title: Age-dependent increase in serum levels of indoxyl sulphate and p-cresol sulphate is not related to their precursors: Tryptophan and tyrosine.
abstract: OBJECTIVE
  Retention of indoxyl sulphate and p-cresol sulphate is associated with many diseases. The aim of the present study was to examine serum levels of indoxyl sulphate and p-cresol sulphate, the dynamics of their changes according to age, and their precursors.
  
  
  METHODS
  The study included 180 healthy individuals aged 20-90 years (n = 180), divided into subgroups by decade (n = 30 in each subgroup) and into subgroups of ≥65 years (n = 42) or <65 years (n = 138). Serum indoxyl sulphate and p-cresol sulphate, tryptophan, and tyrosine were measured using high-performance liquid chromatography-mass spectrometry.
  
  
  RESULTS
  The 70-90 years age group had higher indoxyl sulphate than the 50-59 years age group (P = 0.033). The 70-90 years age group had higher p-cresol sulphate than the 20-29 years (P < 0.001), 30-39 years (P < 0.001), 40-49 years (P = 0.007) and 50-59 years (P = 0.001) age groups; the 60-69 years age group had higher p-cresol sulphate than the 20-29 years (P = 0.043) and 30-39 years (P = 0.011) age groups. Indoxyl sulphate and p-cresol sulphate serum levels were higher in those aged ≥65 years. Indoxyl sulphate and p-cresol sulphate serum levels correlated positively with age, but not with tryptophan and tyrosine, respectively.
  
  
  CONCLUSIONS
  Healthy aging is associated with indoxyl sulphate and p-cresol sulphate serum level increases, which are not linked to tryptophan and tyrosine serum levels. Geriatr Gerontol Int 2017; 17: 1022-1026.
authors.affiliation: Department of Immunology, Transplantology, and Internal Diseases, Medical University of Warsaw, Warsaw, Poland.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Wyczalkowska-Tomasik
authors.affiliation: Department of Clinical Nursing, Medical University of Warsaw, Warsaw, Poland.
authors.forename: Bozena
authors.initials: B
authors.lastname: Czarkowska-Paczek
authors.affiliation: Bioanalysis and Drugs Analysis Department, Faculty of Pharmacy, Medical University of Warsaw, Warsaw, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Giebultowicz
authors.affiliation: Bioanalysis and Drugs Analysis Department, Faculty of Pharmacy, Medical University of Warsaw, Warsaw, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Wroczynski
authors.affiliation: Department of Immunology, Transplantology, and Internal Diseases, Medical University of Warsaw, Warsaw, Poland.|Department of Bioinformatics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Leszek
authors.initials: L
authors.lastname: Paczek
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D003408:Cresols / Q000097:blood*; D005260:Female; D006801:Humans; D007200:Indican / Q000097:blood*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D013463:Sulfuric Acid Esters / Q000097:blood*; D014364:Tryptophan / Q000097:blood*; D014443:Tyrosine / Q000097:blood*; D055815:Young Adult
chemical_list: D003408:Cresols; D013463:Sulfuric Acid Esters; D014443:Tyrosine; C408690:4-cresol sulfate; D014364:Tryptophan; D007200:Indican
keywords: aging; indoxyl sulphate; p-cresol sulphate; uremic toxins