Relationship between serum C3 levels and traditional risk factors for myocardial infarction.

Serum C3, a complement component produced by macrophages, the liver and the adipose tissue, is associated with the risk of myocardial infarction in men. This study was performed to ascertain the relationships between serum C3 and traditional risk factors in an unselected population sample.A random population of 1,068 subjects (537 men and 531 women, 23 to 90 years old) was examined for risk factor assessment. Serum C3 was measured by nephelometry. C3 was independently associated with body mass index (P < 0.0005, especially in women), LDL-cholesterol (P = 0.0014 in men and 0.0215 in women), systolic blood pressure (P < 0.05) and, in women, with triglycerides (P = 0.0133) and blood glucose (P = 0.0383), as assessed by multivariate analysis (multiple linear regression). The overall R2 were 0.07 and 0.21 for men and women, respectively. Women over 50 years of age had significantly higher C3 levels, LDL-cholesterol and body mass index than younger women. The correlation of C3 with LDL-cholesterol was present after the age of 40 in men, and 2 decades later in women.These data show that serum C3 correlates with a cluster of conventional risk factors for myocardial infarction resembling insulin resistance. Such correlations may be either independent of, or mediated by the development of coronary atherosclerosis.