Affiliations: Vestische Kinderklinik Datteln, University
Witten-Herdecke, Datteln, Germany
Note: [] Address for correspondence: Dr. Petra Niklowitz, Vestische
Kinderklinik Datteln, University Witten-Herdecke, Dr.-Friedrich-Steiner-Str. 5,
D-45711 Datteln, Germany. Tel.: +49(0)2363/975296; Fax: +49(0)2363/64211;
E-mail: pf-niklowitz@web.de
Abstract: Coenzyme Q10 (CoQ10) is used by the body as an endogenous
antioxidant and performs essential functions in mitochondrial energy
production. The value of CoQ10 as a biomarker for oxidative stress will be
severely restricted if there are huge individual daily variations in its
concentration. For analysis of diurnal changes in CoQ10 plasma and blood cell
concentrations, blood was collected from nine healthy adults (at two- or
three-hour intervals for plasma, and three times a day for blood cells). CoQ10
was analysed by HPLC using electrochemical detection and internal
standardisation. Daytime variations in CoQ10 concentration in plasma are
maintained within narrow limits and show no statistically significant
difference (Kruskal-Wallis). However, a drop at night-time (0300 h) is
accompanied by a drop in total cholesterol concentration. Remarkable
inter-individual differences in blood cell (erythrocytes, platelets, white
blood cells) content of CoQ10 occur with only slight intra-individual daily
variations. A correlation (Spearman) is found for cholesterol and CoQ10 content
in circulation which may be explained by the carrier capacity of blood for this
highly lipophilic substance. Moreover, a diurnal change in hepatic HMG-CoA
reductase activity may suggest a common diurnal regulation of synthesis of both
CoQ10 and cholesterol.
