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PubMed1998

Improved viability and metabolic behavior of hepatocytes after liver storage in the presence of a succinic acid ester.

BACKGROUND: Selected esters of succinic acid were recently proposed as novel nutrients to support ATP generation in cells endangered by an imbalance between the formation and breakdown of this adenine nucleotide. In the present study, a new ester, glycerol-1,2,3-trimethylsuccinate, was examined for its potential beneficial effect in the procedures preceding liver transplantation. METHODS: The viability and metabolic behavior of hepatocytes were examined after perfusion and storage of rat livers for 20 hr at 4 degrees C with a Belzer UW-CSS solution in the absence or presence or 2 mM glycerol-1,2,3-trimethylsuccinate. RESULTS: Although it failed to affect significantly the release of cellular enzymes during storage and the protein or glycogen content of the liver, and was unable to prevent the storage-induced decrease in both biosynthetic activity and D-[U-14C]glucose incorporation into glycogen in isolated hepatocytes, the ester restored to a close-to-normal value the viability of the hepatocytes and opposed the starvation-like effects of liver storage upon both the conversion of D-[U-14C]glucose to 14CO2 and radioactive amino acids and the de novo generation of 14C-labeled D-glucose from [2-14C]pyruvate. CONCLUSIONS: Because succinic acid esters are efficiently metabolized in several cell types, the present results suggest that such esters may have a wide field of application in transplantation procedures.

Animals↗
PubMedDate not supplied

[Effect of food carbohydrate quality on monosaccharide utilization for the biosynthesis of glycogen, fat and proteins in the rat liver].

The inclusion of 3H-6-glucose and 14C-fructose metabolites into the rat liver glycogen, lipids and protein was studied in male rats receiving the rations containing 56% of carbohydrates, 18% protein, 26% fat, necessary amount of mineral substances and vitamins, during 25 days. Animals given the ration with starch, as a carbohydrate, were used as controls. In the ration of animals in groups 2, 3 and 4 some portion of starch (30% calorific value) was substituted for glucose, sucrose of the mixture of glucose and fructose (1:1). It was found that in the liver of animals given pure starch, radioactivity from 3H-6-glucose was included mainly into proteins, when starch was partly substituted for monosaccharide--mainly into lipids. These regularities were recorded in the distribution of radioactivity from 14C-fructose, all the parameters being shifted in the direction of increased inclusion of radioactivity into lipids. Partial substitution of starch for sucrose specifically changed the radioactivity distribution between proteins and lipids, thus revealing a distinct "disaccharide" effect.

Animals↗
PubMed1982

Further evidence for the classical pentose phosphate cycle in the liver.

Isolated rat hepatocytes were incubated with [3-(14)C]xylitol or d-[3-(14)C]xylulose plus xylitol or glucose at substrate concentrations. The glucose formed was isolated and degraded to give the relative specific radioactivities in each carbon atom. C-4 of glucose had the highest specific radioactivity, followed by C-3, with half to one-fifth that of C-4. Only about 1% of the total radioactivity was in C-1. The data are compared with the predictions of the classical pentose phosphate cycle [Horecker, Gibbs, Klenow & Smyrniotis (1954) J. Biol. Chem.207, 393-403], and the proposed new version of the pentose phosphate cycle in liver [Longenecker & Williams (1980) Biochem. J.188, 847-857], which they denoted as the ;L-type pentose cycle'. The Williams pathway predicts that the specific radioactivity of C-1 of glucose should be half that of C-4 (after correction for approximately equal labelling on C-3 and C-4 of hexose phosphate in the pathway involving fructose 1,6-bisphosphatase). The actual labelling in C-1 is 20-350-fold less than this. When the hepatocytes are incubated with phenazine methosulphate, to stimulate the oxidative branch of the pentose phosphate cycle, the predicted relationship between (C-2/C-3) and (C-1/C-3) ratios of specific radio-activities is nearly exactly in accord with the classical pentose phosphate cycle. Glucose and glucose 6-phosphate were isolated and degraded from an incubation of hepatocytes from starved/re-fed rats with [3-(14)C]xylitol. Although the patterns were of the classical type, there was more randomization of (14)C into C-2 and C-1 in the glucose 6-phosphate isolated at the end of the incubation than in the glucose which was continuously produced.

Animals↗
PubMed1981

The determination of lactate turnover in vivo with 3H- and 14C-labelled lactate. The significance of sites of tracer administration and sampling.

L-[3-3H,U-14C]Lactate was administered to starved rats either as a bolus or by continuous infusion. Tracer administration was performed two ways: injection into the vena cava and sampling from the aorta (V-A mode), or injection into the aorta and sampling from the vena cava (A-VC mode). The specific-radioactivity curves after infusion or injection differed markedly with the two procedures. However, the specific radioactivities of 14C-labelled glucose derived from [U-14C]lactate were similar in the two modes. The apparent turnover rates of lactate calculated from the 3H specific-radioactivity curves in the V-A mode were about half those obtained from the 3H specific-radioactivity curves in the A-VC mode. The apparent contribution of lactate carbon to glucose carbon calculated from specific-radioactivity curves of the A-VC mode was greater than that obtained from the V-A mode. The apparent recycling of lactate carbon calculated from the specific radioactivities for [U-14C]- and [3-3H]-lactate was greater in the A-VC mode than the V-A mode. [U-14C] Glucose was administered in the two modes, but in contrast with lactate the specific radioactivities were only slightly different. An analysis to account for these observations is presented. It is shown that the two modes represent sampling from different pools of lactate. The significance of sites of tracer administration and sampling for the interpretation of tracer kinetics of compounds present in intracellular and extracellular spaces, and with a high turnover rate, is discussed. We propose that for such compounds, including lactate, alanine and glycerol, the widely used V-A mode leads to a marked underestimate of replacement, mass and carbon recycling, and that the A-VC mode is the preferred method for the assessment of these parameters.

Animals↗
PubMed1993

Effects of xylitol on carbohydrate and protein metabolism after trauma and during sepsis.

INTRODUCTION: Total parenteral nutrition (TPN) after trauma and during sepsis has two major goals. One is the reduction of increased protein catabolism, the second is to avoid hyperglycemia and enhanced hepatic gluconeogenesis. Glucose and xylitol differ in their utilization rates after trauma and during sepsis. Whole-body glucose utilization is reduced during such states, while the utilization of xylitol is more than doubled. In order to investigate whether these differences are associated with beneficial effects on hepatic glucose production and protein sparing, we conducted two animal and two clinical studies. METHODS: For the analysis of glucose and protein turnover radioactive and stable isotope techniques were applied. In burned rats primed constant infusions of 6-[3H]-glucose, 1-[14C]-alanine, 3-[14C]-alanine and U-[14C]-acetate were used to determine whole body glucose turnover, gluconeogenesis from C3-precursors and alanine flux. In septic rats nitrogen balance was calculated after determination of 24-hour-urine nitrogen content measured by micro-Kjeldahl digestion. 24-hour urinary 3-methyl-histidine excretion was analysed by amino acid autoanalyser. In human studies hepatic glucose production and urea synthesis rates were measured using primed continuous infusions of [6,6-d2]-glucose and [2-N15]-urea, respectively. RESULTS: In the first trauma model we demonstrated that hypocaloric xylitol in contrast to glucose significantly reduced hepatic glucose production and gluconeogenesis from C3-carbons. In the septic rat exchange of glucose calories by xylitol in a proportion of 1:1 was associated with a significantly ameliorated nitrogen retention and lower 3-methyl-histidine excretion. In two studies on surgical intensive care patients we were able to confirm these nitrogen sparing properties of xylitol. Hepatic glucose production and urea synthesis rates were significantly reduced during xylitol infusion after trauma, whereas equicaloric glucose had no effects. In septic patients xylitol led to significant lower lactate concentrations and gluconeogenesis rates than isocaloric glucose. DISCUSSION: In animal as well as in human studies hypocaloric xylitol and the mixture of glucose/xylitol (1:1) were more efficient in preserving body protein than glucose alone. Hepatic gluconeogenesis was significantly reduced when compared to isocaloric glucose. During the acute phase after trauma we therefore recommend a carbohydrate supplementation of 3 g/kg BW/d by xylitol. During long-term TPN a glucose/xylitol mixture (1:1) in a dosage of 6 g/kg BW/d is recommended together with amino acids and, if necessary, lipids.

Animals↗
PubMed1987

Pyridine nucleotide analog interference with metabolic processes in mitogen-stimulated human T lymphocytes.

The differential metabolic effects of three nicotinamide analogs, 6-aminonicotinamide, 3-aminobenzamide, and 5-methylnicotinamide, were analyzed in mitogen-stimulated preparations of human T lymphocytes. Mitogen stimulation with the phorbol ester TPA and a monoclonal antibody to the T3 cell surface antigen caused an increase in cellular NAD and ATP levels and a marked increase in glucose metabolism as demonstrated by an increase in cellular levels of glucose 6-phosphate and a sevenfold increase in radioactive CO2 formation from [l-14C]glucose. 6-Aminonicotinamide had drastic inhibitory effects on the mitogen-stimulated increases in NAD and ATP levels as well as on the metabolism of glucose. Treatment of the mitogen-stimulated cells with 6-aminonicotinamide also caused a marked increase in cellular levels of 6-phosphogluconate, suggesting inhibition of the hexose monophosphate shunt at 6-phosphogluconate dehydrogenase. Radioactive CO2 formation from [6-14C]glucose showed that metabolism through the tricarboxylic acid cycle was not used to compensate for the inhibition of the hexose monophosphate shunt pathway. Treatment of cells with 3-aminobenzamide had the opposite effect of 6-aminonicotinamide in that cellular NAD levels increased, presumable due to inhibition of poly(ADP-ribose) polymerase. 3-Aminobenzamide did not interfere with ATP or glucose 6-phosphate levels and did not cause significant elevations of 6-phosphogluconate. Thus, 6-aminonicotinamide appears to have direct inhibitory effects on the synthesis of both pyridine nucleotides and poly(ADP-ribose), whereas 3-aminobenzamide has its major inhibitory effect on poly(ADP-ribose) synthesis. 5-Methylnicotinamide also interferes with the mitogen-stimulated increase in NAD levels but not as effectively as 6-aminonicotinamide. The alterations in pyridine nucleotide metabolism resulting from treatment with these nicotinamide analogs can produce drastic and diverse alterations in pathways of glucose utilization and energy generation.

6-Aminonicotinamide↗
PubMed1982

Effect of cholesterol on the reconstituted D-glucose transport system of human erythrocyte membranes.

Human erythrocyte membranes were solubilized by cholate. Reconstitution into phospholipid liposomes containing different amounts of cholesterol was performed by chromatographic removal of cholate. Glucose transport was determined as the differential uptake of radioactive D- and L-glucose. The reconstituted glucose transport activity decreased with increasing concentration of cholesterol up to about 20 mole percent. Further increase in cholesterol concentration resulted in an increase in the glucose transport activity.

Blood Glucose↗
PubMed1973

Effect of halofenate and clofibrate on growth and lipid synthesis in Saccharomyces cerevisiae.

Halofenate-free acid (HFA) inhibited the growth of Saccharomyces cerevisiae by 50% at a concentration of 0.34 mm. This inhibitory effect was prevented by addition of either oleate or acetate, but not by pyruvate. When cell growth was supported by oleate, HFA inhibited the incorporation of radioactive carbon from glucose-U-(14)C or pyruvate-2-(14)C into fatty acids and sterols. The incorporation of radioactive carbon into fatty acids and sterols from acetate-2-(14)C was unaffected by the compound. When cell growth was supported by either oleate or acetate, HFA inhibited the conversion of pyruvate-1-(14)C to (14)CO(2). These results suggest that HFA inhibits the conversion of pyruvate to acetate in yeast. Partially purified yeast pyruvate dehydrogenase was inhibited 50% by 5.5 mm HFA; however, the concentration required for 50% inhibition was considerably reduced when the enzyme was preincubated with the compound at room temperature. In a similar manner, the hypolipidemic agent clofibrate-free acid inhibited the growth of yeast by 50% at 3.0 mm. This inhibition was also prevented by acetate and not by pyruvate. In addition, clofibrate-free acid inhibited partially purified pyruvate dehydrogenase by 50% at a concentration of 37.0 mm.

Acetates↗
PubMed1991

Pathway and carbon sources for hepatic glycogen repletion in dogs.

The present studies were undertaken to quantitate the relative contributions of the indirect and direct pathways for hepatic glycogen repletion and to determine the role of splanchnic tissues in provision of C precursors used for the indirect pathway. For this purpose, we administered oral glucose (1.4 g/kg) enriched with [1-14C]glucose to 18-h fasted dogs and measured net hepatic and net gastrointestinal glucose, lactate, and alanine balance, hepatic and gastrointestinal fractional extraction [( 3H]lactate), release and uptake of lactate, as well as the total amount of hepatic glycogen formed from the oral glucose and the 14C labeling pattern of the glycogen-glucose C. Although net hepatic glucose uptake (8.7 +/- 0.6 g, 27% of the oral load) exceeded the amount of glycogen formed from the oral glucose (6.3 +/- 1.1 g), analysis of radioactivity in C-1 of the glycogen glucose indicated that nearly 50% of the glycogen was formed by the indirect pathway. Net hepatic uptake of lactate (1.4 +/- 0.1 g) and alanine (1.5 +/- 0.1 g) could account for greater than 90% of glycogen formed by the indirect pathway if all of the lactate and alanine taken up by the liver had been incorporated into glycogen. Release of lactate and alanine by splanchnic tissues approximated the amount of lactate and alanine taken up by the liver. However, in addition to taking up lactate, the liver also produced nearly as much lactate as the gastrointestinal tract (1.8 +/- 0.2 vs. 2.0 +/- 0.3 g, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1971

The formation of glycoproteins in tissues of higher plants. Specific labelling with D-(1- 14 C)glucosamine.

1. Radioactivity from d-[l-(14)C]glucosamine is incorporated into ethanol-insoluble compounds of high molecular weight in a number of plant tissues, including roots of corn (Zea mays), callus cells of sycamore (Acer pseudoplatanus), axenic cultures of duckweed (Lemna minor) and germinating seedlings of corn, broad bean (Vicia faba) and barley (Hordeum vulgare). 2. Except in the case of Lemna, where some of the radioactivity was recovered in glucose, hydrolysis of these ethanol-insoluble materials with acid released [(14)C]glucosamine as the major radioactive product. 3. The labelled compounds isolated from Zea roots and the Acer cells are believed to be glycoproteins rather than polysaccharides on the basis of their solubility properties, their charge characteristics and their susceptibility to hydrolysis by 0.5m-potassium hydroxide and by the proteases trypsin and Pronase. Further, radioactive peptides were isolated and purified after Pronase treatment and shown to contain glucosamine as well as a number of amino acids. 4. The experiments therefore indicate that d-[(14)C]glucosamine can be used as a specific precursor of the amino sugar units of plant as well as animal glycoproteins.

Alkalies↗
PubMed1992

Action of neopullulanase. Neopullulanase catalyzes both hydrolysis and transglycosylation at alpha-(1----4)- and alpha-(1----6)-glucosidic linkages.

The transglycosylation reaction catalyzed by neopullulanase was analyzed. Radioactive oligosaccharides were produced when the enzyme acted on maltotriose in the presence of [U-14C]glucose. Some of the radioactive oligosaccharides had only alpha-(1----4)-glucosidic linkages, but others were suggested to have alpha-(1----6)-glucosidic linkages. The existence of alpha-(1----6)-glucosidic linkages in the products from maltotriose with neopullulanase was proven by proton NMR spectroscopy and methylation analysis. We previously reported that the one active center of neopullulanase catalyzes the hydrolysis of alpha-(1----4)- and alpha-(1----6)-glucosidic linkages (Kuriki, T., Takata, H., Okada, S., and Imanaka, T. (1991) J. Bacteriol. 173,6147-6152). These facts proved that neopullulanase catalyzed all four types of reactions: hydrolysis of alpha-(1----4)-glucosidic linkage, hydrolysis of alpha-(1----6)-glucosidic linkage, transglycosylation to form alpha-(1----4)-glucosidic linkage, and transglycosylation to form alpha-(1----6)-glucosidic linkage. The four reactions are typically catalyzed by alpha-amylase, pullulanase, cyclomaltodextrin glucanotransferase, and 1,4-alpha-D-glucan branching enzyme, respectively. These four enzymes have some structural similarities to one other, but reactions catalyzed by the enzymes are considered to be distinctive: the four reactions are individually catalyzed by each of the enzymes. The experimental results obtained from the analysis of the reaction of the neopullulanase exhibited that the four reactions can be catalyzed in the same mechanism.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1990

Brain glucose metabolism in noninsulin-dependent diabetes mellitus: a study in Pima Indians using positron emission tomography during hyperinsulinemia with euglycemic glucose clamp.

To determine whether insulin or noninsulin-dependent diabetes mellitus affects brain glucose metabolism, brain glucose utilization was studied in the basal state and during hyperinsulinemic euglycemic glucose clamps in nondiabetic and diabetic Pima Indians by positron emission tomography with 2-[18F]fluoro-2-deoxy-D-glucose (18FDG). Glucose utilization in 75 brain areas was determined by analysis of single scans and by least squares estimation of the rate parameters for the FDG model; these data were compared to results in normal caucasian volunteers. No effect of ethnicity or diabetic status on brain glucose utilization was observed. During the hyperinsulinemic clamps (mean insulin, 11,708 +/- 3,026 pmol/L), clearance of 18FDG from blood was accelerated, and accumulation of brain radioactivity was reduced. However, glucose utilization by the brain was identical to results during sham glucose clamps (mean insulin, 204 +/- 56 pmol/L) performed in the same patients. During the studies with hyperinsulinemia, k4 (representing loss of tissue radioactivity) was increased in most brain areas (mean increase, 0.0031 +/- 0.0018 min-1; P less than 0.02). The possible mechanisms for this effect are multiple, and the physiological significance, if any, is unknown. Further studies of the effects of insulin on brain glucose metabolism are needed.

Adult↗
PubMed1982

Role of the adenylate system and glycolytic flux in the control of protein synthesis in isolated rat lung cells.

(1) Glucose stimulates the incorporation of amino acids into protein in lung cells isolated by digestion of the lung stroma with collagenase. This effect reflects mainly an increase in protein synthesis since no effect of glucose had been found to the uptake of amino acid precursors and, although glucose decreases the rate of intracellular proteolysis by 15%, this effect cannot account for the increased incorporation of radioactivity into proteins. Furthermore, glucose did not induce any significant change in the intracellular content of valine. (2) For glucose to act on protein synthesis, it must be glycolyzed since its stereoisomer, L-glucose, which is not metabolized by lung cells, has no effect. (3) The mechanism of glucose action does not seem to be related simply to variations of cellular ATP content or energy charge. The following arguments seem to support this conclusion: (i) glucose does not bring about significant variations in the concentration of reactants of the adenylate system; (ii) the increase in protein synthesis induced by glucose in energy-depleted cells correlates with a rise in ATP content and energy charge; however, adenosine, which increases ATP levels in a form quantitatively similar to glucose, is unable to affect protein synthesis: (iii) glucose also accelerates the incorporation of amino acids into proteins in adenosine-treated lung cells in which the ATP concentration was almost double that of the control and the energy charge was considerably elevated, ruling out the possibility that a rise in the steady-state concentration of ATP and/or energy charge alone could be responsible for the acceleration of protein synthesis. (4) It can be concluded that the effect of glucose in increasing protein synthesis in lung cells is dependent on some signal arising from its breakdown and not to variations in the concentration of reactants or energy charge of the adenylate system.

Adenine Nucleotides↗
PubMed1974

Patterns of food utilization by the germinating lettuce seeds.

The embryo excised from seed of Grand Rapids lettuce (Lactuca sativa L.) can be cultured in distilled water. Complete digestion of the endosperm and transfer of nutrients from the endosperm to the embryo occur in the germinating seed with fat as the source of food. The fat is utilized for respiration, synthesis of amino acids, and to a degree, converted to sucrose. (14)C-Glucose administered to the seed is quickly converted to sucrose in the endosperm and translocated to the embryo. Radioactivity associated with the glucose remains predominantly in the carbohydrate fraction, and much of it is incorporated into what is believed to be cell wall polysaccharides. Relatively little isotope is distributed in the amino or organic acids.

Journal Article↗
PubMed1983

Endogenous prostaglandin synthesis and glucose-induced insulin secretion from the adult rat pancreatic islet.

Although exogenous prostaglandins are recognized modulators of insulin secretion, the relationship between their endogenous synthesis and insulin secretion has not been rigorously studied in isolated adult rat islets. Using 3H-arachidonic acid as a tracer, we evaluated the effect of glucose stimulation upon the incorporation of this fatty acid into islet phospholipids and prostaglandins (separated by extraction and sequential silicic acid, thin-layer and paper chromatography). We observed that 3H-arachidonic acid was incorporated into islet phospholipids and prostaglandins under basal conditions (0.3 mg/ml glucose). Furthermore, exposure of islets to a stimulatory glucose concentration led to significant increases in the recovery of 3H-arachidonic acid-derived radioactivity in islet phosphatidylethanolamine, phosphatidylserine, sphingomyelin, and phosphatidylinositol as well as into all of the measured prostaglandins (A2, B2, D2, E2, and F2 alpha). The most marked increases in recovered radioactivity resulting from a stimulatory glucose concentration were in islet phosphatidylethanolamine and prostaglandin A2 (which we believe to be derived, in large part, from endogenously synthesized prostaglandin E2). These glucose-induced increases in 3H-arachidonic acid-derived radioactivity in both the phospholipid and the prostaglandin fractions were eliminated by the inhibition of phospholipase A2 activity with mepacrine or by the inhibition of cyclooxygenase activity with sodium salicylate. When islets prelabeled with 3H-arachidonic acid were exposed to a high glucose concentration in a perifusion system, there was a brisk extracellular release of radioactivity (presumably representing unidentified prostaglandins) that began within 1 min and that peaked slightly before the peak of the first phase of insulin secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

D- and L-glucose transport across the pulmonary epithelium.

Previously we observed what appeared to be augmented D-glucose transport across the pulmonary epithelium. To investigate this phenomenon we placed fluid containing L-[3H]glucose and D-[U-14C]glucose in the alveoli of isolated Ringer-perfused lungs from 4-wk-old rabbits. The appearance of radioactivity in recirculating glucose-free perfusate was measured. 3H appearing in the perfusate was associated with L-glucose. 14C, however, was associated with three compounds, with approximate molecular weights of 180 (glucose), 300, and 560. The nonglucose species were not identified. This 14C movement was inhibited by phlorizin, but not phloretin, in the alveolar fluid. A similar pattern of 14C movement occurred when D-[U-14C]glucose was replaced with 2-deoxy-D-[U14C]-glucose, but not with methyl-alpha-D-[U-14C]glucopyranoside. The activation energy of the 14C metabolism-transport process was found to be 34 kcal/mol, and L-glucose transport showed an unusual temperature dependence, with maximum conductance at 15 degrees C. It appears that some D-glucose crosses the pulmonary epithelium as does L-glucose. However, most enters epithelial cells and is incorporated into larger molecules which enter the vascular but not the alveolar space.

Animals↗
PubMed1991

[The mechanism of the reduction of protein catabolism following trauma and during sepsis using xylitol].

Total parenteral nutrition (TPN) after trauma and sepsis has two major goals. One is the reduction of enhanced protein catabolism; the second is the avoidance of enhancement of whole-body glucose turnover. Glucose and xylitol differ in their quantitative utilization rate after trauma and sepsis. Maximal glucose utilization is reduced during such states, while the utilization of xylitol is more than doubled. In order to investigate whether these differences are associated with beneficial effects with regard to whole-body glucose turnover rate of gluconeogenesis and protein sparing, we conducted two studies using animal models and two clinical studies. METHODS. For the determination of glucose and protein turnover, radioactive and stable isotope techniques were applied. In an animal model a primed constant infusion of 3-H-6-glucose, 14-C-1-alanine and 13-C-3-alanine and 14-C-U-acetate was used to determine total glucose appearance, gluconeogenesis from 3-C-precursors and alanine flux. In the human studies hepatic glucose production was determined by using a primed constant infusion of 6.6-D-2-glucose and urea synthesis rate was determined by a primed constant infusion of 2-N-15-urea. RESULTS. In the first rat model we were able to show that hypocaloric xylitol compared to glucose significantly reduced whole-body glucose turnover from 1741 +/- 232 mumol/h during glucose infusion to 449 +/- 49 mumol/h during xylitol infusion and gluconeogenesis from C-3 carbons form 382 +/- 24 mumol/h during glucose infusion to 155 +/- 39 mumol/h during xylitol infusion after a burn trauma. In a second septic rat model the exchange of glucose calories by xylitol in a proportion of 1:1 was associated with a significantly ameliorated N-balance from +144 +/- 90 mgN/kg body weight per day during glucose infusion to +699 +/- 80 mgN/kg body weight per day during glucose-xylitol infusion and a reduced 3-methyl-histidine excretion from 7.14 +/- 0.61 mumol/kg body wt. per day during glucose infusion to 4.10 +/- 0.56 mumol/kg per day during glucose-xylitol infusion, respectively. In two studies with surgical intensive care patients we were able to confirm the nitrogen-sparing properties of xylitol infusion, together with amino acids during hypocaloric feeding or during TPN with a glucose/xylitol mixture in a proportion of 1:1. From a basal urea production rate of 9.2 +/- 1.6 mumol/kg min. xylitol led to a significant reduction with 6.4 +/- 1.5 mumol/kg per min. Hepatic glucose production was significantly reduced during xylitol infusion from basal 4.8 +/- 0.6 mg/kg per min to 3.1 +/- 0.7 mg/kg per min, respectively. Equicaloric glucose in a dosage of 3 g/kg per day had no effect. During TPN glucose/xylitol, in a proportion of 1:1 at a total dosage of 0.24 g/kg per h, significantly reduced whole-body glucose turnover, endogenous glucose production and lactate concentrations compared to an isocaloric glucose infusion. DISCUSSION. In animal as well as in human studies hypocaloric xylitol as well as a glucose-xylitol mixture were more efficient in preserving body protein than glucose alone. Whole-body glucose turnover was significantly reduced during hypocaloric xylitol or glucose-xylitol infusion compared to isocaloric glucose infusion. During the acute phase after trauma we therefore recommend a carbohydrate supplementation of 3 g/kg body wt. per day using xylitol. During long-term TPN, a glucose-xylitol mixture in a proportion of 1:1 in a dosage of 3 g/kg body wt. per day each is recommended as energy source, together with amino acids and, if necessary, lipids.

Animals↗