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02-08-2017 | Rheumatology | News | Article

Body fat associated with poor response to TNF inhibitors in ankylosing spondylitis

medwireNews: Patients with ankylosing spondylitis (AS) and higher fat mass have a worse response to tumor necrosis factor (TNF) inhibitor treatment than those with lower body fat content, study results suggest.

As reported in The Journal of Rheumatology, the research team led by Irene van der Horst–Bruinsma (VU University Medical Center, Amsterdam, the Netherlands) analyzed data from 41 patients with AS, 41.5% of whom were treated with etanercept and the remainder with adalimumab.

Over a median follow-up of 14.3 months, 46.4% of the participants experienced a clinically important improvement in disease activity as indicated by an increase in the Ankylosing Spondylitis Disease Activity Score containing C-reactive protein (ASDAS-CRP) of at least 1.1 points.

Patients with a higher body fat percentage, fat mass index (FMI), or FMI percentile at baseline were significantly less likely to achieve at least a clinically important improvement in ASDAS-CRP than those with lower body fat measurements, with corresponding odds ratios (ORs) of 0.8, 0.7, and 0.9 after adjustment for factors including age, gender, disease duration, and disease-modifying antirheumatic drug use.

Similarly, higher FMI percentile at baseline was significantly associated with a lower chance of achieving a clinically important improvement in disease activity, defined as an increase of 1.1 points or more in the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), among patients with a baseline BASDAI score of at least 4 points (adjusted OR=0.95).

These results support “the concept that adipose tissue, through the release of different bioactive molecules and hormones such as adiponectin, leptin, resistin, TNF, and interleukin 6, can participate in different inflammatory and autoimmune processes,” write the researchers.

“Also, more body fat content could limit the absorption and distribution of the TNF-α blockers administered,” they add.

The team also found that female patients had a significantly higher body fat percentage and FMI at baseline than male patients, at 40.3% versus 27.9% and 11.3 kg/m2 versus 7.0 kg/m2, respectively. And a numerically lower proportion of women than men experienced a clinically important improvement in ASDAS-CRP scores, at 37.5% versus 52.0%.

Higher body fat may therefore “contribute to the lower response rates to treatment in female patients,” says the team, but they note that the difference in outcomes by gender did not reach statistical significance, “probably because of the low number of patients” included in the study.

By Claire Barnard

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