Binding of adiponectin and C1q in human serum, and clinical significance of the measurement of C1q-adiponectin / total adiponectin ratio

摘要

Objective: Adiponectin and C1q have similar sequences, exist abundantly in blood, and are produced by adipose tissues. The aim of this study was to examine whether adiponectin and C1q form protein-complex in blood and to know the clinical significance of the C1q-adiponectin (C1q-APN) complex in serum. Methods: The direct interaction between adiponectin and C1q was investigated by far western blotting and co-immunoprecipitation. The relationship between serum C1q-APN and various clinical features was analyzed in 329 Japanese men who underwent health check-up, including measurements of visceral (VFA) and subcutaneous fat area (SFA) by computed tomography (Victor-J study). Results: Adiponectin bound to C1q in vitro and C1q-APN complex existed in human blood. C1q-APN complexes were identified in high- and middle-molecular weight forms of adiponectin in human serum by gel-filtration chromatography. Stepwise multiple regression analysis identified body mass index, VFA and SFA as significant determinants of serum C1q-APN level. Serum C1q-APN/Total-APN ratio correlated positively with cardiovascular risk factor accumulation in subjects with VFA ≥ 100 cm2. Conclusions: These results indicate that high- and middle-molecular forms of adiponectin partly consist of adiponectin-complex with other proteins including C1q and that the blood C1q-APN/Total-APN ratio may serve as a biomarker of the metabolic syndrome in general male subjects.