Endogenous amino acid flow at the terminal ileum of adult humans determined following the ingestion of a single protein‐free meal

Abstract

Abstract:The study sought to determine endogenous total nitrogen and amino acid flows at the terminal ileum of adult humans. Six adults (65f 10 kg bodyweight) with well-established ileostomies fasted for 14 h before consuming a single protein-free meal (240 g) containing Celite (acid-insoluble ash) as an indigestible marker. Ileal digesta were collected for 8 h after the meal and endogenous flows were determined by reference to the marker. The mean ( f SE) total 8 h output of digesta dry matter was 9.1 (k3.51) g. The mean ileal flow of total nitrogen was 4.38 (f 0.770), with the mean amino acid flows ranging from 0.17 (fO.009) for methionine to 2.26 (fO.258) for glutamic acid (mg g-' food dry matter intake).

Quantitative and qualitative changes in endogenous nitrogen components along the small intestine of the calf

“…By contrast, it differed from that of rats 12 and pigs. 5,6,12,26,27 (w 2 b 200) and, to a lesser extent humans 5 (w 2 = 78). Of all the AAs determined, the levels of proline and glycine were particularly variable.…”

“…We compared the AA compositions of ileal digesta obtained in our experiment with those corresponding to fresh milk and lactose (Toullec R, unpublished) or non-clotting milk 25 and with those published for various animal species. 5,6,12,26,27 For pigs we calculated a mean composition from various data.…”

“…2,3 To assess the nutritive value of a protein source, a partition of the undigested protein at the ileum between endogenous and dietary fractions should be made, thus allowing the true digestibility to be calculated. 4 In pigs, several approaches have been designed to quantify the¯ow of endogenous protein at the terminal ileum, including protein-free diets, 5,6 the regression/extrapolation method 7±10 and the use of completely digestible proteins. 11,12 The endogenous losses determined with these methods may be termed basal or non-speci®c.…”

Box-modeling of 15N/14N in mammals

“…Urea hydrolysis (U hyd ) 0.16·W 0.79 Assimon and Stein (1994); Barboza et al (1997); Chikunya et al (1996); Chilcott et al (1985); Cocimano and Leng (1967) Fractionation factor during the deamination of a protein into amino acids e (see Table 2 for the values) 15 a TA Fractionation factor during the transamination of a protein into amino acids e (see Table 2 for the values) 15 a OS Fractionation factor associated to the change of the oxidation state of N between a reactant and the product e (see Table 2 for the values) a Body mass (W) is in kg b These allometric relations are calculated for a zero N balance using Il deg =0.04·W 0.91 (Donkoh et al 1994;Mariscal-Landin et al 1995;Montagne et al 2000;Morens 2002;Rowan et al 1993;Tome´and Bos 2000); P exc =0.38(U exc +A exc ) (Canh et al 1997;Sponheimer et al 2003;Tome´and Bos 2000); A exc =0.1·U exc (Canh et al 1997;Petersen et al 1998) c Deduced from the fact that the protein content of an animal is roughly equal to 15% of its body weight and that proteins are composed of 15% of N d Deduced from the stoechiometry of N for the urea synthesis reaction e The conversion in the a form is given by the relationship: 10 3 ln(a)=D…”

Gut luminal endogenous protein: Implications for the determination of ileal amino acid digestibility in humans

“…The overall mean endogenous ileal amino acid flows are given in Table 2. Once again, the endogenous ileal flows for the individual amino acids tended to be higher than their (31,32,33) protein-free counterparts (Table 1). When, however, the ileal amino acid losses were expressed relative to lysine at 100 units (Tables 1 & 2) the relative amino acid compositions of the two types of digesta were more similar though some considerable differences still persisted for some amino acids.…”