Fatty liver disease (steatotic liver disease, SLD for short) is increasingly causing failure of the liver as a vital organ. A team led by researchers has now discovered that a saturated fatty acid in blood vessels leads to the production of the signalling molecule SEMA3A, which closes the ‘windows’ in the blood vessels. This hinders the transport of fat from the liver to the adipose tissue. The researchers report that the windows open again and the fat in the liver is reduced when SEMA3A is inhibited.