Prolonged oral coenzyme Q10-β-cyclodextrin supplementation increases plasma CoQ10concentration and skeletal muscle complex I+III activity in young, untrained healthy Thoroughbreds

Coenzyme Q 10 (CoQ 10 ) is an essential component of the mitochondrial electron transport chain (ETC). Decreased skeletal muscle CoQ 10 content may result in decreased ETC activity and energy production. This study aimed to test the hypothesis that prolonged supplementation with oral CoQ 10 will increase plasma CoQ 10 concentrations and skeletal muscle CoQ 10 content in young, healthy untrained Thoroughbreds. Nineteen Thoroughbreds (27.5±9.7 months old; 11 males, 8 females) from one farm and maintained on a grass pasture with one grain meal per day were supplemented orally once per day for 9 weeks with 1.5 mg/kg body weight of a CoQ 10 -β-cyclodextrin inclusion complex. Whole-blood and skeletal muscle biopsies were collected before (T 0 ) and after (T 1 ) 9 weeks of supplementation. Plasma CoQ 10 concentrations were determined via high-performance liquid chromatography. Skeletal muscle mitochondrial ETC combined complex I+III enzyme activity (an indirect measurement of CoQ 10 content) was assessed spectrophotometrically and normalised to mitochondrial abundance. Results were analysed using a paired two-tailed Students t -test with P ≤0.05 significant. Horses accepted supplementation with no adverse effects. The mean change in plasma CoQ 10 concentration from T 0 to T 1 was significantly greater than zero (0.13±0.02 vs . 0.25±0.03 µg/ml, mean difference 0.12±0.03; P =0.004), although variability in absorbance resulted in only a 58% response rate. The mean change in skeletal muscle complex I+III activity from T 0 to T 1 was significantly greater than zero (0.36±0.04 vs . 0.59±0.05 pmol/min/mg of muscle, mean difference 0.23±0.05; P =0.0004), although T 1 values for 3/19 horses decreased on average by 23% below T 0 values. In conclusion, prolonged oral supplementation of the diet of young, healthy untrained Thoroughbreds with CoQ 10 increased mean plasma CoQ 10 concentration by 99% and mean skeletal muscle complex I+III activity by 65% with variability in absorbance among horses. Additional research is warranted investigating training and exercise effects on skeletal muscle CoQ 10 content in CoQ 10 supplemented and un-supplemented Thoroughbreds.