Insulin resistance was more prevalent in patients with rheumatoid arthritis (RA) compared with systemic lupus erythematosus (SLE). Between-group differences could not be explained by traditional insulin resistance risk factors, suggesting that specific RA- and SLE-related mechanisms may instead drive differences in insulin resistance rates. These study findings were published in the Journal of Rheumatology.
While insulin resistance is highly prevalent with both RA and SLE, the specific manifestations of insulin resistance in each condition remains unclear.
Investigators conducted a cross-sectional study to assess the relative prevalence rates of insulin resistance in both disease groups. Patients with RA and patients with SLE were recruited from participating hospitals in Spain. All patients were non-diabetic, and none were taking glucose-lowering drugs or insulin therapy. Insulin resistance was determined using the homeostatic model assessment (HOMA2). Disease activity and cardiovascular (CV) risk factors were captured. Fasting serum samples were taken and used to determine glucose, insulin, and C-peptide levels. Multivariable logistic regression was used to identify differences in insulin resistance indexes between the RA and SLE groups.
The study cohort comprised 186 patients with SLE (mean age, 50 ± 11 years) and 227 patients with RA (52 ± 10 years) (P =.053). Overall, insulin resistance was more prevalent in the RA group compared with the SLE group (25% vs 14%; P =.005). Patients with RA had significantly higher insulin levels than patients with SLE (median [range]: 7.2 [4.4-10.6] vs. 8.0 [5.5-16.40] μU/ml; P =.032). Serum C-peptide levels were also elevated in the RA group, though the difference was not statistically significant (3.05 ± 2.65 vs. 3.57 ± 2.97 ng/ml, P =.060).
In multivariable analyses, HOMA2 indexes related to insulin sensitivity were lower with RA compared with SLE (P =.004). Patients with RA also had higher HOMA2 indexes related to beta cell function (P =.000). After adjustments for disease duration, prednisolone use, and traditional CV risk factors, patients with RA were still more likely to meet the definition of insulin resistance than patients with SLE (odds ratio, 2.15; 95% confidence interval, 2.25-3.69; P =.005). Traditional factors associated with insulin resistance factors had comparable effects on insulin indexes for both disease groups, suggesting that between-group differences may be a result of RA and SLE themselves.
The higher prevalence of insulin resistance with RA “cannot be explained by factors classically associated with [insulin resistance] or disease-related data like [C-reactive protein], disease duration or the use of prednisone,” investigators wrote. “Specific mechanisms underlying each disease may be responsible for these differences.” Further research is necessary to clarify the relationship between RA, SLE, and insulin resistance.
Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Quevedo-Abeledo JC, Sánchez-Pérez H, Tejera-Segura B, et al. Higher prevalence and degree of insulin resistance in patients with rheumatoid arthritis than in patients with systemic lupus erythematosus. J Rheumatol. Published online July 1, 2020. doi: 10.3899/jrheum.200435