A Novel ELISA System for Measuring Modified LDL-Adiponectin Complex.

AIM: Adiponectin is an anti-diabetic and anti-atherogenic protein secreted primarily from adipose tissue. Adiponectin and modified LDL (mLDL) form a complex to modulate their biological activity. To elucidate the significance of the complex formation, we analyzed its effects on vascular tissue and developed and verified novel quantifying methods for adiponectin. METHODS: To study the significance of the mLDL-adiponectin complex (MAC) formation, we used the wire-myography method on rat mesenteric artery. We developed a method to measure MAC by using LOX-1 as the capture protein and anti-adiponectin antibody for detection. We compared serum MAC levels between hemodialysis patients and control subjects. RESULTS: Administering mLDL alone to rat mesenteric artery impaired endothelium-dependent vasorelaxation, whereas simultaneously administering adiponectin with mLDL protected rat mesenteric artery from the mLDL-induced impairment of vasorelaxation. This finding indicates MAC formation prevents endothelium from mLDL-induced dysfunction in tissue. Using our novel ELISA for MAC, we found that MAC was increasingly detectable depending on the doses of mLDL and adiponectin in vitro. In serum, hemodialysis patients showed a significantly higher ratio of MAC-high patients (higher than the median level of MAC) than did healthy controls. Furthermore, the MAC-high hemodialysis group had lower mLDL activity measured as LOX-1 ligand containing apoB. CONCLUSION: Using our ELISA, we detected MAC in human serum that protected blood vessels from the deleterious effects of oxidized LDL.