Magnesium isoglycyrrhizinate alleviates fructose-induced liver oxidative stress and inflammatory injury through suppressing NOXs

Excessive fructose intake is a risk factor for liver oxidative stress injury. Magnesium isoglycyrrhizinate as a hepatoprotective agent is used to treat liver diseases in clinic. However, its antioxidant effects and the underlying potential mechanisms are still not clearly understood. In this study, magnesium isoglycyrrhizinate was found to alleviate liver oxidative stress and inflammatory injury in fructose-fed rats. Magnesium isoglycyrrhizinate suppressed hepatic reactive oxygen species overproduction (0.97 +/- 0.04 a.u. versus 1.34 +/- 0.07 a.u.) in fructose-fed rats by down-regulating mRNA and protein levels of nicotinamide adenine dinucleotide phosphate oxidase (NOX) 1, NOX2 and NOX4, resulting in reduction of interleukin-1 beta (IL-1 beta) levels (1.13 +/- 0.09 a.u. versus 1.97 +/- 0.12 a.u.). Similarly, magnesium isoglycyrrhizinate reduced reactive oxygen species overproduction (1.07 +/- 0.02 a.u. versus 1.35 +/- 0.06 a.u.) and IL-1 beta levels (1.14 +/- 0.09 a.u. versus 1.66 +/- 0.07 a.u.) in fructose-exposed HepG2 cells. Furthermore, data from treatment of reactive oxygen species inhibitor N-acetyl-L-cysteine or NOXs inhibitor diphenyleneiodonium in fructose-exposed HepG2 cells showed that fructose enhanced NOX1, NOX2 and NOX4 expression to increase reactive oxygen species generation, causing oxidative stress and inflammation, more importantly, these disturbances were significantly attenuated by magnesium isoglycyrrhizinate. The molecular mechanisms underpinning these effects suggest that magnesium isoglycyrrhizinate may inhibit NOX1, NOX2 and NOX4 expression to reduce reactive oxygen species generation, subsequently prevent liver oxidative stress injury under high fructose condition. Thus, the blockade of NOX1, NOX2 and NOX4 expression by magnesium isoglycyrrhizinate may be the potential therapeutic approach for improving fructose-induced liver injury in clinic.