Overexpression of mitochondrial uncoupling protein-3 does not decrease production of the reactive oxygen species, elevated by palmitate in skeletal muscle cells.

Fatty acids induced an increase in reactive oxygen species (ROS) and enhanced NF-kappaB activation in L6 myotubes differentiated in culture. Palmitate proved more effective than oleate in eliciting these effects. The induction of uncoupling protein-3 (UCP3) at levels similar to those occurring in vivo, attained through the use of an adenoviral vector, led to a reduction of mitochondrial membrane potential in L6 myotubes. However, the capacity of palmitate to increase ROS was not reduced but, quite the opposite, it was moderately enhanced due to the presence of UCP3. The presence of UCP3 in mitochondria did not modify the expression of genes encoding ROS-related enzymes, either in basal conditions or in the presence of palmitate. However, in the presence of UCP3, UCP2 mRNA expression was down-regulated in response to palmitate. We conclude that UCP3 does not act as a protective agent against palmitate-dependent induction of ROS production in differentiated skeletal muscle cells.