C3 and C4 are strongly related to adipose tissue variables and cardiovascular risk factors

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>In several reports, C3 and C4 have been linked to diabetes and cardiovascular disease (<jats:styled-content style="fixed-case">CVD</jats:styled-content>). Here, we investigate this link and the degree of C3 activation in elderly individuals.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>In this study, C3 and C4 and the activation fragment C3a‐desArg were analysed in 1016 subjects aged 70, in which blood pressure, lipid variables and fasting blood glucose were assessed.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>C3 levels were related to all the investigated classical cardiovascular risk factors and the metabolic syndrome (<jats:styled-content style="fixed-case">BMI</jats:styled-content>, waist circumference, fat distribution, blood pressure, blood glucose levels, <jats:styled-content style="fixed-case">TG</jats:styled-content>) except total cholesterol and <jats:styled-content style="fixed-case">LDL</jats:styled-content> cholesterol in a highly significant fashion (Spearman up to 0,5; <jats:italic>P</jats:italic> < 0·0001). C4 and C3a‐desArg were associated in the same fashion but less significantly, while the ratios C4/C3 or C3a‐desArg/C3 were not, indicating that the association was not directly related to complement activation. The levels C3 and to a lesser degree C4 and C3a‐desArg were associated particularly with <jats:styled-content style="fixed-case">CRP</jats:styled-content>, but also with E‐selectin and <jats:styled-content style="fixed-case">ICAM</jats:styled-content>‐1. In addition, C3 and C4 levels were shown to decline significantly in 15 female subjects enrolled in a weight‐reduction programme over 4 months.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>A strong relation between C3, C4 and C3a‐desArg levels, adipose tissue and risk factors of <jats:styled-content style="fixed-case">CVD</jats:styled-content> was established. The data support that the adipose tissue produces complement components and generates initiators of inflammation, such as C3a and C5a, able to trigger a cyto/chemokine response, in proportion to the amount of adipose tissue. This corroborates the concept that complement contributes to the low‐grade inflammation associated with obesity.</jats:p></jats:sec>