Background Systemic lupus erythematosus (SLE) is an autoimmune disease with a wide range of clinical manifestations and most cases of SLE occur in women. There is strong evidence on the relationship between physical activity and the primary prevention of chronic health problems in women. The metabolic syndrome is defined by a clustering of atherosclerotic cardiovascular disease risk factors, characterized by central obesity, glucose intolerance, hypertension, dyslipidemia, insulin resistance (IR) and a systemic proinflammatory and procoagulating state.
Objectives The aim of this study was to investigate the impact of metabolic syndrome and physical activity in clinically quiescent SLE patients, especially emphasis on the interaction of IR, bone metabolism, and inflammation.
Methods Seventy five female clinically quiescent SLE patients attending outpatient clinics at Taichung Veterans General Hospital were enrolled in this study. Thirty age-matched healthy females from the local community served as controls. Metabolic syndrome was based on the National Cholesterol Education Program (NCEP/ATP III) definition. The homeostasis model assessment (HOMA) was used to evaluate the status of IR. Estimates of energy expenditures represented by total activity calorie, physical activity calorie, total activity calorie per body weight, and physical activity calorie per body weight of studied patients were assessed using the RT3 tri-axial accelerometer in a seven-day period. Bone mineral density (BMD) and body composition were measured by dual energy X-ray absorptiometry. Electrochemiluminescence immunoassay was performed to measure bone metabolism markers including C-terminal crosslinking telopeptide of type I collagen, parathyroid hormone, type I procollagen N-terminal propeptide, and osteocalcin. Serum levels of inflammatory markers were assessed using the Bio-Plex Human Cytokine 17-Plex panel in combination with the Bio-Plex Suspension Array System.
Results All of the patients were non-smokers and performed regular daily activities. The high prevalence of metabolic syndrome was present in this study. About 36% of studied patients were considered IR with a value of HOMA IR greater than 2.0. Incidence rate was also significantly higher in SLE patients with IR than SLE patients without IR. SLE patients with IR tended to have higher estimates of energy expenditure compared to those in SLE patients without IR. However, there was no statistically significant difference in physical activity between patients stratified by HOMA IR. About 53% of studied patients were considered osteopenia or osteoporosis. Osteopenia or osteoporosis was more prevalent in SLE patients with IR than SLE patients without IR. However, total BMD and the BMD at the spine and femoral neck were not significantly different between SLE patients with and without IR. SLE patients regardless of IR had significantly lower circulating levels of osteocalcin than healthy subjects. With respect to inflammation, SLE patients with IR had significantly higher serum levels of monocyte chemoatractant protein-1 and macrophage inflammatory protein-1β than healthy subjects.
Conclusions Although SLE patients in this study were considered clinically quiescent, a possible link between insulin resistance, bone metabolism, and inflammation exists.
Disclosure of Interest None Declared