Background/Purpose: Patients with systemic lupus erythematosus (SLE) have reduced physical activity and frequently complain of fatigue. Exercise reduces fatigue in patients with SLE; however, the mechanism of the exercise-induced reduction in fatigue is unknown. Exercise also improves muscle quality, particularly by reducing intermuscular adipose tissue (IMAT). To date, no study has evaluated the presence of IMAT in patients with SLE. Thus, in this study, we hypothesize that IMAT is increased in patients with SLE, and it is associated with patient-reported physical activity and fatigue.

Methods: In a cross-sectional study, we evaluated 51 participants (23 patients with SLE and 28 controls). IMAT was evaluated in the calf muscles using sequential T1-weighted and Dixon magnetic resonance images (MRI). Patient-reported physical activity and fatigue were evaluated using visual analog scales.

Results: Patients with SLE and controls were similar in terms of age, sex, race, body mass index (BMI), and renal function (Table 1). Corticosteroid and antihypertensive medication use was higher in patients with SLE than in controls. IMAT accumulation, expressed as the ratio of IMAT area to total muscle size, was significantly higher in patients with SLE than in controls (7.92%, 4.51-13.39%, vs. 2.65%, 1.15-4.61%, median, IQR, p< 0.001, Figure 1). These differences between the groups remained significant after adjustment for age, race, and BMI. Corticosteroid use may affect the accumulation of IMAT, however, in patients with SLE  IMAT accumulation did not differ significantly among corticosteroid users and non users p=0.48. Patient-reported fatigue and physical activity were higher and lower, respectively, in patients with SLE than in controls (Table 1). IMAT was positively correlated with patient-reported fatigue (rho=0.52, p< 0.001) and inversely correlated with patient-reported walking distance (rho=-0.60, p< 0.001). Physical activity may affect IMAT accumulation, however, the difference in IMAT between controls and patients with SLE remains significant after adjusting for the reported physical activity (p=0.015).

Conclusion: Patients with SLE have greater IMAT accumulation than controls. Increased IMAT is associated with greater fatigue and lower physical activity. Future studies should evaluate the effectiveness of interventions that improve muscle quality to alleviate fatigue in patients with SLE.

Table 1

Figure 1

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/intermuscular-adipose-tissue-in-patients-with-systemic-lupus-erythematosus/