24-dehydro Cholesterol is an immediate precursor to cholesterol in the Bloch pathway of cholesterol biosynthesis. Structurally, it varies from cholesterol only by a single double bond at carbon 24 and has been used as cholesterol substitute in cellular membrane studies. During brain development, 24-dehydro cholesterol transiently accumulates, composing up to 30% of total brain sterol, where it is poised to rapidly enrich membrane sterols. However, defects in cholesterol synthesis can lead to a condition called, desmosterolosis, which results in an accumulation of excess 24-dehydro cholesterol. 24-dehydro Cholesterol has been reported to activate liver X receptor-target genes in both the liver of cholesterol-free mice and in cholesterol-starved macrophage foam cells in atherosclerotic lesions.
