Peripheral and Splanchnic Metabolism of Dietary Nitrogen Are Differently Affected by the Protein Source in Humans as Assessed by Compartmental Modeling

Abstract

We used a previously developed compartmental model to assess the postprandial distribution and metabolism of dietary nitrogen (N) in the splanchnic and peripheral areas after the ingestion of a single mixed meal containing either (15)N-labeled milk or soy purified protein. Although the lower whole-body retention of dietary N from soy protein was measured experimentally, the splanchnic retention of dietary N was predicted by the model not to be affected by the protein source, and its incorporation into splanchnic proteins was predicted to reach approximately 35% of ingested N at 8 h after both meals. However, dietary N intestinal absorption and its appearance in splanchnic free amino acids were predicted to be more rapid from soy protein and were associated with a higher deamination, concomitant with a higher efficiency of incorporation of dietary N into proteins in the splanchnic bed. In contrast, soy protein was predicted to cause a reduction in peripheral dietary N uptake, as a consequence of both similar splanchnic retention and increased oxidation compared with milk protein. In addition, protein synthesis efficiency was reduced in the peripheral area after soy protein intake, leading to dietary N incorporation in peripheral proteins that fell from 26 to 19% of ingested N 8 h after milk and soy protein ingestion, respectively. Such a model thus enables a description of the processes involved in the differential metabolic utilization of dietary proteins and constitutes a valuable tool for further definition of the notion of protein quality during the period of protein gain.

Nutritional Strategies to Promote Postexercise Recovery

“…It appears that milk , and net balance (N) at rest in the fasted state, after exercise in the fasted state, after exercise with carbohydrate supplementation, and after exercise with protein supplementation. Data adapted from Biolo, Williams, Fleming, and Wolfe (1999) ; ;Borsheim, Cree, et al (2004);Borsheim, Tipton, Wolf, and Wolfe (2002); Howarth et al (2009);Koopman, Wagenmakers, et al (2005);Miller, Tipton, Chinkes, Wolf, and Wolfe (2003); Phillips et al (1997), Pitkanen et al (2003), Rasmussen, Tipton, Miller, Wolf, and Wolfe (2000); Roy, Tarnopolsky, MacDougall, Fowles, and Yarasheski (1997) ;Tipton, Ferrando, Phillips, Doyle, and Wolfe (1999);and Tipton, Ferrando, Williams, and Wolfe (1996). proteins and their isolated forms, whey and casein, offer an anabolic advantage over soy protein in promoting muscle hypertrophy (Fouillet, Mariotti, Gaudichon, Bos, & Tome, 2002;Wilkinson et al, 2007). Casein and whey protein seem to have distinct anabolic properties, which is attributed to differences in digestion and absorption kinetics (Boirie et al, 1997;Dangin et al, 2001;Dangin et al, 2003;Tipton et al, 2004a).…”

Consumption of fat-free fluid milk after resistance exercise promotes greater lean mass accretion than does consumption of soy or carbohydrate in young, novice, male weightlifters

“…In addition, ingestion of intrinsically labeled soy and milk proteins resulted in greater incorporation of nitrogen into serum proteins and urea when soy was ingested (17). The suggestion from these results (17), and from a modeling approach (18), was that proteins from soy are directed toward splanchnic metabolism, whereas milk proteins are directed to peripheral sites.…”

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).…”