Python heart holds surprises that could be of use in cardiology

By Dr. Ananya Mandal, MDOct 30 2011

The expanding hearts of pythons have intrigued researchers. Leslie Leinwand - a University of Colorado at Boulder molecular biologist who studies heart disease in humans called pythons’ expanding hearts “amazing biology”. “They're not swelling up. They're building (heart) muscle,” he said.

Reptile biologists have studied these snakes, especially the huge Burmese pythons that can go nearly a year between meals. When these snakes swallow that next rat or bird - or in some cases deer their metabolism hitches up more than 40-fold, and their organs immediately expand. The heart grows a startling 40 percent or more within three days.

Leinwand saw implications for humans in this. An enlarged human heart is typically caused by chronic high blood pressure or other ailments that leave it flabby and unable to pump well. But months and years of vigorous exercise give some highly conditioned athletes unusually large, muscular hearts similar in some respects to expanded python hearts.

So Leinwand's team ordered some pythons and began testing their hearts. A digesting python's blood gets so full of fat it looks milky. A type of fat called triglycerides increased 50-fold within a day. In people, high triglyceride levels are dangerous. But the python heart was burning fat so rapidly that it did not affect the arteries at all. A key enzyme that protects the heart from damage rose in python blood right after it ate, while a heart-damaging compound was repressed.

Then the team found that a combination of three fatty acids in the blood helped promote healthy heart growth. The hearts of fasting pythons injected with the mixture grew the same way that a fed python's does they found.

After a year, Dr. Cecilia Riquelme determined that she could enlarge the heart of a starved python by injecting blood from a feasting one. She dropped plasma from a fed python into a lab dish containing the rat heart cells - and they grew bigger, too. Sure enough, injecting living mice made their hearts grow in an apparently healthy way as well. They want to know how the python heart shrinks back to its original size when digestion's done.

The experiments are “very, very cool indeed,” said James Hicks, a University of California, Irvine, biologist who has long studied pythons' extreme metabolism and wants to see more such comparisons. If the same underlying heart signals work in animals as divergent as snakes and mice, “this may reveal a common universal mechanism that can be used for improving cardiac function in all vertebrates, including humans,” Hicks said. “Only further studies and time will tell, but this paper is very exciting.”

The study was funded by the National Institutes of Health and a Boulder biotechnology company that Leinwand co-founded, Hiberna Corp., that aims to develop drugs based on extreme animal biology. The study was published in the latest issue of the journal Science.