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PubMed2002

Design and synthesis of a novel class of sugar-peptide hybrids: C-linked glyco beta-amino acids through a stereoselective "acetate" Mannich reaction as the key strategic element.

A new type of sugar-amino acid hybrid, which is comprised of a sugar unit (gluco-, galacto-, or mannopyranose) linked through a C-glycosidic linkage to the beta-position of an alpha-unsubstituted beta-amino acid unit, is presented. It is hypothesized that these new compounds, or the oligomeric peptides derived therefrom, might possess the structural features of beta-amino acid oligomers and the chemical and enzymatic resistance of C-glycosides to hydrolysis. The synthetic strategy is based on a new Mannich-type reaction between a chiral acetate enolate equivalent and alpha-amido sulfones derived from the corresponding sugar-C-glycoside aldehydes. While the sugar-C-glycoside aldehyde partner is prepared from well-established transformations on known sugar precursors, the lithium enolate derived from (1R)-endo-2-acetylisoborneol 3 is employed as the key element. This Mannich approach proceeds with essentially perfect diasteromeric control leading to the new beta-amino carbonyl adducts in good yields. Further, cleavage of the camphor auxiliary is smoothly performed by oxidative treatment with ammonium cerium nitrate (CAN). Complementarily, direct peptide-type coupling of the beta-amino carbonyl Mannich adducts with an alpha- or beta-amino acid residue and subsequent CAN-promoted detachment of the auxiliary yields dipeptide fragments bearing a sugar-containing aliphatic side chain and is a process that can be iterated. A preliminary conformational study based on the combination of experimental NMR data and molecular mechanics and molecular dynamics (MD) of one particular adduct is also provided.

Amino Acids↗

PubMed2000

Mutagenicity of heated sugar-casein systems: effect of the Maillard reaction.

The formation of mutagens after the heating of sugar-casein model systems at 120 degrees C was examined by the Ames test, using Salmonella typhimurium strain TA100. Several sugars (glucose, fructose, galactose, tagatose, lactose, and lactulose) were compared in their mutagenicities. Mutagenicity could be fully ascribed to Maillard reaction products and strongly varied with the kind of sugar. The differences in mutagenicity among the sugar-casein systems were caused by a difference in reaction rate and a difference in reaction mechanism. Sugars with a comparable reaction mechanism (glucose and galactose) showed a higher mutagenic activity corresponding with a higher Maillard reactivity. Disaccharides showed no mutagenic activity (lactose) or a lower mutagenic activity (lactulose) than their corresponding monosaccharides. Ketose sugars (fructose and tagatose) showed a remarkably higher mutagenicity compared with their aldose isomers (glucose and galactose), which was due to a difference in reaction mechanism.

Caseins↗

PubMed2001

Sugar-dependent alterations in cotyledon and leaf development in transgenic plants expressing the HDZhdip gene ATHB13.

ATHB13 is a new member of the homeodomain leucine zipper (HDZip) transcription factor family of Arabidopsis thaliana. Constitutive high-level expression of the ATHB13 cDNA in transgenic plants results in altered development of cotyledons and leaves, specifically in plants grown on media containing metabolizable sugars. Cotyledons and leaves of sugar-grown transgenic plants are more narrow and the junction between the petiole and the leaf blade less distinct, as compared to the wild type. High-level expression of ATHB13 affects cotyledon shape by inhibiting lateral expansion of epidermal cells in sugar-treated seedlings. Experiments with non-metabolizable sugars indicate that the alteration in leaf shape in the ATHB13 transgenics is mediated by sucrose sensing. ATHB13 further affects a subset of the gene expression responses of the wild-type plant to sugars. The expression of genes encoding beta-amylase and vegetative storage protein is induced to higher levels in response to sucrose in the transgenic plants as compared to the wild type. The expression of other sugar-regulated genes examined is unaffected by ATHB13. These data suggest that ATHB13 may be a component of the sucrose-signalling pathway, active close to the targets of the signal transduction.

Amino Acid Sequence↗

PubMed1998

Structures of the N-linked sugar chains in the PAS-6 glycoprotein from the bovine milk fat globule membrane.

The structures of the N-linked sugar chains in the PAS-6 glycoprotein (PAS-6) from the bovine milk fat globule membrane were determined. The sugar chains were liberated from PAS-6 by hydrazinolysis, and the pyridylaminated sugar chains were separated into a neutral (6N) and two acidic chains (6M and 6D), the acidic sugar chains then being converted to neutral sugar chains (6MN and 6DN). 6N was separated into two neutral fractions (6N13 and 6N5.5), while 6MN and 6DN each gave a single fraction (6MN13 and 6DN13). The structure of 6N5.5, which was the major sugar chain in PAS-6, is proposed to be Man alpha1 --> 6 (Man alpha1 --> 3) Man beta1 --> 4GlcNAc beta1 --> 4GlcNAc-PA; 6N13, 6MN13 and 6DN13 are proposed to be Gal beta1 --> 3Gal beta1 --> 4GlcNAc beta1 --> 2Man alpha1 --> 6 (Gal beta1 --> 3Gal beta1 --> 4GlcNAc beta1 --> 2Man alpha1 --> 3) Man beta1 --> 4GlcNAc beta1 --> 4 (Fuc alpha1 --> 6)GlcNAc-PA; 6M and 6D had 1 or 2 additional NeuAc residues at the non-reducing ends of 6MN13 and 6DN13, respectively.

Animals↗

PubMed2001

Sugar-responsible elements in the promoter of a gene for beta-amylase of sweet potato.

Expression of genes coding for sporamin and beta-amylase, the two most abundant proteins in storage roots of sweet potato, is coordinately inducible in atypical vegetative tissues by sugars. A sweet potato gene for beta-amylase (beta-Amy) with introns as well as a beta-Amy::GUS fusion gene composed of the beta-Amy promoter and the GUS coding sequence, both showed sugar-inducible expression in leaves of transgenic tobacco which occurred via a hexokinase-independent pathway. Analyses using various 5'-terminal and internal deletions of the beta-Amy promoter indicated that truncated promoters of beta-Amy containing a sequence between -901 and -820, relative to the transcription start site, and the basic promoter region can confer sugar-inducible expression. This 82 bp region contained the TGGACGG sequence that plays an essential role in the sugar-inducible expression of the truncated promoter of the sporamin gene. Deletion or base substitutions of this element in the truncated beta-Amy promoter abolished the sugar-inducible expression, the results suggesting that the TGGACGG element plays an important role in the coordinate induction of expression of genes for beta-amylase and sporamin by sugars.

Amino Acid Sequence↗

PubMed2003

Preparation and characterization of pH sensitive sugar mediated (polyethylene glycol/chitosan) membrane.

Novel biodegradable membrane based on chitosan matrix was prepared and characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and swelling test. Native sugar, which is commonly used in human life, was utilized to prepare the crosslinked hydrophilic chitosan-polyethylene glycol (PEG) polyblend. According to TGA and FTIR results, the chemical reaction occurred in imine bonds (C=N) between sugar and amino groups in chitosan. Chitosan blending with high swelling capacity of PEG increased the water affinity and reacted with sugar decreased the water affinity. The equilibrium water content (EWC) value of the sugar mediated membrane is in the sequence of sucrose>D-fructose>glucose and they all present much lower water uptake ability than polyblend. The chitosan was not degraded by lysozyme, but all of the sugar-mediated membranes were susceptible to lysozyme. Scanning electron microscope (SEM) morphology shows that the degradation rate not only was controlled by the chemical complexation between sugar and polyblends, but the surface morphology of membranes also has great influence. Sucrose-mediated membrane supports the attachment and growth of NIH 3T3 fibroblasts. The pH-sensitive and well degradable property of the sucrose-mediated membrane can be applied for biomedical application.

Journal Article↗

PubMed2004

Effect of pH, counter ion, and phosphate concentration on the glass transition temperature of freeze-dried sugar-phosphate mixtures.

PURPOSE: The aim of the present work is to study the interaction of phosphate salts with trehalose and sucrose in freeze-dried matrices, particularly the effect of the salts on the glass transition temperature (Tg) of the sugars. METHODS: Freeze-dried trehalose and sucrose systems containing different amounts of sodium or potassium phosphate were analyzed by differential scanning calorimetry to determine the Tg and by Fourier-transform infrared spectroscopy (FTIR) analysis to evaluate the strength of the interaction between sugars and phosphate ions. RESULTS: Sucrose-phosphate mixtures show an increase in Tg up to 40 degrees C in a broad pH range (4-9) compared to that of pure sucrose. Sucrose-phosphate mixtures exhibit a higher Tg than pure sucrose while retaining higher water contents. Trehalose-phosphate mixtures (having a Tg of 135 degrees C at a pH of 8.8) are a better option than pure trehalose for preservation of labile materials. The -OH stretching of the sugars in the presence of phosphates decreases with increase in pH, indicating an increase in the sugar-phosphate interaction. CONCLUSIONS: Sugar-phosphate mixtures exhibit several interesting features that make them useful for lyophilization of labile molecules; Tg values much higher than those observed for the pure sugars can be obtained upon the addition of phosphate.

Calorimetry, Differential Scanning↗

PubMed1980

Insulin stimulates sugar transport in giant muscle fibres of the barnacle.

Insulin stimulates sugar transport in vertebrate skeletal muscle but the mechanism of insulin action is unknown. It has been reported that Na transport in giant muscle fibers of the barnacle (Balanus nubilis) is sensitive to insulin but no one has examined the sensitivity of sugar tansport to insulin in this preparation. We show here that insulin does, indeed, stimulate sugar transport in barnacle muscle. The great advantage of barnacle muscle over all other muscles used so far for investigating the mechanism of insulin action is its large size, which facilitates measurements on single cells and permits the experimenter to control the intracellular environment of the muscle fibre by the technique of internal dialysis. Using single muscle fibres it is possible to show that acceleration of sugar transport by insulin is associated with a fall in ionized Ca, a fall in cyclic AMP and a rise in cyclic GMP. Working with internally dialysed muscle fibres we find that insulin only increases sugar transport when the dialysis solution contains ATP. In the absence of insulin, sugar transport is dialysed muscle is increased by a rise in ionized Ca, a fall in cyclic AMP and, when the internal Ca is elevated, by a rise in cyclic GMP.

Adenosine Triphosphate↗

PubMed2004

Sugar-added beverages and adolescent weight change.

OBJECTIVE: The increase in consumption of sugar-added beverages over recent decades may be partly responsible for the obesity epidemic among U.S. adolescents. Our aim was to evaluate the relationship between BMI changes and intakes of sugar-added beverages, milk, fruit juices, and diet soda. RESEARCH METHODS AND PROCEDURES: Our prospective cohort study included >10,000 boys and girls participating in the U.S. Growing Up Today Study. The participants were 9 to 14 years old in 1996 and completed questionnaires in 1996, 1997, and 1998. We analyzed change in BMI (kilograms per meter squared) over two 1-year periods among children who completed annual food frequency questionnaires assessing typical past year intakes. We studied beverage intakes during the year corresponding to each BMI change, and in separate models, we studied 1-year changes in beverage intakes, adjusting for prior year intakes. Models included all beverages simultaneously; further models adjusted for total energy intake. RESULTS: Consumption of sugar-added beverages was associated with small BMI gains during the corresponding year (boys: +0.03 kg/m2 per daily serving, p = 0.04; girls: +0.02 kg/m2, p = 0.096). In models not assuming a linear dose-response trend, girls who drank 1 serving/d of sugar-added beverages gained more weight (+0.068, p = 0.02) than girls drinking none, as did girls drinking 2 servings/d (+0.09, p = 0.06) or 3+ servings/d (+0.08, p = 0.06). Analyses of year-to-year change in beverage intakes provided generally similar findings; boys who increased consumption of sugar-added beverages from the prior year experienced weight gain (+0.04 kg/m2 per additional daily serving, p = 0.01). Children who increased intakes by 2 or more servings/d from the prior year gained weight (boys: +0.14, p = 0.01; girls +0.10, p = 0.046). Further adjusting our models for total energy intake substantially reduced the estimated effects, which were no longer significant. DISCUSSION: Consumption of sugar-added beverages may contribute to weight gain among adolescents, probably due to their contribution to total energy intake, because adjustment for calories greatly attenuated the estimated associations.

Adolescent↗

PubMed1991

The use of the sugar clock in dental health education.

An important factor in the prevention of dental caries is limiting the number of times in a day that sugar enters the mouth. This can be simply illustrated by using the sugar clock. The effectiveness of this as a technique for teaching 9-11-year-old children the importance of limiting frequency of sugar intakes was tested in a controlled study. Four weeks and 4 months after sugar clocks were used with a study group of children, they showed a significant increase over baseline in the number of correct answers given to a questionnaire. A control group showed no significant increase. It was concluded that the sugar clock is an effective method of teaching the importance of limiting frequency of sugar intake to this age group.

Child↗

PubMed1994

Sugar consumption and dental caries: evidence from 90 countries.

An examination is made of data on dental caries amongst 12-year-old children and sugar consumption of the total population for 90 countries. For the whole data set, DMFT score tends to rise with sugar consumption. The linear relationship between the logarithm of DMFT and sugar is estimated to have a slope of 0.021 per kg/year per head of population (P < 0.0001), and accounts for 28% of the variation in DMFT. In contrast, when data from 29 industrialised nations are analysed separately, there is no evidence of a sugar-caries relationship; the slope of the linear regression line is estimated to be -0.013, not significantly different from zero. This latter result is in agreement with the considerable evidence of a lack of strong relationship between the amount of sugar consumed and caries occurrence in Western countries. These results suggest that, in addition to sugar, other factors, such as other aspects of diet, exposure to fluoride and genetic effects, must be taken into account when seeking to explain variations in caries prevalence, and when making recommendations for caries control.

Australia↗

PubMed2004

Beliefs and attitudes towards the consumption of sugar-free products in a sample of Italian adolescents.

OBJECTIVE: The objective of this study was to investigate beliefs and attitudes towards sugar-free products in a sample of Italian teenagers. DESIGN: A total of 10 secondary public schools in the county of Rome were randomly selected. The probability of being extracted was set proportional to the number of students. A random sample of teenagers was selected from the schools for participating in a food consumption survey. SUBJECTS: The sample included 233 adolescents, aged 15-21 y. A total of 224 adolescents agreed to participate in the study aimed at assessing beliefs and attitudes. INTERVENTIONS: Two questionnaires were completed at the first day of the last period of the 4-day food survey. The first questionnaire contained questions on attitudes and beliefs toward a healthy diet. The second questionnaire, aimed at assessing adolescents' attitudes towards the consumption of sugar-free products, was based in part on the social-psychological model of the Theory of Planned Behaviour. RESULTS: In general, the adolescents of this sample seemed to be quite uncertain in their responses. On average, they did not express an emphatic point of view with regard to the act of eating sugar-free products. The results of the assessment of relationships between the variables of the theoretical model revealed the lack of causal links among beliefs, attitudes, intention and consumption of sugar-free products. Perceived behavioural control was not a significant predictor of intention. CONCLUSIONS: The target of further studies aimed at investigating attitudes towards sugar-free products should be tailored according to the quantity of consumption of such products in order to represent a sample of frequent and high consumers of sugar-free products. SPONSORSHIP: European Commission Quality of Life and Management of Living Resources Fifth framework Programme. QLRT-1999-00155.

Adolescent↗

PubMed2005

Prevalence of dental caries and sugar consumption among 6-12-y-old schoolchildren in La Trinidad, Benguet, Philippines.

OBJECTIVE: To determine the prevalence of dental caries and the level of sugar consumption among 6-12-y-old schoolchildren in La Trinidad, Benguet, Philippines. DESIGN: A Cross-sectional study as a baseline survey for a later intervention program. A questionnaire was distributed to obtain information on dental history and total consumption of food with sugar. Caries were diagnosed based on the WHO recommendation. RESULTS: A total of 1200 schoolchildren, aged 6-12 y were included. The prevalence of dental caries in primary dentition was 71.7% and in the permanent dentition, 68.2%. The mean total decayed, extracted due to caries and filled primary teeth (DMFT) and decayed, missing and filled permanent teeth (DMFT) were 4.12 (s.d. 4.03) and 2.40 (s.d. 2.57), respectively. As age increased the mean DMFT increased. Majority (70%) had tooth brushing practices, and less than half (42.5%) had a dental visit only when necessary. Their sugar intake was twice more than the WHO recommendation with a mean daily total intake of 59 g per person. Most common sources of dietary sugar were hard candies (89%), banana cue (84.9%), camote cue (84.9%) and soft drinks (84.4%). No significant correlation was found between sugar intake and dental caries. CONCLUSION: The results indicate that dental caries is highly prevalent and increase with augmented sugar consumption. This maybe due to a widespread neglect of oral health and an increased availability of refined sugary products. Caries rates mirrored those of the developing countries with untreated lesions dominating all ages. The high level of untreated caries in all age groups is a cause for concern.

Child↗

PubMed1987

Sugar uptake by fluid-phase pinocytosis and diffusion in isolated rat hepatocytes.

Measurements of sugar pinocytosis (fluid-phase endocytosis of radiolabelled sucrose, lactose and raffinose) in freshly isolated rat hepatocytes are disturbed by sugar diffusing into the cells through plasma-membrane blebs. Non-pinocytic entry may be even more pronounced at 0 degrees C, and is a major contributor to 'background' radioactivity. By electrodisruption of the plasma membrane, a distinction can be made between pinocytotically sequestered sugar and free sugar that has entered the cytosol by diffusion. Pinocytosis proceeds at a rate of 2%/h (relative to the intracellular fluid volume), whereas the rate of sucrose entry by diffusion is more than twice as high. Three pinocytotic compartments are distinguishable in isolated hepatocytes: (1) a rapidly recycling compartment, which is completely destroyed by electrodisruption, and which may represent pinocytic channels continuous with the plasma membrane; (2) a non-recycling (or very slowly recycling) electrodisruption-resistant compartment, which allows accumulation of the lysosomally hydrolysable sugar lactose, and which therefore must represent non-lysosomal vacuoles (endosomes?); (3) a lysosomal compartment (non-recycling, electrodisruption-resistant), which accumulates raffinose and sucrose, but which hydrolyses lactose. The last two compartments can be partially resolved in metrizamide/sucrose density gradients by the use of different sugar probes.

Animals↗

PubMed1998

Stability of captopril in invert sugar solution.

OBJECTIVE: To assess the stability of captopril in different concentrations of invert sugar solution and to verify the hypothesis that the antioxidant effect of invert sugar can inhibit captopril's oxidative degradation. METHOD: Captopril 1 mg/ml formulations were prepared in 0% (Milli-Q water), 1%, 10%, 30% and 85% w/v of invert sugar and stored at 5 C. The formulations were sampled at intervals up to 30 days for assay of captopril using a stability-indicating high-performance liquid chromatographic method. RESULTS: Captopril in formulations containing low concentrations (1%, 10%, 30% w/v) of invert sugar was significantly less stable than in the control formulation (captopril 1 mg/ml in Milli-Q water). In contrast, captopril in a formulation containing 85% w/v invert sugar was substantially more stable than in the control. CONCLUSION: Captopril formulated in a solution of 85% w/v invert sugar is stable for at least 2 weeks when stored at 5 degrees C.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed2000

The Arabidopsis SUCROSE UNCOUPLED-6 gene is identical to ABSCISIC ACID INSENSITIVE-4: involvement of abscisic acid in sugar responses.

In plants, sugars act as signalling molecules that control many aspects of metabolism and development. Arabidopsis plants homozygous for the recessive sucrose uncoupled-6 (sun6) mutation show a reduced sensitivity to sugars for processes such as photosynthesis, gene expression and germination. The sun6 mutant is insensitive to sugars that are substrates for hexokinase, suggesting that SUN6 might play a role in hexokinase-dependent sugar responses. The SUN6 gene was cloned by transposon tagging and analysis showed it to be identical to the previously described ABSCISIC ACID INSENSITIVE-4 (ABI4) gene. Our analysis suggests the involvement of abscisic acid and components of the abscisic acid signal transduction cascade in a hexokinase-dependent sugar response pathway. During the plant life cycle, SUN6/ABI4 may be involved in controlling metabolite availability in an abscisic acid- and sugar-dependent way.

Abscisic Acid↗

PubMed2000

The Arabidopsis sugar-insensitive mutants sis4 and sis5 are defective in abscisic acid synthesis and response.

Although soluble sugar levels affect many aspects of plant development and physiology, little is known about the mechanisms by which plants respond to sugar. Here we report the isolation of 13 sugar-insensitive (sis) mutants of Arabidopsis that, unlike wild-type plants, are able to form expanded cotyledons and true leaves when germinated on media containing high concentrations of glucose or sucrose. The sis4 and sis5 mutants are allelic to the ABA-biosynthesis mutant aba2 and the ABA-insensitive mutant abi4, respectively. In addition to being insensitive to glucose and sucrose, the sis4/aba2 and sis5/abi4 mutants also display decreased sensitivity to the inhibitory effects of mannose on early seedling development. Mutations in the ABI5 gene, but not mutations in the ABI1, ABI2 or ABI3 genes, also lead to weak glucose- and mannose-insensitive phenotypes. Wild-type and mutant plants show similar responses to the effects of exogenous sugar on chlorophyll and anthocyanin accumulation, indicating that the mutants are not defective in all sugar responses. These results indicate that defects in ABA metabolism and some, but not all, defects in ABA response can also alter response to exogenous sugar.

Abscisic Acid↗

PubMed2006

Adhesion and detachment mechanisms of sugar surfaces from the solid (glassy) to liquid (viscous) states.

The viscosity of some sugars varies continuously by approximately 10 orders of magnitude over a temperature range of 50 degrees C. Sugars are therefore ideal model materials for studying the failure mechanism of materials as they change from the solid to the liquid state. We have used a surface forces apparatus coupled to interference and optical microscopy imaging to study the way two sugar surfaces adhere and detach from adhesive contact. The sugar-coated layers on mica displayed significant loading-unloading hysteresis, and the adhesive strength and failure mechanism during a "loading-unloading cycle" depended on the loading rate, contact time, and unloading rate. The failure of two glassy sugar surfaces was manifested by the nucleation of many sharp microcracks at the external boundary that rapidly propagate along the original contact interface. At the other extreme, when the material is a liquid, "failure" occurs through the nucleation and inward growth of large rounded ripples, characteristic of a Saffman-Taylor fingering instability. In the transition from glassy to viscous failure, sharp crack tips and smooth rounded fingers coexist during the crack propagation. In addition, whereas the detachment geometry of two glassy surfaces was characterized by a peeling-like mechanism along a plane, the fingers associated with the "snapping" of a liquid neck extended in all directions. These findings provide insights into the adhesion and failure mechanisms of materials at the micro/nanoscales and are also relevant to the action of interparticle forces between sugar particles, such as those used in inhalation drug delivery.

Adhesiveness↗