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PubMed1976

[Sugar substitutes in the diabetic diet].

The decreased glucsoe utilization in diabetes mellitus justifies the use of sugar substitutes ("diabetic sugar") if two conditions are fulfilled: 1)The sugar substitute should be a carbohydrate which does not lead, or only to a slight degree, to hyperglycaemia and thus, in this respect, differs distinctly from sugars such as glucose and saccharose. 2) The sugar substitute must not cause undesired side-effects. The absorption, utilization and side-effects of the sugar substitutes fructose, sorbitol and xylitol were investigated. They were found to be more slowly absorbed than glucose and thus to offer the advantage of better utilization under conditions of limited insulin production. However, the particularly slow passive absorption of sorbitol and xylitol can sometimes be a disadvantage, since osmotic diarrhoea may occur after administration of high oral doses. The sugar substitutes enter the metabolism enzymatically and are utilized mainly in the liver. The peripheral state was investigated after intravenous, intraduodenal and oral administration of glucose and fructose to healthy subjects. Liver metabolism was examined (Dietze) by comparing hepatic venous and arterial concentrations after intravenous administration of the sugars. Also, diabetic patients received glucose and fructose orally. As previously demonstrated, the investigations using several techniques showed a smaller influence on blood glucose and serum insulin concentrations after administration of fructose, sorbitol and xylitol than after glucose. If no metabolic changes occur after intravenous administration of high doses, no such changes need be expected after oral administration of small doses. Nor did measurements in hepatic venous blood (Dietze) show any marked effect of fructose on the blood glucose level. The healthy subjects showed no significant changes in blood glucose or serum insulin concentration after either intraduodenal or oral administration of fructose, whereas they showed a considerable increase after glucose administration. Investigations in adult-type diabetics revealed a better utilization of fructose than glucose. With correct dosage, sugar substitutes are able to increase the carbohydrate tolerance and, under certain conditions, to achieve a relative stabilization of the metabolism of unstable diabetics. The antiketogenic activity of sugar substitutes is particularly pronounced. Side-effects such as high blood levels of urea, lactate, triglycerides and bilirubin or a decrease in hepatic adenin nucleotides do not occur after oral administration, nor are they of importance after intravenous administration with correct dosage. The osmotic diarrhoea occurring after intake of sorbitol or xylitol is caused by their slow absorption and limits the consumption of these sugar substitutes. In the often obese adult-type diabetics, the calorie intake inherent in the consumption of diabetic sugars may have an unfavourable influence on their weight...

Adult↗
PubMed1978

Dual effect of adrenalin on sugar transport in rat diaphragm muscle.

The effect of adrenalin on the membrane transport of the non-metabolized sugar, 3-methylglucose, was studied in isolated "intact" rat hemidiaphragms and related to simultaneously occurring changes in the internal levels of Na+, ATP, glucose-6-P, glycerol formation and 45Ca uptake and loss. Basal sugar transport was inhibited by low (10-8-10-5 M) concentrations of adrenalin; this was antagonized by propranolol and practolol. High concentrations (10-4-10-3 M) stimulated sugar transport, and this was blocked by propranolol and butoxamine and was dependent on external Ca2+. These results suggest interaction with two different classes of adrenergic receptors, possibly of beta 1 and beta 2 types. Both low and high concentrations increases Na+ and K+ gradients by a practolol-sensitive effect. Isoproterenol behaved identically but phenylephrine had only the two practolol-sensitive effects on sugar and ion transport. Insulin did not interfere with inhibition of sugar transport and decrease in internal Na+ but prevented stimulation of sugar transport. Under anoxia adrenalin had no effect on sugar transport but led to greater Na+ gain by tissue. Addition of 3.0 mM palmitate decreased inhibition of sugar transport without changing receptor specificity. ATP was decreased and lipolysis enchanged by high adrenalin but glucose-6-P was increased by the low concentration as well. Influx of 45 Ca was decreased by low and increased by high adrenalin; 45Ca efflux was also differentially affected. The results indicate that inhibition and stimulation of sugar transport depend on different receptors and that the latter response may override the former. The data are consistent with the earlier postulated regulatory role of sarcoplasmic Ca2+ on sugar transport in muscle, with adrenalin affecting Ca2+ fluxes and distribution both directly and indirectly.

Animals↗
PubMed1979

Reduction in mutagenicity of cigarette smoke condensate by added sugars.

The effects of adding sugars to high- and low-tar cigarettes on the mutagenicity of their smoke condensates were studied using Salmonella typhimurium TA100 and TA98 with and without metabolic activation. The sugars tested were glucose, fructose, galactose, sorbitol, sucrose and lactose. The lowest mutagenicities observed with these sugars per mg of smoke condensate assayed on TA98 with metabolic activation were 37% (high-tar cigarettes) and 22% (low-tar cigaretts) of that of smoke condensate from untreated cigarettes. Addition of sugars increased the total amounts of smoke condensates, but the mutagenicities of the total condensates were also decreased by all the sugars, the lowest values being 35% (high-tar cigarettes) and 36% (low-tar cigarettes) of that of smoke condensates from cigarettes without added sugar. On assay with TA100 with metabolic activation, decreases in both specific and total mutangenicities of condensates of high-tar cigarettes were observed with all the sugars tested except galactose and sucrose. Treatment with glucose, fructose or sorbitol decreased the specific mutagenicity of condensates of low-tar cigarettes and glucose and fructose reduced also their total mutagenicity. The effects of added sugars were more marked when assayed on TA98 than on TA100 and of the sugars tested fructose and sorbitol had the greatest effects. Addition of sugars had no effect of the mutagenicity of cigarette-smoke condensate without metabolic activation.

Carbohydrates↗
PubMed1979

Determination of endotoxins in sugar with the Limulus test.

The Limulus amebocyte lysate test has been used for determination of pyrogens in sugar of different qualities. All the samples of domestic white sugar and beet raw sugar produced in Sweden during 1976 had a very low content of endotoxins, less than 10 ng/g of sugar. Imported cane raw sugar was, however, highly contaminated. The highest value obtained corresponds to about 100 mg of Escherichia coli endotoxin per g of raw sugar. Such crude sugar cannot, even after refining, be used for medical purposes. Instead, Swedish beet sugar is used as the raw material for production of invert sugar solutions for parenteral administration. The amount of endotoxin in this sugar is less than 1 ng/g.

Carbohydrates↗
PubMed1978

Catabolite inhibition and sequential metabolism of sugars by Streptococcus lactis.

Growth of galactose-adapted cells of Streptococcus lactis ML(3) in a medium containing a mixture of glucose, galactose, and lactose was characterized initially by the simultaneous metabolism of glucose and lactose. Galactose was not significantly utilized until the latter sugars had been exhausted from the medium. The addition of glucose or lactose to a culture of S. lactis ML(3) growing exponentially on galactose caused immediate inhibition of galactose utilization and an increase in growth rate, concomitant with the preferential metabolism of the added sugar. Under nongrowing conditions, cells of S. lactis ML(3) grown previously on galactose metabolized the three separate sugars equally rapidly. However, cells suspended in buffer containing a mixture of glucose plus galactose or lactose plus galactose again consumed glucose or lactose preferentially. The rate of galactose metabolism was reduced by approximately 95% in the presence of the inhibitory sugar, but the maximum rate of metabolism was resumed upon exhaustion of glucose or lactose from the system. When presented with a mixture of glucose and lactose, the resting cells metabolized both sugars simultaneously. Lactose, glucose, and a non-metabolizable glucose analog (2-deoxy-d-glucose) prevented the phosphoenolpyruvate-dependent uptake of thiomethyl-beta-d-galactopyranoside (TMG), but the accumulation of TMG, like galactose metabolism, commenced immediately upon exhaustion of the metabolizable sugars from the medium. Growth of galactose-adapted cells of the lactose-defective variant S. lactis 7962 in the triple-sugar medium was characterized by the sequential metabolism of glucose, galactose, and lactose. Growth of S. lactis ML(3) and 7962 in the triple-sugar medium occurred without apparent diauxie, and for each strain the patterns of sequential sugar metabolism under growing and nongrowing conditions were identical. Fine control of the activities of preexisting enzyme systems by catabolite inhibition may afford a satisfactory explanation for the observed sequential utilization of sugars by these two organisms.

Biological Transport↗
PubMed1977

Sugar interaction with the antiluminal surface of the proximal tubule in dog kidney.

The pulse-injection multiple-indicator-dilution technique in vivo has been used to investigate bidirectional sugar interaction with the antiluminal surface of the nephron in dog kidney. Simultaneous renal vein and urine outflow curves were obtained for radiolabeled sugars known to interact with the antiluminal surface. The following sugars were tested relative to T-1824 albumin (plasma reference) and creatinine (extracellular reference) under conditions of high-dose phlorizin preloading (75-225 mg/kg): D-glucose, D-xylose, D-fucose, D-mannose, D-galactose, L-arabinose, myoinositol, and D-fructose. The results indicate that as the plasma concentration of phlorizin increases there is, first, a partial inhibition of sugar interaction at the antiluminal membrane so that only unidirectional uptake of sugar from blood to tubular cell is observed, followed by complete inhibition of sugar interaction at the peritubular face of the antiluminal membrane, resulting in superposition of sugar and creatinine curves in the renal vein effluent. Two possible interpretations exist. i) Phlorizin exerts its inhibitory action successively at the cytoplasmic and then at the peritubular face of the antiluminal membrane. Moreover, since all of the sugar substrates are inhibited by phlorizin, the data suggest that the sugar-membrane interaction takes place at a common site at the level of the proximal tubule. ii) Alternatively, the action of phlorizin could result from a metabolic inhibitory effect affecting multiple sugar transport systems at the antiluminal membrane.

Animals↗
PubMed2026

Phosphorylation and ubiquitination coordinate homeostasis of a tomato transporter responsible for fruit sugar accumulation.

Sugar transport mediated by different transporters is essential for maintaining sugar homeostasis in plants. Here, we report that phosphorylation and ubiquitination coordinate the homeostasis of a tomato (Solanum lycopersicum) sugar transporter SlSWEET16, revealing a new aspect of plant sugar homeostasis. SlSWEET16 is localized to plasma membrane and functions as a mono- and disaccharide transporter. SlSWEET16 mediates cellular sugar efflux, and CRISPR/Cas9-mediated knockout of SlSWEET16 leads to increased fruit sugar accumulation. Strikingly, the C-terminus of SlSWEET16 is subjected to both phosphorylation and ubiquitination. Two protein kinases including SlSnRK2.3 and SlSnRK2.4 associate with the C-terminus of SlSWEET16, resulting into an increase in the stability of SlSWEET16. Meanwhile, the C-terminus of SlSWEET16 also interacts with an E3 ubiquitin ligase SlTT3.1L2, which decreases the stability of SlSWEET16. SlSnRK2.3 and SlSnRK2.4 inhibit fruit sugar accumulation, whereas SlTT3.1L2 promotes it. Mutations of phosphorylated or ubiquitinated residues in SlSWEET16's C-terminus further corroborate the contribution of phosphorylation and ubiquitination to the stability of SlSWEET16 and fruit sugar accumulation. Our results reveal a multiple-protein regulatory module that integrates different post-translational modifications to control transporter-mediated fruit sugar accumulation.

Solanum lycopersicum↗
PubMed1979

Preparatively useful reactions involving nitrogenous sugars and some applications with carbohydrate-containing antibiotics.

This work describes the development of useful synthetic methodology with simple sugars, practical applications for conversion of abundant precursors into modified sugars (especially amino and deoxy sugars) of importance in various groups of natural products, and the conversion of such products into compounds of biological or pharmacological interest, especially carbohydrate antibiotics and their analogs. Examples of synthetic methodology illustrate various routes to deoxygenated (saturated, alkenic, and acetylenic), and oxidized (carbonylic, aldehydic, and carboxylic) functionality from hydroxyl and amino precursors. Unusual modes of sugar protection by such procedures as kinetic acetonation are discussed, together with the use of diazo and hydrazino groups for access to novel structures, including extended carbon-chain sugars and sugar--heterocycle conjugates. The broad utility of 5-membered benzylidene acetals in regiospecific routes to alpha, beta-deoxycarbonyl sugars is the basis of general methodology for practical, large-scale synthesis of aminopolydeoxy sugars, with daunosamine as the prototype, of widely varied substitution-mode and stereochemistry. Implications of the foregoing are discussed in relation to several classes of antibiotics, especially the anthracyclines and analogs thereof. A range of 7-O-(amino sugar-substituted)daunomycinones have been synthesized, together with 3'-hydroxy-daunorubicin and adriamycin, and their antitumor and toxicological properties evaluated; prospects for useful total synthesis will be mentioned.

Amino Sugars↗
PubMed1976

Sugar binding to purified fractions from bovine taste buds and epithelial tissue. Relationships to bioactivity.

Binding of various sugars was compared in purified subfractions of taste buds isolated from bovine circumvallate papillae and of non-taste bud-bearing epithelium isolated from tissue surrounding these papillae. Binding of 14C-labeled sugars was greater in purified subfractions obtained from taste bud than from non-taste bud-bearing tissue and was, in general, greater in those taste bud subfractions in which a greater membrane purification was achieved. Binding specificity of the 14C-labeled sugars sucrose, fructose, glucose and of 14C-labeled cyclamate and saccharine was measured by competition of each 14C-labeled sugar or synthetic sweetener with its unlabeled homologous sugar in P4(B) taste bud subfractions; this binding, as shown for sucrose, was reversible and temperature dependent. Essentially no competition of the 14C-lageled sugars sucrose, fructose, glucose or 14C-labeled cyclamate and saccharine by their respective unlabeled homologues occurred in epithelial tissue P4(B) subfractions; this binding was not reversible. Binding specificity was further observed by the competition of 14C-labeled sucrose, fructose and glucose with each unlabeled sugar for binding sites on P4(B) taste bud subfractions; unlabeled sucrose was more effective in competing with each 14C-labeled surgar than was unlabeled fructose or glucose. The relatively non-sweet sugar lactose did not compete with 14C-labeled lactose in P4(B) subfractions from either taste bud or non-taste bud-bearing epithelial tissue. Binding of 14C-labeled sucrose in purified P4(B) bud subfractions was inhibited by increased concentrations of unlabeled sucrose, phospholipase C, neuraminidase, EDTA, NaCl and urea. Dissociation constants for sugar or synthetic sweetener binding were low (approx. 10(-3) M) but in a rank order (sucrose greater than fructose greater than glucose greater than saccharine) consistent with preference and electrophysiological responses in cow. The cow is behaviorally indifferent to saccharine and lactose consistent with the data obtained in the present study.

Animals↗
PubMed1978

Regulation of the synthesis of M protein by sugars, Todd Hewitt broth, and horse serum, in growing cells of Streptococcus pyogenes.

Various sugars were tested for their effect on the differential rate of synthesis of M protein during the growth of Streptococcus pyogenes strain 0055 M12T12. In a semisynthetic medium alone, a high rate of M protein synthesis occurred with glucose as a substrate; decreasing rates of synthesis occurred with sucrose and trehalose, in that order, although the rates of growth were approximately equal with all sugars. A period of derepressed synthesis of M protein occurred in the lag phase of growth and in the stationary period as the substrates were being depleted. Although glucose inhibited the utilization of other sugars, diauxie was not apparent from the growth curves. However, synthesis of M protein followed strong diauxie curves with a reduction in rate of synthesis during the utilization of the second sugar. With glucose as a substrate, 2-deoxyglucose showed a strong permanent repression of M protein synthesis, whereas both glucose and 2-deoxyglucose caused temporary repression when sucrose was the substrate. Horse serum increased the rate of synthesis of M protein in a manner very similar to that caused by adding cyclic AMP, although quantitative analyses suggested that cyclic AMP, per se, was not the effector in horse serum. Addition of Todd Hewitt broth permitted the organisms to grow on phosphorylated sugars. Although the rates of growth on phosphorylated sugars were similar to that obtained with glucose, M protein was not synthesized when a phosphorylated sugar was the sole substrate. The addition of phosphorylated sugars with glucose or sucrose as substrates strongly repressed the synthesis of M protein with glucose-1-phosphate and with fructose 1,6-diphosphate repressing M protein synthesis the most. Clearly, M protein synthesis, which was not required for growth, was preferentially induced by glucose as compared to the other sugars and was dependent upon the metabolic route by which glucose was utilized.

Animals↗
PubMed2026

Metabolomics-based authentication of acacia honey against C3 and C4 sugar adulteration.

Acacia (Robinia pseudoacacia) honey is frequently adulterated with low-cost alternatives via direct syrup addition or in-hive sugar feeding. We focused on sugar-feeding adulterants, which is difficult to distinguish from nectar-based honey. Stable carbon isotope ratio analysis (SCIRA) is an established method for assessing honey authentication; however, its applicability is limited to detecting C4 plant-derived sugar adulteration. Therefore, we developed a metabolomics-based multi-marker strategy to discriminate acacia honey from beet-sugar (C3)- and cane-sugar (C4)-fed honey. Thirteen metabolites were prioritized using combined multivariate and univariate criteria. Subsequently, 1716 panels of seven-marker (13C7) were evaluated for discrimination performance. 291 panels achieved 100% accuracy in an independent validation set. In blending scenarios, acacia honeys spiked with 20% beet-sugar-fed honey and 20% cane-sugar-fed honey were successfully identified, outperforming SCIRA (60%) and beet-sugar marker 3-methoxytyramine (3-MT) (30%). These findings establish metabolomic panels as a robust marker for acacia honey authentication, extending beyond current reference methods.

Acacia↗