Bone health in Duchenne muscular dystrophy: clinical and biochemical correlates.

PURPOSE: An increased fracture risk is commonly reported in Duchenne muscular dystrophy (DMD). Our aim was to investigate bone mineral density (BMD) and bone turnover, including sclerostin, and their association with markers of cardiac and respiratory performance in a cohort of DMD subjects. METHODS: In this single center, cross sectional observational study, lumbar spine (LS) BMD Z-scores, C-terminal telopeptide of procollagen type I (CTX) and osteocalcin (BGP), as bone resorption and formation markers, respectively, and sclerostin were assessed. Left ventricular ejection fraction (LVEF) and forced vital capacity (FVC) were evaluated. Clinical prevalent fractures were also recorded. RESULTS: Thirty-one patients [median age = 14 (12-21.5) years] were studied. Ambulant subjects had higher LS BMD Z-scores compared with non-ambulant ones and subjects with prevalent clinical fractures [n = 9 (29%)] showed lower LS BMD Z-scores compared with subjects without fractures. LS BMD Z-scores were positively correlated with FVC (r = 0.50; p = 0.01), but not with glucocorticoid use, and FVC was positively associated with BGP (r = 0.55; p = 0.02). In non-ambulant subjects, LS BMD Z-scores were associated with BMI (r = 0.54; p = 0.02) and sclerostin was associated with age (r = 0.44; p = 0.05). Age, BMI, FVC and sclerostin were independently associated with LS BMD Z-score in a stepwise multiple regression analysis. Older age, lower BMI, FVC and sclerostin were associated with lower LS BMD Z-scores. CONCLUSION: In a cohort of DMD patients, our data confirm low LS BMD Z-scores, mainly in non-ambulant subjects and irrespective of the glucocorticoid use, and suggest that FVC and sclerostin are independently associated with LS BMD Z-scores.

Effect of exercise on telomere length and telomere proteins expression in mdx mice.

In Duchenne muscular dystrophy (DMD), telomere shortening has been postulated to contribute to the failure of regenerative activity promoting the premature senescence of satellite cells. The aim of the present study was to investigate the telomere length and the expression of telomeric repeat-binding factor-1 (TRF1), poly (ADP-ribose) polymerase-1 (PARP1) and mouse telomerase reverse transcriptase (MTERT) in gastrocnemius, tibialis anterior and diaphragm muscles of the murine model of DMD, the mdx mouse and whether a chronic protocol of forced exercise impacts on them. Our results confirmed a telomere shortening in mdx muscles, more evident in the diaphragm, in which exercise induced a greater shortening than in wild-type mice. Moreover, we showed for the first time in mdx an increased TRF1 and PARP1 expression and an augmented activity of MTERT, further enhanced by exercise. These results reinforce the hypothesis that a deregulation of mechanisms involved in telomere length occurs and may pave the way for the test of compounds targeting proteins modulating telomere maintenance as a novel strategy to treat dystrophinopathies.

Health-related quality of life and functional changes in DMD: A 12-month longitudinal cohort study.

In Duchenne muscular dystrophy (DMD) little has been reported on the association between clinical outcome measures and patient health-related quality of life (HRQOL) tools. Our study evaluated the relationship between 12 month changes on the Generic Core Scales (GCS), the Multidimensional Fatigue Scale and the Neuromuscular Module of the PedsQL(TM) with several outcome measures (6 minute walk test, North Star Ambulatory Assessment and timed items) in ambulatory DMD. Ninety-eight ambulatory DMD in a multicentric setting were included in the study. At baseline, the PedsQL(TM) inventories correlated with almost all the functional measures On the Child Self-Report there was a significant decrease between baseline and 12 months on the PedsQL(TM) GCS and its first domain, in parallel with the decrement in the functional outcome measures. Correlation between the 12 month changes on the PedsQL(TM) inventories and functional measures were almost all negligible. Similar results were obtained on the Parent Proxy-Report. In conclusion, PedsQL(TM) correlates with the level of impairment at baseline, but this does not hold true when 12 month changes are considered. Further studies comparing different tools are needed to better elucidate the complexity of the relationship between HRQOL and functional performances.