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PubMed1995

In vivo effects of glucosamine on insulin secretion and insulin sensitivity in the rat: possible relevance to the maladaptive responses to chronic hyperglycaemia.

We tested the hypothesis that glucosamine, a putative activator of glucose toxicity in vitro through acceleration of the hexosamine pathway, may determine in vivo the two key features of glucose toxicity in diabetes, namely, peripheral insulin resistance and decreased insulin secretion. Two groups of awake rats were studied either with intraarterial administration of glucosamine (5 mumol.kg-1.min-1) or saline. Insulin secretion was determined after arginine, glucose (hyperglycaemic clamp), and arginine/glucose infusions, while insulin-mediated glucose metabolism was assessed by the euglycaemic hyperinsulinaemic clamp in combination with [3-3H]-glucose infusion. Glucosamine had no effects on arginine-induced insulin secretion both at euglycaemia and hyperglycaemia, but significantly (40-50%) impaired glucose-induced insulin secretion (both first and second phases). During euglycaemic hyperinsulinaemic clamp studies, glucosamine decreased glucose uptake by approximately 30%, affecting glycolysis (estimated from 3H2O rate of appearance) and muscle glycogen synthesis (calculated from accumulation of [3H]-glucosyl units in muscle glycogen) to a similar extent. Muscle glucose 6-phosphate concentration was markedly reduced in the glucosamine-infused rats, suggesting an impairment in glucose transport/phosphorylation. Therefore, an increase in hexosamine metabolism in vivo: 1) inhibits glucose-induced insulin secretion, and 2) reduces insulin stimulation of both glycolysis and glycogen synthesis, thereby mimicking in normal rats the major alterations due to glucose toxicity in diabetes.

Animals↗

PubMed1982

Anderson-Fabry's disease: neuropathological and neurochemical investigation.

A clinical, neuropathological and neurochemical study of a case of Anderson-Fabry's disease is described. The clinical course mainly consisted of repeated ictus with major involvement of the CNS. The neuropathological examination is dominated by severe alterations in the cerebral vessels due to glycolipid deposits on the walls, with reduction or occlusion of the lumen. This is correlated with secondary ischaemic foci scattered throughout the cortex as well as through the white matter. In addition, the cells of the cerebral cortex, thalamus, basal ganglia, amygdala, cerebellar and olivary nuclei show a marked accumulation of lipofuscin. Biochemical examination reveals a threefold increase in galactolipids due to the specific alpha-galactosidase deficiency. Cholesterol is reduced secondarily to ischaemic myelin damage. Glycosaminoglycans uronic acid is increased in cytosol and membrane-bound fractions which could be related to reactive gliosis. Glycoprotein sugars show a decrease in N-acetyl-neuraminic acid and fucose as well as an increase in hexosamines and hexoses in membrane-bound fraction, while in cytosol fraction all sugars are increased. This suggests that the alpha-galactosidase deficiency can alter not only the glycolipid but also the glycoprotein metabolism, resulting in a higher presence of hexosamines and hexoses-rich glycoproteins.

Amygdala↗

PubMed1977

Circular dichroism of human urinary Tamm-Horsfall glycoprotein.

Human urinary Tamm-Horsfall glycoprotein, which contains 28% carbohydrate, has a monomeric molecular weight of about 80,000 but is isolated from urine in the form of intertwining helical suprastructures with molecular weights greater than 10(7). The native glycoprotein was dissociated and denatured with 6 M guanidinium chloride and was subsequently renatured by dialysis against a Tris-HCl buffer. Using sedimetation equilibrium, the renatured glycoprotein was characterized by a Mw cell of 256,800 and a Mz cell of 356,000. The ratio, Mz/Mw, of 1.39 indicates some polydispersity with regard to molecular size. There was no evidence of helical suprastructures in the renatured glycoprotein as judged by electron microscopy. Ca2+ concentrations of up to 50 mM failed to precipitate the renatured glycoprotein; in contrast, the native glycoprotein is precipitated by Ca2+ concentrations between 5-10 mM. The circular dichroic spectrum of renatured Tamm-Horsfall glycoprotein was obtained, resolved, and tentative band assignments made. The spectrum, which is quite similar to that of native Tamm-Horsfall glycoprotein, exhibited negative extrema at 269 nm (due in large part to disulfides and tyrosines) and at 215 nm (due to protein beta-structure and the N-acetylated hexosamines). The alpha-helical content of the glycoprotein was estimated to be no more than 10% and the amount of beta-structure to be about 33%; these values were not affected by the presence of Ca2+ (1 mM). A glcopeptide fraction (ca. 90% carbohydrate), prepared by extensive pronase digestion of the reduced, S-carboxymethylated glycoprotein, exhibited an ellipticity extremum at 212 nm of + 4,750 deg-cm2/dmole, referred to the concentration of (N-acetylated) hexosamines and neuraminic acid.

Carbohydrates↗

PubMed1976

Comparison of pancreatic dysfunction in chronic alcoholic pancreatitis and chronic gallstone pancreatitis.

Comparative assessments of the endocrine and exocrine functions of the pancreas associated with gallstone pancreatitis or alcoholic pancreatitis were performed in a series of 86 patients, 20 with cholelithiasis, 12 with chronic alcoholism, 24 with chronic gallstone pancreatitis and 30 with chronic alcoholic pancreatitis and 32 healthy subjects were served as controls. The patients with cholelithiasis showed exocrine hypersecretion of the pancreas. In the patients with gallstone pancreatitis, all the assessed parameters of exocrine function were depressed. On the other hand, no pancreatic exocrine dysfunction was dispalyed in cases with chronic alcoholism. In the non-calcifying alcoholic pancreatitis, both the volume output and the the maximum concentration and output of bicarbonate were diminished but depression in amylase output was not seen. All these parameters were lowered in patients with calcifying pancreatitis. Elevation of hexosamine concentration in the pancreatic juice was evident in alcoholic pancreatitis as compared with gallstone pancreatitis, being particularly prominent in cases of non-calcifying pancreatitis. Patients with alcoholic pancreatitis were observed to secrete viscous pancreatic juice richer in amylase and hexosamine content, than those in the patients with gallstone pancreatitis. Endocrine dysfunction of the pancreas is more frequent and intense in alcoholic pancreatitis than in gallstone pancreatitis.

Alcoholism↗

PubMed2002

Dietary fatty acid composition during pregnancy and lactation in the rat programs growth and glucose metabolism in the offspring.

AIMS/HYPOTHESIS: We investigated of the effects of fatty acid composition of the maternal diet on fetal and postnatal growth, morphology of the pancreas and glucose metabolism and muscle hexosamine concentrations in the adult offspring of rats. METHODS: High-fat diets enriched with either saturated or unsaturated fatty acids were fed to female adult rats 2 weeks before mating until the end of the weaning period. After weaning, the offspring was maintained on a diet with a balanced fatty acid content. At 3 months of age, pancreatic Langerhans islet size and number were assessed by morphometric analysis and oral glucose tolerance tests (OGTT) were carried out. RESULTS: The unsaturated fatty acid diet showed lower birth weight and reduced postnatal weight gain. Furthermore, this group showed increased pancreatic islet numbers without affected glucose tolerance at the age of 12 weeks. The offspring of the saturated fatty acid diet group showed a reduced number of large pancreatic islets. Moreover, a faster and higher insulin response was observed after an oral glucose load in these animals. Muscle hexosamine concentrations were not different between groups. CONCLUSION/INTERPRETATION: Maternal diets enriched with either saturated fatty acids or unsaturated fatty acids had opposite effects on pancreatic islet development in rat offspring, with consequences for the insulin response at 12 weeks of age. Therefore, maternal dietary fatty acid composition plays a role in programming growth, pancreatic development and glucose metabolism in the offspring.

Animals↗

PubMed1997

UDP-N-acetylglucosamine transferase and glutamine: fructose 6-phosphate amidotransferase activities in insulin-sensitive tissues.

Glutamine:fructose 6-phosphate amidotransferase (GFA) is rate-limiting for hexosamine biosynthesis, while a UDP-GlcNAc beta-N-acetylglucosaminyltransferase (O-GlcNAc transferase) catalyses final O-linked attachment of GlcNAc to serine and threonine residues on intracellular proteins. Increased activity of the hexosamine pathway is a putative mediator of glucose-induced insulin resistance but the mechanisms are unclear. We determined whether O-GlcNAc transferase is found in insulin-sensitive tissues and compared its activity to that of GFA in rat tissues. We also determined whether non-insulin-dependent diabetes mellitus (NIDDM) or acute hyperinsulinaemia alters O-GlcNAc transferase activity in human skeletal muscle. O-GlcNAc transferase was measured using 3H-UDP-GlcNAc and a synthetic cationic peptide substrate containing serine and threonine residues, and GFA was determined by measuring a fluorescent derivative of GlcN6P by HPLC. O-GlcNAc transferase activities were 2-4 fold higher in skeletal muscles and the heart than in the liver, which had the lowest activity, while GFA activity was 14-36-fold higher in submandibular gland and 5-18 fold higher in the liver than in skeletal muscles or the heart. In patients with NIDDM (n = 11), basal O-GlcNAc transferase in skeletal muscle averaged 3.8 +/- 0.3 nmol/mg.min, which was not different from that in normal subjects (3.3 +/- 0.4 nmol/mg.min). A 180-min intravenous insulin infusion (40 mU/m2.min) did not change muscle O-GlcNAc transferase activity in either group. We conclude that O-GlcNAc transferase is widely distributed in insulin-sensitive tissues in the rat and is also found in human skeletal muscle. These findings suggest the possibility that O-linked glycosylation of intracellular proteins is involved in mediating glucose toxicity. O-GlcNAc transferase does not, however, appear to be regulated by either NIDDM or acute hyperinsulinaemia, suggesting that mass action effects determine the extent of O-linked glycosylation under hyperglycaemic conditions.

Adipose Tissue↗

PubMed2007

Changes in glycoprotein components in streptozotocin--nicotinamide induced type 2 diabetes: influence of tetrahydrocurcumin from Curcuma longa.

Curcuma longa (Zingiberaceae) has been used traditionally as antidiabetic, and has been proven scientifically to possess high antioxidant activity and anticancer properties. The active components of Curcuma longa such as curcumin and tetrahydrocurcumin (THC), a major colourless metabolite of curcumin also possesses antidiabetic, antiinflammatory and antioxidant activity. The ethnopharmacological value of this plant, the effect of THC on glycoproteins was carried out in normal and streptozotocin-nicotiniamide induced type 2 hyperglycaemic rats for 45 days. Glucose, plasma insulin and glycoprotein components in plasma and tissues (hexose, hexosamine, fucose and sialic acid) were determined. Oral administration of THC to diabetic rats showed a decrease in the level of blood glucose and plasma glycoproteins. The levels of plasma insulin and tissue sialic acid were increased where as the levels of tissue hexose, hexosamine and fucose were near normal in diabetic rats treated with THC. The present study indicates that the THC possesses a significant beneficial effect on glycoprotein moiety in addition to its antidiabetic effect. The effect of THC is more prominent than curcumin.

Animals↗

PubMed1986

Analysis by high-performance liquid chromatography of radioactively labeled carbohydrate components of proteoglycans.

Methods were developed for the separation of radioactively labeled carbohydrate components of proteoglycans by isocratic ion-moderated partition HPLC. Neutral sugars were separated after hydrolysis in trifluoroacetic acid with baseline separation between glucose, xylose, galactose, fucose, and mannose. N-Acetylneuraminic acid, N-acetylated hexosamines, glucose, galactose, and xylitol were likewise well separated from each other under isocratic elution conditions. Glucuronic acid, iduronic acid, and their lactones were separated after hydrolysis in formic acid and sulfuric acid. Glucosamine, galactosamine, galactosaminitol, and glucosaminitol were separated by HPLC on a cation exchanger with neutral buffer after hydrolysis in hydrochloric acid. The separation techniques also proved useful in fractionation of exoglycosidase digests of O- and N-linked oligosaccharides. Separations of aldoses, hexosamines, and uronic acids were adapted to sensitive photometric detection.

Carbohydrates↗

PubMed1990

Quantitative analysis of N-sulfated, N-acetylated, and unsubstituted glucosamine amino groups in heparin and related polysaccharides.

A colorimetric procedure for quantitative determination of free and substituted glucosamine amino groups in heparin and related polysaccharides has been developed. The total content of hexosamine amino groups is determined by a modification of the method of Tsuji et al. (1969, Chem. Pharm. Bull. 17, 1505-1510); this method involves acid hydrolysis under conditions effecting complete removal of N-acetyl and N-sulfate groups, deaminative cleavage with nitrous acid, and colorimetric analysis of the resultant anhydromannose residues by reaction with 3-methyl-2-benzothiazolinone hydrazone (MBTH). N-sulfated glucosamine residues are cleaved selectively by treatment with nitrous acid at pH approximately 1.5 (J. E. Shively, and H.E. Conrad, 1976, Biochemistry 15, 3932-3942) and quantitated by the MBTH reaction. Under carefully controlled conditions, deamination at pH approximately 1.5 is highly specific for N-sulfated glucosamine residues, but an excess of reagent causes some cleavage of residues with unsubstituted amino groups as well. Deaminative cleavage at pH approximately 4.5 results in preferential degradation of unsubstituted glucosamine residues, but some cleavage (5-8%) of N-sulfated residues also occurs. However, analysis of the content of N-sulfated residues by the specific pH 1.5 procedure allows appropriate corrections to be made. From the value for total hexosamine content and the sum of N-sulfated and unsubstituted residues, the content of N-acetylated residues is calculated by difference. The modified deamination procedures, in combination with product analysis by the MBTH reaction, have been applied to several problems commonly encountered in the analysis and characterization of heparin.

Acetylglucosamine↗

PubMed1983

Oligosaccharides released from glycolipids by trifluoroacetolysis can be analyzed by gas chromatography-mass spectrometry.

Carbohydrates are quantitatively released by trifluoroacetolysis of neutral glycosphingolipids that contain 4-sphingenine. During the reaction hydroxyl groups are O-trifluoroacetylated and N-acetyl hexosamines are transamidated to form N-trifluoroacetyl derivatives. Selective removal of O-trifluoroacetyl groups followed by permethylation produces derivatives with properties favorable for analysis by combined gas chromatography/mass spectrometry. Electron impact mass spectra of permethylated N-trifluoroacetylated oligosaccharide alditols are characterized by strong primary and secondary fragments in which a positive charge is localized on the N-trifluoroacetyl hexosamine residue. The method enables rapid separation and identification of components in mixtures of carbohydrate chains from glycosphingolipids containing up to six simple sugars.

Animals↗

PubMed1975

Isolation and partial characterization of two minor glycoproteins from human erythrocyte membranes.

Two minor glycoproteins GP-II and GP-III, were isolated from human erythrocyte membranes and characterized chemically and immunologically. The chemical composition of GP-II and GP-III was similar: GP-II consisted of 81% protein and 19% carbohydrate of which 4.9% was hexose, 5.4% hexosamine and 7.8% sialic acid. GP-III consisted of 76% protein and 24% carbohydrate of which 7.6% was hexose, 7.2% hexosamine and 8.1% sialic acid. The amino acid composition of GP-II and GP-III was also similar. GP-II and GP-III, however, differed in chemical composition from the MN glycoprotein. GP-II and GP-III were associated with the blood group activities Ss, I and A, but not with the MN antigens. GP-III had higher blood group activities per mug of protein than did GP-II. The specific activities for the Ss blood group antigens were increased 3-10-fold by purificantion of GP-III from the aqueous phase of chloroform methanol extracts.

Amino Acids↗

PubMed1976

Isolation and partial characterization of human kidney gangliosides.

1. Eight gangliosides were purified from chloroform/methanol extracts of human kidneys by using modified Folch partition, dialysis, ethanol precipitation, silicic acid column chromatography and preparative thin-layer chromatography. 2. By thin-layer chromatographic behaviour and gas-liquid chromatographic determinations the main gangliosides in human kidney are N-acetylneuraminyllactosylceramide (74% of total) and di-N-acetylneuraminyllactosylceramide (19% of total). 3. Five hexosamine-containing fractions were isolated. Four of them were homogeneous on thin-layer chromatography, and one contained two gangliosides. By gas-liquid chromatography-mass spectrometry it was shown that two gangliosides (together 5% of total) contain glucosamine, and one (1% of total) contains galactosamine. The other of the glucosamine gangliosides contains fucose in addition to the usual sugars found in gangliosides. Of the two remaining hexosamine positive fractions (together 1% of total) one was homogeneous on thin-layer chromatography, the other contained two gangliosides. These two fractions contained both glucosamine and galactosamine. 4. The main long-chain base in all fractions was sphingosine.

Chromatography, Gas↗

PubMed1991

Interaction of a high-affinity heparin subfraction with low-density lipoprotein stimulates cholesteryl ester accumulation in mouse macrophages.

A high-affinity heparin subfraction accounting for 8% of whole heparin from bovine lung was isolated by low-density lipoprotein (LDL)-affinity chromatography. When compared to whole heparin, the high-affinity subfraction was relatively higher in molecular weight (11,000 vs. 17,000) and contained more iduronyl sulfate as hexuronic acid (76% vs. 86%), N-sulfate ester (0.75 vs. 0.96 mol/mol hexosamine), and O-sulfate ester (1.51 vs. 1.68 mol/mol hexosamine). Although both heparin preparations formed insoluble complexes with LDL quantitatively in the presence of 30 mM Ca2+, the concentrations of NaCl required for 50% reduction in maximal insoluble complex formation was markedly higher with high-affinity subfraction (0.55 M vs. 0.04 M). When compared to complex of 125I-LDL and whole heparin (H-125I-LDL), complex of 125I-LDL and high-affinity heparin subfraction (HAH-125I-LDL) produced marked increase in the degradation of lipoproteins by macrophages (7-fold vs. 1.4-fold over native LDL, after 5 h incubation) as well as cellular cholesteryl ester synthesis (16.7-fold vs. 2.2-fold over native LDL, after 18 h incubation) and content (36-fold vs. 2.7-fold over native LDL, after 48 h incubation). After a 5 h incubation, macrophages accumulated 2.3-fold more cell-associated radioactivity from HAH-125I-LDL complex than from [125I]acetyl-LDL. While unlabeled HAH-LDL complex produced a dose-dependent inhibition of the degradation of labeled complex, native unlabeled LDL did not elicit any effect even at a 20-fold excess concentration. Unlabeled particulate LDL aggregate competed for 33% of degradation of labeled complex; however, cytochalasin D, known inhibitor of phagocytosis, did not effectively inhibit the degradation of labeled complex. Unlabeled acetyl-LDL produced a partial (33%) inhibition of the degradation of labeled complex. These results indicate that (1) the interaction of high-affinity heparin subfraction with LDL leads to scavenger receptor mediated endocytosis of the lipoprotein, and stimulation of cholesteryl ester synthesis and accumulation in the macrophages; and (2) with respect to macrophage recognition and uptake, HAH-LDL complex was similar but not identical to acetyl-LDL. These observations may have implications for atherogenesis, because both mast cells and endothelial cells can synthesize heparin in the arterial wall.

Animals↗

PubMed1977

The effects of thromboxane B2 and 6-ketoprostaglandin F1alpha on cultured fibroblasts.

The effects of thromboxane B2 and 6-ketoprostaglandin F1alpha on the synthesis of DNA, RNA and hexosamine-containing substances were studied. Thromboxane B2 (1 microgram/ml) added to cultures in the stationary phase caused the initiation of DNA synthesis and cell proliferation in a small proportion of cells. The same amount of thromboxane B2 also increased [3H]uridine incorporation into acid-insoluble fraction by 50% in 24 h, and stimulated the production of hexosamine-containing substances 2.5 fold over the control during the first 6 h. On the other hand, 6-ketoprostaglandin F1alpha was essentially inactive on these indexes except slight stimulation of DNA synthesis.

Cell Division↗

PubMed1984

The metabolism of galactose in the human gastric mucous membrane.

After incubating pieces of human gastric mucous membrane with radioactive galactose, labeled metabolites of glycolysis (FDP,PEP,pyruvate):hexose and hexosamine intermediates in glycoconjugate biosynthesis (gal-1P, UDP-gal,acetylated hexosamines, and their phosphate esters), amino acids (glycine, alanine, and serine), and oxoglutarate as a metabolite of the citric acid cycle were isolated from the acid-soluble fraction. These results suggest that galactose in the human gastric mucous membrane is epimerized to glucose and metabolized in the glycolytic pathway together with oxidation in the citric acid cycle and in the direction of glycoconjugate biosynthesis.

Chromatography, Ion Exchange↗

PubMed1983

The carbohydrate units of asialo-ovomucoid: their heterogeneity and enzymic degradation.

An ovomucoid variant free from sialic acid has been prepared in a pure state by ion-exchange chromatography on DEAE-cellulose. The purified glycoprotein contained 10-11 residues of mannose, 2-3 residues of galactose, and 21 residues of 2-acetamido-2-deoxyglucose. Glycopeptides have been prepared by exhaustive digestion with Pronase followed by ion-exchange chromatography on Dowex 50 (X2) resin. Three fractions were obtained, all with similar contents of mannose and hexosamine but with various contents of galactose. The sugar-aspartic acid ratios indicated that all of the fractions were heterogeneous, the major fraction having mannose-galactose-hexosamine-aspartic acid ratios of 2.6:0.5:5.8:1.0. Cleavage of asialo-ovomucoid with cyanogen bromide and proteolytic digestion of the isolated fragments gave two heterogeneous glycopeptide fractions of similar composition. Both asialo-ovomucoid and the principal glycopeptide fraction were degraded with beta-D-galactosidase, alpha-D-mannosidase, and beta-N-acetylglucosaminidase singly and in sequence. Removal of much of the carbohydrate from asialo-ovomucoid had no appreciable effect on its anti-tryptic activity. By sequential degradation of the glycopeptide, a pentasaccharide core alpha-D-Man-[alpha-D-Man]-beta-D-Man-beta-D-GlcNAc-beta-D-GlcNAc-Asn was obtained. Other structural features revealed by enzymic degradation are discussed.

Animals↗

PubMed1978

Connective tissue components in normal and atherosclerotic human coronary arteries.

Human coronary arteries with various degrees of atherosclerosis were analyzed for the concentration of different types of glycosaminoglycans (GAGs). The changes in GAGs were considered against the background of macroscopic atherosclerosis, and the concentration of glycoprotein-bound hexosamines, collagen, calcium and cholesterol. The concentration of calcium was increased and that of hyaluronic acid decreased even in mildly atherosclerotic coronary arteries. The additional changes in advanced atherosclerosis included the increase of collagen and dermatan sulphate and the decrease of heparan sulphate. Cholesterol was increased in mild, and even further in advanced, atheroslcerosis. The concentrations of chondroitin sulphates and glycoprotein-bound hexosamines were not significantly affected by atherosclerosis.

Chondroitin Sulfates↗

PubMed1987

Structural features and antigenic properties of carbohydrate-containing components of Trypanosoma conorhini.

Aqueous and phenolic extracts of Trypanosoma conorhini were fractionated and high molecular weight, carbohydrate-rich fractions obtained. Their antigenic characteristics, reactivity with lectins and partial chemical structure were determined. The major component, the phenolic extract, was electrophoretically diffuse and consisted of 15% protein, 5% phosphorus, hexosamine, and 67% neutral carbohydrate, which contained mannose, galactose, and xylose in a molar ratio of 1.0:1.8:1.8. Chemical analyses and lectin agglutination experiments showed nonreducing end-groups of beta-D-galactopyranose, beta-xylopyranose, and alpha-D-mannopyranose. Phosphate esters occurred, apparently, at O-6 of hexopyranosyl units. Hexosamine was present as nonacetylated units of 2-amino-2-deoxy-alpha-D-glucopyranosyl units that were extremely resistant to acid hydrolysis. On double immunodiffusion tests, the major component gave a precipitation line with rabbit serum against whole cells of Trypanosoma cruzi, suggesting the presence of common antigenic determinant(s) on the cell surface of each trypanosomatid.

Agglutination Tests↗