Studies have shown that fatigue can be one of the most debilitating symptoms of systemic lupus erythematosus (SLE). It can lead to diminished QOL, disruption of sleep, mental anguish, and a lack of physical activity. The cause of fatigue in patients with SLE is unknown. However, it has been speculated that there is a causality dilemma (ie, a lack of physical activity causes fatigue, and fatigue causes a lack of physical activity).
Intramuscular adipose tissue (IMAT) accumulates due to inactivity and has been associated with the increased onset of inflammation. Despite a possible correlation between symptoms, IMAT has not been characterized in patients with SLE.
Jorge Luis Gamboa, MD, and colleagues sought to remedy this gap in knowledge by developing a cross sectional study on IMAT frequency in patients with SLE for a study published in Lupus Science and Medicine. “In this study, IMAT was evaluated using MRI, an important tool to quantify the distribution of ectopic adipose tissue,” Dr. Gamboa said. “We hypothesized that IMAT is increased in patients with SLE compared with controls and it is associated with markers of inflammation. In a hypothesis-generating aim, we also evaluated the association between IMAT and decreased physical activity/increased fatigue in our cohort
of patients.”
IMAT Significantly Higher in Patients With SLE
The cross-sectional study divided patients into two groups: control patients (N=28) who did not have a history of SLE or autoimmune diseases and patients with SLE (N=23) who met the criteria for diagnosis according to the 2017 American College of Rheumatology classification criteria. Participants were considered similar in terms of age, sex, race, BMI, and renal function.
In the study, IMAT accumulation was expressed as the percentage of IMAT area to muscle area; MRI imaging was used to determine this. The calf area of the leg was examined accordingly. IMAT accumulation was significantly higher in the group of patients with SLE compared with the patients in the control group (7.92%
[95% CI, 4.51% to 13.39%] vs 2.65% [95% CI, 1.15% to 4.61%]; P<0.001). No difference was observed in the cross-sectional area of the muscles between the two groups.
In terms of normalized subcutaneous adipose tissue in the cross-sectional area of the leg, the percentage was higher in patients with SLE (32.95%; 95% CI, 27.96% to 41.60%) versus controls (27.06%; 95% CI, 22.97% to
30.91%; P=0.02). However, once this percentage was adjusted for age, sex, race, and BMI,the difference was not significant.
Patients with SLE had significantly higher self-reported fatigue compared with those in the control group (49mm [28mm-63mm]vs 2mm [0mm-5mm] on a 100mm scale; P<0.001). Patients with SLE also had significantly lower comfortable walking distances compared with those in the control group (1.1 miles [0.2-2.0 miles] vs 5.0 miles [3.0-5.3 miles]; P<0.001).
Futures Studies on Patient Interventions Are Warranted
In pointing out a possible correlation between physical activity and reduced IMAT, Dr. Gamboa and colleagues wrote, “Overall, participants who could walk greater than the median comfortable walking distance had lower IMAT accumulation. Physical activity may affect IMAT accumulation, however, the difference in IMAT accumulation between controls and patients with SLE remained significant after adjusting for the reported walking distance (P=0.02; Figure).”
Although the study did not conclude with any recommendation for the increase of physical activity in patients with SLE, it did suggest that future studies should be conducted to evaluate whether interventions, like increased physical activity, could reduce IMAT and perhaps have a positive impact on patients with SLE.
