Enhancement of S-nitrosylation in glycosylated hemoglobin

In this study, we report a novel differential nitric oxide interaction with nonglycosylated and glycosylated hemoglobin. After in vitro incubation of hemoglobin with S-nitroso N-acetyl penicillamine (SNAP), S-nitrosoglutathione, or S-nitrosocysteine, S-nitrosylation was significantly higher in human glycosylated hemoglobin purified from diabetic subjects compared to nondiabetic controls. Inversely, spontaneous decomposition was significantly lower for S-nitrosohemoglobin obtained from glycosylated hemoglobin. Bidimensional isoelectric focusing of hemoglobins incubated in vitro with SNAP also revealed a greater interaction of nitric oxide with glycosylated hemoglobin. In addition, a significantly higher level of S-nitrosohemoglobin was found in erythrocyte lysates from streptozotocin-induced diabetic rats compared to control rats. We suggest that highly glycosylated hemoglobin in diabetic subjects may favor S-nitrosylation, which may in turn impair vascular function, and participate in diabetic microangiopathy.     

Measurement of serum glycosylated proteins and glycosylated low density lipoprotein fraction in diabetes mellitus

A simple method was developed for estimating serum glycosylated protein levels using gel filtration with Bio-Gel P6 by determining the protein and sugar content in the void volume fraction. The glycosylated protein levels (GSP) correlated well with fasting blood sugar levels and glycosylated albumin level (G-ALB) determined by affinity chromatography with Blue Sepharose CL6B. The glycosylation level of heparin-citrate precipitable fraction of serum which predominantly contained low density lipoprotein (G-LDL) also correlated well with GSP and LDL-cholesterol levels. Significantly different values were obtained for GSP, G-ALB, and G-LDL between normals and diabetics.     

A theoretical model to predict the behavior of glycosylated hemoglobin levels

The measurement of glycosylated hemoglobin as a percentage of total hemoglobin is rapidly becoming the standard method of monitoring the average blood sugar level in diabetics for research purposes and may soon become the standard for clinical care and diagnosis. Much speculation exists in the literature about the nature of the glycosylation reaction. Most experimenters expect a linear relationship between the plasma glucose level and percent glycosylated hemoglobin in whole blood; however, a curve of decreasing slope with increasing glucose concentration is found.Here, a reaction model including simple first order kinetics between glucose and hemoglobin and a finite erythrocyte life of 120 days is considered. By carrying out the integration for each erythrocyte cohort followed by an integration combining all cohorts, a curve corresponding to the experimental result is found. In addition, results on expected glycosylated hemoglobin percent as a function of erythrocyte age and plasma glucose concentration are presented as well as a plot of glucose concentration versus glycosylated hemoglobin percent for the 40-day erythrocyte life in mice. All of the results correlate with experimental values in the literature if a rate constant of k = 1·0 × 10^?5dlmg^?1 day is used.The evaluation of a radioactive iron-transferrin experiment in the literature reveals the possibility that the glycosylation reaction begins during erythropoiesis.Finally, a curve is displayed which shows the expected 120-day decay during normoglycemia, of an elevated glycosylated hemoglobin level resulting from a preceding period of constant hyperglycemia.     

Adducts of glycosylated serum albumin with amino acids

Glycosylation of human serum albumin was conducted by its long incubation with the excess either of D-glucose or D-glucose-6-phosphate at 37 degrees C. The glycosylated fractions were isolated by the cation-exchange chromatography on CM-cellulose. The quantity of glucose bound covalently with protein was determined by thiobarbituric acid. The glucose-modified human serum albumin forms stable adducts with amino acids. These complexes are, evidently, produced as a result of the Schiff's base formation between the carbonyl group of the ketoamine adduct of glucose with protein and primary amino group of amino acid further followed by the Amadori rearrangement.     

Isolation of glycosylated hemoglobins by a combination of ion-exchange and gel-filtration chromatographies: a pilot study

The techniques of ion exchange and gel filtration have been combined in a single chromatographic column which allows the simultaneous isolation of hemoglobins glycosylated at their beta-amino termini from other hemoglobin species as well as from molecules differing in size from the hemoglobins. This method is unique because it makes possible isolation of preparative quantities of glycosylated hemoglobins within approximately 15 min. The method works most efficiently with a dry weight-to-weight ratio of Biorex 70 to Sephadex G25 of 1.4 to 1.0. The technique was applied to the determination of the apparent first-order rate constant for the deglycosylation of the labile form of hemoglobin AIc.     

Association of dietary and serum selenium concentrations with glucose level and risk of diabetes mellitus: A cross sectional study of national health and nutrition examination survey, 1999-2006

BackgroundThe associations among dietary selenium intake, serum selenium concentration, plasma glucose and glycosylated hemoglobin levels, and diabetes risk remain controversial. This study aimed to evaluate these associations in adults from the United States.MethodsWe conducted a cross-sectional study of participants aged 18 years and older who participated in the National Health and Nutrition Examination Survey. Between 1999 and 2006, a total of 41,474 participants were initially included in this study. Multivariable linear or logistic regression analysis was used to investigate the association between dietary selenium intake and serum selenium concentrations, glucose level, and diabetes risk.ResultsThe average age of the participants was 30.32 ± 23.95 years, and 48.72 % were men. Their mean dietary selenium intake and mean serum selenium concentration were 98 ± 55 μg per day and 129 ± 22 ng/mL, respectively. Compared with t he lowest quartile of dietary selenium intake, the highest quartile was associated with elevated plasma glucose levels (β = 2.412, 95 % confidence interval [CI]: 0.420, 4.403, P = 0.018), glycosylated hemoglobin levels (β = 0.080, 95 % CI: 0.041, 0.119, P < 0.001), and diabetes risk (odds ratio [OR] = 2.139, 95 % CI: 1.763, 2.596, P < 0.001). Higher serum selenium was also associated with increased plasma glucose levels (β = 12.454, 95 % CI: 4.122, 20.786, P = 0.003) and glycosylated hemoglobin levels (β = 0.326, 95 % CI: 0.187, 0.465, P < 0.001). A generalized additive model with a spline curve suggested a nonlinear relationship between dietary selenium intake, serum selenium and glucose levels, and diabetes risk.ConclusionsDietary selenium intake and serum selenium were positively associated with elevated levels of plasma glucose and glycosylated hemoglobin, and the relationships were nonlinear. Additional selenium supplementation for patients with diabetes may not be recommended.     

Determination of glycosylated albumin in controls and in diabetics by affinity chromatography with phenylboronic acid

The determination of glycosylated albumin was performed in 19 diabetic patients and in 16 control subjects, by means of chromatographic separation on columns of phenilboronic acid, immobilized by agarose gel. The interference with free glucose was eliminated by serum gel filtration on sephadex G 25 columns. The results demonstrated that glycosylated albumin values, obtained by affinity chromatography, discriminate diabetic by non-diabetic subjects and significantly correlate with glycosylated proteins levels, taken by colorimetric method with thiobarbituric acid. The chromatographic technique resulted in a more simplified way than colorimetric method and has shown to be sensitive to significant increases in "in vitro" glycosylation. Moreover it lasts less than the other technique and its variation coefficient is extremely low. In conclusion it represents a progress in the routine determination of glycosylated albumin.     

The glycan structure of albumin Redhill, a glycosylated variant of human serum albumin.

Although human serum albumin is synthesized without carbohydrate, glycosylated variants of the protein can be found. We have determined the structure of the glycan bound to the double-mutant albumin Redhill (-1 Arg, 320 Ala-->Thr). The oligosaccharide was released from the protein using anhydrous hydrazine, and its structure was investigated using neuraminidase and a reagent array analysis method, which is based on the use of specific exoglycosidases. The glycan was shown to be a disialylated biantennary complex type oligosaccharide N-linked to 318 Asn. However, a minor part (11 mol%) of the glycan was without sialic acid. The structure is principally the same as that of glycans bound to two other types of glycosylated albumin variants. Glycosylation can affect, for example, the fatty acid binding properties of albumin. Taking the present information into account, it is apparent that different effects on binding are caused not by different glycan structures but by different locations of attachment, with the possible addition of local conformational changes in the protein molecule.     

Comparison of IgG3 responses to carbohydrates following mouse infection or immunization with six species of Trichinella

The IgG3 antibody responses to carbohydrate epitopes were compared in BALB/c mice infected or immunized with six species of Trichinella: T. spiralis (T1), T. nativa (T2), T. britovi (T3), T6, T. nelsoni (T7), and T8. The dynamics of IgG3 responses and antigen recognition following infection or immunization were measured by ELISA and Western blot respectively, using glycosylated and deglycosylated larval crude extracts (LCE) prepared from homologous isolates. A high degree of protein glycosylation was found in all species and with similar profiles. Deglycosylation was completely achieved only in LCE from T1 and T6 isolates. The dynamics of IgG3 responses following infection or immunization significantly differed whereas the antigen recognition profiles appeared similar. Variations in the levels and antigen recognition patterns of IgG3 among the different species were apparent. The highest IgG3 levels were recorded in infections by the T8 isolate and the lowest in infections by the T6 isolate, whereas for immunization the highest IgG3 response was induced by T7 and the lowest by T8. Following antigen deglycosylation, the IgG3 responses were significantly reduced or abrogated and the recognition patterns markedly modified or suppressed in the different species of Trichinella.     

Glycosylated hemoglobin measured by affinity chromatography in diabetic and nondiabetic patients on long-term dialysis therapy.

We measured by affinity chromatography glycosylated hemoglobin levels in the blood of 43 diabetic and nondiabetic patients (139 measurements) on long-term dialysis therapy (continuous ambulatory peritoneal dialysis and hemodialysis) to determine the usefulness of this method of estimating glycemic control in diabetic persons on dialysis therapy. In nondiabetic patients, glycosylated hemoglobin levels were within the normal range (4.0% to 6.8% of total blood hemoglobin levels) for both continuous ambulatory peritoneal dialysis and hemodialysis. Glycosylated hemoglobin values correlated significantly with fasting blood glucose levels, serum urea levels, and serum total carbon dioxide content. By stepwise regression, fasting blood glucose values accounted statistically for .54 of the variability (R2) in glycosylated hemoglobin. The contribution of the other variables to this variability was minimal. In 9 diabetic patients (3 on hemodialysis), glycosylated hemoglobin levels correlated significantly with average daily blood glucose levels. Regression of the fasting blood glucose value on glycosylated hemoglobin was similar between continuous ambulatory peritoneal dialysis and hemodialysis. Measuring glycosylated hemoglobin levels by affinity chromatography is a suitable method for assessing glycemia in dialysis patients.     

Some species of human leukocyte interferon are glycosylated

The carbohydrate content of all of the species of human leukocyte interferon (IFN-alpha) which have been derived from patients with chronic myelogeneous leukemia (CML) and purified to homogeneity has now been determined. Amino sugar content was measured by high-performance liquid chromatography and fluorescamine detection of acid hydrolysates of each sample. Two species showed significant amounts of glucosamine. Most of the purified species of leukocyte interferon from a myeloblast cell line were also tested, and two species were found to contain sugar residues. These forms also differed from the CML interferons in that they revealed the presence of greater amounts of galactosamine. The apparent lack of carbohydrate in some of the higher-molecular-weight species of interferon implicated factors other than glycosylation in the molecular weight differences. The results indicate that some species of IFN-alpha are glycosylated to various degrees.     

Nonenzymatic glycosylation of albumin in vivo. Identification of multiple glycosylated sites

Nonenzymatic glycosylation of albumin in vivo occurs at multiple sites. Glucose gets attached to Lys-199, Lys-281, Lys-439, and Lys-525 as well as to some other lysine residues. The principal glycosylated site is Lys-525. Approximately 33% of the overall glycosylation occurs at this site. This site specificity is remarkable and is postulated to be a consequence of local catalysis of the nonenzymatic glycosylation reaction. It appears that positively charged amino groups in the protein catalyze the Amadori rearrangement at specific sites. The principal glycosylated site, Lys-525, lies in a Lys-Lys sequence; other glycosylated sites lie in a Lys-Lys, Lys-His, and Lys-His-Lys sequence or are near disulfide bridges, which are likely to place amino groups of more remote parts of the protein closer to these sites. The occurrence of nonenzymatic glycosylation at most of the identified sites in albumin from diabetic patients is explained by the concept of local acid-base catalysis of the Amadori rearrangement.     

Effect of Temperature on Development and Immature Survival in the Scale Insect Predator, Chilocorus nigritus (F.) (Coleoptera: Coccinellidae)

Developmental and immature survival rates of the coccidophagous coccinellid Chilocorus nigritus (F.) were examined under constant, cycling and glasshouse temperatures in order to determine its suitability for use as a biological control agent in temperature glasshouses. First instar larvae did not complete development at 18 C. However, within the range 20-30 C, the developmental rate increased with rising temperature. The theoretical lower thermal threshold for development was found to be 16.6 C. Thermal summation and polynomial regression methods were used to predict developmental periods under glasshouse conditions. The predictions were accurate to within a mean of 10% in relation to observed data. Under laboratory conditions, immature survival rates were highest 28 C (52%) and lowest at (and below) 20 C (17%). First instar larvae suffered the highest mortality rates, while pupae had the lowest. Under glasshouse conditions, the survival rates were much lower (9% in the winter months and 20% throughout the remainder of the year), but the species was considered to be a suitable biocontrol agent if mean daily temperatures were maintained at levels above 20 C.     

Endocytosis of native and glycosylated bovine serum albumin by duct cells of the rat parotid gland

Summary The ability of duct cells of the rat parotid gland to internalize bovine serum albumin (BSA) and several glycosylated albumins (glucosamide, galactosamide, fucosamide, lactosyl, p-aminophenyl-N-acetyl-D-glucosamide, p-aminophenyl-N-acetyl-D-mannopyranoside, p-aminophenyl-N-acetyl-D-galactosamide) was investigated. The various BSA preparations were infused into the gland via the main excretory duct, after which the tissues were fixed and prepared for light and electron microscopy. Immunolocalization of native BSA, as well as the glycosylated BSAs, was performed on thin sections, using an unlabeled antibody to BSA followed by protein A-colloidal gold. Gold particles were present over the lumina of both intercalated ducts and striated ducts, and over small endocytic structures and large vacuoles in the apical cytoplasm of both duct cell types. Endocytosis of the glycosylated BSAs by duct cells was greater than native BSA. Fucosylamide-BSA and mannopyranoside-BSA were taken up to a greater extent than the other glycosylated BSAs. Uptake by intercalated duct cells was greater than by striated duct cells, was independent of the concentration of the glycosylated BSA, and was reduced by an excess of the corresponding sugar. Striated duct cells showed some damage by the glycosylated BSAs that was concentration-dependent, and which was reduced in the presence of an excess of the corresponding sugar. These results suggest that endocytosis by salivary gland duct cells may involve specific recognition of carbohydrate residues and that the endocytosis of acinar secretory proteins observed in certain conditions may be due to increased and/or altered protein glycosylation.     

Biosynthesis of glycosylated human lysozyme mutants.

Complementary DNA encoding human lysozyme was subjected to oligonucleotide-directed mutagenesis. At one of three selected positions, amino acid residues 22, 68, or 118, the signal for N-linked glycosylation was created. The mutant DNAs were inserted into a eucaryotic vector and transfected into cultured hamster cells. The three mutant cDNAs directed synthesis of lysozyme mutants, which were named LI, LII, and LIII. The mutant lysozymes LI and LII comprised mixtures of glycosylated and nonglycosylated forms. The glycosylated and nonglycosylated forms of mutant LI were found to have an enzymatic activity similar to normal human milk lysozyme. The usage of the glycosylation sites in the mutants was similar in Chinese hamster ovary (CHO) and baby hamster kidney cells. Approximately two of every three molecules in mutant LI, approximately one of every eight molecules in mutant LII, and practically no molecules in mutant LIII became glycosylated. In CHO cells, the processing of the oligosaccharide side chains yielded several larger products than in baby hamster kidney cells. This size variability of glycosylated lysozyme from CHO cells may be explained by the presence of biantennary and triantennary endo-beta-N-acetylglucosaminidase H-resistant oligosaccharides with N-acetyllactosamine repeats of variable length and by the presence of hybrid oligosaccharides, as suggested by affinity to several lectins and sensitivity to endo-beta-galactosidase. In both cell types, the majority of the glycosylated forms were secreted and thus behaved similarly to nonglycosylated lysozyme. A small proportion of mutant LI lysozyme remained associated with the cells. The retained lysozyme was recruited predominantly from the molecules bearing high mannose oligosaccharides. These molecules were targeted to lysosomes, and their carbohydrate was trimmed to an endo-beta-N-acetylglucosaminidase H-resistant form. Owing to the small size of mutant LI lysozyme, minor changes in the size of its carbohydrate moiety result in detectable changes in the electrophoretic mobility of the whole glycoprotein. We suggest that this novel glycoprotein could be used as a reporter in studies on processing and segregation of glycoproteins.     

Measurement of receptor-independent metabolism of low-density lipoprotein. An application of glycosylated low-density lipoprotein

Incubation of human low-density lipoprotein (LDL) with glucose results in a nonenzymatic formation of a Schiff base between the monosaccharide and lysyl residues of apolipoprotein B. Increasing the percentage of lysyl residues of apolipoprotein B modified by glycosylation decreases the fractional catabolic rate of the glycosylated LDL, and decreases the metabolism of the glycosylated LDL by human skin fibroblasts. The glycosylated LDL, containing 20-40% of total lysyl residues of apoprotein B modified, was metabolized at a slow rate by both human skin fibroblasts and mouse peritoneal macrophages. These results led to the suggestion that glycosylated LDL is primarily catabolized via a receptor-independent process. Assuming LDL catabolism occurs via receptor-dependent and receptor-independent processes, the ratio of (fractional catabolic rate of glycosylated LDL)/(fractional catabolic rate of native LDL) should be an estimate of the percentage of LDL catabolism via the receptor-independent process. From the fractional catabolic rates of glucose-LDL (20-40% of lysyl residues modified) and galactose-LDL (30-60% of lysyl residues modified) 41% and 30% respectively, of LDL catabolism occurred by a receptor-independent process.     

醋甲唑胺治疗2 型糖尿病的临床疗效及安全性观察

目的:评价青光眼治疗药物醋甲唑胺用于2型糖尿病治疗的有效性及安全性。方法:选择我院2型糖尿病初诊患者64例,随机分为两组,其中醋甲唑胺治疗组32例,对照药物二甲双胍32例。观察并比较两组患者治疗前后血糖及糖化血红蛋白水平变化,以及肝肾功能、血尿常规等安全性指标。结果:与治疗前比较,两组患者治疗后糖化血红蛋白水平均下降,差异具有统计学意义(P0.05);但治疗后两组间糖化血红蛋白水平比较,差异无统计学意义(P0.05);两组治疗前后肝功肾功等生化指标之间比较,差异无统计学意义(P0.05);两组用药安全性比较,差异无统计学意义(P0.05)。结论:醋甲唑胺与二甲双胍具有相似的降血糖疗效,可作为新的治疗糖尿病的二线药物选择性使用。     

Characterization of a single glycosylated asparagine site on a glycopeptide using solid-phase Edman degradation

The characterization of site-specific glycosylation is traditionally dependent on the availability of suitable proteolytic cleavage sites between each glycosylated residue, so that peptides containing individual glycosylation sites are recovered. In the case of heavily glycosylated domains such as theO-glycosylated mucins, which have no available protease sites, this approach is not possible. Here we introduce a new method to gain site-specific compositional data on the oligosaccharides attached to a single amino acid. Using a model glycopeptide from a mutant human albumin Casebrook, glycosylated PTH-Asn was recovered after sequential solid-phase Edman degradation, subjected to acid hydrolysis and the sugars were identified by high performance anion exchange chromatography with pulsed amperometric detection. The PTH-Asn(Sac) derivative was further characterized by ionspray mass spectrometry. Comparison between an endoproteinase Glu-C glycopeptide and a tryptic glycopeptide showed that the oligosaccharide attached to Asn494 was stable after at least 10 cycles of Edman degradation.     

2,3-diphosphoglycerate and glycosylated hemoglobin in diabetes mellitus

Large amounts of intraerythrocyte 2-3 diphosphoglycerate (2-3 DPG) increase red cell oxygen-releasing capacity. Since glycosylated hemoglobins, found in higher percentages in diabetics, have an increased oxygen affinity, 2-3 DPG concentration was assayed in 12 diabetics (4 I.D.D., 8 N.I.D.D.) and 18 healthy volunteers. 2-3 DPG was related to glycemic fasting values and to glycosylated hemoglobins to evaluate if 2-3 DPG levels increase in diabetics as a compensatory mechanism to prevent peripheral hypoxia. 2-3 DPG values were significantly higher in diabetics than in normals: 11.4 mumol/gHb +/- 1.7 (= M +/- 1 SD) vs 9.8 mumol/gHb +/- 2.3 (p less than 0.05). 2-3 DPG did not correlate significantly to glycosylated hemoglobins or to glycemic values neither in diabetics nor in normals. These preliminary observations emphasize the usefullness of 2-3 DPG assay in evaluating peripheral oxygenation in diabetics: 2-3 DPG is higher in diabetics but does not correlate to glycemic equilibrium.     

变形链球菌对不同牙科充填材料的粘附及早期生物膜的形成

目的探讨变形链球菌对不同牙科充填材料的粘附和早期生物膜的形成.方法比较经放射性同位素3H-TDR(3H-胸腺嘧啶核苷)标记的变形链球菌对3种唾液包被的充填材料的粘附.采用蛋白质测量试剂盒定量分析其对唾液蛋白的吸附量;采用凝胶电泳和图像分析系统定量分析其对唾液白蛋白和α-淀粉酶的吸收率.结果各种材料对变形链球菌的粘附能力,对唾液蛋白的吸附能力均随着材料的不同而不同.Fuji IX对细菌的粘附量很高,但是对蛋白的吸附量却很低;而F2000对细菌的粘附量很低,对蛋白的吸附量却很高.结论在不同充填材料表面形成的生物膜是不同的,提示早期生物膜的形成具有一定的特异性.这种生物膜的差异对口腔微生态环境及龋病和/或牙周病的发展具有重要意义.