title: Catabolism of amino acids in livers from cafeteria-fed rats.
abstract: Most studies using a hypercaloric diet to induce obesity have focused on the metabolism of fat and carbohydrates. Less concern has been given to the metabolism of amino acids, despite evidence of modifications in nitrogen metabolism during obesity. The aim of this study was to evaluate amino acid metabolism in livers from cafeteria diet-induced obese rats. Blood parameters were analysed, and histological sections of livers were stained with Sudan III. The enzymatic activities of some enzymes were determined in liver homogenates. Gluconeogenesis, ureagenesis, and oxygen consumption were evaluated in rat livers perfused with glutamine, alanine, or ammonium chloride. Compared to control rats, cafeteria-fed rats demonstrated higher levels of triacylglycerol and glucose in the blood and greater accumulation of fat in livers. Gluconeogenesis and urea production in livers perfused with glutamine and alanine at higher concentrations showed a substantial reduction in cafeteria-fed rats. However, no significant difference was observed among groups perfused with ammonium chloride. The activities of the enzymes alanine aminotransferase, glutaminase, and aspartate aminotransferase in the livers were reduced in cafeteria-fed rats. Taken together, these data are consistent with the hypothesis that livers from cafeteria diet-induced obese rats exhibit a limitation in their maximal capacity to metabolise glutamine and alanine to glucose, ammonia, and urea, not because of an impairment in gluconeogenesis and/or ureagenesis, but rather due to a depression in the activities of enzymes that catalyse the initial steps of amino acid metabolism.
authors.affiliation: Department of Biochemistry, Laboratory of Liver Metabolism, University of Maringá, Avenida Colombo 5790, 87020-900 Maringá, Paraná, Brazil.
authors.forename: Cristiane Vizioli
authors.initials: CV
authors.lastname: de Castro Ghizoni
authors.forename: Fabiana Rodrigues Silva
authors.initials: FR
authors.lastname: Gasparin
authors.forename: Antonio Sueiti Maeda
authors.initials: AS
authors.lastname: Júnior
authors.forename: Fernando Olinto
authors.initials: FO
authors.lastname: Carreño
authors.forename: Rodrigo Polimeni
authors.initials: RP
authors.lastname: Constantin
authors.forename: Adelar
authors.initials: A
authors.lastname: Bracht
authors.forename: Emy Luiza
authors.initials: EL
authors.lastname: Ishii Iwamoto
authors.forename: Jorgete
authors.initials: J
authors.lastname: Constantin
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000641:Ammonia / Q000378:metabolism; D000818:Animals; D001219:Aspartate Aminotransferases / Q000378:metabolism; D001786:Blood Glucose; D002784:Cholesterol / Q000097:blood; D059305:Diet, High-Fat / Q000009:adverse effects; D002149:Energy Intake; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D066298:In Vitro Techniques; D019344:Lactic Acid / Q000097:blood; D050356:Lipid Metabolism; D008099:Liver / Q000378:metabolism*; D008297:Male; D056128:Obesity, Abdominal / Q000209:etiology / Q000378:metabolism*; D010101:Oxygen Consumption; D051381:Rats; D017208:Rats, Wistar; D014280:Triglycerides / Q000097:blood; D014508:Urea / Q000378:metabolism
chemical_list: D000596:Amino Acids; D001786:Blood Glucose; D014280:Triglycerides; D019344:Lactic Acid; D000641:Ammonia; D014508:Urea; D002784:Cholesterol; D005969:Glutamate Dehydrogenase; D001219:Aspartate Aminotransferases