Selenoprotein P-mediated reductive stress impairs cold-induced thermogenesis in brown fat

Reactive oxygen species (ROS) oxidize and activate the uncoupler protein 1 (UCP1) in brown adipose tissue (BAT) under physiological cold exposure and noradrenaline (NA) stimulation to increase thermogenesis. However, pathological significance and the endogenous regulator of the ROS-mediated BAT activation remain unclear. Here, we show that serum levels of selenoprotein P (SeP, encoded by Selenop) are negatively correlated with BAT activity in humans. SeP impairs UCP1 activity and thermogenesis. Physiological cold exposure downregulates Selenop in BAT. BAT-specific Selenop-deficient (BAT-Selenop KO) mice presented elevated NA-induced mitochondrial ROS production, sulfenylated UCP1, and enhanced thermogenesis and glucose uptake in BAT during cold exposure. SeP inhibits mitochondrial ROS by upregulating the expression of the antioxidant enzyme, glutathione peroxidase 4, and impairs glucose uptake in brown adipocytes. High fat/high sucrose diet upregulates Selenop in the liver and inhibits the NA-induced BAT thermogenesis in BAT-Selenop KO mice. Our data indicate that SeP, as the hepatokine and BATkine, is the first identified intrinsic factor inducing reductive stress that impairs UCP1 activation and thermogenesis in BAT, and therefore may be a potential therapeutic target for obesity and diabetes.