IR sensitivity lower, β cell function higher in RA vs SLE patients

Patients with rheumatoid arthritis (RA) have lower insulin resistance (IR) sensitivity and higher β cell function than those with systemic lupus erythematosus (SLE), reveals a study.

“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,” the authors said.

A cross-sectional study was carried out in 413 patients without diabetes (227 with RA and 186 with SLE), analysing glucose, insulin, and C-peptide serum levels of the participants, as well as IR by the homeostatic model assessment (HOMA2).

The authors performed a multivariable regression analysis to assess the differences in IR indexes between SLE and RA patients, as well as to determine if IR risk factors or disease-related characteristics were differentially related to IR in both populations.

Multivariable analysis revealed an upregulated insulin:C-peptide molar ratio in RA patients compared to SLE patients (β, 0.009, 95 percent confidence interval [CI], 0.005–0.014; p<0.001). Furthermore, HOMA2 indexes associated with insulin sensitivity (HOMA2-%S) were lower (β, –27, 95 percent CI, –46 to –9; p=0.004) and β cell function (HOMA2-%B) demonstrated higher IR indexes (β, 38, 95 percent CI, 23–52; p<0.001) in RA than in SLE patients.

RA patients were also more likely to fulfil the definition of IR than those with SLE (odds ratio, 2.15, 95 percent CI, 1.25–3.69; p=0.005). The size effect of IR factors on IR indexes was equal in both diseases.