Regulation of ubiquinone metabolism

Interest in ubiquinone (UQ) has increased during recent years, mainly becau se of its antioxidant function and its use as a dietary supplement. However , our knowledge of the biosynthesis, catabolism, and regulation of this lip id in mammalian tissues is quite limited. UQ exhibits a high rate of turnov er in all tissues indicating that cells possess efficient metabolic pathway s for handling this compound and controlling its tissue levels. Besides rev iewing the generally accepted metabolic pathway, alternative synthetic mech anisms are described. The lack of data concerning catabolism and regulation of this compound is emphasized. Reasons for the rather limited uptake of d ietary UQ are discussed and alternative mechanisms for its beneficial effec ts on organ function are suggested. Since appropriate tissue uptake of diet ary UQ probably only occurs in deficient states, the definition of partial UQ deficiency and its consequences is urgently needed. The possibility of r aising tissue UQ levels by drug treatment or natural metabolites is raised as a choice of preference for the future. (C) 2000 Elsevier Science Inc.