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How fruit bats suffer no consequences from their high sugar diet

In a fascinating twist of nature, fruit bats not only survive but thrive on a high-sugar diet that consists predominantly of sugary fruits, consuming up to twice their body weight daily.

It’s a well-established fact that high-sugar diets are detrimental to human health, leading to conditions like diabetes, obesity, and even cancer. So the question remains…why don’t fruit bats suffer the same consequences?

Studying fruit bats and their sugar diet

Scientists at UC San Francisco have delved into this mystery, uncovering how fruit bats may have evolved to tolerate such high sugar levels.

Their findings reveal adaptations in fruit bats that prevent their sugar-rich diet from causing harm, unlike in humans.

This research could hold potential implications for the 37 million Americans suffering from diabetes, a disease that ranks as the eighth leading cause of death in the United States.

Diabetes: A growing global concern

Costing $237 billion in direct medical expenses annually, diabetes is a condition where the human body either fails to produce insulin or cannot effectively use it, leading to uncontrolled blood sugar levels.

“With diabetes, the human body can’t produce or detect insulin, leading to problems controlling blood sugar,” explains Nadav Ahituv, PhD, director of the UCSF Institute for Human Genetics and co-senior author of the study.

“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.”

Focusing on bat physiology

Ahituv’s team concentrated on evolutionary changes in the bat pancreas and kidneys. They discovered that the pancreas of a fruit bat, in comparison to that of an insect-eating bat, contains additional insulin-producing cells and genetic modifications to process large amounts of sugar.

Moreover, the fruit bat’s kidneys have adapted to retain essential electrolytes from their watery, fruit-based 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 sugary day in the life of a fruit bat

Interestingly, fruit bats spend 20 hours a day sleeping, waking up for a mere four hours to feast on fruit before returning to their roost.

To comprehend how fruit bats manage this high sugar intake, Ahituv and Gordon collaborated with scientists from various institutions, including Yonsei University in Korea and the American Museum of Natural History in New York City.

They compared the Jamaican fruit bat to the big brown bat, which primarily consumes insects.

By employing single-cell technology, the researchers could not only identify which types of cells were present in different organs but also understand how these cells regulate gene expression in accordance with each diet.

In fruit bats, the pancreas and kidneys have evolved to support their diet. The pancreas boasts more cells for insulin and glucagon production, while the kidneys efficiently trap salts during blood filtration.

Zooming into the cellular level, regulatory DNA in these cells has evolved to switch appropriate genes on or off, depending on the dietary needs. This contrasts with the big brown bat, which has adapted to a diet of insects.

“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.” 

Implications for human health

Some aspects of the fruit bat’s biology resemble human diabetic conditions, but with a significant advantage — they maintain a sweet tooth without the associated health 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.” 

This study benefits from a growing interest in bat research, particularly in understanding how their unique traits can enhance human health.

Gordon and Ahituv’s participation in an annual Bat-a-Thon in Belize, involving a census of wild bats, exemplifies this interest.

A Jamaican fruit bat captured during this event played a key role in the sugar metabolism study.

Bats, being one of the most diverse mammalian families, offer numerous examples of evolutionary success, whether it’s their immune systems, peculiar diets, or other unique abilities.

Beginning of a new frontier

In summary, UC San Francisco scientists have uncovered how fruit bats can consume extremely high-sugar diets without adverse effects, unlike humans who risk diabetes and obesity from such diets.

This research reveals that fruit bats have evolved specific adaptations in their pancreas and kidneys to process and tolerate large amounts of sugar.

Led by Nadav Ahituv, PhD, and Wei Gordon, PhD, the team’s findings, derived from comparisons between fruit bats and insect-eating bats, offer insights that could aid in developing new treatments for the 37 million Americans with diabetes.

“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.”

The study highlights the potential of learning from wildlife to address human health challenges, marking a significant step in understanding and potentially managing high-sugar metabolism in humans.

The full study was published in the journal Nature Communications.


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