An Adipocyte-Derived Plasma Protein, Adiponectin, Adheres to Injured Vascular Walls

TLDR

Adipose tissue secretes a variety of proteins into the bloodstream. The study analyzes adiponectin characteristics in vitro and in vivo. The authors transfected adiponectin cDNA into COS cells, assessed secretion, performed solid‑phase binding assays to collagens, and conducted immunohistochemistry on injured vessels. Adiponectin, a plasma protein highly expressed in adipose tissue, binds collagen types I, III, and V in vascular intima, is secreted by transfected cells, is present in human plasma, and accumulates in injured but not intact vascular walls.

Abstract

Adipose tissue secretes a variety of proteins into the bloodstream. We have previously reported a novel cDNA, apM1 (adipose most abundant gene transcript 1), which is specifically and abundantly expressed in adipose tissue [1]. Primary structure analysis predicted that the apM1 gene product possesses significant homology to collagens VIII, X and complement factor C1q, and we named it adiponectin. In the current study, we analyzed characteristics of adiponectin in vitro and in vivo. Adiponectin protein was proved to be secreted into the medium when the cDNA was transfected to COS cells. Anti-adiponectin crossreactivities were abundantly detected in the human plasma. In solid-phase binding assays, adiponectin specifically bound to collagen types I, III and V, which are present in vascular intima. Immunohistochemical analysis revealed that adiponectin was detected in the walls of the catheter-injured vessels but not in the intact vascular walls. These data suggest that adiponectin is a plasma protein produced by adipose tissue and accumulates in vascular walls when the endothelial barrier is injured.