Background/Purpose: In patients with rheumatoid arthritis(RA), elevated resting energy expenditure(REE) is associated with rheumatoid cachexia and protein catabolism driven by pro-inflammatory cytokines. IR is also associated with elevated REE in adults without RA, independent of inflammation. Given the high prevalence of IR in RA, our goal was to investigate the association between IR and REE in patients with RA.

Methods: 35 individuals meeting the 2010ACR/EULAR criteria for RA and 17 non-RA controls comparable in age, sex and race were selected. Body composition was determined by dual energy x-ray absorptiometry (DEXA). REE was measured using indirect calorimetry. Insulin sensitivity was measured using the Matsuda index. Linear regression model was used to study the relationship among REE, insulin sensitivity and CRP, as well as an interaction between IS and CRP. Statistical significance is defined by a p-value < 0.05.

Results: RA and non-RA controls had comparable body mass index, total fat free mass index, CRP and REE levels. Insulin sensitivity was lower in the RA group (median=2.9, IQR=5.4) compared to the non-RA group (median=5.9, IQR=4.1). The median DAS28-CRP among individuals with RA was 1.8 (IQR=1.7). Among individuals with RA, we found a statistically significant relationship between REE and CRP levels [R²= 41.0 %, adjusted R²=33.9%, estimate coefficient (SE)= 46.7 (13.7), p=0.0022], while insulin sensitivity was not significantly associated with REE after adjusting for CRP level [estimate (SE)=-57.4 (43.3), p=0.256]. Among individuals with RA, there was also no significant interaction between IR and CRP [estimate (SE)=-40.0976(22.746), p=0.146]. In the non-RA control group, neither insulin sensitivity nor CRP level were significantly associated with REE.

Conclusion: CRP was significantly and independently associated  with REE among RA individuals, but not non-RA controls. IS was not independently related to REE in either group. These results suggest that, in RA, inflammation may be a common antecedent leading to both elevated REE and insulin resistance.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/role-of-insulin-resistance-and-inflammation-on-resting-energy-expenditure-in-patients-with-rheumatoid-arthritis/