Altered glycosylation and sialylation of serum proteins and lipid bound sialic acids in chronic renal failure

Elevated serum sialic acids, a potent biomarker of alloxan-induced type 1 diabetes in dogs by ethanolic extract of Anogeissus leiocarpus

Objectives

This study investigated serum sialic acids for a predictive and diagnostic biomarker of diabetes mellitus (DM) in dogs and its prognostic value with ethanolic extract of Anogeissus leiocarpus.

Design

Four groups of 3 dogs were used; non-diabetic controls (ND), diabetic-untreated (DU), diabetic insulin-treated (DI) and diabetic extract-treated (DE). Free serum sialic acids (FSSA) and erythrocyte surface sialic acids (ESSA) were assayed in all groups, pre-and post-induction of hyperglycaemia and results were presented as means ± standard error of means (SEM) and subjected to ANOVA using Tukey's post-hoc tests with GraphPad Prism® statistical package.

Results

FSSA increased in DU and plateaued at third week (61.8 ± 0.41 μg/ml), (P < 0.002) with additional 38.2 μg/ml (62%) generated, coinciding with hyperglycaemia. FSSA of DI increased but declined to 22.3 ± 1.55 μg/ml. Extract of Anogeissus leiocarpus effectively modulated FSSA in DE as increased value declined to 21.4 ± 0.78 μg/ml. Pre-induction DU ESSA (8.27 ± 0.11 μg/ml) significantly (P < 0.002) decreased by third week (2.33 ± 1.49 μg/ml), coinciding with hyperglycaemia. Strong negative correlation coefficient (r = -0.92) occurred between DU's FSSA and ESSA and ND (P < 0.03). Sialic acid expression in dog's insulin dependent diabetes mellitus (IDDM) is 18% lower than normal. Extract of A. leiocarpus restored ESSA completely. ESSA cleaved in DU, 5.94 μg/ml (72%), could not account for the extra FSSA (32.26 μg/ml); liver and kidneys are contributors.

Conclusion

FSSA predicts canine DM.

Highly Variable Sialylation Status of Donor-Specific Antibodies Does Not Impact Humoral Rejection Outcomes

Clinical outcome in antibody-mediated rejection (AMR) shows high inter-individual heterogeneity. Sialylation status of the Fc fragment of IgGs is variable, which could modulate their ability to bind to C1q and/or Fc receptors. In this translational study, we evaluated whether DSA sialylation influence AMR outcomes. Among 938 kidney transplant recipients for whom a graft biopsy was performed between 2004 and 2012 at Lyon University Hospitals, 69 fulfilled the diagnosis criteria for AMR and were enrolled. Sera banked at the time of the biopsy were screened for the presence of DSA by Luminex. The sialylation status of total IgG and DSA was quantified using Sambucus nigra agglutinin-based chromatography. All patients had similar levels of sialylation of serum IgGs (~2%). In contrast, the proportion of sialylated DSA were highly variable (median = 9%; range = 0–100%), allowing to distribute the patients in two groups: high DSA sialylation (n = 44; 64%) and low DSA sialylation (n = 25; 36%). The two groups differed neither on the intensity of rejection lesions (C4d, ptc, and g; p > 0.05) nor on graft survival rates (Log rank test, p = 0.99). in vitro models confirmed the lack of impact of Fc sialylation on the ability of a monoclonal antibody to trigger classical complement cascade and activate NK cells. We conclude that DSA sialylation status is highly variable but has not impact on DSA pathogenicity and AMR outcome.

Serum Total Sialic Acid and Highly Sensitive C-reactive Protein: Prognostic Markers for the Diabetic Nephropathy

Background:

This study was undertaken to evaluate and establish the role of total sialic acid (TSA) and highly sensitive C-reactive protein (hs-CRP) in type 2 diabetes mellitus (T2DM) and its correlation with complications such as diabetic nephropathy.

Materials and Methods:

One hundred fifty-seven patients with T2DM with nephropathy (DN) and 162 patients of T2DM without nephropathy (DM) along with 165 unrelated age and sex-matched healthy controls were included in the study. Serum glucose (fasting and postprandial) levels, renal profile, and lipid profile were done as per standard protocol. Serum TSA test levels and hs-CRP level were evaluated using thiobarbituric acid assay and immunoturbidimetric method respectively.

Results:

We observed a higher concentration of serum TSA (82.67 ± 6.63 mg/dl) and hs-CRP (3.2 ± 1.44 mg/L) in diabetic nephropathy than the diabetes mellitus group (73.83 ± 6.90 mg/dl and 2.07 ± 1.32 mg/L, respectively). Both TSA and hs-CRP levels were found significantly correlated with fasting and postprandial blood sugar, hemoglobin A1c, and urine microalbumin levels in both DM and DN groups. Multinomial logistic regression analysis showed that both TSA and hs-CRP was independently associated with diabetic nephropathy.

Conclusion:

High serum TSA and hs-CRP levels may increase the microangiopathic (diabetic nephropathy) complications of T2DM.

Quantification of monosaccharides through multiple-reaction monitoring liquid chromatography/mass spectrometry using an aminopropyl column

A simple, sensitive, and reproducible quantitative liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was designed for the simultaneous quantification of monosaccharides derived from glycoprotein and blood serum using a multiple-reaction monitoring (MRM) approach. Sialic acids and neutral monosaccharides were efficiently separated using an amino-bonded silica phase column. Neutral monosaccharide molecules were detected as their aldol acetate anion adducts [M + CH(3)CO(2)](-) using electrospray ionization in negative ion MRM mode, while sialic acids were detected as deprotonated ions [M-H](-). The new method did not require a reduction step, and exhibited very high sensitivity to carbohydrates with limits of detection of 1 pg for the sugars studied. The linearity of the described approach spanned over three orders of magnitude (pg to ng). The method was validated for monosaccharides originating from N-linked glycans attached to glycoproteins and glycoproteins found in human blood serum. The method effectively quantified monosaccharides originating from as little as 1 microg of glycoprotein and 5 microL of blood serum. The method was robust, reproducible, and highly sensitive. It did not require reduction, derivatization or postcolumn addition of reagents.

Contributions to senescence: non-enzymatic glycosylation of proteins

Non-enzymatic glycosylation (NEG) of in vivo proteins is believed to play an important role in the process of senescence. Diabetes mellitus also provides a convenient model to study senescence, as many of its sequalae, e.g. neuropathy, retinopathy, may be found in the post seventy year old normoglycaemic population. Discoveries of the mechanisms by which proteins become irreversibly modified by chronic high levels of glucose and other reducing sugars, has led to an increased understanding of the pathophysiological consequences of senescence. This may eventually enable the development of suitable therapies to improve age-related morbidity.

Pulsatile immunoreactive and bioactive luteinizing hormone secretion in adolescents with chronic renal failure. The Cooperative Study Group on Pubertal Development in Chronic Renal Failure (CSPCRF)

Delayed or arrested pubertal development is common in children with chronic renal failure (CRF). Normal puberty is initiated by the onset of episodic nocturnal secretion of luteinizing hormone (LH) containing an increasing proportion of bioactive hormone. To test the functional integrity of the hypothalamo-pituitary axis in CRF we measured immunoreactive (i-LH) and bioactive (bio-LH) plasma LH concentrations at 15-min intervals from 2000 to 0700 hours in 65 pubertal patients aged 10-23 years [46 boys/19 girls; 20 on conservative treatment (CT), 13 on dialysis (D), 32 with transplants (TP)]. i-LH was determined by radio-immunoassay and bio-LH by a mouse Leydig cell assay. Peak detection was performed by the cluster analysis computer programme. The mean (+/- SD) number of i-LH (in both sexes) and bio-LH pulses (in boys) per profile, and the mean peak area of i-LH (in both sexes) and bio-LH (in girls) were higher in TP than in CT or D patients. The ratio of bio-LH to i-LH increased during puberty in CT (G1 vs G4/5, 0.3 +/- 0.5 vs 1.8 +/- 0.,4) and TP (0.6 +/- 0.7 vs 1.8 +/- 0.7) but remained low in male D patients (0.4 +/- 0.7 vs 1.1 +/- 0.8). The ratios were subnormal, however, even in mature TP patients compared with healthy adults. The bio-LH/i-LH ratio and the bio-LH peak area best predicted integrated nocturnal testosterone concentrations in TP but not in uraemic male patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated serum and urine sialic acid levels in renal diseases

Total sialic acid (TSA) and lipid-associated sialic acid (LASA) concentrations were found to be significantly elevated in the sera of patients with chronic glomerulonephritis (CGN) and those with chronic renal failure (CRF) who were maintained on haemodialysis. The reference values for TSA and LASA were determined in the sera of 60 healthy subjects (33 males and 27 females) and showed no significant dependence on age and sex. No correlation existed between the TSA and LASA values, nor between TSA and LASA and the serum BUN and creatinine values in the patients and controls. A large amount of bound sialic acids was excreted in the urine of both groups of patients, although the serum sialic acid levels were increased.