The elixir of life from creatures of night

Natasha Khan / Bloomberg News /

Published Aug 27, 2013 at 05:00AM

Bats have long been associated with nightmarish connotations — Count Dracula being just one example — but the winged mammals are getting a new and more positive take from researchers, who believe the animal’s DNA holds the key to how to battle aging, diseases and cancer.

HONG KONG — Count Dracula was onto something.

Bats.

The immortal Prince of Darkness has been associated with the flying mammals since he first flitted through Bram Stoker’s 1897 novel. Now, scientists seek to unlock another trait the vampire shares with bats: the secret of longevity.

The volume of published scientific research on bat viruses has doubled in the past decade with the discovery that they’re probably a natural reservoir for global killers such as Ebola, severe acute respiratory syndrome and the Middle East respiratory syndrome. Along the way, scientists have been startled by how well they respond to the genetic wear and tear that’s a feature of life, aging and diseases such as cancer.

“The most outstanding difference we’ve seen between bats and other mammals has to do with DNA repair,” said Linfa Wang, 53, director of the emerging infectious disease program at the Duke-NUS graduate medical school in Singapore. “If the science is as true as we think it is, we can unlock the mechanisms and it can have a huge, huge impact.”

Wang, dubbed by some colleagues the “Bat Man,” was awarded a grant in April from the National Research Foundation of Singapore and is hiring a team of 10 researchers to study the animals’ genomics.

How some species can live three times longer than other mammals their size may be linked to their ability to carry viruses that are deadly to other animals, as well as their low rates of cancer, he said.

It’s a positive spin for a group of mammals that’s suffered from negative connotations in Western culture for centuries: from bat-winged demons in medieval Christian imagery to a modern association with rabies and other viruses.

Since their ancestors first took flight more than 50 million years ago, bats have spread across all continents and into every habitat bar the polar extremes. They’ve evolved into more than 1,100 species, from the bumblebee-sized Kitti’s hog-nosed bat, the world’s smallest mammal, to fruit-eating flying foxes with six-foot (1.8 meter) wingspans.

Wang’s research will focus on the black flying fox, Pteropus alecto.

The ability to fly means bats can spread zoonoses — diseases that transmit from vertebrate animals to humans — across the globe.

It’s that feature that first drew researchers at Australia’s Commonwealth Scientific and Industrial Research Organization to bat viruses almost two decades ago.

In September 1994, Queensland horse trainer Vic Rail, a stablehand, and most of his animals fell ill. Within days, Rail and 14 horses were dead. Around the same time, there was another outbreak about 500 miles away.

Researchers began testing wild animals in search of a likely source. They found antibodies for the newly discovered Hendra virus in fruit bats.

Wang took over the Hendra research two years later, and now has a team of 25 scientists researching the potential threat from bat-borne viruses. Wang is still chief executive science leader at the Geelong-based animal-health laboratory.

About 60 percent of new infectious diseases affecting humans are zoonotic, according to the United Nations’ Food and Agricultural Organization.

Such viruses have probably been in bats “forever,” said Brisbane-based veterinary epidemiologist Hume Field, who worked closely with Wang’s team. Bats are starting to have a bigger impact on humans due to the destruction of their habitats. “Their food resources have got to be less reliable, so they’ve become urban creatures,” he said.

Viruses typically transmit from bats to humans through another mammal that is either genetically closer or has more opportunities for exposure, as was the probable case with the civet cat and SARS.

When the World Health Organization assembled a team to investigate SARS toward the end of the outbreak in 2003, Wang was recruited. He suggested bats might be involved. A few years later, they were found to harbor a coronavirus similar to SARS, bringing a flurry of converts and new research.

“My interest with bats started with SARS,” University of Hong Kong microbiologist K.Y. Yuen said in his basement office at Hong Kong’s Queen Mary hospital complex as he sketched out links between bats and different viruses on a whiteboard. “If we have another virus jumping into humans, bats should immediately be considered.”

Flight may make bats a threat. It may also be their biggest gift. As people globally live longer lives, diseases related to aging and cell damage, such as cancer and Alzheimer’s, are a growing scourge. There were almost 810 million people older than 60 on the planet in 2012, up from 205 million in 1950, according to the United Nations.

Metabolic activity and environmental factors cause damage to DNA in humans. Wang said that newborn babies have almost homogeneously healthy cells, while a 70-year-old may have damage in 90 percent of his mitochondria — structures inside cells that produce energy.

Bats’ cells are adapted to survive surges in metabolism — their hearts can go from 10 beats per minute during hibernation to 1,000 beats in flight. A similar change in humans would create a lethal shortage of oxygen and oversupply of toxic by-products of the metabolic process that damage DNA.

“So everything is interlinked,” Wang said. “Bats’ ability to do better with DNA damage repair, live longer, have less cancer, carry viruses without disease — we think this is all a different display of the same thing.”