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PubMed1995

Lipopolysaccharide of Rhodospirillum salinarum 40: structural studies on the core and lipid A region.

The structural elucidation of lipid A of the cell wall lipopolysaccharide (LPS) of Rhodospirillum salinarum 40 by chemical methods and laser desorption mass spectrometry revealed the presence of a mixed lipid A composed of three different 1,4'bisphosphorylated beta (1 --> 6)-linked backbone hexosaminyl-hexosamine disaccharides, i.e. those composed of GlcN --> GlcN, 2,3-diamino-2,3-dideoxy-D-Glc-(DAG --> DAG, and DAG --> GlcN. Lipid A of R. salinarum contained preferentially 3-OH-18:0 and 3-OH-14:0 as amide-linked and cis delta 11-18:1 and c19:0 as ester-linked fatty acids. The mass spectra of the liberated acyl-oxyacyl residues proved the concomitant presence of 3-O-(cis delta 11-18:1)-18:0 and 3-O-(c19:0)-14:0 as the predominating diesters in this mixed lipid A. The glycosidically linked and the ester-linked phosphate groups of the backbone disaccharide were neither substituted by ethanolamine, phosphorylethanolamine, nor by 4-amino-4-deoxy-L-arabinose, in contrast to most of the enterobacterial lipid As. In the core oligosaccharide fraction, a HexA (1 --> 4)HexA(1 --> 5)Kdo-trisaccharide was identified by methylation analysis. The terminal HexA (hexuronic acid) is possibly 4-OMe-GalA, a component described here as an LPS constituent for the first time. LPS of R. salinarum showed a lethality in C57BL/10 ScSN (LPS-responder)-mice) of an order of 10(-1)-10(-2) of that reported for Salmonella abortus equi LPS, and it was also capable of inducing TNF alpha and IL6 in macrophages of C57BL/10ScSN mice.

Animals↗
PubMed1986

Influence of dietary fiber on lipids and aortic composition of vervet monkeys.

A semipurified, cholesterol-free diet containing 40% carbohydrate can produce aortic sudanophilia or aortic atherosclerosis in vervet monkeys (Cercopithecus aethiops pygerethrus) depending on the particular carbohydrate fed. Four groups of vervet monkeys (three males and three females per group) were fed semipurified diets containing lactose. Two of the groups were also fed 15% cellulose (C) or 15% cellulose plus 0.1% cholesterol (CC); the two other groups were fed 15% pectin (P) or 15% pectin plus 0.1% cholesterol (PC). The average serum total cholesterol and low density lipoprotein cholesterol levels over the entire feeding period (mg/dl +/- SEM) were, for C, 156 +/- 14 and 95 +/- 5; for P, 173 +/- 15 and 112 +/- 8; for CC, 187 +/- 27 and 122 +/- 21; and for PC, 155 +/- 11 and 108 +/- 7. Cholesterol levels at autopsy (mg/dl +/- SEM) were, for C, 103 +/- 6; for P, 108 +/- 16; for CC, 92 +/- 9; and for PC, 106 +/- 7. Aortic sudanophilia (percentage of area) was, for C, 5.9 +/- 2.7; for P, 13.5 +/- 9.4; for CC, 5.3 +/- 2.1; and for PC, 21.6 +/- 10.3. Dietary pectin led to more severe sudanophilia (increased by 129% in the absence of cholesterol and by 308% in its presence) than did cellulose. Analysis of aortic glycosaminoglycans (GAG) revealed that dermatan sulfate levels fell in both cholesterol-fed groups, and chondroitin sulfate fell in aortas of group CC. Heparan sulfate levels were unaffected by cholesterol feeding. Hexuronic acid, galactosamine and hexosamine levels were elevated in the pectin-fed monkeys, but levels were unaffected by dietary cholesterol.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Pathogenesis of gastric mucosal damage induced by intraperitoneal administration of gold thioglucose in rats.

Rats injected intraperitoneally with gold thioglucose (GTG,0.3mg/g) revealed hemorrhagic lesions in the gastric mucosa 24h after the injection. However, no morphological changes were found in the central nervous system after the injection. The volume of gastric secretion and acid output increased significantly 24h after the injection (P less than 0.01), and gastric emptying was markedly inhibited 24h post administration (P less than 0.01). There were no changes in either blood flow or hexosamine contents in the gastric mucosa. These results indicated that gastric hemorrhagic lesion was associated with increases in gastric secretion and acid output. No significant changes were found in gastrin contents in either plasma or the gastric mucosa. A subdiaphragmatic vagotomy prior to the GTG injection prevented bleeding in the gastric mucosa and lowered the gastric secretion and acid output. This indicated that the mechanism of action of GTG in producing the gastric lesion might be mediated by the vagus nerve.

Animals↗
PubMed1976

Hormonal control of growth and differentiation of insect tissues cultured in vitro.

This paper reviews the effects of insect hormones on lepidopteran imaginal discs cultured in vitro. Beta-ecdysone showed that RNA and protein synthesis was required for evagination and cuticle deposition. In particular, studies with actinomycin D and cycloheximide (at nontoxic levels) showed that RNA and protein synthesis during the ecdysone-dependent period was essential for subsequent development. These findings support the hypothesis that stimulation of macromolecular synthesis is fundamental to the action of ecdysone on imaginal discs. The influence of beta-ecdysone on chitin synthesis was also examined. Beta-ecdysone stimulated uptake and incorporation of tritiated-glucosamine by cultured P.interpunctella wing discs. Addition of hexosamines to the culture medium had no influence on ecdysone-induced cuticle deposition, but inhibition of glucose-uptake by cytochalasin B prevented the formation of cuticle. The action of ecdysone on particular enzymes in the chitin pathway remains to be elucidated.timulated both evatination and cuticle deposition of wing discs of Plodia interpunctella(Hubner). However, evagination required a shorter exposure to ecdysone than did cuticle deposition. Cuticle deposition was obtained under the following conditions: (a) a 24-hour pulse of beta-ecdysone (0.5-5.0 mug/ml); (b) continuous treatment with 0.2 mug/ml beta-ecdysone; or (c) continuous treatment with 0.5 to 50.0 mug/ml beta-ecdysone in medium conditioned with larval fat body...

Acetylglucosamine↗
PubMedDate not supplied

Fibrinogen Logroño. A new case of congenital dysfibrinogenemia.

An abnormal fibrinogen was discovered in a 9-year-old male subject without history of hemorrhagic diathesis. Coagulation time, prothrombin time and Reptilase time were prolonged. The thrombin time was corrected using increasing concentrations of normal plasma and bovine thrombin; there was a partial correction at pH 6.5 and ionic strength 0.05. A study of the family showed that the mother and a brother of the propositus presented the same abnormalities. Analysis of the purified fibrinogen showed normal fibrinopeptide release and normal levels of sialic acid and hexosamines. However, coagulation index, polymerization of fibrin monomers, isoelectric point and sedimentation coefficient were abnormal. In view of the abnormalities described and by comparison with the data reported in the literature, we believe that this should be considered a new variant of the fibrinogen molecule and we have designated it 'fibrinogen Logroño'.

Blood Coagulation Disorders↗
PubMed1981

Serum glycoproteins in diagnosis and monitoring of patients with large-bowel cancer.

The profile of serum glycoproteins is altered in malignancy with a relative increase in acute phase reactant proteins. A prospective study has been performed to investigate three sugar moieties (hexose, hexosamine and sialic acid) of these glycoproteins in the serum of large-bowel cancer patients as a possible guide to recurrence, and to compare these three variables with carcinoembryonic antigen (CEA). The three variables indicated the presence of colorectal cancer in over 65 per cent of 107 cancer-bearing subjects. Furthermore, the appearance of metastatic disease was associated with abnormalities in these variables in 10 of 11 patients, and appears more accurately reflected than with CEA. However, the three variables and CEA are cumulative in their value for predicting recurrent cancer. Monitoring of acute phase reactant proteins may therefore be of potential clinical benefit for monitoring of colorectal cancer patients at high risk of recurrence.

Carcinoembryonic Antigen↗
PubMed2006

The influence of genetic background on the induction of oxidative stress and impaired insulin secretion in mouse islets.

AIMS/HYPOTHESIS: We determined whether high-glucose-induced beta cell dysfunction is associated with oxidative stress in the DBA/2 mouse, a mouse strain susceptible to islet failure. MATERIALS AND METHODS: Glucose- and non-glucose-mediated insulin secretion from the islets of DBA/2 and control C57BL/6 mice was determined following a 48-h exposure to high glucose. Flux via the hexosamine biosynthesis pathway was assessed by determining O-glycosylated protein levels. Oxidative stress was determined by measuring hydrogen peroxide levels and the expression of anti-oxidant enzymes. RESULTS: Exposure to high glucose levels impaired glucose-stimulated insulin secretion in DBA/2 islets but not C57BL/6 islets, and this was associated with reduced islet insulin content and lower ATP levels than in C57BL/6 islets. Exposure of islets to glucosamine for 48 h mimicked the effects of high glucose on insulin secretion in the DBA/2 islets. High glucose exposure elevated O-glycosylated proteins; however, this occurred in islets from both strains, excluding a role for O-glycosylation in the impairment of DBA/2 insulin secretion. Additionally, both glucosamine and high glucose caused an increase in hydrogen peroxide in DBA/2 islets but not in C57BL/6 islets, an effect prevented by the antioxidant N-acetyl-L: -cysteine. Interestingly, while glutathione peroxidase and catalase expression was comparable between the two strains, the antioxidant enzyme manganese superoxide dismutase, which converts superoxide to hydrogen peroxide, was increased in DBA/2 islets, possibly explaining the increase in hydrogen peroxide levels. CONCLUSIONS/INTERPRETATION: Chronic high glucose culture caused an impairment in glucose-stimulated insulin secretion in DBA/2 islets, which have a genetic predisposition to failure, and this may be the result of oxidative stress.

Adenosine Triphosphate↗
PubMed1999

Nutritional regulation of leptin in humans.

Although leptin was first discussed as an "adipostat" that regulated food intake in accordance with triglyceride stores, it has become clear that leptin's role is much more complex and that a great many unanswered questions persist. Human studies have not shown that serum leptin concentrations can be changed rapidly by meals. Insulin seems to have a modest but immediate effect in attenuating the morning nadir of serum leptin as well as a greater effect manifested after 4-6 h. These changes in serum leptin, like the decreases that occur with fasting, are not accompanied by corresponding changes in adipose leptin mRNA, suggesting regulation by translational control or changes in the rate of leptin degradation, secretion or clearance. There is convincing evidence that insulin increases leptin synthesis and secretion, probably through an insulin-dependent effect on glucose metabolism. This effect of insulin is possibly mediated by the hexosamine pathway. What adipocytes seem to be communicating to the brain is not how much triglyceride they contain but whether they are currently synthesizing or hydrolysing triglyceride. Confounding many studies is the problem of leptin's diurnal rhythm. Because many studies only measured leptin during its morning nadir or examined the effects of insulin or specific nutrients provided after an overnight fast, important information on regulation may have been lost.

Appetite↗
PubMed2000

Increased O-GlcNAc transferase in pancreas of rats with streptozotocin-induced diabetes.

AIMS/HYPOTHESIS: Streptozotocin (STZ), a chemically reactive analogue of N-acetylglucosamine, induces necrosis of the beta cells, resulting in diabetes mellitus. Glucose-induced insulin resistance is mediated by increased activity of the hexosamine pathway. We aimed to examine the regulation of O-GlcNAc transferase expression and activity in the normal and streptozotocin diabetic pancreas. METHODS: Rats were made diabetic by an injection of streptozotocin (65 mg/kg). The expression of O-GlcNAc transferase protein was examined by immunoblot analysis. Activity of O-GlcNAc transferase was assayed by the incorporation of [3H]GlcNAc into the synthetic peptide. Localization of O-GlcNAc transferase was done by immunohistochemistry. The change of O-GlcNAc modification of proteins was examined by immunoblot analysis. RESULTS: In the STZ-induced diabetic pancreas, a severe loss of beta cells was observed, whereas alpha cells had increased in number. The diabetic pancreas showed an increase in the expression of O-GlcNAc transferase at the protein level and the O-GlcNAc transferase activity in it was increased significantly (p < 0.05). An increase in the immunostaining intensity in the cytoplasm of islet beta cells was also observed in the diabetic pancreas, whereas exocrine cells and islet cells other than beta cells showed little change in immunostaining intensity. The pancreas of STZ-diabetic rats showed a 3.1-fold increase in total cellular O-GlcNAc-modified proteins. CONCLUSION/INTERPRETATION: These findings indicate that O-GlcNAc transferase plays an important part in the modulation of O-GlcNAc concentrations in the pancreas and suggest that the increase in O-GlcNAc modification of the proteins correlates closely with diabetes.

Animals↗
PubMed2001

Presence of glutamine:fructose-6-phosphate amidotransferase for glucosamine-6-phosphate synthesis in endothelial cells: effects of hyperglycaemia and glutamine.

AIMS/HYPOTHESIS: Recent studies show that glucosamine infusion impairs endothelium-dependent blood flow in normoglycaemic rats. The pathophysiological relevance of this finding, however, depends on whether de novo glucosamine synthesis occurs in endothelial cells. The aim of this study was to test the hypothesis of whether glutamine:fructose-6-phosphate amidotransferase (the first and key regulatory enzyme in hexosamine synthesis) is present for endothelial glucosamine synthesis. METHODS: Bovine venular, bovine aortic, human microvascular, human umbilical vein, and rat coronary microvascular endothelial cells were used to measure glutamine:fructose-6-phosphate amidotransferase activity. To determine glucosamine-6-phosphate synthesis in intact cells, they were incubated for 1 h in Krebs bicarbonate buffer containing 5, 15 or 30 mmol/l [U-14C]glucose and 0.5, 2 or 4 mmol/l glutamine. The [14C]Glucosamine-6-phosphate and its end products ([14C]UDP-N-acetylglucosamine and [14C]UDP-Nacetylgalactosamine) were separated by HPLC. RESULTS: There were high glutamine:fructose-6-phosphate amidotransferase activities in all endothelial cells studied. Exposure of cells to 15 to 30 mmol/l glucose or 2 to 4 mmol/l glutamine increased enzyme activity. Glucosamine-6-phosphate, UDP-N-acetylglucosamine and UDP-N-acetylgalactosamine syntheses increased with increasing extracellular concentrations of glucose from 5 to 30 mmol/l or of glutamine from 0.5 to 4 mmol/l. CONCLUSION/INTERPRETATION: Our results show the presence of glutamine:fructose-6-phosphate amidotransferase for de novo glucosamine synthesis in endothelial cells and the modulation of this pathway by hyperglycaemia and glutamine. As glucosamine inhibits endothelial nitric oxide synthesis, these findings could have important implications for impaired endothelium-dependent relaxation and vascular dysfunction in diabetes mellitus.

Animals↗
PubMed2001

15th Golgi lecture: from hyperglycaemia to the dysregulation of vascular remodelling in diabetes.

Hyperglycaemia has been shown to play a central part in diabetic vascular disease, which is also influenced by individual background. Hyperglycaemia initiates the pathogenetic sequence through a series of interrelated biochemical abnormalities, including increased flux through the polyol and hexosamine pathways, oxidative stress, AGE formation and protein kinase C activation. These abnormalities are capable of modifying the function of resident and non-resident vascular cells by changing their production pattern of several autocrine and paracrine factors, including growth, vasoactive and coagulation factors and adhesion molecules. These mediators profoundly impair the physiologic turnover of the vessel wall, thus leading to an abnormal process of vascular remodelling, with alterations in cell and matrix turnover and contacts, vascular tone and permeability and coagulation pattern. This process has distinct features depending on the target tissue. The hallmark of nephropathy is an abnormal accumulation of extracellular matrix within the mesangium, sustained by an upregulation of TGF-beta, possibly triggered by a local activation of the renin-angiotensin system. The central pathological lesion in retinopathy is retinal ischaemia due to the formation of acellular capillaries. The resulting vascular endothelial growth factor-dependent neovascularization is a detrimental phenomenon leading to the formation of noncompetent vessels. Conversely, in macrovascular disease, arterial occlusion resulting from plaque formation with superimposed thrombosis elicits an angiogenic response which is impaired, but generates competent vessels, potentially compensating for reduced flow. Thus, upstream interventions interrupting the pathogenetic sequence at the level of hyperglycaemia (and related biochemical events) are the most effective, whereas downstream interventions should be targeted to the tissue affected.

Animals↗
PubMed2006

Effect of +36T>C in intron 1 on the glutamine: fructose-6-phosphate amidotransferase 1 gene and its contribution to type 2 diabetes in different populations.

Glutamine: fructose-6-phosphate amidotransferase 1 (GFPT1) acts as a rate-limiting enzyme in the hexosamine biosynthetic pathway, which is an alternative branch of glucose metabolism. To evaluate GFPT1 as a susceptibility gene to type 2 diabetes, we surveyed the polymorphisms related with the gene function of GFPT1 and assessed its contribution to type 2 diabetes with a case-control association study. Screening of the 5'-flanking and all coding regions of GFPT1 revealed eight polymorphisms, one in the 5'-flanking region, one synonymous polymorphism in exon 8, five in introns and one in 3'-UTR, but no mis-sense or non-sense polymorphism. With in silico simulation, a putative promoter region was apparently predicted between 1 kb upstream and 1 kb downstream of the start codon. In this region, +36T>C polymorphism was located on the GC box sequence in intron 1, and its functional effect on promoter activity was confirmed by luciferase reporter assay, introducing a new functional polymorphism of the GFPT1 gene. To examine its association with type 2 diabetes, we analyzed 2,763 Japanese (1,461 controls and 1,302 cases) and 330 Caucasians (190 controls and 140 cases). One possible association of +36T>C was observed in Caucasians, but no association of polymorphisms including +36T>C in intron 1 or haplotypes was observed in Japanese. Although we could not completely rule out a contribution to specific sub-groups or other populations, genetic variation of GFPT1 is unlikely to have a major role in the susceptibility to type 2 diabetes in Japanese.

5' Flanking Region↗
PubMed2001

Identification of GFAT1-L, a novel splice variant of human glutamine: fructose-6-phosphate amidotransferase (GFAT1) that is expressed abundantly in skeletal muscle.

Glutamine:fructose-6-phosphate amidotransferase (GFAT1) is the rate-limiting enzyme in the hexosamine biosynthetic pathway, which plays an important role in hyperglycemia-induced insulin resistance. To evaluate the role of GFAT1 expression, we analyzed the expression profiles of GFAT1 mRNA in various human tissues using reverse transcriptase-polymerase chain reaction. We report here the identification and cDNA cloning of a novel GFAT1 splice variant expressed abundantly in skeletal muscle and heart. This subtype, designated GFAT1-L, contains a 54-bp insertion within the GFAT1 coding sequence. Recombinant GFAT1-L protein possessed functional GFAT activities and biochemical characteristics similar to GFAT1. Previously, GFAT1 was considered a simplex enzyme. The identification of a novel GFAT1 subtype possessing functional enzymatic activity and tissue-specific expression should provide additional insight into the mechanism of skeletal muscle insulin resistance and diabetes complications.

Alternative Splicing↗
PubMed2007

Thiamine attenuates the hypertension and metabolic abnormalities in CD36-defective SHR: uncoupling of glucose oxidation from cellular entry accompanied with enhanced protein O-GlcNAcylation in CD36 deficiency.

BACKGROUND AND OBJECTIVES: The spontaneous hypertensive rat (SHR) is a widely studied model of hypertension that exhibits metabolic abnormalities, which share features with the human metabolic syndrome. Genetic linkage studies have revealed a defective CD36 gene, encoding a membrane fatty acid (FA) transporter, in hyperinsulinemia of the SHR. However, there is no unifying mechanism that can explain these phenotypes as a consequence of a defective CD36 gene. Impaired fatty acid uptake is compensated by increased glucose uptake. We hypothesized that (1) the abundant intracellular glucose is not oxidized proportionally and (2) the correction of the uncoupling of glucose oxidation to its cellular entry might be effective against the pathophysiology of CD36-defective SHR. Therefore, we attempted to activate glucose oxidation with the repletion of thiamine, a coenzyme for multiple steps of glucose metabolism. METHODS AND RESULTS: In one series of experiments, intracellular glucose fate was assessed by the ratio of [(14)C]glucose/[(3)H]deoxyglucose radioactivity, which suggested that glucose oxidation was uncoupled from its cellular entry in SHR. Protein O-GlcNAcylation was intense in the hearts of CD36-defective SHR compared with that of wild-type CD36 rats [Wister Kyoto rats (WKY)], indicating the shunt of glucose through the hexosamine biosynthetic pathway (HBP). In another series of studies, 4-week-old SHR were maintained with water containing 0.2% thiamine for 10 weeks. Systolic blood pressure, plasma insulin and norepinephrine levels were significantly lower in the thiamine-group, as compared with the untreated-group. In epididymal adipose tissue, thiamine repletion down-regulated the expression levels of mRNA transcripts for UDP-N-acetylglucosamine:peptide glycosyltransferase, angiotensinogen, angiotensin type 1 receptor, transforming growth factor-beta1 and plasminogen activator inhibitor-1. CONCLUSIONS: The hearts of CD36-defective SHR exhibited uncoupling of glucose oxidation from its cellular entry, accompanied with the enhanced protein O-GlcNAcylation, suggesting increased glucose shunt through the HBP. Thiamine repletion in CD36-defective SHR resulted in (1) the correction of the uncoupling of glucose oxidation to its cellular entry, concomitant with reduced protein O-GlcNAcylation, (2) the down-regulation of the expression of mRNAs involved in HBP, the renin-angiotensin system and adipokines in epididymal adipose tissue, and (3) the attenuation of the hypertension and hyperinsulinemia. We propose that interventions targeting glucose oxidation with thiamine repletion may provide a novel adjunctive approach to attenuate metabolic abnormalities and related hypertension.

Acetylglucosamine↗
PubMed2006

Glucosamine-induced increase in Akt phosphorylation corresponds to increased endoplasmic reticulum stress in astroglial cells.

Increased glucose flux through the hexosamine biosynthetic pathway (HBP) is known to affect the activity of a number of signal transduction pathways and lead to insulin resistance. Although widely studied in insulin responsive tissues, the effect of increased HBP activity on largely insulin unresponsive tissues, such as the brain, remains relatively unknown. Herein, we investigate the effects of increased HBP flux on Akt activation in a human astroglial cells line using glucosamine, a compound commonly used to mimic hyperglycemic conditions by increasing HBP flux. Cellular treatment with 8 mM glucosamine resulted in a 96.8% +/- 24.6 increase in Akt phosphorylation after 5 h of treatment that remained elevated throughout the 9-h time course. Glucosamine treatment also resulted in modest increases in global levels of the O-GlcNAc protein modification. Increasing O-GlcNAc levels using the O-GlcNAcase inhibitor streptozotocin (STZ) also increased Akt phosphorylation by 96.8% +/- 11.0 after only 3 h although for a shorter duration than glucosamine; however, the more potent O-GlcNAcase inhibitors O-(2-acetamido-2-deoxy-D-glucopyranosylidene)amino-N-phenylcarbamate (PUGNAc) and 1,2-dideoxy-2'-propyl-alpha-D-glucopyranoso-[2,1-d]-Delta2'-thiazoline (NAGBT) failed to mimic the increases in phospho-Akt indicating that the Akt phosphorylation is not a result of increased O-GlcNAc protein modification. Further analysis indicated that this increased phosphorylation was also not due to increased osmotic stress and was not attenuated by N-acetylcysteine eliminating the potential role of oxidative stress in the observed phospho-Akt increases. Glucosamine treatment, but not STZ treatment, did correlate with a large increase in the expression of the endoplasmic reticulum (ER) stress marker GRP 78. Altogether, these results indicate that increased HBP flux in human astroglial cells results in a rapid, short-term phosphorylation of Akt that is likely a result of increased ER stress. The mechanism by which STZ increases Akt phosphorylation, however, remains unknown.

Acetylcysteine↗
PubMed2006

Effect of sucrose and saturated-fat diets on mRNA levels of genes limiting muscle fatty acid and glucose supply in rats.

In this study, we examined whether the increased availability of lipids in blood resulting from two types of diet manipulation regulated metabolic gene expression in the skeletal muscle of rats. Feeding for 4 wk on an isocaloric-sucrose or a hypercaloric-fat diet increased plasma TAG in the fed condition by increments of 70 and 40%, respectively, and increased fasting insulinemia (approximately 3-fold) compared with a starch diet. The fat diet impaired glucose tolerance and caused obesity, whereas sucrose-fed rats maintained their normal weight. We analyzed the expression of genes that regulate the exogenous FA supply (LPL, FAT/CD36, FATP1), synthesis (ACC1), glucose (GLUT4, GLUT1, HK2, GFAT1, glycogen phosphorylase) or glycerol (glycerol kinase) provision, or substrate choice for oxidation (PDK4) in gastrocnemius and soleus muscles at the end of the glucose tolerance test. LPL, FAT/CD36, FATP1, PDK4, and GLUT4 mRNA as well as glycogen phosphorylase and glycerol kinase activity levels in both muscles were unchanged by the diets. Increased mRNA levels of GLUT1 (1.6- and 2.6-fold, respectively) and GFAT1 (about 1.7-fold) in gastrocnemius, and of ACC1 (about 1.5-fold) in soleus, were found in both the sucrose and fat groups. In the fat group, HK2 mRNA was also higher (1.8-fold) in the gastrocnemius. Both sucrose and saturated-fat diets prompted hyperinsulinemia and hyperlipemia in rats. These metabolic disturbances did not alter the expression of LPL, FAT/CD36, FATP1, PDK4, and GLUT4 genes or glycogen phosphorylase and glycerol kinase activity levels in either analyzed muscle. Instead, they were linked to the coordinated upregulation in gastrocnemius of genes that govern glucose uptake and the hexosamine pathway, namely, GLUT1 and GFAT1, which might contribute to insulin resistance.

Animals↗
PubMed1983

Size fractionation of anionic oligosaccharides and glycopeptides by high-performance liquid chromatography.

A rapid method for the fractionation of anionic oligosaccharide and glycopeptide species on the basis of net carbohydrate content utilizing high-performance liquid chromatography has been developed. Amine-bearing bonded-phase columns are eluted with a mobile phase consisting of a water:acetonitrile gradient containing 3% acetic acid titrated to pH 5.5 with triethylamine. Phosphorylated and sialylated oligosaccharides within various charge classes differing in their hexose or hexosamine contents but bearing the same number of anionic species can be resolved without prior removal of the anionic moieties. Glycopeptides containing at least as many as six amino acids are also well fractionated on the basis of carbohydrate content. A variety of detection methods may be used and sensitivity in the subnanomole range is possible with fluorescent or radiolabeling techniques. This method offers a significant improvement in the rapidity and resolution attainable for the size fractionation of anionic complex carbohydrates.

Anions↗
PubMed1984

A quantitative determination by capillary gas-liquid chromatography of neutral and amino sugars (as O-methyloxime acetates), and a study on hydrolytic conditions for glycoproteins and polysaccharides in order to increase sugar recoveries.

Complete gas-liquid chromatographic separation of O-methyloxime acetates (syn and anti isomers) prepared from eight neutral sugars, three hexosamines, and muramic acid has been obtained, using a fused-silica Carbowax 20M capillary column. A single hydrolytic step for carbohydrate-containing biological material (less than or equal to 2.5 X 10(-3) M sugar solution in 4 N trifluoroacetic acid at 125 degrees C for 1 h) has been developed, and results have been compared with those obtained with standard hydrolytic conditions in order to ensure complete release of amino sugars from glycoproteins, together with minimum losses of neutral sugars. The combination of this acid hydrolysis with the above improved derivatization procedure for the gas-liquid chromatographic analysis has led to a simple, rapid, and sensitive analytical method, which has been successfully tested on three glycoproteins (fetuin, mucin, and peroxidase) and two plant cell-wall polysaccharide fractions (soluble fibers from carrots and soybeans).

Amino Sugars↗