title: Efficacy of antioxidant treatment in reducing resistin serum levels: a randomized study.
abstract: OBJECTIVE
  Few in vitro studies have examined the participation of resistin, a recently discovered adipokine, in oxidative processes. We investigated whether in vivo treatment with the antioxidant vitamin C might affect resistin serum levels.
  
  
  METHODS
  Randomized prospective open trial.
  
  
  METHODS
  San Giovanni Battista Hospital, Turin, Italy.
  
  
  METHODS
  Eighty healthy individuals.
  
  
  METHODS
  Administration of 2 g of ascorbic acid orally for 2 wk (n = 40; experimental group) or no supplementation (n = 40; control group).
  
  
  METHODS
  The primary end point was the between-group difference in the before-after change in resistin serum level after vitamin C supplementation. Secondary endpoints were the within- and between-group changes in glucose, insulin, lipid parameters, C-reactive protein fasting values, and markers of oxidative stress.
  
  
  RESULTS
  In the experimental group, vitamin C supplementation was significantly associated with both resistin concentration reduction (from 4.3 +/- 1.5 to 2.9 +/- 0.8 ng/ml; 95% confidence interval [CI] -1.87, -1.03) and ascorbic acid level increase (from 9.4 +/- 2.9 to 19.0 +/- 5.2 mg/l; 95% CI 7.9, 11.2). In the control group, resistin levels did not change significantly (from 4.2 +/- 1.0 to 4.3 +/- 0.9 ng/ml; 95% CI -0.07, 0.37). The between-group differences were highly significant (p < 0.001). Vitamin C supplementation was also associated with a statistically significant reduction in nitrotyrosine level and incremental increase in reduced glutathione. In a linear regression model, within-individual changes in vitamin C concentrations were inversely correlated with changes in resistin levels in both groups (each unit increase of vitamin C corresponded to a decrease of about 0.10 units of resistin levels (95% CI 0.13, 0.08; p < 0.001).
  
  
  CONCLUSIONS
  This is to our knowledge the first randomized trial in humans that has demonstrated that short-term vitamin C supplementation could significantly reduce resistin levels, independent of changes in inflammatory or metabolic variables. Future investigations of resistin participation in oxidative processes are warranted.
authors.affiliation: Department of Internal Medicine, University of Turin, Turin, Italy. sbo@molinette.piemonte.it
authors.forename: Simona
authors.initials: S
authors.lastname: Bo
authors.forename: Giovannino
authors.initials: G
authors.lastname: Ciccone
authors.forename: Marilena
authors.initials: M
authors.lastname: Durazzo
authors.forename: Roberto
authors.initials: R
authors.lastname: Gambino
authors.forename: Paola
authors.initials: P
authors.lastname: Massarenti
authors.forename: Ileana
authors.initials: I
authors.lastname: Baldi
authors.forename: Antonela
authors.initials: A
authors.lastname: Lezo
authors.forename: Elisa
authors.initials: E
authors.lastname: Tiozzo
authors.forename: Daniela
authors.initials: D
authors.lastname: Pauletto
authors.forename: Maurizio
authors.initials: M
authors.lastname: Cassader
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Pagano