Alpha 2HS-glycoprotein in the serum and urine of patients with renal diseases

Urinary Fetuin-A Fragments Predict Progressive Estimated Glomerular Filtration Rate Decline in Two Independent Type 2 Diabetes Cohorts of Different Ethnicities

INTRODUCTION

There is a great clinical need for novel markers to predict kidney function decline in patients with type 2 diabetes. We explored the potential of posttranslationally modified fetuin-A fragments in urine (uPTM-FetA) as such a marker.

METHODS

We included patients with type 2 diabetes from two independent, nonoverlapping prospective cohort studies. A cut-off for uPTM-FetA, measured via ELISA method, was determined using the Youden index in the primary cohort of patients with type 2 diabetes from Taiwan. Kidney endpoint was defined as an estimated glomerular filtration rate (eGFR) decline ≥30% from baseline, reaching of an eGFR <15 mL/min/1.73 m2, or a need of renal replacement therapy. Prospective associations were assessed in Cox regression models. All analyses were replicated in a cohort of patients with type 2 diabetes from the Netherlands.

RESULTS

In total, 294 patients with type 2 diabetes (age 61 ± 10 years, 55% male, eGFR 88 ± 16 mL/min/1.73 m2) were included in the primary cohort. During a follow-up of median 4.6 years, 42 participants (14%) experienced the kidney endpoint. Using the defined cut-off, a high uPTM-FetA was associated with a higher risk of renal function decline (Plog-rank < 0.0001). This association was similar in subgroups depending on albuminuria. This association remained, independent of age, sex, baseline eGFR, albuminuria, HbA1c, and other potential confounders (HR: 9.94; 95% CI: 2.96-33.40; p < 0.001 in the final model). Analyses in the validation cohort (376 patients with type 2 diabetes, age 64 ± 11 years, 66% male, eGFR 76 ± 24 mL/min/1.73 m2) using the same cut-off yielded similar results.

CONCLUSION

uPTM-FetA was independently associated with kidney function decline in patients with type 2 diabetes validated in a 2-cohort study. The significant additive predictive power of this biomarker from conventional risk factors suggests its clinical use for renal function progression in patients with type 2 diabetes.

Differential Proteomics of Urinary Exovesicles from Classical Galactosemic Patients Reveals Subclinical Kidney Insufficiency

Classical galactosemia is caused by a nearly complete deficiency of galactose-1-phosphate uridyltransferase (GALT; EC 2.7.712), resulting in a severely impaired galactose metabolism with galactose-1-phosphate and galactitol accumulation. Even on a galactose-restricted diet, patients develop serious long-term complications of the central nervous system and ovaries that may result from chronic cell-toxic effects exerted by endogenous galactose. To address the question of whether disease-associated cellular perturbations could affect the kidney function of the patients, we performed differential proteomics of detergent-resistant membranes from urinary exovesicles. Galactosemic samples (showing drastic shifts from high-mannose to complex-type N-glycosylation on exosomal N-glycoproteins) and healthy, sex-matched controls were analyzed in quadruplex iTRAQ experiments performed in biological and technical replicates. Particularly in the female patient group, the most striking finding was a drastic increase of abundant serum (glyco)proteins, like albumin, leucine-rich α-2-glycoprotein, fetuin, immunoglobulins, prostaglandin H2 d-isomerase, and α-1-microglobulin protein (AMBP), pointing to a subclinical failure of kidney filter function in galactosemic patients and resulting in a heavy overload of exosomal membranes with adsorbed serum (glyco)proteins. Several of these proteins are connected to TBMN and IgAN, proteinuria, and renal damage. The impairment of renal protein filtration was also indicated by increased protein contents derived from extracellular matrices and lysosomes.

Soluble CD40 ligand, high sensitive C-reactive protein and fetuin-A levels in patients with essential thrombocythemia

BACKGROUND

CD40 ligand (CD40L) is expressed on the surface of activated platelets and activated T lymphocytes. Circulating soluble CD40 ligand (sCD40L) is formed from these molecules proteolytically. Fetuin-A is a potent antiinflammatory cytokine.

AIM OF THE STUDY

In this study, we aim to investigate sCD40L levels to determine whether there is platelet activation and to measure high sensitive C-reactive protein (hs-CRP) levels to demonstrate if this leads to an inflammatory process and also to study fetuin-A levels to see if there is any concomitant antiinflammatory event in patients with essential thrombocythemia (ET).

METHODS

We compared 30 patients with essential thrombocythemia with 30 control subjects and in these patients we measured levels of sCD40L, hs-CRP and fetuin-A.

RESULTS

sCD40L levels were significantly higher in the ET group compared to the control group (30.6±14.4 vs. 18.5±8.9, p=0.001). Although fetuin-A levels showed a slight trend to be increased in ET patients, the difference did not reach significance (4.5±4.2 vs. 3.2±2.1, p=0.158). There were no statistically significant differences in hs-CRP levels (24.6±4.9 vs. 25.0±5.2, p=0.750).

CONCLUSION

sCD40L was significantly higher in patients with an ET without any association with an inflammatory process and we believe this may be a marker of platelet regeneration.

Comparison of the course of biomarker changes and kidney injury in a rat model of drug-induced acute kidney injury

OBJECTIVE

To aid in evaluating the performance of biomarkers, we measured kidney injury biomarkers in rat models of drug-induced acute kidney injury.

METHODS AND RESULTS

Rats were treated with site-specific nephrotoxins, puromycin, gentamicin, cisplatin, or 2-bromoethylamine. Fifteen biomarkers (β-2-microglobulin, calbindin, clusterin, cystatin-C, KIM-1, GST-α, GST-μ, NGAL, osteopontin, EGF, TIMP-1, VEGF, albumin, RPA-1, and urinary total protein) were examined in comparison with BUN, serum creatinine, and NAG. Some biomarkers, which were different depending in each nephrotoxin, showed ability to detect the prodromal stage of drug-induced kidney injury. Characteristic changing patterns of biomarkers were also found depending on the specific lesion site in the kidney.

CONCLUSION

These data suggested that establishment of a suitable biomarker panel would facilitate detection of site-specific kidney injury with high sensitivity.

Reduced serum fetuin-A in nephrotic children: a consequence of proteinuria?

BACKGROUND

The extracellular protein fetuin-A is a potent soluble inhibitor of calcification, and its deficiency has been associated with vascular calcification in dialysis patients. In proteinuric patients, significant urinary losses of fetuin-A may cause low serum fetuin-A levels.

METHODS

In a cross-sectional study, urinary/serum concentrations of fetuin-A were investigated in proteinuric children with glomerular diseases and preserved renal function (n = 58) in comparison to healthy controls (n = 246).

RESULTS

Mean fetuin-A serum concentrations were clearly reduced in children with nephrotic syndrome (0.25 ± 0.14 g/l, p < 0.001), slightly reduced in children with large proteinuria (0.39 ± 0.15 g/l, p < 0.05), and comparable to controls in those with mild proteinuria (0.45 ± 0.14 vs. 0.46 ± 0.12 g/l). Fetuin-A was positively correlated with serum protein (r = 0.58), albumin (r = 0.57), and calcium (r = 0.64), but negatively correlated with proteinuria (r = -0.41), albuminuria (r = -0.46), and urinary fetuin-A excretion (r = -0.48; each p < 0.001). The fractional excretion of fetuin-A was significantly associated with the degree of proteinuria and serum fetuin-A levels. However, the urinary loss of fetuin-A and albumin in nephrotic children differed by three orders of magnitude and the mean fractional excretion of fetuin-A was only 1/10 of that of albumin (0.016 ± 0.029 vs. 0.162 ± 0.403%; p < 0.001).

CONCLUSIONS

Fetuin-A is clearly reduced in children with nephrotic syndrome and associated with the degree of hypoalbuminemia. This is due to urinary fetuin-A loss and/or reduced hepatic synthesis. Persistent fetuin-A deficiency may have an impact on cardiovascular morbidity in nephrotic children.

Fetuin-A and interleukin-18 levels in ankylosing spondylitis

AIM

Interleukin-18 (IL-18) and fetuin-A have been implicated in atherosclerosis. Preliminary evidence suggests that ankylosing spondylitis (AS) is associated with an increased risk of atherosclerosis. The aim of the present study was to investigate possible abnormalities in IL-18 and fetuin-A levels in AS.

METHODS

Subjects without established cardiovascular (CV) risk factors were studied. Fasting glucose, serum lipids, high sensitive C-reactive protein (hsCRP), erythrocyte sedimentation rate, IL-18 and fetuin-A were assessed. Patients were also evaluated with the Bath Ankylosing Spondylitis Metrology Index, Bath Ankylosing Spondylitis Functional Index, and the Bath Ankylosing Spondylitis Disease Activity Index.

RESULTS

Fourty-five patients with AS (37.4 +/- 9.7 years; 35M/10F) and 29 controls (35.5 +/- 11.1 years; 21M/8F) were studied. Fetuin-A levels were significantly higher in AS patients compared to controls (1023.5 +/- 171.6 vs. 856.9 +/- 207.9 microg/mL, P < 0.001). IL-18 levels were also higher in the AS group but the difference was not significant (184 +/- 186 vs. 140 +/- 115, P = 0.1). Significant but weak correlations were found between fetuin-A, IL-18, hsCRP, low density lipoprotein cholesterol, and triglyceride levels (P < 0.05; r = 0.4, 0.3, 0.2, and 0.3 respectively). Comparison of subjects with respect to the treatment type, disease activity and history of peripheral arthritis yielded no difference regarding fetuin-A and IL-18 between groups.

CONCLUSION

Fetuin-A and IL-18 levels seem to be increased in AS patients regardless of disease activity and treatment type.

Decreased serum fetuin-A levels are associated with coronary artery diseases

BACKGROUND

To analyze Fetuin-A levels and soluble cellular adhesion molecules in patients with acute coronary syndrome.

METHODS AND RESULTS

Serum Fetuin-A and intercellular adhesion molecule-1 (sICAM-1), vascular cellular adhesion molecule-1 (sVCAM-1) levels were examined in 127 patients who presented with chest pain. These patients were classified in three groups: stable angina (SA, n=51), myocardial infarction (MI, n=34) and non-cardiac group (n=42). Logarithmic transformations were made for Fetuin-A levels. Log-Fetuin-A levels were higher in non-cardiac subjects compared to MI and SA patients (p<0.05). Patients with SA showed lower levels than controls but higher levels as compared to MI patients. After controlling for age and gender, levels of sVCAM-1 and sICAM-1 in patients with coronary atherosclerosis were not different from those in non-cardiac subjects.

CONCLUSION

Serum levels of soluble VCAM-1, ICAM-1 were not related to coronary artery disease (CAD), but fetuin-A levels seems to be decreased in SA and MI patients. Low fetuin-A may play a role in the pathophysiology of CAD.

Decreased levels of circulating alpha2-Heremans-Schmid glycoprotein/Fetuin-A (AHSG) in patients with rheumatoid arthritis

OBJECTIVE

Alpha2-Heremans Schmid glycoprotein/Fetuin-A (AHSG) is a circulating negative acute-phase protein, which inhibits bimineralization. It is often considered as a potential mediator between chronic inflammation and cardiovascular diseases. The metabolism of AHSG in patients with rheumatoid arthritis (RA) is unknown.

METHODS

Serum AHSG concentrations were measured in 102 patients with RA using a newly developed indirect enzyme-linked immunosorbent assay (ELISA).

RESULTS

The serum AHSG levels in the RA patients were significantly lower than that in healthy volunteers (249.8 +/- 84.1 vs 425.0 +/- 93.0 microg/ml, P<0.0001). Serum C-reactive protein concentration and erythrocyte sedimentation rate were inversely correlated, while albumin, hemoglobin and total cholesterol were positively correlated with AHSG. Current serum AHSG levels did not affect the presence of aortic calcification, whereas cumulative glucocorticoid dosage was significantly related to aortic calcification (P=0.005).

CONCLUSION

Serum AHSG levels were significantly decreased in patients with RA. The levels reflected inflammatory and malnutritional conditions. Its role in the development of cardiovascular diseases or inflammatory bone resorption remain uncertain in RA patients.

Pathogenesis of vascular calcification in dialysis patients

Soft-tissue and vascular calcification are highly prevalent in end-stage renal disease (ESRD). Vascular calcifications manifest as both medial and intimal calcification of arteries and are a hallmark of the accelerated atherosclerosis observed in uremia. The nature of vascular calcification is progressive, and is associated with arterial stiffness and increased cardiovascular mortality. Age, duration of dialysis, and diabetes mellitus are clear determinants of the severity of vascular calcification; however, more recently novel insights into the pathomechanisms of unwanted calcification processes have been gained. Disturbances of mineral metabolism such as hyperphosphatemia and hypercalcemia appear to contribute to progressive calcification, not only by passive precipitation but by actively inducing changes in vascular smooth muscle cell behavior toward an osteoblast-like phenotype. Specific calcium-regulatory proteins may act locally or systemically as calcification inhibitors. Dysregulations of calcification inhibitors, including fetuin-A, matrix Gla protein, osteoprotegerin, and pyrophosphates may also be pathophysiologically relevant factors in the context of uremic extraosseous calcification. In this context, low serum fetuin-A levels were recently found to be associated with increased mortality in cohorts of dialysis patients. This overview intends to summarize current knowledge of the scientific concepts involved in the pathogenesis of extraosseous calcification in ESRD.

Kidney-bone, bone-kidney, and cell-cell communications in renal osteodystrophy

The relationship between bone and the kidney in renal osteodystrophy is a complex interplay of kidney to bone connections, bone to kidney connections, and cell to cell connections. In addition, such interactions have a profound effect on the vasculature. In this review, we discuss the role of the bone morphogenetic proteins (BMPs) in the skeleton, kidney, and vasculature. In addition, we propose that deficiencies of these BMPs seen in chronic kidney disease (CKD) result in decreased bone remodeling and a compensatory secondary hyperparathyroidism (high turnover state). Treatment of the hyperparathyroidism blocks this compensatory arm and thus decreased bone remodeling occurs (low turnover). We review animal models of CKD in which treatment with BMP-7 resulted in normalization of both high and low turnover states. Finally, we discuss vascular calcification as it relates to bone metabolism. We discuss the roles of BMP-7 and 2 other bone regulatory proteins, osteoprotegerin (OPG) and alpha2-HS glycoprotein (AHSG, human fetuin), in the human vasculature and their implications for vascular calcification.

Serum alpha 2-HS glycoprotein concentration in patients with hematological malignancies. A follow-up study

We observed significantly reduced serum alpha 2-HS glycoprotein concentrations in patients with acute lymphocytic, acute nonlymphocytic, chronic granulocytic and chronic myelomonocytic leukemias, Hodgkin's and non-Hodgkin's lymphomas, myelofibrosis, and multiple myeloma, but not in patients with chronic lymphocytic leukemia and polycythemia vera, as compared with healthy controls. We followed the serum level of the protein for 18 months. Patients with infectious complications, those receiving cytostatic treatment, and those in the preterminal period had further reduced serum alpha 2-HS glycoprotein levels. The reduction of serum alpha 2-HS glycoprotein concentration was primarily due to decreased production caused by infiltration of the liver, a hepatotoxic effect of cytostatic treatment, and, to a lesser degree, to increased consumption. We found statistically significant negative correlations between serum alpha 2-HS glycoprotein concentration and erythrocyte sedimentation rate, serum aspartate aminotransferase and alkaline phosphatase activities, and IgG and IgM concentrations. The determination of the alpha 2-HS glycoprotein concentration is useful for the assessment and follow-up of the clinical status and therapy of patients with hematological malignancies and also has prognostic significance.

Noncollagenous proteins in normal and pathological human bone

The concentrations of alpha 2HS-glycoprotein, albumin, and sialic acid were measured in the bone of 28 normal individuals and 6 patients with osteogenesis imperfecta, 3 patients with Paget's disease, and 4 patients with either renal osteodystrophy, osteoporosis, osteomalacia, or osteopetrosis. The concentration of alpha 2HS-glycoprotein in neonatal bone was 3 X higher than in bone from children and 7 X higher than in adult bone. The concentrations of albumin and sialic acid in neonatal bone were 1.5 X higher that in bone from children and twice the levels in adult bone. The concentrations of alpha 2HS-glycoprotein, albumin and sialic acid were above the normal mean values in the patients with osteogenesis imperfecta, and 4 patients had significantly raised levels of one or more of these proteins. The concentrations of these noncollagenous proteins were also significantly raised in Paget's disease, and the alpha 2HS-glycoprotein was significantly raised in renal osteodystrophy. The lowest level of alpha 2HS-glycoprotein was in osteopetrotic bone and the lowest levels of albumin and sialic acid were in osteoporotic bone. The results of this study suggest that the concentrations of alpha 2HS-glycoprotein, albumin, and sialic acid in bone are related to the rate of bone turnover.