Studies on the lipid-regulating mechanism of alisol-based compounds on lipoprotein lipase

Studies on the lipid-regulating effects of alisol compounds are reported that include alisol B, alisol A 24-acetate (24A), alisol A and an alisol B - 24A - alisol A mixture (content ratio = 1:1:1). The effects on the activity of lipoprotein lipase (LPL), a key lipid-modulating enzyme, were studied to investigate the molecular mechanism of lipid-regulating activity of alisols. The effects of alisols on regulating blood lipids and the activities of LPL were determined using a reagent kit method. The structure of LPL was obtained by homology modeling and the interactive mechanism of alisol monomers and the mixture with LPL was investigated by molecular simulation. The alisol monomer and mixture were shown to regulate blood lipids, suggesting that alisols may decrease the level of triglyceride (TG) by improving the activity of LPL. The order of intensity was: mixture > alisol A > alisol B > 24A, indicating that alisols of alismatis rhizoma feature a synergistic effect on LPL. The N- and C-terminus of LPL both represented the catalytic active domains of this lipid-regulating effect. Cys306, Gln129 and Ser166 were the key amino acid residues resulting in the lipid-regulating effect of the alisol monomer while Ser166 and Arg18 were found to be responsible for the lipid-regulating effect of the mixture. The C-terminus of LPL was indirectly involved in the enzymatic process. A folded side chain of alisols or the parent ring was found to bind somewhat weaker to LPL than an open side chain or parent ring. The hydroxyl groups on the C14-, C22-, C28-, C30- and C31-terminus in the side chain, the ring ether structure in C23-position, and the acetyl group in C29-position represented the key sites for the lipid-regulating action of alisols. Meanwhile, the C30-site hydroxyl group played an important role in the synergistic effect of the alisol mixture.