Effect of dietary methionine and polychlorinated biphenyls on cholesterol metabolism in rats fed a diet containing soy protein isolate.

Oda, Hiroaki; Okumura, Y.; Hitomi, Yoshinori; Ozaki, Kazuto; Nagaoka, Satoshi; Yoshida, Akira

doi:10.3177/jnsv.35.333

Cited by 22 publications

(6 citation statements)

References 35 publications

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“…Concentration of cholesterol in the plasma, lipoprotein fractions and liver, phosphatidylcholine:phosphatidylethanolamine ratio in the liver and ratio of 20 : 4n-6 :18 : 2n-6 in the liver phospholipids of growing rats fed diets with different concentrations of methionine (Mean values with their standard errors for ten rats per group) growth increases cholesterol concentrations in the plasma and liver. This is in agreement with several reports showing that methionine supplementation of a low-methionine diet, for example a soyabean protein diet, causes hypercholesterolaemia in rats (Oda et al 1989;Tanaka & Sugano, 1989;Saeki et al 1990;Sugiyama et al 1996Sugiyama et al , 1997.…”

Section: Discussionsupporting

confidence: 93%

Effect of dietary methionine on plasma and liver cholesterol concentrations in rats and expression of hepatic genes involved in cholesterol metabolism

et al. 2006

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Methionine has been shown to increase plasma cholesterol in animals. In the present study, mechanisms were investigated by which methionine could alter cholesterol metabolism. In the first experiment, forty growing rats were fed four casein-based diets differing in methionine content (2·6, 3·5, 4·5 or 6·0 g/kg) for 14 d. In the second experiment, isolated rat hepatocytes were incubated in media supplemented with 50, 100 or 200 mmol/l methionine. Dietary methionine tended to increase plasma homocysteine concentrations in the rats (P¼0·058). A weak positive correlation between circulating homocysteine and plasma cholesterol was observed (R 2 0·27, P,0·01). Rats fed 3·5 g/kg or more of methionine had higher concentrations of cholesterol in their plasma, in lipoprotein fractions of density (r; kg/l) 1·006 , r , 1·063 and r . 1·063, and in liver than rats fed 2·6 g/kg methionine. Rats fed 6 g/kg methionine had a higher hepatic expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase and cholesterol-7a-hydroxylase than rats fed less methionine. The phosphatidylcholine:phosphatidylethanolamine ratio in rat liver increased with rising dietary methionine concentration; the relative mRNA concentrations of phosphatidylethanolamine N-methyltransferase and cystathionine b-synthase remained unaffected. Hepatocytes incubated in media supplemented with 100 or 200 mmol/l methionine had a higher cholesterol synthesis than hepatocytes incubated in a medium supplemented with 50 mmol/l methionine; the LDL uptake in hepatocytes was independent of the methionine concentration of the medium. In conclusion, the present study suggests that dietary methionine induces hypercholesterolaemia at least in part via an enhanced hepatic cholesterol synthesis. Previous studies on the effects of dietary proteins on plasma cholesterol have shown that casein raises serum and LDL-cholesterol concentration in animals and man, whereas plant proteins such as soya protein do not (Ikeda et al.

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Section: Discussionsupporting

confidence: 93%

Effect of dietary methionine on plasma and liver cholesterol concentrations in rats and expression of hepatic genes involved in cholesterol metabolism

et al. 2006

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“…Effect on plasma cholesterol concentration. Several reports have shown that methionine supplementation of a lowmethionine diet, e.g., soybean protein diet, increases the plasma cholesterol concentration in rats (8,(33)(34)(35). These results suggest that methionine has a hypercholesterolemic action at least under the experimental conditions used, although methionine also has been shown to have a hypocholesterolemic action under different dietary conditions.…”

Section: Discussionmentioning

confidence: 88%

Dietary methionine level affects linoleic acid metabolism through phosphatidylethanolamine N‐methylation in rats

Sugiyama¹,

Kumazawa²,

Zhou³

et al. 1998

Lipids

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The effects of dietary methionine level on the profiles of fatty acids and phospholipids and on the plasma cholesterol concentration were investigated to confirm whether the methionine content of dietary proteins is one of the major factors that cause differential effects on lipid metabolism. The effect of dietary supplementation with eritadenine, which is shown to be a potent inhibitor of phosphatidylethanolamine (PE) N-methylation, was also investigated. Rats were fed six diets containing casein (100 g/kg) and amino acid mixture (86.4 g/kg) differing in methionine content (2.5, 4.5, and 7.5 g/kg) and without or with eritadenine supplementation (30 mg/kg) for 14 d. The ratio of arachidonic to linoleic acid of liver microsomal and plasma phosphatidylcholine (PC) was significantly increased as the methionine level of diet was elevated, indicating that dietary methionine stimulates the metabolism of linoleic acid. The PC/PE ratio of liver microsomes and the plasma cholesterol concentration were also increased by dietary methionine. These effects of methionine were completely abolished by eritadenine supplementation The S-adenosylmethionine concentration in the liver reflected the methionine level of diet. These results support the idea that the differential effects of dietary proteins on lipid metabolism might be ascribed, at least in part, to their different methionine contents, and that methionine might exert its effects through alteration of PE N-methylation.

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“…CYP7A1 activity was assayed using the procedure of Oda et al (1989). About 2 g of liver was homogenized in 4 volumes of 0.1 M potassium phosphate buffer (pH 7.4) containing 1 mM EDTA and 50 mM NaF.…”

Section: Methodsmentioning

confidence: 99%

Dietary chitosan enhances hepatic CYP7A1 activity and reduces plasma and liver cholesterol concentrations in diet-induced hypercholesterolemia in rats

et al. 2007

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The present study was performed to elucidate the hypocholesterolemic action of chitosan on the diet-induced hypercholesterolemia in rats. Male Sprague-Dawley rats (n=24) were fed with chitosan-free diet (Control), diets containing 2% or 5% chitosan for 4 weeks. Hypercholesterolemia was induced by adding 1% cholesterol and 0.5% cholic acid to all diets. Body weight gain and food intake of rats did not differ among the groups. The chitosan treated groups showed significant improvement in the plasma concentration of total cholesterol and LDL-cholesterol compared to the control group (p<0.05). Also, the chitosan treated groups decreased the liver concentration of total lipid and total cholesterol compared to the control group (p<0.05). The activity of hepatic cholesterol 7α-hydroxylase (CYP7A1), the rate-limiting enzyme in the conversion of cholesterol to bile acids, was increased by 123% and 165% for the 2% or 5% chitosan diets, respectively. These findings suggest that enhancement of hepatic CYP7A1 activity may be a mechanism, which can partially account for the hypocholesterolemic effect of dietary chitosan in cholesterol metabolism.

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Effect of dietary methionine and polychlorinated biphenyls on cholesterol metabolism in rats fed a diet containing soy protein isolate.

Cited by 22 publications

References 35 publications

Effect of dietary methionine on plasma and liver cholesterol concentrations in rats and expression of hepatic genes involved in cholesterol metabolism

Effect of dietary methionine on plasma and liver cholesterol concentrations in rats and expression of hepatic genes involved in cholesterol metabolism

Dietary methionine level affects linoleic acid metabolism through phosphatidylethanolamine N‐methylation in rats

Dietary chitosan enhances hepatic CYP7A1 activity and reduces plasma and liver cholesterol concentrations in diet-induced hypercholesterolemia in rats

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