Bioavailability of Ubiquinone and Ubiquinol in Older Adults

Coenzyme Q10 (or CoQ10) is a marketed supplement in US even though it can be synthesized in the body via complicated biochemical pathways. It exists in both reduced and oxidized states, namely ubiquinol and ubiquinone, respectively. It is commonly present in all cell membranes. The main function of CoQ10 is to participate in energy production. Further, the reduced form of CoQ10, ubiquinol, is appreciated as an important lipophilic antioxidant to protect free radical induced damages to DNA, lipid, and proteins. Given that older adults have increased production of free radicals, suboptimal antioxidant defenses toward free radicals, and a decreased capability to replenish utilized CoQ10, CoQ10 supplementation can be one of feasible ways to increase CoQ10 status in order adults. Most supplements available for consumers are in the oxidized form. While the ubiquinol form is also available, whether the reduced form will be more effective to replenish CoQ10 status in older subjects remains to be explored. Thus, investigators aimed to examine whether ubiquinol will be more effectively absorbed in older adults with a low antioxidant defense status. To pursue this aim, investigators will conduct a double blind, randomized, crossover design trail with 5 study visits (1 screening visit and 4 study visits). Ten older men (\>55 y, BMI: 25-5 kg/m2) with a compromised antioxidant defenses will be recruited and complete the trial. Eligible subjects will be randomized to receive 200 mg/d ubiquinol or ubiquinone for 2 weeks with 2-week washout between crossover. Ubiquinol and ubiquinone in plasma and immune cells in blood will be assessed to reveal whether the reduced form, ubiquinol, is more absorbable than the oxidized form, ubiquinone in older adults.