Glabridin, an isoflavan from licorice root, upregulates paraoxonase 2 expression under hyperglycemia and protects it from oxidation

Scope: Hyperglycemia is associated with oxidative stress, which accelerates cardiovascular complications. This study investigates the potential of glabridin to regulate paraoxonase 2 (PON2) levels, in vivo, and explores the glabridin protective effect on PON2 through tryptophan-fluorescence quenching and mass spectrometry. Methods and results: Adult mouse offspring of saturated fatty acids fed mothers, which developed hyperglycemia after exposure to a high fat diet in their adult life, had lower levels of heart PON2 mRNA and protein expression than did the control mice (64 and 26%, respectively). Glabridin supplementation significantly upregulated PON2 mRNA and protein expression in the liver (2.1-fold and 2.6-fold, respectively) and heart (2.5-fold and 1.6-fold, respectively) in these mice. In vitro studies demonstrated that the fluorescence quenching of PON2 by glabridin was a result of the formation of a glabridin-PON2 interaction. The binding constant (7.61 × 10⁵ M^-1) and the ΔG (-33.55kJ/mol) indicated that this interaction was driven by a hydrophobic force, which confers protection against CuSO₄-induced PON2 oxidation. Conclusion: Such results indicate that glabridin preserves the anti-atherogenic abilities of PON2 by maintaining its levels, in vivo. The glabridin-PON2 interaction may be the mechanism by which glabridin protects PON2 from oxidation, thus contributing to the protection of PON2 activity in hyperglycemia.