Cardiolipin deficiency in Barth syndrome is not associated with increased superoxide/H₂O₂ production in heart and skeletal muscle mitochondria

Abstract

Barth syndrome (BTHS) is a rare X-linked genetic disorder caused by mutations in the gene encoding the transacylase tafazzin and characterized by loss of cardiolipin and severe cardiomyopathy. Mitochondrial oxidants have been implicated in the cardiomyopathy in BTHS. Eleven mitochondrial sites produce superoxide/hydrogen peroxide (H 2 O 2) at significant rates. Which of these sites generate oxidants at excessive rates in BTHS is unknown. Here, we measured the maximum capacity of superoxide/H 2 O 2 production from each site and the ex vivo rate of superoxide/H 2 O 2 production in the heart and skeletal muscle mitochondria of the tafazzin knockdown mice (tazkd) from 3 to 12 months of age. Despite reduced oxidative capacity, superoxide/H 2 O 2 production was indistinguishable between tazkd mice and wild-type littermates. These observations raise questions about the involvement of mitochondrial oxidants in BTHS pathology.

The Influence of Supplemental Dietary Linoleic Acid on Skeletal Muscle Contractile Function in a Rodent Model of Barth Syndrome

“…Slowed contractile kinetics in TazKD soleus compared to WT did not translate to changes in grip strength. A lack of change to in vivo muscle function is similar to previous research in that locomotor activity in TazKD mice did not differ from WT ( Cole et al, 2018 ; Goncalves et al, 2021 ). Grip strength is a common non-invasive in vivo evaluation of muscle force ( Ge et al, 2016 ; Martinez-Huenchullan et al, 2017 ).…”

“…To our knowledge, this is the first study to fully characterize an impaired contractile phenotype in the pre-clinical rodent model of Barth syndrome and the potential efficacy of dietary supplemental LA to reverse this phenotype. Similar to previous studies, administration of doxycycline to TazKD mice in utero and post-weaning resulted in decreased skeletal muscle Taz mRNA, protein, CL content, CL 18:2n6 composition, and increased MLCL:CL ratio ( Acehan et al, 2011 ; Soustek et al, 2011 ; Ikon et al, 2018 ; Johnson et al, 2018 ; Goncalves et al, 2021 ), along with reduced weight gain ( Acehan et al, 2011 ; Cole et al, 2016 ; Ikon et al, 2018 ; Johnson et al, 2018 ; Goncalves et al, 2021 ). The main findings are (1) TazKD soleus demonstrated slower force development and relaxation in vitro as key contributors to this impaired contractile phenotype, (2) the impaired contractile phenotype seen in vitro in TazKD compared to WT did not translate to altered muscle function in vivo , and (3) supplemental LA attenuated, to some degree, soleus in vitro impaired contractile phenotype in TazKD mice, which appears to not be fully mediated by CL content and composition.…”

“…Despite these positive findings in cell culture, to our knowledge, no studies have examined the influence of supplemental LA on CL content and composition, and skeletal muscle function at the level of the whole organism. The preclinical Taz knockdown (TazKD) mouse model has been extensively used in the literature because it closely recapitulates Barth syndrome pathologies seen in human patients ( Ren et al, 2019 ), including skeletal muscle weakness ( Acehan et al, 2011 ; Soustek et al, 2011 ) and exercise intolerance ( Powers et al, 2013 ; Schafer et al, 2018 ; Goncalves et al, 2021 ). As such, this preclinical model may prove important in testing the possibility and efficacy of supplemental LA treatment.…”

An update on methods and approaches for interrogating mitochondrial reactive oxygen species production

“…These substrate and inhibitor combinations have been successfully used to demonstrate /H 2 O 2 sources outside of complex I and II can also generate significant amounts of ROS [ 34 , 56 ]. These approaches have been implemented to study ROS production in various disease models including Barth's syndrome, heart disease, insulin resistance, and diet-induced obesity [ 27 , [56] , [57] , [58] ]. Additionally, this toolkit was used to show there are sex and mouse-strain differences in the native rates of production for the twelve sites [ 56 , 59 ].…”

Skeletal Muscle Mitochondria Dysfunction in Genetic Neuromuscular Disorders with Cardiac Phenotype

“…In contrast to these findings, a recent investigation showed that ROS levels were indistinguishable between TAZ knock-down mice and wild-type littermates. Thus, it can be concluded that cardiolipin deficiency in Barth syndrome pathogenesis is unlikely associated with boosted production of ROS [ 152 ].…”