scholarly journals Diabetic Embryopathy Susceptibility in Mice Is Associated with Differential Dependence on Glucosamine and Modulation of High Glucose-Induced Oxidative Stress

Antioxidants ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1156
Author(s):  
Jin Hyuk Jung ◽  
Mary R. Loeken
Keyword(s):  
Oxidative Stress ◽  
High Glucose ◽  
Glucose Transporter ◽  
Embryonic Stem ◽  
Amino Sugar ◽  
Pentose Phosphate ◽  
Mouse Strains ◽  
Hexosamine Biosynthetic Pathway ◽  
Diabetic Embryopathy ◽  
Stimulation Of

The high KM glucose transporter, GLUT2 (SLC2A2), is expressed by embryos and causes high rates of glucose transport during maternal hyperglycemic episodes in diabetic pregnancies and causes congenital malformations (diabetic embryopathy). GLUT2 is also a low KM transporter of the amino sugar, glucosamine (GlcN), which enters the hexosamine biosynthetic pathway (HBP) and provides substrate for glycosylation reactions. Exogenous GlcN also increases activity of the pentose phosphate pathway (PPP), which increases production of NADPH reducing equivalents. GLUT2-transported GlcN is inhibited by high glucose concentrations. Not all mouse strains are susceptible to diabetic embryopathy. The aim of this study was to test the hypothesis that susceptibility to diabetic embryopathy is related to differential dependence on exogenous GlcN for glycosylation or stimulation of the PPP. We tested this using murine embryonic stem cell (ESC) lines that were derived from embryopathy-susceptible FVB/NJ (FVB), and embryopathy-resistant C57Bl/6J (B6), embryos in the presence of low or high glucose, and in the presence or absence of GlcN. There were no significant differences in Glut2 expression, or of glucose or GlcN transport, between FVB and B6 ESC. GlcN effects on growth and incorporation into glycoproteins indicated that FVB ESC are more dependent on exogenous GlcN than are B6 ESC. GlcN stimulated PPP activity in FVB but not in B6 ESC. High glucose induced oxidative stress in FVB ESC but not in B6 ESC. These results indicate that FVB embryos are more dependent on exogenous GlcN for glycosylation, but also for stimulation of the PPP and NADPH production, than are B6 embryos, thereby rendering FVB embryos more susceptible to high glucose to induce oxidative stress.

Hyperglycemia-mediated activation of the hexosamine biosynthetic pathway results in myocardial apoptosis

2010 ◽  
Vol 299 (1) ◽  
pp. C139-C147 ◽  
Author(s):  
Uthra Rajamani ◽  
M. Faadiel Essop
Keyword(s):  
Oxidative Stress ◽  
High Glucose ◽  
Biosynthetic Pathway ◽  
Heart Diseases ◽  
Antioxidant Treatment ◽  
Hexosamine Biosynthetic Pathway ◽  
Myocardial Apoptosis ◽  
Activity Measurements ◽  
H9c2 Cardiomyoblasts

The mechanisms mediating hyperglycemia-mediated myocardial cell death are poorly defined. Since elevated flux through the hexosamine biosynthetic pathway (HBP) is closely linked with the diabetic phenotype, we hypothesized that hyperglycemia-mediated oxidative stress results in greater O-GlcNAcylation (HBP end product) of the proapoptotic peptide BAD, thereby increasing myocardial apoptosis. H9c2 cardiomyoblasts were exposed to high glucose (33 mM) ± HBP modulators ± antioxidant treatment for 5 days vs. matched controls (5.5 mM), and we subsequently evaluated apoptosis by immunoblotting, immunofluorescence staining, and caspase activity measurements. In vitro reactive oxygen species (ROS) levels were quantified by 2′,7′-dichlorodihydrofluorescein diacetate staining (fluorescence microscopy and flow cytometry). We determined total and BAD O-GlcNAcylation, respectively, by immunoblotting and immunofluorescence microscopy. The current study shows that high glucose treatment of cells significantly increased the degree of apoptosis. In parallel, overall O-GlcNAcylation, BAD O-GlcNAcylation, and ROS levels were increased. HBP inhibition and antioxidant treatment attenuated these effects, while increased end product levels exacerbated it. As BAD-Bcl-2 dimer formation enhances apoptosis, we performed immunoprecipitation analysis and colocalization and found increased dimerization in cells exposed to hyperglycemia. Our study identified a novel pathway whereby hyperglycemia results in greater oxidative stress and increased HBP activation and BAD O-GlcNAcylation in H9c2 cardiomyoblasts. Since greater BAD-Bcl-2 dimerization increases myocardial apoptosis, this pathway may play a crucial role in diabetes-related onset of heart diseases.

scholarly journals Failure to increase glucose consumption through the pentose-phosphate pathway results in the death of glucose-6-phosphate dehydrogenase gene-deleted mouse embryonic stem cells subjected to oxidative stress

2003 ◽  
Vol 370 (3) ◽  
pp. 935-943 ◽  
Author(s):  
Stefania FILOSA ◽  
Annalisa FICO ◽  
Francesca PAGLIALUNGA ◽  
Marco BALESTRIERI ◽  
Almudena CROOKE ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Pentose Phosphate Pathway ◽  
Es Cells ◽  
Large Fraction ◽  
Embryonic Stem ◽  
Reducing Power ◽  
High Ratio ◽  
Pentose Phosphate ◽  
Wild Type

Mouse embryonic stem (ES) glucose-6-phosphate (G6P) dehydrogenase-deleted cells (G6pdΔ), obtained by transient Cre recombinase expression in a G6pd-loxed cell line, are unable to produce G6P dehydrogenase (G6PD) protein (EC 1.1.1.42). These G6pdΔ cells proliferate in vitro without special requirements but are extremely sensitive to oxidative stress. Under normal growth conditions, ES G6pdΔ cells show a high ratio of NADPH to NADP+ and a normal intracellular level of GSH. In the presence of the thiol scavenger oxidant, azodicarboxylic acid bis[dimethylamide], at concentrations lethal for G6pdΔ but not for wild-type ES cells, NADPH and GSH in G6pdΔ cells dramatically shift to their oxidized forms. In contrast, wild-type ES cells are able to increase rapidly and intensely the activity of the pentose-phosphate pathway in response to the oxidant. This process, mediated by the [NADPH]/[NADP+] ratio, does not occur in G6pdΔ cells. G6PD has been generally considered essential for providing NADPH-reducing power. We now find that other reactions provide the cell with a large fraction of NADPH under non-stress conditions, whereas G6PD is the only NADPH-producing enzyme activated in response to oxidative stress, which can act as a guardian of the cell redox potential. Moreover, bacterial G6PD can substitute for the human enzyme, strongly suggesting that a relatively simple mechanism of enzyme kinetics underlies this phenomenon.

scholarly journals Regulation of Erythritol Metabolism, a Biomarker of Cardiometabolic Disease

2021 ◽  
Vol 5 (Supplement_2) ◽  
pp. 515-515
Author(s):  
Semira Ortiz ◽  
Martha Field
Keyword(s):  
Oxidative Stress ◽  
Hydrogen Peroxide ◽  
High Glucose ◽  
Elevated Serum ◽  
A549 Cells ◽  
Predictive Biomarker ◽  
Pentose Phosphate ◽  
Tissue Type ◽  
Disease Development ◽  
Central Adiposity

Abstract Objectives Serum erythritol is a predictive biomarker of chronic disease development and complications.  In cohort studies, elevated serum erythritol at baseline was predictive of central adiposity gain, T2DM, and cardiovascular disease development up to 20 years later. Erythritol is a polyol that has been well characterized as a non-nutritive sweetener. Erythritol was recently discovered to be synthesized endogenously in humans from glucose through the pentose phosphate pathway (PPP). The regulation of erythritol synthesis in mammals, however, is not characterized. The purpose of this study was to assess stimuli that modulate intracellular erythritol levels and the distribution of erythritol in key metabolic tissues. Methods First, we fed 8-week-old C57BL/6J mice a defined diet (AIN93G) for two weeks, after which plasma and tissue erythritol were measured by GC-MS. To further evaluate the cellular regulation of erythritol synthesis, we used A549 cells for their high PPP activity. Using siRNA, we knocked down SORD (a potential erythritol-synthesizing enzyme) and glucose-6-phosphate dehydrogenase (G6PD) under normal (5 mM) and high (25 mM) glucose conditions and measured intracellular erythritol. We also exposed A549’s to hydrogen peroxide to assess if erythritol synthesis is elevated by oxidative stress, an additional stimulator of the PPP. Results Plasma erythritol ranged from 0.44 uM to 0.73 uM in young, healthy mice. Erythritol differed significantly based on tissue type (p < 0.0001). The liver and kidney had the highest relative erythritol, followed by quadriceps, whereas white adipose tissue contained the least erythritol. SORD knockdown significantly reduced erythritol synthesis under high glucose, but not normal glucose conditions (p < 0.01). Knockdown of G6PD did not impact erythritol synthesis at either glucose concentration. Finally, treatment with hydrogen peroxide significantly increased intracellular erythritol (p < 0.0001). Conclusions In conclusion, erythritol is present in mouse plasma, SORD-expressing tissues, and human cells. Erythritol was elevated by high glucose and oxidative stress–two key factors in the pathogenesis of cardiometabolic diseases. Together, these data suggest that erythritol synthesis occurs parallel to elevated PPP flux in response to metabolic stressors. Funding Sources N/A

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