Silencing of ubiquinone biosynthesis genes extends life span in Caenorhabditis elegans

Ubiquinone (coenzyme Q; Q) is a key factor in the mitochondria electron transport chain, but it also functions as an antioxidant and as a cofactor of mitochondrial uncoupling proteins. Furthermore, Q isoforms balance in Caenorhabiditis elegans is determined by both dietary intake and endogenous biosynthesis. In the absence of synthesis, withdrawal of dietary Q(8) in adulthood extends life span. Thus, Q plays an important role in the aging process and understanding its synthesis acquires a new impetus. We have identified by RNA interference (RNAi) eight genes, including clk-1, involved in ubiquinone biosynthesis in C. elegans feeding animals with dsRNA-containing Escherichia coli HT115 strains. Silenced C. elegans showed lower levels of both endogenous Q(9) and Q(8) provided by diet, produced less superoxide without a significant modification of mitochondrial electron chain, and extended life span compared with non-interfered animals. E. coli strains harboring dsRNA also interfered with their own Q(8) biosynthesis. These findings suggest that more efficient electron transport between a lower amount of Q and electron transport capacity of the mitochondrial complexes leads to less production of reactive oxygen species that contributes to extension of life span in the nematode C. elegans.