2024

Shape matters: How microplastic travels that far

New study: Microplastic fibers are settling substantially slower than spherical particles in the atmosphere and might even reach stratosphere

Peer-Reviewed Publication

MAX PLANCK INSTITUTE FOR DYNAMICS AND SELF-ORGANIZATION

Microplastic particles can be found in the most remote corners of our planet. For some places, such as Arctic glaciers and ice sheets, atmospheric transport is the only conceivable pathway. However, it is puzzling how some quite large and mostly fiber-like microplastics found their way to such places, even though atmospheric transport models predict that such large particles fall out of the atmosphere close to their sources.

The study by an interdisciplinary group of scientists from the University of Vienna, Austria and the Max Planck Institute for Dynamics and Self-Organisation in Göttingen, Germany, has approached this puzzle via an innovative combination of laboratory experiments and model simulations. The researchers first determined experimentally how fast microplastic fibers settle in the atmosphere and found that fibers settle substantially slower than spheres of the same mass.

Lack of data on microplastic fibers in air

Mohsen Bagheri of the Max Planck Institute for Dynamics and Self-Organisation, who oversaw the laboratory experiments, comments: "Surprisingly, there is almost no data in the literature on the dynamics of microplastic fibers as they settle in air. This lack of data is largely due to the challenges of conducting controlled and repeatable experiments on such small particles in air. With advances in submicron-resolution 3D printing and the development of a novel experimental setup that allows tracking of individual microplastics in air, we were able to fill this knowledge gap and improve existing models in this study".

The researchers then implemented a model describing the settling process of non-spherical particles into a global atmospheric transport model. The differences to spherical particles were dramatic: fibers with lengths of up to 1.5 mm could reach the most remote places of Earth in the model, while the model showed that spheres of the same mass settled much closer to the plastic source regions.

Daria Tatsii from the Department of Meteorology and Geophysics at the University of Vienna, the first author of the study, says: "With the novel laboratory experiments and modelling analysis, we certainly reduce uncertainties about the atmospheric transport of fibers and can finally explain via modelling why microplastics reach very remote regions of the planet. An important result of the study is that our analysis is applicable not only to microplastics, but also to any other particles such as volcanic ash, mineral dust, pollen, etc.".

Fibers might have an impact even on the stratosphere

Another finding is that, in the model, plastic fibers could reach much greater heights in the atmosphere than spheres of the same mass. Andreas Stohl of the University of Vienna who initiated the study comments: "This could have implications for cloud processes and even for stratospheric ozone, since it seems possible that microplastic fibers are abundant in the upper troposphere and might even reach the stratosphere. For instance, we cannot rule out that chlorine contained in these particles is harmful to the ozone layer. However, right now we do not even know how much plastic, and in which sizes and shapes, is emitted to the atmosphere, and we also do not know what happens to it under the extreme conditions of the upper troposphere and stratosphere. We are lacking very basic data. But given the dramatic increase in global plastic production, we have to be watchful."

Despite all uncertainties, one thing is clear from the paper: The often peculiar shapes of microplastic particles need to be considered when investigating their environmental impact.

JOURNAL

Environmental Science & Technology

DOI

10.1021/acs.est.3c08209

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Shape Matters: Long-Range Transport of Microplastic Fibers in the Atmosphere

Microplastics affect soil fungi depending on drought conditions

Peer-Reviewed Publication

WILEY

Moisture levels in the soil can impact the effects that microplastic pollution has on soil fungi, according to new research published in Environmental Microbiology.

By studying soil samples mixed with microplastics under different conditions, investigators found that when soil is well-watered, toxic chemicals in microplastics can leach into the soil and hinder soil fungal richness. With dry soil, however, the leaching of water-extractable chemicals is less pronounced and therefore less impactful on soil fungal structure.

The researchers also noted that under dry conditions, microplastics help soil hold water for longer, which could help mitigate the effects of drought. Although this could be considered a desirable scenario, these interactions imply complex challenges for land management.

“Microplastics in soil alter soil fungal communities, which negatively affect soil ecosystem functions,” said corresponding author Yudi M. Lozano, PhD, of Freie Universität Berlin and the Berlin-Brandenburg Institute of Advanced Biodiversity Research, in Germany.

URL upon publication: https://onlinelibrary.wiley.com/doi/10.1111/1462-2920.16549

Additional Information
NOTE: The information contained in this release is protected by copyright. Please include journal attribution in all coverage. For more information or to obtain a PDF of any study, please contact: Sara Henning-Stout, newsroom@wiley.com.

About the Journal
Environmental Microbiology is devoted to the advancement of our understanding of microbial interactions and microbial processes in the environment, and publishes original research reporting significant advances in or relating to this subject. Environmental Microbiology is published jointly with Applied Microbiology International.

About Wiley
Wiley is a knowledge company and a global leader in research, publishing, and knowledge solutions. Dedicated to the creation and application of knowledge, Wiley serves the world’s researchers, learners, innovators, and leaders, helping them achieve their goals and solve the world's most important challenges. For more than two centuries, Wiley has been delivering on its timeless mission to unlock human potential. Visit us at Wiley.com. Follow us on Facebook, Twitter, LinkedIn and Instagram.

JOURNAL

Environmental Microbiology

DOI

10.1111/1462-2920.16549

ARTICLE TITLE

Microplastic fibers affect soil fungal communities depending on drought conditions with consequences for ecosystem functions

ARTICLE PUBLICATION DATE

10-Jan-2024

More than 900 chemicals, many found in consumer products and the environment, display breast-cancer causing traits

New study advances understanding of how endocrine disrupting chemicals influence breast cancer risk

Peer-Reviewed Publication

SILENT SPRING INSTITUTE

With tens of thousands of synthetic chemicals on the market, and new ones in development all the time, knowing which ones might be harmful is a challenge both for the federal agencies that regulate them and the companies that use them in products. Now scientists have found a quick way to predict if a chemical is likely to cause breast cancer based on whether the chemical harbors specific traits.

“This new study provides a roadmap for regulators and manufacturers to quickly flag chemicals that could contribute to breast cancer in order to prevent their use in consumer products and find safer alternatives,” says lead author Dr. Jennifer Kay, a research scientist at Silent Spring Institute.

Breast cancer remains the most commonly diagnosed cancer in the United States. Recent data show rates increasing in young women, a trend that can’t be explained by genetics. “We need new tools to identify environmental exposures that could be contributing to this trend so we can develop prevention strategies and reduce the burden of the disease,” says Kay.

Hormone signals

Kay and her colleagues searched through multiple international and U.S. government databases to identify chemicals that have been found to cause mammary tumors in animals. The databases were from the International Agency for Cancer Research (IARC), the National Toxicology Program, the U.S. Environmental Protection Agency (EPA), and the National Cancer Institute, among others.

The researchers also looked at data from EPA’s ToxCast program to identify chemicals that alter the body’s hormones, or endocrine disruptors, in ways that could promote breast cancer. The team looked specifically for chemicals that activate the estrogen receptor—a receptor present in breast cells—as well as chemicals that cause cells to make more estrogen or progesterone, an established risk factor for breast cancer.

Reporting in Environmental Health Perspectives, the researchers identified a total of 921 chemicals that could promote the development of breast cancer. Ninety percent of the chemicals are ones that people are commonly exposed to in consumer products, food and drink, pesticides, medications, and workplaces.

A breakdown of the list revealed 278 chemicals that cause mammary tumors in animals. More than half of the chemicals cause cells to make more estrogen or progesterone, and about a third activate the estrogen receptor. “Breast cancer is a hormonal disease, so the fact that so many chemicals can alter estrogen and progesterone is concerning,” says Kay.

Since damage to DNA can also trigger cancer, the researchers searched additional databases and found 420 of the chemicals on their list both damage DNA and alter hormones, which could make them riskier. What’s more, the team’s analysis found that chemicals that cause mammary tumors in animals are more likely to have these DNA damaging and hormone-disrupting characteristics than ones that don’t.

“Historically, chemicals that cause mammary tumors in animals were seen as the best predictor of whether they might cause breast cancer in humans,” says co-author Ruthann Rudel, director of research at Silent Spring. “But animal studies are expensive and time consuming, which is why so many chemicals have not been tested. Our findings show that screening chemicals for these hormonal traits could be an effective strategy for flagging potential breast carcinogens.”

A roadmap for safety

Over the past decade, there has been growing evidence that environmental chemicals are important contributing factors in the development of cancer. A number of studies in people have found links between breast cancer and pesticides, hair dyes, and air pollution. Other studies suggest exposure to hormone-disrupting chemicals early in life, in the womb or during puberty, can alter breast development in ways that could increase the risk of cancer later on.

To observe those associations, however, scientists have to wait until hundreds or thousands of children and women have been exposed to a chemical and check, often many years later, to see who develops breast cancer. “It’s not feasible, nor is it ethical, to wait that long,” says Rudel. “And it’s another reason why we need better tools for predicting which chemicals are likely to lead to breast cancer so we can avoid those exposures.”

The Silent Spring study could have implications for how EPA assesses chemicals for safety. For instance, the chemicals identified in the study include more than 30 pesticides that EPA previously approved for use despite evidence linking the chemicals with mammary tumors.

This fall, EPA proposed a new strategic plan to ensure that pesticides are evaluated for their effects on hormones. The study authors hope their new comprehensive list of breast cancer-relevant chemicals, which includes hundreds of endocrine disruptors, will inform EPA’s plan and better protect the public from harmful exposures.

Additional co-authors of the new study include Megan Schwarzman at UC Berkeley and Julia Brody at Silent Spring Institute.

Funding for this project was provided by the California Breast Cancer Research Program (Grant #23QB-1881) and charitable donations to the Safer Chemicals Program at Silent Spring Institute.

Reference:

Kay, J.E., J.G. Brody, M. Schwarzman, R.A. Rudel. 2023. Application of the Key Characteristics framework to identify potential breast carcinogens using publicly available in vivo, in vitro, and in silico data. Environmental Health Perspectives. DOI: 10.1289/EHP13233

JOURNAL

Environmental Health Perspectives

DOI

10.1289/EHP13233

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

Cells

ARTICLE TITLE

Application of the Key Characteristics framework to identify potential breast carcinogens using publicly available in vivo, in vitro, and in silico data

ARTICLE PUBLICATION DATE

10-Jan-2024

COI STATEMENT

Silent Spring Institute is a scientific research organization dedicated to studying environmental factors in women’s health. The institute is a 501(c)3 public charity funded by federal grants and contracts, foundation grants, and private donations, including from breast cancer organizations. Study funders had no role in study design; in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the article for publication.

FOREVER CHEMICALS

PFAS flow equally between Arctic Ocean and Atlantic Ocean, study finds

Peer-Reviewed Publication

AMERICAN CHEMICAL SOCIETY

PFAS flow equally between Arctic Ocean and Atlantic Ocean, study finds — IMAGE:
PFAS COME AND GO BETWEEN THE ARCTIC AND ATLANTIC OCEANS AT ROUGHLY EQUAL RATES.
view more
CREDIT: ADAPTED FROM ENVIRONMENTAL SCIENCE & TECHNOLOGY LETTERS 2024, DOI: 10.1021/ACS.ESTLETT.3C00835

The frigid Arctic Ocean is far removed from the places most people live, but even so, “forever chemicals” reach this remote landscape. Now, research in ACS’ Environmental Science & Technology Letters suggests that per- and polyfluoroalkyl substances (PFAS) won't stay there indefinitely. Instead, they are transported in a feedback loop, with the Arctic Ocean potentially exporting as many PFAS to the North Atlantic Ocean as it receives, circulating the compounds around the world.

To get to the Arctic Ocean, some PFAS hitch a ride in the air and fall onto the ocean’s surface, but others enter from adjacent oceans. The potential impact of these compounds on marine organisms depends on what PFAS are present and how much, which are ever-changing as water flows between the Arctic Ocean and the North Atlantic Ocean. These waterbodies are connected by the Fram Strait, which sits to the northeast of Greenland near the Svalbard archipelago. Warm water travels north on the eastern side of the strait, and cold water flows south along the western side, providing a dynamic gateway for PFAS transportation. So, Rainer Lohmann and colleagues wanted to track the movement of PFAS in this region and identify how water circulation influences the mix of contaminants in the Arctic Ocean.

The researchers deployed passive sampling systems, which took up PFAS into a sorbent-filled microporous membrane from water as it flowed past. They put the systems at three locations in the Fram Strait, and at four depths in each location. After a year, the team retrieved the systems and measured the collected PFAS using liquid chromatography-mass spectrometry. The researchers overserved that:

Ten PFAS were detected in at least one passive sampler, however, one substance detected in the area by previous research teams wasn’t among them.
Two compounds known as PFOA and PFOS, which are being phased out, were present at the highest levels. Newer, short-chain PFAS were also routinely present.
Surprisingly, several PFAS were found in water below 3,000 feet deep. The team suggests that these compounds could have gotten there by attaching to particles as they fell to the seafloor.

The team calculated the amounts of PFAS flowing in each direction through the Fram Strait. Their data showed that in one year around 123 tons traveled into the Arctic Ocean and about 110 tons moved into the Atlantic Ocean. According to the researchers, these values are the largest of any pollutant reported in the strait, demonstrating how significant the back-and-forth circulation of PFAS is in the Arctic Ocean.

The authors acknowledge funding from the University of Rhode Island Sources, Transport, Exposure and Effects of PFAS (STEEP) Superfund Center, and the Alfred Wegener Institute Long Term Ecological Research Hausgarten program.

The paper’s abstract will be available on Jan. 10 at 8 a.m. Eastern time here: http://pubs.acs.org/doi/abs/10.1021/acs.estlett.3c00835

###

The American Chemical Society (ACS) is a nonprofit organization chartered by the U.S. Congress. ACS’ mission is to advance the broader chemistry enterprise and its practitioners for the benefit of Earth and all its people. The Society is a global leader in promoting excellence in science education and providing access to chemistry-related information and research through its multiple research solutions, peer-reviewed journals, scientific conferences, eBooks and weekly news periodical Chemical & Engineering News. ACS journals are among the most cited, most trusted and most read within the scientific literature; however, ACS itself does not conduct chemical research. As a leader in scientific information solutions, its CAS division partners with global innovators to accelerate breakthroughs by curating, connecting and analyzing the world’s scientific knowledge. ACS’ main offices are in Washington, D.C., and Columbus, Ohio.

To automatically receive news releases from the American Chemical Society, contact newsroom@acs.org.

Note: ACS does not conduct research, but publishes and publicizes peer-reviewed scientific studies.

JOURNAL

Environmental Science & Technology Letters

DOI

10.1021/acs.estlett.3c00835

ARTICLE TITLE

Passive Sampler Derived Profiles and Mass Flows of Perfluorinated Alkyl Substances (PFASs) across the Fram Strait in the North Atlantic

ARTICLE PUBLICATION DATE

10-Jan-2024

Nafion byproduct 2 found in blood of well users near Fayetteville, NC

Peer-Reviewed Publication

NORTH CAROLINA STATE UNIVERSITY

Researchers from the GenX Exposure Study detected PFAS originating from a fluorochemical manufacturing plant – including Nafion byproduct 2 and GenX – in nearby private wells in Bladen and Cumberland Counties, N.C. PFAS refers to a group of chemicals called per- and polyfluoroalkyl substances.

“These compounds were released to the environment through air and wastewater emissions from the facility,” says Nadine Kotlarz, research scholar in the department of biological sciences at North Carolina State University, member of NC State’s Center for Human Health and the Environment (CHHE), and corresponding author of the paper.

“Air released from the facility caused the contamination of groundwater and private wells,” Kotlarz says. “In order to study how exposure to these chemicals may affect human health, we need to know the exposure levels across impacted people.”

In February 2019, the researchers recruited 153 people from this region who used 84 private wells to participate in the GenX Exposure Study. The participants lived within six miles of the fluorochemical facility. The participants provided well water and blood samples and filled out questionnaires about their well-water consumption.

The water and blood samples were screened for nine PFAS produced by the facility, including GenX and Nafion byproduct 2.

The PFAS found most frequently and at the highest concentrations in the wells included several low molecular weight PFAS (PMPA, PEPA, GenX, PFO2HxA, PFMOAA). The median concentration of GenX in the wells was 107 nanograms per liter (ng/L), 10 times higher than the U.S. Environmental Protection Agency’s (EPA) drinking water health advisory level of 10 ng/L.

However, these PFAS were not frequently detected in the private well users’ blood, even though they drank the well water.

Nafion byproduct 2, a higher molecular weight PFAS with a longer half-life, was detected frequently in wells at lower concentrations (the median concentration was 14 ng/L) and detected in more than half of participants’ blood.

“With Nafion byproduct 2, we saw that higher well-water concentration and the longer a person lived at their home correlated with higher blood levels,” Kotlarz says. “Well-water consumption is having an impact on exposure, and we know that several other PFAS were present in the wells, but due to the short half-lives of some PFAS (like GenX) in the body, we didn’t find all of the well water PFAS in blood.

“Blood levels of a chemical across a population are often used to characterize exposure,” Kotlarz says. “Without blood levels, we will need to estimate exposure to PFAS such as GenX another way in order to study their potential health effects.”

The research appears in the Journal of Exposure Science and Environmental Epidemiology. The GenX Exposure Study is supported by research funding from the National Institute of Environmental Health Sciences (1R21ES029353), NC State’s CHHE (P30 ES025128), the Center for Environmental and Health Effects of PFAS (P42 ES0310095), and the NC Policy Collaboratory. James McCord and Mark Strynar from the EPA; David Collier and Suzanne Lea from East Carolina University; Theresa Guillette of the Oak Ridge Institute for Science and Education Research; and Claire Critchley, Michael Cuffney, Zachary Hopkins, Detlef Knappe and Jane Hoppin of NC State also contributed to the work.

-peake-

Note to editors: An abstract follows.

“Per- and polyfluoroalkyl ether acids in well water and blood serum from private well users residing by a fluorochemical facility near Fayetteville, North Carolina”

DOI: 10.1038/s41370-023-00626-x

Authors: Nadine Kotlarz, Claire Critchley, Michael Cuffney, Zachary R. Hopkins, Detlef R.U. Knappe, Jane A. Hoppin, North Carolina State University; Theresa Guillette, Oak Ridge Institute for Science and Education Research; David Collier, C. Suzanne Lea, East Carolina University; James McCord, Mark Strynar, U.S. Environmental Protection Agency
Published: Jan. 10, 2024 in the Journal of Exposure Science and Environmental Epidemiology

Abstract:
BACKGROUND: A fluorochemical facility near Fayetteville, North Carolina, emitted per- and polyfluoroalkyl ether acids (PFEAs), a subgroup of per- and polyfluoroalkyl substances (PFAS), to air.
OBJECTIVE: Analyze PFAS in private wells near the facility and in blood from well users to assess relationships between PFEA levels in water and serum.
METHODS: In 2019, we recruited private well users into the GenX Exposure Study and collected blood and well water samples. We targeted 26 PFAS (11 PFEAs) in water and 27 PFAS (9 PFEAs) in serum using liquid chromatography-mass spectrometry. We used regression modeling to explore relationships between water and serum PFAS. For the only PFEA detected frequently in water and serum, Nafion byproduct 2, we used generalized estimating equation (GEE) models to assess well water exposure metrics and then adjusted for covariates that may influence Nafion byproduct 2 serum concentrations.
RESULTS: We enrolled 153 participants ages 6 and older (median=56 years) using 84 private wells. Most wells (74%) had ≥6 detectable PFEAs; median ∑PFEAs was 842 ng/L (interquartile range=197-1,760 ng/L). Low molecular weight PFEAs (PMPA, HFPO-DA [GenX], PEPA, PFO2HxA) were frequently detected in well water, had the highest median concentrations, but were not detectable in serum. Nafion byproduct 2 was detected in 73% of wells (median=14 ng/L) and 56% of serum samples (median=0.2 ng/mL). Cumulative dose (well concentration × duration at address) was positively associated with Nafion byproduct 2 serum levels and explained the most variability (10%). In the adjusted model, cumulative dose was associated with higher Nafion byproduct 2 serum levels while time outside the home was associated with lower levels.
SIGNIFICANCE: Serum biomarkers were not good measures of long-term exposure to low molecular weight PFEAs in a private well population. For Nafion byproduct 2, well water exposure metrics were associated with serum levels, particularly when incorporating exposure duration.

JOURNAL

Journal of Exposure Science & Environmental Epidemiology

DOI

10.1038/s41370-023-00626-x

METHOD OF RESEARCH

Observational study

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Per- and polyfluoroalkyl ether acids in well water and blood serum from private well users residing by a fluorochemical facility near Fayetteville, North Carolina

ARTICLE PUBLICATION DATE

10-Jan-2024

Nine new snail species discovered in Papua New Guinea, a biodiversity hot spot at risk

Peer-Reviewed Publication

FLORIDA MUSEUM OF NATURAL HISTORY

Nine new species of carnivorous land snails have been found in the remote forests of Papua New Guinea, a biodiversity hot spot. A new study describes the species, which are so small that all nine could fit together on a U.S. nickel. They present a rare opportunity to study a group that in many other places is disappearing fast. Worldwide, mollusks account for more than 50% of all recorded extinctions since the year 1500, and many of these were land snails from Pacific islands.

The island of New Guinea accounts for less than 1% of Earth’s land area, but it contains roughly 5% of the planet’s biodiversity and the largest intact rainforests in Australasia. Wildlife thrives within this large swath of undeveloped land, but Papua New Guinea’s old-growth forests are also highly desirable to loggers and are likely to become a conservation battleground in the future.

“These new species of snails were found in areas that still have native vegetation and still appear to be doing well, but they could easily become endangered if things change,” said John Slapcinsky, lead author of the paper and manager of the Florida Museum’s invertebrate zoology collection.

To reach Papua New Guinea's isolated forests, researchers had to travel on foot over steep mountains, sometimes using fallen trees to cross crevices that were more than 100 feet deep. There are few roads in the country, which historically posed a challenge to scientists interested in researching the region but has also shielded native plants and animals from human disturbance and habitat destruction.

Slapcinsky took nine trips to Papua New Guinea between 2002 and 2012, each time staying for at least a month to comb through the soil and fallen leaves. He ultimately collected more than 19,000 snails from over 200 sites.

Only 31% of the snail species he surveyed had been previously documented, a sign of Papua New Guinea’s high biodiversity and low levels of sampling. But the snails are also exceptionally hard to find because of their small size, pickiness about their habitats and limited distribution. Nearly all of them are restricted to a single island or mountain.

The newly named snails have tightly coiled, Frisbee-shaped shells in various shades of brown and tan, some with attractive gold or brown flamelike bands. One of the new species, Torresiropa paterivolans, was named for its resemblance to flying saucers (in Latin, “patera” means “saucer,” and “volans” means “flying”).

All nine species have dagger-shaped teeth on their radula, which is characteristic of predatory snails. Just what they’re eating, Slapcinsky said, is a mystery, since the snails did not eat anything under observation. Still, the shape of the teeth, combined with the fact that other species in the same family — Rhytididae — are predators, suggests that these newly discovered snails do eat meat.

There is not yet enough data to know the conservation status of the new species, but it is a promising sign that their habitat has not yet been dramatically altered by human activity.

Slapcinsky contrasted this with the Hawaiian Islands, where native snails are at imminent risk of extinction. He works with a team at the Bishop Museum in Honolulu that collaborates with the state and federal government on captive breeding programs for native snail colonies, many of which harbor the last members of their species. They also provide native snails for fenced-in areas, known as exclosures, where predators have been removed and the native forest has been replanted. These are expensive programs that Papua New Guinea still has the chance to avoid, Slapcinsky said, by slowing deforestation and preventing the introduction of non-native predators before it becomes a more serious problem.

Snails are highly vulnerable to habitat disturbances because they cannot easily travel long distances and are usually adapted only to the environment in their immediate vicinity. “When these habitats are threatened, snails are often out of luck, since they can’t go anywhere,” Slapcinsky said.

Many past discoveries of new snail species, especially on Pacific islands, have come after it was too late to save them. Scientists did not know that many snails lived on Easter Island, which was completely deforested centuries ago, until examining fossil deposits. But species on the island of New Guinea can still be saved if the forest is saved. The newly named snails provide a rare glimpse at an ecosystem that remains largely intact, and there are surely many similar discoveries yet to be made.

“We don’t know everything that’s out there,” Slapcinsky said. “Most people may not realize how poorly known most of the invertebrates are, even though 95 to 99% of all animals are invertebrates. You can go to a place, look around for a few months and find all sorts of things that haven’t been described before.”

Detailed photos of the snails, while beautiful, also serve a scientific purpose by providing documentation of the species.

CREDIT

Florida Museum photo by Jeff Gage

The country of Papua New Guinea includes the eastern half of the island of New Guinea and several offshore islands.

CREDIT

Florida Museum photo by John Slapcinsky

JOURNAL

Archiv für Molluskenkunde

DOI

10.1127/arch.moll/152/135-152

ARTICLE TITLE

Overlooked predatory snails from Papua New Guinea: nine new Torresiropa Solem, 1959 (Gastropoda: Stylommatophora: Rhytididae)

How fruit bats got a sweet tooth without sour health

Peer-Reviewed Publication

UNIVERSITY OF CALIFORNIA - SAN FRANCISCO

Levi Gadye,
Levi.Gadye@ucsf.edu | @UCSF

Video: https://ucsf.app.box.com/s/i3atd54ye4m1z1spi0qf59axq7tq7640

A high-sugar diet is bad news for humans, leading to diabetes, obesity and even cancer. Yet fruit bats survive and even thrive by eating up to twice their body weight in sugary fruit every day.

Now, UC San Francisco scientists have discovered how fruit bats may have evolved to consume so much sugar, with potential implications for the 37 million Americans with diabetes. The findings, published on Tuesday, Jan. 9, 2024 in Nature Communications, point to adaptations in the fruit bat body that prevent their sugar-rich diet from becoming harmful.

Diabetes is the eighth leading cause of death in the United States, according to the Centers for Disease Control and Prevention, and it’s responsible for $237 billion in direct medical costs each year.

“With diabetes, the human body can’t produce or detect insulin, leading to problems controlling blood sugar,” said Nadav Ahituv, PhD, director of the UCSF Institute for Human Genetics and co-senior author of the paper. “But fruit bats have a genetic system that controls blood sugar without fail. We’d like to learn from that system to make better insulin- or sugar-sensing therapies for people.”

Ahituv’s team focused on evolution in the bat pancreas, which controls blood sugar, and the kidneys. They found that the fruit bat pancreas, compared to the pancreas of an insect-eating bat, had extra insulin-producing cells as well as genetic changes to help it process an immense amount of sugar. And fruit bat kidneys had adapted to ensure that vital electrolytes would be retained from their watery meals.

“Even small changes, to single letters of DNA, make this diet viable for fruit bats,” said Wei Gordon, PhD, co-first author of the paper, a recent graduate of UCSF’s TETRAD program, and assistant professor of biology at Menlo College. “We need to understand high-sugar metabolism like this to make progress helping the one in three Americans who are prediabetic.”

A sweet tooth without consequences

Each day, after 20 hours of sleep, fruit bats wake up for four hours to gorge on fruit. Then it’s back to the roost.

To understand how a fruit bat pulls off this feat of sugar consumption, Ahituv and Gordon collaborated with scientists from a variety of institutions, ranging from Yonsei University in Korea to the American Museum of Natural History in New York City, to compare the Jamaican fruit bat to the big brown bat, which only eats insects.

The researchers analyzed gene expression (which genes were on or off) and regulatory DNA (the parts of DNA that control gene expression) using a method for measuring both in individual cells.

“This newer single-cell technology can explain not only which types of cells are in which organs, but also how those cells regulate gene expression to manage each diet,” Ahituv said.

In fruit bats, the compositions of the pancreas and kidneys evolved to accommodate their diet. The pancreas had more cells to produce insulin, which tells the body to lower blood sugar, as well as more cells to produce glucagon, the other major sugar-regulating hormone. The fruit bat kidneys, meanwhile, had more cells to trap scarce salts as they filter blood.

Zooming in, the regulatory DNA in those cells had evolved to turn the appropriate genes for fruit metabolism on or off. The big brown bat, on the other hand, had more cells for breaking down protein and conserving water. And the gene expression in those cells was tuned to handle a diet of bugs.

“The organization of the DNA around the insulin and glucagon genes was very clearly different between the two bat species,” Gordon said. “The DNA around genes used to be considered ‘junk,’ but our data shows that this regulatory DNA likely helps fruit bats react to sudden increases or decreases in blood sugar.”

While some of the biology of the fruit bat resembled what’s found in humans with diabetes, the fruit bat appeared to evolve something that humans with a sweet tooth could only dream of: a sweet tooth without consequences.

“It’s remarkable to step back from model organisms, like the laboratory mouse, and discover possible solutions for human health crises out in nature,” Gordon said. “Bats have figured it out, and it’s all in their DNA, the result of natural selection.”

Superheroes of evolution

The study benefited from a recent groundswell of interest in studying bats to better human health. Gordon and Ahituv traveled to Belize to participate in an annual Bat-a-Thon with nearly 50 other bat researchers, taking a census of wild bats as well as field samples for science. One of the Jamaican fruit bats captured at this event was used in the sugar metabolism study.

As one of the most diverse families of mammals, bats include many examples of evolutionary triumph, from their immune systems to their peculiar diets and beyond.

“For me, bats are like superheroes, each one with an amazing super power, whether it is echolocation, flying, blood sucking without coagulation, or eating fruit and not getting diabetes,” Ahituv said. “This kind of work is just the beginning.”

Key collaborators included co-first author Seungbyn Baek, PhD, from Yonsei University (South Korea); co-senior author Martin Hemberg, PhD, from Harvard Medical School; Tony Schountz, PhD, from Colorado State University; Lisa Noelle Cooper, PhD, from Northeast Ohio Medical University; Melissa R. Ingala, PhD, Fairleigh Dickinson University; and Nancy B. Simmons, PhD, American Museum of Natural History. Other UCSF authors are Hai P. Nguyen, PhD, Yien-Ming Kuo, PhD, Rachael Bradley, and Sarah L. Fong, PhD. For all authors see the paper.

About UCSF: The University of California, San Francisco (UCSF) is exclusively focused on the health sciences and is dedicated to promoting health worldwide through advanced biomedical research, graduate-level education in the life sciences and health professions, and excellence in patient care. UCSF Health, which serves as UCSF's primary academic medical center, includes top-ranked specialty hospitals and other clinical programs, and has affiliations throughout the Bay Area. UCSF School of Medicine also has a regional campus in Fresno. Learn more at https://ucsf.edu, or see our Fact Sheet.