A specific mixture of fatty acids circulating in the blood of pythons is responsible for an increase in the size of the animals’ hearts after feeding, according to a new report (Science, DOI: 10.1126/science.1210558). The identification of these molecules, which trigger pythons’ heart cells to expand so that the snakes can metabolize big meals, could lead to future therapies for heart disease in humans.
Although they sometimes fast for long periods between meals, when Burmese pythons feed, they can swallow prey as large as a deer. To accommodate such feasts, the snakes’ metabolic rates skyrocket, and their hearts grow in mass by as much as 40% within two to three days after feeding.
A team of researchers led by Leslie A. Leinwand of the University of Colorado, Boulder, took a closer look at the composition of the snakes’ blood plasma before and after feeding to understand this extreme physiology. The scientists saw a significant increase in triglycerides and fatty acids post meal that made the pythons’ blood appear “milky,” Leinwand says.
Using gas chromatography, the team identified the main components responsible for signaling the snakes’ heart growth: myristic, palmitic, and palmitoleic acids. When added to cultured rat heart cells or injected into mice, this mixture caused the same enlargement elicited by the plasma of fed pythons. The researchers also administered the fatty acids to fasting pythons and observed heart growth similar to that in fed snakes.
Heart growth in humans can be both good and bad, Leinwand says. For well-trained athletes, heart muscle walls and chambers grow proportionally, leading to increased metabolic efficiency. Understanding the molecular mechanisms behind healthy heart growth in pythons could help cardiac disease patients who have small heart chambers and thick heart muscle walls.
These results are fascinating and newsworthy, says Marc van Bilsen, a cardiac physiologist at Maastricht University, in the Netherlands, because the researchers show that saturated and monounsaturated fatty acids—traditionally considered as “bad guys” or merely as energy-providing substrates for the heart—have important roles in cellular signaling.