A study ‘links’ diabetes and bats. The sugar levels in their blood “are the highest ever seen in nature. Levels that would be lethal or send a mammal into a coma, but not the bats. We are seeing a new feature that we didn’t know was possible.” Researcher Jasmin Camacho talks about her group’s discovery, illustrated in a work published in ‘Nature Ecology and Evolution’. Scientists from the US Stowers Institute for Medical Research wanted to get to the bottom of this record-breaking ability of bats, because discovering their secret could also have implications for humans.
Indeed, what was observed suggests that small winged mammals have developed strategies to survive, and even thrive, with this extreme characteristic of skyrocketing sugars. The authors hope that knowing more could help us better understand human diseases such as diabetes, and pave the way for strategies to better protect our health.
Humans must regulate their blood sugar levels to stay healthy and fuel their cells.. Too much sugar or too little can cause serious complications, and high levels in the blood are a hallmark of diabetes. Research offers a glimpse into evolution and bats.
Co-authors Camacho and Andrea Bernal-Rivera explain that 30 million years ago, Neotropical leaf-nosed bats lived only on insects. Since then, however, they have diversified into many species, also changing their ‘diet’. From insects, the different lineages have specialized in menus that range from fruit to nectar, meat and everything in between, even just blood.
The team traveled to the jungles of Central America, South America, and the Caribbean to conduct fieldwork over several years, performing glucose tolerance tests, measuring blood sugar concentrations in nearly 200 wild-caught bats from 29 different species, after a single administration of one of three types of sugars associated with insect, fruit, or nectar diets. “We looked at the different ways in which sugar is assimilated, absorbed, stored, and used in the body, and how this process is specialized due to different diets,” Bernal-Rivera explains.
“We hope to extend this understanding to other mammals, including humans,” Camacho adds. The mechanism for keeping blood sugar levels within a narrow, healthy range is called glucose homeostasis, which is typically regulated by the hormone insulin and is what goes wrong in diabetes. Different species of leaf-nosed bats show a spectrum of adaptations to glucose homeostasis, ranging from changes in gut anatomy to genetic alterations for proteins that transport sugar from the blood into cells.
“Fruit bats have fine-tuned their insulin signaling pathway to lower blood sugar,” Camacho says. “On the other end of the spectrum, nectar bats can tolerate high blood sugar levels, similar to those seen in people with unregulated diabetes. They’ve developed a different mechanism, and it doesn’t appear to be insulin-dependent.” While the exact way they handle glucose is still being studied, researchers have found potential clues to alternative metabolic strategies for glucose regulation. Bats on high-sugar diets have been observed to have longer guts and larger intestinal cells with larger surface areas to absorb nutrients from food, compared to bats on other diets. Additionally, nectar bats have continuous expression of a gene responsible for sugar transport, a trait also seen in a species of hummingbird.
“This study establishes extremely important assets for the field,” says Nadav Ahituv, a professor of bioengineering and genetics at the University of California, San Francisco. “It provides not only metabolic characteristics of different bat species with different diets, but also their gut morphology and candidate genomic regions and protein structural differences that could guide dietary adaptations. The datasets will fuel future research and could advance the development of novel therapies for a variety of metabolic diseases in humans.”
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