Elsevier

Clinica Chimica Acta

Volume 347, Issues 1–2, September 2004, Pages 139-144
Clinica Chimica Acta

Age-related changes in plasma coenzyme Q10 concentrations and redox state in apparently healthy children and adults

https://doi.org/10.1016/j.cccn.2004.04.003Get rights and content

Abstract

Background: Coenzyme Q10 (CoQ) is an endogenous enzyme cofactor, which may provide protective benefits as an antioxidant. Because age-related CoQ changes and deficiency states have been described, there is a need to establish normal ranges in healthy children. The objectives of this study are to determine if age-related differences in reduced CoQ (ubiquinol), oxidized CoQ (ubiquinone), and CoQ redox state exist in childhood, and to establish reference intervals for these analytes in healthy children. Methods: Apparently healthy children (n=68) were selected from individuals with no history of current acute illness, medically diagnosed disease, or current medication treatment. Self-reported healthy adults (n=106) were selected from the ongoing Princeton Follow-up Study in greater Cincinnati. Participants were assessed for lipid profiles, ubiquinol concentration, ubiquinone concentration, total CoQ concentration, and CoQ redox ratio. Results: Mean total CoQ and ubiquinol concentrations are similar in younger children (0.2–7.6 years) and adults (29–78 years); however, lipid-adjusted total CoQ concentrations are significantly increased in younger children. Also CoQ redox ratio is significantly increased in younger and older children compared with adults. Conclusions: Elevated CoQ and redox ratios in children may be an indication of oxidative stress effects, which are associated with early development of coronary heart disease.

Introduction

Coenzyme Q10 (CoQ) is an endogenous enzyme cofactor that is produced in most living cells in humans, is distributed in cellular membranes, is an essential component of the mitochondrial respiratory chain, and may provide protective benefits as an antioxidant [1], [2]. Coenzyme Q10 is a redox molecule (2,3-dimethoxy, 5-methyl, 6-decaprenyl benzoquinone), which exists in biochemically reduced CoQ (ubiquinol) and oxidized CoQ (ubiquinone) forms in biological tissues [1]. Because of its important role in mitochondrial and membrane functions, the redox state of CoQ (ubiquinol/ubiquinone ratio) has been suggested to be a useful biomarker of oxidative stress [3], [4].

The development of mitochondrial abnormalities, increased production of free radicals, and the cumulative effects of oxidative stress upon the body have been proposed as the mitochondrial theory of aging [5]. The hypothesis that mitochondria are both a source and a target of cellular free radicals and the knowledge of the important role of CoQ in mitochondrial function have led others to propose that CoQ may be linked with aging mechanisms [6]. The common assumption has been that CoQ levels generally decline with aging [7], but data supporting this postulate are limited. Interestingly, Hara et al. [8] reported low ubiquinol concentrations, redox ratio, and total CoQ plasma concentrations in apparently healthy neonates during the first 5 days after birth.

CoQ reference ranges are needed to support CoQ research and clinical monitoring in pediatric populations. The objectives of this study are twofold: to determine if age-related changes in ubiquinol, ubiquinone, and CoQ redox state (ubiquinol/ubiquinone ratio) occur in healthy individuals between childhood and old age; and to establish reference intervals for these analytes in healthy children.

Section snippets

Materials and methods

This study was approved by the Institutional Review Board of the Cincinnati Children's Hospital Medical Center (CCHMC), Cincinnati, OH. Informed consent was obtained from all subjects or their parents. Adult participants in the study were drawn from the ongoing Princeton Follow-up Study, a 28-year follow-up of former students and their parents from the Princeton Lipid Research Clinics (LRC) Study. The Princeton LRC Study has been described previously [9], [10], [11]. Adults provided a medical

Results

Demographic characteristics and lipid profiles of population samples are summarized in Table 1. Age-related increases in BMI, total cholesterol (TC), high density lipoprotein (HDL), and low density lipoprotein (LDL) are evident (Table 1). No significant differences in total plasma CoQ or ubiquinol concentrations are found between younger children and adults (Table 2). Younger children have increased mean lipid-adjusted total CoQ concentrations compared with adults (Table 2). CoQ redox ratios

Discussion

CoQ deficiency states have been associated with many diseases and conditions in pediatric and adult populations [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25]; however, in a recent study, age-related CoQ changes were not evident in healthy adults ranging from 28 to 80 years [26]. In this study, comparison of CoQ measures in younger adults (29–50 years) vs. older adults (53–78 years) also shows no significant age-related differences (data not shown). Review of previous

Acknowledgements

This study was supported in part by NIH grant HL62394.

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