High glucose disrupts oligosaccharide recognition function via competitive inhibition: a potential mechanism for immune dysregulation in diabetes mellitus

High sensitive detection of carbohydrate binding proteins in an ELISA-solid phase assay based on multivalent glyconanoparticles

Improved detection of anti-carbohydrate antibodies is a need in clinical identification of biomarkers for cancer cells or pathogens. Here, we report a new ELISA approach for the detection of specific immunoglobulins (IgGs) against carbohydrates. Two nanometer gold glyconanoparticles bearing oligosaccharide epitopes of HIV or Streptococcus pneumoniae were used as antigens to coat ELISA-plates. A ~3,000-fold improved detection of specific IgGs in mice immunized against S. pneumoniae respect to the well known BSA-glycoconjugate ELISA was achieved. Moreover, these multivalent glyconanoparticles have been employed in solid phase assays to detect the carbohydrate-dependent binding of human dendritic cells and the lectin DC-SIGN. Multivalent glyconanoparticles in ELISA provide a versatile, easy and highly sensitive method to detect and quantify the binding of glycan to proteins and to facilitate the identification of biomarkers.

Prevalence of bacterial contamination of glucose test strips in individual single-use packets versus multiple-use vials

BACKGROUND

Glucose measurement is the cornerstone of diabetes control. In the hospital setting, the same device and package of test strips (50 or 100 strips) can be used to monitor glucose in several patients, which can increase cross contamination. The objective of our study is to measure bacterial contamination in glucose test strips, comparing results in individual single-use packets (one hospital) versus multi-use vials (two hospitals) in Spain.

METHODS

Test strips were collected from five different wards. Each hospital also collected two unopened vials from a single ward as controls. They were sent to a reference laboratory for microbiologic study. A number equal or higher than two colony forming units per strip was considered as a positive result.

RESULTS

Out of 423 glucose test strips collected and cultured, 146 were contaminated (34%); only 7% of individually packed strips were contaminated versus 45% of strips packed in multi-use vials, with a high statistical significance (p < .001).

CONCLUSIONS

In the strips from multi-use vials, a high contamination rate was found and highly pathogenic organisms were identified, such as methicillin-resistant Staphylococcus epidermidis or Staphylococcus hemolyticus. In contrast, in strips packed individually, there was a much lower contamination rate and no such pathogen organisms were found. Therefore, in the hospital setting, the use of blood glucose test strips in individual packages would be more advantageous (mainly from a clinical point of view, but also from a financial one) than those packed in multi-use vials.

De novo 19p13.2 microdeletion encompassing the insulin receptor and resistin genes in a patient with obesity and learning disability

Genetic studies have provided novel insights of appetite regulation and pathophysiology of obesity. The adipose tissue is an active endocrine organ secreting several hormones contributing to insulin resistance and the development of the comorbidities of obesity, such as type 2 diabetes and cardiovascular disease. Herein, we report on a patient with severe obesity and mild learning disability with a 750 kb de novo deletion of chromosome 19. The deletion encompasses several genes, including resistin and the first part of the insulin receptor, genes that are relevant for obesity. This novel deletion may therefore represent a region for obesity research. Plasma analyses and gene expression demonstrated that the deletion resulted in haploinsufficiency for resistin and insulin receptor in the patient compared to controls. We then studied the biochemical and adipocytokine profile in these subjects. We observed no differences in glucose and lipid parameters between the patient and the controls. Thus, haploinsufficiency of insulin receptor and resistin does not appear to influence glucose and lipid metabolism. However, the patient had considerably higher values of adiponectin and TNFα than controls. In conclusion, we identified a 19p13.2 microdeletion encompassing the insulin receptor and resistin genes resulting in haploinsufficiency in an obese, but otherwise healthy patient. No firm conclusions could be drawn regarding the potential effect of the microdeletion on adipokine profile.

A role for polyglucans in a model sea urchin embryo cellular interaction

The enzymatic activities of commercially prepared glycosidases were verified by direct chemical assays using defined substrates and fixed and live sea urchin (Lytechinus pictus) embryos to determine if a model cellular interaction of interest to developmental biologists for over a century (interaction of archenteron tip and roof of the blastocoel) was mediated by glycans. Glycosidases (active and denatured) were incubated with microdissected archenterons and blastocoel roofs in a direct assay to learn if their enzymatic activities could prevent the normal adhesive interaction. Of the five glycosidases tested only β-amylase (an exoglycosidase) immediately inhibited the interaction at relatively low unit activity. α-Amylase (an endoglycosidase) had no measurable effect, while other glycosidases (α-glucosidase, β-glucosidase, β-galactosidase) only substantially inhibited adhesion after a 12-h incubation. We demonstrated that the five glycosidases were active (not inhibited) in the presence of embryo materials, and that cleaved sugars could be detected directly after incubation of some enzymes with the embryos. The biochemical purity of the enzymes was examined using gel electrophoresis under denaturing conditions, and the absence of contaminating proteases was confirmed using Azocoll™ substrate. As we cannot entirely rule out the presence of minor contaminating enzymatic activities, only inhibitions of adhesion after very short incubations with enzyme were considered significant and biologically relevant. Although glycans in indirect experiments have been implicated in mediating the interaction of the tip of the archenteron and roof of the blastocoel, to our knowledge, this is the first study that directly implicates polyglucans with terminal 1,4-linked glucose residues in this adhesive event.

Hyperglycemic conditions inhibit C3-mediated immunologic control of Staphylococcus aureus

BACKGROUND

Diabetic patients are at increased risk for bacterial infections; these studies provide new insight into the role of the host defense complement system in controlling bacterial pathogens in hyperglycemic environments.

METHODS

The interactions of complement C3 with bacteria in elevated glucose were assayed for complement activation to opsonic forms, phagocytosis and bacterial killing. C3 was analyzed in euglycemic and hyperglycemic conditions by mass spectrometry to measure glycation and structural differences.

RESULTS

Elevated glucose inhibited S. aureus activation of C3 and deposition of C3b and iC3b on the bacterial surface. S. aureus-generated C5a and serum-mediated phagocytosis by neutrophils were both decreased in elevated glucose conditions. Interestingly, elevated glucose increased the binding of unactivated C3 to S. aureus, which was reversible on return to normal glucose concentrations. In a model of polymicrobial infection, S. aureus in elevated glucose conditions depleted C3 from serum resulting in decreased complement-mediated killing of E. coli. To investigate the effect of differing glucose concentration on C3 structure and glycation, purified C3 incubated with varying glucose concentrations was analyzed by mass spectrometry. Glycation was limited to the same three lysine residues in both euglycemic and hyperglycemic conditions over one hour, thus glycation could not account for observed changes between glucose conditions. However, surface labeling of C3 with sulfo-NHS-biotin showed significant changes in the surface availability of seven lysine residues in response to increasing glucose concentrations. These results suggest that the tertiary structure of C3 changes in response to hyperglycemic conditions leading to an altered interaction of C3 with bacterial pathogens.

CONCLUSIONS

These results demonstrate that hyperglycemic conditions inhibit C3-mediated complement effectors important in the immunological control of S. aureus. Mass spectrometric analysis reveals that the glycation state of C3 is the same regardless of glucose concentration over a one-hour time period. However, in conditions of elevated glucose C3 appears to undergo structural changes.