Fruit bats – who survive and even thrive by eating up to twice their body weight in sugary fruit daily – may hold the key to curing diabetes, according to a new landmark study.
While a high-sugar diet leads to a host of health complications for humans, including diabetes, obesity and even cancer, fruit bats are like ‘superheroes’ that can consume a vast amount of sugar that is potentially so deadly to humans.
Now, researchers from the University of California-San Francisco (UCSF) are investigating how these bats have evolved to cope with such high sugar intake - and whether this ability can help humans with diabetes.
The most recent figures from the World Health Organization (WHO) estimate that 422 million people worldwide have diabetes. The international health body says an estimated 1.5 million deaths are directly linked to the preventable disease each year.
“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,” says Nadav Ahituv, PhD, director of the UCSF Institute for Human Genetics and co-senior author of the paper, in a university release.
Regional, global diabetes prevalence
It is estimated there are as many as one in five people in the UAE with diabetes, according to the figures from Cleveland Clinic Abu Dhabi, a number predicted to double by the year 2040.
In Saudi Arabia, the International Diabetes Federation (IDF) Atlas predicts more than 4.2 million people are living with diabetes – a number expected to grow to 5.6 million by 2030 and more than 7.5 million by 2045.
Globally, the IDF says 537 million adults (20-79 years) are living with diabetes - 1 in 10. This number is predicted to rise to 643 million by 2030 and 783 million by 2045. In 2021, diabetes was responsible for 6.7 million - or one every five seconds.
Diabetes can lead to a host of health complications, including kidney failure, heart attack, blindness, stroke and limb amputation.
With diabetes, the human body can’t produce or detect insulin, leading to problems controlling blood sugar,” said Ahituv. “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. 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.”
After 20 hours of sleep each day, fruit bats wake up for four hours to gorge on fruit. Then it’s back to the roost.
Researchers at work
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 has 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. 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.”
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.