title: Changes in salivary amino acid composition during aging.
abstract: BACKGROUND
  it has been suggested that the features of saliva reflect the physiological and psychological state of primates as well as subprimates, however, studies revealing the relationship between aging and the concentrations of salivary amino acids are limited. In order to better understand their physiological role, age-related changes of salivary amino acids were investigated.
  
  
  METHODS
  forty-five participants including 5 children [6.60 ± 1.67 (5-9) years old], 20 adults [46.55 ± 14.68 (23-64) years old), and 20 senior citizens [71.60 ± 4.27 (66-82) years old] took part in this study. Whole saliva (one sample per each person) was collected in the daytime (10:00-11:00 or 14:00-15:00). Salivary amino acids were recovered after deproteinization with 5% trichloroacetic acid and determined by an amino acid analyzer.
  
  
  RESULTS
  glycine was the most abundant amino acid in the saliva. Glycine and lysine levels increased significantly (p<0.05) with aging, regardless of gender difference. When the glycine and lysine levels were plotted, much higher correlation (p<0.001) was observed. On the other hand, there was no significant correlation between the salivary concentration of glutamic acid or histidine and age.
  
  
  CONCLUSIONS
  salivary amino acid levels may be regarded as markers of aging.
authors.affiliation: Division of Oral Diagnosis, Department of Diagnosis and Therapeutic Sciences, Meikai University School of Dentistry, Sakado, Saitama 350-0283, Japan. stanaka@dent.meikai.ac.jp
authors.forename: Shoji
authors.initials: S
authors.lastname: Tanaka
authors.forename: Mamoru
authors.initials: M
authors.lastname: Machino
authors.forename: Sayoko
authors.initials: S
authors.lastname: Akita
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Yokote
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sakagami
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D000596:Amino Acids / Q000032:analysis*; D002648:Child; D002675:Child, Preschool; D005260:Female; D018698:Glutamic Acid / Q000032:analysis; D005998:Glycine / Q000032:analysis; D006639:Histidine / Q000032:analysis; D006801:Humans; D008239:Lysine / Q000032:analysis; D008297:Male; D008875:Middle Aged; D012463:Saliva / Q000737:chemistry*; D012737:Sex Factors
chemical_list: D000596:Amino Acids; D018698:Glutamic Acid; D006639:Histidine; D008239:Lysine; D005998:Glycine