Ubiquinol reduces gamma glutamyltransferase as a marker of oxidative stress in humans

BACKGROUND: The reduced form of Coenzyme Q(10) (CoQ(10)), ubiquinol (Q(10)H(2)), serves as a potent antioxidant in mitochondria and lipid membranes. There is evidence that Q(10)H(2) protects against oxidative events in lipids, proteins and DNA. Serum gamma-glutamyltransferase (GGT) activity is associated with cardiovascular diseases. In a physiological range, activity of GGT is a potential early and sensitive marker of inflammation and oxidative stress. In this study, we first examined the relationship between CoQ(10) status and serum GGT activity in 416 healthy participants between 19 and 62 years of age in a cross-sectional study (cohort I). In the second step, 53 healthy males (21–48 years of age; cohort II) underwent a 14-day Q(10)H(2) supplementation (150 mg/d) to evaluate the effect of Q(10)H(2) supplementation on serum GGT activity and GGT1 gene expression. FINDINGS: There was a strong positive association between CoQ(10) status and serum GGT activity in cohort I. However, a gender-specific examination revealed differences between male and female volunteers regarding the association between CoQ(10) status and serum GGT activity. Q(10)H(2) supplementation (cohort II) caused a significant decrease in serum GGT activity from T(0) to T(14) (p < 0.001). GGT1 mRNA levels declined 1.49-fold after Q(10)H(2) supplementation. Of note, other liver enzymes (i.e., aspartate aminotransferase, AST) were not affected by Q(10)H(2) supplementation. CONCLUSIONS: CoQ(10) level is positively associated with serum GGT activity. Supplementation with Q(10)H(2) reduces serum GGT activity. This effect might be caused by gene expression. Overall, we provide preliminary evidence that higher Q(10)H(2) levels improve oxidative stress via reduction of serum GGT activity in humans. TRIAL REGISTRATION: Current Controlled Trials ISRCTN26780329.