Figure 2.

Schematic representation of signaling and biochemical pathways activated by T3 and/or T2 in skeletal muscle that promote variations in substrate metabolism, lipid handling, and thermogenesis at the mitochondrial level. If not accompanied by T3 or T2, the symbol + indicates that the pathway is stimulated by both iodothyronines. T3 and T2 activate processes leading to the import of FFA and their oxidation at the mitochondrial level, with FAT/CD36 playing a role. Through activation of AMPK-ACC signaling pathway, T2 and T3 relieves the inhibition of CPT1 by malonyl-CoA, and thus promote the entrance of fatty acids into mitochondria and their oxidation. The rise in MTE activity, would contribute to maintain a high level of fatty acid oxidation rate. The box represents processes, occurring at the level of mitochondrial inner membrane, underlying coupled and uncoupled respiration affected by T3 and T2.