In the fat around the heart and blood vessels of heart failure patients, the MAO-A enzyme is much more common than the MAO-B enzyme.

In the fat around the heart and blood vessels of heart failure patients, a specific enzyme called MAO-A is much more common and makes more harmful chemicals than its cousin MAO-B.

When fat tissue around the heart and blood vessels from heart failure patients was soaked in a small amount of methylene blue for a day, the levels of a specific enzyme (MAO-A) that makes harmful molecules went down.

When fat tissue around the heart and blood vessels was soaked in a blue dye called methylene blue for a day in the lab, it made less of a harmful enzyme and produced fewer damaging chemicals, which might help explain how the dye could protect cells.