Antioxidants and glucose metabolism disorders.

PURPOSE OF REVIEW: Recent evidence suggests that oxidative stress is a cornerstone of the metabolic mechanisms by which overfeeding leads to insulin resistance. This review is an update of the most recent arguments in favor of this theory and of the possible role of antioxidants.

RECENT FINDINGS: Reactive oxidative species (ROS) are produced by multiple pathways within the cell and are essential for many cellular functions. ROS production is balanced by enzymatic and nonenzymatic antioxidant systems. The perturbation of the pro-oxidant/antioxidant balance can lead to increased oxidative damage of macromolecules, a phenomenon known as 'oxidative stress'. ROS are involved both in insulin signal transduction and in insulin resistance when produced in excess. Overfeeding, saturated fatty acids, and obesity play a key role in the excessive production of ROS. However, a diet rich in fruits and vegetables, and therefore antioxidants, has demonstrated beneficial effects against oxidative damages and insulin resistance.

SUMMARY: Experimental data are in favor of a beneficial role of antioxidants in glucose metabolism, but clinical data in humans are more controversial. Even if a diet rich in fruits and vegetables could provide an optimal mix of antioxidants, it remains unclear whether supplementation with antioxidants alone can reproduce the same effect.