title: 13C- and 15N-incorporation of doubly stable isotope labelled Lactobacillus johnsonii in humans.
abstract: OBJECTIVE
  In the present study, Lactobacillus johnsonii (La1) doubly labelled with 15N and 13C (dlLa1) was used to follow the metabolic fate of orally administered dlLa1 in humans.
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  Research Laboratory, Children's Hospital, University of Rostock.
  
  
  METHODS
  A total of 10 healthy adults aged 23-36 y.
  
  
  METHODS
  The subjects received 87 mg/kg body weight viable dlLa1 and 10 g raffinose together with breakfast. Expired air samples were taken over 14 h, whereas urine and faeces were collected over 2 days. A blood sample was taken after 2 h. 13C- and 15N-enrichments were measured by isotope ratio mass spectrometry (SerCon, UK) and H2-concentrations were measured by electrochemical detection (Stimotron, Germany).
  
  
  RESULTS
  The orocaecal transit time (OCTT) was reached after 3.7 h. The 13CO2-exhalation amounted to 8.6% of ingested dose. The urinary excretion of 13C and 15N was 1.3 and 12.4% of ingested dose, respectively, whereas the faecal excretion was 39.9 and 37.6% of ingested dose, respectively. After 2 h, 13C- and 15N-enrichment of fibrinogen amounted to 70 and 90 ppm excess, respectively.
  
  
  CONCLUSIONS
  In comparison to OCTT of 3.7 h, both stable isotopes appear after 30 min in breath and urine, indicating that dlLa1 is rapidly digested in the small bowel before reaching the caecum. This is confirmed by 13C-and 15N-enrichments of blood plasma fractions. The ingestion of dlLa1 led to an excretion of 50% of ingested dose of both stable isotopes.
authors: Research Laboratory, Children's Hospital, University of Rostock, Germany. klaus-dieter.wutzke@med.uni-rostock.de
authors: K D
authors: KD
authors: Wutzke
authors: I
authors: I
authors: Oetjens
mesh_terms: D000284:Administration, Oral; D000328:Adult; D001944:Breath Tests; D002245:Carbon Dioxide / Q000032:analysis; D002247:Carbon Isotopes; D004063:Digestion; D005243:Feces / Q000737:chemistry; D005260:Female; D005772:Gastrointestinal Transit / Q000502:physiology*; D006801:Humans; D007778:Lactobacillus / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D008297:Male; D013058:Mass Spectrometry; D009587:Nitrogen Isotopes; D019936:Probiotics; D011887:Raffinose; D014556:Urine / Q000737:chemistry
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D002245:Carbon Dioxide; D011887:Raffinose