Selection for high and low oxygen consumption altered hepatic mitochondrial energy efficiency in mice

Selection for high ( H ) and low ( L ) oxygen consumption ( OC ) as an indirect estimation of maintenance energy requirement was determined. Feed intake and body weight were measured and feed conversion ratio ( FCR ) of 4–8‐week‐old mice was calculated. Respiratory activity of hepatic mitochondria was measured at 12 weeks. Total feed intake ( H : 103.74 g, L : 97.92 g, P  < 0.01), daily feed intake ( H : 3.70 g/day, L : 3.50 g/day, P  < 0.01) and FCR ( H : 18.79, L : 15.50, P  < 0.01) were significantly different between lines. The line by sex interaction was significant for FCR . No line differences were observed in males; and the FCR of the H line was greater than in the L line in females. H line mice had the highest hepatic mitochondrial respiratory activity in state 2 ( P  < 0.01), the highest uncoupled respiratory rate of mitochondria in the presence of an uncoupling agent ( P  < 0.001), and the mitochondrial proton leak. The adenosine diphosphate/ O ratio was highest in the L line ( P  < 0.05). This suggests that the selection for high and low OC induced differences in basal mitochondrial respiration and basal metabolism, resulting in difference in FCR between H and L lines.