Pathways affected by 3,5-diiodo-l-thyronine in liver of high fat-fed rats: evidence from two-dimensional electrophoresis, blue-native PAGE, and mass spectrometry.

3,5-Diiodo-l-thyronine (T2) powerfully reduces adiposity in rats fed a high-fat diet (HFD), stimulating (in the liver) fatty acid oxidation and mitochondrial uncoupling, and strongly counteracting steatosis, a condition commonly associated with diet-induced obesity. Proteomics offer unique possibilities for the investigation of changes in the levels and modifications of proteins. Here, combining 2D-E, mass spectrometry, and blue native (BN) PAGE, we studied how the subcellular hepatic phenotype responds to HFD and T2-treatment. By identifying differentially expressed proteins and analyzing their interrelation [using the Ingenuity Pathway Analysis (IPA) platform], we obtained an integrated view of the phenotypic/metabolic adaptations occurring in the liver proteome during HFD with or without T2-treatment. Interestingly, T2 counteracted several HFD-induced changes, mostly in mitochondria. BN-PAGE and subsequent in-gel activity analysis of OXPHOS complexes revealed a modified profile of individual complexes in HFD mitochondria vs. normal ones. This pattern was re-normalized in mitochondria from T2-treated HFD animals. These data indicate that in HFD rats, the effects of T2 on the liver proteome cause it to resemble that associated with a non-steatotic condition. The identified metabolic pathways (mainly at the mitochondrial level) may be responsible for the beneficial effects of T2 on liver adiposity and metabolism.