Overweight, obesity tied to higher degree of synovitis in RA
Patients with rheumatoid arthritis (RA) who are overweight or obese have a higher degree of histologically-proven follicular synovitis. Furthermore, body mass index (BMI) appears to impact response to treatment in these patients, according to a study presented at the annual meeting of the ACR/ARHP* held in San Diego, California, US.
“Overweight and obesity are associated with higher degree of histologically-proven synovitis in RA patients from the time of disease onset to the achievement of stable remission influencing the response rate to [treat-to-target] regimen,” said study lead author Dr Stefano Alivernini from the Catholic University of the Sacred Heart, Rome, Italy, and colleagues.
The study population comprised 125 individuals with RA, of whom 57 were DMARD**-naïve, 43 were inadequate responders to methotrexate, and 25 were considered clinically stable and in ultrasound remission while on treatment with methotrexate and TNF***-inhibitors (DAS# <1.6). They were grouped according to BMI at baseline, ie, normal weight (BMI <25 kg/m2), overweight (BMI 25–30 kg/m2), and obese (BMI >30 kg/m2).
All patients underwent synovial tissue biopsy and immunochemistry testing for CD68+, CD21+, CD20+, and CD3+. Treatment-naïve patients were treated as per the treat-to-target strategy and were followed for 12 months.
Bar the age difference (DMARD-naïve patients were younger than methotrexate inadequate responders and patients in remission [53.5, 59.5, and 57.2 years, respectively]), other demographic, immunologic, and clinical characteristics were similar between the patients. Overweight/obesity rate was also comparable between the DMARD-naïve, methotrexate inadequate responders, and patients in remission (59.6, 58.2, and 56.0 percent, respectively).
Among DMARD-naïve patients, the incidence of follicular synovitis was higher among obese compared with normal-weight patients (78.6 percent vs 39.1 percent; p=0.02). [ACR/ARHP 2017, abstract 1898]
DMARD-naïve patients with a BMI >35 kg/m2 had higher histological scores for lining and sublining CD68+ (p=0.03 and 0.01, respectively), sublining CD20+ (p=0.005), sublining CD3+ (p=0.003), and lining and sublining CD21+ cells (p<0.001 and p=0.003, respectively) compared with normal-weight DMARD-naïve patients.
There was also a direct correlation between BMI and synovial aggregate grade (R=0.311; p=0.02) and histological scores for CD21+, CD20+, and CD3+ cells (R=0.344; p=0.01, R=0.295; p=0.03, and R=0.256; p=0.05, respectively) among DMARD-naïve patients.
Response to treatment was worse among overweight/obese DMARD-naïve patients compared with normal-weight ones at 6 and 12 months follow-up (p<0.05 for both time frames).
In contrast, BMI did not appear to affect the extent of synovial inflammation in methotrexate inadequate responders.
Patients in remission had lower DAS and inflammatory markers (namely erythrocyte sedimentation rate and C-reactive protein) compared with DMARD-naïve patients (p<0.001 for each). However, even among patients in stable remission, those who were overweight or obese had higher levels of residual synovial inflammation as compared with normal-weight patients (sublining CD68+ cells; p=0.001, lining CD20+ cells; p=0.04, and lining and sublining CD3+ cells; p=0.04 and 0.05, respectively).
“[M]ultiple studies confirm that obesity is a risk factor associated with the development of RA,” said Alivernini.
“Based on these results, we believe that it’s important to track patients’ BMI in clinical practice, since there is a tight relation between the BMI category of RA patients and their chance of a good clinical response to treat-to-target. Since body weight is a modifiable factor, a standardized, multidisciplinary approach to help the patient achieve weight loss should be advised to increase disease control,” he concluded.