Thai water bug offers insights into human heart disease

TALLAHASSEE, Fla., Oct. 3 (UPI) -- Scientists don't have many opportunities to experiment on a living, beating human heart, which makes studying heart muscle defects quite difficult.

To study heart disease, researchers must find muscles analogous to the human heart. These muscles don't necessary have to be found in the human body.

One of the more promising anatomical analogues lies inside Lethocerus indicus, a palm-sized species of water bug found in Thailand. The muscle that propels the wings of the Thai water bug beats rhythmically like the human heart.

Within this muscle is a tiny filament composed of chains of the protein myosin. The filament controls the contraction of the muscle. Just as important as contraction, however, is the relaxation of the muscle.

Researchers at Florida State University were able to produce 3D images of the filament molecules in a relaxed state -- a breakthrough.

"After you contract your bicep to see if your muscles look like Arnold Schwarzenegger's, you need this filament to assume its relaxed structure, so that after contraction your tricep muscle can re-extend your bicep," Kenneth Taylor, a professor of biological sciences at Florida State, said in a news release.

Even the slightest defects in myosin function can lead to a breakdown in the rhythm of the heart muscle. The latest imaging analysis allowed scientists to better understand how mutations affect proteins inside the heart-like muscle of the Thai water bug.

The new imagery -- detailed in the journal Science Advances -- reveals how myosin rods interact with other proteins, like actin filaments, to contract and relax the muscle.

"The image answers a whole lot of questions about myosin filaments that scientists have been wondering about for decades," Taylor explained. "Many of these cardiomyopathy mutations may be understandable in terms of flawed muscle relaxation."

Scientists haven't yet turned their breakthrough into a new treatment for cardiomyopathy, but researchers hope such a development is not far off. For now, scientists are concentrating on securing even higher resolution images of the muscle filament -- images that will reveal the behavior of amino acids inside the myosin rods and actin filaments.