Predictors of Loss of Ambulation in Duchenne Muscular Dystrophy: A Systematic Review and Meta-Analysis

Objective

The objective of this study was to describe predictors of loss of ambulation in Duchenne muscular dystrophy (DMD).

Methods

This systematic review and meta-analysis included searches of MEDLINE ALL, Embase, and the Cochrane Database of Systematic Reviews from January 1, 2000, to December 31, 2022, for predictors of loss of ambulation in DMD. Search terms included "Duchenne muscular dystrophy" as a Medical Subject Heading or free text term, in combination with variations of the term "predictor". Risk of bias was assessed using the Newcastle-Ottawa Scale. We performed meta-analysis pooling of hazard ratios of the effects of glucocorticoids (vs. no glucocorticoid therapy) by fitting a common-effect inverse-variance model.

Results

The bibliographic searches resulted in the inclusion of 45 studies of children and adults with DMD from 17 countries across Europe, Asia, and North America. Glucocorticoid therapy was associated with delayed loss of ambulation (overall meta-analysis HR deflazacort/prednisone/prednisolone: 0.44 [95% CI: 0.40-0.48]) (n = 25 studies). Earlier onset of first signs or symptoms, earlier loss of developmental milestones, lower baseline 6MWT (i.e.,<350 vs. ≥350 metres and <330 vs. ≥330 metres), and lower baseline NSAA were associated with earlier loss of ambulation (n = 5 studies). Deletion of exons 3-7, proximal mutations (upstream intron 44), single exon 45 deletions, and mutations amenable of skipping exon 8, exon 44, and exon 53, were associated with prolonged ambulation; distal mutations (intron 44 and downstream), deletion of exons 49-50, and mutations amenable of skipping exon 45, and exon 51 were associated with earlier loss of ambulation (n = 13 studies). Specific single-nucleotide polymorphisms in CD40 gene rs1883832, LTBP4 gene rs10880, SPP1 gene rs2835709 and rs11730582, and TCTEX1D1 gene rs1060575 (n = 7 studies), as well as race/ethnicity and level of family/patient deprivation (n = 3 studies), were associated with loss of ambulation. Treatment with ataluren (n = 2 studies) and eteplirsen (n = 3 studies) were associated with prolonged ambulation. Magnetic resonance biomarkers (MRI and MRS) were identified as significant predictors of loss of ambulation (n = 6 studies). In total, 33% of studies exhibited some risk of bias.

Conclusion

Our synthesis of predictors of loss of ambulation in DMD contributes to the understanding the natural history of disease and informs the design of new trials of novel therapies targeting this heavily burdened patient population.

Interaction of Amyloid-β-(1-42) Peptide and Its Aggregates with Lipid/Water Interfaces Probed by Vibrational Sum-Frequency Generation Spectroscopy

In this study, we use surface-sensitive vibrational sum-frequency generation (VSFG) spectroscopy to investigate the interaction between model lipid monolayers and Aβ(1-42) in its monomeric and aggregated states. Combining VSFG with atomic force microscopy (AFM) and thioflavin T (ThT) fluorescence measurements, we found that only small aggregates with probably a β-hairpin-like structure adsorbed to the zwitterionic lipid monolayer (DOPC). In contrast, larger aggregates with an extended β-sheet structure adsorbed to a negatively charged lipid monolayer (DOPG). The adsorption of small, initially formed aggregates strongly destabilized both monolayers, but only the DOPC monolayer was completely disrupted. We showed that the intensity of the amide-II' band in achiral (SSP) and chiral (SPP) polarization combinations increased in time when Aβ(1-42) aggregates accumulated at the DOPG monolayer. Nevertheless, almost no adsorption of preformed mature fibrils to DOPG monolayers was detected. By performing spectral VSFG calculations, we revealed a clear correlation between the amide-II' signal and the degree of amyloid aggregates (e.g., oligomers or (proto)fibrils) of various Aβ(1-42) structures. The calculations showed that only structures with a significant amyloid β-sheet content have a strong amide-II' intensity, in line with previous Raman studies. The combination of the presented results substantiates the amide-II(') band as a legitimate amyloid marker.

Impaired secretion of platelet granules in patients with Duchenne muscular dystrophy - results of a prospective diagnostic study

A tendency to bleed during scoliosis surgery has been reported repeatedly in Duchenne muscular dystrophy (DMD) and diagnostic studies show a prolonged bleeding time. The pathophysiological background is still not fully understood. The short dystrophin isoform dp71 is expressed in platelets and mediates contractile properties. We performed a bicentric, non-blinded, prospective diagnostic study in 53 patients with confirmed DMD. Extensive laboratory analyses included platelet aggregometry and platelet flow cytometry, as well as routine coagulation analyses. Results of laboratory diagnostics were correlated with clinical data. Patients were subgrouped and analyzed according to ambulatory status and cardiac involvement. Platelet aggregation was reduced after stimulation with ADP (adenosine triphosphate) [60%; reference range 66-84%]. In addition, in the DMD cohort the expression of platelet activation markers CD62 and CD63 (flow cytometry analyses) was significantly lower than in healthy controls, most prominent in non-ambulatory patients with cardiac involvement. There was no clear association with the location of the underlying mutations in the dystrophin gene. No further abnormalities were identified regarding primary or secondary hemostasis. This study shows that platelets of patients with DMD have decreased expression of CD62 and CD63 which are markers for platelet granule release. This may indicate that patients with DMD have an impaired platelet granule secretion which may explain to some extent the increased bleeding, especially in mucocutaneous areas and perioperatively.

Structure Determination of Hen Egg-White Lysozyme Aggregates Adsorbed to Lipid/Water and Air/Water Interfaces

We use vibrational sum-frequency generation (VSFG) spectroscopy to study the structure of hen egg-white lysozyme (HEWL) aggregates adsorbed to DOPG/D₂O and air/D₂O interfaces. We find that aggregates with a parallel and antiparallel β-sheet structure together with smaller unordered aggregates and a denaturated protein are adsorbed to both interfaces. We demonstrate that to retrieve this information, fitting of the VSFG spectra is essential. The number of bands contributing to the VSFG spectrum might be misinterpreted, due to interference between peaks with opposite orientation and a nonresonant background. Our study identified hydrophobicity as the main driving force for adsorption to the air/D₂O interface. Adsorption to the DOPG/D₂O interface is also influenced by hydrophobic interaction; however, electrostatic interaction between the charged protein's groups and the lipid's headgroups has the most significant effect on the adsorption. We find that the intensity of the VSFG spectrum at the DOPG/D₂O interface is strongly enhanced by varying the pH of the solution. We show that this change is not due to a change of lysozyme's and its aggregates' charge but due to dipole reorientation at the DOPG/D₂O interface. This finding suggests that extra care must be taken when interpreting the VSFG spectrum of proteins adsorbed at the lipid/water interface.

The Multiple Sclerosis Inventory of Cognition for Adolescents (MUSICADO): A brief screening instrument to assess cognitive dysfunction, fatigue and loss of health-related quality of life in pediatric-onset multiple sclerosis

OBJECTIVE

Screening for cognitive impairment (CI), fatigue and also Health-related quality of life (HRQoL) in patients with pediatric-onset multiple sclerosis (POMS) is of utmost importance in clinical practice. The aim of this study was to establish a new and validated pediatric screening tool "MUSICADO" that is easy to use and time economical.

METHODS

106 patients with POMS aged 12-18 years and 210 healthy controls (HCs) stratified for age and education underwent neuropsychological testing including a screening test "Multiple Sclerosis Inventory of Cognition" for adults and 8 standardized cognitive tests and established scales to assess fatigue and HRQoL.

RESULTS

The phonemic verbal fluency task (RWT "s-words"), the Trail Making Test A (TMT-A), and the Digit Span Forward discriminated significantly between patients and HCs (p = 0.000, respectively) and showed the highest proportion of test failure in patients (24.5%, 17.9%; 15.1%, respectively). Therefore, they were put together to form the cognitive part of the "MUSICADO". After applying a scoring algorithm with balanced weighting of the subtests and age and education correction and a cut-off score for impairment, 35.8% of patients were categorized to be cognitively impaired (specificity: 88.6%). Fatigue was detected in 37.1% of the patients (specificity: 94.0%) and loss of HRQoL in 41.8% (specificity 95.7%) with the screening version, respectively.

CONCLUSION

The MUSICADO is a newly designed brief and easy to use screening test to help to early identify CI, fatigue, and loss of HRQoL in patients with POMS as cut scores are provided for all three items. Further studies will have to show its usability in independent samples of patients with POMS.