Alzheimer's disease: brain desmosterol levels.

Desmosterol is a C27 sterol intermediate in cholesterol synthesis generated during the metabolic pathway that transforms lanosterol into cholesterol. It has become of particular interest in the pathogenesis of Alzheimer's disease (AD) because of the report that the activity of the gene coding for the enzyme DHCR24, which metabolizes desmosterol to cholesterol, is selectively reduced in the affected areas of the brain. Any change in the pattern of C27 sterol intermediates in cholesterol synthesis merits investigation with respect to the pathogenesis of AD, since neurosteroids such as progesterone can modulate the tissue levels. We therefore analyzed the C27 sterol composition using a metabolomics approach that preserves the proportion of the different sterol intermediates. In AD, the proportion of desmosterol was found to be less than that of age-matched controls. The findings do not directly support the focus on Seladin-1, although they could reflect different stages of a slowly progressive disease.