Low intensity training of mdx mice reduces carbonylation and increases expression levels of proteins involved in energy metabolism and muscle contraction

Abstract

High intensity training induces muscle damage in dystrophin-deficient mdx mice, an animal model for Duchenne muscular dystrophy. However, low intensity training (LIT) rescues the mdx phenotype and even reduces the level of protein carbonylation, a marker of oxidative damage. Until now, beneficial effects of LIT were mainly assessed at the physiological level. We investigated the effects of LIT at the molecular level on 8-week-old wild-type and mdx muscle using 2D Western blot and protein-protein interaction analysis. We found that the fast isoforms of troponin T and myosin binding protein C as well as glycogen phosphorylase were overcarbonylated and downregulated in mdx muscle. Some of the mitochondrial enzymes of the citric acid cycle were overcarbonylated, whereas some proteins of the respiratory chain were downregulated. Of functional importance, ATP synthase was only partially assembled, as revealed by Blue Native PAGE analysis. LIT decreased the carbonylation level and increased the expression of fast isoforms of troponin T and of myosin binding protein C, and glycogen phosphorylase. In addition, it increased the expression of aconitate hydratase and NADH dehydrogenase, and fully restored the ATP synthase complex. Our study demonstrates that the benefits of LIT are associated with lowered oxidative damage as revealed by carbonylation and higher expression of proteins involved in energy metabolism and muscle contraction. Potentially, these results will help to design therapies for DMD based on exercise mimicking drugs.

Effects of muscular dystrophy, exercise and blocking activin receptor IIB ligands on the unfolded protein response and oxidative stress

“…weeks of low intensity swimming [10]. Differences in the age of animals, time point of animal euthanization following the last bout of exercise, exercise mode, intensity and volume, and in the basal redox status of mdx mice may explain these results.…”

“…Recent studies showed increased oxidative stress as one candidate mechanism that may mediate the pathology of dystrophin deficiency [9,10]. Dystrophic mdx mice at the age of ~14 weeks showed significantly greater levels of oxidized glutathione (GSSG) (P<0.05) compared to healthy wild type animals ( Fig.…”

“…It is linked to several pathological processes including dysfunction of proteostasis and the accumulation of misfolded proteins in the lumen of the endoplasmic reticulum (ER), resulting in ER stress [6]. Notably, secondary consequences of dystrophin deficiency include the loss of skeletal muscle calcium homeostasis and hypoxia [7,8] as well as deficiency in nitric oxide synthase NOS [2] that can trigger oxidative stress [9,10] and in theory, ER stress. Furthermore, accumulation of improperly folded dystrophin in mdx mice [11] may also cause ER stress.…”

“…Exercise improves muscle oxidative capacity in mdx mice [25,26], which as an adaptation could increase resistance to the dystrophic pathology [7]. Exercise training may decrease markers of oxidative stress in mdx mice, but this response may depend on the dose, type, intensity and duration of exercise, and possibly the disease status [9,10]. Decreased levels of oxidative stress would be beneficial since ER stress and oxidative stress can work in a positive feed-forward loop in a manner that disrupts cell function and induces pro-apoptotic signaling [6,27].…”

Comparison of Experimental Protocols of Physical Exercise for mdx Mice and Duchenne Muscular Dystrophy Patients

“…Further variables included the age of the mice and training duration. Voluntary and brief (<30 min per session) exercise of young mice (<8 weeks old) was defined as low intensity training [30, 59], whereas exercise of older mice, or under intensive or prolonged conditions (>30 min), was defined as high intensity training [63]. …”