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 CF_l 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 CF_l 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.     

The Effects of N(4-Methylphenyl)diphenimide on Lipid Metabolism of Sprague Dawley Rats

N(4-Methylphenyl)diphenimide proved to be an effective hypolipidemic agent in rats at 10 and 20 mg/kg/day. Both serum cholesterol and triglyceride levels were reduced significantly. Decreases in tissue lipids as well as VLDL cholesterol levels were observed. HDL-cholesterol was elevated even at 10 mg/kg/day. The agent was equally effective in hyperlipidemic diet-induced rats, lowering serum lipids and VLDL- and LDL-cholesterol while elevating HDL-cholesterol levels. The drug interfered with the incorporation of ³H-cholesterol and ³H-palmitic acid into chylomicrons, VLDL, and LDL. The two precursors were incorporated at a higher rate into HDL.³H-Leucine was incorporated into chylomicrons, VLDL, and LDL at a higher rate, but not into HDL. Reduced uptake of the precursor for lipid synthesis was noted in tissues after treatment with the drug.     

Terephthalic Acid in Sprague-Dawley Rats as a Hypolipidemic Agent

Terephthalic acid at 20 mg/kg/day in lowered serum cholesterol and triglyceride levels in rats. The cholesterol content was lowered in the lipoprotein fractions. The effects of the agents on de novo lipid synthesis showed that similar enzymes were affected in rat liver and small intestinal mucosa cells as when compared to in vitro tissue culture cells from rats and humans, e.g. reduction of acyl CoA cholesterol acyl transferase and elevation of neutral cholesterol ester hydrolase activities suggest that net cholesterol esters deposition in foam cells should be reduced and plaque growth should be slowed. The suppression of LDL receptor binding and degradation by the drug suggest that less apoB lipoproteins are taken up by peripheral tissues. The elevated HDL receptor binding and internalization in the liver suggest that the drug accelerates cholesterol return to the liver. Additional studies show that cholesterol and bile acid secretion in the bile is elevated. However, the bile acids secreted are not lithogenic. Acute toxicity studies show that the agent appears to be safe in rodents. Two observations of increased serum alkaline phosphophatase levels and increased liver vacuolation suggest some alteration of hepatic cell morphology, which requires further investigation.     

Antineoplastic activities and cytotoxicity of 1-acyl and 1,2-diacyl-1,2,4-triazolidine-3,5-diones in murine and human tissue culture cells.

1-Acyl- and 1,2-diacyl-1,2,4-triazolidine-3,5-diones were found to be potent cytotoxic agents in murine and human cancer cell lines, e.g. L1210, P388, Tmolt3, colon adenocarcinoma, Hela cells and glioma. In vivo activity was demonstrated at 8 mg/kg/day against Ehrlich ascites carcinoma growth. In L1210 cells, 1-acetyl-4-phenyl-1,2,4-triazolidine-3,5-dione, 41, reduced DNA synthesis significantly with moderate reduction in RNA synthesis. Enzyme sites in L1210 cells which were markedly affected were m- and r-RNA polymerase, PRPP amidotransferase, IMP dehydrogenase, dihydrofolate reductase, thymidine, TMP and TDP kinases. Kinetic studies suggest the inhibition of rate limiting enzymes in the purine pathway by 41 was responsible for its cytotoxicity. Acute toxicity studies in mice indicated 41 was safe for therapeutic use at 20, 50, and 100 mg/ky/day.     

The Hypolipidemic Effects of l-Acetyl-4-phenyl-l,2,4-triazolidine-3,5-dione in Rodents

l-Acetyl-4-phenyl-l ,2,4-triazolidine,5-dione (APTD), a potent hypolipidemic agent, lowered both serum cholesterol and triglyceride levels in normo- and hyperlipidemic rats at 10 or 20 mg/kg/day. The agent effectively lowered VLDL-cholesterol (VLDL-C) and LDL-C content and raised HDL-C content in normal and hyperlipidemic rats treated from 4 to 8 weeks. Similar effects on the incorporation of cholesterol into the lipoprotein fractions were observed after drug treatment. Tissue lipids, e.g. cholesterol, were lowered, whereas fecal cholesterol levels were increased. APTD's primary targets were acyl CoA cholesterol acyl transferase (ACAT) for cholesterol ester synthesis and sn-glycerol-3-phosphate acyl transferase (GPAT) and phosphatidylate phosphohydrolase (PPH) for triglyceride synthesis.