The liver may hold an unexpected key to fighting two of the most serious diseases associated with aging: Alzheimer's disease and heart disease. Scientists have discovered that restoring the function of aging liver cells can dramatically reduce harmful substances in the bloodstream, raising the possibility of treating diseases that affect organs far beyond the liver itself.

In a new study involving older rats, researchers at the Keck School of Medicine of USC found that an experimental drug called cinaciguat reversed important signs of aging in specialized liver cells. After just two weeks of treatment, levels of amyloid beta, a protein associated with Alzheimer's disease, dropped by half. Levels of LDL, commonly called bad cholesterol, also returned to those seen in younger animals.

The findings, published in the Journal of Biological Chemistry , also revealed a previously unknown way that liver cells communicate with one another.…