Metabolic and structural skeletal muscle health in systemic lupus erythematosus related fatigue: a multi-modal magnetic resonance imaging study

Objective: This study aimed to investigate the potential structural and metabolic role of skeletal muscle in SLE related fatigue. Methods: A case control, multi-modal MRI study was conducted. Cases were inactive SLE patients who reported chronic fatigue. Controls were age/sex matched healthy members of the general population. Participants were clinically characterised and then underwent a 3T whole body MRI scan. Resting and dynamic 31 Phosphorous Magnetic Resonance Spectroscopy (MRS) of the calf muscles was applied from which phosphocreatine recovery half time (PCr), a marker of mitochondrial dysfunction, was computed. In addition, microstructural sequences (T1-weighted anatomical images, T2 mapping and diffusion tensor imaging) were acquired. Descriptive statistics evaluated group differences and within case physical fatigue correlations were explored. Results: Of the 37 recruits (mean age= 43.8 years, 89.2% female), cases (n=19) reported higher levels of physical fatigue, pain, depression and sleep disturbance compared to the control group (p<0.0001). PCr was greater (p=0.045) among cases (33.0+/-9.0s) compared to controls (27.1+/-6.6s). No micro-structural group differences were observed. Within cases, physical fatigue did not correlate with PCr (r=-0.28, p=0.25). Conclusion: We report preliminary data evidencing greater skeletal muscle mitochondrial dysfunction among fatigued SLE patients compared to healthy controls.