Menthol has found a purpose beyond soothing a cough. Researchers have designed a genetic circuit that can be switched on by a drop in temperature — or by menthol, which imparts a cooling sensation.

Scientists are investigating genes as treatments for genetic diseases and other medical problems, but controlling those genes in the body is a challenge. Seeking a solution, Martin Fussenegger at the Basel campus of the Swiss Federal Institute of Technology Zurich and his colleagues developed a genetic circuit based on the human protein TRPM8, which reacts to cool temperatures.

In cells the team created, TRPM8 responds both to temperatures of 15–18 ºC and to the presence of menthol — a mint-flavoured ingredient of many cough drops and other remedies — by activating a second protein. That activation, in turn, triggers the production of a third protein of the researchers’ choice.

The team engineered a set of cells whose TRPM8-based circuitry stimulated production of the protein insulin, which controls blood sugar levels. After diabetic mice implanted with these cells had menthol applied to their skin, their blood sugar levels were lower than those of diabetic mice treated with menthol alone.