Human fetuin/alpha2HS-glycoprotein level as a novel indicator of liver cell function and short-term mortality in patients with liver cirrhosis and liver cancer

Causes and metabolic consequences of Fatty liver

Type 2 diabetes and cardiovascular disease represent a serious threat to the health of the population worldwide. Although overall adiposity and particularly visceral adiposity are established risk factors for these diseases, in the recent years fatty liver emerged as an additional and independent factor. However, the pathophysiology of fat accumulation in the liver and the cross-talk of fatty liver with other tissues involved in metabolism in humans are not fully understood. Here we discuss the mechanisms involved in the pathogenesis of hepatic fat accumulation, particularly the roles of body fat distribution, nutrition, exercise, genetics, and gene-environment interaction. Furthermore, the effects of fatty liver on glucose and lipid metabolism, specifically via induction of subclinical inflammation and secretion of humoral factors, are highlighted. Finally, new aspects regarding the dissociation of fatty liver and insulin resistance are addressed.

Profiling of serum and tissue high abundance acute-phase proteins of patients with epithelial and germ line ovarian carcinoma

Background

Acute-phase response involves the simultaneous altered expression of serum proteins in association to inflammation, infection, injury or malignancy. Studies of the acute-phase response usually involve determination of the levels of individual acute-phase serum proteins. In the present study, the acute-phase response of patients with epithelial (EOCa) and germ-line (GOCa) ovarian carcinoma was investigated using the gel-based proteomic approach, a technique which allowed the simultaneous assessment of the levels of the acute-phase serum high abundance proteins. Data obtained were validated using ELISA and immunostaining of biopsy samples.

Results

Enhanced expression of clusterin (CLU), α₁-antitrypsin, haptoglobin and leucine rich glycoprotein was detected in all patients. However, the levels of α₁-antichymotrypsin (ACT) was only enhanced in EOCa patients, while patients with GOCa were typically characterized by elevated levels of ceruloplasmin but lower levels of α₂-HS glycoprotein. The enhanced expression of CLU in EOCa and GOCa patients and up-regulated expression of ACT specifically in EOCa patients were confirmed by ELISA. Immunohistochemical staining of biopsy samples of EOCa and GOCa patients demonstrated correlation of the acute-phase protein expression.

Conclusion

Patients with EOCa and GOCa demonstrated distinctive aberrant expression of serum and tissue high abundance acute-phase proteins compared to negative control women.

Serum alpha 2-HS glycoprotein predicts survival in patients with glioblastoma

BACKGROUND

Glioblastoma, the most common primary brain tumor, has variable prognosis. We aimed to identify serum biomarkers that predict survival of patients with glioblastoma.

METHODS

In phase 1 (biomarker discovery), SELDI-TOF mass spectra were studied in 200 serum samples from 58 control subjects and 36 patients with grade II astrocytoma, 15 with anaplastic astrocytoma, and 91 with glioblastoma. To identify potential biomarkers, we searched for peptide peaks that changed progressively in size with increasing malignancy. One peak, identified as the B-chain of alpha 2-Heremans-Schmid glycoprotein (AHSG), was less prominent with increasing tumor grade. We therefore investigated AHSG as a survival predictor in glioblastoma. We measured serum AHSG by turbidimetry and determined indices of malignancy, including tumor proliferation (Ki67 immunolabel) and necrosis (tumor lipids on magnetic resonance spectroscopy). In phase 2 (biomarker validation), the prognostic power of AHSG was validated in an independent group of 72 glioblastoma patients.

RESULTS

Median survival was longer (51 vs 29 weeks) in glioblastoma patients with normal vs low serum AHSG concentrations (hazard ratio 2.7, 95% CI 1.5-5.0, P <0.001), independent of age and Karnofsky score. Serum AHSG inversely correlated with Ki-67 immunolabeling and tumor lipids. A prognostic index combining serum AHSG with patient age and Karnofsky score separated glioblastoma patients with short (<3 months) and long (>2 years) median survival. The prognostic value of serum AHSG was validated in a different cohort of glioblastoma patients.

CONCLUSIONS

We conclude that serum AHSG concentration, measured before starting treatment, predicts survival in patients with glioblastoma.

Vascular calcification inhibitors in relation to cardiovascular disease with special emphasis on fetuin-A in chronic kidney disease

The mortality rate is extremely high in chronic kidney disease (CKD), primarily due to the high prevalence of cardiovascular disease (CVD) in this patient group. Apart from traditional Framingham risk factors, evidences suggest that nontraditional risk factors, such as inflammation, oxidative stress, endothelial dysfunction, and vascular calcification also contribute to this extremely high risk of CVD. Disturbance in the mineral metabolism, especially in the ions of Ca and PO4, are linked to enhanced calcification of blood vessels. Although the mechanism(s) of this enhanced calcification process are not fully understood, current knowledge suggests that a large number (and an imbalance between them) of circulating promoters and inhibitors of the calcification process, that is, fetuin-A (or alpha 2-Heremans-Schmid glycoprotein, AHSG), matrix-Gla protein (MGP), osteoprotegerin (OPG), osteopontin (OPN), bone morphogenetic proteins (BMPs), and inorganic pyrophosphate (PPi), are involved in the deterioration of vascular tissue. Thus, an imbalance in these factors may contribute to the high prevalence of vascular complications in CKD patients. Among these mediators, studies on fetuin-A deserve further attention as clinical studies consistently show that fetuin-A deficiency is associated with vascular calcification, all-cause and cardiovascular mortality in CKD patients. Both chronic inflammation and the uremic milieu per se may contribute to fetuin-A depletion, as well as specific mutations in the AHSG gene. Recent experimental and clinical studies also suggest an intriguing link between fetuin-A, insulin resistance, and the metabolic syndrome.

Human serum fetuin A/alpha2HS-glycoprotein level is associated with long-term survival in patients with alcoholic liver cirrhosis, comparison with the Child-Pugh and MELD scores

Background

Serum concentration of fetuin A/α2HS-glycoprotein (AHSG) is a good indicator of liver cell function and 1-month mortality in patients with alcoholic liver cirrhosis and liver cancer. We intended to determine whether decreased serum AHSG levels are associated with long-term mortality and whether the follow-up of serum AHSG levels can add to the predictive value of the Child-Pugh (CP) and MELD scores.

Methods

We determined serum AHSG concentrations in 89 patients by radial immunodiffusion. Samples were taken at the time of enrolment and in the 1^st, 3^rd, 6^th, and the 12^th month thereafter.

Results

Forty-one patients died during the 1-year follow-up period, 37 of them had liver failure. Data of these patients were analysed further. Deceased patients had lower baseline AHSG levels than the 52 patients who survived (293 ± 77 vs. 490 ± 106 μg/ml, mean ± SD, p < 0.001). Of all laboratory parameters serum AHSG level, CP and MELD scores showed the greatest difference between deceased and survived patients. The cutoff AHSG level 365 μg/ml could differentiate between deceased and survived patients (AUC: 0.937 ± 0.025, p < 0.001, sensitivity: 0.865, specificity: 0.942) better than the MELD score of 20 (AUC: 0.739 ± 0.052, p < 0.001, sensitivity: 0.595, specificity: 0.729). Initial AHSG concentrations < 365 μg/ml were associated with high mortality rate (91.4%, relative risk: 9.874, 95% C.I.: 4.258–22.898, p < 0.001) compared to those with ≥ 365 μg/ml (9.3%). Fourteen out of these 37 fatalities occurred during the first month of observation. During months 1–12 low AHSG concentration proved to be a strong indicator of mortality (relative risk: 9.257, 95% C.I.: 3.945–21.724, p < 0.001). Multiple logistic regression analysis indicated that decrease of serum AHSG concentration was independent of all variables that differed between survived and deceased patients during univariate analysis. Multivariate analysis showed that correlation of low serum AHSG levels with mortality was stronger than that with CP and MELD scores. Patients with AHSG < 365 μg/ml had significantly shortened survival both in groups with MELD < 20 and MELD ≥ 20 (p < 0.0001 and p = 0.0014, respectively).

Conclusion

Serum AHSG concentration is a reliable and sensitive indicator of 1-year mortality in patients with alcoholic liver cirrhosis that compares well to the predictive value of CP score and may further improve that of MELD score.

Investigation of an albumin-enriched fraction of human serum and its albuminome

The removal of albumin and other high abundance proteins is a routine first step in the analysis of serum and plasma proteomes. However, as albumin can bind proteins and peptides, there is a universal concern as to how the serum proteome is changed by the removal of albumin. To address this concern, the current study was designed to identify proteins and peptides removed from the serum during albumin depletion; to determine which of these are bound to albumin (rather than copurified) and whether the bound proteins are intact proteins or peptide fragments. Sequential, independent analyses including both anti-albumin antibody (anti-HSA) affinity chromatography and SEC were used to isolate albumin-bound proteins. RP-HPLC and 1-D SDS-PAGE were then used to further separate the proteins prior to identification by MS/MS. Finally, whole protein molecular weight (MW) MS measurements coupled with protein coverage obtained by MS were combined to assess whether the bound proteins were intact or peptide fragments. Combining the results from multiple approaches, 35 proteins, of which 24 are intact, were found to be associated with albumin, and they include both known high and low abundance proteins.

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.

Alpha2-Heremans-Schmid glycoprotein/fetuin-A is associated with insulin resistance and fat accumulation in the liver in humans

OBJECTIVE

The alpha(2)-Heremans-Schmid glycoprotein (AHSG; fetuin-A in animals) impairs insulin signaling in vitro and in rodents. Whether AHSG is associated with insulin resistance in humans is under investigation. In an animal model of diet-induced obesity that is commonly associated with hepatic steatosis, an increase in Ahsg mRNA expression was observed in the liver. Therefore, we hypothesized that the AHSG plasma protein, which is exclusively secreted by the liver in humans, may not only be associated with insulin resistance but also with fat accumulation in the liver.

RESEARCH DESIGN AND METHODS

Data from 106 healthy Caucasians without type 2 diabetes were included in cross-sectional analyses. A subgroup of 47 individuals had data from a longitudinal study. Insulin sensitivity was measured by a euglycemic-hyperinsulinemic clamp, and liver fat was determined by (1)H magnetic resonance spectroscopy.

RESULTS

AHSG plasma levels, adjusted for age, sex, and percentage of body fat, were higher in subjects with impaired glucose tolerance compared with subjects with normal glucose tolerance (P = 0.006). AHSG plasma levels were negatively associated with insulin sensitivity (r = -0.22, P = 0.03) in cross-sectional analyses. Moreover, they were positively associated with liver fat (r = 0.27, P = 0.01). In longitudinal analyses, under weight loss, a decrease in liver fat was accompanied by a decrease in AHSG plasma concentrations. Furthermore, high AHSG levels at baseline predicted less increase in insulin sensitivity (P = 0.02).

CONCLUSIONS

We found that high AHSG plasma levels are associated with insulin resistance in humans. Moreover, AHSG plasma levels are elevated in subjects with fat accumulation in the liver. This is consistent with a potential role of AHSG as a link between fatty liver and insulin resistance.

Fetuin-A, a hepatocyte-specific protein that binds Plasmodium berghei thrombospondin-related adhesive protein: a potential role in infectivity

Malaria infection is initiated when the insect vector injects Plasmodium sporozoites into a susceptible vertebrate host. Sporozoites rapidly leave the circulatory system to invade hepatocytes, where further development generates the parasite form that invades and multiplies within erythrocytes. Previous experiments have shown that the thrombospondin-related adhesive protein (TRAP) plays an important role in sporozoite infectivity for hepatocytes. TRAP, a typical type-1 transmembrane protein, has a long extracellular region, which contains two adhesive domains, an A-domain and a thrombospondin repeat. We have generated recombinant proteins of the TRAP adhesive domains. These TRAP fragments show direct interaction with hepatocytes and inhibit sporozoite invasion in vitro. When the recombinant TRAP A-domain was used for immunoprecipitation against hepatocyte membrane fractions, it bound to alpha2-Heremans-Schmid glycoprotein/fetuin-A, a hepatocyte-specific protein associated with the extracellular matrix. When the soluble sporozoite protein fraction was immunoprecipitated on a fetuin-A-adsorbed protein A column, TRAP bound this ligand. Importantly, anti-fetuin-A antibodies inhibited invasion of hepatocytes by sporozoites. Further, onset of malaria infection was delayed in fetuin-A-deficient mice compared to that in wild-type C57BL/6 mice when they were challenged with Plasmodium berghei sporozoites. These data demonstrate that the extracellular region of TRAP interacts with fetuin-A on hepatocyte membranes and that this interaction enhances the parasite's ability to invade hepatocytes.

The serum protein alpha 2-Heremans-Schmid glycoprotein/fetuin-A is a systemically acting inhibitor of ectopic calcification

Ectopic calcification is a frequent complication of many degenerative diseases. Here we identify the serum protein alpha2-Heremans-Schmid glycoprotein (Ahsg, also known as fetuin-A) as an important inhibitor of ectopic calcification acting on the systemic level. Ahsg-deficient mice are phenotypically normal, but develop severe calcification of various organs on a mineral and vitamin D-rich diet and on a normal diet when the deficiency is combined with a DBA/2 genetic background. This phenotype is not associated with apparent changes in calcium and phosphate homeostasis, but with a decreased inhibitory activity of the Ahsg-deficient extracellular fluid on mineral formation. The same underlying principle may contribute to many calcifying disorders including calciphylaxis, a syndrome of severe systemic calcification in patients with chronic renal failure. Taken together, our data demonstrate a critical role of Ahsg as an inhibitor of unwanted mineralization and provide a novel therapeutic concept to prevent ectopic calcification accompanying various diseases.

Association of low fetuin-A (AHSG) concentrations in serum with cardiovascular mortality in patients on dialysis: a cross-sectional study

BACKGROUND

Vascular calcification is the most prominent underlying pathological finding in patients with uraemia, and is a predictor of mortality in this population. Fetuin-A (alpha2-Heremans Schmid glycoprotein; AHSG) is an important circulating inhibitor of calcification in vivo, and is downregulated during the acute-phase response. We aimed to investigate the hypothesis that AHSG deficiency is directly related to uraemic vascular calcification.

METHODS

We did a cross-sectional study in 312 stable patients on haemodialysis to analyse the inter-relation of AHSG and C-reactive protein (CRP) and their predictive effect on all-cause and cardiovascular mortality, over a period of 32 months. Subsequently, we tested the capacity of serum to inhibit CaxPO4 precipitation in patients on long-term dialysis (n=17) with apparent soft-tissue calcifications, and in those on short-term dialysis (n=8) without evidence of calcifications and cardiovascular disease.

FINDINGS

AHSG concentrations in serum were significantly lower in patients on haemodialysis (mean 0.66 g/L [SD 0.28]) than in healthy controls (0.72 [0.19]). Low concentrations of the glycoprotein were associated with raised amounts of CRP and with enhanced cardiovascular (p=0.031) and all-cause mortality (p=0.0013). Sera from patients on long-term dialysis with low AHSG concentrations showed impaired ex-vivo capacity to inhibit CaxPO4 precipitation (mean IC50: 9.0 microL serum [SD 3.1] vs 7.5 [0.8] in short-term patients and 6.4 [2.6] in controls). Reconstitution of sera with purified AHSG returned this impairment to normal. Interpretation AHSG deficiency is associated with inflammation and links vascular calcification to mortality in patients on dialysis. Activated acute-phase response and AHSG deficiency might account for accelerated atherosclerosis in uraemia.