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Serum complement C3 strongly correlates with whole-body insulin sensitivity in rheumatoid arthritis
Francesco Ursini1, Salvatore D'Angelo2, Emilio Russo3
1Department of Health Sciences, University of Catanzaro "Magna Graecia", Catanzaro, Italy. francesco.ursini@yahoo.it.
Insights
Rheumatoid arthritis patients show a strong link between inflammation and insulin resistance. Complement C3 levels correlate with insulin sensitivity, aiding in identifying at-risk individuals.
Area of Science:
- Rheumatology
- Endocrinology
- Immunology
Background:
- Rheumatoid arthritis (RA) is associated with increased cardiovascular disease (CVD) risk.
- This risk stems from a combination of traditional risk factors, like insulin resistance, and chronic inflammation.
- Understanding the interplay between inflammation and metabolic health in RA is crucial for CVD prevention.
Purpose of the Study:
- To investigate the relationship between inflammatory markers and insulin sensitivity in patients with rheumatoid arthritis.
- To identify specific inflammatory indicators that correlate with impaired insulin sensitivity.
Main Methods:
- Forty non-diabetic rheumatoid arthritis patients were enrolled.
- Standard anthropometric measurements, laboratory tests, and oral glucose tolerance tests (OGTT) were performed.
- Insulin sensitivity index (ISI) was calculated using dynamic glucose and insulin values from the OGTT.
Main Results:
- Insulin sensitivity index (lnISI) showed inverse correlations with age, BMI, waist circumference, systolic blood pressure, ESR, CRP, and complement C3.
- In non-obese patients, lnISI correlated with age, BMI, CRP, and C3.
- Multiple regression analysis revealed that BMI and complement C3 significantly predicted lnISI, explaining 38.2% of the variance. In non-obese patients, only C3 was a significant predictor (32.2% variance).
- A complement C3 cutoff of 1.22 g/L effectively identified insulin-resistant RA patients (67% sensitivity, 79% specificity).
Conclusions:
- Complement C3 is a significant correlate of insulin sensitivity in rheumatoid arthritis patients.
- This association holds true for both obese and non-obese individuals.
- Complement C3 may serve as a valuable biomarker for assessing insulin resistance in RA.
Objectives:
Rheumatoid arthritis (RA) is characterised by an excess of cardiovascular diseases (CVD) risk, attributable to a synergy between under-diagnosed traditional risk factors (i.e. insulin resistance) and inflammatory disease activity. The aim of the present study was to evaluate the correlation between inflammatory measures and insulin sensitivity in RA patients.
Methods:
Forty non-diabetic RA patients (19 males) were recruited. All patients underwent anthropometric measurements, laboratory evaluation and oral glucose tolerance test (OGTT). Insulin sensitivity index (ISI) was calculated with the equation proposed by Matsuda et al., from dynamic values of glucose and insulin obtained during OGTT.
Results:
In the univariate analysis, lnISI correlated inversely with age, BMI, waist circumference, sBP, ESR, lnCRP and complement C3, but not with disease duration, dBP or complement C4. In non-obese patients (BMI <30 kg/m2, n=28), only age, BMI, lnCRP and C3 maintained their correlation with lnISI. In a stepwise multiple regression using lnISI as the dependent variable and BMI, age, lnCRP and complement C3 as predictors, only BMI and C3 entered the equation and accounted for 38.2% of the variance in lnISI. In non-obese patients, only C3 entered the regression equation, accounting for 32.2% of the variance in lnISI. Using a ROC curve, we identified the best cut-off for complement C3 of 1.22 g/L that yielded a sensitivity of 67% and a specificity of 79% for classification of insulin resistant patients.
Conclusions:
In RA patients, complement C3 correlates strongly with insulin sensitivity, in both obese and non-obese individuals.
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