Able to stretch as long as a telephone pole and swallow an antelope or alligator whole, a python is a marvel of nature. Consider how it feeds:
In the first 24 hours after devouring its massive prey, its heart grows 25%, its cardiac tissue softens dramatically, and the organ squeezes harder and harder to more than double its pulse. Meanwhile, a vast collection of specialized genes kicks into action to help boost the snake's metabolism fortyfold. Two weeks later, after its feast has been digested, all systems return to normal-its heart remaining just slightly larger, and even stronger, than before.
This extraordinary process, described by CU Boulder researchers this week in the journal PNAS, could ultimately inspire novel treatments for a common human heart condition called cardiac fibrosis, in which heart tissue stiffens, as well as a host of other modern-day ailments that the monstrous snakes seem to miraculously resist.
"Pythons can go months or even a year in the wild without eating and then consume something greater than their own body mass, yet nothing bad happens to them," said senior author Leslie Leinwand, professor of molecular, cellular and developmental biology at CU Boulder and chief scientific officer of the BioFrontiers Institute. "We believe they possess mechanisms that protect their hearts from things that would be harmful to humans. This study goes a long way toward mapping out what those are."
What pythons and athletes have in common
Leinwand first started studying pythons nearly two decades ago, and her lab remains one of the few in the world looking to the constricting, non-venomous reptiles for clues to improve human health.
As much as 20 feet long, depending on the species, pythons are typically found in resource-scarce regions of Africa, South Asia and Australia. They fast for extended periods but when they do eat, they eat alot.
"Most people who use animal models to study disease and health typically focus on rats and mice, but there is a lot to learn from animals like pythons that have evolved ways to survive in extreme environments," said Leinwand, whose students drive to Oklahoma each year to purchase baby snakes from a breeder and raise them to adulthood in the Boulder lab.
There are two kinds of heart growth in humans, explains Leinwand: Healthy, like the kind that comes with chronic endurance exercise, and unhealthy, like the kind that comes with disease.
Pythons, much like elite athletes, excel at healthy heart growth.
Her previous work has shown that over the course of about a week to 10 days after a meal, python hearts get much bigger, their heart rate doubles, and their bloodstream turns milky white with circulating fats which, surprisingly, nourish rather than harm their heart tissue.
The new study set out to explore how this all happens.
Researchers fed pythons who had fasted for 28 days a meal of 25% of their body weight and compared them to snakes who had not been fed.
They discovered that as the well-fed snakes' hearts grew, specialized bundles of cardiac muscle called myofibrils- that help the heart expand and contract- radically softened and contracted with roughly 50% greater force. Meanwhile, those same snakes had different metabolites in their blood and "profound epigenetic differences," differences in which genes were turned on or off, than the fasting snakes.
Leslie Leinwand in the Leinwand Lab with a python in 2011. Leinwand began studying pythons nearly 20 years ago and her lab remains one of only a few in the world who do so. Credit: Casey Cass/CU Boulder.
"It's fascinating how pythons can modify their metabolism and contraction force, which is particularly relevant given the prevalence of cardiac metabolic disorders in humans," said first author Claudia Crocini, a former postdoctoral researcher in Leinwand's lab and now group leader at the German Heart Center Charite' (DHZC) in Berlin, Germany.
Toward novel treatments for metabolic disease
More research is necessary to identify precisely which genes and metabolites are at play and what they do, but the study suggests that some may nudge the python heart to burn fat instead of sugar for fuel. Notably, diseased hearts struggle to do this.
"We found that the python heart is basically able to radically remodel itself, becoming much less stiff and much more energy efficient, in just 24 hours," said Leinwand. "If we can map out how the python does this and harness it to use therapeutically in people it would be extraordinary."
Stiff or fibrotic tissue drives disease in other organs beside the heart, including lungs and livers, so there could be applications there, too, said Leinwand, whose previous discoveries have helped lead to multiple blockbuster drugs for heart disease.
Leinwand notes that pythons in the Florida Everglades, unlike their counterparts in other areas of the world, have an endless supply of food and take advantage of it. Yet they still manage to remain physically and metabolically healthy. They may hold clues for preventing or reversing metabolic syndrome and other obesity-related diseases.
Her lab is exploring this too.
"The fact that they can eat endlessly with really no negative health consequences makes them a great candidate to study," she said.
