Improved mitochondrial function in the hearts of sarcolipin-deficient dystrophin and utrophin double-knockout mice
Satvik Mareedu, … , Lai-Hua Xie, Gopal J. Babu
Satvik Mareedu, … , Lai-Hua Xie, Gopal J. Babu
Published April 2, 2024
Citation Information: JCI Insight. 2024;9(9):e170185. https://doi.org/10.1172/jci.insight.170185.
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Research Article Metabolism

Improved mitochondrial function in the hearts of sarcolipin-deficient dystrophin and utrophin double-knockout mice

Abstract

Duchenne muscular dystrophy (DMD) is a progressive muscle-wasting disease associated with cardiomyopathy. DMD cardiomyopathy is characterized by abnormal intracellular Ca2+ homeostasis and mitochondrial dysfunction. We used dystrophin and utrophin double-knockout (mdx:utrn–/–) mice in a sarcolipin (SLN) heterozygous-knockout (sln+/–) background to examine the effect of SLN reduction on mitochondrial function in the dystrophic myocardium. Germline reduction of SLN expression in mdx:utrn–/– mice improved cardiac sarco/endoplasmic reticulum (SR) Ca2+ cycling, reduced cardiac fibrosis, and improved cardiac function. At the cellular level, reducing SLN expression prevented mitochondrial Ca2+ overload, reduced mitochondrial membrane potential loss, and improved mitochondrial function. Transmission electron microscopy of myocardial tissues and proteomic analysis of mitochondria-associated membranes showed that reducing SLN expression improved mitochondrial structure and SR-mitochondria interactions in dystrophic cardiomyocytes. These findings indicate that SLN upregulation plays a substantial role in the pathogenesis of cardiomyopathy and that reducing SLN expression has clinical implications in the treatment of DMD cardiomyopathy.

Authors

Satvik Mareedu, Nadezhda Fefelova, Cristi L. Galindo, Goutham Prakash, Risa Mukai, Junichi Sadoshima, Lai-Hua Xie, Gopal J. Babu

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Figure 6

Improved mitochondrial structure and MAMs in mdx:utrn–/–:sln+/– ventricles.

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Improved mitochondrial structure and MAMs in mdx:utrn–/–:sln+/– ventricl...
(A) Representative transmission electron micrographs of ventricular sections from WT, mdx:utrn–/–, and mdx:utrn–/–:sln+/– mice (left panel). The 45,000× original magnification shows the SR-mitochondrial junctions (indicated by arrows) and loss of cristae in the SR-associated mitochondria. Quantification (right panel) showing cristae density in SR-associated and non-SR-associated mitochondria. We randomly selected 6 to 8 fields at 10,000× original magnification and analyzed approximately 150 mitochondria/genotype (40–60 mitochondria/mouse heart) for cristae density measurements. n = 3 mice per genotype. Data were analyzed by ordinary 1-way ANOVA for multigroup comparisons. Values shown are means ± SE. (B) Representative Western blots (left panel) and quantitation (right panel) showing RyR2, SERCA2a, SLN, and PLN protein levels in the MAMs purified from the myocardium of WT, mdx:utrn–/–, and mdx:utrn–/–:sln+/– mice. We pooled 4–5 ventricles for each MAM preparation. n = 3 MAM preparation/genotype. For Western blotting, 10–20 μg of MAM protein is loaded per well. Data were analyzed by ordinary 1-way ANOVA for multigroup comparisons. Values shown are means ± SE. *P < 0.01 vs. WT and mdx:utrn–/–:sln+/–; #P < 0.05 vs. WT. (C) Venn diagram showing significantly altered MAM proteins between mdx:utrn–/– and WT and mdx:utrn–/–:sln+/– and mdx:utrn–/– mice. (D) Heatmap of 43 MAM proteins that are well clustered between WT and mdx:utrn–/–:sln+/– but differentially expressed in mdx:utrn–/– mice. (E) Horizontal stacked bar chart comparing the top canonical pathways either up- or downregulated in the MAMs between mdx:utrn–/–:sln+/– and mdx:utrn–/– and between mdx:utrn–/– and WT mice with a P value cutoff of 0.05.