Daily delivery of dietary nitrogen to the periphery is stable in rats adapted to increased protein intake

Morens, Céline; Gaudichon, Claire; Fromentin, Gilles; Marsset-Baglieri, Agnès; Bensaı̈d, Ahmed; Larue-Achagiotis, Christiane; Luengo, Catherine; Tomé, Daniel

doi:10.1152/ajpendo.2001.281.4.e826

Cited by 44 publications

(48 citation statements)

References 47 publications

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“…Subcutaneous fat pad measurements and expansion of fat mass revealed remarkable differences between the two groups. These results are in agreement with others (37,38) and can be explained, to some extent, by the reduction in caloric intake, but we also observed increased UCP-1 levels that may reflect an increase in energy expenditure.…”

Section: Discussionsupporting

confidence: 94%

A Central Role for Neuronal AMP-Activated Protein Kinase (AMPK) and Mammalian Target of Rapamycin (mTOR) in High-Protein Diet–Induced Weight Loss

et al. 2008

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OBJECTIVE-A high-protein diet (HPD) is known to promote the reduction of body fat, but the mechanisms underlying this change are unclear. AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) function as majors regulators of cellular metabolism that respond to changes in energy status, and recent data demonstrated that they also play a critical role in systemic energy balance. Here, we sought to determine whether the response of the AMPK and mTOR pathways could contribute to the molecular effects of an HPD.RESEARCH DESIGN AND METHODS-Western blotting, confocal microscopy, chromatography, light microscopy, and RT-PCR assays were combined to explore the anorexigenic effects of an HPD.RESULTS-An HPD reduced food intake and induced weight loss in both normal rats and ob/ob mice. The intracerebroventricular administration of leucine reduced food intake, and the magnitude of weight loss and reduction of food intake in a leucine-supplemented diet are similar to that achieved by HPD in normal rats and in ob/ob mice, suggesting that leucine is a major component of the effects of an HPD. Leucine and HPD decrease AMPK and increase mTOR activity in the hypothalamus, leading to inhibition of neuropeptide Y and stimulation of pro-opiomelanocortin expression. Consistent with a cross-regulation between AMPK and mTOR to control food intake, our data show that the activation of these enzymes occurs in the same specific neuronal subtypes.CONCLUSIONS-These findings provide support for the hypothesis that AMPK and mTOR interact in the hypothalamus to regulate feeding during HPD in a leucine-dependent manner.

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Section: Discussionsupporting

confidence: 94%

A Central Role for Neuronal AMP-Activated Protein Kinase (AMPK) and Mammalian Target of Rapamycin (mTOR) in High-Protein Diet–Induced Weight Loss

et al. 2008

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“…A crucial question regarding dietary availability is the metabolic fate of dietary lysine used in first pass by the PDV tissues. Previous results might indicate that the large firstpass utilization of dietary lysine in the present study resulted in a higher fractional rate of oxidation (10,21,22,43). Further study is warranted to establish how feeding modality affects the proportion of dietary lysine that is retained via incorporation into protein or irreversibly lost via oxidative metabolism within the PDV tissues.…”

Section: Discussionmentioning

confidence: 72%

Intestinal lysine metabolism is driven by the enteral availability of dietary lysine in piglets fed a bolus meal

Bos

Stoll²,

Fouillet³

et al. 2003

American Journal of Physiology-Endocrinology and Metabolism

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Intestinal lysine metabolism is driven by the enteral availability of dietary lysine in piglets fed a bolus meal. Am J Physiol Endocrinol Metab 285: E1246-E1257, 2003. First published August 8, 2003 10.1152/ajpendo.00150.2003.-Previous steady-state continuous-feeding studies have shown that the gut mucosa removes substantial amounts of both dietary and systemic amino acids. However, enteral nutrition is often given under non-steady-state conditions as a bolus meal, and this has been shown to influence systemic metabolism. Therefore, our aim was to quantify the relative metabolism of dietary and systemic lysine by the portal-drained viscera (PDV) under non-steady-state conditions after a single bolus meal. Five 28-day-old piglets implanted with arterial, venous, and portal catheters and with an ultrasonic portal flow probe were given an oral bolus feeding of a milk formula containing a trace quantity of intrinsically 15 N-labeled soy protein and a continuous intravenous infusion of [U-13 C]lysine for 8 h. Total lysine use by the PDV was maximal 1 h after the meal (891 mol ⅐ kg Ϫ1 ⅐ h Ϫ1 ) and was predominantly of dietary origin (89%), paralleling the enteral delivery of dietary lysine. Intestinal lysine use returned to a low level after 4 h postprandially and was derived exclusively from the arterial supply until 8 h. Cumulative systemic appearance of dietary lysine reached 44 and 80% of the ingested amount 4 and 8 h after the meal, respectively, whereas the PDV first-pass use of dietary lysine was 55 and 32% of the intake for these two periods, respectively. We conclude that the first-pass utilization rate of dietary lysine by the PDV is directly increased by the enteral lysine availability and that it is higher with a bolus than with continuous oral feeding.amino acid metabolism; dietary amino acids; portal-drained viscera; nonsteady state STUDIES IN ANIMALS have shown that, during feeding, amino acid utilization by gut tissues is a major determinant of the systemic availability of both essential and nonessential dietary amino acids (27). Indeed, the intestine removes a substantial part of the absorbed dietary essential amino acids to fulfill its own metabolic needs for purposes of protein biosynthesis and energy production (37,39,43,47). This phenomenon can decrease the systemic availability of essential amino acids to the body (39,45,49). However, the gut can also be considered as a buffer, sequestering dietary amino acids through protein synthesis during feeding when they are available in excess, and then releasing them in the fasted state to the peripheral pools when their availability is decreased (12,33).Nonessential amino acids are used by the intestine in synthetic pathways and energy production. They also undergo several metabolic interconversions (in particular, glutamate removal and arginine and alanine synthesis), producing a different pattern of amino acids released in the portal circulation than that of dietary protein (28,29,39,41,43,48).Although the intestine is mainly supplied with dietary ami...

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“…In vivo, amino acids display an anabolic effect (Giordano et al, 1996;Volpi et al, 1996) and were shown to stimulate muscle protein synthesis (Bohe et al, 2003;Liu et al, 2002;Nair and Short, 2005;Nygren and Nair, 2003). There was no effect of a dietary protein level above the PRI on muscle mass and protein content, and a high protein diet of around 2 g/kg body weight per day has not been demonstrated to modulate skeletal protein synthesis in both exercising and non-exercising human subjects (Bolster et al, 2005;IoM, 2005;Juillet et al, 2008) or animals (Almurshed and Grunewald, 2000;Chevalier et al, 2009;Masanés et al, 1999;Morens et al, 2001;Taillandier et al, 2003). However, increasing protein intake above the individual requirement increases amino acid oxidation and modifies protein turnover.…”

Section: Muscle Massmentioning

confidence: 99%

Scientific Opinion on Dietary Reference Values for protein

Products¹

2012

EFSA Journal

324

152

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This opinion of the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) deals with the setting of Dietary Reference Values (DRVs) for protein. The Panel concludes that a Population Reference Intake (PRI) can be derived from nitrogen balance studies. Several health outcomes possibly associated with protein intake were also considered but data were found to be insufficient to establish DRVs. For healthy adults of both sexes, the average requirement (AR) is 0.66 g protein/kg body weight per day based on nitrogen balance data. Considering the 97.5 th percentile of the distribution of the requirement and assuming an efficiency of utilisation of dietary protein for maintenance of 47 %, the PRI for adults of all ages was estimated to be 0.83 g protein/kg body weight per day and is applicable both to high quality protein and to protein in mixed diets. For children from six months onwards, age-dependent requirements for growth estimated from average daily rates of protein deposition and adjusted by a protein efficiency for growth of 58 % were added to the requirement for maintenance of 0.66 g/kg body weight per day. The PRI was estimated based on the average requirement plus 1.96 SD using a combined SD for growth and maintenance. For pregnancy, an intake of 1, 9 and 28 g/d in the first, second and third trimesters, respectively, is proposed in addition to the PRI for non-pregnant women. For lactation, a protein intake of 19 g/d during the first six months, and of 13 g/d after six months, is proposed in addition to the PRI for non-lactating women. Data are insufficient to establish a Tolerable Upper Intake Level (UL) for protein. Intakes up to twice the PRI are regularly consumed from mixed diets by some physically active and healthy adults in Europe and are considered safe. © European Food Safety Authority, 2012 KEY WORDSProtein, amino acids, nitrogen balance, factorial method, efficiency of utilisation, digestibility, health outcomes. SUMMARYFollowing a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver a scientific opinion on Population Reference Intakes for the European population, including protein.Dietary proteins are the source of nitrogen and indispensable amino acids which the body requires for tissue growth and maintenance. The main pathway of amino acid metabolism is protein synthesis. In this opinion, "protein" is total nitrogen x 6.25 and protein requirements are based on nitrogen content. Protein digestion takes place in the stomach and in the small intestine. In healthy humans, the absorption and transport of amino acids is usually not limited by the availability of digestive enzymes or transport mechanisms, but some protein escapes digestion in the small intestine and is degraded in the colon through bacterial proteolysis and amino acid catabolism. By the time digesta are excreted as faeces, they consist largely of microbial protein. Therefore, when assessing protein digestibility, it is important to distinguish ...

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Daily delivery of dietary nitrogen to the periphery is stable in rats adapted to increased protein intake

Cited by 44 publications

References 47 publications

A Central Role for Neuronal AMP-Activated Protein Kinase (AMPK) and Mammalian Target of Rapamycin (mTOR) in High-Protein Diet–Induced Weight Loss

A Central Role for Neuronal AMP-Activated Protein Kinase (AMPK) and Mammalian Target of Rapamycin (mTOR) in High-Protein Diet–Induced Weight Loss

Intestinal lysine metabolism is driven by the enteral availability of dietary lysine in piglets fed a bolus meal

Scientific Opinion on Dietary Reference Values for protein

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