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Use of lactose [15N15N]ureide to quantify colonic salvage of urea-nitrogen

Use of lactose [15N15N]ureide to quantify colonic salvage of urea-nitrogen
Use of lactose [15N15N]ureide to quantify colonic salvage of urea-nitrogen

Lactose-ureide was investigated as a potential means to deliver a known dose of 15N label directly to the colon in order to non-invasively quantify urea salvage. Two lactose-ureides, labelled with either 13C or 15N on the urea moiety, were synthesised and analysed for purity. Following this, a clinical trial was marginally adequate in healthy adult individuals who had accommodated to a diet marginally adequate in protein were given oral doses of the lactose-ureides, and the excretion of label was followed. Results from the lactose [13C]ureide administration demonstrated that little of the dose was excreted on breath before 6 h, with about 80% undergoing fermentation and hydrolysis over a 48 h period, leading to the conclusion that lactose-ureide is a suitable vehicle to non-invasively deliver label to the colon intact. An analysis of urine and stool allowed a quantification of the fate of lactose [15N15N]ureide, demonstrating that about 5% was excreted as urinary [15N15N]urea, 30% as urinary [14N15N]urea, and 22% in the stool fraction. It was concluded that, of the 15N label available to the body over half was retained on average. The discovery of label associated with lysine in the bacterial fraction of stool further suggests that de novo formed essential amino acids are available to the host. Additionally, a methodology was developed in order to directly address the potential functional significance of lysine formed de novo to the body, by attempting to separate the lysine fraction of apoliprotein B-100 hydrolysates in a quantity sufficient to determine changes in 15N enrichment using c-IRMS. An accurate detection of changes in 15N enrichment as low as 0.002 APE in samples containing 3.3 ug lysine-N was achieved, and a distinction was made between the fate of lysine, lysine-N, and lysine-15N through the analytical system.

A method has been developed which allows the salvage of urea-N to be non-invasively quantified in normal adults.

University of Southampton
Bundy, Rafe
1768a3e2-eb22-4fec-a9f3-72956216a7d8
Bundy, Rafe
1768a3e2-eb22-4fec-a9f3-72956216a7d8

Bundy, Rafe (1997) Use of lactose [15N15N]ureide to quantify colonic salvage of urea-nitrogen. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Lactose-ureide was investigated as a potential means to deliver a known dose of 15N label directly to the colon in order to non-invasively quantify urea salvage. Two lactose-ureides, labelled with either 13C or 15N on the urea moiety, were synthesised and analysed for purity. Following this, a clinical trial was marginally adequate in healthy adult individuals who had accommodated to a diet marginally adequate in protein were given oral doses of the lactose-ureides, and the excretion of label was followed. Results from the lactose [13C]ureide administration demonstrated that little of the dose was excreted on breath before 6 h, with about 80% undergoing fermentation and hydrolysis over a 48 h period, leading to the conclusion that lactose-ureide is a suitable vehicle to non-invasively deliver label to the colon intact. An analysis of urine and stool allowed a quantification of the fate of lactose [15N15N]ureide, demonstrating that about 5% was excreted as urinary [15N15N]urea, 30% as urinary [14N15N]urea, and 22% in the stool fraction. It was concluded that, of the 15N label available to the body over half was retained on average. The discovery of label associated with lysine in the bacterial fraction of stool further suggests that de novo formed essential amino acids are available to the host. Additionally, a methodology was developed in order to directly address the potential functional significance of lysine formed de novo to the body, by attempting to separate the lysine fraction of apoliprotein B-100 hydrolysates in a quantity sufficient to determine changes in 15N enrichment using c-IRMS. An accurate detection of changes in 15N enrichment as low as 0.002 APE in samples containing 3.3 ug lysine-N was achieved, and a distinction was made between the fate of lysine, lysine-N, and lysine-15N through the analytical system.

A method has been developed which allows the salvage of urea-N to be non-invasively quantified in normal adults.

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Published date: 1997

Identifiers

Local EPrints ID: 462978
URI: http://eprints.soton.ac.uk/id/eprint/462978
PURE UUID: 5d8ed57b-d811-4ba2-8c25-1e0b69335f32

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Date deposited: 04 Jul 2022 20:33
Last modified: 04 Jul 2022 21:36

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Contributors

Author: Rafe Bundy

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