Diabetes is a condition in which the body produces too little or no insulin. Diabetics thus depend on an external supply of this hormone via injection or pump. Researchers led by Martin Fussenegger from the Department of Biosystems Science and Engineering at ETH Zurich in Basel, Switzerland want to make the lives of these people easier and are looking for solutions to produce and administer insulin directly in the body.
One such solution the scientists are pursuing is enclosing insulin-producing designer cells in capsules that can be implanted in the body. To be able to control from the outside when and how much insulin the cells release into the blood, researchers have studied and applied different triggers in recent years: light, temperature and electric fields.
Fussenegger and his colleagues have now developed another, novel stimulation method: they use music to trigger the cells to release insulin within minutes. This works especially well with “We Will Rock You,” a global hit by British rock band, Queen.
Equipping cells to receive sound waves
To make the insulin-producing cells receptive to sound waves, the researchers used a protein from the bacterium E. coli. Such proteins respond to mechanical stimuli and are common in animals and bacteria. The protein is located in the membrane of the bacterium and regulates the influx of calcium ions into the cell interior. The researchers have incorporated the blueprint of this bacterial ion channel into human insulin-producing cells. This lets these cells create the ion channel themselves and embed it in their membrane.
As the scientists have been able to show, the channel in these cells opens in response to sound, allowing positively charged calcium ions to flow into the cell. This leads to a charge reversal in the cell membrane, which in turn causes the tiny insulin-filled vesicles inside the cell to fuse with the cell membrane and release the insulin to the outside.
Booming bass boosts insulin secretion
In cell cultures, the researchers first determined which frequencies and volume levels activated the ion channels most strongly. They found that volume levels around 60 decibels (dB) and bass frequencies of 50 hertz were the most effective in triggering the ion channels. To trigger maximum insulin release, the sound or the music had to continue for a minimum of three seconds and pause for a maximum of five seconds. If the intervals were too far apart, substantially less insulin was released.
Finally, the researchers looked into which music genres caused the strongest insulin response at a volume of 85 dB. Rock music with booming bass like the song from Queen, “We Will Rock You” came out on top, followed by the soundtrack to the action movie The Avengers. The insulin response to classical music and guitar music was rather weak by comparison.
