Contribution of plasma proteins to splanchnic and total anabolic utilization of dietary nitrogen in humans

Abstract

Splanchnic tissues are largely involved in the postprandial utilization of dietary amino acids, but little is yet known, particularly in humans, about the relative contributions of different splanchnic protein pools to splanchnic and total postprandial anabolism. Our aim was to develop a compartmental model that could distinguish dietary nitrogen (N) incorporation among splanchnic constitutive, plasma (splanchnic exported), and peripheral proteins after a mixed-protein meal in humans. Eight healthy subjects were fed a single mixed meal containing 15N-labeled soy protein, and dietary N postprandial kinetics were measured in plasma free amino acids, proteins, and urea and urinary urea and ammonia. These experimental data and others previously obtained for dietary N kinetics in ileal effluents under similar experimental conditions were used to develop the compartmental model. Six hours after the mixed-meal ingestion, 31.5, 7.5, and 21% of ingested N were predicted to be incorporated into splanchnic constitutive, splanchnic exported, and peripheral proteins, respectively. The contribution of splanchnic exported proteins to total splanchnic anabolism from dietary N was predicted to be approximately 19% and to remain steady throughout the simulation period. Model behavior and its predictions were strongly in line with current knowledge of the system and the scarce, specific data available in the literature. This model provides the first data concerning the anabolism of splanchnic constitutive proteins in the nonsteady postprandial state in humans. By use of only slightly invasive techniques, this model could help to assess how the splanchnic anabolism is modulated under different nutritional or pathophysiological conditions in humans.

The challenge of diabetes in Asia

“…The model calculations are fairly complex but allow one to predict the kinetics of dietary nitrogen in the body (Juillet et al, 2006). Both the amino acid profi le of the protein and the kinetics of amino acid delivery to the blood can affect the postprandial splanchnic and peripheral uptake of amino acid in humans (Deglaire et al, 2009b;Fouillet et al, 2000Fouillet et al, , 2001Fouillet et al, , 2002bFouillet et al, , 2003Fouillet et al, , 2009Juillet et al, 2008). Increasing protein intake increases splanchnic catabolic use while splanchnic catabolic use and peripheral anabolic use are inversely affected (Fouillet et al, 2009).…”

Postprandial intestinal and whole body nitrogen kinetics and distribution in piglets fed a single meal

“…At 0900 (t ϭ 0), the animals received a single mixed meal providing one-third of their previous daily intake. The meal fed to the piglets consisted of 46 ml/kg body wt of a mix of Litterlife powder and water (1:3) mixed with a trace of a uniformly and intrinsically 15 N-labeled soy protein isolate [150 mg/kg body wt, 98 atom % (AT%)]. The soy protein isolate was prepared as previously described (6,19).…”

“…Because amino acids were neutralized at pH 7 and the resin was under Na ϩ form, it is assumed that no amino acid was retained by the resin. The supernatant containing free N fractions was filtered through 10-kDa cut-off filters (Ultrafree-CL; Amicon, Millipore, Bedford, MA) to eliminate residual protein, freeze-dried, and used for the determination of 15 N enrichment of plasma free N. Resin was washed three times with water. Ammonia was eluted from resin using 2.5 M KHSO 4, and 15 N enrichment of both urea and ammonia plasma was determined by IRMS (Optima; Fisons Instruments, Manchester, UK).…”

“…Because of its rapid growth, the piglet is also a good model to quantify the metabolic fates of dietary N towards disposal or anabolic utilization. Thus the objective of the present study was to determine N kinetics across the portal drained viscera and at the whole body levels in piglets fed a single 15 N-labeled meal, with particular emphasis on the sequential transfer of dietary N to the different body N pools.…”

Enhanced L-citrulline in parboiled paddy rice with watermelon (Citrullus lanatus) juice for preventing Sarcopenia: A preliminary study

“…The success of postprandial aminoacidemia depends on the ability of the intestine and the liver to retain amino acids from protein digestion. While some amino acids are retained by the splanchnic tissue, splanchnic sequestration is accentuated with age and reduces the availability of amino acids for muscle biosynthesis (Jahan-Mihan et al, 2011;Fouillet et al, 2003).…”