Hong K. Kim

Quantitation of serum lipids by a simple TLC-charring method.

Abstract The thin layer chromatographic-charring technique of Marsh and Weinstein has been shown to provide a simple, rapid means for the estimation of serum lipids. The method involves separation of lipids by thin layer chromatography, scraping the spot into a test tube, charring with concentrated H2SO4 and determination of the absorbance at 375 nm. Results obtained by this method compare favorably with the Sperry-Webb and Van Handel-Zilversmit methods for cholesterol and triglycerides, respectively.

Experimental atherosclerosis in rabbits fed cholesterol-free diets: 5. Comparison of Peanut, Corn, Butter, and Coconut Oils

Abstract Four groups of Dutch belted rabbits were fed a semipurified diet containing 40% sucrose, 25% casein, and 14% fat for 10 months (without added cholesterol). The fats were peanut oil (PNO), corn oil (CO), butter oil (BO), and coconut oil (CNO). All diets were hyperlipidemic and hyperlipoproteinemic. The highest serum cholesterol and triglyceride levels were observed in the CNO groups, 330 and 286 mgm/dl, respectively. Serum cholesterol and triglyceride levels in the other groups (mgm/dl) were: PNO-205 and 51; CO-152 and 28; BO-292 and 48. The serum of α β lipoprotein cholesterol ratios were: PNO-0.28; CO-0.28; BO-0.19, and CNO-0.13. This ratio is about 0.35–0.40 in normal Dutch belted rabbits. Liver cholesterol levels were similar in all groups (1.35 ± 0.5 gm/100 gm). Liver triglyceride levels were (gm/100 gm): PNO-0.37; CO-0.55; BO-0.66; CNO-0.39. The most severe gross atherosclerosis was observed in the CNO group (25% of surface area) and the least in the CO group (2%). The involved surface area in the other two groups was: PNO-10% and BO-14%. Microscopic evaluation of the severity of the aortic lesions indicated that the rabbits fed CNO, BO, and PNO had the most frequent and severe lesions. In contrast, the animals fed CO consistently showed much less aortic disease. Gross aortic examination revealed distinct differences in the characteristics of atherosclerotic lesions induced by the four dietary fats. The most extensive lesions, observed in rabbits fed CNO, were characterized by intimal proliferation spread over the area of lipid deposition. BO tended to produce aortic lesions rich in lipid but a relatively small number of cells and little collagen deposition. The aortic lesions in rabbits fed PNO contained relatively little lipid and were characterized by thick fibrous plaques due to prominent intimal proliferation and a high proportion of collagen. The rabbits fed CO developed few aortic lesions, with minimal intimal proliferation and very little lipid. The relative atherogenicity of PNO was an unexpected finding.

Experimental atherosclerosis in rabbits fed cholesterol-free diets: 4. Investigation into the source of cholesteremia☆

Abstract The metabolism of exogenous and endogenous cholesterol was studied in rabbits fed a normal diet of rabbit chow or an atherogenic, semisynthetic diet ( SS ) containing 40% carbohydrate, 25% casein, and 14% hydrogenated coconut oil. The SS diet was more cholesteremic, betalipoproteinemic and atherogenic. More cholesterol was absorbed and more synthesized by rabbits on the SS diet and more radioactive cholesterol was recovered from their lesions. The chow-fed rabbits excreted 4 times as much feces over a 3 day period. Biliary cholesterol and total bile acids were 2.2 and 2.6 times higher in the SS group. The biliary cholesterol-specific activity was significantly higher in the SS group but cholanoic acid-specific activities and primary/secondary bile acid ratios were significantly lower. The data suggest that one reason for the cholesteremic effect of the SS diet is a reduced level of degradation of endogenous cholesterol to bile acids.

Effect of Colestipol (U-26,597A) on Experimental Atherosclerosis in Rabbits

Summary Colestipol, a high-molecular-weight polymer which binds bile acids, exerts a hypocholesteremic effect in several species. The addition of 1% colestipol to an atherogenic regimen (2% cholesterol, 6% corn oil) did not significantly affect serum or liver cholesterol levels of rabbits but did cause a significant reduction (p < .05) in atheromata in both the aortic arch and thoracic aorta. An appreciable number of rabbits fed 1% colestipol were free of atheromata. We are indebted to Dr. T. M. Parkinson of the Upjohn Co., Kalamazoo, MI for generously supplying the colestipol used in this work.

Quantitative recovery of lipids from aortas stained with Sudan IV

The separation of Sudan IV from lipid extracts of stained aortas can be accomplished by thin layer or column chromatography, but the most convenient method involves adsorption of the dye to activated carbon. The aortic lipids are thus recovered quantitatively.

Cholesterol vehicle in experimental atherosclerosis: Part 12. Rapeseed oil☆

Abstract Rabbits were fed diets containing 2% cholesterol and 6% of either rapeseed oil (RSO) or corn oil (CO). In three experiments there were no differences in atherogenicity of the two oils. Serum cholesterol and liver triglyceride levels were similar in the two groups, whereas serum triglycerides and liver cholesterols were somewhat lower in rabbits fed cholesterol and RSO. From gas chromatographic analysis of the triglycerides and cholesterol esters of aortas and livers, there is indirect evidence for the conversion of erucic to oleic acid. At the level and time period of feeding (6%, 2 months) RSO did not exert a deleterious effect on the rabbits.

Lipolysis of corn, peanut and randomized peanut oils

Corn oil, peanut oil and randomized peanut oil exhibit different atherogenic potentials; peanut oil being more atherogenic than the other oils. This study was conducted to ascertain if the atherogenicity of these oils was related to their rates of lipolysis. Using both pancreatic lipase and milk lipoprotein lipase (LPL), it was shown that the rated of lipolysis were corn oil>peanut oil>randomized peanut oil. The rates of lipolysis are not related to atherogenicity and may be affected by the distribution of long-chain saturated fatty acids in the component triglycerides.