Daily consumption of milk enriched with fish oil, oleic acid, minerals and vitamins reduces cell adhesion molecules in healthy children.

BACKGROUND AND AIMS: Several studies have suggested that polyunsaturated fatty acids, vitamins and minerals have beneficial effects on lipid profile and systemic inflammation in adults. METHODS AND RESULTS: We examined the effects of a daily intake of milk enriched with longchain polyunsaturated fatty acids, oleic acid, carbohydrates, vitamins, minerals and low in saturated fatty acids (SFAs) for 5 months, on several cardiovascular (CVD) risk biomarkers in healthy children aged 8-14 years. In a randomized double-blind placebo-controlled trial, a total of 107 children of both genders were assigned to two study groups: 1) a supplemented group (SG, n=53) who consumed 0.6 L/day of an enriched dairy product, and 2) a control group (CG, n=54) who consumed 0.6 L/day of standard whole milk. Both groups consumed the dairy drinks for 5 months, in addition to their usual diet. Serum levels of adhesion molecules as indices of vascular endothelial cell activation were assessed in both groups at 0 and 5 months as well as white blood cell counts, lipid profile, serum proteins, total serum calcium, 25-OH vitamin D, glucose, insulin and adiponectin. In the enriched dairy drink supplemented group, adhesion molecules E-selectin and ICAM-1 as well as lymphocyte levels decreased while plasma docosahexaenoic acid (DHA) and serum calcium concentrations increased. In the control group, serum total protein, transferrin, total cholesterol, HDL-cholesterol and adiponectin concentrations decreased. CONCLUSION: The consumption of a milk enriched with fish oil, oleic acid, minerals and vitamins reduced indices of endothelial cell activation in the studied group of healthy children.

[Intake of an iron-supplemented milk formula as a preventive measure to avoid low iron status in 1-3 year-olds]. / Ingesta de una fórmula láctea suplementada con hierro como medida preventiva del déficit de hierro en niños de 1 a 3 años de edad.

OBJECTIVE: Low iron status is a well known risk factor for iron deficiency anemia in infants and young children. The aim of the present study was to evaluate the influence of an iron-fortified toddler formula on iron status in 1-3 year-olds. PATIENTS AND METHODS: Thirty-three healthy infants and young children were assigned to two groups that received 500 mL/day of and iron-fortified toddler formula or 500 mL/day of unmodified cow's milk for 4 months. Allocation was random and double-blind. Daily dietary intake was calculated by dietary evaluation, and iron nutritional status was assessed (hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, serum iron, ferritin, and transferrin). RESULTS: At enrollment, no anemia was found in either group, although hemoglobin concentration and hematocrit were significantly lower in the toddler formula group than in the unmodified cow's milk group. However, these differences disappeared at the end of the intervention period. After 4 months, the toddler formula group showed significantly higher serum ferritin and lower serum transferrin concentrations than the cow's milk group. CONCLUSION: Intake of iron-supplemented toddler formula for 4 months in 1-3 year-olds is more effective in maintaining iron nutritional status than cow's milk.

Ingesta de una fórmula láctea suplementada con hierro como medida preventiva del déficit de hierro en niños de 1 a 3 años de edad / Intake of an iron-supplemented milk formula as a preventive measure to avoid low iron status in 1-3 year-olds

Objetivo. La baja ingesta de hierro es un factor bien conocido como responsable de anemia por deficiencia de hierro en lactantes y niños pequeños. En el presente estudio se ha evaluado la influencia de la ingesta de una fórmula láctea para niños pequeños suplementada con hierro sobre el estado nutricional del hierro en niños de 1 a 3 años de edad. Pacientes y métodos. Se han estudiado 33 niños sanos distribuidos de forma aleatorizada y doble ciego en 2 grupos, uno que tomó 500 ml/día de una fórmula láctea suplementada con hierro y otro 500 ml/día de leche entera de vaca. Todos los niños tomaron la fórmula o la leche de vaca durante 4 meses. La ingesta de nutrientes fue calculada mediante la valoración de la dieta y se evaluó el estado nutricional del hierro (hemoglobina, hematócrito, volumen corpuscular medio, hemoglobina corpuscular media, concentración de hemoglobina corpuscular media, hierro, ferritina y transferrina). Resultados. Al inicio del estudio, ningún niño presentaba anemia, aunque el grupo que tomó la fórmula láctea suplementada con hierro presentaba una concentración de hemoglobina y hematócrito significativamente más baja. Sin embargo, las diferencias desaparecieron al final del período de intervención. Además, al final del estudio el grupo que tomó la fórmula láctea suplementada con hierro mostró unas concentraciones en suero significativamente más elevadas de ferritina y más bajas de transferrina que el grupo que tomó leche entera de vaca. Conclusión. La ingesta de una fórmula suplementada con hierro para niños pequeños durante 4 meses en niños de 1 a 3 años de edad, contribuye mejor que la leche de vaca a mantener el estado nutricional de hierro

Objective. Low iron status is a well known risk factor for iron deficiency anemia in infants and young children. The aim of the present study was to evaluate the influence of an iron-fortified toddler formula on iron status in 1-3 year-olds. Patients and methods. Thirty-three healthy infants and young children were assigned to two groups that received 500 mL/day of and iron-fortified toddler formula or 500 mL/day of unmodified cow's milk for 4 months. Allocation was random and double-blind. Daily dietary intake was calculated by dietary evaluation, and iron nutritional status was assessed (hemoglobin, hematocrit, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, serum iron, ferritin, and transferrin). Results. At enrollment, no anemia was found in either group, although hemoglobin concentration and hematocrit were significantly lower in the toddler formula group than in the unmodified cow's milk group. However, these differences disappeared at the end of the intervention period. After 4 months, the toddler formula group showed significantly higher serum ferritin and lower serum transferrin concentrations than the cow's milk group. Conclusion. Intake of iron-supplemented toddler formula for 4 months in 1-3 year-olds is more effective in maintaining iron nutritional status than cow's milk

[Cardiovascular effects of omega-3-fatty acids and alternatives to increase their intake]. / Efectos cardiovasculares de los ácidos grasos omega-3 y alternativas para incrementar su ingesta.

Cardiovascular diseases are the main mortality cause in Europe, the USA and a great extent of Asia. There are several risk factors associated with cardiovascular diseases, such as increased total cholesterol, homocysteine and triglycerides, hypertension, diabetes, and reduced levels of HDL-cholesterol. Many of these risk factors are diet influenced. In spite of the great amount of foods enriched with n-3 fatty acids available at the market, the knowledge about the effects produced by regular intake of these foods still is a challenge in the majority of cases. It appears that intake of foods enriches with n-3 polyunsatured fatty acids is an option that may be effective in reducing risk factors for diseases, by substituting supplements without modifying consumer's alimentary habits. Also shown are the outcomes from a nutritional study undergone with a functional milk-bases food that contains n-3 fatty acids, oleic acid and vitamins.

n-3 Fatty acids plus oleic acid and vitamin supplemented milk consumption reduces total and LDL cholesterol, homocysteine and levels of endothelial adhesion molecules in healthy humans.

BACKGROUND AND AIMS: Numerous studies suggest n -3 polyunsaturated fatty acids (n -3 PUFA) and oleic acid intake have beneficial effects on health including risk reduction of coronary heart disease. The purpose of this study was to evaluate the effect of a commercially available skimmed milk supplemented with n -3 PUFA, oleic acid, and vitamins E, B(6), and folic acid (Puleva Omega3) on risk factors for cardiovascular disease. (CVD). METHODS: Thirty volunteers were given 500 ml/day of semi-skimmed milk for 4 weeks and then 500 ml/day of the n -3 enriched milk for 8 further weeks. Plasma and LDL lipoproteins were obtained from volunteers at the beginning of the study (T(pre)), and at 4, 8 and 12 weeks. RESULTS: The consumption of n -3 enriched milk produced a significant decrease in plasma concentration of total and LDL cholesterol accompanied by a reduction in plasma levels of homocysteine. Plasma and LDL oxidability and vitamin E concentration remained unchanged throughout the study. A significant reduction in plasma levels of vascular cell adhesion molecule 1, and an increase in plasma concentration of folic acid were also observed. CONCLUSION: Daily intake of n -3 PUFA and oleic acid supplemented skimmed milk plus folic acid and B-type vitamins has favourable effects on risk factors for CVD.

Free and protein-bound glutamine have identical splanchnic extraction in healthy human volunteers.

The objectives of the present study were to determine the splanchnic extraction of glutamine after ingestion of glutamine-rich protein ((15)N-labeled oat proteins) and to compare it with that of free glutamine and to determine de novo glutamine synthesis before and after glutamine consumption. Eight healthy adults were infused intravenously in the postabsorptive state with L-[1-(13)C]glutamine (3 micromol x kg(-1) x h(-1)) and L-[1-(13)C]lysine (1.5 micromol x kg(-1) x h(-1)) for 8 h. Four hours after the beginning of the infusion, subjects consumed (every 20 min) a liquid formula providing either 2.5 g of protein from (15)N-labeled oat proteins or a mixture of free amino acids that mimicked the oat-amino acid profile and contained L-[2,5-(15)N(2)]glutamine and L-[2-(15)N]lysine. Splanchnic extraction of glutamine reached 62.5 +/- 5.0% and 66.7 +/- 3.9% after administration of (15)N-labeled oat proteins and the mixture of free amino acids, respectively. Lysine splanchnic extraction was also not different (40.9 +/- 11.9% and 34.9 +/- 10.6% for (15)N-labeled oat proteins and free amino acids, respectively). The main conclusion of the present study is that glutamine is equally bioavailable when given enterally as a free amino acid and when protein bound. Therefore, and taking into consideration the drawbacks of free glutamine supplementation of ready-to-use formulas for enteral nutrition, protein sources naturally rich in this amino acid are the best option for providing stable glutamine.

Effect of glutamine supplementation of the diet on tissue protein synthesis rate of glucocorticoid-treated rats.

Although glutamine status in the critically ill patient can be improved by nutritional means, the most effective way of effecting such supplementation has received little attention. We evaluated two different ways of supplementing clinical nutrition products with glutamine, either with free glutamine or by providing a glutamine-rich protein source, in acute glucocorticoid-treated (intraperitoneal dexamethasone, 120 mg/kg) rats. During the recovery period, the animals received isonitrogenous and isoenergetic diets containing either casein, mixed whey proteins with or without glutamine, or carob protein plus essential amino acids. Plasma and tissue amino acids and glutathione as well as tissue protein synthesis were measured. Dexamethasone treatment lowered weight gain, muscle glutamine, and muscle and jejunal protein synthetic rate. Muscle protein synthesis was increased (from 15.9% to 24.2%/d) only when glutamine was included in the diet as a free amino acid. This increase paralleled a rise in plasma glutamine. We speculate that glutamine provided in dietary protein is extensively metabolized by the splanchnic tissues and does not influence peripheral glutamine status to the same extent as glutamine provided in a free amino acid form. However, both forms of glutamine supplementation were equally effective in increasing protein synthesis in the jejunum (by 25%). This is likely the main benefit of glutamine supplementation of enteral nutrition formulas.

Componentes biológicamente activosde la leche materna / Bioactive compounds derived from human milk

La leche materna es un complejo fluido biológico que aporta la energía y los nutrientes esenciales para el desarrollo y crecimiento del recién nacido. Pero además, la leche materna contiene toda una serie de compuestos bioactivos como enzimas, hormonas, factores de crecimiento, proteínas específicas, poliaminas, nucleótidos, oligosacáridos, etc., que ejercen efectos biológicos y que en conjunto reciben el nombre de "factores tróficos de la leche". Estos compuestos biactivos son considerados nutrientes potencialmente esenciales en periodos de desarrollo y en determinadas enfermedades, cuando la capacidad de síntesis no supera las necesidades de los mismos. Aunque las fórmulas infantiles aportan todos los nutrientes para un adecuado desarrollo del recién nacido, carecen de muchos de estos compuestos. Este artículo pretende realizar una revisión acerca de los conocimientos actuales sobre los efectos biológicos de la lactoferrina, nucleótidos, poliaminas y oligosacáridos (AU)

Neither glutamine nor arginine supplementation of diets increase glutamine body stores in healthy growing rats.

The aim of the work was to resolve whether glutamine and arginine supplemented diets affect plasma and tissue (muscle, liver and intestinal mucosa) glutamine concentrations, as well as glutaminase and glutamine synthetase specific activities. The trial was performed in growing rats fed 10% protein diets for 3 weeks. Protein sources were: whey proteins (W); whey proteins+free glutamine (WG); whey proteins+arginine (WA); and casein+wheat protein hydrolysate+acid whey (39:39:22), as source containing protein-bound glutamine (CGW). Rats fed the control diet (6.4% glutamine) (W) showed comparable glutamine body stores to those of rats fed the WG diet. In fact, glutamine sup- plementation down-regulated the hepatic glutamine synthetic capacity of growing rats (W/WG: 6.8+/-0.3 vs 6.0+/-0.2 nmol/min/mg protein). Arginine supplementation of the diet (up to 9% of the protein content) resulted in a decrease in plasma and tissue glutamine concentrations (W/WA: plasma, 1218+/-51 vs 1031+/-48 micromol/L; liver 7.5+/-0.4 vs 6.5+/-0.2 micromol/g; muscle: 5.7+/-0.2 vs 4.0+/-0.2 micromol/g). These data suggest that glutamine supplementation of the diet does not increase plasma and tissue glutamine concentrations in healthy growing rats, while the addition of arginine to the diet decreases glutamine body stores.

Role of glutamine on the de novo purine nucleotide synthesis in Caco-2 cells.

BACKGROUND: The body's nucleotide pool derives from three potential sources: de novo synthesis, salvage of preformed-nucleosides/bases or the diet. The relative contributions of these pathways of assimilation are poorly understood in vivo. Dietary nucleotides have been suggested to have beneficial effects an the development and repair of the gastrointestinal tract. Tissues with a rapid turnover, such as the gut and the immune system cells, may utilise preformed nucleotides (coming from the diet), in situations in which there is a high demand of nucleotides for nucleic acid synthesis. Therefore, nucleotides could be considered as conditionally essential nutrients. AIM OF THE WORK AND METHODS: Development of a method to measure synthesis de novo of RNA-purine nucleotides in Caco-2 cells, relying an the incorporation of 14C-glycine into the purine ring of the nucleotide. To establish the fractional synthesis rate of RNA purine nucleotides in Caco-2 cells, grown in culture medium containing different concentrations of glutamine, in the presence or absence of added nucleotides. To investigate the degree to which tissue ribonucleosides are derived from the culture medium or from de novo synthesis in the presence of different concentrations of glutamine, using undifferentiated Caco-2 cells, stressed or not by the addition of IL-1 beta to the medium. RESULTS AND CONCLUSIONS: The presence of high levels of glutamine in the culture medium is essential for cell proliferation (estimated by measurement of the fractional synthesis rate of purine nucleotides) and the presence of nucleotides cannot replace the glutamine dependence of Caco-2 cell proliferation. The incorporation of exogenous purine nucleotides into RNA of Caco-2 cells is rather limited, and it becomes important when cells are stressed by glutamine deprivation. Stress by addition of interleukin-1 beta resulted in the maintenance or the increase in de novo synthesised RNA-purine nucleotides, even in the presence of exogenous nucleotides. However, the addition of interleukin-1 beta to the culture medium led to an enhanced salvage of preformed pyrimidine nucleotides for nucleic acid synthesis when glutamine was present in the medium at a concentration of 0.5 mmol/L.

Plasma glutamine response to enteral administration of glutamine in human volunteers (free glutamine versus protein-bound glutamine).

The goal of the present work was to compare the plasma glutamine response to exogenous glutamine administration in human volunteers; glutamine was provided as a free amino acid, bound to proteins, or in the form of peptides. Plasma glutamine concentrations were measured in eight human volunteers at 30, 60, 90, 120, and 240 min after receiving a drink containing 30 g of protein from one of the five different proteins tested (sodium caseinate, sodium caseinate + free glutamine, carob germ flour, carob protein concentrate, and carob protein hydrolysate). Peak plasma glutamine concentrations were 42% higher than postabsorptive basal values when exogenous glutamine was administered in the form of free glutamine added to caseinate (925.9 +/- 67.7 versus 651.3 +/- 44.0 micromol/L, respectively). In contrast, when glutamine was offered 100% bound to proteins (carob proteins), peak plasma glutamine concentration increased only between 18% and 23% from basal values, possibly because of the lower digestibility of carob proteins versus that of caseinate + free glutamine, to a different glutamine utilization at the gut level, or to a different response in endogenous glutamine kinetics to enteral administration of glutamine, depending on the molecular form of the glutamine source (free or protein bound).

Methods for measuring tissue RNA turnover.

Measuring RNA turnover is important because of the significance of rRNA, tRNA and mRNA in tissue protein synthesis. Changes in turnover of each of these species precede important cellular events such as hormone or cytokine action or cell-division itself. Isotopic methods have relied on decay of pulse-labelled RNA or on incorporation of isotopically-labelled precursors. However, recycling of labels may lead to under or overestimation of synthesis rates respectively. The labelling of the intracellular precursor pool must be known if accurate RNA synthesis rates are to be calculated from the degree of incorporation. However, the intracellular nucleotide pools may be anatomically or metabolically compartmented (i.e. via de novo or salvage synthesis routes) and this complicates many study designs. The use of[methyl-14C]- or [methyl-3H]methionine as a means of labelling methylated nucleosides in RNA and protein simultaneously is described in addition to new stable isotopic techniques based on 13C-glycine as a de novo label. Urinary excretion of the numerous modified nucleosides in cellular RNA can be used to calculate whole-body turnover rates of each of the major RNA species. Examples of the effects of critical-illness and glutamine supplementation on RNA turnover are given. We conclude by suggesting that whole-body RNA turnover rates have been significantly underestimated and that this has implications for nutritional therapy, especially with regard to nucleotide supplementation.

Protein hydrolysate vs free amino acid-based diets on the nutritional recovery of the starved rat.

BACKGROUND AND AIMS: To test the hypothesis that a peptide-based enteral product was equivalent to a low-fat, free amino acid-based formula in the nutritional and functional recovery of the starved rat. METHODS: Sixteen male Wistar rats were starved for 3 days. Then, rats were randomised to a whey protein hydrolysate-based diet or a free amino acid-based diet and refed for 3 days. The experiment was designed to provide the same energy intake in both groups. The parameters studied included body weight gain, nitrogen retention, plasma free amino acid concentrations, muscle glutamine concentrations and glutathione levels in gut mucosa and liver. RESULTS: Weight gain was statistically higher on the peptide-based diet than on the elemental diet after the refeeding period. This difference in weight gain was associated with a statistically higher nitrogen retention. Plasma and muscle free glutamine concentrations were higher in rats fed the whey protein hydrolysate-based diet than those in rats refed the free amino acid-based diet, even though the glutamine intake was higher in the latter group. Glutathione concentrations in liver and gut mucosa were similar in the groups. CONCLUSION: We conclude that enteral diets containing peptides were more effective than a diet containing free amino acids in the nutritional recovery of the starved rat.

Food deprivation and refeeding influence growth, nutrient retention and functional recovery of rats.

The objective of this work was to determine the effects of starvation and refeeding on growth, nutritional recovery and intestinal repair in starved rats. Male Wistar rats, weighing 200 g, were starved for 3 d, then refed a soy-based diet for another 3 d. Normally fed rats were given the same diet and used as controls. The variables assessed were as follows: body weight gain and nitrogen retention during recovery after starvation; muscle glutamine concentration; tissue protein content; gut mucosa and liver glutathione levels; intestinal permeability to ovalbumin, lactulose and mannitol; and intestinal tissue apoptosis. Starvation was associated with lower muscle glutamine levels and intestinal mucosa impairment, including a lower content of mucosal protein, a higher level of oxidized glutathione, enhanced permeability to macromolecules and greater numbers of apoptotic cells. Refeeding for 3 d resulted in rapid repair of gut atrophy and normalization of not only intestinal permeability but also of the majority of metabolic markers assessed in other tissues. In conclusion, with the use of severely starved rats, we have established a reversible experimental animal model of malnutrition that might prove useful in comparing the effectiveness of different enteral diets.

Use of different dietary protein sources for lactating goats: milk production and composition as functions of protein degradability and amino acid composition.

To establish the effect of the nature of four different protein sources [fababeans, 27.8% crude protein (CP); sunflower meal, 41.7% CP; corn gluten feed, 18.8% CP; and cottonseed, 18.3% CP] on milk protein production by goats, the ruminal degradation of these feeds was studied as was the amino acid (AA) composition of the original material and that of the undegradable fractions of the protein sources. Four diets were designed; 20% of their protein was supplied by each of the different sources. Four groups of 5 Granadina goats were used to study the utilization of these diets for milk production. No significant differences were observed in dry matter intake or milk production. The milk produced by goats fed the diet containing sunflower meal had the lowest protein concentration; the highest milk protein concentration was observed for goats fed the diet containing corn gluten feed. From a multivariate analysis, it was deduced that the quickly degradable protein fraction in the rumen and the ruminally undegradable protein fraction were the components of the protein sources most directly related to the milk protein produced. Given the similar AA profiles of the undegradable fractions of the different protein sources, the possible supplementation achieved from these ruminally undegradable fractions must be established by the amount of protein supplied regardless of AA composition.

Integration of amino acid and carbon intermediary metabolism: studies with uniformly labeled tracers and mass isotopomer analysis.

The central pathways of metabolism include glycolysis and gluconeogenesis, fatty acid synthesis and beta-oxidation, the citric acid cycle and ureagenesis. Because these pathways intersect, changes in one pathway, due to inborn error or disease, affect pathways that may seem remote from the initial metabolic defect. These metabolic interrelationships also present difficulties for isotopic studies, because once carbon derived from isotopic tracers is introduced into metabolism it is extensively recycled. The use of multiple labeled (especially uniformly 13C-labeled ([U-13C]), metabolic tracers, in conjunction with mass isotopomer distribution analysis of mass and nuclear magnetic spectra, has enabled the development of methods that resolve some of these difficulties. Suitable choices of tracers and analytes allow the simultaneous measurement of multiple pathways and, importantly, their kinetic interrelationships. We illustrate three uses of the technique: (1) the unequivocal determination of trace fluxes; (2) the quantification of biosynthetic pathways: and (3) the dissection, in vivo, of the citric acid (Krebs) cycle. In each case, different combinations of [U-13C]tracer and metabolic end product have revealed metabolic phenomena that otherwise would remain unidentified. A particularly striking, and unexpected, observation that has emerged from recent studies using the technique, suggests that the key dehydrogenase reactions in the Krebs cycle may be reversible. Although this approach is of relatively recent development, it has already given a number of novel insights into the organization of the central metabolic pathways. It should provide a powerful method of investigating the metabolic impact of genetic disease and provide invaluable support of the assessment of new therapeutic interventions.

Dietary nucleotides might influence the humoral immune response against cow's milk proteins in preterm neonates.

The objective of this study was to evaluate the influence of dietary nucleotide supplementation in preterm infants during the first month of life on the intestinal permeability to lactulose, mannitol and to beta-lactoglobulin and on the development of circulating antibodies to beta-lactoglobulin and alpha-casein. Twenty-seven preterm infants were enrolled in the study; 11 of them were fed a standard low-birth weight milk formula and 16 infants were fed the same formula supplemented with nucleotides at similar levels to those found in human milk. Blood and urine samples were obtained at 1, 7 and 30 days of age. Serum beta-lactoglobulin, serum IgG antibody to alpha-casein and serum IgG antibody to beta-lactoglobulin were measured by ELISA. The lactulose/mannitol urinary excretion rate was measured by gas liquid chromatography. Neither the intestinal permeability to saccharides nor the intestinal absorption of beta-lactoglobulin were affected by the nucleotide supplementation. However, serum concentrations of IgG antibody to beta-lactoglobulin were higher in preterm neonates fed the supplemented formula than in those fed the standard formula. According to these results, dietary nucleotides might influence the maturation of the humoral immune response in preterm newborn infants.

Ribonucleic acid nucleotides in maternal and fetal tissues derive almost exclusively from synthesis de novo in pregnant mice.

The contributions of dietary nucleotides and nucleotides synthesized de novo to ribonucleic acid synthesis in vivo were estimated by feeding, from d 13 to 18 of gestation, two groups of five pregnant mice a defined diet that contained either uniformly [U13C]-labeled nucleotides or [U13C]-algal amino acids isolated from algal biomass. Ribonucleic acid and protein were isolated from mucosa, liver and fetus. Nucleosides and amino acids were isolated and converted to their trimethylsilyl and n-propyl ester, heptaflurobutyramide derivatives, respectively. The isotopic enrichments of all isotopomers were determined by gas chromatography-mass spectrometry. In the mice that ingested [U13C]-nucleotides, the isotopic enrichment of [Ul3C]-purines (0.03-0.2 mol/100 mol) was significantly (P < 0.001) less than that of [U13C]-uridine (1.5-4.2 mol/100 mol). [13C5]-Purines (0.1-0.8 mol/100 mol) and [13C4]-uridine (0.2-0.5 mol/100 mol) were detected, showing that some dietary bases and ribose were incorporated via the salvage pathway. In mice that Ingested U13C-amino acids, the isotopic enrichment (2-4.6 mol/100 mol) of the [13C2]-purines, which derive from [Ul3C]-glycine, was between 73 (liver) and 113% (fetus) of protein-bound 13C2-glycine. The isotopic enrichment (0.8-1.6 mol/100 mol) of [13C3]-uridine, an isotopomer that derives from [U13C]-aspartate, was 50 (liver) to 126% (mucosa) of [13C4]-protein-bound aspartate. The results suggest that a large majority of the bases incorporated into maternal and fetal ribonucleic acids derive from synthesis de novo.

A rapid gas-liquid chromatography method for the determination of lactulose and mannitol in urine: clinical application in studies of intestinal permeability.

OBJECTIVE: The purpose of this study was to develop a gas-liquid chromatography method for the determination of the urinary excretion of two nonmetabolizable sugars (lactulose and mannitol) to estimate the intestinal permeability. METHODS: Two internal standards (alpha-methyl-D-glucopyranosyde and sucrose) were added to the urine samples prior to derivatization with the aid of a solution of pyridine, [N, O-bis (trimethylsilyl)]-acetamide and chlorotrimethylsilan. Sample preparation was simpler and faster than in other previous methods and the four sugars were resolved within 27 min. RESULTS: The inclusion of internal standards reduced the coefficient of variation from 9.44% to 4.78%. The method provided better sensitivity, range of analysis, and linearity than a previously published HPLC method reducing variances in the recovery of lactulose and mannitol added to urine. The clinical application of this method was tested in preterm infants fed human milk or cow's milk based formula and in breast fed term infants. CONCLUSION: The method described here for the determination of urinary lactulose and mannitol is more rapid, simpler, and more accurate than other previously published methods.