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PubMed1969

Regulation of sugar transport in isolated bacterial membrane preparations from Escherichia coli.

The experiments presented in this paper demonstrate that glucose transport via the phosphoenolpyruvate-phosphotransferase system as studied in isolated E. coli membrane preparations is subject to regulation by sugar-P's. Glucose transport in these preparations is inhibited by glucose-6-P, glucose-1-P, and, to a lesser extent, by other P-esters. There appear to be two inhibitory sites, one specific for glucose-1-P and related sugar-1-P's and the other specific for glucose-6-P and related sugar-6-P's. The inhibition by these sugar-P's is noncompetitive, and the inhibitory sites are separate, subject to independent control, and apparently are accessible from outside the membrane. Furthermore, glucose-6-P is able to reverse partially inhibition of glucose transport by glucose-1-P and vice versa. Preliminary evidence is presented indicating that glucose-1-P may play a central role in the regulation of sugar transport in general, by virtue of its ability to inhibit selectively the transport of sugars other than glucose.

Biological Transport↗

PubMed1986

Variable stoichiometry of phosphate-linked anion exchange in Streptococcus lactis: implications for the mechanism of sugar phosphate transport by bacteria.

Phosphate/2-deoxyglucose 6-phosphate antiport in Streptococcus lactis showed an exchange stoichiometry that varied over a 2-fold range when assay pH was shifted between pH 8.2 and pH 5.2. At pH 7.0 and above, 2 mol of phosphate moved per mol of sugar phosphate; at pH 6.1 the ratio was 1.5:1, while at pH 5.2 the overall stoichiometry fell to 1.1:1. This pattern was not affected by valinomycin in potassium-based media, nor could variable stoichiometry be attributed to altered hydrolysis of the sugar phosphate substrate. In kinetic studies at pH 7.0 or pH 5.2, sugar 6-phosphate was a competitive inhibitor of phosphate transport, indicating operation of a single system. Parallel tests showed that the affinity of antiport for its sugar 6-phosphate substrate was insensitive to pH in this range. Overall, such results suggest a neutral exchange that has specificity for monovalent phosphate but that selects randomly among the available mono- and divalent sugar 6-phosphates. A simple model that shows this behavior suggests a mechanistic role for anion exchange in bacterial transport of sugar phosphate or other organic anions.

Anions↗

PubMed1990

Sugars induce the Agrobacterium virulence genes through a periplasmic binding protein and a transmembrane signal protein.

Phenolic plant metabolites such as acetosyringone induce transcription of the virulence (vir) genes of Agrobacterium tumefaciens through the transmembrane VirA protein. We report here that certain sugars induce the vir genes synergistically with phenolic inducers by way of a distinct regulatory pathway that includes VirA and a chromosomally encoded virulence protein, ChvE. Sequence comparison showed that ChvE is a periplasmic galactose-binding protein corresponding to the GBP1 protein isolated from Agrobacterium radiobacter. Like homologous sugar-binding proteins in Escherichia coli, ChvE was required for chemotaxis toward galactose and several other sugars. These sugars strongly induced vir gene expression in wild-type cells when acetosyringone was absent or present in low concentrations. Mutations in chvE abolished vir gene induction by sugars and resulted in a limited host range for infection but did not affect vir gene induction by acetosyringone. A mutant lacking the periplasmic domain of VirA exhibited the same regulatory phenotype and limited host range as chvE mutants. These data show that the vir genes are regulated by two separate classes of plant-derived inducers by way of distinct regulatory pathways that can be separated by mutation. Induction by sugars is essential for infection of some but not all plant hosts.

Amino Acid Sequence↗

PubMed1999

Sugars including erythronic and threonic acids in human aqueous humour.

PURPOSE: Sugars in the aqueous humour of the eye serve both as a source of nutrients to the lens and other anterior ocular tissues, and potentially as an indicator of waste products from these tissues. In this work we intended to measure the levels of sugars in human blood and aqueous humour from cataract patients with and without diabetes. After initial results we decided to identify an unknown sugar component. METHODS: Sugars were measured by hplc. The unknown sugar peak was identified by gas chromatography/mass spectrometry RESULTS: Very little fructose and sorbitol were found. Glucose levels were higher in both blood and aqueous from diabetic patients. During these analyses we found a major component that did not correspond to any sugar reported previously in aqueous humour. This was identified as a mixture of threonic and erythronic acids. CONCLUSIONS: Glucose levels increase in human aqueous humour in diabetes without markedly raised levels of sorbitol or fructose. Erythronic and threonic acids are normal components of aqueous humour and blood. They may be derived from glycated proteins or from degradation of ascorbic acid.

Aged↗

PubMed1994

Effects of feeding restriction and meal pattern of a sugar beet-containing diet and control diet on nutrient digestibility, plasma lipid concentrations and postprandial triacylglycerol response in broiler chickens.

Broiler chickens were fed on a control diet based on maize or a diet containing sugar-beet-pulp fibre (Beetfiber) at an inclusion level of 46 g/kg. Diets were provided ad lib. or at a restricted level either once daily or three times daily. On days 13 and 20, chickens fed on the ad lib. control and sugar-beet-pulp-containing diets generally weighed more and had poorer feed conversion ratios than chickens given the restricted control and sugar-beet-pulp-containing diets respectively. Furthermore, chickens given the restricted diets once daily had greater body weights and generally improved feed conversion efficiencies compared with chickens given the restricted diets three times daily. Generally, elevated plasma lipid concentrations were observed amongst chickens given the restricted diets once daily compared with chickens fed ad lib. as well as the restricted diets three times daily, while chickens fed on restricted diets three times daily had plasma lipid concentrations intermediate between those fed ad lib. and once daily. In a plasma triacyglycerol response study on day 22, feeding of sugar-beet-pulp-containing diets generally reduced postprandial triacylglycerol concentrations and delayed triacylglycerol response relative to chickens given the control diets either ad lib. or restricted, which may indicate gastrointestinal adaptation to feeding of a fibre-rich diet. Postprandial triacylglycerol concentrations observed for chickens receiving restricted diets were increased compared with chickens given the respective ad lib. diets, indicating adaptation of chickens to reduced feed frequency. On day 25, feeding of sugar-beet-pulp-containing diets decreased digesta dry matter content and ileal organic matter digestibility. Chickens given sugar-beet-pulp-containing diets generally had, on day 25, increased caecal short-chain fatty acid (SCFA) concentrations in comparison with chickens given the ad lib. control diet, indicating increased fermentation of dietary components. It is also noteworthy that the greatest SCFA concentrations were observed amongst chickens given the control diet once daily, suggesting enhanced caecal fermentation capacity. This may have been a consequence of increased bacterial activity and caecal hypertrophy due to infrequent feeding of a low-fibre diet.

Animals↗

PubMed2003

Associations between intake of added sugars and intakes of nutrients and food groups in the diets of German children and adolescents.

The aim of the present analysis was to evaluate the effect of intake of added sugars on intakes of nutrients and food groups. We used a mixed linear model (PROC MIXED) to analyse data from the Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) study (an ongoing longitudinal cohort study between infancy and adulthood). Between July 1985 and August 2001, 3 d weighed dietary records (n 4993) from 849 children and adolescents (416 male, 433 female) aged 2-18 years were collected and evaluated. Overall mean intake of added sugars was 12.4 (SD 5.3) (median 12.0) % energy. Fat intake (% energy) and intake of all analysed nutrients (as % reference values for nutrient intakes) fell across quintiles 1-5 of energy intake from added sugars (P<0.001). With the exception of 'Sugary foods' and 'Beverages' (significant increase, P<0.0001) and 'Dairy' (NS), intake of all other food groups decreased with increasing intake of added sugars (P<0.0001). In conclusion, we found a slight, but statistically significant, nutrient-dilution effect of added sugars and a significant reduction in intake of important nutrient-bearing food groups. However, the DONALD study gives no clear indicator on grounds of micronutrient dilution for a quantitative limit on intake of added sugars.

Adolescent↗

PubMed1991

Development of sugar-induced blood pressure elevation after uninephrectomy in a resistant rat strain.

Certain rat strains acutely increase blood pressure (BP) when given diets high in NaCl. Prior results showed that "salt-sensitive" rat strains, at least the ones studied, also increase BP in response to sugar loading. To examine this relationship further and learn more about the pathogenesis of sucrose-induced BP elevations, we examined the effects of unilateral nephrectomy (uninephrectomy) on sucrose-induced BP changes. The rationale is based upon the findings that renal mass removal sensitizes BP response to salt loading. Over 15 weeks, augmented sugar (sucrose) consumption by Long-Evans (LE) rats did not increase BP markedly compared to rats consuming a diet relatively low in sugar unless uninephrectomy was performed. The differences in BP caused by the high sugar diet in a uninephrectomized rat could not be explained adequately by alterations in catecholamine excretion, plasma renin activity, excesses in blood volume, or the other parameters examined. However, salt-induced hypertension has been attributed to the presence of circulating substances affecting ion transport. Among the dietary groups, there was a significant correlation between the ability of plasma to depress PAH and TEA renal slice uptake and the difference in BP. This is consistent with the presence of a circulating factor affecting cell transport that has its greatest activity in the high sugar-uninephrectomy group of LE rats. We conclude that reducing renal mass potentiates sugar-induced BP elevation similar to salt-induced BP elevation in a normally resistant rat strain, and the rise of BP may be caused by a circulating factor.

Aging↗

PubMed2001

The role of added sugars in the diet quality of children and adolescents.

OBJECTIVE: The associations between added sugars intake and consumption of vitamins, minerals and servings of foods in the USDA Food Guide Pyramid were examined. METHODS: Data from the USDA 1994-96 Continuing Survey of Food Intakes by Individuals were used in multivariate regression analyses to assess the statistical and practical significance of added sugars intake for diet and nutrient adequacy. RESULTS: The association of added sugars with consumption of vitamins, minerals and servings of foods in the USDA Food Guide Pyramid was usually statistically significant. For the model of all individuals over two years of age, individuals who consume more added sugars are predicted to consume more grains, lean meat and iron and to consume fewer vegetables and fruits and less dairy, vitamin A, calcium and folates. Children who consume more added sugars are predicted to consume more grains, vitamin C, iron and folates and to consume less dairy. Adolescents who consume more added sugars are predicted to consume more grains, vitamin C and iron and less fruit. CONCLUSION: The associations, whether positive or negative, however, were always small from either a practical perspective or in comparison to the associations of other sources of energy.

Adolescent↗

PubMed1979

Radiation-induced DNA strand breaks in deoxygenated aqueous solutions. The formation of altered sugars as end groups.

Gamma irradiation of DNA in deoxygenated, N2O-saturated aqueous solution leads to three bound altered sugars present as end groups in broken DNA strands. These sugars are linked to the DNA by phosphoric acid ester bonds. Two of the end groups have the structures (4) and (5). (Formula: see text) The third end group after dephosphorylation has structure (3). The formation of the bound sugars (4) and (5) is explained by a mechanism postulated earlier for the formation of free altered sugars. Except for the phosphoric acid ester linkage, the free altered sugars have the same chemical structures as the bound altered sugars.

Chemical Phenomena↗

PubMed1999

The effect of temperature on water vapor sorption by some amorphous pharmaceutical sugars.

To determine the effect of temperature on the water vapor sorption behavior of some amorphous pharmaceutical sugars, aqueous solutions of sucrose, lactose, trehalose, and raffinose were freeze-dried using a conventional laboratory lyophilizer. The amorphous sugars formed were stored for several months at 5, 30, and 50 degrees C and at a range of relative humidities (0-90% RH). After equilibration the extent of water vapor sorption was determined gravimetrically, and the presence of any crystalline material was determined. A significant amount of water was sorbed by each of the amorphous sugars even at moderate humidities. In every system studied, lowering the storage temperature at any given relative humidity caused an increased quantity of water to be sorbed. This indicated the predominance of an exothermic water vapor sorption process. Spontaneous crystallization of all the sugars occurred at elevated RHs, and the onset of crystallization did not necessarily coincide with attainment of the water content of the final crystalline forms(s) or the reduction of the sugars' glass transition temperature to ambient conditions. Notably, the amorphous and crystalline forms of some sugars were able to coexist in a quasi-equilibrium state under certain temperature and humidity conditions.

Absorption↗

PubMedDate not supplied

[Energetic utilization of sugar beets, dried shreds, sucrose and apple pectin by growing swine. 1. Study overview and composition and digestibility of feed and rations].

Total metabolism experiments with a basic ration were carried out over two measuring periods and with a basic ration plus supplements of raw sugar beets, steamed sugar beets, dried sugar beet pulp, sucrose and apple pectin resp. with 4 pigs per test group and 4 test groups (LW 40-135 kg). Live weight gain was approximately equal after the feeding of raw and steamed sugar beets. It amounted to 650 g/animal and day in the first experimental period and to 715 g in the second. After feeding dried sugar beet pulp as supplement the corresponding weight gain was 525 and 565 g/animal and day. In the course of the ontogenetic development up to a live weight of about 70 kg an increase of digestibility could be observed. Adaptation cannot be excluded. This question will be pursued in the following experiments, so that consequences for energetic feed evaluation have to be postponed. For both raw and steamed sugar beets the digestibility of the organic matter was 88%, of NFE 95% and of water soluble carbohydrates 95%.

Animal Feed↗

PubMed1999

Sugar-branched-cyclodextrins as injectable drug carriers in mice.

The purpose of this study was to investigate stable complexation of drug in blood by sugar-branched-beta-cyclodextrins (beta-CDs) such as glucose (glu)- or galactose (gal)-branched-beta-CDs and the pharmacokinetic disposition of drug in sugar-branched-beta-CD complex. Complexation of steroidal drugs in sugar-branched-beta-CDs and their replacement by cholesterol were measured. The complexes of dexamethasone/glucosyl-beta-CDs (dexamethasone/glu-beta-CD or dexamethasone/glu-glu-beta-CD) were not replaced by cholesterol, which is a representative endogenous compound, whereas the complex of dexamethasone/beta-CD was replaced by cholesterol. The same results were obtained in steroidal drugs such as hydrocortisone, triamcinolone, and prednisolone. Thus, the use of glu-beta-CD and glu-glu-beta-CD permitted the stable complexation of the drug in water. Stability constants of dexamethasone/glu-glu-beta-CD and dexamethasone/gal-glu-beta-CD complexes are the same, which means that the sugar moiety of the side chain in beta-CD has little effect on stability constants. After the dexamethasone/gal-glu-beta-CD complex or the dexamethasone/glu-glu-beta-CD complex (dexamethasone: 1 mg/body) was administered intravenously to mice, dexamethasone concentrations in liver tissue and blood were measured. The dexamethasone/gal-glu-beta-CD complex (66.1 +/- 1.7 micrograms as dexamethasone/gram of liver tissue) was distributed to liver tissue significantly more than the dexamethasone/glu-glu-beta-CD (beta-CD) complex (59.9 +/- 1.0 micrograms as dexamethasone/gram of liver) at 30 min after administration (p < .05). Sugar-branched-beta-CD gave a water-soluble and stable complex for dexamethasone and changed the disposition of dexamethasone. Sugar-branched-beta-CDs are potentially excellent carriers for a steroidal injectable formulation.

Animals↗

PubMed2005

Probing the geometry of the inner vestibule of BK channels with sugars.

The geometry of the inner vestibule of BK channels was probed by examining the effects of different sugars in the intracellular solution on single-channel current amplitude (unitary current). Glycerol, glucose, and sucrose decreased unitary current through BK channels in a concentration- and size-dependent manner, in the order sucrose > glucose > glycerol, with outward currents being reduced more than inward currents. The fractional decrease of outward current was more directly related to the fractional hydrodynamic volume occupied by the sugars than to changes in osmolality. For concentrations of sugars < or =1 M, the i/V plots for outward currents in the presence and absence of sugar superimposed after scaling, and increasing K(+)(i) from 150 mM to 2 M increased the magnitudes of the i/V plots with little effect on the shape of the scaled curves. These observations suggest that sugars < or =1 M reduce outward currents mainly by entering the inner vestibule and reducing the movement of K(+) through the vestibule, rather than by limiting diffusion-controlled access of K(+) to the vestibule. With 2 M sucrose, the movement of K(+) into the inner vestibule became diffusion limited for 150 mM K(+)(i) and voltages > +100 mV. Increasing K(+)(i) then relieved the diffusion limitation. An estimate of the capture radius based on the 5 pA diffusion-limited current for channels without the ring of negative charge at the entrance to the inner vestibule was 2.2 A. Adding the radius of a hydrated K(+) (6-8 A) then gave an effective radius for the entrance to the inner vestibule of 8-10 A. Such a functionally wide entrance to the inner vestibule together with our observation that even small concentrations of sugar in the inner vestibule reduce unitary current suggest that a wide inner vestibule is required for the large conductance of BK channels.

Animals↗

PubMed1964

ION TRANSPORT IN ISOLATED RABBIT ILEUM. II. THE INTERACTION BETWEEN ACTIVE SODIUM AND ACTIVE SUGAR TRANSPORT.

The addition of actively transported sugars to the solution bathing the mucosal surface of an in vitro preparation of distal rabbit ileum results in a rapid increase in the transmural potential difference, the short-circuit current, and the rate of active Na transport from mucosa to serosa. These effects are dependent upon the active transport of the sugar per se and are independent of the metabolic fate of the transported sugar. Furthermore, they are inhibited both by low concentrations of phlorizin in the mucosal solution and by low concentrations of ouabain in the serosal solution. The increase in the short-circuit current, DeltaI(sc), requires the presence of Na in the perfusion medium and its magnitude is a linear function of the Na concentration. On the other hand, DeltaI(sc) is a saturable function of the mucosal sugar concentration which is consistent with Michaelis-Menten kinetics suggesting that the increase in active Na transport is stoichiometrically related to the rate of active sugar transport. An interpretation of these findings in terms of a hypothetical model for intestinal Na and sugar transport is presented.

Animals↗

PubMedDate not supplied

Sugar digestion efficiencies of Gurney's sugarbirds, malachite sunbirds, and black sunbirds.

This study determined the interaction between energy assimilation and digestive constraints on the foraging behaviour of nectarivorous Gurney's sugarbirds (Promerops gurneyi), black sunbirds (Nectarinia amethystina), and malachite sunbirds (Nectarinia famosa) in the laboratory. Rates of sugar intake and consumption, transit time, and the concentration of sugar in the excreta were measured when birds were fed 0.25 mol L-1 sucrose, 0.73 mol L-1 sucrose, and 0.73 mol L-1 glucose. For each species, intake rates by volume were greater at low sugar concentrations, such that energy intakes per 90 min were similar, irrespective of diet, which supports the idea of regulated energy intake for these nectarivorous birds. All species were efficient at energy extraction, excreting 1% or less sucrose equivalent irrespective of the initial sugar concentration of each diet. Transit times of solutions ingested increased with an increase in sugar concentration. Birds maximized energy assimilation on high- and low-energy nectar diets by having high extraction efficiencies and short transit times. Sugarbird and sunbird foraging behaviours may be limited by digestive processes and the cost of carrying high-energy reserves as nectar sugar concentration increases.

Animals↗

PubMed1995

Digestion and metabolism of sugars.

Many factors potentially influence the digestion, absorption, and metabolism of the various species of sugars occurring in the human diet. Experimental evidence indicates that the source of sugars in foods does not in itself affect the rate of absorption or the metabolism of the sugars. However, the form in which the sugars are ingested and the physical and chemical properties of the food matrices do have significant effects on the rates of absorption. Food matrices influence gastric emptying and through their physical properties affect the rate of transport across the small intestinal mucosa. Disaccharides form the major proportion of ingested carbohydrates in the small intestine and the digestion and transport systems for these sugars, except for lactose, are the most efficient. After absorption, the pathways of the different dietary sugars converge and the original dietary source has only minimal effects on metabolism.

Dietary Carbohydrates↗

PubMed1995

Sugars and blood glucose control.

The rise of blood glucose in normal and diabetic subjects after meals varies markedly and depends on many factors, including the source of the carbohydrate, its method of preparation, and the composition of the total meal. Classification of carbohydrates as simple or complex does not predict their effects on blood glucose or insulin. Rapidly absorbed carbohydrates, which produce large blood glucose and insulin responses, may be in the form of both sugars and starches. Sugars added to foods have no different effect on blood glucose from those of sugars alone. The natural sugars in fruit and fruit juices raise blood glucose approximately as much as does sucrose and less than do most refined starchy carbohydrate foods. The optimum amount of sugars in the diet is not known. However, undue avoidance of sugars is not necessary for blood glucose control and is not advised because it may result in increased intakes of fat and high-glycemic-index starch.

Blood Glucose↗

PubMed1995

Sugar and body weight regulation.

The need to understand reasons for the high prevalence of obesity in developed countries has led to examination of dietary habits that may contribute to obesity. We consider whether consumption of high amounts of sugars presents a public health problem by contributing to the development of obesity. Metabolic studies show that diets high in fat are more likely to result in body fat accumulation than are diets high in carbohydrate. There is no indication that simple sugars differ from complex sugars in this regard. Epidemiologic data show a clear inverse relation between intake of sugar and fat. Further, although high intake of dietary fat is positively associated with indexes of obesity, high intake of sugar is negatively associated with indexes of obesity. There is ample reason to associate high-fat diets with obesity but, at present, no reason to associate high-sugar diets with obesity.

Body Weight↗