Original Article
European Journal of Clinical Nutrition (2006) 60, 847–852. doi:10.1038/sj.ejcn.1602389; published online 1 February 2006
15N-excretion of heat-killed Lactobacillus casei in humans
Guarantor: KD Wutzke.
Contributors: VS was principal investigator and doctoral candidate of KDW.
1Children's Hospital, Research Laboratory, University of Rostock, Rostock, Germany
Correspondence: Professor KD Wutzke, Children's Hospital, Research Laboratory, University of Rostock, Rembrandtstrasse 16/17, D-18055 Rostock, Germany. E-mail: klaus-dieter.wutzke@med.uni-rostock.de
Received 26 June 2005; Revised 11 November 2005; Accepted 2 December 2005; Published online 1 February 2006.
Abstract
Objective:
In the present study, Lactobacillus casei (L. casei) labelled with 15N was used to follow the metabolic fate of orally administered heat-killed 15N-labelled L. casei (15N-L.casei) in humans.
Design:
Experimental study.
Setting:
University of Rostock, Children's Hospital, Research Laboratory.
Subjects:
Twelve healthy adults aged 23–32 years.
Intervention:
The subjects received 36 mg/kg body weight heat-killed 15N-L.casei and 500 mg Lactose-[13C]ureide 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).
Results:
The orocaecal transit time (OCTT) was reached after 4.1 h. The urinary 15N-excretion was 9.3% of the ingested dose, whereas the faecal excretion was 65.1% of the ingested dose. After 2 h, 15N-enrichment of supernatant, fibrinogen, and plasma protein precipitate amounted to 254, 11, and 2 p.p.m. excess, respectively.
Conclusions:
In comparison to the OCTT of 4.1 h, 15N-enrichment in urinary ammonia and urinary total nitrogen already began to rise 30 min after 15N-L.casei ingestion, indicating that 15N-L.casei is rapidly digested in the small bowel. This is confirmed by 15N-enrichments of blood plasma fractions. The ingestion of heat-killed 15N-L.casei led to a total excretion of 74.4% of the ingested 15N-dose.
Keywords:
15N-labelled Lactobacillus casei, 15N-excretion, lactose-[13C]ureide, orocaecal transit time
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