Glycogen synthase and phosphorylase activity in pancreatic islets

info:eu-repo/semantics/publishe

Hexose Metabolism in Pancreatic Islets: Glycogen Synthase and Glycogen Phosphorylase Activities

The activity of glycogen synthase and glycogen phosphorylase was measured in rat pancreatic islet homogenates. For this purpose, the sensitivity of current radioisotopic procedures for the assay of these enzymes in liver extracts was increased by about two orders of magnitude. Even so, the measurement of glycogen synthase and phosphorylase in islet homogenates was hampered by a potent amylase-like activity, resulting in the hydrolysis of preformed or newly formed 14C-labeled glycogen. Acarbose suppressed the latter phenomenon which was found attributable to both minute contamination of isolated islets by acinar cells and genuine α-amylase activity in purified islet β-cells. As measured by the more sensitive method in the presence of acarbose, the a/(a + b) ratio for glycogen synthase activity in islet homogenates was increased in islets preincubated in the presence as distinct from absence of D-glucose and decreased after preincubation with forskolin. These changes represented a mirror image of those evoked by D-glucose and forskolin in the a/(a + b) ratio for glycogen phosphorylase activity. It is concluded that glycogen synthesis and breakdown are regulated in the endocrine pancreas in a manner qualitatively comparable to that prevailing in hepatocytes, the possible participation of an amylase-like activity to glycogen metabolism in intact islet β-cells requiring further investigation. © 1994 Academic Press. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Interference of glycogenolysis with glycolysis in pancreatic islets from glucose-infused rats

info:eu-repo/semantics/publishe

Is glycolysis impaired in erythrocytes of diabetic rats?

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Interference of glycogenolysis with glycolysis in pancreatic islets from glucose-infused rats

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Interconversion of D-fructose 1,6-bisphosphate and triose phosphates in human erythrocytes

Aldolase and triose phosphate isomerase both display strict specificity towards the enantiomers of [1-3H]glycerone 3-phosphate. The enantiomer generated from D-[1-3H]glyceraldehyde 3-phosphate produces 3HOH in the aldolase reaction, whilst the other enantiomer generated from D-[3-3H]fructose 1,6-bisphosphate is solely detritiated in the reaction catalyzed by triose phosphate isomerase. Advantage was taken of such a specificity to assess,in human erythrocytes exposed to either D-[3-3H]glucose or D-[3,4-3H]glucose, the extent of D-glyceraldehyde 3-phosphate sequential conversion to glycerone 3-phosphate and D-fructose 1,6-bisphosphate, relative to net glycolytic flux. At 37°C and in the presence of 5.6 mM D-glucose, only 55% of the metabolites of D-[4-3H]glucose underwent detritiation in the reactions catalyzed by triose phosphate isomerase and aldolase. Such a percentage was further decreased at low temperature (8°C) or lower concentrations of D-glucose (0.2 and 1.0 mM). However, when the erythrocytes were exposed to menadione, the increase in 3HOH production from either D-[3-3H]glucose or D-[3,4-3H]glucose indicated that the majority of the 3H atoms initially located on the C4 of D-glucose were recovered as 3HOH upon circulation through the pentose phosphate pathway. These findings suggest that, under physiological conditions, a large fraction of D-glyceraldehyde 3-phosphate generated from exogenous D-glucose may undergo enzyme-to-enzyme channelling in the glycolytic pathway.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Erratum: Novel inhibitors of the sodium-calcium exchanger: Benzene ring analogues of N-guanidino substituted amiloride derivatives (European Journal of Medicinal Chemistry (2001) 36:7-8 (597-614) PII:S0223523401012478)

SCOPUS: er.jinfo:eu-repo/semantics/publishe

3- and 4-substituted 4H-pyrido[4,3-e]-1,2,4-thiadiazme 1,1-dioxides as potassium channel openers: Synthesis, pharmacological evaluation, and structure-activity relationships

SCOPUS: re.jinfo:eu-repo/semantics/publishe

Covid-19 and blood groups: ABO antibody levels may also matter

International audienceBackground : Susceptibility to Covid-19 has been found to be associated with ABO blood group, with O type individuals being at a lower risk. However, the underlying mechanism has not been elucidated. Here, we aimed to test the hypothesis that Covid-19 patients might have lower levels of ABO antibodies than non-infected individuals as they could offer some degree of protection.Methods : After showing that the viral spike protein harbors the ABO glycan epitopes when produced by cells expressing the relevant glycosyltransferases, like upper respiratory tract epithelial cells, we enrolled 290 patients with Covid-19 and 276 asymptomatic controls to compare their levels of natural ABO blood group antibodies.Results : We found significantly lower IgM anti-A + anti-B agglutination scores in blood group O patients (76.93 vs 88.29, P-value=0.034) and lower levels of anti-B (24.93 vs 30.40, P-value=0.028) and anti-A antibodies (28.56 vs 36.50, P-value= 0.048) in blood group A and blood group B patients, respectively, compared to controls.Conclusion : In this study, we showed that ABO antibodies levels are significantly lower in Covid-19 patients compared to controls. These findings could indicate that patients with low levels of ABO antibodies are at higher risk of being infected