Antioxidant treatment induces reductive stress associated with mitochondrial dysfunction in adipocytes [Cell Biology] (Journal of Biological Chemistry)

?-Adrenergic stimulation of adipose tissue increases mitochondrial density and activity (browning) that are associated with improved whole-body metabolism. Whereas chronically elevated levels of reactive oxygen species (ROS) in adipose tissue contribute to insulin resistance, transient ROS elevation stimulates physiological processes such as adipogenesis. Here, using a combination of biochemical and cell and molecular biology-based approaches, we studied whether ROS or antioxidant treatment affects ?3-adrenergic receptor (?3-AR) stimulation-induced adipose tissue browning. We found that ?3-AR stimulation increases ROS levels in cultured adipocytes, but, unexpectedly, pretreatment with different antioxidants (N-acetylcysteine, vitamin E, or GSH ethyl ester) did not prevent this ROS increase. Using fluorescent probes, we discovered that the antioxidant treatments instead enhanced ?3-AR stimulation-induced mitochondrial ROS production. This pro-oxidant effect of antioxidants was, even in the absence of ?3-AR stimulation, associated with decreased oxygen consumption and increased lactate production in adipocytes. We observed similar antioxidant effects in WT mice: N-acetylcysteine blunted ?3-AR stimulation-induced browning of white adipose tissue and reduced mitochondrial activity in brown adipose tissue even in the absence of ?3-AR stimulation. Furthermore, N-acetylcysteine increased the levels of peroxiredoxin 3 and superoxide dismutase 2 in adipose tissue, indicating increased mitochondrial oxidative stress. We interpret this negative impact of antioxidants on oxygen consumption in vitro and adipose tissue browning in vivo as essential adaptations that prevent a further increase in mitochondrial ROS production. In description, these results suggest that chronic antioxidant supplementation can produce a paradoxical increase in oxidative stress associated with mitochondrial dysfunction in adipocytes.