Energy and protein metabolism during recovery from malnutrition due to nonneoplastic gastrointestinal disease.

The magnitude of metabolic adaptation to malnutrition is still debated and few studies have investigated the phase of recovery from malnutrition. The aim of the present work was to determine whether refeeding was associated with adaptive changes in 1) energy expenditure, 2) maximal capacity for oxidizing lipids, and 3) whole-body protein turnover. Eleven malnourished patients with nonneoplastic gastrointestinal diseases were studied by using indirect calorimetry and L-[1-13C]leucine infusion while being infused with lipid-rich total parenteral nutrition (TPN). The same study was performed before initiation of TPN and after a mean gain of 6.5 kg body wt. In absolute values, resting energy expenditure (REE) increased after refeeding (4.05 +/- 0.85 compared with 4.60 +/- 1.05 MJ/d). Change in REE adjusted for fat-free mass (FFM) correlated significantly with change in body weight (r = 0.850, P = 0.01) and change in body fat (r = 0.798, P = 0.01) but not with change in FFM (r = -0.06, NS). Lipid oxidation decreased significantly after body weight gain (0.93 +/- 0.28 compared with 0.50 +/- 0.37 mg.kg-1.min-1). When expressed per kg FFM, protein turnover and breakdown increased significantly during body weight gain. Moreover, the change in protein turnover correlated with the rate of change in FFM, suggesting that FFM accretion requires increased interorgan exchange of amino acids. Our data suggest that in patients similar to those studied here and during recovery from malnutrition, the degree of change in adjusted REE during refeeding is correlated with change in fat mass and not with change in FFM, and that there is a decrease in oxidation of infused lipids. These mechanisms may contribute to body fat repletion and regulation during weight gain.

Isotope ratio mass spectrometric method for the on-line determination of oxygen-18 in organic matter.

A method for the on-line determination of oxygen-18, at a naturally occurring level, in organic material is presented. After pyrolysis of the samples to form carbon monoxide, which is performed at 1300 degrees C in a vitreous carbon tube, the pyrolysis products are transported by a stream of helium gas. Using an open split, a small part of the effluent is transferred to the ion source of an isotope ratio mass spectrometer. The ratio is obtained from a measurement of the ion current intensities at m/z 30 and 28 (12C18O and 12C16O). The method was tested with the secondary water standard GISP (Greenland Ice Sheet Precipitation) and the carbonate standard NBS 19. The values obtained were -24.8/1000 and 27.3/1000 vs. VSMOW (Vienna Standard Mean Ocean Water) (LAEA reference values are -24.8/1000 and 28.7/1000 vs. VSMOW). The potential of the method was demonstrated by measuring the 18O content of samples of beet and cane sucrose and also samples of vanillin extracted from vanilla pods or of synthetic origin.

Energy and protein metabolism in malnutrition due to nonneoplastic gastrointestinal diseases.

Although a reduction in both energy expenditure and protein turnover has been demonstrated in starved volunteers, few metabolic data are available for patients in whom malnutrition is due to nonneoplastic gastrointestinal diseases. Chronically malnourished, unstressed adult patients with nonneoplastic gastrointestinal diseases (body mass index, 15.8 +/- 2.5 kg/m2, n = 13) and healthy control subjects (n = 10) were studied in the postabsorptive state using indirect calorimetry, as well as substrate fluxes of L[1-13C]leucine, L-[2-15N]glutamine (seven patients and six controls), and D[6,6-2H2]glucose (seven patients and eight controls). Resting energy expenditure (REE) expressed in kilocalories per 24 hours was significantly lower in patients than in controls; REE expressed per unit of fat-free mass (FFM) was not significantly different in both groups. Whole-body leucine turnover, oxidation, and nonoxidative disposal rates, based on either 13C-leucine or 13C-alpha-ketoisocaproic acid (KIC) enrichments, and glucose turnover rate were not significantly different between malnourished patients and controls. Moreover, glutamine turnover was increased by 28% in malnourished patients as compared with normal volunteers (429.8 +/- 86.8 v 334.9 +/- 15.9 mumol/kg/h, P = .02). These results suggest that hypometabolic adaptation, although previously documented in starved volunteers, is not operative during states of chronic malnutrition due to gastrointestinal disease. The increase in glutamine turnover rate might represent an adaptative mechanism to malnutrition for preservation of visceral mass or function.

Effect of acute glycerol administration with or without a mixed meal in humans.

We explored the effects of oral glycerol administration (20 g) alone or in combination with a mixed meal on postprandial lipids, free fatty acids, high-density lipoprotein cholesterol and retinyl palmitate. We also tested the meal alone as a control. The metabolic behavior of 13C-labelled glycerol, mainly its incorporation into triglycerides and glucose, was also investigated. The tests were performed on 13 healthy subjects aged 20-56 years (mean 32.1 +/- 10.8). Glycerol administration alone induced a decrease in plasma free fatty acid levels. When glycerol was given with the meal, it was absorbed faster and postprandial triglyceride levels were higher compared to the meal alone (p < 0.05). An earlier and higher peak of retinyl palmitate was also observed when comparing the glycerol and mixed meal test to the mixed meal alone. No significant effect was observed on total, high-density and low-density lipoprotein cholesterol. These results suggest that the glycerol-induced increase in postprandial triglyceride levels is probably due to an increase in chylomicron synthesis and perhaps to the stimulation of intestinal glycerol kinase activity. 13C-labelled glycerol administration showed a more important glycerol incorporation in lipoproteins with a density range of < 1.006 during the test with glycerol alone as compared to the test with glycerol and a mixed meal, suggesting that the rate of glycerol incorporation into lipoproteins depends on the availability of other substrates.

Glutamine metabolism in healthy adult men: response to enteral and intravenous feeding.

To assess the effect of feeding on glutamine kinetics, six healthy men received 4-h intravenous infusions of L-[2-15N]glutamine and L-[1-13C]leucine on 3 separate days: 1) in the postabsorptive state, 2) over the course of an 8-h nasogastric infusion of a small peptide-based nutrient mixture, and 3) during an 8-h isonitrogenous, isoenergetic intravenous infusion (1.5 g amino acid.kg-1.d-1; 130 kJ.kg-1.d-1, or 31 kcal.kg-1.d-1; 58% carbohydrate and 42% fat). Regardless of the route, nutrition increased leucine appearance rate (Ra) and oxidation, stimulated protein synthesis, and improved leucine balance; apparent rates of protein breakdown decreased during enteral nutrition only. Glutamine Ra increased 16.8% (NS) and 26.2% (P < 0.01) with parenteral and enteral feeding, respectively, over postabsorptive values. The present findings are consistent with a major role of glutamine in interorgan nitrogen transport in the fed state and further suggest that increased availability of precursors may stimulate glutamine synthesis de novo, and enteral infusion of peptide-bound amino acids may be an effective route to provide free glutamine to the rest of the body.

Leucine metabolism at graded amino acid intakes in children receiving parenteral nutrition.

To assess the response of protein turnover to graded levels of amino acid (AA) intakes, leucine kinetics were determined in six 8- to 16-yr-old patients in a stable nutritional status receiving home parenteral nutrition (PN) for short-bowel syndrome or intestinal pseudo-obstruction syndrome. Although daily energy intake was kept constant at 68.7 +/- 13 kcal/kg lean body mass (LBM) with 25.4 +/- 3.6% lipid, patients were given, for three consecutive 7-day periods, 0.7, 1.5, or 2.5 g AA.kg LBM-1.day-1, with the order of the regimens being randomized. On day 7 of each period, a 4-h infusion of L-[1-13C]leucine was performed during intravenous feeding; plasma [13C]ketoisocaproate and expired 13CO2 enrichments were used to assess whole body leucine turnover (Ra), oxidation rate (Ox), nonoxidative disposal [an estimate of protein synthesis (S)], and leucine derived from protein breakdown (B). Urine collection (24 h) was performed for determination of nitrogen excretion. Results indicate a dose-dependent rise in plasma leucine concentration, Ra, and Ox but no significant change in B. There was a significant increase of S (P = 0.04 analysis of variance) with increased AA intakes as well as net leucine balance (P = 0.02). Results are consistent with improved leucine balance, when leucine intake increases, despite increased leucine oxidation. The net protein gain observed with higher AA intakes may suggest a beneficial effect for children receiving long-term PN.

The role of type and structure of complex carbohydrates response to physical exercise.

To examine the level of oxidation between different carbohydrate foodstuffs ingested one hour before exercise, three experiments were conducted in men. They performed a series of exercise tests of two hours duration at 60% VO2max preceded in experiment I by ingestion of one of five isocaloric (836 kJ) successive meals of bread, potatoes, rice, spaghetti, or glucose; in experiment II, by either spaghetti or glucose, both naturally 13C enriched; in experiment III, by one of four 13C labelled meals containing starches differing in their proportion of amylose and amylopectin and in their culinary preparation. Results show: 1) The following glucose and insulin response from the highest to the lowest was: glucose > potatoes > bread > rice > spaghetti and after 30 min of exercise a significantly lower blood glucose concentration observed after glucose and potato diets compared to the rice and spaghetti meals. The level of 13CO2 production from the food ingested in experiments II and III was expressed in terms of Atom Percent Excess (APE). Data suggests that spaghetti is oxidized to a lesser degree than glucose. The comparison between starches shows that gelatinized amylopectin is metabolized to the same extent as glucose when there is a progressive decline in the level of oxidation from gelantinized amylose and crude amylopectin to crude amylose.

Glutamine nitrogen kinetics in insulin-dependent diabetic humans.

To assess the effect of insulin deficiency on whole body glutamine kinetics, five young adults with type I (insulin-dependent) diabetes received 4-h primed continuous infusions of L-[1-13C]leucine and L-[2-15N]glutamine in the postabsorptive state after blood glucose had been clamped overnight at either a normoglycemic level (approximately 85 mg/dl) or a moderate hyperglycemic level (approximately 260 mg/dl) by means of an automated glucose control insulin infusion system. The hyperglycemic state was associated with a significant rise in leucine level [from 165 +/- 23 to 242 +/- 62 (SD) microM], appearance rate (from 125 +/- 11 to 142 +/- 17 mumol.kg-1.h-1), and oxidation (from 27 +/- 10 to 31 +/- 10 mumol.kg-1.h-1). In contrast, neither the plasma level nor the appearance rate of glutamine (333 +/- 51 vs. 318 +/- 58 mumol.kg-1.h-1) was affected. We conclude that insulin deficiency resulting in moderate hyperglycemia induces a 13% rise in whole body proteolysis and yet does not stimulate glutamine de novo synthesis, despite increased precursor availability.

Evaluation of (13C)ethanol incorporation into very-low-density lipoprotein triglycerides using gas chromatography/isotope ratio mass spectrometry coupling.

Gas chromatography/isotope ratio mass spectrometry (GC/IRMS) coupling was used to evaluate (13C)ethanol incorporation into plasmatic very-low-density lipoprotein (VLDL) triglycerides of three healthy human volunteers. After the perfusion of 13C-enriched alcohol, VLDL triglyceride fractions were extracted from plasma samples and prepared for the analysis of (13C)fatty acid methyl esters. The GC/IRMS coupling line, the analytical procedure and the data collection are described. The results show that ethanol itself may be used as a substrate for lipogenesis, though to a small extent: less than 10% of VLDL triglycerides may be derived from this metabolic pathway. Ethanol incorporates predominantly into myristic and palmitic acid. The small amount of sample material required for analysis, which minimizes the amount of isotope-labelled substrate required, makes this technique a valuable tool for metabolic investigations in human subjects.

Use of a ventilated canopy for assessment of [13C]leucine oxidation in patients receiving total parenteral nutrition.

Rates of oxidation of infused 13C-labeled substrates are calculated from CO2 production and 13C enrichment in breath CO2. Breath sampling through a mouthpiece is not appropriate in severely ill patients; the authors therefore validated the use of direct air sampling from the ventilated canopy of an indirect calorimeter for measuring the oxidation of 13C-labeled substrates. Infusions of H13CO3Na or L-[1-13C]leucine were performed in four healthy postabsorptive adults and six malnourished patients receiving total parenteral nutrition (TPN). At each sampling point, air was collected from the canopy to compare with breath air sampled through a mouthpiece and 13CO2 enrichment determined by isotope ratio mass spectrometry. Despite five-fold dilution of expired air by room air within the canopy (a dilution required to maintain safe CO2 levels in inspired air): (1) Breath 13CO2 enrichment was accurately predicted using samples from the canopy, with a correction taking into account the measured CO2 fractions in canopy and room air; (2) the precision in isotopic determination was similar with both methods (SD/mean of 12 determinations = 2.5 +/- 1.0% vs 3.0 +/- 1.0%). These data demonstrate that the use of a ventilated canopy allows for combined assessment of energy expenditure and rates of oxidation of 13C-labeled substrates even in sick, debilitated patients receiving total parenteral nutrition.

Oxidation of corn starch, glucose, and fructose ingested before exercise.

The purpose of this study was to compare the metabolic and endocrine responses, and the amounts of exogenous carbohydrate oxidized, during prolonged moderate cycle ergometer exercise (120 min, 60% VO2max), preceded by ingestion of 13C enriched glucose (G), fructose (F), or pure corn starch (S) (1,592 kJ ingested with 400 ml of water, 60 min before the beginning of exercise) in six healthy young male subjects. Plasma glucose and insulin concentrations significantly increased in response to G and S feeding. The high plasma insulin values resulted in a significant transient reduction in plasma glucose concentration in the first hour of exercise and blunted the response of plasma free fatty acid and glycerol concentrations, when compared to the values observed with F ingestion, which did not modify plasma glucose or insulin concentrations. Over the 2 h exercise period, the percentages of exogenous G (67 +/- 9%) and S (73 +/- 8%) oxidized were not significantly different but were significantly higher than the percentage of exogenous F oxidized (54 +/- 6%). These results confirm that 1) exogenous F is less readily available for oxidation than G or S and 2) pure corn starch does not offer any advantage over glucose as a pre-exercise meal.

Whole body glucose kinetics in type I diabetes studied with [6,6-2H] and [U-13C]-glucose and the artificial B-cell.

Dynamic aspects of whole body glucose metabolism were assessed in ten young adult insulin-dependent (type I) diabetic men. Using a primed, continuous intravenous infusion of [6,6-2H]glucose and [U-13C]glucose, endogenous production, tissue uptake, carbon recycling, and oxidation of glucose were measured in the postabsorptive state. These studies were undertaken after blood glucose had been maintained overnight at 5.9 +/- 0.4 mmol/L (n = 10), and on another night at 10.5 +/- 0.4 mmol/L (n = 4) or 15.2 +/- 0.6 mmol/L (n = 6). In the normoglycemic state, endogenous glucose production averaged 2.15 +/- 0.13 mg x kg-1 x min-1. This value, as well as the rate of glucose carbon recycling (0.16 +/- 0.04 mg x kg-1 x min-1) and glucose oxidation (1.52 +/- 0.16 mg x kg-1 x min-1) are comparable to those found in nondiabetic controls. In the hyperglycemic states at 10 or 15 mmol/L, endogenous glucose production was increased by 11% (P less than .01) and 60% (P less than .01) compared to the normoglycemic states, respectively. Glucose carbon recycling contributed only a small percentage to this variation in glucose production (15% at the 15 mmol/L glucose level). This suggests that if gluconeogenesis participates in the increased glucose output, it is not dependent on a greater systemic supply of three-carbon precursors. The increased rate of glucose production in the hyperglycemic state was quantitatively offset by a rise in urinary glucose excretion. Glucose tissue uptake, as well as glucose oxidation, did not vary between normoglycemic and hyperglycemic states.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of 13C-labeled glucose for estimating glucose oxidation: some design considerations.

Use of 13C-labeled glucose for estimating in vivo rates of glucose oxidation faces several difficulties, particularly the accurate determination of the output of 13C in expired air. In an investigation of wholebody glucose metabolism in healthy adult humans, using a continuous intravenous infusion of D-[U-13C]glucose, we found that a precise estimate of the rate of glucose oxidation was difficult to achieve when the study included infusions with unlabeled glucose. Problems arose 1) as a result of the slow rate at which the 13CO2 released by glucose oxidation reaches an equilibrium in expired air CO2 and 2) due to the contribution to 13CO2 output by the natural 13C in the unlabeled glucose that was infused. In a subsequent series of experiments in healthy young adults, we found that the entry of 13CO2 released by the tissues into the bicarbonate pool and into the expired air is relatively slow and a tracer infusion protocol of approximately 6 h is required for determination of glucose oxidation. This applies when metabolic states are changed acutely during the experiment or when unlabeled glucose is infused. However, for resting subjects in the basal postabsorptive state we confirmed that the time required to achieve a steady state in the 13C enrichment of expired air can be shortened significantly by the use of a NaH13CO3 priming dose, even when this dose varies from the ideal.

Whole body de novo amino acid synthesis in type I (insulin-dependent) diabetes studied with stable isotope-labeled leucine, alanine, and glycine.

Dynamic aspects of whole body alanine and glycine metabolism have been explored in insulin-dependent (type I) diabetic subjects. Using a primed, continuous intravenous (i.v.) infusion of [2H3]alanine and [15N]glycine given simultaneously with [1-13C]leucine, whole body alanine and glycine fluxes and their rates of de novo synthesis were measured in 6 diabetic young men. Subjects were studied in the postabsorptive state, after blood glucose was clamped overnight at 15.2 +/- 0.3 mM, and then, on the following night, at 5.9 +/- 0.2 mM (insulin infusion rates of 0.24 +/- 0.09 and 1.65 +/- 0.20 U/h, respectively). In the normoglycemic state, leucine, alanine, and glycine fluxes averaged 88 +/- 4, 378 +/- 39, and 155 +/- 8 mumol X kg-1 X h-1, respectively. Based on the leucine flux, alanine and glycine de novo synthesis rates were 264 +/- 36 and 67 +/- 8 mumol X kg-1 X h-1. In the hyperglycemic state, leucine flux increased 23% (P less than 0.01), alanine flux rose slightly (+5%) but significantly (P less than 0.05), while alanine de novo synthesis and glycine flux remained unchanged and glycine de novo synthesis decreased by 33% (P less than 0.001). These results show that small alterations in peripheral alanine inflow in the hyperglycemic state reflect increased proteolysis and suggest that increased circulating plasma glucose does not contribute to de novo alanine synthesis in the absence of adequate insulin effect and/or augmented glucose tissue uptake. These observations also reveal the importance of insulin in the maintenance of whole body leucine economy, since a lower rate of insulin administration was associated with an increased rate of leucine oxidation.

[Determination of the percentage of grain whisky in commercial whiskies by isotopic mass spectrometry]. / Détermination du pourcentage de whisky de grain dans les whiskies commerciaux par spectrométrie de masse isitopique.

Commercial whisky is generally a blend between malt whisky and grain whisky. Corn is one of the main sources of grain and it is now well known that in corn the carbon dioxide assimilation proceeds through carboxylation of phosphoenolpyruvate but in many other plants like barley atmospheric carbon dioxide is fixed on ribulose 1,5 diphosphate. Each pathway of carbon dioxide assimilation is characterized by a fractionation factor of carbon isotopes. Consequently, the organic matter and also the fermentation alcohol of corn or barley show different 13C/12C ratio. The determination of the 13C/12C ratio in the alcohol of blended whisky allows the determination of the percentage of corn whisky.

[New analytic criteria for the characterization of wines]. / Recherche de nouveaux critères analytiques de caractérisation des vins.

Isotopic analysis, determination of radioactivity are factors allowing a better characterization of wines. The analysis of the composition in stable isotopes of the constituants of wine can provide new analytic criteria for characterizing wines. Thus, the concentration of 13C in ethanol can allow the disclosure of an addition of cane sugar or maize sugar to the musts. A study of the composition in stable isotopes of the water of wines of a certain region made it possible to show a correlation between the amount of D and 18O in the water of wine, and the alcohlic concentration. The setting up of the curve showing the decrease of the radioactivity of 14C in the Girondewines allows a determination of the date, accurate to within one year, of these wines. The enzymatic determination of the gluconic acid present in the wines produced from crops attacked by Botrytis Cinerea allows one to estimate the type of rottenness of the grape; the gluconic acid, which is only present in very small quantities in wines produced from sound grapes, represents about 50 p. 100 of the fixed acides of the grapes affected by "noble rottenness" and up to 90 p. 100 in the case of adultarated grapes. Thanks to the recults obtained in 1976, standards are proposed to allow the characterization of the wines produced from grapes affected by "noble rottenness", so that they can be distinguished from, on the one hand, the wines produced from sound grapes, and on the other hand, the wines produced from adultarated grapes.

[Use of ethanol naturally enriched in carbon 13 for metabolic studies]. / Utilisation d'éthanol naturellement enrichi en carbone 13 pour des études métaboliques

The ratio of carbon 13 to carbon 12 is higher in organic substances which originate from corn or cane, as compared to most higher plants. Cane alcohol or corn alcohol are enriched in carbon 13 as compared to common European foods. This discovery provided a new technique for alcohol metabolism studies with animals or men. The ratio of carbon 13 to carbon 12 is measured by mass spectrometry in the carbon dioxide expired after administration of cane or corn alcohol. This ratio increases significantly and reaches a maximum when the blood alcohol level has decreased considerably.