Pythons are known for their enormous appetites. In a single meal they can devour animals at least as big as they are-deer, alligators, pigs, household pets. Equally remarkable is what happens inside the python as it digests its prey. Within a day, its internal organs can double in size. Metabolic rate and production of insulin and lipids soar. Then, like an accordion, the python's organs return to normal size in just a few days. Metabolism slows. Then the snake can fast for months, even a year, without losing muscle mass or showing any ill effects, ready to ambush new prey.
How this process happens so rapidly is a biological mystery with important implications for human health, particularly when it comes to heart failure. Now scientists at the University of Colorado are reporting that they have partly solved it. In a paper in the current issue of Science, they report that a gorging python expands its heart by enlarging existing cells-a process called hypertrophy-and not by creating new ones. (It is not known whether snakes get heart disease.) Hypertrophy of the human heart occurs in two types. One, from ailments like high blood pressure and heart attacks, is a leading predictor of death. The second type is beneficial and occurs from exercise in conditioned athletes.
The Colorado scientists found that the enlargement of a python's heart is analogous to the growth seen in the heart of a human athlete. Among their goals is to better understand how plasma components instruct individual cells to develop into the beneficial ones among athletes or bad ones in disease. A second finding is that a specific combination of three fatty acids produces enlargement of a python's heart, intestines, liver and kidneys. Injections of the combination produce similar growth in the heart of a mouse. Understanding such exaggerated variations, the researchers say, could help them develop novel ways to delay, prevent, treat or even reverse various hereditary and acquired human diseases.
"Heart failure is the goal" of the python research, said Leslie A Leinwand, a Howard Hughes Medical Institute professor at the University of Colorado and a senior member of the research team. She added that the findings might also lead to treatments to prevent sudden death in young athletes, as well as ailments like diabetes, high blood pressure and obesity. The python research in Boulder began in 2005, when Cecilia A Riquelme, who had earned a PhD in cell biology in her native Chile, sought a fellowship in Dr Leinwand's laboratory. An expert in the molecular workings of the heart, Dr Leinwand knew little such research had been done on pythons. There are structural differences-a python heart has three chambers, a human heart four. Yet she thought experiments in comparative biology might advance human heart research.
So she bought a supply of five-foot pythons and asked Dr Riquelme, "How would you feel about working with pythons?" Pythons are not venomous; still, she feared being bitten. But the challenge was too tempting to pass up, and after a harmless bite she overcame her fear. After a year, Dr Riquelme determined that she could enlarge the heart of a starved python by injecting blood from a feasting one. She then proposed adding the blood's straw-coloured plasma to rat heart cells to determine whether it had the same effect. Dr Leinwand doubted the experiment would work. But it did, repeatedly, and Dr Riquelme said her colleague "jumped up and down" with excitement. Dr Leinwand called it "the critical finding that motivated us to translate the python biology into mammals."
New York Times
