Assessment of a Complex V Mutation and Metabolic Economy between C3H/HeJ and C3H/HeN Mice
Jamelle Brown; Scott Ballinger, Ph.D.; Meghana Sthanam; Melissa Sammy; and David Westbrook University of Alabama at Birmingham, Birmingham, AL
The C3H mouse is widely used in cardiovascular disease (CVD) research because of its high resistance to atherosclerosis and other CVD risk factors. Two strains of the C3H mouse, C3H/HeJ and C3H/HeN, are often used interchangeably; however, previous studies have shown that there are several physiological differences between these strains. There are also mitochondrial genetic differences between the strains, namely a missense mutation in the mitochondrial DNA (mtDNA) at position 8889 which occurs in complex V of the mitochondrial electron transport chain. This mutation results in an amino acid change from alanine to threonine in the C3H/HeJ strain. Complex V is also known as ATP synthase, which uses the transmembrane proton gradient to couple oxidative phosphorylation with ATP production. Mitochondrial function and dysfunction have been shown to play a role in CVD development. Therefore, we hypothesize that this mutation in complex V results in a functional change in ATP-linked oxygen consumption and ATP production by the mitochondria, which may affect CVD susceptibility. To approach this question, isolated mitochondria from cardiac and skeletal muscle of six-week-old mice were subjected to substrates, inhibitors, and uncouplers of the mitochondrial electron transport chain. The Seahorse XF24 analyzer was used to assess ATP-linked oxygen consumption and ATP production was measured using a luciferase assay. Preliminary data revealed no observable difference in ATP-linked oxygen consumption between strains for either tissue. ATP production was higher in both tissues in the C3H/HeJ strain. This indicates that C3H/HeJ mice have more economical mitochondria than C3H/HeN mice since more ATP is generated from the same amount of oxygen. However, due to small sample size, statistical significance could not be determined. Subsequent studies will attempt to replicate these findings by increasing sample size.