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The contribution of glucagon to type 1 and type 2 diabetes has long been known, but the underlying defects in alpha cell function are not well‐described. During both disease states, alpha cells respond inappropriately to stimuli, leading to dysregulated glucagon secretion, impaired glucose tolerance and hypoglycaemia. The mechanisms involved in this dysfunction are complex, but possibly include changes in alpha cell glucose‐sensing, alpha cell de‐differentiation, paracrine feedback, as well as alpha cell mass. However, the molecular underpinnings of alpha cell failure are still poorly understood. Recent transcriptomic analyses have identified vitamin D binding protein (DBP), encoded by GC/Gc, as an alpha cell signature gene. DBP is highly localized to the liver and alpha cells and is virtually absent from other tissues and cell types under non‐pathological conditions. While the vitamin D transportation role of DBP is well characterized in the liver and circulation, its function in alpha cells remains more enigmatic. Recent work reveals that loss of DBP leads to smaller and hyperplastic alpha cells, which secrete less glucagon in response to low glucose concentration, despite vitamin D sufficiency. Alpha cells lacking DBP display impaired Ca2+ fluxes and Na+ conductance, as well as changes in glucagon granule distribution. Underlying these defects is an increase in the ratio of cytoskeletal F‐actin to G‐actin, highlighting a novel intracellular actin scavenging role for DBP in islets. [ABSTRACT FROM AUTHOR]

Vitamin D Binding Protein (VDBP), also well-known as Gc-globulin, is a plasma protein which acts as a carrier molecule for vitamin D and its metabolites. This multifunctional glycoprotein is a member of the albumin superfamily of binding proteins. It is predominantly synthesized as a single long chain glycoprotein in the liver. VDBP helps in vitamin D metabolites transport, control bone development, binds actin monomers and fatty acids and prevents their polymerization; which might be harmful in circulatory system. A less defined role in modulating immune and inflammatory response is also known. VDBP plays an important role in protection of microcirculation, inflammation, infection and also known to have antiviral and antitumoral activity. Recent studies documented its use as a early marker for diagnosis of chronic kidney disease. This review discusses the multifunctional characters of VDBP in spectra of diseases with emphasis on its use as marker for diabetic nephropathy. [ABSTRACT FROM AUTHOR]

Summary: Vitamin-D-binding protein (DBP) or group-specific component of serum (GC-globulin) carries vitamin D metabolites from the circulation to target tissues. DBP is highly localized to the liver and pancreatic α cells. Although DBP serum levels, gene polymorphisms, and autoantigens have all been associated with diabetes risk, the underlying mechanisms remain unknown. Here, we show that DBP regulates α cell morphology, α cell function, and glucagon secretion. Deletion of DBP leads to smaller and hyperplastic α cells, altered Na+ channel conductance, impaired α cell activation by low glucose, and reduced rates of glucagon secretion both in vivo and in vitro. Mechanistically, this involves reversible changes in islet microfilament abundance and density, as well as changes in glucagon granule distribution. Defects are also seen in β cell and δ cell function. Immunostaining of human pancreata reveals generalized loss of DBP expression as a feature of late-onset and long-standing, but not early-onset, type 1 diabetes. Thus, DBP regulates α cell phenotype, with implications for diabetes pathogenesis.

Background: Changes in Gc‐globulin (Gc) and in alpha‐foetoprotein (AFP) have been shown to be related to outcome in patients with acute liver failure (ALF). Gc is a serum protein that complexes with intravascular actin released during cellular necrosis. AFP, also made by hepatocytes, is associated with hepatocellular growth and regeneration. Previously, low absolute levels or decreases over time in either AFP or Gc portended to be a poor outcome. Methods: In a retrospective analysis of the double‐blind trial of intravenous N‐acetylcysteine (NAC) for ALF not because of acetaminophen, sera on days 1 and 3 or days 2 and 4 following admission were available to measure AFP in 70 patients and Gc in 66 patients. Mann‐Whitney U tests were performed on the admission values, the absolute change and the fractional change of AFP and Gc to compare TFS (transplant‐free survival) and non‐TFS (death or transplantation). Logistic regression and receiver operating characteristic (ROC) analyses were performed to evaluate the markers in comparison and in addition to King's College Criteria (KCC). Results: Transplant‐free survival patients were characterized by increases in AFP, whereas non‐TFS had significantly different (negative) absolute and fractional changes (P < .01). The addition of declining AFP levels to KCC improved the area under the curve in predicting non‐TFS (AUC >70%). Gc globulin values did not differ between TFS and non‐TFS in the 2‐day intervals studied (P> .2). Conclusion: In this comparison of two prognostic markers in patients with non‐acetaminophen‐induced ALF, rising AFP but not rising Gc levels was associated with TFS. Trial Registration: ClinicalTrials.gov number NCT00004467. [ABSTRACT FROM AUTHOR]

Introduction and aim: Vitamin D has been associated with chronic liver diseases and low vitamin levels may contribute to progression of chronic hepatitis C. The aim of this study was to evaluate the influence of vitamin D serum levels and GC gene polymorphisms in the severity of liver fibrosis in patients with chronic hepatitis C genotype 1. Material and methods: Cross-sectional study that enrolled 132 adult patients with chronic hepatitis C genotype 1 attended at the outpatient Clinic of Gastroenterology Division at Hospital de Clínicas de Porto Alegre. At the time of enrollment patients had a blood withdraw for serum 25(OH)D determination and genotypic analysis of rs7041 and rs4588 polymorphisms in GC gene. None/mild fibrosis was considered as METAVIR F0, F1 and F2 and severe fibrosis as METAVIR F3 and F4. Results: Median 25(OH)D levels in the sample were 19.9 ng/mL (P25-P75: 14.0-29.4). Fifty percent of patients presented vitamin D deficiency (< 20 ng/mL). In stepwise multiple linear regression the variables associated with 25(OH)D levels were blood withdrawn in Winter/spring season, the haplotypes AT/AT + AG/AT of rs7041 and rs4588 and female sex. For evaluation of severe fibrosis, variables associated in logistic regression were age, vitamin D severe deficiency (< 10 ng/mL), glucose levels, BMI and platelets count. Conclusions: Vitamin D levels are associated with severity of liver fibrosis in chronic hepatitis C genotype 1 patients. Although the rs7041 and rs4588 GC polymorphisms are strong predictors of vitamin D levels, they do not play a direct role in liver fibrosis.

This study aimed to analyse vitamin D-binding protein (Gc-globulin) serum levels in acute liver failure (ALF) in children in relation to disease outcomes and correlations with other known markers used to evaluate the severity of ALF. Our study included 34 children (mean age 4.87 ± 5.30 years) with ALF of different causes (metabolic, 26.47%; autoimmune, 23.53%; toxic, 20.59%; infection, 17.65%; unknown, 11.76%) and 30 children without any liver injury (mean age 6.11 ± 4.26 years). The outcome was poor in 14 patients (41.18%), including one child with liver transplantation (2.94%). Serum Gc-globulin levels were significantly lower in ALF patients compared to the control group (151.57 ± 171.8 mg/L vs. 498.63 ± 252.50 mg/L; p < 0.000001), with an optimum cut-off of 163.5 mg/L (Area Under the Curve, AUC, 0.8921; sensitivity, 76.50%; specificity, 100%). Levels were also lower in patients with poor outcomes compared to survivors (59.34 ± 33.73 mg/L vs. 216.12 ± 199.69 mg/L; p < 0.0001), with an optimum cut-off 115 mg/L (AUC, 0.7642; sensitivity, 100%; specificity, 50%). Gc-globulin serum levels were variable according to ALF aetiology, i.e., lower in metabolic, infectious, or unknown causes compared to autoimmune and toxic causes. Gc-globulin serum levels were decreased in children with ALF and lower in those with poor outcomes compared with survivors. Gc-globulin serum levels were correlated with other known parameters used to evaluate the severity of ALF and could help to identify patients at high risk for poor outcomes.

The teleological purpose of an ongoing pregnancy is to fulfill its fundamental role of a successful, uncomplicated delivery, in conjunction with an optimal intrauterine environment for the developing fetus. Vitamin D metabolism is adapted to meet both these demands during pregnancy; first by stimulation of calcium absorption for adequate intrauterine bone mineral accrual of the fetus, and second, by enhancing systemic and local maternal tolerance to paternal and fetal alloantigens. Vitamin D-binding protein (VDBP) is one of the key biomolecules that optimize vitamin D homeostasis and also contributes as an immune regulator for a healthy, ongoing pregnancy. In this regard, recent results indicate that dysregulation of VDBP equilibrium could be a risk factor for adverse fetal, maternal, and neonatal outcomes, including preeclampsia, preterm birth, and gestational diabetes. Moreover, it has been hypothesized to be also implicated in the interpretation of vitamin D status in the pregnant state. The aim of this review is to assess available literature regarding the association of VDBP with clinical outcomes during pregnancy, as a potential biomarker for future clinical practice, with a discourse on current knowledge gaps and future research agenda.

The measurement of vitamin D-binding protein (VDBP) by immunoassay has been confounded by variable antibody recognition of the Gc1s, Gc1F and Gc2 phenotypes. This has led to spurious conclusions regarding vitamin D status in different ethnic groups. In order to overcome these problems there is a requirement for VDBP antibodies that are unaffected by phenotype status. Here we report the generation and testing of three monoclonal antibodies to VDBP which recognise linear epitopes and are unaffected by vast molar excesses of synthetic peptides spanning these phenotypic domains. These IgG1 kappa antibodies were purified and biotinylated to allow suitable pairings to develop a sandwich ELISA for circulating VDBP. The VDBP ELISA is unaffected by actin and confirms that VDBP levels are significantly reduced in sepsis patients and non-sepsis intensive care patients compared to normal healthy subjects. Levels of VDBP along with total 25OH vitamin D3 can be used to calculate free 25OH vitamin D3 levels and these compare well with consensus values determined independently. The VDBP ELISA meets acceptable performance criteria and as such can be used in conjunction with total 25OH vitamin D3 to determine the free 25OH vitamin D3 status in various cohorts. [ABSTRACT FROM AUTHOR]

Background. The extracellular actin scavenging system (EASS) is composed of plasma Gc-globulin and gelsolin, and is responsible for the elimination of toxic actin from the bloodstream. Objectives. In this study, we assessed the actin-free Gc-globulin concentrations in blood plasma and cerebrospinal fluid (CSF) obtained from subjects with neurodegenerative and inflammatory diseases of the central nervous system (CNS) as well as in a control group. Material and methods. Using an enzyme-linked immunosorbent assay (ELISA), we measured the actinfree Gc-globulin concentrations in blood plasma and CSF obtained from subjects diagnosed with Alzheimer's disease (AD) (n = 20), amyotrophic lateral sclerosis (ALS) (n = 12), multiple sclerosis (MS) (n = 42), tick-borne encephalitis (TBE) (n = 12), and from a control group (n = 20). Results. The concentrations of free Gc-globulin in plasma collected from patients diagnosed with AD (509.6 ±87.6 mg/L) and ALS (455.5 ±99.8 mg/L) did not differ significantly between each other, but were significantly higher compared to the reference group (311.7 ±87.5 mg/L) (p < 0.001 and p < 0.006, respectively) as well as to MS (310.8 ±66.6 mg/L) (p < 0.001 and p < 0.001, respectively) and TBE (256.7 ±76 mg/L) (p < 0.001 and p < 0.003, respectively). In CSF collected from patients diagnosed with AD and ALS, the concentrations of free Gc-globulin were 2.6 ±1.1 mg/L and 2.7 ±1.9 mg/L, respectively. They did not differ significantly between each other and were significantly higher compared to the reference group (1.5 ±0.9 mg/L) (p < 0.005 and p < 0.041, respectively). Interestingly, in patients with AD, significantly higher values of Gc-globulin were detected compared to MS patients (1.7 ±0.9 mg/L) (p < 0.013). Conclusions. Higher concentrations of free Gc-globulin in blood plasma and CSF collected from patients suffering from neurodegenerative diseases may indicate a potential role of this protein in their pathogenesis, and represent a potential tool for the diagnosis of CNS diseases. [ABSTRACT FROM AUTHOR]

The teleological purpose of an ongoing pregnancy is to fulfill its fundamental role of a successful, uncomplicated delivery, in conjunction with an optimal intrauterine environment for the developing fetus. Vitamin D metabolism is adapted to meet both these demands during pregnancy; first by stimulation of calcium absorption for adequate intrauterine bone mineral accrual of the fetus, and second, by enhancing systemic and local maternal tolerance to paternal and fetal alloantigens. Vitamin D-binding protein (VDBP) is one of the key biomolecules that optimize vitamin D homeostasis and also contributes as an immune regulator for a healthy, ongoing pregnancy. In this regard, recent results indicate that dysregulation of VDBP equilibrium could be a risk factor for adverse fetal, maternal, and neonatal outcomes, including preeclampsia, preterm birth, and gestational diabetes. Moreover, it has been hypothesized to be also implicated in the interpretation of vitamin D status in the pregnant state. The aim of this review is to assess available literature regarding the association of VDBP with clinical outcomes during pregnancy, as a potential biomarker for future clinical practice, with a discourse on current knowledge gaps and future research agenda. [ABSTRACT FROM AUTHOR]

Introduction and aim. Vitamin D has been associated with chronic liver diseases and low vitamin levels may contribute to progression of chronic hepatitis C. The aim of this study was to evaluate the influence of vitamin D serum levels and GC gene polymorphisms in the severity of liver fibrosis in patients with chronic hepatitis C genotype 1. Material and methods. Cross-sectional study that enrolled 132 adult patients with chronic hepatitis C genotype 1 attended at the outpatient Clinic of Gastroenterology Division at Hospital de Clínicas de Porto Alegre. At the time of enrollment patients had a blood withdraw for serum 25(OH)D determination and genotypic analysis of rs7041 and rs4588 polymorphisms in GC gene. None/mild fibrosis was considered as METAVIR F0, F1 and F2 and severe fibrosis as METAVIR F3 and F4. Results. Median 25(OH)D levels in the sample were 19.9 ng/mL (P25- P75: 14.0-29.4). Fifty percent of patients presented vitamin D deficiency (< 20 ng/mL). In stepwise multiple linear regression the variables associated with 25(OH)D levels were blood withdrawn in Winter/spring season, the haplotypes AT/AT + AG/AT of rs7041 and rs4588 and female sex. For evaluation of severe fibrosis, variables associated in logistic regression were age, vitamin D severe deficiency (< 10 ng/mL), glucose levels, BMI and platelets count. Conclusions. Vitamin D levels are associated with severity of liver fibrosis in chronic hepatitis C genotype 1 patients. Although the rs7041 and rs4588 GC polymorphisms are strong predictors of vitamin D levels, they do not play a direct role in liver fibrosis. [ABSTRACT FROM AUTHOR]

This review considers the functions of extracellular actin-cell surface bound, associated with extracellular matrix, or freely circulating. The role of this protein in different pathological processes is analyzed: its toxic effects and involvement in autoimmune diseases as an autoantigen. The extracellular actin clearance system and its role in protection against the negative effects of actin are characterized. Levels of free-circulating actin, anti-actin immunoglobulins, and components of the actin clearance system as prognostic biomarkers for different diseases are reviewed. Experimental approaches to protection against excessive amounts of free-circulating F-actin are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Improving the early detection rate and surveillance of bladder cancer remains a great challenge in medicine. Here, we identified sixteen proteins including Gc-globulin (GC) in urine from bladder cancer patients and normal controls by two-dimensional fluorescent differential gel electrophoresis (2D-DIGE) and matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF/TOF MS). Bioinformatics analyses indicated GC played important roles in the regulation of growth, apoptosis, death and epidermal growth factor receptor activity. The GC expression patterns in urine or tissue from cases and controls were further quantified by western blotting, immunohistochemical staining and enzyme-linked immunosorbent assay (ELISA). ELISA quantification by correcting for creatinine expression showed GC-Cr was significantly increased in bladder cancer patients than in benign bladder damages cases and normal controls (1013.70±851.25 versus 99.34±55.87, 105.32±47.81ng/mg, respectively). Receiver operating characteristic (ROC) analysis suggested that at 161.086ng/mg urinary GC, bladder cancer could be detected with 92.31% sensitivity and 83.02% specificity, and 1407.481ng/mg with 82.61% sensitivity and 88.24% specificity could be used for the detection of infiltrating urothelial carcinoma of bladder cancer. Taken together, we identified GC as a potential novel urinary biomarker for the early detection and surveillance of bladder cancer. [Copyright &y& Elsevier]

The serum vitamin D binding protein (DBP), also known as GC-globulin, is a multifunctional protein known for its role in the transport of vitamin D metabolites. DBP also binds fatty acids and actin monomers, preventing their polymerization that could be detrimental in the circulatory system. DBP may have immune functions independent of its role as a transporter of vitamin D. Because of the abundance of DBP, many aspects of its basic biochemistry were quickly established. Other features of vitamin D action, particularly transcriptional mechanisms of regulation, received greater focus and early interest in DBP centred on its value as a tool for population genetics because of its intriguing genetic variations. Nonetheless, knowledge of DBP mechanisms in physiology was obtained, and functions beyond vitamin D ligand binding were identified. With the recent increased attention regarding the benefits of vitamin D (bone health and immunological regulation), there has been a resurgence of interest in DBP. Because DBP is the primary transporter of vitamin D, it has a role in maintaining the total levels of vitamin D for the organism and in regulating the amounts of free (unbound) vitamin D available for specific tissues and cell types to utilize. This review will describe the findings on the basic biochemistry and molecular biology of DBP, the studies that elucidated its biological functions and highlight these results in light of the current renewed interest in vitamin D and human health, as well as the debate over what constitutes sufficient levels of vitamin D. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Background: Gc-globulin is a polymorphic protein with three phenotypes: Gc 1-1, Gc 2-1 and Gc 2-2. Deglycosylation of Gc-globulin results in a Gc-macrophage activating factor (Gc-MAF). This study investigated the potential of MAF as a tumour marker and the influence of Gcphenotypes on serum MAF-concentrations. Methods: Gc-phenotype of 98 healthy individuals and 60 cancer patients was determined. MAF-levels of healthy individuals and cancer patients were analysed according to their Gc-phenotype using a Helix pomatia agglutinin-based ELISA. ROC curves analysed the efficiency of MAF as a tumour marker. Results: MAF-levels between controls and patients were significantly different (p<0.001). No phenotypic differences were found in the patients. In comparison with the controls, MAF-values were significantly lower in cancer patients carrying Gc 1-1 (p<0.01) and Gc 2-1 (p<0.001). No difference was observed in Gc 2-2 phenotype. Diagnostic accuracy of MAF as a tumour marker also demonstrated pronounced differences between Gc-phenotypes. Conclusions: Gc-phenotype is a confounding factor when interpreting MAF-data. The value of MAF as a tumour marker varies according to phenotype. Future studies on MAF will have to consider the effect of Gc-phenotype. [ABSTRACT FROM AUTHOR]

Abstract: The vitamin D binding protein (DBP) is a multifunctional, albumin-like plasma protein that often requires cell surface binding to mediate some of its diverse functions. DBP binds to several different molecules on the external face of the plasma membrane indicating that it may possess distinct cell binding sequences. In this report, surface plasmon resonance was utilized to evaluate the relative binding of the human myeloid cell line U937 to immobilized recombinant expressed DBP in order to identify cell localization sequences. U937 cells showed robust binding to immobilized native DBP, but essentially no interaction when sensor chips were coated with β2-microglobulin or BSA. The cell–DBP interaction was completely eliminated if cells were pretreated with soluble DBP. Recombinant DBP domains and truncated domains were next evaluated to determine the location of cell binding regions. Domains I (amino acids 1–191) and III (379–458), but not domain II (192–378), could support cell binding. Further evaluation of domain I, using truncated proteins and overlapping peptides, demonstrated that a single amino acid sequence, residues 150–172 (NYGQAPLSLLVSYTKSYLSMVGS), mediated cell binding. The domain III cell binding region was investigated using truncated versions of domain III fused to full-length domain II that served as a scaffold. These experiments indicated that the cell binding sequence is located in the first portion of that domain (379–402: ELSSFIDKGQELCADYSENTFTEY). Overlapping peptides spanning this sequence could partially block cell binding only when used in combination. We conclude that DBP contains two cell localization sequences that may be required for some of the multiple functions of this protein. [Copyright &y& Elsevier]

Abstract: Background: Gc-globulin or vitamin D binding protein is a highly expressed, multifunctional and polymorphic serum protein, which also serves as the major transporter for vitamin D metabolites in the circulation. The present study was performed to analyze the interaction between gc-globulin of hepatocytes and hepatic stellate cells, the most important fat-/retinol-storing cell type in the liver, which spontaneously transdifferentiates to myofibroblasts in culture. Methods: Hepatic stellate cells and hepatocytes were isolated by the pronase/collagenase reperfusion method, hepatocytes by collagenase reperfusion of the organ. Gc-globulin expression was monitored by immunocytochemistry, immunoblotting, RT-PCR, metabolic labelling with [35S]-methionine, and its intracellular binding to α-smooth-muscle actin was investigated by co-immunoprecipitation. Cytoskeletal stainings of gc-globulin and α-smooth-muscle actin in hepatic stellate cells and the identification of the receptors megalin/gp330, HCAM/CD44, cubilin and annexin A2 were performed with confocal immunocytochemistry, immunoblotting and/or FACS-analysis. Results: Hepatocytes synthesize and secrete gc-globulin as shown by RT-PCR and [35S]-methionine labelling, which could be suppressed by cycloheximide. Also, a strong signal for gc-globulin was detected in the immunoblot of native hepatic stellate cell lysates. However, no mRNA for gc-globulin was found in this cell type, which suggests no active synthesis by hepatic stellate cells. Hepatic stellate cells were tested positively for the presence of known gc-globulin interacting receptors megalin/gp330, HCAM/CD44, cubilin and annexin A2. Inhibition of the megalin/gp330 receptor by a competitive, neutralizing antibody resulted in decreased intracellular availability of gc-globulin in hepatic stellate cells. The latter effect was enhanced by additional incubation of hepatic stellate cells with EDTA for complexing Ca2+, suggesting a Ca2+-dependent internalization of gc-globulin into hepatic stellate cells via the megalin/gp300 receptor. This was supported by confocal microscopy which showed a co-localization of gc-globulin with the multifunctional megalin/gp330 receptor on this cell type. Inside hepatic stellate cells, a linkage between gc-globulin and α-smooth muscle actin filaments of hepatic stellate cells was detected by immunocytochemistry. Intracellular binding of gc-globulin to α-smooth-muscle actin filaments was confirmed by co-immunoprecipitation. Conclusion: We give evidence to the expression of the megalin/gp330 receptor on hepatic stellate cells and that this receptor is involved in the Ca2+-dependent internalization of gc-globulin into hepatic stellate cells, a protein synthesized and secreted into the extracellular space and circulation by hepatocytes. Inside hepatic stellate cells, it co-localizes with and binds to α-smooth muscle actin filaments. Under consideration of the available literature, these findings propose a participation of gc-globulin in hepatic vitamin D metabolism as well as in hepatic stellate cell stability and apoptosis as important mechanisms of liver regeneration. [Copyright &y& Elsevier]

Abstract: The vitamin D binding protein (DBP) is the major plasma carrier protein of vitamin D and its metabolites. Unlike other hydrophobic hormone-binding systems, it circulates in a considerably higher titer compared to its ligands. Apart from its specific sterol binding capacity, DBP exerts several other important biological functions such as actin scavenging, fatty acid transport, macrophage activation and chemotaxis. The DBP-gene is a member of a multigene cluster that includes albumin, α-fetoprotein, and α-albumin/afamin. All four genes are expressed predominantly in the liver with overlapping developmental profiles. DBP is a highly polymorphic serum protein with three common alleles (Gc1F, Gc1S and Gc2) and more than 120 rare variants. The presence of unique alleles is a useful tool for anthropological studies to discriminate and to reveal ancestral links between populations. Many studies have discussed the link between DBP-phenotypes and susceptibility or resistance to osteoporosis, Graves'' disease, Hashimoto''s thyroiditis, diabetes, COPD, AIDS, multiple sclerosis, sarcoidosis and rheumatic fever. This article reviews the general characteristics, functions and clinical aspects of DBP. [Copyright &y& Elsevier]

Background: A low serum level ([sub <]100 mg/L) of the actin-scavenger Gc-globulin is a prognostic marker of non-survival in fulminant hepatic failure (FHF). It is unknown whether decreased production or increased consumption (or both) is responsible for the low Gc-globulin levels. Methods: Ten patients with FHF and four patients with acute or chronic liver disease (AOCLD) with hepatic encephalopathy (HE) grades II-IV were included. Eight patients with cirrhosis (chronic liver disease, CLD) without HE served as controls. Total, free, and actin-bound Gc-globulin were measured in samples from an artery, a central vein, and a hepatic vein. In 12 patients (9 FHF, 3 AOCLD), concentrations were measured before and after high volume plasmapheresis (HVP). Results: Total Gc-globulin was reduced to 21%, 40%, and 43% of the normal level in the FHF, AOCLD, and CLD groups, respectively, whereas bound Gc-globulin was within normal range in all patients. The Gc:actin complex ratio was increased 3.8, 2.5, and 1.9-fold compared with normal levels. Total, free, and bound serum Gc-globulin levels did not differ among arterial, systemic venous, or hepatic venous blood. Total Gc-globulin rose to >100 mg/L in all patients after HVP, whereas bound Gc-globulin remained unchanged. The Gc-globulin production rate in FHF and AOCLD patients was increased to 4.1 ± 1.3 mg/min compared to literature values of 0.6 mg/min in healthy individuals. The estimated half-life of total Gc-globulin was shorter in the patients compared to healthy individuals (127 ± 56 min and 870 min, respectively). Conclusions: Gc-globulin levels were reduced in patients with FHF and AOCLD because a 7-fold increase of Gc-globulin production rate could not compensate for the accelerated clearance. Bound Gc-globulin was maintained within normal levels in all circumstances studied, indicating a possible regulatory role of this parameter in the clearance of actin. [ABSTRACT FROM AUTHOR]

Objective: Actin is the dominating intracellular protein and is released to the circulation after tissue injury. Gc-globulin is one of the plasma proteins responsible for removal of actin from the circulation. Recent studies have shown that the level of Gc-globulin is reduced shortly after trauma. Serial changes in Gc-globulin after severe injury have not been studied so far and could provide additional information about the role of Gc-globulin in the pathophysiological response to trauma. Design: Prospective, observational. Setting: Surgical intensive care unit in a university hospital. Patients: Thirty-eight patients were included in the study: 12 women and 26 men with a median age of 38 years (range 19–86) and a median Injury Severity Score (ISS) of 18 (range 6–45). Seven patients died, on day 5, 8, 8, 10, 10, 13 and 21, respectively. Interventions: None. Measurements and main results: The serum concentration of Gc-globulin (Gctotal) and the percentage of Gc-globulin bound to actin (Gc%complexed) were measured daily for 1 week using rocket immunoelectrophoresis. Concentrations of free Gc-globulin (Gcfree) and Gc-globulin bound to actin (Gcbound) were calculated from these analytical results. The concentration of Gctotal and Gccomplexed correlated significantly (r=–0.99, p<0.001) throughout the time period. After day 3 levels of Gc%complexed normalised, whereas levels of Gctotal continued to increase above control values. The concentrations of Gctotal and Gcfree were significantly lower in non-survivors compared to survivors; p=0.005 and p=0.03, respectively. This was combined with an inverse correlation of Gcbound between these two groups (r=–0.73; p=0.04). Conclusions: Severe injury results in a prolonged load on the extracellular actin scavenger system; more pronounced in patients who do not survive. Gc-globulin displays characteristics of an acute phase reactant, with supra-normal serum levels 1 week after severe injury. Serial measurements of Gc-globulin after trauma could prove to be a method of early identification of patients with increased risk of mortality. [ABSTRACT FROM AUTHOR]

1,25-dihydroxyvitamin D (1,25(OH) D) has been shown to modulate lymphocyte activation in vitro. Through binding to specific receptors 1,25(OH) D inhibits proliferation, immunoglobulin production and the release of cytokines. Moreover, 1,25-(OH) D is efficiently produced by activated monocytes. These findings suggest that 1,25-(OH) D may play a role as a regulator of immunological activation. Consequently, we found it of interest to study the serum levels of the two major metabolites of vitamin D in patients with systemic lupus erythematosus (SLE) (n=21), rheumatoid arthritis (RA) (n=29) and osteoarthritis (n=12). In patients with SLE the levels of 25-OH D were below those of the healthy controls (p=0.0008) and OA (p=0.0168). The levels 1,25-(OH) D corresponded to normal levels. There were no significant correlations between 25-OH D levels and clinical or paraclinical disease manifestations. Further, the phenotypic distribution of Gc-globulin, which binds vitamin D metabolites in circulation, was normal. The serum concentrations of 1,25-(OH) D and 25-OH D in patients with RA and OA corresponded to those of the controls. Although the cause of the reduced 25-OH D levels in SLE patients is unclear, possible beneficial effects of administration of vitamin D to these patients should be considered. [ABSTRACT FROM AUTHOR]

This study aimed to analyse vitamin D-binding protein (Gc-globulin) serum levels in acute liver failure (ALF) in children in relation to disease outcomes and correlations with other known markers used to evaluate the severity of ALF. Our study included 34 children (mean age 4.87 ± 5.30 years) with ALF of different causes (metabolic, 26.47%; autoimmune, 23.53%; toxic, 20.59%; infection, 17.65%; unknown, 11.76%) and 30 children without any liver injury (mean age 6.11 ± 4.26 years). The outcome was poor in 14 patients (41.18%), including one child with liver transplantation (2.94%). Serum Gc-globulin levels were significantly lower in ALF patients compared to the control group (151.57 ± 171.8 mg/L vs. 498.63 ± 252.50 mg/L; p < 0.000001), with an optimum cut-off of 163.5 mg/L (Area Under the Curve, AUC, 0.8921; sensitivity, 76.50%; specificity, 100%). Levels were also lower in patients with poor outcomes compared to survivors (59.34 ± 33.73 mg/L vs. 216.12 ± 199.69 mg/L; p < 0.0001), with an optimum cut-off 115 mg/L (AUC, 0.7642; sensitivity, 100%; specificity, 50%). Gc-globulin serum levels were variable according to ALF aetiology, i.e., lower in metabolic, infectious, or unknown causes compared to autoimmune and toxic causes. Gc-globulin serum levels were decreased in children with ALF and lower in those with poor outcomes compared with survivors. Gc-globulin serum levels were correlated with other known parameters used to evaluate the severity of ALF and could help to identify patients at high risk for poor outcomes. [ABSTRACT FROM AUTHOR]

Vitamin-D-binding protein (DBP) or group-specific component of serum (GC-globulin) carries vitamin D metabolites from the circulation to target tissues. DBP is highly localized to the liver and pancreatic α cells. Although DBP serum levels, gene polymorphisms, and autoantigens have all been associated with diabetes risk, the underlying mechanisms remain unknown. Here, we show that DBP regulates α cell morphology, α cell function, and glucagon secretion. Deletion of DBP leads to smaller and hyperplastic α cells, altered Na + channel conductance, impaired α cell activation by low glucose, and reduced rates of glucagon secretion both in vivo and in vitro. Mechanistically, this involves reversible changes in islet microfilament abundance and density, as well as changes in glucagon granule distribution. Defects are also seen in β cell and δ cell function. Immunostaining of human pancreata reveals generalized loss of DBP expression as a feature of late-onset and long-standing, but not early-onset, type 1 diabetes. Thus, DBP regulates α cell phenotype, with implications for diabetes pathogenesis., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)

Vitamin D plays a vital role in successful pregnancy outcomes for both the mother and fetus. Vitamin D is bound to vitamin D binding protein (VDBP) in blood and is carried to the liver, kidneys and other target tissues. Accurate measurements of the clinically measured metabolite of vitamin D, 25-hydroxyvitamin D [25(OH)D], depend on complete removal from the binding protein. It has been found that VDBP concentrations increase in maternal serum during pregnancy, obfuscating the accuracy of 25(OH)D concentration measurements in pregnant women. Additionally, measurements of VDBP concentrations during pregnancy have been performed using immunoassays, which suffer from variations due to differences in antibody epitopes, making clinical comparisons difficult. Quantification of VDBP is also of interest because changes in VDBP expression levels may indicate negative outcomes during pregnancy, such as preterm delivery and restricted fetal growth. To address the need for accurate measurement of VDBP during pregnancy, a method using liquid chromatography-isotope dilution mass spectrometry (LC-IDMS) was developed to quantify VDBP using isotopically labeled peptides as internal standards. This method was used to quantify VDBP in Standard Reference Material® (SRM) 1949 Frozen Human Prenatal Serum, which was prepared from separate serum pools of women who were not pregnant and women during each trimester of pregnancy. VDBP concentrations were found to be lowest in the serum pool from non-pregnant women and increased in each trimester. These data had good repeatability and were found to be suitable for reference value assignment of VDBP in SRM 1949., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Aim: To investigate the relationship of vitamin D-binding protein (GC) and genetic variation of GC (rs4588, rs7041 and rs2282679) with metabolic syndrome (MetS) in the Thai population., Materials & Methods: GC-globulin concentrations were measured by quantitative western blot analysis in 401 adults. All participants were genotyped using TaqMan allelic discrimination assays., Results: GC-globulin levels were significatly lower in MetS subjects than in control subjects, in which significant negative correlations of GC-globulin levels with systolic blood pressure, glucose and age were found. Male participants who carried the GT genotype for rs4588 showed an increased risk of MetS compared with the GG wild-type (odds ratio: 3.25; p = 0.004)., Conclusion: GC-globulin concentrations and variation in GC rs4588 were supported as a risk factor for MetS in Thais.

Vitamin-D-binding protein (VDBP), a transporter of 25-hydroxyvitamin D metabolites, has three common isoforms. The relationship of the isoforms and their glycosylation state with various diseases has been under recent examination. In this work, liquid chromatography coupled to isotope dilution mass spectrometry was evaluated for quantification of VDBP, the three common isoforms, and total glycosylation. Protocols using guanidine, urea, RapiGest, trifluoroethanol, or tris buffer were also evaluated for optimal tryptic digestion. Differences in peptide release were detected between purified and plasma VDBP; however, for both protein sources, ELPEHTVK, TSALSAK, and VLEPTLK concentrations were reproducible between most protocols tested. The isoform-specific peptides, LPDATPK, LPDATPTELAK, and LPEATPTELAK, were optimally released when TFE was added to plasma. The total VDBP concentration calculated from the three shared peptides resulted in 97.6% accuracy compared with the concentration from amino acid analysis. Glycosylation of VDBP was also calculated for purified protein and donor samples using the ratio of the isoform-specific peptide(s) to the total protein concentration. Glycosylation of purified VDBP was found to be 99.5-111.1% the value determined by semiquantitative analysis of the intact protein by LC-MS. This approach may be used to quantify other samples containing a mixture of isoforms and post-translational modifications.