Abstract
Objective Since insulin resistance (IR) is highly prevalent in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), we aimed to determine whether differences in IR exist between the two conditions.
Methods We conducted a cross-sectional study comprising 413 subjects without diabetes (186 with SLE and 227 with RA). Glucose, insulin, and C-peptide serum levels, as well as IR by the homeostatic model assessment (HOMA2) were studied. A multivariable regression analysis was performed to evaluate the differences in IR indexes between patients with SLE and RA, as well as to determine if IR risk factors or disease-related characteristics are differentially associated with IR in both populations.
Results The insulin:C-peptide molar ratio was upregulated in patients with RA compared to patients with SLE (β 0.009, 95% CI 0.005–0.014, P < 0.001) after multivariable analysis. HOMA2 indexes related to insulin sensitivity (HOMA2-%S) were found to be lower (β –27, 95% CI –46 to –9, P = 0.004) and β cell function (HOMA2-%B) showed higher IR indexes (β 38, 95% CI 23–52, P < 0.001) in RA than in SLE patients after multivariable analysis. Patients with RA more often fulfilled the definition of IR than those with SLE (OR 2.15, 95% CI 1.25–3.69, P = 0.005). The size effect of IR factors on IR indexes was found to be equal in both diseases.
Conclusion IR sensitivity is lower and β cell function is higher in RA than in SLE patients. The fact that traditional IR factors have an equal effect on IR in both SLE and RA supports the contention that these differences are related to the diseases themselves.
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