“Obesity is an important comorbidity in psoriatic arthritis (PsA). While this is commonly assessed by BMI, BMI is a crude adiposity marker and provides no information on regional body fat distribution. Body composition analysis by MRI allows for visualization of where fat is stored—whether it is deposited in subcutaneous adipose tissue, or “spills over” into more metabolically adverse visceral and ectopic fat compartments, including the liver and muscle. The site of fat storage is important, as greater visceral adipose tissue (VAT) volume and muscle fat infiltration (MFI) are associated with coronary heart disease (CHD) and type 2 diabetes (T2D), and higher liver fat with T2D. To date, there is a scarcity of data regarding body composition in patients with PsA, which could potentially provide useful insights into the increased risk of T2D and cardiovascular disease in patients with this condition.”
For a paper published in Rheumatology (Oxford), Dr. Ferguson and colleagues aimed to characterize the body composition profile of patients with PsA and compare this with that of metabolic disease-free (MDF) controls and those with T2D using MRI, the gold standard in body composition analysis. Participants with PsA recruited from the Immune Metabolic Associations in PsA (IMAPA) study were compared with MDF healthy controls, matched by age, sex, and BMI, and with UK Biobank study participants with T2D recruited from the UK Biobank. The propensity to T2D and CHD for PsA compared with MDF controls was calculated based on these body composition profiles.
Patients With PsA Have Greater Visceral & Liver Fat
The study team observed that patients with PsA have a metabolically adverse body fat distribution, with greater visceral and liver fat than MDF controls, and more comparable to those with T2D. Mean VAT volume was 5.89 L (standard deviation [SD], 2.10 L) in participants with PsA, compared with 4.34 L (SD, 1.83 L) in matched MDF controls. Median percentage of liver fat was also greater in patients with PsA (8.88%; interquartile range [IQR], 4.42%-13.18%) compared with matched MDF controls (3.29%; IQR, 1.98%-7.25%). There were no statistically significant differences in VAT, liver fat, or muscle fat infiltration (MFI) between PsA and type 2 diabetes (Table). Importantly, Dr Ferguson notes that “these findings remained significant after adjusting for BMI, suggesting it is not just simply excess fat, but where this fat is stored in the body, that may be associated with cardiometabolic complications in PsA.”
Of particular note, according to the researchers, the reported body composition in patients with PsA was more strongly associated with T2D, and to a lesser degree, CHD, compared with age-, sex-, and BMI-matched healthy individuals. “We have shown that the body composition in patients with PsA is associated with a 27% greater propensity to CHD and 83% greater propensity to type 2 diabetes compared with body composition in matched MDF controls,” adds Dr. Ferguson.
Weight Loss Important for PsA Management
“To the best of our knowledge, this is the first study to demonstrate that PsA is associated with an adverse body fat distribution with greater visceral and liver fat compared with that of age, sex, and BMI-matched MDF controls and more in line with that of patients with T2Don MRI,” Dr. Ferguson notes. “Such findings, in turn, predict greater propensity to CHD and especially T2D. Our findings suggest that weight loss should be considered a core component of PsA disease management to lessen cardiometabolic risk in this patient population.”
Dr. Ferguson and colleagues note that there is now a need for further research focused on large-scale, randomized, placebo-controlled trials to confirm that weight loss improves body composition and outcomes in patients with PsA, both in minimizing disease activity and in lessening diabetes and heart disease risk, as suggested by prior studies. “Subsequent studies should also include a larger number of patients with PsA, including those with varying disease activity and biologic agent use.”