[Role of novel mitochondrial proteins in energy balance]

Mitochondrial activity plays a key role in the control of thermogenesis and energy expenditure in homeothermic organisms. Recently, much attention has been paid to the novel protein members of UCP family as putative regulators of uncoupled respiration. Nevertheless, it is likely that other aspects, as yet unrecognized, of mitochondrial biology are also crucial to comprehend mitochondrial function. Thus, mitochondria are organized in filaments or in networks in many cell types as a result of the operation of fusion and fission events. The demonstration that mitofusin-2, a protein involved in mitochondrial fusion, stimulates the mitochondrial oxidation of substrates, cell respiration and mitochondrial membrane potential suggests that this protein may play an important role in mitochondrial metabolism, and as a consequence, in energy balance. Furthermore, the observation that mitofusin-2 expression is repressed in obese skeletal muscle suggests a posible role in the pathophysiology and/or etiopathogenesis of obesity.