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

Abstract

Background: The reduced form of Coenzyme Q10 (CoQ10), ubiquinol (Q10H2), serves as a potent antioxidant in mitochondria and lipid membranes. There is evidence that Q10H2 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 CoQ10 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 Q10H2 supplementation (150 mg/d) to evaluate the effect of Q10H2 supplementation on serum GGT activity and GGT1 gene expression.

Findings: There was a strong positive association between CoQ10 status and serum GGT activity in cohort I. However, a gender-specific examination revealed differences between male and female volunteers regarding the association between CoQ10 status and serum GGT activity. Q10H2 supplementation (cohort II) caused a significant decrease in serum GGT activity from T0 to T14 (p < 0.001). GGT1 mRNA levels declined 1.49-fold after Q10H2 supplementation. Of note, other liver enzymes (i.e., aspartate aminotransferase, AST) were not affected by Q10H2 supplementation.

Conclusions: CoQ10 level is positively associated with serum GGT activity. Supplementation with Q10H2 reduces serum GGT activity. This effect might be caused by gene expression. Overall, we provide preliminary evidence that higher Q10H2 levels improve oxidative stress via reduction of serum GGT activity in humans.

Trial registration: Current Controlled Trials ISRCTN26780329.

Figure 1

Prevalence of elevated gamma glutamyltransferase (GGT) activity levels (≥50/40 U/l m/f) in males (m; n = 220) and females (f; n = 196).

Figure 2

Relationship between total CoQ ₁₀ (A), ubiquinol (B), ubiquinone (C) and CoQ ₁₀ redox state (D) and serum GGT activity.

Figure 3

The impact of Q₁₀H₂ supplementation on gamma glutamyltransferase (GGT, A) and GGT1 mRNA levels (B) as well as alanine aminotransferase (AST, C) and GOT2 mRNA levels (D). Data show respective effects before (T₀) and after (T₁₄) supplementation. Data are calculated from the mean (±SEM) of 53 (A + C) or rather three (B + D) volunteers. Bar graphs are presented as the mean ± SD, ***p < 0.001 significant differences between T₀ and T₁₄, paired Student’s t-test.