The aim of this study was to explore the association between the serum concentration of complement component 3 (C3) and a variety of metabolic parameters. The study involved 125 patients in our outpatient clinic. Anthropometric and clinical laboratory data were collected and statistical associations between the serum concentration of C3 and other parameters were evaluated in a cross-sectional as well as a prospective manner. A group of male patients with metabolic syndrome (Mets, n=35) were characterized by marked increase in serum concentrations of C3, body mass index (BMI), waist circumference, hemoglobin (Hb) A1c, insulin resistance (HOMA-IR), triglyceride, uric acid, urinary protein, and Hb. In a one-way analysis of variance of all subjects, the serum concentration of C3 was significantly elevated as the number of items of complying with the Mets diagnostic criteria increased. In 60 of 125 patients who did not have diabetes and were given anti-lipogenetic medication, the serum concentration of C3 showed significant positive associations with serum levels of CH50, insulin, HOMA-IR, total cholesterol, hematocrit, LDL-c, C4, Hb, triglyceride, BMI, and albumin. In a prospective follow-up evaluation (n=35), there was a significant positive association between DeltaC3 (the second concentration of serum C3 minus the first concentration of serum C3)and DeltaHOMA-IR (the second concentration of HOMA-IR minus the first concentration of HOMA-IR). In conclusion, in Japanese patients, there is evidence implicating C3 concentration as a marker of Mets coinciding with insulin resistance.
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