Background/Purpose: Targeted blockade of tumour necrosis factor (TNF) has been a major therapeutic advance in the treatment of rheumatoid arthritis (RA), psoriatic arthritis (PsA) and ankylosing spondylitis (AS). TNF (or “cachectin”, as it was initially called) may be responsible for the weight loss observed in patients with active RA via its inhibitory effect on the enzyme lipoprotein lipase which regulates fat metabolism. “Rheumatoid cachexia” may be an important contributor to morbidity and mortality in RA. Low body weight in RA patients was associated with increased disability and radiological progression of joint damage. Other factors are also important in RA-related weight loss, for example lack of physical activity due to joint pain and restriction of movement, or anorexia from a combination of ill-health and medications. The effect of corticosteroids (CS) on body weight is an important confounder. TNF inhibition has been associated with variable effects on body weight in patients with inflammatory arthritis.   We sought to determine if TNF inhibition (TNFi) resulted in weight gain in patients with inflammatory arthritis.

Methods: In this retrospective cohort study, the following data were obtained for all patients initiated on a biologic disease modifying anti-rheumatic drug (bDMARD) through the Mid-North Coast Arthritis Clinic (MNCAC) for inflammatory arthritis up to Jan 25, 2012: age, sex, type of inflammatory arthritis, initial bDMARD, body weight at 3 initial consecutive time-points, CRP, ESR, Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) or Disease Activity Score-28 joints (DAS28) as appropriate, and oral corticosteroid dose (mg/d). Change in body weight over 3 time-points following commencement of the initial bDMARD was calculated. Regression modeling (mixed linear models) was undertaken to ascertain the effect of parameters (age, sex, disease activity, bDMARD, daily dose of oral corticosteroid) on body weight.

Results: N=301 patients were initiated on a bDMARD. N=98 were excluded for the following reasons (insufficient time on treatment for 3 weighs, n=55; incomplete data, n=32; intentional weight loss, n=9; refused weighing, n=1; failure to commence therapy, n=1). The remaining 203 patients were included and had commenced the following bDMARDS: 184 TNFi, 8 tocilizumab, 8 abatacept, 3 rituximab. Patients initiated on a TNFi gained weight at the rate of 0.03 (95 CI: 0.013-0.035, p<0.001) kg per week, independent of corticosteroid dose and disease activity. There was no change in weight in those initiated on a non-TNFi bDMARD (n=19).

Conclusion: TNF inhibition resulted in minor weight gain. This side effect is often forgotten. It is possible that weight loss may be predictive of clinical response to TNFi. This needs to be investigated in a larger prospective study

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/tumour-necrosis-factor-inhibition-is-associated-with-weight-gain-in-patients-with-inflammatory-arthritis/