First published October 1, 2014 - More info
Although supraphysiological concentrations of urea are known to increase oxidative stress in cultured cells, it is generally thought that the elevated levels of urea in chronic renal failure patients have negligible toxicity. We previously demonstrated that ROS increase intracellular protein modification by O-linked β-N-acetylglucosamine (O-GlcNAc), and others showed that increased modification of insulin signaling molecules by O-GlcNAc reduces insulin signal transduction. Because both oxidative stress and insulin resistance have been observed in patients with end-stage renal disease, we sought to determine the role of urea in these phenotypes. Treatment of 3T3-L1 adipocytes with urea at disease-relevant concentrations induced ROS production, caused insulin resistance, increased expression of adipokines retinol binding protein 4 (RBP4) and resistin, and increased O-GlcNAc–modified insulin signaling molecules. Investigation of a mouse model of surgically induced renal failure (uremic mice) revealed increased ROS production, modification of insulin signaling molecules by O-GlcNAc, and increased expression of RBP4 and resistin in visceral adipose tissue. Uremic mice also displayed insulin resistance and glucose intolerance, and treatment with an antioxidant SOD/catalase mimetic normalized these defects. The SOD/catalase mimetic treatment also prevented the development of insulin resistance in normal mice after urea infusion. These data suggest that therapeutic targeting of urea-induced ROS may help reduce the high morbidity and mortality caused by end-stage renal disease.
Maria D’Apolito, Xueliang Du, Haihong Zong, Alessandra Catucci, Luigi Maiuri, Tiziana Trivisano, Massimo Pettoello-Mantovani, Angelo Campanozzi, Valeria Raia, Jeffrey E. Pessin, Michael Brownlee, Ida Giardino
Original citation: J Clin Invest. 2010;120(1):203–213. doi:10.1172/JCI37672.
Citation for this addendum: J Clin Invest. 2014;124(10):4668. doi:10.1172/JCI78338.
Concerns were recently raised with regard to the immunoblot images in Figure 5B, and it was unclear to the Editorial Board whether the position of the bands in lane 2 of the total IRS-1 blot and the O-GlcNAc was consistent with stripping and reprobing of the same membrane. An investigative committee at the University of Foggia found no evidence for image manipulation after comprehensive analysis of the available images by a noted expert in digital image analysis; however, the original raw data were unavailable for review due to a flood in the region. The authors have therefore performed a replicate experiment; the results (shown below) are consistent with the findings originally reported in the paper.