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Changes in Physiopathological Markers in Myotonic Dystrophy Type 1 Skeletal Muscle: A 3-Year Follow-up Study

Marie-Pier Roussel1,2, Aymeric Ravel-Chapuis3,4,5, Jonathan Gobin4,5

  • 1Département des Sciences Fondamentales, Université du Québec à Chicoutimi, Saguenay, QC, Canada.

Journal of Neuromuscular Diseases
|July 20, 2024
PubMed
Abstract

Insights

Myotonic dystrophy type 1 (DM1) causes muscle weakness linked to fiber changes and nuclear foci. The autophagy marker LC3BII/LC3BI ratio shows potential for tracking strength loss in DM1 patients.

Area of Science:

  • Neurology
  • Muscle Physiology
  • Biochemistry

Background:

  • Myotonic dystrophy type 1 (DM1) is a progressive genetic disorder affecting skeletal muscles.
  • It stems from abnormal CTG repeats in the DMPK gene, leading to nuclear foci and MBNL1 sequestration.
  • The precise impact of DM1 on skeletal muscle pathophysiology remains under-investigated.

Purpose of the Study:

  • To identify physiopathological markers associated with maximal strength loss in DM1 patients over time.
  • To explore the relationship between muscle fiber characteristics, nuclear foci, MBNL1, and strength decline.

Main Methods:

  • Twenty-two DM1 participants underwent strength testing and muscle biopsies over three years.
  • Muscle fiber typing, size (MFD, AF/HF), and nuclear foci/MBNL1 colocalization were assessed.
  • Immunoblotting quantified key proteins including GSK3β, p62, and autophagy markers (LC3BI, LC3BII).

Main Results:

  • Maximal isometric muscle strength (MIMS) loss correlated with Type 1 fiber minimal Feret's diameter (MFD) decrease and atrophy factor (AF) increase.
  • Baseline nuclear foci/MBNL1+ percentage and strength training predicted changes in foci accumulation.
  • Correlations were observed between MIMS changes and levels of GSK3β, p62, LC3BI, LC3BII, and the LC3BII/LC3BI ratio.

Conclusions:

  • Decreased Type 1 MFD and increased AF are linked to MIMS loss in DM1.
  • Strength training may mitigate the accumulation of nuclear foci/MBNL1.
  • The LC3BII/LC3BI ratio demonstrates potential as a biomarker for MIMS loss in DM1, warranting further research.
Keywords:
Myotonic dystrophy type 1histomorphologymaximal muscle strengthnatural history studynuclear foci and MBNL1 colocalizationprotein expression

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