The effect of pre- and probiotics on the colonic ammonia metabolism in humans as measured by lactose-[15N2]ureide

Abstract

Background: The evaluation of ammonia detoxification by pre-and probiotics by means of colonic lactose-[ 15 N 2 ]ureide ( 15 N-LU) degradation is of great interest both scientifically and in terms of nutrition physiology. Objective: Pre-and probiotics were supplemented in healthy adults to evaluate the effect of the ammonia metabolism in the human colon by means of 15 N-LU. Methods: A total of 14 participants aged 20-28 years daily received a regular diet either without (no treatment) or with supplementation of 30 g fibre of potatoes (FPs), 30 g wrinkle pea starch (WPS, resistant starch content: 12 and 70%, respectively) and 375 g Lactobacillus acidophilus (LC1) yoghurt, over a 10-day period in a randomised order. After 1 week, 5.7 mg/kg body weight 15 N-LU was administered together with breakfast. A venous blood sample was taken after 6 h. Urine and faeces were collected over a period of 48 and 72 h, respectively. The 15 N abundances were measured by isotope ratio mass spectrometry. Results: The mean renal 15 N-excretion differed significantly between the supplementation of FP and no treatment (32.5 versus 46.3%, P ¼ 0.034), FP and LC1 (32.5 versus 51.6%, P ¼ 0.001), and WPS and LC1 (38.5 versus 51.6%, P ¼ 0.048). The mean faecal 15 N-excretion amounted to 42.7% (no treatment), 59.7% (FP), 41.8% (WPS) and 44.0% (LC1). In comparison with no treatment, the urinary 15 NH 3 -enrichment was significantly decreased at 16 h after FP supplementation. Conclusion: The prebiotic intake of FP and WPS lowered the colonic generation and the renal excretion of toxic 15 NH 3 , respectively, when using 15 N-LU as a xenobiotic marker.

Effect of alcohol consumption on whole-body protein turnover in healthy adults

“…After 15 N-YP ingestion, the urine was collected at 2, 4, and 6 h intervals over a period of 48 h. Faeces scraped from polyvinyl film were also collected quantitatively over 2 days. Urine volumes and faecal masses were homogenised, recorded, and 1 ml or 1 g, respectively, of each sample was stored at −20 • C until analysis [15]. On the 11th day, the subjects began to consume 0.4 ml ethanol kg −1 day −1 equivalent to 3.3 ml red wine kg −1 day −1 (Dry Bordeaux, 12.0 vol% ethanol) within 30 min together with dinner at 18:00 for the last 10 days of the study.…”

“…Urine and faeces samples were combusted in the elemental analyser SL TM (SerCon, Crewe, UK) using copper oxide at 900 • C and subsequently reduced to nitrogen gas using copper at 600 • C. Thereafter, the 15 N-abundances were measured by isotope ratio mass spectrometry (Tracer mass 20-20 TM , SerCon), as detailed previously [15][16][17][18][19]. …”

“…However, little is known about possible changes in the whole-body protein turnover rate (Q) and other parameters of the protein metabolism in response to the consumption of alcohol in moderate dosages, which is also of great scientific interest. Our Research Laboratory has long-time experience in 15 N-labelling and in using yeast protein for tracer kinetic studies in humans [9][10][11][12]. The particular advantage of applying a universally 15 N-labelled yeast protein ( 15 N-YP) for evaluating the protein flux rates is the fact that the 15 N-dose is spread among all proteinogenic amino acids.…”

“…Our Research Laboratory has long-time experience in 15 N-labelling and in using yeast protein for tracer kinetic studies in humans [9][10][11][12]. The particular advantage of applying a universally 15 N-labelled yeast protein ( 15 N-YP) for evaluating the protein flux rates is the fact that the 15 N-dose is spread among all proteinogenic amino acids. In contrast to the application of a single 15 N-labelled amino acid as a tracer substance, a 15 N-YP gives a more representative picture of the protein metabolism, particularly when specific metabolic conditions are to be examined [9][10][11][12].…”

“…The data were expressed either as 15 N-enrichment in at% excess (measured 15 N-abundance in at% minus natural 15 N-abundance of 0.3663 at%) or as percentage cumulative urinary and faecal 15 N-excretion.2.3.1. Percentage of cumulative urinary and faecal 15 N-excretionThe 15 N-excretion (E) in a specified urine or faeces sample is the product of the measured 15 Nenrichment in at% excess (APE sample ), the urine volume (vol) or the faecal mass (m) in ml or g, respectively, and the N-concentration (c N ) of the urine or faeces sample in mg ml −1 or mg g −1 , respectively, divided by 100:E = APE sample vol(m)c N 100 .The percentage of cumulative15 N-excretion (PCE) is the urinary or faecal 15 N-excretion (E) in mg, respectively, multiplied by 100 divided by the 15 N-excess dose minus the faecal 15 N-excretion (D) in mg [15]: PCE = E100 D .…”