title: An evaluation of protein intake for metabolic demands and the quality of dietary protein in rats using an indicator amino acid oxidation method.
abstract: Currently, protein requirements are generally determined based on nitrogen balance studies, but there are a variety of limitations associated with this method. The indicator amino acid oxidation (IAAO) method, with a theoretical base that differs widely from the nitrogen balance method, was developed as an alternative method for humans. The objective of the present study was to evaluate protein intakes for metabolic demands and protein quality, using protein itself, in rats employing the IAAO technique with L-[1-(13)C]phenylalanine. Male Wistar/ST rats (5-6 wk old) received a graded casein (4.3, 8.6, 12.9, 17.2, 21.5, 25.8%), or a wheat gluten (7.2, 10.8, 14.4, 18.0, 21.6, 25.2%) diet, along with L-[1-(13)C]phenylalanine. An isotopic plateau in breath was achieved 210 min after the start of the (13)C ingestion. The protein intakes for metabolic demands were calculated by applying a mixed-effect change-point regression model to breath (13)CO(2) data, which identified a breakpoint at minimal breath (13)CO(2) in response to graded protein intake. The protein intakes for metabolic demands determined by the IAAO method were 13.1 g/kg BW/d for casein and 18.1 g/kg BW/d for wheat gluten, showing a tendency similar to that determined by the nitrogen balance method. These results demonstrated that the IAAO method could be employed to evaluate not only the protein intakes for metabolic demands, but the dietary protein quality in freely living rats, suggesting that this method might be viable in a clinical setting.
authors.affiliation: Division of Applied Life Science, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan.
authors.forename: Aki
authors.initials: A
authors.lastname: Ogawa
authors.forename: Yuka
authors.initials: Y
authors.lastname: Naruse
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Shigemura
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Isao
authors.initials: I
authors.lastname: Suzuki
authors.forename: Sayori
authors.initials: S
authors.lastname: Wada
authors.forename: Kohsuke
authors.initials: K
authors.lastname: Hayamizu
authors.forename: Masashi
authors.initials: M
authors.lastname: Kuwahata
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Kido
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes / Q000378:metabolism; D002364:Caseins / Q000378:metabolism; D004032:Diet / Q000592:standards; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000592:standards; D002149:Energy Intake; D004734:Energy Metabolism; D005983:Glutens / Q000378:metabolism; D008297:Male; D009584:Nitrogen / Q000378:metabolism; D015596:Nutrition Assessment; D009751:Nutritional Requirements; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D014908:Triticum
chemical_list: D000596:Amino Acids; D002247:Carbon Isotopes; D002364:Caseins; D004044:Dietary Proteins; D002245:Carbon Dioxide; D010649:Phenylalanine; D005983:Glutens; D009584:Nitrogen