Metabolic Profiling Reveals Differences in Plasma Concentrations of Arabinose and Xylose after Consumption of Fiber-Rich Pasta and Wheat Bread with Differential Rates of Systemic Appearance of Exogenous Glucose in Healthy Men.

BACKGROUND: The consumption of products rich in cereal fiber and with a low glycemic index is implicated in a lower risk of metabolic diseases. Previously, we showed that the consumption of fiber-rich pasta compared with bread resulted in a lower rate of appearance of exogenous glucose and a lower glucose clearance rate quantified with a dual-isotope technique, which was in accordance with a lower insulin and glucose-dependent insulinotropic polypeptide response. OBJECTIVE: To gain more insight into the acute metabolic consequences of the consumption of products resulting in differential glucose kinetics, postprandial metabolic profiles were determined. METHODS: In a crossover study, 9 healthy men [mean ± SEM age: 21 ± 0.5 y; mean ± SEM body mass index (kg/m2): 22 ± 0.5] consumed wheat bread (132 g) and fresh pasta (119 g uncooked) enriched with wheat bran (10%) meals. A total of 134 different metabolites in postprandial plasma samples (at -5, 30, 60, 90, 120, and 180 min) were quantified by using a gas chromatography-mass spectrometry-based metabolomics approach (secondary outcomes). Two-factor ANOVA and advanced multivariate statistical analysis (partial least squares) were applied to detect differences between both food products. RESULTS: Forty-two different postprandial metabolite profiles were identified, primarily representing pathways related to protein and energy metabolism, which were on average 8% and 7% lower after the men consumed pasta rather than bread, whereas concentrations of arabinose and xylose were 58% and 53% higher, respectively. Arabinose and xylose are derived from arabinoxylans, which are important components of wheat bran. The higher bioavailability of arabinose and xylose after pasta intake coincided with a lower rate of appearance of glucose and amino acids. We speculate that this higher bioavailability is due to higher degradation of arabinoxylans by small intestinal microbiota, facilitated by the higher viscosity of arabinoxylans after pasta intake than after bread intake. CONCLUSION: This study suggests that wheat bran, depending on the method of processing, can increase the viscosity of the meal bolus in the small intestine and interfere with macronutrient absorption in healthy men, thereby influencing postprandial glucose and insulin responses. This trial was registered at www.controlled-trials.com as ISRCTN42106325.

Cancer-associated carbohydrate identification in Hodgkin's lymphoma by carbohydrate array profiling.

Tumor-associated carbohydrates have potential not only as diagnostic tools but also as specific therapeutic targets. Their identification, however, has been hampered by the lack of suitable technologies. We used carbohydrate array technology to compare serum antibody (IgG and IgM) levels against 37 different carbohydrates between classical Hodgkin's lymphoma (cHL) patients and age/sex-matched healthy controls. Serum IgM levels measured by ELISA against 2 of the 5 carbohydrates identified using this technique, L-alpha-arabinose (L-Araf) and alpha-N-acetylgalactosamine (GalNAc(alpha)), were higher (F values of 11.30 and 18.27, respectively) in a cohort of cHL patients (n = 16) than either diffuse large B-cell lymphoma patients (n = 18) or control sera (n = 12). Higher anti-L-Araf IgM levels in cHL patients were associated with cytosine arabinoside treatment (p < 0.05). The GalNAc(alpha) glycotope, Tn, was found to be heterogeneously expressed in the Reed-Sternberg cells of 9/20 (45%) cHL cases, but not in malignant cells of 25 cases of lymphocyte-predominant HL or another 21 hematological disorders (291 cases) examined immunohistochemically. Tn was expressed in 41/238 (17%) classical HL cases present on a tissue microarray. Expression was associated with CD79a and LMP1 expression and negatively with p27(KIP1) expression (p < 0.05). Kaplan-Meier survival analysis revealed a trend towards improved relapse-free survival with Tn expression although this was not statistically significant (p = 0.271). We suggest that this technique could provide a powerful tool for identifying novel carbohydrates in other cancers.

The utility of blood glucose meters in biotechnological applications.

Most methods used to measure glucose concentrations in biotechnological settings are labour-intensive and/or expensive. With this in mind we have investigated the possibility of employing blood glucose meters, the use of which has the benefit of being fast, convenient and inexpensive, for this purpose. Accu-Chek Advantage (Roche Diagnostics, Indianapolis, IN, U.S.A.) and Precision QID (Medisense, Abbott Laboratories, Indianapolis, IN, U.S.A.) meters were tested using glucose samples of known concentration, at pH 7.5 and 4.8. The Accu-Chek Advantage meter uses strips containing the enzyme glucose dehydrogenase. This meter showed a linear response for glucose concentrations between 0.50 and 6.0 g/litre, and the effect of pH was small. The Precision QID meter uses strips containing the enzyme glucose oxidase and is more sensitive to pH. The displayed glucose concentrations at low pH values were consistently lower than at higher pH values. At both pH values the response curve reached a plateau, which limited the effective range of this meter to a range of 0.30-2.5 g/litre. Unlike the Precision QID meter, the Accu-Chek Advantage meter also responded to xylose and arabinose. A synergistic effect of combining sugars was observed when a mixture of sugars consisting of glucose and arabinose, or glucose and xylose, was applied: the displayed concentrations were consistently higher than was expected on the basis of the individual calibration curves. The use of glucose meters is a fast and convenient alternative to existing methods and may be of particular use for screening purposes where a high degree of accuracy is not crucial. The choice of meter should depend on the application, and in this respect the pH, expected concentration range and the presence of other sugars are among the factors that should be considered.

L-Arabinosuria: a new defect in human pentose metabolism.

A female patient, the first child of healthy non-consanguineous parents, presented at the age of 16 months with delayed motor development and facial dysmorphism. In addition she displayed a palatoschizis and multiple skeletal abnormalities as hypoplastic scapulae, hypoplastic os ilea, and an extreme cervical kyphosis. Biochemical investigation of urine revealed no abnormalities except for the presence of large amounts of reducing sugars. The sugar was identified as L-arabinose, which mainly originated from fruit formula in her diet. In addition highly elevated levels of L-arabitol were found in urine, plasma, and cerebrospinal fluid. Although little is known about human arabinose metabolism, we presume that L-arabitol dehydrogenase is deficient in our patient. As polyols are potentially toxic to the central nervous system there could be deleterious long-term effects of this disorder. Withdrawal of dietary fruit led to normalization of polyol levels. The above-mentioned clinical abnormalities are probably not related to this new inborn error of metabolism and should be considered as a separate entity.

Passive absorption of hydrophilic carbohydrate probes by the house sparrow Passer domesticus.

To evaluate the permeability of the intestine of the house sparrow Passer domesticus to hydrophilic compounds, we applied a pharmacokinetic technique to measure in vivo absorption of two carbohydrate probes, l-arabinose and d-mannitol. Probes were fed or injected, and blood and excreta were subsequently collected and analyzed by gas chromatography/mass spectrometry. Following injection, plasma probe concentration decreased in a log-linear fashion, implying single-compartment, first-order kinetics. Following oral administration, plasma probe concentrations increased, reached a maximum at 10 min and then decreased in log-linear fashion. Mannitol and arabinose absorption were calculated from the areas under the post-absorption plasma curve and the respective distribution spaces and elimination constants. The amounts absorbed increased linearly with the concentration administered (range 1-1000 mmol x l(-1)), implying a passive process. The mouth-to-cloaca retention time of digesta, measured using the non-absorbable compound potassium ferrocyanide, was independent of probe concentration. On average, 69% of the oral dose of probe was absorbed and this was independent of the concentration of probe administered. This paper supports an earlier report of substantial passive glucose absorption in house sparrows and offers a method to study the extent of hydrophilic solute absorption, which has importance for future research in areas as diverse as biomedical, ecological and evolutionary physiology.

Nutritional implications and metabolizable energy value of D-xylose and L-arabinose in chicks.

An experiment was conducted to examine the effects of graded levels (2.5, 5.0, 7.5, 10.0, and 15.0%) of dietary D-xylose or L-arabinose on chick performance. As reference, D-glucose was included in the experiment. A second experiment was performed to determine the AMEn of D-xylose and L-arabinose. Results of Experiment 1 showed a significant linear decrease (P less than .05) in weight gain and efficiency of feed utilization when the dietary level of either D-xylose or L-arabinose was increased. The same was true for daily feed intake of the D-xylose treatments. Water intake was linearly (P less than .05) increased as dietary level of both pentose sugars increased, and, as a result, dry matter content of the droppings decreased. Results of Experiment 2 showed that the AMEn value of either pentose sugar was dose related. The AMEn values for D-xylose at 5 and 10% dietary inclusion were 2,660 and 2,020 kcal/kg, respectively. Those for L-arabinose at these inclusion levels were 2,300 and 1,360 kcal/kg, respectively. Feeding equal dietary levels of either pentose sugar resulted in higher concentrations of xylose than of arabinose in blood plasma. Concentration of glucose in blood was not affected by feeding either D-xylose or L-arabinose. Cecal length and weight were markedly increased by feeding L-arabinose and intermediately by D-xylose.

Serum levels of arabinitol in the detection of invasive candidiasis in animals and humans.

Arabinitol is a pentitol generated in large quantitites by several species of Candida, including Candida albicans. The level of arabinitol in the sera of infected animals and humans was determined by gas-liquid chromatography of an acetone extract of the serum. Experimentally infected mice with pyelonephritis due to C. albicans had elevated levels of arabinitol; rabbits with pyelonephritis did not have elevated levels, nor did rabbits with catheter-induce cystitis, but rabbits with endocarditis developed elevated levels of arabinitol shortly before death. A prospective study in patients clinically suspected of having invasive candidiasis failed to show elevated levels of arabinitol in most. Mice and patients not colonized or infected with yeasts but with renal failure had high serum levels of arabinitol. The data indicate that an elevated level of arabinitol in the serum of a patient without renal disease is suggestive of invasive candidiasis, but normal serum levels do not contradict the diagnosis.

General and transport properties of hypotonic and isotonic preparations of resealed erythrocyte ghosts.

Resealed human erythrocyte ghosts are regarded as valuable tools for the study of membrane properties. In order to investigate to what extent preparation procedures affect the yield of ghosts, their general properties, and their permeability, ghosts prepared by lysis at low (hypotonic media) and high (isotonic media) ionic strength were compared with each other and with native erythrocytes. For isotonic lysis, cells were either subjected to dielectric breakdown or suspended in isotonic NH4Cl solutions. In spite of very different characteristics of the lysis and the resealing process in the three types of preparations, the resulting ghosts do not differ in a number of features except for somewhat varying yields and for properties resulting from the mode of lysis. Specific transport properties, as characterized by the mediated fluxes of m-erythritol, L-arabinose, L-lactate, and sulfate, proved to be unaltered with a few unsystematic exceptions. The simple nonmediated fluxes of all these permeants, as measured in the presence of inhibitors, however, were enhanced between 1.5- and 4-fold, indicating a somewhat increased ground permeability (of the lipid domain) in all ghost membranes.

Quantification of arabinitol in serum by selected ion monitoring as a diagnostic technique in invasive candidiasis.

D-Arabinitol was identified by mass spectrometry as a metabolite of Candida albicans and Candida tropicalis. For quantification, serum was deproteinized with acetone, the supernatant was evaporated to dryness, the silyl derivative was formed, and a portion was injected into a combined gas chromatograph-mass spectrometer system. Erythritol or 2-deoxy-galactitol was the internal standard. The protonated molecular ions, obtained in chemical ionization with isobutane, were monitored. For 39 normal subjects the mean endogenous arabinitol concentration was 0.52 microgram/ml (standard deviation, +/- 0.34). An increment of 0.2 microgram of arabinitol per ml could be quantified. Of 11 cases with diagnosed invasive candidiasis, 9 had arabinitol levels > 1.2 microgram/ml (8 microM) in the range of 1.2 to 25.0 micrograms/ml; the remaining 2 cases had levels in the normal range. Six cases of diagnosed colonized candidiasis showed normal arabinitol levels.

Dual effect of membrane cholesterol on simple and mediated transport processes in human erythrocytes.

The influence of cholesterol on simple and facilitated transport processes across the membrane of intact human erythrocytes was studied after graded depletion or enrichment of membrane cholesterol by incubation of the cells in phospholipid or phospholipid/cholesterol suspensions. 1. The carrier-mediated transfer of L-lactate and of L-arabinose proved to be enhanced in this effect. In contrast, the self-exchange of SO4(2-), mediated by the inorganic anion-exchange system, and the simple diffusion of erythritol via the lipid phase of the membrane are inhibited by cholesterol. 2. Reversibility of these two opposite effects of cholesterol was demonstrated by measurements on cells depleted again after cholesterol enrichment and enriched again after previous depletion. 3. Certain phospholipids used for preparing the lipid dispersions that are required for cholesterol variation have effects on permeability of their own, due, for example, to traces of contaminants. A discrimination of such artifacts due, for example, to traces of contaminants. A discrimination of such artifacts from the effects of cholesterol is only possible by demonstrating reversibility. 4. The opposite effects of cholesterol on various facilitated transfer processes, which have a correlation in the opposite effects of other modifications of the membrane lipid phase (Deuticke, B., Grunze, M. and Haest, C.W.M. (1979) Alfred Benzon Symposium 14, Munksgaard, Copenhagen, in the press), are indicative of different types of lipid-protein interaction in the erythrocyte membrane.

Studies on antitumor activity of prumycin. II. Studies on distribution and excretion of prumycin.

Tissue distribution, excretion and metabolism of prumycin in normal mice and rats were studied by microbiological assay. Following the injection of prumycin into mice, high activity was detected and continued for 24 hours in the kidney, and the activity was also high in the skin, uterus, bone, liver, lung and stomach in this order. But concentration in the brain, heart, spleen and testis were too low to detect even 5 minutes after the injection. Prumycin was not inactivated by a variety of tissue homogenates in vitro. Therefore, inability to detect activity of prumycin in the spleen and testis appears to result from poor distribution rather than inactivation by these organs. About 70% of injected prumycin was excreted into rat urine in 24 hours but it was not detectable in feces. When prumycin was injected intravenously into dogs at the dose over 10 mg/kg, vomiting was observed in all animals, and LD50 was about 50 mg/kg.

Candidiasis: detection by gas-liquid chromatography of D-arabinitol, a fungal metabolite, in human serum.

D-Arabinitol was identified as a major metabolite of Candida species in human subjects. Gas-liquid chromatography was used to measure the concentration of D-arabinitol in serum. The study included subjects who were healthy and cancer patients who had proven invasive candidiasis or were colonized with Candida. D-Arabinitol concentrations greater than 1.0 microgram per milliliter were found in serum from patients with invasive infection. This technique may prove valuable in the diagnosis of invasive candidiasis.

Influence of enzymatic phospholipid cleavage on the permeability of the erythrocyte membrane. II. Protein-mediated transfer of monosaccharides and anions.

In order to investigate the influence of membrane lipids on transport via the protein domain of the erythrocyte membrane, a number of facilitated diffusion processes was studied by tracer flux techniques in whole cells after cleavage of up to 65% of the phosphatidylcholine or the sphingomyelin by phospholipase A2 from Naja naja or bee venom, or by sphingomyelinase, respectively. The mediated fluxes of L-arabinose, which is transported by the glucose carrier, and of L-lactate, which uses a specific monocarboxylate carrier, were markedly inhibited by cleavage of either phosphatidylcholine or sphingomyelin. These phospholipid dependencies are in line with earlier data on cholesterol dependencies (Deuticke, B. (1977) Rev. Physiol. Biochem. Pharmacol. 78, 1-97). They can only in part be explained by changes of membrane fluidity. More specific interactions of the degradation products with the carrier proteins seem also to play a role. Sulfate and oxalate transfer, which proceed via the inorganic anion-exchange system, are essentially unaffected by cleavage of phosphatidylcholine and less sensitive to sphingomyelin cleavage than the two other processes. This also agrees with earlier data on cholesterol independency of sulfate transfer. The inorganic anion-exchange protein thus seems to be less dependent on the surrounding lipids in its conformation and its mode of action than the two other carriers.

The interaction of 3-deoxy-3-fluoro-D-glucose with the hexose-transport system of the human erythrocyte.

1. By using an optical method the kinetic parameters of hexose transport across the human erythrocyte membrane were determined for several sugars. The series of half-saturated constants is as follows: 3-deoxy-3-fluoro-d-glucose = 3-O-methyl-d-glucose