title: Variation of betaine, N,N-dimethylglycine, choline, glycerophosphorylcholine, taurine and trimethylamine-N-oxide in the plasma and urine of overweight people with type 2 diabetes over a two-year period.
abstract: BACKGROUND
  Plasma betaine concentrations and urinary betaine excretions have high test-retest reliability. Abnormal betaine excretion is common in diabetes. We aimed to confirm the individuality of plasma betaine and urinary betaine excretion in an overweight population with type 2 diabetes and compare this with the individuality of other osmolytes, one-carbon metabolites and trimethylamine-N-oxide (TMAO), thus assessing their potential usefulness as disease markers.
  
  
  METHODS
  Urine and plasma were collected from overweight subjects with type 2 diabetes at four time points over a two-year period. We measured the concentrations of the osmolytes: betaine, glycerophosphorylcholine (GPC) and taurine, as well as TMAO, and the one-carbon metabolites, N,N-dimethylglycine (DMG) and free choline. Samples were measured using tandem mass spectrometry (LC-MS/MS).
  
  
  RESULTS
  Betaine showed a high degree of individuality (or test-retest reliability) in the plasma (index of individuality = 0.52) and urine (index of individuality = 0.45). Betaine in the plasma had positive and negative log-normal reference change values (RCVs) of 54% and -35%, respectively. The other osmolytes, taurine and GPC were more variable in the plasma of individuals compared to the urine. DMG and choline showed high individuality in the plasma and urine. TMAO was highly variable in the plasma and urine (log-normal RCVs ranging from 403% to -80% in plasma).
  
  
  CONCLUSIONS
  Betaine is highly individual in overweight people with diabetes. Betaine, its metabolite DMG, and precursor choline showed more reliability than the osmolytes, GPC and taurine. The low reliability of TMAO suggests that a single TMAO measurement has low diagnostic value.
authors.affiliation: Biochemistry Unit, Canterbury Health Laboratories, Christchurch, New Zealand Department of Chemistry, University of Canterbury, Christchurch, New Zealand chris.mcentyre@cdhb.health.nz.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: McEntyre
authors.affiliation: Biochemistry Unit, Canterbury Health Laboratories, Christchurch, New Zealand Department of Chemistry, University of Canterbury, Christchurch, New Zealand.
authors.forename: Michael
authors.initials: M
authors.lastname: Lever
authors.affiliation: Department of Pathology, University of Otago, Christchurch; Christchurch, New Zealand.
authors.forename: Stephen T
authors.initials: ST
authors.lastname: Chambers
authors.affiliation: Biochemistry Unit, Canterbury Health Laboratories, Christchurch, New Zealand Department of Pathology, University of Otago, Christchurch; Christchurch, New Zealand.
authors.forename: Peter M
authors.initials: PM
authors.lastname: George
authors.affiliation: Department of Pathology, University of Otago, Christchurch; Christchurch, New Zealand.
authors.forename: Sandy
authors.initials: S
authors.lastname: Slow
authors.affiliation: Biochemistry Unit, Canterbury Health Laboratories, Christchurch, New Zealand.
authors.forename: Jane L
authors.initials: JL
authors.lastname: Elmslie
authors.affiliation: Biochemistry Unit, Canterbury Health Laboratories, Christchurch, New Zealand.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Florkowski
authors.affiliation: Department of Medicine, University of Otago, Christchurch; Christchurch, New Zealand.
authors.forename: Helen
authors.initials: H
authors.lastname: Lunt
authors.affiliation: Department of Medicine, University of Otago, Wellington; Wellington, New Zealand.
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Krebs
mesh_terms: D000368:Aged; D001622:Betaine / Q000097:blood* / Q000652:urine*; D002794:Choline / Q000097:blood / Q000652:urine; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000175:diagnosis / Q000652:urine*; D005260:Female; D005997:Glycerylphosphorylcholine / Q000097:blood / Q000652:urine; D006801:Humans; D008297:Male; D008744:Methylamines / Q000097:blood / Q000652:urine; D008875:Middle Aged; D050177:Overweight / Q000097:blood* / Q000175:diagnosis / Q000652:urine*; D012521:Sarcosine / Q000031:analogs & derivatives / Q000097:blood / Q000652:urine; D013654:Taurine / Q000097:blood / Q000652:urine; D013997:Time Factors
chemical_list: D008744:Methylamines; D013654:Taurine; D001622:Betaine; D005997:Glycerylphosphorylcholine; C025138:dimethylglycine; C023336:trimethylamine; D002794:Choline; D012521:Sarcosine
keywords:  N; Betaine; N-dimethylglycine; choline; coefficient of reliability; diabetes; glycerophosphorylcholine; index of individuality; reference change value; taurine; trimethylamine-N-oxide