Hypolipidemic activity of 4-pyrimidinecarboxylic acids in CF1 mice

Triglyceride-lowering agents

This review is the first attempt at systematization of the literature data on the structures and activities of triglyceride-lowering agents which used in medical practice or are in development. The effects and mechanisms of action of statins, squalene synthase inhibitors, fibrates, PPARα and PPARα/γ agonists, nicotinic acid, omega-3 fatty acids and some other molecular targets were considered. Unfortunately, to date, harmless and effective triglyceride-lowering drug still does not exist and there is still need for development of better triglyceride-lowering agents.

Investigation of 3,5-isoxazolidinediones as hypolipidemic agents in rodents

A series of 2-benzoyl-4,4-dialkyl-3,5-isoxazolidinediones proved to have potent hypolipidemic activity, lowering both serum cholesterol and triglyceride levels at 10 or 20 mg/kg/day, IP and orally in rodents. 2-(3,4,5-Trimethoxybenzoyl)-4,4-diethyl-3,5-isoxazolidinedione+ ++ (4) afforded the best hypolipidemic activity lowering normolipidemic CF1 mouse serum cholesterol levels 49% and serum triglyceride levels 34% at 20 mg/kg/day, IP. Compound 4 was selected as a typical derivative of the chemical class for further detailed studies. Serum cholesterol levels in normolipidemic Sprague Dawley male rats were reduced 45% after 8 weeks at 10 and 20 mg/kg/day of compound, orally. Serum triglyceride levels were reduced 38-49% at 10 and 20 mg/kg/day, orally. In vitro liver enzyme activities studies in normolipidemic CF1 mice showed the compound inhibited mitochondrial citrate exchange, acetyl CoA synthetase, HMG CoA reductase, acyl CoA cholesterol acyl transferase, acetyl CoA carboxylase, sn-glycerol-3-phosphate acyl transferase, phosphatidylate phosphohydrolase and heparin-induced lipoprotein lipase activities with increases in the activities of cholesterol ester hydrolase and ATP-dependent citrate lyase. Similar enzyme activities were inhibited in vivo except HMG CoA reductase activity was not inhibited in rat liver or small intestinal mucosa after 8 weeks drug administration. Cholesterol levels were reduced in tissues after 8 weeks administration of compound 4 in normolipidemic rats. Bile cholesterol and triglyceride levels were elevated after two weeks administration to rats at 20 mg/kg/day. Serum lipoprotein levels in normolipidemic and hyperlipidemic rats showed the cholesterol levels in VLDL and LDL fractions after 4, 6 and 8 weeks at 10 and 20 mg/kg/day were reduced whereas HDL-cholesterol levels were significantly elevated. Studies demonstrated that 3H-cholesterol and 14C-palmitic acid incorporation into lipids of the lipoprotein fraction was reduced by the drug but 32P-incorporation was generally elevated. The agent demonstrated no observable toxicity in rats after 8 weeks administration, orally. The acute toxicity study in normolipidemic mice at 20, 40 and 100 mg/kg/day, IP, demonstrated no observable harmful effects of the drug.

Synthesis and hypolipidemic activity of 4-substituted 1-acyl-1,2,4-triazolidine-3,5-diones in rodents

A series of 4-substituted 1-acyl-1,2,4-triazolidine-3,5-diones demonstrated potent activity in CF1 mice when administered intraperitoneally at 20 mg/kg/day, lowering both serum cholesterol and triglyceride levels significantly. The 4-(4-chlorophenyl)-substituted compounds demonstrated better hypolipidemic activity in rodents than 4-methoxy-, 4-nitro-, and 4-t-butylphenyl substitutions. Aryl and alkyl substitutions rather than benzoyl substitutions at position 4 demonstrated good hypocholesterolemic activity. Selected compounds were examined for the mode of action in rats in which serum cholesterol and triglyceride levels were reduced after administration of 20 mg/kg/day orally; tissue lipids were reduced after 14 days of administration, and bile and fecal lipids were increased by 44-250%. Serum lipoprotein levels were also modulated by the agents, with cholesterol levels in very low density lipoprotein and low density lipoprotein fractions being reduced by 2-57%. Cholesterol levels in the high density lipoprotein fraction were elevated by 94-341%. Activities of mouse hepatic enzymes were suppressed by the agents in a manner that suggested that the compounds interfere with de novo synthesis of lipids.

Hypolipidemic activity of 6-alkoxycarbonyl-3-aryl-1,3,5- triazabicyclo[3.1.0]hexane-2,4-diones and 2-alkoxycarbonyl-5-aryl-1,3,5-triazine-4,6(1H,5H)-diones in rodents

Significant hypolipidemic activity was demonstrated by 6-ethoxycarbonyl-1-3-phenyl-1,3,5-triazabicyclo[3.1.0]hexane-2,4-dione, 2-ethoxycarbonyl-5-phenyl-1,3,5-triazine-4,6(1H,5H)-dione and 2-ethoxycarbonyl-5-(4-chlorophenyl)-1,3,5-triazine-4,6(1H,5H)-dione in rodents at 20 mg/kg/day. These agents lowered serum cholesterol and triglyceride levels by approximately 40% in mice after 16 d. Tissue lipids in rat liver, small intestinal mucosa, aortic wall and feces were reduced by treatment with the agents. Very low density lipoprotein (VLDL) and low density lipoprotein (LDL) cholesterol levels were reduced in the rat; high density lipoprotein (HDL) cholesterol levels were elevated after 14 d of treatment. The activities of regulatory enzymes, e.g., acetyl-CoA synthetase, acyl-CoA:cholesterol acyltransferase, cholesterol 7 alpha-hydroxylase, sn-glycerol-3-phosphate acyltransferase, phosphatidylate phosphohydrolase and heparin-induced lipoprotein lipase, involved in de novo synthesis of hepatic lipids were affected by the agents. The new compounds may represent another class of potentially useful hypolipidemic agents for the treatment of atherosclerosis since HDL cholesterol levels were increased and VLDL and LDL cholesterol levels were lowered by some of the agents.

The hypolipidemic effects of 2-furoic acid in Sprague-Dawley rats

2-Furoic acid was shown to be effective in lowering both serum cholesterol and serum triglyceride levels significantly in rats with an elevation of HDL cholesterol level at 20 mg/kg/day orally. LDL receptor activity was reduced in hepatocytes, aorta foam cells, small intestinal epithelium cells and fibroblasts. HDL receptor activity was elevated in the rat hepatocytes and small intestinal cells. These activities were correlated with inhibition of acyl CoA cholesterol acyl transferase activity. Neutral cholesterol ester hydrolase activity was elevated in rat hepatocytes and human fibroblasts. Thus, 2-furoic acid appears to interfere directly with activity of intracellular enzymes rather than affecting high affinity-mediated lipoprotein membrane receptors. In vivo treatment with 2-furoic acid led to reduction in the liver and small intestine ATP dependent citrate lyase, acetyl CoA synthetase, acyl CoA cholesterol acyl transferase, sn-glycerol 3-phosphate acyl transferase, phosphatidylate phosphohydrolase and heparin induced lipoprotein lipase activities. 2-Furoic acid reduced biliary cholesterol levels but the agent increased bile salts which are lithogenic. Acute toxicity studies in mice suggest that the agent has some hepatic toxicity effects. The LD50 was relatively low at 250 mg/kg IP in mice.

The hypolipidemic activity of heterocyclic amine boranes in rodents

Heterocyclic amine boranes were observed to be potent hypolipidemic agents in rodents at 8 mg/kg per day lowering both serum cholesterol and triglyceride levels. These agents were also effective in lowering tissue lipids. Rat serum lipoprotein cholesterol levels were reduced in the low density lipoprotein (LDL) and very low density lipoprotein (VLDL) fractions and elevated in the high density lipoprotein (HDL) fraction after 14 days. The modes of action of the agents appear to accelerate excretion of lipids in the bile and the suppression of the activities of key hepatic regulatory enzymes of lipids synthesis.

Hypolipidemic activity of 6-amino-2-mercapto-5-methyl-pyrimidine-4-carboxylic acid and related derivatives in rodents

6-Amino-2-mercapto-5-methylpyrimidine-4-carboxylic acid proved to be a potent hypolipidemic agent in rodents at the low dose of 20 mg/kg/d. The agent effectively reduced the liver enzyme activities required for the synthesis of triglycerides and cholesterol. Lower lipid levels in tissue were observed in mice but not in rats. Preliminary studies indicate that the agent accelerated the excretion of cholesterol and its metabolites from the body. The agents lowered the low-density lipoprotein (LDL) cholesterol content and raised the high-density lipoprotein (HDL) cholesterol content. These changes in lipoprotein cholesterol content suggest that the agent may be helpful in protecting against coronary disease. The agent is more effective than the commercially available agent, i.e., clofibrate at 150 mg/kg/d.