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Tanaka Y, Nagao K, Nakagiri H, Nagaso T, Iwasa Y, Mori H, Asahina M, Imaizumi K, Sato M. Unavailability of liver triacylglycerol increases serum cholesterol concentration induced by dietary cholesterol in exogenously hypercholesterolemic (ExHC) rats. Lipids Health Dis 2014; 13:19. [PMID: 24450544 PMCID: PMC3902423 DOI: 10.1186/1476-511x-13-19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2013] [Accepted: 01/14/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Exogenously hypercholesterolemic (ExHC) rats develop hypercholesterolemia and low hepatic triacylglycerol (TAG) levels when dietary cholesterol is loaded. The responsible gene Smek2 was identified via linkage analysis using the original strain Sprague-Dawley (SD) rats. In this study, we compared SD and ExHC rats to investigate a relationship between hypercholesterolemia and the low hepatic TAG levels observed in ExHC rats. METHODS Male 4-weeks-old ExHC and SD rats were fed a 1% cholesterol diet for 1 week. Serum and liver parameters were analyzed. Gene expression and enzyme activities related to TAG metabolism were also assessed. RESULTS We reproducibly observed higher serum cholesterol and lower hepatic TAG levels in ExHC rats than in SD rats. Golgi apparatus in the livers of ExHC rats secreted β-very-low-density lipoprotein (β-VLDL) that had higher cholesterol ester (CE) and lower TAG content than those in the β-VLDL secreted by SD rats. Gene expression related to fatty acid and TAG synthesis in ExHC rats was lower than that in SD rats. Enzymatic activities for fatty acid synthesis were also relatively lower in ExHC rats. Moreover, the fatty acid composition of hepatic and serum CE in ExHC rats showed that these CEs were not modified after secretion from the liver despite the similar activities of serum lecithin-cholesterol acyltransferase (LCAT) in ExHC rats to those in SD rats. CONCLUSIONS Low production of liver TAG and secretion of CE-rich, TAG-poor β-VLDL without modification by LCAT in the circulation contributed to hypercholesterolemia induced by dietary cholesterol in ExHC rats.
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Affiliation(s)
- Yasutake Tanaka
- Laboratory of Nutrition Chemistry, Division of Bioresource and Bioenvironmental Sciences, Graduate School, Kyushu University, 6-10-1 hakozaki, higashi-ku, Fukuoka 812-8581, Japan
| | - Koji Nagao
- Laboratory of Nutrition Chemistry, Division of Bioresource and Bioenvironmental Sciences, Graduate School, Kyushu University, 6-10-1 hakozaki, higashi-ku, Fukuoka 812-8581, Japan
| | - Hideaki Nakagiri
- Laboratory of Nutrition Chemistry, Division of Bioresource and Bioenvironmental Sciences, Graduate School, Kyushu University, 6-10-1 hakozaki, higashi-ku, Fukuoka 812-8581, Japan
| | - Toshirou Nagaso
- Laboratory of Nutrition Chemistry, Division of Bioresource and Bioenvironmental Sciences, Graduate School, Kyushu University, 6-10-1 hakozaki, higashi-ku, Fukuoka 812-8581, Japan
| | - Yasue Iwasa
- Laboratory of Nutrition Chemistry, Division of Bioresource and Bioenvironmental Sciences, Graduate School, Kyushu University, 6-10-1 hakozaki, higashi-ku, Fukuoka 812-8581, Japan
| | - Haruhiko Mori
- Laboratory of Nutrition Chemistry, Division of Bioresource and Bioenvironmental Sciences, Graduate School, Kyushu University, 6-10-1 hakozaki, higashi-ku, Fukuoka 812-8581, Japan
| | - Makoto Asahina
- Laboratory of Nutrition Chemistry, Division of Bioresource and Bioenvironmental Sciences, Graduate School, Kyushu University, 6-10-1 hakozaki, higashi-ku, Fukuoka 812-8581, Japan
| | - Katsumi Imaizumi
- Laboratory of Nutrition Chemistry, Division of Bioresource and Bioenvironmental Sciences, Graduate School, Kyushu University, 6-10-1 hakozaki, higashi-ku, Fukuoka 812-8581, Japan
| | - Masao Sato
- Laboratory of Nutrition Chemistry, Division of Bioresource and Bioenvironmental Sciences, Graduate School, Kyushu University, 6-10-1 hakozaki, higashi-ku, Fukuoka 812-8581, Japan
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Taniguchi M, Nagao K, Inoue K, Imaizumi K. Cholesterol lowering effect of sulfur-containing amino acids added to a soybean protein diet in rats. J Nutr Sci Vitaminol (Tokyo) 2008; 54:448-53. [PMID: 19155582 DOI: 10.3177/jnsv.54.448] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The cholesterol-lowering action of soybean protein was studied with rats from the aspect of sulfur-containing amino acids using casein as a counterpart. Weanling rats were fed for 3 wk on a soybean protein isolate (SPI) or casein diet. Serum cholesterol levels did not differ between the two diet groups, but were lowered by supplementing methionine to a 10% SPI diet or cystine to an amino acid mixture diet, equivalent to a 10% SPI or to a 20% SPI diet. By adding methionine or cystine to a 10% SPI diet, cholesterol 7alpha-hydroxylase activity was elevated concomitantly with elevated hepatic glutathione (GSH) level, while hydroxyl methyl-glutalyl coenzyme A reductase activity was reduced by methionine, regardless of GSH levels. Excretion of fecal steroid was not significantly changed by addition of either amino acid, as expressed per body weight. These results indicate that the relative amount of methionine and cystine in a diet affected cholesterol metabolizing enzyme activity in a way not parallel to GSH concentration.
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Affiliation(s)
- Misako Taniguchi
- Department of Nutrition Sciences, Nakamura Gakuen University, Fukuoka, Japan.
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Ni W, Yoshida S, Tsuda Y, Nagao K, Sato M, Imaizumi K. Ethanol-extracted soy protein isolate results in elevation of serum cholesterol in exogenously hypercholesterolemic rats. Lipids 1999; 34:713-6. [PMID: 10478929 DOI: 10.1007/s11745-999-0417-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Soy protein preparations were reported to have hypocholesterolemic actions in experimental animals and humans, while the active components and the mechanism by which this occurs are not clarified yet. The objective of this study is to address these issues by using exogenously hypercholesterolemic rats which are susceptible to dietary cholesterol. Two groups of five rats (male, 12-wk-old) were fed on AIN 93G-based diet with soy protein isolate (SPI) or ethanol-extracted SPI (EE-SPI) for 2 wk. EE-SPI was prepared by ethanol extraction to remove isoflavones and other components. Concentrations of serum and liver total cholesterol were lower in rats fed SPI than in those fed EE-SPI. The abundances of mRNA for 7alpha-hydroxylase and low density lipoprotein receptor in the liver were lower in EE-SPI group than those in SPI group. These results suggest that the ethanol extract from SPI has a factor(s) to alleviate hypercholesterolemia by increasing the removal of cholesterol from serum through the receptor pathway and then from liver through enhancement of bile acid synthesis.
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Affiliation(s)
- W Ni
- Division of Bioresource and Bioenvironmental Sciences, Graduate School, Kyushu University, Fukuoka, Japan
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Nagao K, Yoshida S, Nakagiri H, Sakono M, Sato M, Imaizumi K. Gemfibrozil reduces non-high-density lipoprotein cholesterol in exogenously hypercholesterolemic (ExHC) rats fed a high-cholesterol diet. Comp Biochem Physiol B Biochem Mol Biol 1998; 120:579-86. [PMID: 9787818 DOI: 10.1016/s0305-0491(98)10049-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Gemfibrozil is a widely used drug prescribed to elevate serum high-density lipoprotein (HDL) cholesterol levels and lower triacylglycerols. The present study was done to determine if the drug would alleviate hypercholesterolemia in exogenously hypercholesterolemic (ExHC) rats. In the drug-treated ExHC rats, the serum non-HDL cholesterol levels were lowered and the ratio of the non HDL cholesterol to serum triacylglycerols was decreased to the extent seen in the drug-treated SD rats. Liver cholesterol and triacylglycerols were lowered in the drug-treated rats. There was also an increase in fecal excretion of neutral sterols and bile acids, particularly chenodeoxycholic and beta-muricholic acids. The drug elevated cholesterol 7 alpha-hydroxylase activity and mRNA abundance and acyl-CoA cholesterol acyltransferase activity in the liver, but did not influence low-density lipoprotein receptor mRNA level in the liver. Thus, gemfibrozil is effective in alleviating hypercholesterolemia in exogenously hypercholesterolemic rats, by partitioning hepatic cholesterol into biliary excretion.
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Affiliation(s)
- K Nagao
- Department of Food Science and Technology, Faculty of Agriculture, Kyushu University, Fukuoka, Japan
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