title: Associations among the plasma amino acid profile, obesity, and glucose metabolism in Japanese adults with normal glucose tolerance.
abstract: BACKGROUND
  Amino acids (AAs) are emerging as a new class of effective molecules in the etiology of obesity and diabetes mellitus. However, most investigations have focused on subjects with obesity and/or impaired glucose regulation; the possible involvement of AAs in the initial phase of glucose dysregulation remains poorly understood. Furthermore, little attention has been given to possible associations between the pattern/degree of fat deposition and the plasma AA profile. Our objective was therefore to determine the relationships between plasma AA concentrations and the type/degree of obesity and glucose regulation in Japanese adults with normal glucose tolerance.
  
  
  METHODS
  Eighty-three subjects with normal glucose tolerance were classified as obese or nonobese and as visceral obesity or nonvisceral obesity. Correlations between the plasma levels of 23 AAs and somatometric measurements, visceral fat area (VFA), subcutaneous fat area (SFA), and 75-g oral glucose tolerance test results were analyzed.
  
  
  RESULTS
  Obesity or visceral obesity was associated with higher levels of branched-chain AAs (isoleucine, leucine, and valine), lysine, tryptophan, cystine, and glutamate but lower levels of asparagine, citrulline, glutamine, glycine, and serine (p < 0.04). Age- and gender-adjusted analyses indicated that VFA was positively correlated with tryptophan and glutamate levels, whereas VFA and SFA were negatively correlated with citrulline, glutamine, and glycine levels (p < 0.05). The fasting and 2-h plasma glucose levels or the homeostasis model assessment of insulin resistance were positively correlated with valine, glutamate, and tyrosine levels but negatively correlated with citrulline, glutamine, and glycine levels. The homeostasis model assessment for the β-cell function index was positively correlated with leucine, tryptophan, valine, and glutamate levels but negatively correlated with citrulline, glutamine, glycine, and serine levels (p < 0.05).
  
  
  CONCLUSIONS
  The present study identified specific associations between 10 AAs and the type/degree of obesity, and indices of glucose/insulin regulation, in Japanese adults with preserved glucose metabolism. With the growing concern about the increasing prevalence of obesity and diabetes, the possible roles of these AAs as early markers and/or precursors warrant further investigation.
authors.affiliation: First Department of Medicine, Hokkaido University Hospital, North 14, West 5, Kita-ku, Sapporo, 060-8648 Japan.
authors.forename: Chisa
authors.initials: C
authors.lastname: Takashina
authors.affiliation: First Department of Medicine, Hokkaido University Hospital, North 14, West 5, Kita-ku, Sapporo, 060-8648 Japan.
authors.forename: Ichizo
authors.initials: I
authors.lastname: Tsujino
authors.affiliation: First Department of Medicine, Hokkaido University Hospital, North 14, West 5, Kita-ku, Sapporo, 060-8648 Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Watanabe
authors.affiliation: First Department of Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Sakaue
authors.affiliation: First Department of Medicine, Hokkaido University Hospital, North 14, West 5, Kita-ku, Sapporo, 060-8648 Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ikeda
authors.affiliation: First Department of Medicine, Hokkaido University Hospital, North 14, West 5, Kita-ku, Sapporo, 060-8648 Japan.
authors.forename: Asuka
authors.initials: A
authors.lastname: Yamada
authors.affiliation: First Department of Medicine, Hokkaido University Hospital, North 14, West 5, Kita-ku, Sapporo, 060-8648 Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Sato
authors.affiliation: First Department of Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ohira
authors.affiliation: Department of Human Developmental Science, Faculty of Education, Hokkaido University, Sapporo, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Otsuka
authors.affiliation: Department of Diagnostic and Interventional Radiology, Hokkaido University Hospital, Sapporo, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Oyama-Manabe
authors.affiliation: Department of Biostatistics, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Yoichi M
authors.initials: YM
authors.lastname: Ito
authors.affiliation: First Department of Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
authors.forename: Masaharu
authors.initials: M
authors.lastname: Nishimura
keywords: Branched-chain amino acid; Glutamate; Glutamine; Glycine; Insulin resistance; Insulin secretion; Oral glucose tolerance test; Visceral obesity