We have read with much interest the article by Shults et al1 about the possible neuroprotective effect of coenzyme Q10 (CoQ10) in patients with Parkinson disease (PD). Although the study is of clinical importance, their results also influence theoretical questions related to the primary cause of PD.
The idea that a disorder of the mitochondrial respiratory chain is involved in PD stems from studies with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which induces a PD-like syndrome in humans and animals. The MPTP inhibits complex I, which normally transports electrons from nicotinamide adenine dinucleotide dehydrogenase to ubiquinone (CoQ10).2 The cessation of electron transport ultimately results in defective oxidative phosphorylation, adenosine triphosphate (ATP) depletion, and consequently cell death.2 In normal tissue, the electron transport by complex I can be enhanced with exogenous CoQ10.1,3
Horstink MWIM, van Engelen BG. The Effect of Coenzyme Q10 Therapy in Parkinson Disease Could Be Symptomatic. Arch Neurol. 2003;60(8):1170–1172. doi:10.1001/archneur.60.8.1170-a