Blood-Brain Barrier and Neuronal Model Systems for Studying CoQ₁₀ Metabolism

The disparity in outcomes between preclinical and clinical studies supplementing coenzyme Q10 (CoQ10) in neurological disorders may be a reflection of the differences in the ability of supplemental CoQ10 to access the blood-brain barrier (BBB) in rodents and in humans, which is, in turn, a consequence of contrasting structures of the BBB. The applicability of in vivo animal models to study access of CoQ10 across the BBB and subsequent neuronal metabolism has, therefore, been questioned, and there is an argument, perhaps surprisingly, that in vitro model systems (particularly 3D cellular systems) may be more appropriate. In this article, we have, therefore, reviewed the role of model systems to study the access of CoQ10 across the BBB, as well as the role of such systems in studying the role of CoQ10 in aspects of neuronal metabolism, such as mitochondrial and lysosomal function. In addition, the use of such model systems to study the interactions of CoQ10 with vitamin E and selenium has been reviewed. Finally, the practical application of a neuronal model system to investigate the effect of CoQ10 supplementation on CoQ10 status and mitochondrial metabolism in a CoQ10 deficiency state has been described.