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.

OBJECTIVE. The prevalence and natural history of gastroesophageal reflux in infants have been poorly documented. The aim of this study was to evaluate the prevalence and natural history of infant regurgitation in Italian children during the first 2 years of life. METHODS. A detailed questionnaire, according to the Rome II criteria, was completed by 59 primary care pediatricians to assess infant regurgitation in consecutive patients seen in their office over a 3-month period. A total of 2642 patients aged 0 to 12 months were prospectively enrolled during this 3-month period. Follow-up was performed at 6, 12, 18, and 24 months of age. RESULTS. A total of 313 children (12%; 147 girls) received the diagnosis of infant regurgitation. Vomiting was present in 34 of 313 patients. Their score for the Infant Gastroesophageal Reflux Questionnaire was 8.51 ± 4.75 (mean ± SD). Follow-up visits were conducted to the end in 210 of 313 subjects. Regurgitation had disappeared in 56 of 210 infants by the first 6 months of age, in 128 by the first 12 months, in 23 at 18 months, and in 3 patients by the first 24 months. At follow-up, 1 of 210 patients had developed a gastroesophageal reflux disease with esophagitis, proven endoscopically and histologically; another patient received a diagnosis of cow milk protein intolerance. The Infant Gastroesophageal Reflux Questionnaire score reached 0 after 8.2 ± 3.9 months in breastfed infants (89 of 210) and after 9.6 ± 4.1 months in artificially fed infants. CONCLUSIONS. We found that 12% of Italian infants satisfied the Rome II criteria for infant regurgitation. Eighty-eight percent of 210 infants who had completed a 24-month follow-up period had improved at the age of 12 months. Only 1 patient later turned out to have gastroesophageal reflux disease. Use of breast milk was associated with a shorter time necessary to reach an Infant Gastroesophageal Reflux Questionnaire score of 0.