Figure 1.

Schematic representation of the coordinated events activated by T3 that take place in both nuclei and mitochondria, promoting mitochondrial biogenesis. T3 directly activates the transcription of nuclear- and mitochondrial-genes coding for component of respiratory chain by binding to its nuclear TRs and mitochondrial p43. T3 also indirectly activates respiratory genes transcription by up-regulating the transcription of intermediate factors (such as NRF-1 and -2 and PGC1a). AMPK activation also mediates an indirect effect of T3 on mitochondrial biogenesis.