Obesity is the main determinant of insulin resistance more than the circulating pro-inflammatory cytokines levels in rheumatoid arthritis patients.

BACKGROUND: Systemic blockade of TNF-α in Rheumatoid arthritis (RA) with insulin resistance (IR) seems to produce more improvement in insulin sensitivity in normal weight patients with RA than in obese patients with RA, suggesting that systemic-inflammation and obesity are independent risk factors for IR in RA patients.

OBJECTIVES: To evaluate the insulin resistance in: normal weight patients with RA (RA NW), overweight patients with RA (RA OW), obese RA patients (RA OB), and matched control subjects with normal weight (NW) and obesity (OB); and its association with major cytokines involved in the pathogenesis of the disease.

METHODS: Assessments included: body mass index (BMI), insulin resistance by HOMA-IR, ELISA method, and enzymatic colorimetric assay.

RESULTS: Outstanding results from these studies include: (1) In RA patients, IR was well correlated with Body Mass Index (the higher the BMI, the higher IR), but not with levels of serum cytokines. In fact, levels of cytokines were similar in all RA patients, regardless of being obese, overweight or normal weight (2) IR was significantly higher in RA NW than in NW (3) No significant difference was observed between IRs of RA OB and OB (4) As expected, levels of circulating cytokines were significantly higher in RA patients than in OB.

CONCLUSIONS: Obesity appears to be a dominant condition above inflammation to produce IR in RA patients. The dissociation of the inflammation and obesity components to produce IR suggests the need of an independent therapeutic strategy in obese patients with RA.