Exploring 31P-MRS changes in skeletal muscle of riboflavin-responsive lipid storage myopathy patients: Clinical value and implications

Abstract

Objective: To investigate the characteristics of skeletal muscle changes observed through 31phosphorus- magnetic resonance spectroscopy (31P-MRS) in patients with riboflavin-responsive lipid storage myopathy (RR-LSM), and to explore the clinical value of these changes in assisting the diagnosis and evaluating the efficacy of LSM treatment.

Methods: A total of 12 RR-LSM patients underwent 31P-MRS scans pre- and post-treatment, alongside 11 healthy controls. Spectral data were analyzed to derive key metabolite levels, including inorganic phosphate (Pi), phosphocreatine (PCr), and adenosine triphosphate (ATP). Ratios such as Pi/ATP, PCr/ATP, and Pi/PCr were calculated, alongside values for intracellular pH (pHint), adenosine diphosphate (ADP), and phosphorylation potential (PP). Comparative analyses were conducted among three groups: RR - LSM patients before treatment, RR - LSM patients after treatment, and the control group.

Results: Pre-treatment, RR-LSM patients exhibited significantly lower levels of PCr, PCr/ATP, and PP compared to controls (P < 0.05). Conversely, elevated levels of Pi/PCr and ADP were observed (P < 0.05). No significant differences were noted in Pi, Pi/ATP, and intracellular pH (pHint) between groups (P > 0.05). Post-treatment, significant increases in PCr, PCr/ ATP, and PP were observed (P < 0.05), while ADP levels decreased markedly (P < 0.05). However, Pi, Pi/ATP, Pi/PCr, and pHint remained unchanged after treatment (P > 0.05). Post-treatment ADP and 1/PP remained elevated compared to controls (P<0.05).

Conclusion: Our study identifies distinct metabolic alterations in RR-LSM patients, particularly in PCr, PCr/ATP, PP, Pi/PCr, and ADP levels, which serve as valuable biomarkers for diagnosis in RR-LSM. The observed improvements in PCr and related ratios post-treatment highlight the utility of 31P-MRS in tracking metabolic recovery and evaluating the efficacy of riboflavin therapy. These findings underscore the potential of 31P-MRS as a non-invasive tool for clinical management of RR-LSM.