title: Study of molecular targets influencing homocysteine and cholesterol metabolism in growing rats by manipulation of dietary selenium and methionine concentrations.
abstract: Inconsistent results exist from human and animal studies for Se and methionine (Met) regarding their influence on homocysteine (HCys) and cholesterol (Chol) metabolism. To elucidate these contradictions, sixty-four weanling albino rats were divided into eight groups of 8, and were fed diets containing four different Se levels (15, 50, 150 and 450 microg/kg) either in combination with the recommended Met level of 3 g/kg (C15, C50, C150 and C450) or with an increased Met concentration of 15 g/kg (M15, M50, M150 and M450) for 8 weeks. Plasma HCys was twofold higher in the Se-supplemented C groups than in group C15. Met addition also doubled plasma HCys compared with the respective C groups. In contrast, the expression of the key enzymes of glutathione biosynthesis in the liver was significantly lowered by Se and in particular by Met. Liver Chol concentration was significantly higher in all the Se-supplemented C and M groups than in groups C15 and M15. Plasma Chol was, however, lowered. The uninfluenced expression of sterol-regulatory element-binding protein 2 and of hydroxymethyl-glutaryl-CoA reductase, the increased LDL receptor expression and the reduced expression of the hepatobiliary Chol exporter ATP-binding-cassette-transporter 8 (ABCG8) by Se and/or Met explain these findings. We conclude that the elevation of plasma HCys in rats by Se and Met results from a higher export into plasma. The fact that Se in particular combined with Met increases liver Chol but reduces plasma Chol should be addressed in future investigations focussing on the regulation of ABCG8, which is also selectively involved in the reverse transport of phytosterols in the small intestine.
authors.affiliation: Institute of Agricultural and Nutritional Sciences, Preventive Nutrition Group, Martin Luther University Halle Wittenberg, Von-Danckelmann-Platz 2, D-06120 Halle/Saale, Germany.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Wolf
authors.forename: Kristin
authors.initials: K
authors.lastname: Mueller
authors.forename: Frank
authors.initials: F
authors.lastname: Hirche
authors.forename: Erika
authors.initials: E
authors.lastname: Most
authors.forename: Josef
authors.initials: J
authors.lastname: Pallauf
authors.forename: Andreas S
authors.initials: AS
authors.lastname: Mueller
mesh_terms: D000071019:ATP Binding Cassette Transporter, Subfamily G, Member 8; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000214:Acyl Coenzyme A / Q000378:metabolism; D000818:Animals; D001798:Blood Proteins / Q000032:analysis; D002784:Cholesterol / Q000378:metabolism*; D004032:Diet; D005978:Glutathione / Q000096:biosynthesis*; D006710:Homocysteine / Q000097:blood*; D008074:Lipoproteins / Q000378:metabolism; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008715:Methionine / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D011973:Receptors, LDL / Q000378:metabolism; D012643:Selenium / Q000008:administration & dosage / Q000494:pharmacology*; D051782:Sterol Regulatory Element Binding Protein 2 / Q000378:metabolism
chemical_list: D000071019:ATP Binding Cassette Transporter, Subfamily G, Member 8; D018528:ATP-Binding Cassette Transporters; C480693:Abcg8 protein, rat; D000214:Acyl Coenzyme A; D001798:Blood Proteins; D008074:Lipoproteins; D011973:Receptors, LDL; D051782:Sterol Regulatory Element Binding Protein 2; D006710:Homocysteine; C015901:glutaryl-coenzyme A; D002784:Cholesterol; D008715:Methionine; D005978:Glutathione; D012643:Selenium