scholarly journals Calculation of substrate oxidation rates in vivo from gaseous exchange

1983 ◽  
Vol 55 (2) ◽  
pp. 628-634 ◽  
Author(s):  
K. N. Frayn
Keyword(s):  
Ketone Bodies ◽  
Fat Oxidation ◽  
Nitrogen Excretion ◽  
Co2 Production ◽  
Gaseous Exchange ◽  
Oxidation Rates ◽  
The Difference ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen

This paper reviews the assumptions involved in calculating rates of carbohydrate and fat oxidation from measurements of O2 consumption, CO2 production, and urinary nitrogen excretion. It is shown that erroneous results are obtained in the presence of metabolic processes such as lipogenesis and gluconeogenesis. The apparent rates calculated under these conditions can, however, be interpreted as net rates of “utilization.” Thus the apparent rate of carbohydrate oxidation is the sum of the rates of utilization for oxidation and for lipogenesis minus the rate at which carbohydrate is formed from amino acids. The apparent rate of fat oxidation is the difference between the rates of oxidation and synthesis from carbohydrate, so that the apparently negative rates encountered in patients infused with glucose do quantitatively represent net rates of synthesis. Other processes such as synthesis of ketone bodies or lactate at rates greater than their utilization can also disturb the calculations, but the magnitude of the effect can be estimated from appropriate measurements. Methods of correcting the observed gaseous exchange in these circumstances are given.

Comparison of indirect calorimetry and a new breath 13C/12C ratio method during strenuous exercise

1992 ◽  
Vol 263 (1) ◽  
pp. E64-E71 ◽  
Author(s):  
J. A. Romijn ◽  
E. F. Coyle ◽  
J. Hibbert ◽  
R. R. Wolfe
Keyword(s):  
Indirect Calorimetry ◽  
Fat Oxidation ◽  
Substrate Oxidation ◽  
Co2 Production ◽  
Strenuous Exercise ◽  
Ratio Method ◽  
O2 Uptake ◽  
Underlying Assumption ◽  
Oxidation Rates

A new stable isotope method for the determination of substrate oxidation rates in vivo is described and compared with indirect calorimetry at rest and during high-intensity exercise (30 min at 80-85% maximal O2 uptake capacity) in six well-trained cyclists. This method uses the absolute ratios of 13C/12C in expired air, endogenous glucose, fat, and protein in addition to O2 consumption and is independent of CO2 production (VCO2). Carbohydrate and fat oxidation rates at rest, calculated by both methods, were not significantly different. During exercise the breath 13C/12C ratio increased and reached a steady state after 15-20 min. Carbohydrate oxidation rates during exercise were 39.4 +/- 5.2 and 41.7 +/- 5.7 mg.kg-1.min-1 [not significant (NS)], and fat oxidation rates were 7.3 +/- 1.3 and 6.9 +/- 1.2 mg.kg-1.min-1 (NS), using indirect calorimetry, and the breath ratio method, respectively. We conclude that the breath 13C/12C ratio method can be used to calculate substrate oxidation under different conditions, such as the basal state and exercise. In addition, the results obtained by this new method support the validity of the underlying assumption that indirect calorimetry regards VCO2 as a reflection of tissue CO2 production, during exercise in trained subjects, even up to 80-85% maximal O2 uptake.

scholarly journals EFFECTS OF BACTERIAL ENDOTOXINS ON METABOLISM

1962 ◽  
Vol 116 (6) ◽  
pp. 897-911 ◽  
Author(s):  
L. Joe Berry ◽  
Dorothy S. Smythe ◽  
Susannah McC. Kolbye
Keyword(s):  
Nitrogen Excretion ◽  
Protein Nitrogen ◽  
Bacterial Endotoxins ◽  
Small Change ◽  
The Moment ◽  
Lower Ratio ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen

The greater susceptibility to the lethal effects of bacterial endotoxin (heat-killed Salmonella typhimurium or Escherichia coli lipopolysaccharide, in mice infected with an attenuated strain of Mycobacterium tuberculosis (BCG) was confirmed. It reached a maximum at 2 weeks postinfection and gradually diminished for an additional 6 weeks. At the time of maximum susceptibility several metabolic and physiological differences became apparent. BCG-infected mice die sooner (4 to 12 hours) and without the diarrhea, conjunctivitis, and general symptomatology associated with endotoxin deaths of normal animals. Reticuloendothelial blockade results in only a small change in reactivity to endotoxin, in contrast to normal mice. Subcutaneous injection of 2 units of ACTH is followed by no significant increase in urinary nitrogen excretion while in control animals it more than doubles. Plasma clearance of intravenously administered inulin is approximately normal in BCG-infected mice 17 hours after an LD50 dose of endotoxin but control mice similarly treated show renal impairment. In line with this result is the absence of elevated carcass non-protein nitrogen (NPN) following endotoxin poisoning or at the moment of death from endotoxemia in the hyperreactive animals in contrast to the two- to threefold increase in carcass NPN in normal mice under similar conditions. Body carbohydrate is at a minimum and becomes depleted to a level approximating that found at death more rapidly in BCG-infected mice given endotoxin than in controls. There is also a lower ratio of carbohydrate anabolized to protein catabolized following cortisone administration to BCG-infected mice than in control mice. This is found in adrenalectomized mice and in stressed animals and is reported elsewhere. Some of the differences just described can be attributed to a refractory adrenal cortex. There is less depletion of adrenal cholesterol in vivo and lower corticoid synthesis in vitro than in normal mice yet this is not fundamentally responsible for the greater susceptibility of BCG-infected animals to endotoxin since adrenalectomized mice, which are even more susceptible, are metabolically and physiologically more comparable to normal mice than to BCG-infected mice. One can conclude, therefore, that the hyperreactivity of BCG-infected mice is more than an intensification of the normal response to endotoxin.

Hyperglucagonemia during insulin deficiency accelerates protein catabolism

1987 ◽  
Vol 253 (2) ◽  
pp. E208-E213 ◽  
Author(s):  
K. S. Nair ◽  
D. Halliday ◽  
D. E. Matthews ◽  
S. L. Welle
Keyword(s):  
Protein Metabolism ◽  
Nitrogen Excretion ◽  
Insulin Deficiency ◽  
Leucine Oxidation ◽  
Precise Role ◽  
Combined Deficiency ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen

Hyperglucagonemia coexists with insulin deficiency or insulin resistance in many conditions where urinary nitrogen excretion is increased, but the precise role of glucagon in these conditions is controversial. The purpose of this study was to evaluate the effect of hyperglucagonemia on protein metabolism in insulin-deficient subjects. We used the stable isotope of an essential amino acid (L-[1-13C]leucine) as a tracer of in vivo protein metabolism. A combined deficiency of insulin and glucagon was induced by intravenous infusion of somatostatin. Hyperglucagonemia and hypoinsulinemia were induced by infusions of somatostatin and glucagon. When somatostatin alone was infused leucine flux increased, indicating a 6-17% increase in proteolysis. When somatostatin and glucagon were infused, leucine flux increased, indicating a 12-32% increase in proteolysis. The increase in leucine flux during the infusion of somatostatin and glucagon was higher than the increase during infusion of somatostatin alone. Somatostatin alone did not change leucine oxidation, whereas the somatostatin plus glucagon increased leucine oxidation 100%. We conclude that hyperglucagonemia accelerates proteolysis and leucine oxidation in insulin-deficient humans.

scholarly journals Feasibility of achieving different protein targets using a hypocaloric high-protein enteral formula in critically ill patients

Critical Care ◽  
2021 ◽  
Vol 25 (1) ◽  
Author(s):  
Pierre Singer ◽  
Itai Bendavid ◽  
Ilana BenArie ◽  
Liran Stadlander ◽  
Ilya Kagan
Keyword(s):  
Critically Ill ◽  
Nitrogen Balance ◽  
High Protein ◽  
Nitrogen Excretion ◽  
Protein Targets ◽  
Protein Target ◽  
Group A ◽  
Group B ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen

Abstract Background and aims Combining energy and protein targets during the acute phase of critical illness is challenging. Energy should be provided progressively to reach targets while avoiding overfeeding and ensuring sufficient protein provision. This prospective observational study evaluated the feasibility of achieving protein targets guided by 24-h urinary nitrogen excretion while avoiding overfeeding when administering a high protein-to-energy ratio enteral nutrition (EN) formula. Methods Critically ill adult mechanically ventilated patients with an APACHE II score > 15, SOFA > 4 and without gastrointestinal dysfunction received EN with hypocaloric content for 7 days. Protein need was determined by 24-h urinary nitrogen excretion, up to 1.2 g/kg (Group A, N = 10) or up to 1.5 g/kg (Group B, N = 22). Variables assessed included nitrogen intake, excretion, balance; resting energy expenditure (REE); phase angle (PhA); gastrointestinal tolerance of EN. Results Demographic characteristics of groups were similar. Protein target was achieved using urinary nitrogen excretion measurements. Nitrogen balance worsened in Group A but improved in Group B. Daily protein and calorie intake and balance were significantly increased in Group B compared to Group A. REE was correlated to PhA measurements. Gastric tolerance of EN was good. Conclusions Achieving the protein target using urinary nitrogen loss up to 1.5 g/kg/day was feasible in this hypercatabolic population. Reaching a higher protein and calorie target did not induce higher nitrogen excretion and was associated with improved nitrogen balance and a better energy intake without overfeeding. PhA appears to be related to REE and may reflect metabolism level, suggestive of a new phenotype for nutritional status. Trial registration 0795-18-RMC.

Effect of starch on the utilization by sheep of a straw diet supplemented with urea and minerals

1976 ◽  
Vol 27 (1) ◽  
pp. 139 ◽  
Author(s):  
JG Mulholland ◽  
JB Coombe ◽  
WR McManus
Keyword(s):  
Organic Matter ◽  
Nitrogen Retention ◽  
Nitrogen Excretion ◽  
Digestible Organic Matter ◽  
Cellulose Digestibility ◽  
Oat Straw ◽  
Total Body ◽  
Body Energy ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen

Individually penned Border Leicester x Merino wethers, aged 11 months, were fed ad lib. for 16 weeks on a basal ration of ground, pelleted oat straw, urea and minerals, supplemented with 0, 5, 10, 15, 20, 30 or 40% starch. The diets contained equal percentages of nitrogen and minerals. Dry matter intake reached a maximum of 2000 g/day with 30% starch; above this starch level, digestive disturbances were observed. Organic matter digestibility was increased by the addition of starch, but cellulose digestibility was depressed by as much as 18 units with the addition of 30% starch. Up to 10% the starch level had little effect on cellulose digestibility. Liveweight change was significantly correlated with digestible organic matter intake, mean daily weight gains varying from 22 g with no starch to 104 g with 30% starch. However, a large percentage of the liveweight gain was as total body water, and body energy storage increased appreciably only when the diet contained at least 20% starch. The inclusion of 5% starch slightly depressed both intake and liveweight gain. Daily clean wool production was significantly increased at starch levels higher than 20% and ranged from 5.3 to 7.5 g/day with 0 and 40% starch respectively. Increasing levels of starch had little effect on apparent nitrogen digestibility, but resulted in a substantial increase in nitrogen retention through a reduction in urinary nitrogen excretion. Serum urea levels fell from a mean of 42 mg/100 ml during the first week to 31 mg/100 ml during subsequent periods, with no significant differences between diets. With the general exception of potassium, mineral balances were positive or close to zero throughout the experiment.

Branched-Chain Amino Acids, Nitrogen Excretion and Injury in Man

1976 ◽  
Vol 50 (5) ◽  
pp. 393-399 ◽  
Author(s):  
J. H. Wedge ◽  
R. De Campos ◽  
A. Kerr ◽  
R. Smith ◽  
Rose Farrell ◽  
...  
Keyword(s):  
Amino Acids ◽  
Venous Blood ◽  
Branched Chain Amino Acids ◽  
Nitrogen Excretion ◽  
Adult Males ◽  
Blood Concentrations ◽  
Branched Chain ◽  
Injured Patients ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen

1. Venous blood concentrations of the branched-chain amino acids, valine, leucine and isoleucine, and urinary nitrogen excretion have been measured in sixteen adult males, from 2 h to 7 days after injury, and in four adults after elective skin grafts. 2. In the injured group the concentrations of these amino acids rose significantly 24 h after injury and had doubled at 4 days and remained high; in contrast the skin-graft patients showed no significant change. 3. In those injured patients with initial hyperketonaemia, defined as more than 0·2 mmol/l, the increase in concentrations of branched-chain amino acids at the fourth and seventh days after injury was significantly less than in those with normoketonaemia, and was accompanied by lower urinary nitrogen excretion throughout the whole period. 4. It is suggested that the changes in the concentration of branched-chain amino acids after injury indicate decreased uptake by muscle or excessive release due to an imbalance between protein synthesis and protein catabolism in this tissue.

Urinary nitrogen excretion at the early stage of severe acute pancreatitis

2020 ◽  
Vol 21 (4) ◽  
pp. 131-134
Author(s):  
O. G. Sivkov ◽  
◽  
A. O. Sivkov ◽  
Keyword(s):  
Acute Pancreatitis ◽  
Severe Acute Pancreatitis ◽  
Early Stage ◽  
Ideal Body Weight ◽  
Nitrogen Excretion ◽  
The Third ◽  
Ideal Body ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen ◽  
The Ideal

Aim. To study urinary nitrogen excretion at the early stage of severe acute pancreatitis. Materials and methods. Prospective, single-center, cohort study. Inclusion criteria: diagnosis of acute pancreatitis and presence of at least one of the predictors of severe course. Among all patients (n = 72), a cohort of patients with severe acute pancreatitis (n = 32) was allocated. Three groups were formed in it: the first one – all patients, the second one – survivors (n = 24), the third one – deceased (n = 8). Urinary nitrogen excretion was determined using the Deacon formula. Measurements were performed on the first, third and fifth days of the disease. Statistical processing of the material was carried out by the SPSS software package. The null hypothesis was rejected at p < 0.05. Results. In the first week of the disease in all groups, the maximum urinary nitrogen excretion occurs on the 3rd day. When comparing the results of the second and third groups, it was found that the urinary nitrogen excretion on the first and fifth days did not have a statistically significant difference between the groups (respectively, p = 0.138, p = 0.572), and the results of the third day have (p = 0.014). A similar pattern remains when recalculating the nitrogen loss in the urine to the ideal weight; for the third day, the differences between the second and third groups were statistically significant (p = 0.007). ROC analysis of urinary nitrogen excretion of the third day calculated to the ideal body weight showed an area under the curve of 0.813 (p < 0.009). The value at the cut-off point is defined as 0.65 g/kg/day. The sensitivity of the model was 0.75%, specificity – 0.83%. Conclusion. If in a patient with acute pancreatitis, there is urinary nitrogen excretion on the third day from the onset of the disease, calculated to an ideal body weight of ≥ 0.65 g/kg/day, an unfavorable outcome of the disease is predicted.

The effect of ERDP:FME ratio and DUP supply from concentrates on the performance of lactating ewes offered grazed grass

1996 ◽  
Vol 1996 ◽  
pp. 160-160
Author(s):  
R.G. Wilkinson ◽  
L.A. Sinclair ◽  
J. Powles ◽  
C.M. Minter
Keyword(s):  
Crude Protein ◽  
Microbial Growth ◽  
High Rate ◽  
Nitrogen Excretion ◽  
Crude Protein Content ◽  
Nitrogen Utilisation ◽  
Metabolisable Energy ◽  
Urinary Nitrogen Excretion ◽  
Urinary Nitrogen ◽  
Degradable Protein

Fresh grass is a highly variable product, which is generally characterised as having a high crude protein content, with a high rate and extent of degradation in the rumen. For lactating ruminants, this may result in an effective rumen degradable protein: fermentable metabolisable energy (ERDP:FME) ratio in excess of the optimum requirement for microbial growth, leading to inefficient nitrogen utilisation and high levels of urinary nitrogen excretion. One method of improving the efficiency of nitrogen utilisation is the use of supplements. An appropriate supplement should optimise ERDP and FME supply to the rumen and provide sufficient metabolisable protein (MP) to balance animal requirements. The objective of the experiment was to investigate the response of lactating ewes offered grazed grass to variations in ERDP:FME ratio and digestible undegradable protein (DUP) supply from concentrate supplements.

Sign in / Sign up

Export Citation Format

Share Document