Production of Elemental Nitrogen by Certain Mammals including Man

Costa, Giovanni; Ullrich, L; Kantor, Ferenc; Holland, James F.

doi:10.1038/218546a0

Cited by 65 publications

(32 citation statements)

References 12 publications

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“…Their estimates for N 2 elimination rates have been confirmed by a recent study [14]. Other studies have suggested nonzero N 2 balance in a variety of clinical and metabolic states [15][16][17][18]. Wilmore found that this did not significantly influence measurement of _ V O 2 during exercise, primarily due to the high levels of _ V O 2 achieved [19].…”

Section: Discussionsupporting

confidence: 68%

Measured pulmonary oxygen consumption: difference between systemic oxygen uptake measured by the reverse Fick method and indirect calorimetry in cardiac surgery

Peyton

Robinson

2005

Anaesthesia

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SummaryMeasurement of oxygen uptake by indirect calorimetry was compared with the reverse Fick method in a series of patients undergoing cardiac surgery. Oxygen uptake measurements for indirect calorimetry were made using a calibrated measurement system utilizing the Haldane transformation in a simple semiclosed breathing system based upon a modified Bain circuit. Pulmonary blood flow for the reverse Fick method was measured using bolus thermodilution. The results were (mean [standard deviation]): indirect calorimetry 167[26] ml.min

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Section: Discussionsupporting

confidence: 68%

Measured pulmonary oxygen consumption: difference between systemic oxygen uptake measured by the reverse Fick method and indirect calorimetry in cardiac surgery

Peyton

Robinson

2005

Anaesthesia

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“…Amino acids tend to be preserved in spite of excess energy availability (46) , but in any case, the excess N is eventually lost, albeit not in the canonical way of urea formation (47) . A small but significant proportion of N is excreted as N 2 gas (48,49) by means of, so far, unknown pathways. In addition there is an increased (but relatively small) loss of dietary amino-N in the form of urinary nitrate and nitrite (50) .…”

Section: Amino Acids As Energy Substrates: Amino-nitrogen Sparingmentioning

confidence: 99%

The problem of nitrogen disposal in the obese

Alemany

2012

Nutr. Res. Rev.

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Amino-N is preserved because of the scarcity and nutritional importance of protein. Excretion requires its conversion to ammonia, later incorporated into urea. Under conditions of excess dietary energy, the body cannot easily dispose of the excess amino-N against the evolutively adapted schemes that prevent its wastage; thus ammonia and glutamine formation (and urea excretion) are decreased. High lipid (and energy) availability limits the utilisation of glucose, and high glucose spares the production of ammonium from amino acids, limiting the synthesis of glutamine and its utilisation by the intestine and kidney. The amino acid composition of the diet affects the production of ammonium depending on its composition and the individual amino acid catabolic pathways. Surplus amino acids enhance protein synthesis and growth, and the synthesis of non-protein-N-containing compounds. But these outlets are not enough; consequently, less-conventional mechanisms are activated, such as increased synthesis of NO z followed by higher nitrite (and nitrate) excretion and changes in the microbiota. There is also a significant production of N 2 gas, through unknown mechanisms. Health consequences of amino-N surplus are difficult to fathom because of the sparse data available, but it can be speculated that the effects may be negative, largely because the fundamental N homeostasis is stretched out of normalcy, forcing the N removal through pathways unprepared for that task. The unreliable results of hyperproteic diets, and part of the dysregulation found in the metabolic syndrome may be an unwanted consequence of this N disposal conflict.

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“…An immediate consequence of the increased uptake was a widespread increase in plasma levels of amino acids. On the other hand, the magnitude of non-accounted N seems not be dependent of dietary protein, as previously described [15], remaining to be elucidated the metabolic fate of this N [24].…”

Section: Discussionmentioning

confidence: 52%

Nitrogen Metabolism in Zucker Rats is Affected by Moderate Reduction, but not by Moderate Increase in Dietary Protein

Rafecas¹

2012

TOOBESJ

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Marked changes in the content of protein in the diet affects the rat's pattern of growth, but there is not any data on the effects to moderate changes. Here we used a genetically obese rat strain (Zucker) to examine the metabolic modifications induced to moderate changes in the content of protein of diets, doubling (high-protein (HP): 30%) or halving (low-protein (LP): 8%) the content of protein of reference diet (RD: 16%). Nitrogen, energy balances, and amino acid levels were determined in lean (L) and obese (O) animals after 30 days on each diet. Lean HP (LHP) animals showed higher energy efficiency and amino acid catabolism but maintained similar amino acid accrual rates to the lean RD (LRD) group. Conversely, the lean LP (LLP) group showed a lower growth rate, which was compensated by a relative increase in fat mass. Furthermore, these animals showed greater efficiency accruing amino acids. Obesity increased amino acid catabolism as a result of massive amino acid intake; however, obese rats maintained protein accretion rates, which, in the OHP group, implied a normalization of energy efficiency. Nonetheless, the obese OLP group showed the same protein accretion pattern as in lean animals (LLP). In the base of our data, concluded that the Zucker rats accommodate their metabolism to support moderates increases in the content of protein in the diet, but do not adjust in the same way to a 50% decrease in content of protein, as shown by an index of growth reduced, both in lean and obese rats.

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Production of Elemental Nitrogen by Certain Mammals including Man

Cited by 65 publications

References 12 publications

Measured pulmonary oxygen consumption: difference between systemic oxygen uptake measured by the reverse Fick method and indirect calorimetry in cardiac surgery

Measured pulmonary oxygen consumption: difference between systemic oxygen uptake measured by the reverse Fick method and indirect calorimetry in cardiac surgery

The problem of nitrogen disposal in the obese

Nitrogen Metabolism in Zucker Rats is Affected by Moderate Reduction, but not by Moderate Increase in Dietary Protein

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