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. Author manuscript; available in PMC: 2010 Mar 12.
Published in final edited form as: Annu Rev Biochem. 2009;78:1017–1040. doi: 10.1146/annurev.biochem.78.072407.103859

Figure 1.

Figure 1

Cholesterol metabolism in the brain. (a) An abbreviated cholesterol biosynthetic pathway is shown in which key intermediates and enzymes are highlighted. Statins reduce the flow of intermediates through the biosynthetic pathway by inhibiting 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase. Farnesyl diphosphate (farnesyl-PP) and geranylgeranyl diphosphate are polyisoprenoid end products of the pathway. Knockout of the cholesterol 24-hydroxylase gene causes cholesterol accumulation and activation of a negative feedback pathway that suppresses the reductase enzyme as well as others in the pathway and subsequently decreases cholesterol synthesis. Redrawn from Reference 79. (b) Cholesterol synthesis and accumulation in mouse brain as a function of age of the animal.