Adiponectin forms a complex with atherogenic LDL and inhibits its downstream effects

Area of Science:

• Biochemistry
• Molecular Biology
• Cardiovascular Research

Background:

• Adiponectin, an adipocyte-derived protein, possesses known antiatherogenic and antidiabetic properties.
• The precise mechanisms by which adiponectin confers its antiatherogenic effects, particularly its interaction with atherogenic lipoproteins, remain incompletely understood.
• Atherogenic low-density lipoprotein (LDL) subfractions, such as L5 and oxidized LDL (oxLDL), are implicated in the development of atherosclerosis and are internalized via scavenger receptors like LOX-1.

Purpose of the Study:

• To investigate the potential interaction between adiponectin and atherogenic LDL.
• To elucidate whether adiponectin can attenuate the atherogenicity of LDL particles.
• To explore the role of adiponectin in modulating LDL uptake and cellular responses mediated by LOX-1.

Main Methods:

• Enzyme-linked immunosorbent assays (ELISAs) were employed to assess the binding affinity of adiponectin to native LDL, oxLDL, and LDL subfractions.
• Cellular uptake studies were conducted using Chinese hamster ovary (CHO) cells expressing either the LDL receptor or LOX-1, as well as human coronary artery endothelial cells (HCAECs) and THP-1-derived macrophages.
• Western blot analysis and sandwich ELISAs were used to detect adiponectin in LDL subfractions and confirm its binding to oxLDL and L5. Cellular signaling pathways (NF-κB, ERK, AMPK) were analyzed.

Main Results:

• Adiponectin demonstrated preferential binding to oxidized LDL (oxLDL) and the electronegative LDL subfraction L5, but not to native LDL.
• Adiponectin significantly inhibited the cellular uptake of oxLDL and L5 in cells expressing LOX-1, while not affecting native LDL uptake via the LDL receptor.
• Adiponectin suppressed oxLDL- and L5-induced pro-atherogenic cellular responses, including NF-κB activation and ERK phosphorylation, and reduced oxLDL-induced endothelin-1 secretion in HCAECs.

Conclusions:

• Adiponectin directly binds to atherogenic LDL particles, specifically oxLDL and L5.
• This binding interaction leads to the inactivation of atherogenic LDL, thereby inhibiting its cellular uptake and downstream pro-atherogenic signaling.
• The findings provide novel insights into the antiatherogenic mechanisms of adiponectin, highlighting its role in neutralizing harmful LDL modifications.