Decreased GLUT1/NHE1 RNA expression in whole blood predicts disease severity in patients with COVID-19

AIMS

We aimed to assess whether expression of whole-blood RNA of sodium proton exchanger 1 (NHE1) and glucose transporter 1 (GLUT1) is associated with COVID-19 infection and outcome in patients presenting to the emergency department with respiratory infections. Furthermore, we investigated NHE1 and GLUT1 expression in the myocardium of deceased COVID-19 patients.

METHODS AND RESULTS

Whole-blood quantitative assessment of NHE1 and GLUT1 RNA was performed using quantitative PCR in patients with respiratory infection upon first contact in the emergency department and subsequently stratified by SARS-CoV-2 infection status. Assessment of NHE1 and GLUT1 RNA using PCR was also performed in left ventricular myocardium of deceased COVID-19 patients. NHE1 expression is up-regulated in whole blood of patients with COVID-19 compared with other respiratory infections at first medical contact in the emergency department (control: 0.0021 ± 0.0002, COVID-19: 0.0031 ± 0.0003, P = 0.01). The ratio of GLUT1 to NHE1 is significantly decreased in the blood of COVID-19 patients who are subsequently intubated and/or die (severe disease) compared with patients with moderate disease (moderate disease: 0.497 ± 0.083 vs. severe disease: 0.294 ± 0.0336, P = 0.036). This ratio is even further decreased in the myocardium of patients who deceased from COVID-19 in comparison with the myocardium of non-infected donors.

CONCLUSIONS

NHE1 and GLUT1 may be critically involved in the disease progression of SARS-CoV-2 infection. We show here that SARS-CoV-2 infection critically disturbs ion channel expression in the heart. A decreased ratio of GLUT1/NHE1 could potentially serve as a biomarker for disease severity in patients with COVID-19.

Relationship between plasma glycation with membrane modification, oxidative stress and expression of glucose trasporter-1 in type 2 diabetes patients with vascular complications

BACKGROUND OF STUDY

Enhanced protein glycation in diabetes causes irreversible cellular damage through membrane modifications. Erythrocytes are persistently exposed to plasma glycated proteins; however, little are known about its consequences on membrane. Aim of this study was to examine the relationship between plasma protein glycation with erythrocyte membrane modifications in type 2 diabetes patients with and without vascular complications.

METHOD

We recruited 60 healthy controls, 85 type 2 diabetic mellitus (DM) and 75 type 2 diabetic patients with complications (DMC). Levels of plasma glycation adduct with antioxidants (fructosamine, protein carbonyl, β-amyloids, thiol groups, total antioxidant status), erythrocyte membrane modifications (protein carbonyls, β-amyloids, free amino groups, erythrocyte fragility), antioxidant profile (GSH, catalase, lipid peroxidation) and Glut-1 expression were quantified.

RESULT

Compared with controls, DM and DMC patients had significantly higher level of glycation adducts, erythrocyte fragility, lipid peroxidation and Glut-1 expression whereas declined levels of plasma and cellular antioxidants. Correlation studies revealed positive association of membrane modifications with erythrocyte sedimentation rate, fragility, peroxidation whereas negative association with free amino groups, glutathione and catalase.

CONCLUSION

Our data suggest that plasma glycation is associated with oxidative stress, Glut-1 expression and erythrocyte fragility in DM patients. This may further contribute to progression of vascular complications.

Impact of diabetes in blood-testis and blood-brain barriers: resemblances and differences

Blood-tissue barriers prevent an uncontrolled exchange of large molecules between adjacent but metabolically separated compartments. There are several known barriers and two of the most important and tightest blood-tissue barriers are the blood-testis barrier (BTB) and the blood-brain barrier (BBB). Under normal conditions these barriers, formed by tight junctions between adjacent cells, control the entry of substances and metabolites. However, hyperglycemia and other diabetes-related complications, such as hypertension, impair the function of these biological barriers with dramatic consequences. Although both, BBB and BTB, are responsible for the maintenance of different biological processes, they have some remarkable similarities not always explored when looking at metabolic-related diseases such as diabetes. These barriers possess their own glucose sensing machinery, suffer a tied hormonal control and have specific mechanisms to counteract hyper- and hypoglycemia. In BBB and BTB the insulin signaling is also distinct from other tissues and organs thus evidencing their importance in protecting against or exacerbating the effects of diabetes on glucose metabolism. The control of glucose and lactate levels in brain and testis highlights the role of these barriers in protecting against peripheral glucose and lactate fluctuations that occur in the diabetic individual. We review the role of BBB and BTB in the control of glucose and metabolic dysfunction caused by diabetes in the brain and seminiferous epithelium. Gaining a better understanding of the molecular mechanisms through which glucose metabolism disrupts BBB and BTB function may highlight new opportunities for the treatment of diabetic complications in brain and male reproductive function.

A new class of drug for the management of type 2 diabetes: sodium glucose co-transporter inhibitors: 'glucuretics'

BACKGROUND

Type 2 diabetes is a common, chronic disease with a prevalence that is increasing at epidemic proportions. Management involves advice on lifestyle changes, oral anti-hyperglycaemic agents and/or insulin. The kidneys play a major role in the regulation of glucose, re-absorbing 99% of the plasma glucose filtered through the renal glomeruli tubules. The glucose transporter, SGLT2, which is found primarily in the S1 segment of the proximal renal tubule accounts for 90% of glucose re-absorption. Competitive inhibition of SGLT2 induces glucosuria in a dose dependent manner and appears to have beneficial effects on glucose regulation in individuals with type 2 diabetes. O-glucoside phlorozin is the model substance for SGLT2 inhibitors: various O-, C-, N- and S-glucosides with varying affinity and specificity have been synthesised.

AIMS

The aim of this review is to describe the background, the mechanism of action and the possible role for sodium glucose co-transporter inhibitors in the treatment of diabetes.

MATERIALS AND METHODS

Databases, including MEDLINE, COCHRANE, EMBASE and EBM reviews were searched for literature relating to sodium glucose transport inhibitors and improvements in glycaemic control in patients with diabetes.

RESULTS

The data suggest that sodium glucose transport inhibitors significantly improve glycaemic control by increasing glucosuria. Some studies described significant reductions in weight and improvement in blood pressure. The most common side effect was infection involving the urinary and genital tracts.

CONCLUSIONS

Sodium glucose co-transport inhibitors appear to be an effective line of treatment, well tolerated and could be a further drug class in the armamentarium available for the management of type 2 diabetes.

Biological role, clinical significance, and therapeutic possibilities of the recently discovered metabolic hormone fibroblastic growth factor 21

Fibroblast growth factor 21 (FGF21), a 181 amino acid circulating protein, is a member of the FGF superfamily, with relevant metabolic actions. It acts through the interaction with specific FGF receptors and a cofactor called β-Klotho, whose expression is predominantly detected in metabolically active organs. FGF21 stimulates glucose uptake in adipocytes via the induction of glucose transporter-1. This action is additive and independent of insulin. β-Cell function and survival are preserved, and glucagon secretion is reduced by this protein, thus decreasing hepatic glucose production and improving insulin sensitivity. Lipid profile has been shown to be improved by FGF21 in several animal models. FGF21 increases energy expenditure in rodents and induces weight loss in diabetic nonhuman primates. It also exerts favorable effects on hepatic steatosis and reduces tissue lipid content in rodents. Adaptive metabolic responses to fasting, including stimulation of ketogenesis and fatty acid oxidation, seem to be partially mediated by FGF21. In humans, serum FGF21 concentrations have been found elevated in insulin-resistant states, such as impaired glucose tolerance and type 2 diabetes. FGF21 levels are correlated with hepatic insulin resistance index, fasting blood glucose, HbA1c, and blood glucose after an oral glucose tolerance test. A relationship between FGF21 levels and long-term diabetic complications, such as nephropathy and carotid atheromatosis, has been reported. FGF21 levels decreased in diabetic patients after starting therapy with insulin or oral agents. Increased FGF21 serum levels have also been found to be associated with obesity. In children, it is correlated with BMI and leptin levels, whereas in adults, FGF21 levels are mainly related to several components of the metabolic syndrome. Serum FGF21 levels have been found to be elevated in patients with ischemic heart disease. In patients with renal disease, FGF21 levels exhibited a progressive increase as renal function deteriorates. Circulating FGF21 levels seem to be related to insulin resistance and inflammation in dialysis patients. In summary, FGF21 is a recently identified hormone with antihyperglycemic, antihyperlipidemic, and thermogenic properties. Direct or indirect potentiation of its effects might be a potential therapeutic target in insulin-resistant states.

Clinicopathological presentation of varying 18F-FDG uptake and expression of glucose transporter 1 and hexokinase II in cases of hepatocellular carcinoma and cholangiocellular carcinoma

We report the results of (18)F-fluorodeoxyglucose positron emission tomography (FDG PET) and immunohistochemical staining of glucose transporter 1 (Glut-1) and hexokinase II (HK-II) in patients with hepatocellular carcinoma (HCC) and cholangiocellular carcinoma (CCC) to observe the variation in (18)F-FDG uptake and variation in expression of Glut-1 and HK-II in these hepatic tumors. In the case of HCC, moderate (18)F-FDG uptake and strong expression of HK-II were detected, whereas Glut-1 was not expressed. Conversely, CCC showed high (18)F-FDG uptake and increased expression of Glut-1 but HK-II was not expressed. The variation in the (18)F-FDG uptake and expression of Glut 1 and HK-II in HCC and CCC might be owing to the difference in origin and the different mechanisms involved in glucose uptake, rate of glucose transporters, and hexokinase activity involved in the glycolytic pathway.

Ultrastructure of Human Erythrocyte GLUT1†

This study was undertaken to examine GLUT1 quaternary structure. Independent but complementary methodologies were used to investigate the influence of membrane-solubilizing detergents on GLUT1/lipid/detergent micelle hydrodynamic radii. Hydrodynamic size analysis and electron microscopy of GLUT1/lipid/detergent micelles and freeze-fracture electron microscopy of GLUT1 proteoliposomes support the hypothesis that the glucose transporter is a multimeric (probably tetrameric) complex of GLUT1 proteins. GLUT1 forms a multimeric complex in octyl glucoside that dissociates upon addition of reductant. Some detergents (e.g., CHAPS and dodecyl maltoside) promote the dissociation of GLUT1 oligomers into smaller aggregation states (dimers or monomers). These complexes do not reassemble as larger oligomers when dissociating detergents are subsequently replaced with nondissociating detergents such as octyl glucoside or cholic acid. When dissociating detergents are replaced with lipids, the resulting proteoliposomes catalyze protein-mediated sugar transport, and the subsequent addition of solubilizing, nondissociating detergents generates higher (tetrameric) GLUT1 aggregation states. These findings suggest that some detergents stabilize while others destabilize GLUT1 quaternary structure. GLUT1 does not appear to exchange rapidly between protein/lipid/detergent micelles but is able to self-associate in the plane of the lipid bilayer.

Enhanced Expression of Glucose Transporter 1 on Erythrocyte Membrane in Hemodialysis Patients: The Possible Role in Erythrocyte Ascorbate Recycling

BACKGROUND

Human erythrocytes can take up dehydroascorbate on the glucose transporter 1 (GLUT 1) and reduce it to ascorbate. Intraerythrocyte ascorbate was proved to be directly responsible for decreased oxidation of extraerythrocytic ascorbate. In addition to spontaneous and irreversible loss of ascorbate in plasma, the hemodialysis (HD) process itself consumes plasma ascorbate. However, intraerythrocyte ascorbate status in uremic patients during HD has yet to be reported.

METHODS

Plasma and intraerythrocyte ascorbate, dehydroascorbate, GLUT 1 expression on erythrocyte membranes, and in vitro studies of "erythrocyte ascorbate recycling" were investigated in age- and sex-matched healthy subjects (control group) and HD patients (HD group).

RESULTS

Intraerythrocyte ascorbate concentrations decreased after 1 HD session compared with pre-HD and recovered to pre-HD values 2 days later, whereas plasma ascorbate concentrations did not recover. In vitro studies suggested that erythrocytes of HD patients have a stronger ability to maintain intracellular ascorbate concentrations compared with healthy subjects. This ability could be inhibited by cytochalasin B (GLUT 1 inhibitor). We also found increased GLUT 1 expression (P = 0.002) on erythrocyte membranes in the HD group compared with the control group.

CONCLUSION

Erythrocytes of uremic patients lost large amounts of ascorbate during HD, but regained it to the pre-HD level 2 days later. Enhanced GLUT 1 expression on erythrocyte membranes for HD patients may contribute to better preservation of intracellular ascorbate compared with healthy subjects.

Identification of a novel SEREX antigen, SLC2A1/GLUT1, in esophageal squamous cell carcinoma

We have carried out SEREX (serological identification of antigens by recombinant cDNA expression cloning), and identified SLC2A1 (solute carrier family 2/facilitated glucose transporter, member 1) as an antigen recognized by serum IgG antibodies in patients with esophageal squamous cell carcinoma (SCC). The levels of serum anti-SLC2A1 antibodies (s-SLC2A1-Abs), examined by enzyme-linked immunosorbent assay using bacterially expressed glutathione-S-transferase-SLC2A1 fusion protein, were significantly higher in patients with esophageal SCC than in healthy donors. When using a cut-off level as the mean + 2x standard deviations of healthy donors, a total of 12 (21%) out of 57 SCC patients were revealed as positive for s-SLC2A1-Abs. The presence of s-SLC2A1-Abs was not associated with either clinicopathological factors or survival. Because s-SLC2A1-Abs were not associated with the positivity of other conventional serum markers, a combination assay of s-SLC2A1-Abs with these conventional serum markers may be useful for the diagnosis and monitoring of esophageal SCC.

The prognostic value of the hypoxia markers CA IX and GLUT 1 and the cytokines VEGF and IL 6 in head and neck squamous cell carcinoma treated by radiotherapy +/- chemotherapy

Background

Several parameters of the tumor microenvironment, such as hypoxia, inflammation and angiogenesis, play a critical role in tumor aggressiveness and treatment response. A major question remains if these markers can be used to stratify patients to certain treatment protocols.

The purpose of this study was to investigate the inter-relationship and the prognostic significance of several biological and clinicopathological parameters in patients with head and neck squamous cell carcinoma (HNSCC) treated by radiotherapy ± chemotherapy.

Methods

We used two subgroups of a retrospective series for which CT-determined tumoral perfusion correlated with local control. In the first subgroup (n = 67), immunohistochemistry for carbonic anhydrase IX (CA IX) and glucose transporter-1 (GLUT-1) was performed on the pretreatment tumor biopsy. In the second subgroup (n = 34), enzyme linked immunosorbent assay (ELISA) was used to determine pretreatment levels of the cytokines vascular endothelial growth factor (VEGF) and interleukin-6 (IL-6) in serum. Correlation was investigated between tumoral perfusion and each of these biological markers, as well as between the markers mutually. The prognostic value of these microenvironmental parameters was also evaluated.

Results

For CA IX and GLUT-1, the combined assessment of patients with both markers expressed above the median showed an independent correlation with local control (p = 0.02) and disease-free survival (p = 0.04) with a trend for regional control (p = 0.06).

In the second subgroup, IL-6 pretreatment serum level above the median was the only independent predictor of local control (p = 0.009), disease-free survival (p = 0.02) and overall survival (p = 0.005).

Conclusion

To our knowledge, we are the first to report a link in HNSCC between IL-6 pretreatment serum levels and radioresistance in vivo. This link is supported by the strong prognostic association of pretreatment IL-6 with local control, known to be the most important parameter to judge radiotherapy responses.

Furthermore, the combined assessment of CA IX and GLUT-1 correlated independently with prognosis. This is a valuable indication that a combined approach is important in the investigation of prognostic markers.