Metabolic syndrome (MetS) is defined as a cluster of cardiovascular and metabolic disorders. Previous studies have demonstrated that ligands selective for I₁ imidazoline receptor (LNPs) ameliorate lipid metabolism (plasma total cholesterol and triglycerides levels) in rat models of metabolic syndrome.

The objective of this study was to explore possible direct actions on hepatocytes which are involved in the regulation of lipid metabolism. Experiments were carried out in HepG2 cells, a cell line of hepatocytes. In order to evaluate the effect of LNP509 on lipid metabolism, the activation (i.e. phosphorylation) of a key actor of this signaling pathway, AMPK, was evaluated by measuring the ratio pAMPK/AMPK by Western Blot. AMPK is the main regulator of Acetyl-CoA-carboxylase (ACC) which is known to provide the malonyl-CoA substrate for the biosynthesis of fatty acids and to play a major role in hepatic steatosis. The effect of LNP509 on ACC phosphorylation (inactivation of ACC) was evaluated by measuring pACC/ACC by Western Blot. Hepatic steatosis, induced by treating HepG2 cells with oleic acid, was quantified by Oil Red O coloration and colorimetric measurements after oil Red O extraction. LNP509 (1 μM, 60 min) induced the M, phosphorylation of AMPK (pAMPK/ AMPK=1.15±0.27) compared to control (pAMPK/AMPK=0.37±0.06).

Interestingly, treatment by LNP509 during 60 min also increased the phosphorylation (inhibition) of ACC (untreated cells: pACC/ACC=0.24±0.06; LNP 509 pACC/ACC=0.70±0.22). Concerning hepatic steatosis, LNP509 seemed to prevent lipid accumulation in HepG2 cell (cells alone=100%, cells+oleic acid=138.54%±10.34, cells+oleic acid+LNP509=112.81%±9.29).

These data suggest that LNPs act directly on hepatic cells to activate AMPK pathway and prevent lipid accumulation. This mechanism probably accounts, at least partly, for the beneficial effects of LNPs on dyslipidemia observed in vivo.

The author hereby declares no conflict of interest