ABSTRACT
The objective was to assess whether pharmacological activation of lecithin cholesterol acyltransferase (LCAT) could exert beneficial effects on lipoprotein metabolism. A putative small molecule activator (compound A) was used as a tool compound in in vitro and in vivo studies. Compound A increased LCAT activity in vitro in plasma from mouse, hamster, rhesus monkey, and human. To assess the acute pharmacodynamic effects of compound A, C57Bl/6 mice and hamsters received a single dose (20 mg/kg) of compound A. Both species displayed a significant increase in high-density lipoprotein cholesterol (HDLc) and a significant decrease in non-HDLc and triglycerides acutely after dosing; these changes tracked with ex vivo plasma LCAT activity. To examine compound A's chronic effect on lipoprotein metabolism, hamsters received a daily dosing of vehicle or of 20 or 60 mg/kg of compound A for 2 weeks. At study termination, compound treatment resulted in a significant increase in HDLc, HDL particle size, plasma apolipoprotein A-I level, and plasma cholesteryl ester (CE) to free cholesterol ratio, and a significant reduction in very low-density lipoprotein cholesterol. The increase in plasma CE mirrored the increase in HDL CE. Triglycerides trended toward a dose-dependent decrease in very low-density lipoprotein and HDL, with multiple triglyceride species reaching statistical significance. Gallbladder bile acids content displayed a significant and more than 2-fold increase with the 60 mg/kg treatment. We characterized pharmacological activation of LCAT by a small molecule extensively for the first time, and our findings support the potential of this approach in treating dyslipidemia and atherosclerosis; our analyses also provide mechanistic insight on LCAT's role in lipoprotein metabolism.
Subject(s)
Enzyme Activation/physiology , Lipoproteins/metabolism , Liver/metabolism , Phosphatidylcholine-Sterol O-Acyltransferase/metabolism , Thiadiazoles/pharmacology , Animals , Bile Acids and Salts/blood , Cholesterol/blood , Cholesterol Esters/blood , Cricetinae , Enzyme Activation/drug effects , Female , Lipoproteins, HDL/blood , Liver/enzymology , Magnetic Resonance Spectroscopy , Mass Spectrometry , Mesocricetus , Mice , Mice, Inbred C57BL , Thiadiazoles/chemistry , Triglycerides/bloodABSTRACT
Lecithin:cholesterol acyltransferase (LCAT) is the key circulating enzyme responsible for high-density lipoprotein (HDL) cholesterol esterification, HDL maturation, and potentially reverse cholesterol transport. To further explore LCAT's mechanism of action on lipoprotein metabolism, we employed adeno-associated viral vector (AAV) serotype 8 to achieve long-term (32-week) high level expression of human LCAT in hCETP;Ldlr(+/-) mice, and characterized the lipid profiles in detail. The mice had a marked increase in HDL cholesterol, HDL particle size, and significant reduction in low-density lipoprotein (LDL) cholesterol, plasma triglycerides, and plasma apoB. Plasma LCAT activity significantly increased with humanized substrate specificity. HDL cholesteryl esters increased in a fashion that fits human LCAT specificity. HDL phosphatidylcholines trended toward decrease, with no change observed for HDL lysophosphatidylcholines. Triglycerides reduction appeared to reside in all lipoprotein particles (very low-density lipoprotein (VLDL), LDL, and HDL), with HDL triglycerides composition highly reflective of VLDL, suggesting that changes in HDL triglycerides were primarily driven by the altered triglycerides metabolism in VLDL. In summary, in this human-like model for lipoprotein metabolism, AAV8-mediated overexpression of human LCAT resulted in profound changes in plasma lipid profiles. Detailed lipid analyses in the lipoprotein particles suggest that LCAT's beneficial effect on lipid metabolism includes not only enhanced HDL cholesterol esterification but also improved metabolism of apoB-containing particles and triglycerides. Our findings thus shed new light on LCAT's mechanism of action and lend support to its therapeutic potential in treating dyslipidemia.
Subject(s)
Cholesterol Ester Transfer Proteins/metabolism , Dependovirus/genetics , Dyslipidemias/therapy , Gene Transfer Techniques , Genetic Therapy , Genetic Vectors , Lipids/blood , Phosphatidylcholine-Sterol O-Acyltransferase/genetics , Receptors, LDL/deficiency , Animals , Cholesterol Ester Transfer Proteins/genetics , Disease Models, Animal , Dyslipidemias/enzymology , Dyslipidemias/genetics , Humans , Liver/enzymology , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Mice, Transgenic , Particle Size , Phosphatidylcholine-Sterol O-Acyltransferase/metabolism , Receptors, LDL/genetics , Time FactorsABSTRACT
A series of pyrazolyl propionyl cyclohexenamides were discovered as full agonists for the high affinity niacin receptor GPR109A. The structure-activity relationship (SAR) studies were aimed to improve activity on GPR109A, reduce Cytochrome P450 2C8 (CYP2C8) and Cytochrome P450 2C9 (CYP2C9) inhibition, reduce serum shift and improve pharmacokinetic (PK) profiles.
Subject(s)
Amides/chemistry , Cyclohexenes/pharmacology , Receptors, G-Protein-Coupled/agonists , Animals , Cyclohexenes/chemistry , Cyclohexenes/pharmacokinetics , Mice , Rats , Receptors, Nicotinic , Structure-Activity RelationshipABSTRACT
Biaryl cyclohexene carboxylic acids were discovered as full and potent niacin receptor (GPR109A) agonists. Compound 1e (MK-6892) displayed excellent receptor activity, good PK across species, remarkably clean off-target profiles, good ancillary pharmacology, and superior therapeutic window over niacin regarding the FFA reduction versus vasodilation in rats and dogs.
Subject(s)
Carboxylic Acids/pharmacology , Cyclohexanecarboxylic Acids/pharmacology , Cyclohexenes/chemistry , Drug Discovery , Oxadiazoles/pharmacology , Receptors, G-Protein-Coupled/agonists , Animals , Area Under Curve , Binding, Competitive , CHO Cells , Carboxylic Acids/chemistry , Carboxylic Acids/pharmacokinetics , Cricetinae , Cricetulus , Cyclohexanecarboxylic Acids/chemistry , Cyclohexanecarboxylic Acids/pharmacokinetics , Dogs , Drug Evaluation, Preclinical , Fatty Acids, Nonesterified/blood , Humans , Metabolic Clearance Rate , Mice , Mice, Inbred C57BL , Mice, Knockout , Models, Chemical , Molecular Structure , Oxadiazoles/chemistry , Oxadiazoles/pharmacokinetics , Rats , Receptors, G-Protein-Coupled/genetics , Receptors, G-Protein-Coupled/metabolism , Receptors, Nicotinic/genetics , Receptors, Nicotinic/metabolism , Structure-Activity Relationship , Vasodilation/drug effectsABSTRACT
Tricyclic analogues were rationally designed as the high affinity niacin receptor G-protein-coupled receptor 109A (GPR109A) agonists by overlapping three lead structures. Various tricyclic anthranilide and cycloalkene carboxylic acid full agonists were discovered with excellent in vitro activity. Compound 2g displayed a good therapeutic index regarding free fatty acids (FFA) reduction and vasodilation effects in rats, with very weak cytochrome P450 2C8 (CYP2C8) and cytochrome P450 2C9 (CYP2C9) inhibition, and a good mouse pharmacokinetics (PK) profile.
Subject(s)
Cycloparaffins/chemical synthesis , Flushing/chemically induced , Heterocyclic Compounds, 3-Ring/chemical synthesis , Hypolipidemic Agents/chemical synthesis , Niacin/metabolism , Receptors, G-Protein-Coupled/agonists , ortho-Aminobenzoates/chemical synthesis , Adipocytes/drug effects , Adipocytes/metabolism , Animals , CHO Cells , Cricetinae , Cricetulus , Cycloparaffins/adverse effects , Cycloparaffins/pharmacology , Ear/blood supply , Heterocyclic Compounds, 3-Ring/adverse effects , Heterocyclic Compounds, 3-Ring/pharmacology , Humans , Hypolipidemic Agents/adverse effects , Hypolipidemic Agents/pharmacology , In Vitro Techniques , Lipolysis , Male , Mice , Radioligand Assay , Rats , Receptors, Nicotinic , Structure-Activity Relationship , Vasodilation/drug effects , ortho-Aminobenzoates/adverse effects , ortho-Aminobenzoates/pharmacologyABSTRACT
The design, synthesis, and biological activity of a series of cycloalkene acid-based niacin receptor agonists are described. This led to the discovery that tetrahydro anthranilic acid is an excellent surrogate for anthranilic acid. Several compounds were identified that were potent against the niacin receptor, had enhanced cytochrome P450 selectivity against subtypes CYP2C8 and CYP2C9, and improved oral exposure in mice.
Subject(s)
Cyclohexenes/chemical synthesis , Cyclohexenes/pharmacology , Cyclopentanes/chemical synthesis , Cyclopentanes/pharmacology , Cytochrome P-450 Enzyme System/metabolism , Nicotinic Agonists/chemical synthesis , Nicotinic Agonists/pharmacology , ortho-Aminobenzoates/chemical synthesis , ortho-Aminobenzoates/pharmacology , Animals , Aryl Hydrocarbon Hydroxylases/drug effects , Cyclohexenes/chemistry , Cyclohexenes/pharmacokinetics , Cyclopentanes/chemistry , Cyclopentanes/pharmacokinetics , Cytochrome P-450 CYP2C8 , Cytochrome P-450 CYP2C9 , Drug Design , Humans , Mice , Nicotinic Agonists/chemistry , Nicotinic Antagonists/pharmacology , ortho-Aminobenzoates/chemistry , ortho-Aminobenzoates/pharmacokineticsABSTRACT
Biaryl anthranilides are reported as potent and selective full agonists for the high affinity niacin receptor GPR109A. The SAR presented outlines approaches to reduce serum shift and both CYPCYP2C8 and CYP2C9 liabilities, while improving PK and maintaining excellent receptor activity. Compound 2i exhibited good in vivo antilipolytic efficacy while providing a significantly improved therapeutic index over vasodilation (flushing) with respect to niacin in the mouse model.
