Figure 4.

Cholesterol synthesis occurs through diverging pathways for different neuronal cell types. Cholesterol synthesis acts through the mevalonate pathway. Acetyl CoA is converted to 3-hydroxy-3-methylglutaryl CoA (HMG-CoA). HMG CoA is then converted to mevalonate via HMG-CoA reductase, and this is the rate limiting step in cholesterol synthesis. Via a complex series of reactions that involve multiple enzymes and reaction steps, mevalonate is converted to squalene. Squalene is converted to lanosterol in an essential cyclization process. From here, the Kandutsch-Russel pathway, which is favored by neuronal cells, produces cholesterol from lanosterol, while the Bloch pathway synthesizes cholesterol that is favored by glial cells. After cholesterol is synthesized, it can be further metabolized into vitamin D, steroid hormones, or bile acids, or it may be incorporated into cellular membranes.