Transferrin, insulin, and progesterone modulate intracellular concentrations of coenzyme Q and cholesterol, products of the mevalonate pathway, in undifferentiated PC12 cells

Coenzyme Q (CoQ) is important not only as an essential lipid for the mitochondrial electron transport system, but also as an antioxidant. CoQ levels decrease during aging and in various diseases. Orally administered CoQ is not readily taken up in the brain, so it is necessary to develop a method to increase the amount of CoQ in neurons. CoQ is synthesized via mevalonate pathway, like cholesterol. Transferrin, insulin, and progesterone are factors used in the culture of neurons. In this study, we determined the effect of these reagents on cellular CoQ and cholesterol levels. The administration of transferrin, insulin, and progesterone increased cellular CoQ levels in undifferentiated PC12 cells. When serum was removed and only insulin was administered, intracellular CoQ levels increased. This increase was even more pronounced with concurrent administration of transferrin, insulin, and progesterone. Cholesterol level decreased by the administration of transferrin, insulin, and progesterone. Progesterone treatment lowered intracellular cholesterol levels in a concentration-dependent manner. Our findings suggest that transferrin, insulin, and progesterone may be useful in regulating CoQ levels and cholesterol levels, which are products of the mevalonate pathway.