title: Long-term effects of histidine depletion on whole-body protein metabolism in healthy adults.
abstract: The essentiality of histidine in healthy adults is a controversial topic. To study the potential metabolic effects of a lack of exogenous histidine, four healthy adults consumed a histidine-free diet, with adequate energy and 1.0 g/(kg. d) of an L-amino acid mixture for 48 d. Protein metabolism was monitored every 4 d by using indicator amino acid (L-[1-(13)C]phenylalanine) oxidation (in four subjects) and [(15)N]glycine (in one subject). Urine samples (24-h) were collected for measurement of urea, total nitrogen, creatinine, 3-methylhistidine (3-MH), histidine and beta-alanine. Albumin, transferrin and hematologic concentrations were measured on d 0, 24 and 48. Urinary excretion of nitrogen, urea, creatinine and 3-MH were not affected by the histidine-free diet. However, there was a significant (P < 0.001) linear decline (24-28%) in whole-body protein turnover. Significant (P < 0.05) decreases in albumin (12%), transferrin (17%) and hemoglobin (Hb) (11%) concentrations occurred slowly over the histidine depletion period. The urinary excretion of beta-alanine (an index of carnosine catabolism) generally increased in the smallest subject during the consumption of histidine-free diet. This study demonstrates that a lack of histidine in the diet for a prolonged period resulted in an accommodation of protein turnover and phenylalanine oxidation, measured by the (13)C-phenylalanine indicator amino acid. The extensive metabolic accommodation, together with decreases in Hb, albumin and transferrin during histidine depletion, leaves unresolved the issue of whether histidine is a dietary essential amino acid in healthy adults.
authors.affiliation: Department of Nutritional Sciences and. Paediatrics, University of Toronto, Toronto, Canada M5S 3E2.
authors.forename: Wantanee
authors.initials: W
authors.lastname: Kriengsinyos
authors.forename: Mahroukh
authors.initials: M
authors.lastname: Rafii
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Wykes
authors.forename: Ronald O
authors.initials: RO
authors.lastname: Ball
authors.forename: Paul B
authors.initials: PB
authors.lastname: Pencharz
mesh_terms: D000328:Adult; D002247:Carbon Isotopes; D003404:Creatinine / Q000652:urine; D004032:Diet; D004909:Erythrocyte Indices; D005260:Female; D005998:Glycine / Q000378:metabolism; D006454:Hemoglobins / Q000378:metabolism; D006639:Histidine / Q000008:administration & dosage / Q000097:blood / Q000172:deficiency* / Q000652:urine; D006801:Humans; D007700:Kinetics; D016014:Linear Models; D008297:Male; D008762:Methylhistidines / Q000652:urine; D009584:Nitrogen / Q000652:urine; D009587:Nitrogen Isotopes; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D012709:Serum Albumin / Q000378:metabolism; D014168:Transferrin / Q000378:metabolism; D014508:Urea / Q000652:urine; D015091:beta-Alanine / Q000652:urine
chemical_list: D002247:Carbon Isotopes; D006454:Hemoglobins; D008762:Methylhistidines; D009587:Nitrogen Isotopes; D011506:Proteins; D012709:Serum Albumin; D014168:Transferrin; D015091:beta-Alanine; D010649:Phenylalanine; D006639:Histidine; D014508:Urea; D003404:Creatinine; C028118:3-methylhistidine; D009584:Nitrogen; D005998:Glycine