Rousettus aegyptiacus (Egyptian fruit bat) photographed at Amazonia Strathclyde Country Park in Glasgow. Credit: Eggybird
Every day, after 20 hours of sleep, fruit bats wake up for four hours, eat up to twice their body weight in sugary fruit, then head back to the roost for more sleep. The most amazing part is they do this without negative consequences for their body.
Over the years, fruit bats have evolved to prevent their sugar-rich diet from becoming harmful. Rather, it’s imperative to their health.
Now, UC San Francisco scientists have discovered just how this evolution occurred, with potential implications for the 37 million Americans with diabetes.
In a study published in Nature Communications, the research team compared the Jamaican fruit bat to the big brown bat, which only eats insects. Using new single-cell technology, they analyzed gene expression and regulatory DNA.
As suspected, the fruit bats’ pancreas and kidneys evolved to accommodate their high-sugar diet. Specifically, the researchers found that 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 bats’ kidneys also had more cells to trap scarce salts, as they filter blood. The DNA of the cells had evolved to turn the appropriate genes for fruit metabolism on or off.
On the other hand, the study results showed that the big brown bat had more cells for breaking down protein and conserving water. The gene expression in these 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,” said Wei Gordon, co-first author of the paper, a recent graduate of UCSF and current assistant professor of biology at Menlo College. “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 resembles what’s found in humans with diabetes, ultimately, the cell evolution of the pancreas and kidneys gives fruit bats something humans can only dream of: a sweet tooth without consequences.
“Even small changes, to single letters of DNA, make this diet viable for fruit bats,” said Gordon. “We need to understand high-sugar metabolism like this to make progress helping the one in three Americans who are prediabetic.”
As one of the most diverse families of mammals, bats are an interesting scientific target. They include many examples of evolutionary triumph, from their immune systems to their diets and beyond.
Nadav Ahituv, co-senior author of the paper and director of the UCSF Institute for Human Genetics, said he believes scientists can learn from bats evolved genetic system in order to make better insulin- or sugar-sensing therapies for diabetic and pre-diabetic people.
“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,” said Ahituv. “This kind of work is just the beginning.”
Gordon agrees.
“It’s remarkable to step back from model organisms, like the laboratory mouse, and discover possible solutions for human health crises out in nature,” the researcher concludes. “Bats have figured it out, and it’s all in their DNA—the result of natural selection.”