Endurance training ameliorates complex 3 deficiency in a mouse model of Barth syndrome

Barth syndrome (BTHS) is an X-linked metabolic disorder that causes cardiomyopathy in infancy and is linked to mutations within the Tafazzin (TAZ) gene. The first mouse model, a TAZ knockdown model (TAZKD), has been generated to further understand the bioenergetics leading to cardiomyopathy. However, the TAZKD model does not show early signs of cardiomyopathy, and cardiac pathophysiology has not been documented until 7-8 months of age. Here we sought to determine the impact of endurance training on the cardiac and skeletal muscle phenotype in young TAZKD mice. TAZKD exercise trained (TAZKD-ET) and control exercise trained (CON-ET) mice underwent a 35-day swimming protocol. Non-trained aged matched TAZKD and CON mice were used as controls. At the end of the protocol, cardiac MRI was used to assess cardiac parameters. Cardiac MRI showed that training resulted in cardiac hypertrophy within both groups and did not result in a decline of ejection fraction. TAZKD mice exhibited a decrease in respiratory complex I, III, and IV enzymatic activity in cardiac tissue compared to control mice; however, training led to an increase in complex III activity in TAZKD-ET mice resulting in similar levels to those of CON-ET mice. (31)P magnetic resonance spectroscopy of the gastrocnemius showed a significantly lowered pH in TAZKD-ET mice post electrical-stimulation compared to CON-ET mice. Endurance training does not accelerate cardiac dysfunction in young TAZKD mice, but results in beneficial physiological effects. Furthermore, our results suggest that a significant drop in intracellular pH levels may contribute to oxidative phosphorylation defects during exercise.