Gc-globulin is an acute phase reactant and an indicator of muscle injury after spinal surgery

Changes in Skeletal Muscle Troponin T and Vitamin D Binding Protein (DBP) Concentrations in the Blood of Male Amateur Athletes Participating in a Marathon and 100 km Adventure Race

This study assessed changes in creatine kinase (CK) activity and skeletal muscle troponin T (sTnT) concentrations in the blood, to estimate the degree of muscle degradation after exercise. In addition, the concentration of vitamin D binding protein (DBP) in the blood was assessed. DBP concentrations were measured in blood as a marker for plasma load by monomeric actin. The study included marathon (MR) participants and 100 km adventure race (AR) participants, who were examined before and after the race. There was a significant (16-fold) increase in CK activity among AR participants, and a significant increase in sTnT concentration-127% in the MR group and 113% in the AR group, while there was a statistically significant decrease in DBP concentration by 14% in the AR group. In addition, it was observed that the initial concentration of DBP in both groups was in a normal range, but was lower than the average population, and the DBP concentration in the AR group was lower than in the MR group. It was concluded that exhausting physical effort such as a marathon or adventure races causes muscle damage with a far stronger influence on sarcoplasm than on filaments. The short-term and slight reduction in the concentration of DBP in blood after such efforts may be due to the appearance of monomeric actin in plasma.

Development and analytical validation of a novel bioavailable 25-hydroxyvitamin D assay

BACKGROUND

Bioavailable 25-hydroxyvitamin D (25OHD) may be a better indicator of vitamin D sufficiency than total 25OHD. This report describes a novel assay for measuring serum bioavailable 25OHD.

METHODS

We developed an assay for 25OHD % bioavailability based on competitive binding of 25OHD tracer between vitamin D-binding protein (DBP)-coated affinity chromatography beads and serum DBP. Bioavailable 25OHD, total 25OHD, albumin, and DBP protein concentrations were measured in 89 samples from hospitalized patients and 42 healthy controls to determine how the DBP binding assay responds to differences in concentrations of DBP and compares to calculated bioavailable 25OHD values.

RESULTS

DBP binding assay showed a linear relationship between DBP-bound 25OHD tracer recovered from bead supernatant and DBP calibrator concentrations (y = 0.0017x +0.731, R2 = 0.9961, p<0.001). Inversion of this relationship allowed interpolation of DBP binding equivalents based upon 25OHD tracer recovered. The relationship between DBP binding equivalents and % bioavailability fits a non-linear curve, allowing calculation of % bioavailable 25OHD from DBP binding equivalents (y = 10.625x-0.817, R2 = 0.9961, p<0.001). In hospitalized patient samples, there were linear relationships between DBP protein concentrations and DBP binding equivalents (y = 0.7905x + 59.82, R2 = 0.8597, p<0.001), between measured vs. calculated % bioavailability (y = 0.9528 + 0.0357, R2 = 0.7200, p<0.001), and between absolute concentrations of measured vs. calculated bioavailable 25OHD (y = 1.2403 + 0.1221, R2 = 0.8913, p<0.001).

CONCLUSIONS

The DBP-binding assay for bioavailable 25OHD shows expected changes in 25OHD % bioavailability in response to changes in DBP concentrations and concordance with calculated bioavailable 25OHD concentrations.

Length of stay, readmission, and mortality after primary surgery for pediatric spinal deformities: a 10-year nationwide cohort study

BACKGROUND CONTEXT

Extended length of stay (extLOS) and unplanned readmissions after first time pediatric spinal deformity surgery are a considerable challenge to both the patient and the health-care system. To our knowledge, only a limited number of nationwide studies reporting short-term comorbidity with complete follow-up exist.

PURPOSE

The purpose of this study was to identify the postoperative complications leading to extLOS, readmissions, and mortality within 90 days after surgery. Furthermore, to identify risk factors for readmission.

DESIGN

Retrospective national cohort study.

PATIENT SAMPLE

A nationwide registry study including all pediatric spinal deformity patients (≤21 years of age) undergoing primary surgery during 2006-2015 (n=1,310).

OUTCOME MEASURES

Reasons for extLOS and 90-day readmissions as well as mortality risk.

METHODS

Patients were identified by procedure and diagnosis codes in the Danish National Patient Registry (DNPR). Data on length of stay (LOS), readmissions, and mortality within 90 days were retrieved from the DNPR. Patients were categorized in six groups according to etiology. Reasons for extLOS and readmission were collected from medical records and discharge summaries.

RESULTS

For the 1,310 patients, the median LOS was 8 days (interquartile range 7-9). Etiologies were idiopathic deformity (53%), neuromuscular deformity (23%), congenital/structural deformity (9%), spondylolisthesis (7%), Scheuermann kyphosis (5%), and syndromic deformity (3%). A total of 274 (21%) patients had extLOS and the most common reason was pain/mobilization issues but with considerable variation between etiologies; Scheuermann kyphosis (91%), idiopathic (59%), syndromic (44%), spondylolisthesis (38%), and congenital (30%). Pulmonary complications were the primary reason for extLOS in the neuromuscular group (22%). The 90-day readmission rate was 6%; 67% of readmissions were medical, mainly infections unrelated to the surgical site (23%); 33% of readmissions were surgical and 14% of patients required revision surgery. Neuromuscular deformity, spondylolisthesis, Scheuermann kyphosis, and LOS >9 days were independent risk factors for readmission; odds ratio (OR) 4.4 (95% confidence interval: 2.2-9.1, p<.01), OR 3.0 (1.1-8.0, p=.03), OR 4.9 (1.7-13.6, p<.01), and OR 1.8 (1.0-3.1, p=.04), respectively. The 90-day mortality risk was 0.4%.

CONCLUSIONS

In this nationwide cohort, pain/mobilization issues are the most common reason for extLOS. The most common reason for readmission is infection unrelated to the surgical site. Readmission after pediatric spinal surgery is related to the etiology and increased focus on patients operated for neuromuscular deformity, spondylolisthesis and Scheuermann kyphosis is warranted.

Evaluation of Vitamin D Metabolism in Patients with Type 1 Diabetes Mellitus in the Setting of Cholecalciferol Treatment

In this prospective controlled study, we examined 25 adults with adequately controlled (HbA1c level < 8.0%) type 1 diabetes mellitus (T1DM) and 49 conditionally healthy adults, intending to reveal the diversity of vitamin D metabolism in the setting of cholecalciferol intake at a therapeutic dose. All patients received a single dose (150,000 IU) of cholecalciferol aqueous solution orally. Laboratory assessments including serum vitamin D metabolites (25(OH)D₃, 25(OH)D₂, 1,25(OH)₂D₃, 3-epi-25(OH)D₃ and 24,25(OH)₂D₃), free 25(OH)D, vitamin D-binding protein (DBP) and parathyroid hormone (PTH) as well as serum and urine biochemical parameters were performed before the intake and on Days 1, 3 and 7 after the administration. The studied groups had no significant differences in baseline parameters except that the patients with diabetes showed higher baseline levels of free 25(OH)D (p < 0.05). They also lacked a correlation between the measured and calculated free 25(OH)D in contrast to the patients from the control group (r = 0.41, p > 0.05 vs. r = 0.88, p < 0.05), possibly due to the glycosylation of binding proteins, which affects the affinity constant for 25(OH)D. The elevation of vitamin D levels after the administration of cholecalciferol was comparable in both groups, with slightly higher 25(OH)D₃ levels observed in the diabetes group throughout the study since Day 1 (p < 0.05). Overall, our data indicate that in patients with adequately controlled T1DM 25(OH)D₃ levels and the therapeutic response to cholecalciferol is similar to that in healthy individuals.

Vitamin D-binding protein as a biomarker to confirm specific clinical diagnoses

Introduction: Vitamin D-binding protein (DBP) performs a variety of functions as a transporter for various ligands and takes part in a number of systemic and local physiological and pathological processes. The knowledge about the pathomechanisms of this protein involvement justifies its use as a biomarker to confirm specific clinical diagnoses suggested by nonspecific signs and symptoms.Areas covered: DBP has properties of both systemic laboratory parameters measured in the blood plasma and specific parameters measured in variety of physiological fluids to assess local changes in specific body organs. Articles published in English between 1993 and 2019 were searched for in PubMed using terms DBP, vitamin D, and metabolites, inflammation. DBP is a transport protein and a regulator of immune and inflammatory processes.Expert opinion: DBP capacity for transporting numerous ligands and co-involvement of DBP in immune and inflammatory processes suggest that DBP may be used in laboratory diagnostics as a specific parameter to confirm pathomechanisms of several systemic diseases and local conditions. Changes in the concentration of DBP present in a variety of clinical material may provide valuable information for use in assessing the severity and treatment of pathological processes.

Vitamin D Binding Protein: A Historic Overview

Vitamin D and all its metabolites are bound to a specific vitamin D binding protein, DBP. This protein was originally first discovered by its worldwide polymorphism and called Group-specific Component (GC). We now know that DBP and GC are the same protein and appeared early in the evolution of vertebrates. DBP is genetically the oldest member of the albuminoid family (including albumin, α-fetoprotein and afamin, all involved in transport of fatty acids or hormones). DBP has a single binding site for all vitamin D metabolites and has a high affinity for 25OHD and 1,25(OH)2D, thereby creating a large pool of circulating 25OHD, which prevents rapid vitamin D deficiency. DBP of higher vertebrates (not amphibians or reptiles) binds with very high affinity actin, thereby preventing the formation of polymeric actin fibrils in the circulation after tissue damage. Megalin is a cargo receptor and is together with cubilin needed to reabsorb DBP or the DBP-25OHD complex, thereby preventing the urinary loss of these proteins and 25OHD. The total concentrations of 25OHD and 1,25(OH)2D in DBP null mice or humans are extremely low but calcium and bone homeostasis remain normal. This is the strongest argument for claiming that the "free hormone hypothesis" also applies to the vitamin D hormone, 1,25(OH)2D. DBP also transports fatty acids, and can play a role in the immune system. DBP is genetically very polymorphic with three frequent alleles (DBP/GC 1f, 1s, and 2) but in total more than 120 different variants but its health consequences, if any, are not understood. A standardization of DBP assays is essential to further explore the role of DBP in physiology and diseases.

Vitamin D Binding Protein, Total and Free Vitamin D Levels in Different Physiological and Pathophysiological Conditions

This review focuses on the biologic importance of the vitamin D binding protein (DBP) with emphasis on its regulation of total and free vitamin D metabolite levels in various clinical conditions. Nearly all DBP is produced in the liver, where its regulation is influenced by estrogen, glucocorticoids and inflammatory cytokines but not by vitamin D itself. DBP is the most polymorphic protein known, and different DBP alleles can have substantial impact on its biologic functions. The three most common alleles-Gc1f, Gc1s, Gc2-differ in their affinity with the vitamin D metabolites and have been variably associated with a number of clinical conditions. Although DBP has a number of biologic functions independent of vitamin D, its major biologic function is that of regulating circulating free and total levels of vitamin D metabolites. 25 hydroxyvitamin D (25(OH)D) is the best studied form of vitamin D as it provides the best measure of vitamin D status. In a normal non-pregnant individual, approximately 0.03% of 25(OH)D is free; 85% is bound to DBP, 15% is bound to albumin. The free hormone hypothesis postulates that only free 25(OH)D can enter cells. This hypothesis is supported by the observation that mice lacking DBP, and therefore with essentially undetectable 25(OH)D levels, do not show signs of vitamin D deficiency unless put on a vitamin D deficient diet. Similar observations have recently been described in a family with a DBP mutation. This hypothesis also applies to other protein bound lipophilic hormones including glucocorticoids, sex steroids, and thyroid hormone. However, tissues expressing the megalin/cubilin complex, such as the kidney, have the capability of taking up 25(OH)D still bound to DBP, but most tissues rely on the free level. Attempts to calculate the free level using affinity constants generated in a normal individual along with measurement of DBP and total 25(OH)D have not accurately reflected directly measured free levels in a number of clinical conditions. In this review, we examine the impact of different clinical conditions as well as different DBP alleles on the relationship between total and free 25(OH)D, using only data in which the free 25(OH)D level was directly measured. The major conclusion is that a number of clinical conditions alter this relationship, raising the question whether measuring just total 25(OH)D might be misleading regarding the assessment of vitamin D status, and such assessment might be improved by measuring free 25(OH)D instead of or in addition to total 25(OH)D.

Characterization of equine vitamin D-binding protein, development of an assay, and assessment of plasma concentrations of the protein in healthy horses and horses with gastrointestinal disease

OBJECTIVE To purify and characterize equine vitamin D-binding protein (VDBP) from equine serum and to evaluate plasma concentrations of VDBP in healthy horses and horses with gastrointestinal injury or disease. ANIMALS 13 healthy laboratory animals (8 mice and 5 rabbits), 61 healthy horses, 12 horses with experimentally induced intestinal ischemia and reperfusion (IR), and 59 horses with acute gastrointestinal diseases. PROCEDURES VDBP was purified from serum of 2 healthy horses, and recombinant equine VDBP was obtained through a commercial service. Equine VDBP was characterized by mass spectrometry. Monoclonal and polyclonal antibodies were raised against equine VDBP, and a rocket immunoelectrophoresis assay for equine VDBP was established. Plasma samples from 61 healthy horses were used to establish working VDBP reference values for study purposes. Plasma VDBP concentrations were assessed at predetermined time points in horses with IR and in horses with naturally occurring gastrointestinal diseases. RESULTS The working reference range for plasma VDBP concentration in healthy horses was 531 to 1,382 mg/L. Plasma VDBP concentrations were significantly decreased after 1 hour of ischemia in horses with IR, compared with values prior to induction of ischemia, and were significantly lower in horses with naturally occurring gastrointestinal diseases with a colic duration of < 12 hours than in healthy horses. CONCLUSIONS AND CLINICAL RELEVANCE Plasma VDBP concentrations were significantly decreased in horses with acute gastrointestinal injury or disease. Further studies and the development of a clinically relevant assay are needed to establish the reliability of VDBP as a diagnostic and prognostic marker in horses.

Critically Ill Children Have Low Vitamin D-Binding Protein, Influencing Bioavailability of Vitamin D

RATIONALE

Vitamin D deficiency, often defined by total serum 25-hydroxyvitamin D (25[OH]D) <20 ng/ml, is common in critically ill patients, with associations with increased mortality and morbidity in the intensive care unit. Correction of vitamin D deficiency in critical illness has been recommended, and ongoing clinical trials are investigating the effect of repletion on patient outcome. The biologically active amount of 25(OH)D depends on the concentration and protein isoform of vitamin D-binding protein (VDBP), which is also an acute-phase reactant affected by inflammation and injury.

OBJECTIVES

We performed a secondary analysis of a cohort of critically ill children in which we reported a high rate of vitamin D deficiency, to examine how VDBP level and genotype would impact vitamin D status.

METHODS

We prospectively enrolled 511 children admitted to the pediatric intensive care unit over a 12-month period.

MEASUREMENTS AND MAIN RESULTS

We measured serum VDBP in 479 children. We genotyped single nucleotide polymorphisms rs7041 and rs4588 in the VDBP gene (GC) to determine haplotypes GC1F, GC1S, and GC2 in 178 subjects who consented, then calculated bioavailable 25(OH)D from serum 25(OH)D, VDBP, albumin, and GC haplotype. The median serum VDBP level was 159 μg/ml (interquartile range, 108-221), lower than has been reported in healthy children. Factors predicting lower levels in multivariate analysis included age <1 year, nonwhite race, being previously healthy, 25(OH)D <20 ng/ml and greater illness severity. In the subgroup that was genotyped, GC haplotype had the strongest association with VDBP level; carriage of one additional copy of GC1S was associated with a 37.5% higher level (95% confidence interval, 31.9-44.8; P < 0.001). Bioavailable 25(OH)D was also inversely associated with illness severity (r = -0.24, P < 0.001), and ratio to measured total 25(OH)D was variable and related to haplotype.

CONCLUSIONS

Physiologic deficiency of 25(OH)D in critical illness may be more difficult to diagnose, given that lower VDBP levels increase bioavailability. Treatment studies conducted on the basis of total 25(OH)D level, without consideration of VDBP concentration and genotype, may increase the risk of falsely negative results.

Behind the scenes of vitamin D binding protein: more than vitamin D binding

Although being discovered in 1959, the number of published papers in recent years reveals that vitamin D binding protein (DBP), a member of the albuminoid superfamily, is a hot research topic. Besides the three major phenotypes (DBP1F, DBP1S and DBP2), more than 120 unique variants have been described of this polymorphic protein. The presence of DBP has been demonstrated in different body fluids (serum, urine, breast milk, ascitic fluid, cerebrospinal fluid, saliva and seminal fluid) and organs (brain, heart, lungs, kidneys, placenta, spleen, testes and uterus). Although the major function is binding, solubilization and transport of vitamin D and its metabolites, the name of this glycoprotein hides numerous other important biological functions. In this review, we will focus on the analytical aspects of the determination of DBP and discuss in detail the multifunctional capacity [actin scavenging, binding of fatty acids, chemotaxis, binding of endotoxins, influence on T cell response and influence of vitamin D binding protein-macrophage activating factor (DBP-MAF) on bone metabolism and cancer] of this abundant plasma protein.

Vitamin D-Binding Protein in Health and Chronic Kidney Disease

Vitamin D-binding protein (DBP) is a multifunctional protein that has attracted increasing interest in recent years, largely because of its potential role in modulating the activity of vitamin D. Nearly all circulating vitamin D (~85-90%) circulates bound to DBP, with a smaller proportion bound to albumin, leaving <5% circulating freely. DBP may also play roles beyond vitamin D binding, with potential roles in the immune system and elsewhere. Numerous polymorphisms of DBP exist around the world, and recent studies have identified relevance of different DBP phenotypes in determining DBP concentration and vitamin D affinity. This review focuses on the known roles of DBP in health and kidney disease, and current views on the relevance of DBP polymorphisms.

Acute phase plasma proteins are altered by electroconvulsive stimulation

Electroconvulsive therapy (ECT) is an effective antidepressant treatment, but its molecular mechanisms of action remain to be fully elucidated. To better understand the effects of ECT, we conducted a proteomic study to characterize global changes in plasma protein abundance induced by electroconvulsive stimulation (ECS) in the animal model equivalent of ECT. Male Sprague-Dawley rats were administered a single or repeat (10 sessions) course of ECS, and compared with sham-ECS administered animals. Quantitative differential protein expression analysis was performed, using 2-dimensional difference in gel electrophoresis (2D DiGE), on immunodepleted plasma. Proteins were selected for identification by liquid chromatography tandem mass spectrometry (LC-MS/MS): 150 protein spots were significantly altered following a single ECS and 178, following repeated ECS. In total, 18 proteins were identified by LC-MS/MS. Many of these were acute-phase response proteins, previously reported to be increased in depressed patients. Changes in the abundance of two proteins of interest were confirmed by other measures. Repeat ECS was found to significantly reduce plasma levels of haptoglobin and apolipoprotein A-IV, although these changes were no longer evident 4 weeks after the repeated ECS. Our results implicate the immune system-induced acute phase protein response in ECS action while identifying potential plasma biomarkers for ECS.

Safety pharmacology, toxicology and pharmacokinetic assessment of human Gc globulin (vitamin D binding protein)

Gc globulin is an important protein of the plasma actin-scavenger system. As such, it has been shown to bind free actin and prevent hypercoagulation and shock in patients with massive actin release resulting from severe tissue injuries. Treatment of such patients with Gc globulin could therefore potentially be life-saving. This article presents pre-clinical toxicology experiments conducted on purified plasma-derived human Gc globulin. The Gc globulin formulation was shown to be stable for at least 4 years with full retention of actin-binding capacity. In vitro studies did not reveal activation of the kallikrein system or the complement system and cellular studies showed no toxic effects on a variety of human cell lines. In vivo studies showed no acute toxic effects in mice, rats or guinea pigs upon intravenous infusion. A 14-day local tolerance study in rabbits showed no adverse effects, and 14-day toxicity studies in rats and horses did not show any unwanted reactions. In a 14-day toxicology study in beagle dogs, formation of antibodies was seen and in the end of the study period, three out of four dogs showed clinical immunological reactions, which could be ascribed to the formation of antibodies. The half-life, T, for human Gc globulin was 12 hr in rats, 16 hr in horses and 30 hr in dogs. The safety profile of plasma-derived Gc globulin is concluded to be consistent to that required for use in man.

Actin-free Gc-globulin after minimal access and conventional anterior lumbar surgery

BACKGROUND

Minimally invasive total knee or hip replacement has been increasingly adopted in recent years. However, literature indicates that minimally invasive joint arthroplasty may not always reduce pain or tissue trauma. We hypothesized that the tissue damage would be reduced in minimal access surgery (MAS) than the conventional open surgery (OS) for anterior lumbar disorders through quantifying measurement of serum actin-free Gc-globulin (Af-Gc), myoglobin (MG), and total creatine kinase (CK).

MATERIALS AND METHODS

This prospective study enrolled 23 patients, including 10 who underwent MAS and thirteen who underwent conventional OS. Blood samples for Af-Gc, MG, and CK were taken simultaneously before surgery and then at intervals of 12, 24, 48, 72, 120, and 168 h thereafter.

RESULTS

All serum level changes in Af-Gc, MG, and CK were significantly lower in the MAS than in the OS group. A significant negative correlation was noted between changes in Af-Gc and MG levels (P = 0.012), and a significant positive correlation was noted between changes in CK and MG levels (P < 0.001). However, at 12 h postop, CK level was transiently higher in MAS group than the OS group.

CONCLUSIONS

The changes of Af-Gc, MG, and CK levels indicate that MAS is less tissue invasive than OS. Further, Af-Gc proved to be a more sensitive marker than MG or CK in response to surgical trauma. The transiently higher CK level at 12 h postop in MAS patients may indicate that a more soft tissue manipulation is required in MAS than the OS patients for the initial surgical approach.

Proteomics study of neuropathic and nonneuropathic dorsal root ganglia: altered protein regulation following segmental spinal nerve ligation injury

Peripheral nerve injury is often followed by the development of severe neuropathic pain. Nerve degeneration accompanied by inflammatory mediators is thought to play a role in generation of neuropathic pain. Neuronal cell death follows axonal degeneration, devastating a vast number of molecules in injured neurons and the neighboring cells. Because we have little understanding of the cellular and molecular mechanisms underlying neuronal cell death triggered by nerve injury, we conducted a proteomics study of rat 4th and 5th lumbar (L4 and L5) dorsal root ganglion (DRG) after L5 spinal nerve ligation. DRG proteins were displayed on two-dimensional gels and analyzed through quantitative densitometry, statistical validation of the quantitative data, and peptide mass fingerprinting for protein identification. Among approximately 1,300 protein spots detected on each gel, we discovered 67 proteins that were tightly regulated by nerve ligation. We find that the injury to primary sensory neurons turned on multiple cellular mechanisms critical for the structural and functional integrity of neurons and for the defense against oxidative damage. Our data indicate that the regulation of metabolic enzymes was carefully orchestrated to meet the altered energy requirement of the DRG cells. Our data also demonstrate that ligation of the L5 spinal nerve led to the upregulation in the L4 DRG of the proteins that are highly expressed in embryonic sensory neurons. To understand the molecular mechanisms underlying neuropathic pain, we need to comprehend such dynamic aspect of protein modulations that follow nerve injury.

Biological and clinical aspects of the vitamin D binding protein (Gc-globulin) and its polymorphism

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, alpha-fetoprotein, and alpha-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.

Plasma 25-hydroxyvitamin D does not vary over the course of a malarial infection

Assessment of the status of some micronutrients is complicated by the acute phase response to infection. We investigated whether 25-hydroxyvitamin D (25OHD) is an acute phase reactant by measuring the effect of a malarial infection on plasma 25OHD level. Blood samples were taken from patients with Plasmodium falciparum malaria daily during the course of their stay in hospital and at a follow-up session 2-6 weeks after discharge. 25OHD was measured by radioimmunoassay. Time course data for the 14 subjects who provided samples for at least the first 2 d in hospital showed no change in 25OHD level during the acute infection. For the 14 subjects with follow-up results, there was no difference between median 25OHD level at admission (25.6 ng/ml, interquartile range (IQR) 23.0, 40.2) and at follow-up (25.2 ng/ml, IQR 19.2, 32.1; P=0.084). 25OHD level appears to be unaffected during the course of a severe malarial infection and thus can be used as a measure of vitamin D status even in subjects who are currently ill.

Therapeutic potential of vitamin D-binding protein

Vitamin D-binding protein (DBP) is a multi-functional plasma protein with many important functions. These include transport of vitamin D metabolites, control of bone development, binding of fatty acids, sequestration of actin and a range of less-defined roles in modulating immune and inflammatory responses. Exploitation of the unique properties of DBP could enable the development of important therapeutic agents for the treatment of a variety of diseases.

Recombinant plasma gelsolin infusion attenuates burn-induced pulmonary microvascular dysfunction

Reduced plasma concentrations of the extracellular actin-binding proteins gelsolin and Gc-globulin correlate with pulmonary failure and death in humans after injury. The purpose of this study was to investigate the role of plasma gelsolin in the pathophysiology of inflammation-induced lung injury. We postulated that plasma gelsolin levels decrease at an early time point after burn injury and that the intravenous infusion of gelsolin prevents burn-induced pulmonary microvascular dysfunction. Adult Sprague-Dawley rats were randomized to undergo a 40% body surface area thermal injury (Burn) or manipulation without burn (Sham). Plasma gelsolin and Gc-globulin concentrations were determined at various times during the first 6 days of injury by Western blotting. Other animals were randomized to receive either recombinant human gelsolin (0.078, 0.78, or 7.8 mg) or albumin (7.8 mg) before and 8 h after Burn or Sham. Twenty-four hours later, pulmonary microvascular permeability was assessed by measuring the capillary filtration by use of an isolated, perfused lung model. We found that plasma gelsolin levels of burn-injured rats decreased to 10% of normal levels within 12 h and remained below normal levels for up to 6 days postinjury. Gc-globulin values also fall, but to a lesser extent and only transiently. Treatment of burned animals with intravenous infusions of recombinant human gelsolin prevented the increase in pulmonary microvascular permeability that accompanies this injury. Our findings are consistent with the hypothesis that plasma gelsolin depletion contributes to the pathophysiology of pulmonary microvascular dysfunction during inflammation.

Crystal structure of the complex between actin and human vitamin D-binding protein at 2.5 A resolution

A high-affinity complex formed between G-actin and plasma vitamin D-binding protein (DBP) is believed to form part of a scavenging system in the plasma for removing actin released from damaged cells. In the study presented here, we describe the crystal structure of the complex between actin and human vitamin D-binding protein at 2.5 A resolution. The complex contains one molecule of each protein bound together by extensive ionic, polar, and hydrophobic interactions. It includes an ATP and a calcium ion bound to actin, but no evidence of vitamin D metabolites bound to the DBP. Both actin and DBP are multidomain molecules, two major domains in actin and three in DBP. All of these domains contribute to the interaction between the molecules. DBP enfolds the end of the actin molecule, principally in actin subdomain 3 but with additional interactions in actin subdomain 1. This orientation is similar to the binding of profilin to actin, as predicted from previous studies. The more extensive interactions of DBP give an affinity for actin some 3 orders of magnitude higher than that for profilin. The larger "footprint" of DBP on actin also leads to an overlap with the actin-binding site of gelsolin domain I.