Our previous results demonstrated that
tungstate decreased
weight gain and adiposity in obese rats through increased thermogenesis and
lipid oxidation, suggesting that brown adipose tissue was one of the targets of its antiobesity effect. To identify potential targets of
tungstate, we used DIGE to compare brown adipose tissue
protein extracts from the following experimental groups: untreated lean,
tungstate-treated lean, untreated obese, and
tungstate-treated obese rats. To distinguish direct targets of
tungstate action from those that are secondary to
body weight loss, we also included in the analysis an additional group consisting of obese rats that lose weight by
caloric restriction. Hierarchical clustering of analysis of variance and t test contrasts clearly separated the different experimental groups. DIGE analysis identified 20
proteins as
tungstate obesity direct targets involved in Krebs cycle, glycolysis, lipolysis and
fatty acid oxidation, electron transport, and redox.
Protein oxidation was decreased by
tungstate treatment, confirming a role in redox processes; however,
palmitate oxidation, as a measure of
fatty acid beta-oxidation, was not altered by
tungstate, thus questioning its putative function in
fatty acid oxidation.
Protein network analyses using Ingenuity Pathways Analysis highlighted
peroxisome proliferator-activated receptor gamma coactivator 1alpha (PGC-1alpha) as a potential target. We confirmed by real time PCR that indeed
tungstate up-regulates PGC-1alpha, and its major target,
uncoupling protein 1, was also increased as shown by Western blot. These results illustrate the utility of proteomics and bioinformatics approaches to identify targets of
obesity therapies and suggest that in brown adipose tissue
tungstate modulates redox processes and increases energy dissipation through uncoupling and PGC-1alpha up-regulation, thus contributing to its overall antiobesity effect.