Heremans-Schmid Glycoprotein Research Articles

Alpha-2 Heremans Schmid Glycoprotein (AHSG) promotes the proliferation of bladder cancer cells by regulating the TGF-β signalling pathway

ABSTRACT Bladder cancer (BC) is one of the most common urinary tract malignancies and is the tenth most common cancer globally. Alpha-2 Heremans Schmid Glycoprotein (AHSG) is a multifunctional protein that plays different roles in the progression of multiple tumors. However, the role and mechanism of AHSG in the development and progression of BC are unknown. AHSG expression was assessed in BC cells and tissues using western blot and immunohistochemistry. Using plasmid and siRNA, overexpressed and knocked down AHSG in BC cells were constructed. A series of functional experiments, including CCK8, plate clone formation, and flow cytometry, were performed to evaluate cell proliferation and cycle. AHSG was expressed higher in BC cells and tissues than in normal bladder epithelial cells and non-tumor tissues. Functionally, the overexpression of AHSG significantly increased the proliferation of BC cells and promoted the cell cycle from G1 to the S phase, whereas the knockdown of AHSG gave the opposite result.Additionally, western blot results revealed that AHSG expression level was negatively correlated with the phosphorylation level of Smad2/3 protein, a key downstream molecule of the traditional TGF-β signaling pathway, suggesting that AHSG could antagonize the traditional TGF-β signaling pathway. Finally, the expression level of AHSG in the urine of BC patients was significantly higher than that of healthy subjects by ELISA, with specificity. Our study concluded that AHSG might be a novel marker of BC that promotes the proliferation of BC cells by regulating the TGF-β signaling pathway.

Effects of two different eight-week walking programs on insulin resistance and ER stressrelated markers in pre-menopausal women / Premenopozal kadınlarda 8 haftalık farklı şiddetteki yürüyüş antrenmanlarının insülin direnci ve ER stresiyle ilişkili markerler üzerine etkileri

Abstract Objective: The relationship between exercise and endoplasmic reticulum (ER) stress, insulin resistance, and obesity is a new field of research. To our knowledge, there are no studies examining the effects of walking exercises on ER stress related markers and insulin resistance in pre-menopausal women. To examine the effect of two different eight-week walking programs on the tumor necrosis factor-alpha (TNF-α), Fetuin-A (α2 - Heremans Schmid glycoprotein), c-Jun N-terminal kinase-1 (JNK-1) and retinol- binding protein-4 (RBP-4), the related markers of ER stress and insulin resistance in pre-menopausal women. Methods: Exercise groups (moderate tempo walking group; MTWG; n=11; brisk walking group BWG; n=12) walked five days a week, starting from 30 minutes, gradually increasing up to 51 minutes. BWG walked at ~70-75% and MTWG at ~50-55 of HRRmax. Body mass index (BMI), body fat percentage (%), VO2max, serum TNF-α, Fetuin-A, JNK-1, RPB-4, blood lipids, and insulin resistance levels were determined before and after the intervention. Results: VO2max increased in both exercise groups favoring BWG; RBP-4 decreased in both exercise groups (p<0.05). Serum TNF-α and, TG (p<0.05), BMI and percent body fat (p<0.01), and insulin levels reduced significantly in BWG (p<0.05). The reductions observed in both exercise groups in insulin resistance, and the increases determined in the negative levels of JNK-1 in BWG may be clinically important. Conclusion: Both type of walking resulted in similar positive effects on RBP-4. The reduction observed in TNF-α, RBP-4, and the increases in the negative levels of JNK-1 in BWG show the positive effects of brisk walking on ER stress. The reduction in insulin resistance in relation to the possible reductions in ER stress and apoptosis in BWG may be more effective to prevent metabolic diseases.

Fetuin A Concentration in the Amniotic Fluid of Fetuses with Down Syndrome

Fetuin A Concentration in the Amniotic Fluid of Fetuses with Down Syndrome Background: Fetuin-A is a plasma protein called Alfa 2- Heremans Schmid glycoprotein. During the fetal life, it is the major component of non-collagenous bone matrix. The aim of this study was to examine the probable variation of Fetuin A which is produced by the fetal liver and trophoblastic tissue and found in abundance in the amniotic fluid Methods: Twenty cases in which amniocentesis were performed were included in the study between December 2012 and December 2013. Amniotic fluid samples were collected from women who underwent amniocentesis in the second trimester of pregnancy. Conventional cytogenetic culture was performed and ten fetuses with Down Syndrome (DS) were identified. They were classified as Group 1 and ten fetuses with normal karyotype were classified as Group 2. Levels of FetuinA in the amniotic fluid were measured in each group. Results: Age, gender, gestational age, obstetrics history and body mass index of the cases in Group 1 and Group 2 were similar. Mean amnion fluid Fetuin-A levels in Group 1 was 3.5 ± 0.4 ng/mL and these values were detected to be 4.7 ± 0.7 ng/mL in Group 2. There was statistically significant difference between the mean amniotic fluid Fetuin-A levels of two groups. (P=0.001 from the Mann-Whitney U test). Conclusion: In the present study, amnion fluid Fetuin-A levels were found to be significantly lower in the presence of DS. Decreased Fetuin-A levels may be effective on antenatal and postnatal developments of fetuses with DS. By the clarification of its importance treatment modalities may be developed.

Alpha-2 Heremans Schmid Glycoprotein (AHSG) Modulates Signaling Pathways in Head and Neck Squamous Cell Carcinoma Cell Line SQ20B

This study was performed to identify the potential role of Alpha-2 Heremans Schmid Glycoprotein (AHSG) in Head and Neck Squamous Cell Carcinoma (HNSCC) tumorigenesis using an HNSCC cell line model. HNSCC cell lines are unique among cancer cell lines, in that they produce endogenous AHSG and do not rely, solely, on AHSG derived from serum. To produce our model, we performed a stable transfection to down-regulate AHSG in the HNSCC cell line SQ20B, resulting in three SQ20B sublines, AH50 with 50% AHSG production, AH20 with 20% AHSG production and EV which is the empty vector control expressing wild-type levels of AHSG. Utilizing these sublines, we examined the effect of AHSG depletion on cellular adhesion, proliferation, migration and invasion in a serum-free environment. We demonstrated that sublines EV and AH50 adhered to plastic and laminin significantly faster than the AH20 cell line, supporting the previously reported role of exogenous AHSG in cell adhesion. As for proliferative potential, EV had the greatest amount of proliferation with AH50 proliferation significantly diminished. AH20 cells did not proliferate at all. Depletion of AHSG also diminished cellular migration and invasion. TGF-β was examined to determine whether levels of the TGF-β binding AHSG influenced the effect of TGF-β on cell signaling and proliferation. Whereas higher levels of AHSG blunted TGF-β influenced SMAD and ERK signaling, it did not clearly affect proliferation, suggesting that AHSG influences on adhesion, proliferation, invasion and migration are primarily due to its role in adhesion and cell spreading. The previously reported role of AHSG in potentiating metastasis via protecting MMP-9 from autolysis was also supported in this cell line based model system of endogenous AHSG production in HNSCC. Together, these data show that endogenously produced AHSG in an HNSCC cell line, promotes in vitro cellular properties identified as having a role in tumorigenesis.

Abstract 3788: Alpha-2 Heremans Schmid glycoprotein (AHSG) promotes migration in head and neck squamous cell carcinoma (HNSCC) cell lines.

Abstract Head and neck squamous cell carcinoma (HNSCC) is the eighth most common tumor in the world. Approximately 30,000 new cases of HNSCC are reported each year and 8,000 related deaths, in the United States. HNSCC of the oral cavity is highly metastatic and has a recurrence rate of 20%-50%, with a dismal 5-year survival rate of ∼50%. African-American males have a 5-year survival rate of ∼42% while the survival rate for Caucasian males is 52%. To date, there is no consistent means for early detection or a reliable biomarker for HNSCC, thus perpetuating the lack of improvement in mortality despite advances in delivery of treatment and surgical reconstruction. In a proteomic study seeking possible biomarkers for HNSCC, AHSG was detected at elevated levels in serum. Interestingly, we have found that some HNSCC cell lines synthesize and secrete AHSG. We have also shown in earlier studies, that the lack of AHSG reduces mammary tumor incidence and prolongs tumor latency in a mouse model for breast cancer. Together, this suggests that this hepatocellular glycoprotein that is found in most body fluids including serum could be a potential biomarker for HNSCC. AHSG is a negative acute phase response protein, which makes the findings of elevated levels of AHSG in the proteomic study most intriguing. In order to evaluate the role of AHSG in HNSCC progression (proliferation and metastatic properties) in vitro, we depleted AHSG in the HNSCC cell lineSQ20B. Thus far, we show that depletion of AHSG does not affect the proliferation of SQ20B cells. However, the depletion of AHSG mediates a decrease in migration and invasion of SQ20B cells. We are currently elucidating the molecular mechanisms of AHSG-mediated motility. This work was supported by grants from the NIH-NCI-Score 1 SC1 CA134018-01 (JO); DOD W81XWH-07-1-0254 (J.O); 5 T32 HL007735-15 (SA) and U54 CA091408 (subproject, DM). Citation Format: Pamela D. Thompson, Kurt Watson, Amos Sakwe, Josiah Ochieng, Dana Marshall. Alpha-2 Heremans Schmid glycoprotein (AHSG) promotes migration in head and neck squamous cell carcinoma (HNSCC) cell lines. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3788. doi:10.1158/1538-7445.AM2013-3788

Abstract LB-15: Alpha-2 Heremans Schmid glycoprotein (AHSG) promotes growth in head and neck squamous cell carcinoma

Abstract Head and neck squamous cell carcinoma (HNSCC) is the eighth most common tumor in the world. In the United States, approximately 30,000 new cases of HNSCC are reported each year and 8,000 related deaths. HNSCC of the oral cavity is highly metastatic and has a recurrence rate of 20%-50%, with a dismal 5-year survival rate of ∼50%. There continues to be no consistent means for early detection or a reliable biomarker for the disease. This has contributed to the lack of improvement in the mortality rates of the disease, despite advances in delivery of treatment and surgical reconstruction. In a proteomic study seeking possible biomarkers for HNSCC, AHSG was detected at elevated serum levels. AHSG is a cell surface glycoprotein that is known to be synthesized by hepatocytes and found in most body fluids including serum. AHSG is also a negative acute phase function protein, which makes the results from the proteomic study, elevated levels of AHSG, intriguing. Our lab has recently shown that the lack of AHSG reduces tumor incidence and prolongs tumor latency. We now show that some HNSCC cell lines synthesize and secrete AHSG at both the message and protein levels. This is important as most cells acquire AHSG through uptake from serum. To our knowledge, this is the first report of AHSG synthesis and expression in HNSCC cell lines. We are currently depleting AHSG expression in these HNSCC cell lines in order to evaluate the effects of AHSG on the growth and metastatic properties (invasiveness and motility) in vitro and in vivo. <br Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-15. doi:1538-7445.AM2012-LB-15

Proteomic analysis reveals oxidative stress response as the main adaptative physiological mechanism in cows under different production systems

Three groups of cows representing three ranges of welfare in the production system were included in the study: two groups of Bruna dels Pirineus beef cattle maintained under different management systems (good and semiferal conditions) and a group of Alberes cows, a breed that lives in the mountains (hardest conditions). In order to identify new stress/welfare biomarkers, serum from Bruna cows living in both environments was subjected to DIGE labelling, two-dimensional electrophoresis and MALDI-MS or ion trap MS. Identification was achieved for 15 proteins, which mainly belonged to three biological functions, the oxidative stress pathway (glutathione peroxidase (GPx) and paraoxonase (PON-1)), the acute phase protein family (Heremans Schmid glycoprotein alpha2 (α2-HSG)) and the complement system. Biological validation included the Alberes breed. GPx and PON-1 were validated by an enzymatic assay and found to be higher and lower, respectively, in cows living in hard conditions. α2-HSG was validated by ELISA and found to be reduced in hard conditions. Other biomarkers of the redox status were also altered by living conditions: protein carbonyl content, superoxide dismutase (SOD) and glutathione reductase (GR). Our results show that changes in the redox system are the main adaptation of cows living in challenging environmental conditions.

AHSG Tag Single Nucleotide Polymorphisms Associate With Type 2 Diabetes and Dyslipidemia

OBJECTIVE—The gene encoding the α2 Heremans-Schmid glycoprotein (AHSG) is a credible biological and positional candidate gene for type 2 diabetes and the metabolic syndrome, and previous attempts to relate AHSG variation with type 2 diabetes and obesity in Swedish and French Caucasians have been largely successful. We related seven frequent AHSG tag single nucleotide polymorphisms to a range of metabolic traits, including type 2 diabetes, obesity, and dyslipidemia. RESEARCH DESIGN AND METHODS—The polymorphisms were genotyped in 7,683 white Danish subjects using Taqman allelic discrimination or chip-based matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, providing a statistical power of >99% to replicate previous findings. Data were analyzed in case-control and haplotype settings, and quantitative metabolic traits were examined for association. Moreover, epistatic effects between AHSG variants and insulin receptor substrate-1 (IRS1) and β-2-adrenergic receptor polymorphisms were investigated. RESULTS—The −469T>G (rs2077119) and IVS6+98C>T (rs2518136) polymorphisms were associated with type 2 diabetes (P = 0.007 and P = 0.006, respectively, or Pcorr = 0.04 and Pcorr = 0.03, respectively, following correction for multiple hypothesis testing), and in a combined analysis of the present and a previous study −469T>G remained significant (odds ratio 0.90 [95% CI 0.84–0.97]; P = 0.007). Furthermore, two AHSG haplotypes were associated with dyslipidemia (P = 0.003 and Pcorr = 0.009). Thr248Met (rs4917) tended to associate with lower fasting and post–oral glucose tolerance test serum insulin release (P = 0.02, Pcorr = 0.1 for fasting and P = 0.04, Pcorr = 0.2 for area under the insulin curve) and improved insulin sensitivity estimated by the homeostasis model assessment of insulin resistance (9.0 vs. 8.6 mmol · l−1 · pmol−1 · l−1; P = 0.01, Pcorr = 0.06). Indications of epistatic effects of AHSG variants with the IRS1 Gly971Arg polymorphism were observed for fasting serum triglyceride concentrations. CONCLUSIONS—Based on present and previous findings, common variation in AHSG may contribute to the interindividual variation in metabolic traits.

Gene Polymorphisms and Serum Alpha-2-Heremans-Schmid Levels in Italian Haemodialysis Patients

Background: Vascular calcification (VC) and accelerated atherosclerosis are major causes of cardiovascular (CV) morbidity and mortality in haemodialysis (HD) patients. Inhibitory proteins are associated with reduced VC and may play a key role in preventing CV in chronic kidney disease (CKD) patients. Fetuin-A, also known as α₂-Heremans-Schmid glycoprotein (AHSG), is a circulating plasma protein with inhibitory effects on VC that has been associated with inflammation and CV mortality in HD patients. In the present study, we investigated the associations between serum fetuin-A levels and its gene (AHSG) polymorphisms in an Italian HD population. Methods: Ninety-six patients on stable chronic HD treatment and 57 healthy controls were genotyped for the common polymorphisms on the AHSG (T256S). In addition, serum fetuin-A levels were tested. Results: In this study, serum fetuin-A levels were lower in HD patients (0.35 ± 0.11 g/l) compared with healthy controls (0.62 ± 0.31 g/l, p < 0.05). In both HD patients and the control group, the distribution of the AHSG gene did not show significant association between low serum fetuin-A levels and the Ser/Ser genotype, known to be associated with a higher CV mortality risk in the HD population. Moreover, the distribution of AHSG gene polymorphisms in HD patients and in healthy controls was similar. Conclusions: In contrast with previous reports, this study suggests that CKD patients on HD treatment have a similar polymorphism distribution of the AHSG gene compared with the normal population and that the reduction in serum fetuin-A levels in Italian HD patients is not associated with an alteration in the distribution of AHSG T256S polymorphisms.

Suppressive effect of alpha2 Heremans-Schmid glycoprotein on in vitro calcification of osteogenesis

alpha(2) Heremans-Schmid glycoprotein (alpha(2)HS glycoprotein) is predominantly found in bone. To date, we have investigated plasma alpha(2)HS levels in immature babies and neonates as well as the histological distribution in various neonatal tissues in order to clarify its physiological significance. In an effort to understand the physiological function of alpha(2)HS glycoprotein in bones, we studied the effects of alpha(2)HS glycoprotein in cultured osteogenesis model using rat marrow cells. We added different concentrations of alpha(2)HS glycoprotein to cultured marrow cells, including osteoblasts in the presence of dexamethasone, in an attempt to elucidate the effects of alpha(2)HS glycoprotein on osteoblast growth and bone calcification in vitro. The results showed that total DNA content was significantly increased with 0.2-20 nM (f.c.) alpha(2)HS glycoprotein, but was neither suppressed nor increased with 200 nM (f.c.) alpha(2)HS glycoprotein. Although ALP activity increased with 0.2 or 2 nM (f.c.) alpha(2)HS glycoprotein, it decreased with 20 or 200 nM (f.c.) alpha(2)HS glycoprotein. While 0.2 nM (f.c.) alpha(2)HS glycoprotein had no effect on calcium or osteocalcin content, 2 nM (f.c.) alpha(2)HS glycoprotein decreased both calcium content and osteocalcin content by about half, and no calcium or osteocalcin was observed with 20 or 200 nM (f.c.). Calcium staining of cultured marrow cells revealed that the number of stained cell tubercles decreased in a concentration-dependent manner. These findings suggest that alpha(2)HS glycoprotein regulates the growth of osteoblasts and acts as an inhibitory factor in the regulation of bone calcification.

Polymorphism of the AHSG gene is associated with increased adipocyte β2-adrenoceptor function

The alpha(2) Heremans-Schmid glycoprotein (AHSG) gene is implicated in the regulation of body fat and insulin sensitivity. The Met/Met genotype of the common single-nucleotide polymorphism (SNP), rs4917, in the AHSG gene has been shown to be associated with reduced plasma levels as well as lower body fat. Here, we studied the association of this variation with subcutaneous adipocyte lipolysis. Ninety-three obese and nonobese healthy men were genotyped for Thr230Met, and subcutaneous adipose tissue biopsies were analyzed for lipolysis characteristics. The Met/Met genotype was associated with a marked increase of 1.5 log units in the lipolytic sensitivity to the beta2-adrenoceptor agonist terbutaline (P=0.0008) as compared with the Thr/Thr and Thr/Met genotypes. This corresponds to an approximately 35-fold increase in beta2-adrenoceptor function. The genotype effect was independent of body mass index and waist circumference. In contrast, lipolytic sensitivity to both the beta1-adrenoceptor agonist dobutamine (P=0.25) and the alpha2A-adrenoceptor agonist clonidine (P=0.54) was unaffected by the Thr230Met variation. Moreover, no difference in either maximal stimulation or inhibition of lipolysis was found between genotypes. We conclude that a common variation (Thr230Met) in the AHSG gene is associated with a marked increase in beta2-adrenoceptor sensitivity in subcutaneous fat cells, which may be of importance in body weight regulation.

Myocardial Stiffness, Cardiac Remodeling, and Diastolic Dysfunction in Calcification-Prone Fetuin-A–Deficient Mice

Accelerated atherosclerosis in dialysis patients is characterized by severe vascular calcification, and the magnitude of vascular calcification is associated with increased cardiovascular mortality. Calcification-dependent arterial stiffness is considered to be a major determinant of cardiac failure in uremia. Fetuin-A/alpha(2)-Heremans-Schmid glycoprotein is an abundant serum protein with powerful calcification inhibitory properties. Fetuin-A deficiency was recently linked to cardiovascular mortality in dialysis patients. Fetuin-A knockout (fetuin-KO) mice spontaneously develop widespread soft tissue calcification, including significant myocardial calcification, whereas larger arteries are spared. Therefore, this investigation offers the unique opportunity to study the functional role of isolated myocardial calcification independent of arterial stiffness by assessing the hemodynamics of fetuin-KO mice. Cardiac output in fetuin-KO mice was lower than in wild-type mice (fetuin-KO 1.81 +/- 0.18 versus WT 2.45 +/- 0.29 ml/min per g; P < 0.005), and fetuin-KO mice were refractory to dobutamine stimulation. Left ventricular relaxation was significantly impaired in fetuin-KO hearts with the relaxation index reduced by 23% (P < 0.005). After ischemia, fetuin-KO hearts displayed a continuous decline in left ventricular developed pressure after the initial phase of reperfusion, resulting in 77 +/- 15% of preischemic left ventricular developed pressure (P < 0.05 versus wild-type). In fetuin-KO mice, dystrophic cardiac calcification, with myocardial calcium contents increased 60-fold, was associated with profound induction of profibrotic TGF-beta and downstream collagen and fibronectin mRNA synthesis. In conclusion, independent of arterial stiffness, calcification-associated "myocardial stiffness" characterized by cardiac fibrosis, diastolic dysfunction, impaired tolerance to ischemia, and catecholamine resistance thus may constitute an underestimated cardiovascular risk factor that contributes to cardiac failure in calcification-prone states.

AHSG gene variant is associated with leanness among Swedish men

Alpha(2) Heremans-Schmid glycoprotein (AHSG) is a plasma protein inhibiting the activity of the insulin receptor tyrosine kinase. Ahsg knock-out mice have increased insulin sensitivity and are resistant to diet-induced obesity. We hypothesized that functional variants of the AHSG gene segregating in the human population would reflect variation in body mass index (BMI). We genotyped 356 overweight or obese (BMI: 37.2 [25.0-66.5] kg/m(2)) and 148 lean (BMI: 23.7 [23.4-24.9] kg/m(2)) otherwise healthy Swedish men for three non-synonymous single-nucleotide polymorphisms (SNPs) within exon 6 (rs4917) and exon 7 (rs4918 and Arg299Cys) and one SNP in intron 1 (rs2593813) of the AHSG gene. The G/G genotype for rs2593813 was more common among lean than among obese and overweight individuals (odds ratio = 2.01, P = 0.009), whereas rs2593813 was in strong linkage disequilibrium (|D'| > or = 0.97) with rs4917 and rs4918. Homozygosity for the rs2593813:G-rs4917:Met-rs4918:Ser haplotype conferred an increased risk for leanness (odds ratio=1.90, P = 0.027). rs4917:Met and rs4918:Ser have previously been associated with lower AHSG protein level. A common variant of AHSG, previously associated with a lower AHSG protein level, is thus more common among lean than obese and overweight men, supporting the results from Ahsg knock-out mice, namely, that AHSG modulates body mass.

?2-Heremans?Schmid glycoprotein gene polymorphisms are associated with adipocyte insulin action

The aim of this study was to investigate the effect of single-nucleotide polymorphisms (SNPs) in the gene encoding the human alpha(2)-Heremans-Schmid glycoprotein (AHSG) on obesity and insulin action in adipocytes. We screened 24 individuals for SNPs in AHSG. Six haplotype-tagging SNPs were genotyped in 188 lean and 176 obese otherwise healthy women for whom common blood chemistry phenotypes were also available. Adipocyte lipolysis and lipogenesis phenotypes were quantified in a subset of 117 lean and 174 obese women. The -469T>G SNP, which is located in the 5' region of AHSG, was associated with insulin-mediated inhibition of lipolysis and stimulation of lipogenesis, as well as basal and 8-bromocyclic AMP-stimulated lipolysis. Three AHSG SNPs were associated with circulating levels of cholesterol. None of the six genotyped SNPs or inferred haplotypes were associated with BMI, calculated percent body fat, waist circumference, circulating levels of glucose or insulin, or homeostasis model assessment of insulin resistance, which was used as an estimate of in vivo insulin sensitivity. Our results are in agreement with a threshold model of susceptibility for insulin resistance and type 2 diabetes, in which specific genetic loci regulate intermediate molecular phenotypes. When an individual's set of susceptibility alleles at such loci exceeds a threshold, clinical disease occurs. Lipolysis in adipocytes appears to be a phenotype that is particularly sensitive to variation in AHSG.

Vascular calcification in patients with end-stage renal disease.

Vascular calcification is the most common type of extra-osseous calcification in end-stage renal disease (ESRD), manifesting as both medial and intimal calcification of large arteries. It is highly prevalent, often progressive and is associated with reduced arterial elasticity and increased mortality. Risk factors for calcification in ESRD include age, duration of dialysis, diabetes mellitus, most probably an elevated calcium-phosphorus product (Ca x P) level, the dose of calcium-containing phosphate binders and the induction of the systemic inflammatory response. Uraemic calcification was thought to be a largely physico-chemical process facilitated by elevated Ca x P (i.e. "metastatic" calcification). It is now well established, however, that vascular smooth muscle cells actively take up phosphate to form bioapatite. This process is associated with a phenotypic transformation of vascular smooth muscle cells during which they express osteoblast markers. In addition to phosphate, various other factors are likely to increase bioapatite formation, e.g. lipids and inflammatory cytokines. There have also been relatively new insights relating to the role of endogenous inhibitors of calcification [i.e. matrix Gla protein and fetuin-A (alpha(2)-Heremans-Schmid glycoprotein)], in particular the downregulation of fetuin-A in systemic inflammation. Decreased serum fetuin-A has been shown to be associated with a reduced capacity to inhibit calcium phosphate precipitation in vitro and is predictive of mortality in dialysis patients. These new insights into pathogenesis may lead to better prevention and treatment of calcification (e.g. with calcimimetics, anti-cytokines, etc.). However, the only preventive approach to have been established prospectively to date is the replacement of calcium-containing phosphate binders with sevelamer HCl, a non-calcaemic phosphate binder. Yet, it remains unclear whether sevelamer HCl reduces vascular calcification by preventing episodes of hypercalcaemia and/or by reducing low-density lipoprotein (LDL)-cholesterol levels.

The serum protein α2–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 α2–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.

Elevated Levels of alpha-2-Heremans-Schmid Glycoprotein in CSF of Patients with Low-Grade Gliomas

Little is known about the expression of mitogens and other tumour-related substances in the cerebrospinal fluid (CSF) of glioma patients. The aim of the current study was to determine the presence of aberrant proteins in the CSF of patients with low-grade gliomas. Lumbar puncture was performed in 8 adult patients with supratentorial low-grade gliomas at the time of diagnosis and in 7 controls. Two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionisation time of flight mass spectrometry were used to detect and quantify deviant proteins in the CSF. Two isoforms of α₂-Heremans-Schmid glycoprotein (AHSG) were identified and demonstrated in higher levels in patients with low-grade gliomas compared with the control group consisting of patients with mixed neurological diagnoses (p = 0.001 and p = 0.04, respectively). In 1 patient, the level of AHSG was significantly reduced after gross total resection of the tumour. AHSG appears in the present proteome screening as a novel substance in glioma research. This glycoprotein is expressed in the fetal human brain and is believed to be involved in the embryonic development of the neocortex. Further analyses are planned to determine the significance of the increased levels of AHSG in the CSF of patients with low-grade gliomas.

Alpha2-Heremans Schmid glycoprotein, a putative inhibitor of tyrosine kinase, prevents glucose toxicity associated with cardiomyocyte dysfunction.

Diabetes leads to impaired glucose metabolism and insulin signaling in the heart, which may contribute to the development of diabetic cardiomyopathy. Insulin stimulates tyrosine phosphorylation of the insulin receptor and insulin receptor substrates. A two-fold increase in insulin-stimulated tyrosine phosphorylation has been reported in diabetic myocardium. The aim of the present study was to examine the effect of a putative inhibitor of tyrosine kinase phosphorylation, alpha(2)-Heremans Schmid glycoprotein (AHSG), on the mechanical dysfunction under a simulated diabetic environment. Isolated ventricular myocytes from adult rats were maintained for 24 h in either normal glucose (NG, 5.5 mM) or high glucose (HG, 25.5 mM) medium with 10(-7) M insulin, and in the absence or presence of AHSG (50 micro g/ml). Contractile indices analyzed included: peak shortening (PS), time-to-PS (TPS), time-to-90% relengthening (TR(90)) and area underneath shortening and relengthening (Area/PS). Myocytes maintained in HG medium displayed reduced PS and prolonged TPS/TR(90), with enhanced area, compared to the NG myocytes. Interestingly, these HG-induced mechanical dysfunctions were abolished by AHSG. Removal of insulin from the culture medium did not affect the basal myocyte mechanics, but prevented AHSG from completely protecting against the HG-induced mechanical defects (i.e. HG-induced prolongation of TR(90) and area were only partially attenuated by AHSG in the absence of insulin). The present data support the notion of tyrosine phosphorylation in the pathogenesis of diabetic cardiomyopathy, and implicate the therapeutic value of tyrosine kinase phosphorylation inhibitors.

Novel Insights into Uremic Vascular Calcification: Role of Matrix Gla Protein and Alpha-2-Heremans Schmid Glycoprotein/Fetuin

Cardiovascular mortality is markedly increased in the dialysis population when compared to non-uremic subjects. Vascular and valvular calcifications are most frequently found in dialysis patients at risk and are independent predictors of cardiovascular death in this population. Traditionally, the presence of hyperphosphatemia and an increased calcium × phosphate product was considered a major pathomechanistic condition leading to excessive vascular and soft-tissue calcifications in uremic subjects. Recent studies in knockout mice, however, revealed that deficiencies in calcium-regulatory proteins may also directly contribute to the development of extraosseus calcifications. α₂-Heremans Schmid glycoprotein and matrix Gla protein are important inhibitors of calcification in vivo and there is novel evidence available that a deficiency in such proteins is involved in the pathogenesis of cardiovascular calcifications in dialysis patients.