Clinical significance of serum complement factor 3 in patients with type 2 diabetes mellitus

Aims Although serum complement factor 3 (C3) is an acute phase reactant mainly synthesized in the liver, several recent studies have shown high C3 gene expression in adipose tissue (AT). However, the relationship between C3 and AT levels has not been fully clarified in type 2 diabetes mellitus (T2DM) patients. Methods A total of 164 T2DM patients (109 men and 55 women) participated in this cross-sectional study. A computed tomography scan was performed to measure visceral, subcutaneous, and total AT. The correlation between these factors and C3 levels was examined using Pearson's correlation analysis. A multivariate regression model was used to assess an independent determinant associated with C3 levels after adjusting the explanatory variables (i.e., all ATs [visceral, subcutaneous, and total], and clinical features [sex, age, body mass index, waist circumference, glycated hemoglobin, duration of diabetes, systolic blood pressure, diastolic blood pressure, aspartate aminotransferase levels, alanine aminotransferase levels, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, log(triglyceride levels), estimated glomerular filtration rate, and log(high-sensitivity C-reactive protein levels)]). Results Serum C3 levels were correlated with visceral, subcutaneous, and total AT among both men (r = 0.505, p < 0.001; r = 0.545, p < 0.001; r = 0.617, p < 0.001, respectively) and women (r = 0.396, p = 0.003; r = 0.517, p < 0.001; r = 0.548, p < 0.001, respectively). In the multivariate regression model, the association between total AT and C3 levels remained significantly positive (β = 0.490, p < 0.001). Conclusions Serum C3 levels are associated with visceral, subcutaneous, and total AT in T2DM patients. Furthermore, C3 levels seem to be a marker for overall adiposity rather than regional adiposity.