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PubMed1989

The effect of ponalrestat on sorbitol levels in the lens of obese and diabetic mice.

Sorbitol levels were determined in lens of genetically obese (ob/ob) and diabetic (db/db) mice, as well as in lean mice (+/db, +/ob) made diabetic by administration of streptozotocin (STZ). Treatment of lean mice with STZ resulted in hypoinsulinemia, whereas the ob/ob and db/db mice were hyperinsulinemic. Hyperglycemia was present in STZ-treated +/db and +/ob mice and in db/db mice, whereas relative euglycemia was observed in ob/ob mice and untreated +/db and +/ob mice. Sorbitol levels were elevated in lens tissue of db/db mice and STZ-treated +/db. In contrast, no changes in sorbitol content were observed in ob/ob mice and +/ob mice treated with STZ, suggesting that aldose reductase activity in lens of this animal model is considerably less than that present in db/db mice. Oral treatment of db/db mice and STZ-treated +/db mice with Ponalrestat reduced hyperglycemia-induced sorbitol accumulation significantly in lens, indicating that aldose reductase inhibitors may ameliorate long-term complications associated with sorbitol accumulation in diabetes.

Aldehyde Reductase↗
PubMed1989

Oral baicalin and liquid extract of licorice reduce sorbitol levels in red blood cell of diabetic rats.

Intracellular accumulation of sorbitol, resulting from the increased glucose flux through polyol pathway with the action of aldose reductase, has been found pathogenic to chronic diabetic complications. It has been reported that baicalin and Glycyrrhiza uralensis Fisch can inhibit rat lens aldose reductase in vitro. In order to determine whether the said medicinal herbs give the inhibitive effect in vivo, 10 streptozotocin induced diabetic rats were treated with baicalin 150 mg/kg.d and liquid extract of licorice (LEL) 7.5 ml/kg.d for a week. RBC sorbitol was determined by a fluorometric assay before and after the treatment, as well as one week afterwards. It was found that oral baicalin and licorice dramatically reduced sorbitol levels in RBC without affecting blood glucose levels. The sorbitol levels was restored to its original values one week after discontinuing the treatment. The present study has demonstrated the effectiveness of baicalin and licorice in reducing RBC sorbitol levels in diabetic rats. Its mechanism is presumably through inhibition of aldose reductase. The feasibility of its clinical application for the control of diabetic complications is under investigation.

Animals↗
PubMed1988

Determination of D-sorbitol in human erythrocytes by an improved enzymatic method with fluorometric detection.

In this enzymatic method to analyze erythrocytes for D-sorbitol, the erythrocytes were separated from plasma by centrifugation, washed with isotonic saline (9 g/L NaCl), then diluted threefold with more saline. We lysed 1.5 mL of the diluted erythrocytes with chloroform and precipitated the protein with 58 g/L HClO4 solution. The resulting supernates were mixed with buffer, NAD+, and sorbitol dehydrogenase (EC 1.1.1.14). For standards, we added sorbitol to the erythrocytes before lysing. After 25 min of incubation at 37 degrees C, the fluorescence responses were recorded. Results for sorbitol were corrected for sample-blank and enzyme fluorescence, and were then normalized for hemoglobin content. Response was linear for a sorbitol concentration range of 1 to 30 mumol/L. Reproducibility was good, with an average CV of 2.5% at 10 mumol/L. Results for healthy individuals and diabetic patients are presented.

Blood Glucose↗
PubMed1986

Sorbitol clearance: a parameter reflecting liver plasma flow in the rat.

According to the clearance concepts, the functional liver plasma flow may be directly measured from the plasma kinetics of any substance whose hepatic intrinsic clearance largely exceeds liver perfusion. The present study was designed to ascertain the requirements for the reliability of D-sorbitol plasma clearance in evaluating changes of liver perfusion in the male Wistar rat. The plasma disappearance curve of D-sorbitol (3 mg/100 g b.w. by bolus i.v. injection) followed a first order kinetics and fitted a two-compartment model. Very similar estimates of D-sorbitol plasma clearance were obtained by applying the area under the curve method to data obtained by the trapezoidal rule and by compartmental analysis. D-sorbitol hepatic extraction was almost complete in controls and in rats submitted to porta-caval shunt and hepatic artery ligation, while significantly decreased after partial hepatectomy. Renal output never exceeded 10% of the administered amount. No in-vivo diffusion into red cells was observed. In controls, the functional liver plasma flow, as measured by D-sorbitol clearance was 2.83 +/- 0.68 ml/min/100 g (mean +/- SD). Significantly lower values were found in rats submitted to porta-caval shunt (1.19 +/- 0.38), hepatic artery ligation (2.06 +/- 0.53), and partial hepatectomy (1.03 +/- 0.44).

Animals↗
PubMedDate not supplied

[Sorbitol pathway of glucose metabolism in streptozotocin diabetes of varying duration and severity].

The degree of accumulation of sorbitol pathway metabolites by the lens, sciatic nerve and aorta is determined by the duration and gravity of experimental diabetes. As the blood glucose content (indicating experimental diabetes gravity) rises, the aldose reductase activity in the tissues increases, the content of sorbitol and fructose ascends. The sorbitol-dehydrogenase activity does not depend on diabetes gravity. An increase of aldose reductase and a decrease in the sorbitol-dehydrogenase activity occur within the first two weeks after diabetes induction, which correlates with the maximal rate of sorbitol and fructose accumulation. The conclusion is made on the necessity of a strict compensation for diabetes to prevent the development of chronic complications.

Aldehyde Reductase↗
PubMed1982

[Varying utilization of glucose and sorbitol in drug-induced hypercortical metabolism].

Utilisation of glucose and sorbitol in medically induced hypercorticalic states was investigated by means of the steroid-glucose-tolerance-test (SGTT) in 9 children, aged 6-16 years suffering from obesity and prediabetes. Prednisolone (1 mg/kg up to 20 mg) was applied 9 and 3 h prior to the loading tests. Blood samples were taken 0, 2, 5, 30, 60, 90, 120, 150 and 180 min after the onset of the loading tests. During the intravenous infusion of glucose (initial 0,33 g/kg followed by 12 mg/kg/min through 2 h) the mean blood glucose values increased from 103 +/- 15,5 to 388 +/- 96,6 mg/100 ml. Decrease of glycemia began delayed after 90 min, and did not approach the 180 min normal values in 3 of 9 patients. In analogous sorbitol-loading tests performed 2 to 6 days later blood glucose rose from 93 +/- 16,6 mg/100 ml to 129 +/- 28,7 mg/100 ml only. There was a significantly higher blood glucose level on SGTT as compared to steroid-sorbitol loading through the whole test period. Renal losses of glucose after SGTT as well as sorbitol losses after steroid-sorbitol loading amounted to approximately 14% of the doses supplied. The resulting data point to the advantages of combined glucose and non-glucose carbohydrate application for parenteral nutrition in medically induced and postoperative hypercorticalic states of metabolism.

Adolescent↗
PubMed1983

Sorbitol intolerance: an unappreciated cause of functional gastrointestinal complaints.

Sorbitol, a polyalcohol sugar, is the sweetener in most "sugar-free" products and may produce an osmotic diarrhea if ingested in large amounts (20-50 g). Whether or not smaller amounts of ingested sorbitol may be associated with other symptoms characteristic of carbohydrate malabsorption has not been determined. Using breath hydrogen analysis, the absorption of 5, 10, and 20 g of sorbitol was studied in 7 healthy volunteers. In a majority of subjects, ingestion of as little as 5 g sorbitol was associated with a significant increase in breath hydrogen concentration. Most subjects experienced mild gastrointestinal distress (gas, bloating) after 10 g and severe symptoms (cramps, diarrhea) after 20 g. These data suggest that the evaluation of patients with "functional" gastrointestinal complaints should include careful inquiry into the use of products containing sorbitol.

Adult↗
PubMed1994

[Carbohydrate substitutes: comparative study of intestinal absorption of fructose, sorbitol and xylitol].

BACKGROUND: The carbohydrate substitutes fructose, sorbitol and xylitol are gaining more and more importance in the production of dietary food. But they can provoke gastrointestinal side-effects. In a randomized double blind study the rate of malabsorption of these sugars was compared and the concomitant symptoms were recorded. SUBJECTS AND METHODS: 25 healthy controls received 25 g of each sugar within 3 consecutive days. The intestinal absorption was determined by H2-exhalation tests and the clinical symptoms were recorded. RESULTS: The rate of malabsorption was 84% for sorbitol, 36% for fructose and 12% for xylitol (p < 0.01 for sorbitol versus fructose and xylitol). 57% of the participants with pathological H2-test after sorbitol and 56% after fructose reported symptoms, while all of the 3 malabsorbers of xylitol were symptomatic. CONCLUSIONS: There is an advantage to administering xylitol and fructose with regard to the intestinal absorption and concomitant symptoms as compared with sorbitol. H2-exhalation tests appear to be a reliable diagnostic tool to detect carbohydrate malabsorption and should find broader application in patients suffering from non-specific abdominal complaints.

Adult↗
PubMed1976

[Metabolism of sorbitol and xylitol in newborn and premature infants and the effect on blood sugar and lactates].

The glucose blood level shows a clear increase in neonates and premature infants with continuous intravenous infusion of sorbitol and xylitol at graded intake rates ranging from 0.5 g - kg(-1) - h(-1) to 1.0 g - kg(-1) - h(-1) when they are administered over a period of 2 to 3 hours. With an intake of 0.5 g - kg(-1) - h(-1) for both polyols a steady state is established after 60 and 90 minutes, respectively. With intake rates of 0.75 g - kg(-1) - h(-1) the xylitol blood level shows a continous increase until the end of infusion, whereas after a 3-hour infusion of sorbitol a steady state is finally established, but with clearly elevated blood levels. The values of the total clearnace of the polyols show a decrease with increasing intake rates and thus indicate a more difficult turnover. Therefore, a, a maximal intake rate of 0.25 g - kg(-1) h-1 should not be surpassed for long-term intravenous nutrition of neonates. The lactate concentration shows a distinct increase with an intake of 1.0 g - kg(-1) - h(-1) sorbitol. A significant increase of blood glucose is also observed after rapid infusion of 0.5 g - kg(-1) and 1.0 g - kg(-1) xylitol, whereas similar doses of sorbitol lead to a considerable delay of the increase of glucose. After rapid infusion of 1.0 g - kg(-1), both polyols lead to a significant increase of the blood lactate concentration. Therefore and because of the delayed increase in blood glucose after sorbitol, the rapid infusion of the polyols must be avoided. From our findings of the metabolic rates of the polyols it can be suggested that the polyols in part can be used instead of glucose in parenteral nutrition also in the neonatal period. Further studies are necessary to prove if the polyols have clear-cut advantages over glucose in neonates.

Blood Glucose↗
PubMed1995

Stimulating effects of sorbitol and L-xylose on rat ileal Ca transport in vitro.

The direct effect of sorbitol and L-xylose on net intestinal calcium transport was compared to that of lactose, by determining unidirectional steady state calcium fluxes in segments of rat ileum in vitro under short-circuited conditions. The iso-molar addition of either 100 mM sorbitol, L-xylose, or lactose in mucosal buffer fluid increased the absorptive flux of Ca from mucosa to serosa to a similar extent and thus reversed ileal net Ca transport from net secretion to a zero net movement. The three substances decreased tissue conductance and reversed tissue polarity. At 200 mM, sorbitol induced a stimulation of net Ca transport due to an enhancement of absorptive Ca flux but in addition due to a decrease of secretory Ca flux from serosa to mucosa. The presence of 1 mM N-ethylmaleimide abolished the effects of sorbitol on ileal Ca flux. In conclusion, the present result shows that sorbitol, L-xylose, and lactose increase net Ca absorption to a comparable extent, in the absence of electrochemical or osmotic gradients. Such an absence of specificity suggests a stimulation of transcellular Ca transport related to the decrease of Na concentration in mucosal solution.

Animals↗
PubMedDate not supplied

Localization of aldose reductase and sorbitol dehydrogenase in the nervous system of normal and diabetic rats.

Intraneuronal accumulations of sorbitol and fructose have been postulated to predispose the nervous system to the cerebral edema associated with the treatment of diabetic ketoacidosis. In the present study, the enzymes of the pathway for the production of sorbitol and fructose, aldose reductase and sorbitol dehydrogenase, were localized histochemically in brain, spinal cord and sciatic nerve. Enzyme activity was limited to the choroidal epithelium, ependymal cells, and pia mater in normal, 2- and 10-week streptozotocin diabetic and vehicle-treated rats. Sorbitol dehydrogenase activity was located in blood vessels and perineurium of the sciatic nerve in these groups of rats. Comparison of diabetic and vehicle groups did not demonstrate any alteration in the activity of either enzyme in the central nervous system. However, there was a decrease in sorbitol dehydrogenase activity in the blood vessels in the sciatic nerve in 50% of the 10-week diabetic rats.

Aldehyde Reductase↗
PubMed1994

Effect of ageing on erythrocyte aldose reductase and sorbitol dehydrogenase activity.

We measured erythrocyte aldose reductase and sorbitol dehydrogenase activity in erythrocytes in healthy individuals aged from 16 to 91 years to determine the mechanism of age-dependent sorbitol accumulation. Erythrocyte aldose reductase activity increased significantly with age but ageing had no effect on sorbitol dehydrogenase activity. Age and the aldose reductase/sorbitol dehydrogenase ratio were positively correlated. These findings suggest that an increase in the ratio of aldose reductase to sorbitol dehydrogenase may contribute to the tissue accumulation of sorbitol in the elderly and may be a mechanism of a disease that is common in elderly individuals.

Adolescent↗
PubMed1985

Erythrocyte sorbitol dehydrogenase of selected non-mammalian vertebrates.

Erythrocyte sorbitol dehydrogenase activity (EC 1.1.1.14) from selected non-mammalian vertebrates was studied showing great variability not related to their phylogenetical position. The Michaelis-Menten constant (Km) for sorbitol exhibited moderate low values in the studied animals. In snakes the Km for sorbitol was low with moderate activity of sorbitol dehydrogenase, suggesting that the enzyme could reach maximum activity with lower sorbitol concentration in comparison to other vertebrates. In the snakes the enzyme showed the same affinity for all the studied polyols, indicating that we are probably dealing with a very ancient enzyme, an unspecific enzyme.

Animals↗
PubMed1999

Effect of high temperature on the metabolic processes affecting sorbitol synthesis in the silverleaf whitefly, Bemisia argentifolii.

Whiteflies accumulate the polyhydric alcohol, sorbitol, when exposed to temperatures greater than about 30 degrees C. Feeding experiments using artificial diets containing labeled sucrose showed that more of the label was incorporated into whitefly bodies and less was excreted in the honeydew when feeding was conducted at 41 compared with 25 degrees C. Analysis of the components of the honeydew showed that more of the excreted label was in glucose and fructose and less in trehalulose at 41 degrees C than at 25 degrees C. A similar effect of temperature on honeydew composition occurred for whiteflies feeding on cotton leaves. Measurement of the activities of glycolytic, pentose-phosphate and polyol pathway enzymes at 30 and 42 degrees C showed that NADPH-dependent ketose reductase/sorbitol dehydrogenase (NADPH-KR/SDH), sucrase, glucokinase and glucose-6-phosphate dehydrogenase activities were stimulated to a greater extent at 42 degrees C than trehalulose synthase and fructokinase. NAD(+)-sorbitol dehydrogenase (NAD(+)-SDH) activity was inhibited at 42 degrees C. We propose that high temperature alters metabolic activity in a way that increases the availability of fructose and stimulates pentose-phosphate pathway activity, providing both the substrate and coenzyme for sorbitol synthesis. High temperature also increases the activity of NADPH-KR/SDH, the enzyme in whiteflies that synthesizes sorbitol, but inhibits the activity of NAD(+)-SDH, the enzyme that degrades sorbitol.

Journal Article↗
PubMed2003

Membrane-bound D-sorbitol dehydrogenase of Gluconobacter suboxydans IFO 3255--enzymatic and genetic characterization.

Gluconobacter strains effectively produce L-sorbose from D-sorbitol because of strong activity of the D-sorbitol dehydrogenase (SLDH). L-sorbose is one of the important intermediates in the industrial vitamin C production process. Two kinds of membrane-bound SLDHs, which consist of three subunits, were reportedly found in Gluconobacter strains [Agric. Biol. Chem. 46 (1982) 135,FEMS Microbiol. Lett. 125 (1995) 45]. We purified a one-subunit-type SLDH (80 kDa) from the membrane fraction of Gluconobacter suboxydans IFO 3255 solubilized with Triton X-100 in the presence of D-sorbitol, but the cofactor could not be identified from the purified enzyme. The SLDH was active on mannitol, glycerol and other sugar alcohols as well as on D-sorbitol to produce respective keto-aldoses. Then, the SLDH gene (sldA) was cloned and sequenced. It encodes the polypeptide of 740 residues, which contains a signal sequence of 24 residues. SLDH had 35-37% identity to those of membrane-bound quinoprotein glucose dehydrogenases (GDHs) from Escherichia coli, Gluconobacter oxydans and Acinetobacter calcoaceticus except the N-terminal hydrophobic region of GDH. Additionally, the sldB gene located just upstream of sldA was found to encode the polypeptide consisting of 126 very hydrophobic residues that is similar to the one-sixth N-terminal region of the GDH. Development of the SLDH activity in E. coli required co-expression of the sldA and sldB genes and the presence of PQQ. The sldA gene disruptant showed undetectable oxidation activities on D-sorbitol in growing culture, and resting-cell reaction (pH 4.5 and 7); in addition, they showed undetectable activities on D-mannitol and glycerol. The disruption of the sldB gene by a gene cassette with a downward promoter to express the sldA gene resulted in formation of a larger size of the SLDH protein and in undetectable oxidation of the polyols. In conclusion, the SLDH of the strain 3255 functions as the main polyol dehydrogenase in vivo. The sldB polypeptide possibly has a chaperone-like function to process the SLDH polypeptide into a mature and active form.

Amino Acid Sequence↗
PubMed1988

Purification and characterization of human liver sorbitol dehydrogenase.

Sorbitol dehydrogenase from human liver was purified to homogeneity by affinity chromatography on immobilized triazine dyes, conventional cation-exchange chromatography, and high-performance liquid chromatography. The major form is a tetrameric, NAD-specific enzyme containing one zinc atom per subunit. Human liver sorbitol dehydrogenase oxidizes neither ethanol nor other primary alcohols. It catalyzes the oxidation of a secondary alcohol group of polyol substrates such as sorbitol, xylitol, or L-threitol. However, the substrate specificity of human liver sorbitol dehydrogenase is broader than that of the liver enzymes of other sources. The present report describes the stereospecific oxidation of (2R,3R)-2,3-butanediol, indicating a more general function of sorbitol dehydrogenase in the metabolism of secondary alcohols. Thus, the enzyme complements the substrate specificities covered by the three classes of human liver alcohol dehydrogenase.

Amino Acids↗
PubMed1993

Sorbitol as the Primary Carbon Source for the Growth of Embryogenic Callus of Maize.

The effects of various carbon sources on initiation and maintenance of embryogenic callus of maize (Zea mays L.) and on the regeneration of plants from embryogenic callus were studied. Growth of embryogenic callus tissue on media containing sucrose was typified by the subsequent growth of both embryogenic (regenerable) and nonembryogenic (nonregenerable) callus. Growth of embryogenic callus on sorbitol was unique among the carbon sources tested in that sorbitol supported the subsequent growth of only embryogenic callus. Further experiments demonstrated that embryogenic callus grown on sorbitol had a greater regenerative capacity (more plants produced per gram fresh weight of callus) than callus grown on sucrose. Sorbitol dehydrogenase was detected in embryogenic callus of maize at a specific activity roughly equivalent to that found in zygotic embryos of developing seeds. Nonembryogenic callus did not contain significant levels of sorbitol dehydrogenase activity.

Journal Article↗
PubMed1989

Variability within mammalian sorbitol dehydrogenases. The primary structure of the human liver enzyme.

The primary structure of sorbitol dehydrogenase from human liver has been determined by peptide analysis in order to relate the variability of this enzyme to that of the others within the alcohol dehydrogenase family. The structure obtained reveals 355 residues with an acyl-blocked N-terminus and an unexpected microheterogeneity at position 237 (Gln/Leu). The residue identity between sheep and human liver sorbitol dehydrogenase is 89%. This variability is similar to that of class I alcohol dehydrogenases, but distinctly different from that of class III alcohol dehydrogenases, the structures of which are much more conserved. Consequently, class III alcohol dehydrogenase is thus far unique within this family of dehydrogenases, suggesting a particularly strict requirement for that structure. The variability within sorbitol dehydrogenase involves all segments of the molecule but is largely at surface positions and clusters in one such region, covering positions 214-240, corresponding to a segment of the coenzyme-binding domain. Ligands to the active-site zinc and most residues lining the coenzyme-binding and substrate-binding pockets are conserved. However, provided conformational models are reliable, a charge difference may affect the interactions at the inner part of the substrate pocket, another charge difference may affect the interdomain region, and a size difference the adenine pocket. The primary structure of human liver sorbitol dehydrogenase further shows that the absence of three of the four ligands to a second zinc atom present in alcohol dehydrogenases is a general property of sorbitol dehydrogenase.

Amino Acid Sequence↗