Objectives It has been suggested that resistance to insulin action is a feature that accompanies rheumatoid arthritis (RA), a disease where chronic inflammation predominates and classical triggers for insulin resistance (IR) like obesity and diabetes are absents. However, data regarding characterization of RA features associated with this insulin resistance (IR) are lacking. The aim of this study was to investigate how sensitivity to insulin and markers of beta cell dysfunction (proinsulin processing metabolites) are expressed in RA.
Methods 101 non-diabetic RA patients and 99 non-diabetic sex and age-matched controls were included in this study. Insulin sensitivity function through homeostatic model assessment (HOMA2), and beta cell secretion through insulin, split and intact proinsulin, and C-peptide were assessed in both groups. We performed multiple regression analysis to compare IR between groups and to explore the relation between RA features and IR. Data were adjusted for glucocorticoids intake and for IR classical risk factors.
Results RA patients compared to controls show higher HOMA-IR (logHOMA-IR, beta coefficient, 0.40 [95% CI 0.20-0.59], p=0.00). When this data was adjusted for glucocorticoids intake, non-on corticosteroid patients maintained a higher IR index (beta coef. 0.14 [95% CI 0.05-0.24], p=0.00). Current prednisone treatment was not associated with higher IR in the patients’ intragroup comparison (beta coef. 0.56 [1.13-1.19], p=0.22). Insulin processing signaling in RA patients showed impaired features via an elevated intact proinsulin levels (beta coef. 3.13 [0.81-5.44] pMol/L, p=0.03 for the comparison between patients and controls). Split proinsulin levels were also higher in RA patients (beta coef. 13.7 pmol/L [3.57-9.40], p=0.00) even adjusting for prednisone intake (beta coef. 2.66 pmol/L [95%CI 1.62-5.95] for non steroids RA patients when compared to controls). In multiple regression analysis, RA features (disease duration, rheumatoid factor, erythrocyte sedimentation rate, C-reactive protein, disease activity through HAQ and DAS28 scores, and current non-biologic disease modifying antirheumatic drug), when adjusted for sex, age and body mass index, were not associated with IR or insulin propeptides.
Conclusions Beta cell signaling is impaired in non-diabetic and non-corticoids RA patients.
Disclosure of Interest None Declared
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