Human serum albumin: from bench to bedside

Serum Albumin Levels and Economic Status in Japanese Older Adults

BACKGROUND

Low serum albumin levels are associated with aging and medical conditions such as cancer, liver dysfunction, inflammation, and malnutrition and might be an independent predictor of long-term mortality in healthy older populations. We tested the hypothesis that economic status is associated with serum albumin levels and explained by nutritional and health status in Japanese older adults.

DESIGN

We performed a cross-sectional analysis using data from the Japan Gerontological Evaluation study (JAGES). The study participants were 6528 functionally independent residents (3189 men and 3339 women) aged ≥65 years living in four municipalities in Aichi prefecture. We used household income as an indicator of economic status. Multiple linear regression was used to compare serum albumin levels in relation to household income, which was classified as low, middle, and high. Additionally, mediation by nutritional and health-related factors was analyzed in multivariable models.

RESULTS

With the middle-income group as reference, participants with low incomes had a significantly lower serum albumin level, even after adjustment for sex, age, residential area, education, marital status, and household structure. The estimated mean difference was -0.17 g/L (95% confidence interval, -0.33 to -0.01 g/L). The relation between serum albumin level and low income became statistically insignificant when "body mass index", "consumption of meat or fish", "self-rated health", "presence of medical conditions", "hyperlipidemia", or "respiratory disease "was included in the model.

CONCLUSION

Serum albumin levels were lower in Japanese older adults with low economic status. The decrease in albumin levels appears to be mediated by nutrition and health-related factors with low household incomes. Future studies are needed to reveal the existence of other pathways.

Association of Hypoalbuminemia With Osteoporosis: Analysis of the National Health and Nutrition Examination Survey

CONTEXT

The association of hypoalbuminemia with osteoporosis in human studies is controversial.

OBJECTIVE

We tested the independent association between hypoalbuminemia and osteoporosis in a national dataset.

DESIGN

This is a cross-sectional observation.

SETTING AND PARTICIPANTS

Participants are individuals selected from the National Health and Nutrition Examination Survey (NHANES) with available clinical, laboratory, and densitometry data from the 2005-2010 and 2013-2014 cycles.

EXPOSURE

Exposure is hypoalbuminemia defined as serum albumin <3.5 g/dL.

MAIN OUTCOME MEASURE

Osteoporosis is defined as bone mineral density of ≤2.5 SD below the mean peak bone mass of young, healthy adults. Analysis took into account the hidden variance and the weighting methodology pertinent to analysis of NHANES.

RESULTS

Overall, 15 539 individuals were included. The mean age was 48.6 years (SE = 0.27). Fifty percent of the individuals were male, and 10.2% were of the black race. There was a graded decrease in the rate of osteoporosis from 15.2% at albumin <3.5 g/dL to 2.6% at albumin >4 g/dL (P = .007) at the femoral neck and from 11.0 to 1.4% at total femur (P = .009). In a fully adjusted model, the odds of osteoporosis with hypoalbuminemia were 5.37-fold (95% confidence interval [CI], 1.43 to 20.20; P = .014) at the femoral neck, 12.46-fold (95% CI, 3.24 to 48.01; P < .001) at total femur, and 4.59-fold (95% CI, 1.49 to 14.16; P = .025) at the lumbar spine higher as compared to albumin >4 mg/dL.

CONCLUSION

In the NHANES dataset, we report an independent association of osteoporosis with hypoalbuminemia at different anatomical sites.

Bioengineered kidney tubules efficiently excrete uremic toxins

The development of a biotechnological platform for the removal of waste products (e.g. uremic toxins), often bound to proteins in plasma, is a prerequisite to improve current treatment modalities for patients suffering from end stage renal disease (ESRD). Here, we present a newly designed bioengineered renal tubule capable of active uremic toxin secretion through the concerted action of essential renal transporters, viz. organic anion transporter-1 (OAT1), breast cancer resistance protein (BCRP) and multidrug resistance protein-4 (MRP4). Three-dimensional cell monolayer formation of human conditionally immortalized proximal tubule epithelial cells (ciPTEC) on biofunctionalized hollow fibers with maintained barrier function was demonstrated. Using a tailor made flow system, the secretory clearance of human serum albumin-bound uremic toxins, indoxyl sulfate and kynurenic acid, as well as albumin reabsorption across the renal tubule was confirmed. These functional bioengineered renal tubules are promising entities in renal replacement therapies and regenerative medicine, as well as in drug development programs.

Equilibrium Sorption of Structurally Diverse Organic Ions to Bovine Serum Albumin

Reliable partitioning data are essential for assessing the bioaccumulation potential and the toxicity of chemicals. In contrast to neutral organic chemicals, the partitioning behavior of ionogenic organic chemicals (IOCs) is still a black box for environmental scientists. Partitioning to serum albumin, the major protein in blood plasma, strongly influences the freely dissolved concentration of many chemicals (including IOCs), which affects their transport and distribution in the body. Because consistent data sets for partitioning of IOCs are rarely available, bovine serum albumin-water partition coefficients (KBSA/w) were measured in this study for 45 anionic and 4 cationic organic chemicals, including various substituted benzoic and naphthoic acids, sulfonates and several pesticides and pharmaceuticals. The results of this study suggest that binding to BSA is substantially influenced by the three-dimensional structure of the chemicals and the position of substitutions on the sorbing molecules. For example, we found a difference of >1.5 log units between isomeric chemicals such as 3,4-dichlorobenzoic acid and 2,6-dichlorobenzoic acid, and 1-naphthoic acid and 2-naphthoic acid. Conventional modeling approaches (e.g., based on octanol-water partition coefficients) poorly predict log KBSA/w of organic ions (R(2) ≤ 0.5), partially because they do not capture the observed steric effects. Hence, alternative modeling strategies will be required for accurate prediction of serum albumin-water partition coefficients of organic ions.

The Roche Immunoturbidimetric Albumin Method on Cobas c 501 Gives Higher Values Than the Abbott and Roche BCP Methods When Analyzing Patient Plasma Samples

BACKGROUND

Serum/plasma albumin is an important and widely used laboratory marker and it is important that we measure albumin correctly without bias. We had indications that the immunoturbidimetric method on Cobas c 501 and the bromocresol purple (BCP) method on Architect 16000 differed, so we decided to study these methods more closely.

METHOD

A total of 1,951 patient requests with albumin measured with both the Architect BCP and Cobas immunoturbidimetric methods were extracted from the laboratory system. A comparison with fresh plasma samples was also performed that included immunoturbidimetric and BCP methods on Cobas c 501 and analysis of the international protein calibrator ERM-DA470k/IFCC.

RESULTS

The median difference between the Abbott BCP and Roche immunoturbidimetric methods was 3.3 g/l and the Roche method overestimated ERM-DA470k/IFCC by 2.2 g/l. The Roche immunoturbidimetric method gave higher values than the Roche BCP method: y = 1.111x - 0.739, R² = 0.971.

CONCLUSION

The Roche immunoturbidimetric albumin method gives clearly higher values than the Abbott and Roche BCP methods when analyzing fresh patient samples. The differences between the two methods were similar at normal and low albumin levels.

Interaction of vitamin B1 with bovine serum albumin investigation using vitamin B1-selective electrode: potentiometric and molecular modeling study

Vitamin B1 or thiamin is one of the B vitamins. All B vitamins help the body to convert food (carbohydrates) into fuel (glucose), which produces energy. The B vitamins are necessary for healthy skin, eyes, hair, and liver. It also could help the nervous system function properly, and is necessary for brain functions. Drug interactions with protein can affect the distribution of the drug and eliminate the drug in living systems. In this study, the binding of thiamine hydrochloride (vitamin B1) to bovine serum albumin (BSA) was evaluated using a new proposed vitamin B1 (thiamine)-selective membrane electrode under various experimental conditions, such as pH, ionic strength, and protein concentration; in addition molecular modeling was applied as well. The binding isotherms plotted based on potentiometric data and analyzed using the Wyman binding potential concept. The apparent binding constant was determined and used for the calculation of intrinsic Gibbs free energy of binding. According to the electrochemical and molecular docking results, it can be concluded that the hydrophobic interactions and hydrogen binding are major interactions between BSA and vitamin B1.

Interaction of singlet oxygen with bovine serum albumin and the role of the protein nano-compartmentalization

Singlet molecular oxygen ((1)O2) contributes to protein damage triggering biophysical and biochemical changes that can be related with aging and oxidative stress. Serum albumins, such as bovine serum albumin (BSA), are abundant proteins in blood plasma with different biological functions. This paper presents a kinetic and spectroscopic study of the (1)O2-mediated oxidation of BSA using the tris(2,2'-bipyridine)ruthenium(II) cation [Ru(bpy)3](2+) as sensitizer. BSA quenches efficiently (1)O2 with a total (chemical+physical interaction) rate constant kt(BSA)=7.3(±0.4)×10(8)M(-1)s(-1), where the chemical pathway represented 37% of the interaction. This efficient quenching by BSA indicates the participation of several reactive residues. MALDI-TOF MS analysis of intact BSA confirmed that after oxidation by (1)O2, the mass protein increased the equivalent of 13 oxygen atoms. Time-resolved emission spectra analysis of BSA established that Trp residues were oxidized to N'-formylkynurenine, being the solvent-accessible W134 preferentially oxidized by (1)O2 as compared with the buried W213. MS confirmed oxidation of at least two Tyr residues to form dihydroxyphenylalanine, with a global reactivity towards (1)O2 six-times lower than for Trp residues. Despite the lack of MS evidences, kinetic and chemical analysis also suggested that residues other than Trp and Tyr, e.g. Met, must react with (1)O2. Modeling of the 3D-structure of BSA indicated that the oxidation pattern involves a random distribution of (1)O2 into BSA; allowing also the interaction of (1)O2 with buried residues by its diffusion from the bulk solvent through interconnected internal hydrophilic and hydrophobic grooves.

Antibody-Targeted Chemotherapy for the Treatment of Melanoma

Antibody-directed chemotherapy (ADC) offers an advantage over conventional chemotherapy because it provides antibody-directed targeting, with resultant improvement in therapeutic efficacy and reduced toxicity. Despite extensive research, with notable exceptions, broad clinical application of ADC remains elusive; major hurdles include the instability of antibody-chemotherapy linkers and reduced tumor toxicity of the chemotherapy when bound to the antibody. To address these challenges, we have developed a platform technology that utilizes the nab-paclitaxel formulation of paclitaxel, Abraxane, in which hydrophobic paclitaxel is suspended in 130-nm albumin nanoparticles and thus made water-soluble. We have developed a method to noncovalently coat the Abraxane nanoparticle with recombinant mAbs (anti-VEGF, bevacizumab) and guide Abraxane delivery into tumors in a preclinical model of human A375 melanoma. Here, we define the binding characteristics of bevacizumab and Abraxane, demonstrate that the chemotherapy agent retains its cytotoxic effect, while the antibody maintains the ability to bind its ligand when the two are present in a single nanoparticle (AB160), and show that the nanoparticle yields improved antitumor efficacy in a preclinical human melanoma xenograft model. Further data suggest that numerous therapeutic monoclonal IgG1 antibodies may be utilized in this platform, which has implications for many solid and hematologic malignancies. Cancer Res; 76(13); 3954-64. ©2016 AACR.

Tracking antitumor metallodrugs: promising agents with the Ru(II)- and Fe(II)-cyclopentadienyl scaffolds

Research on the field of metal complexes for the treatment of cancer diseases has attracted increasing interest due to the urgency in finding more efficient and selective treatments. Owing to their wide structural diversity, organometallic complexes appear as potential alternatives to the design of new anticancer candidates. Herein, we review recent progress in our work toward the development of new drugs based on Ru(II)- and Fe(II)-cyclopentadienyl scaffolds. Their design and chemical properties are reviewed and correlated with their biological effects, in particular the key role that coligands play in the overall behavior of the complex.

Albumin and multiple sclerosis

Leakage of the blood-brain barrier (BBB) is a common pathological feature in multiple sclerosis (MS). Following a breach of the BBB, albumin, the most abundant protein in plasma, gains access to CNS tissue where it is exposed to an inflammatory milieu and tissue damage, e.g., demyelination. Once in the CNS, albumin can participate in protective mechanisms. For example, due to its high concentration and molecular properties, albumin becomes a target for oxidation and nitration reactions. Furthermore, albumin binds metals and heme thereby limiting their ability to produce reactive oxygen and reactive nitrogen species. Albumin also has the potential to worsen disease. Similar to pathogenic processes that occur during epilepsy, extravasated albumin could induce the expression of proinflammatory cytokines and affect the ability of astrocytes to maintain potassium homeostasis thereby possibly making neurons more vulnerable to glutamate exicitotoxicity, which is thought to be a pathogenic mechanism in MS. The albumin quotient, albumin in cerebrospinal fluid (CSF)/albumin in serum, is used as a measure of blood-CSF barrier dysfunction in MS, but it may be inaccurate since albumin levels in the CSF can be influenced by multiple factors including: 1) albumin becomes proteolytically cleaved during disease, 2) extravasated albumin is taken up by macrophages, microglia, and astrocytes, and 3) the location of BBB damage affects the entry of extravasated albumin into ventricular CSF. A discussion of the roles that albumin performs during MS is put forth.

Developing an Anticancer Copper(II) Pro-Drug Based on the His242 Residue of the Human Serum Albumin Carrier IIA Subdomain

To increase delivery efficiency, anticancer activity, and selectivity of anticancer metal agents in vivo, we proposed to develop the anticancer metal pro-drug based on His242 residue of the human serum albumin (HSA) carrier IIA subdomain. To confirm our hypothesis, we prepared two Cu(II) compounds [Cu(P4 mT)Cl and Cu(Bp44 mT)Cl] by modifying Cu(II) compound ligand structure. Studies with two HSA complex structures revealed that Cu(P4 mT)Cl bound to the HSA subdomain IIA via hydrophobic interactions, but Cu(Bp44 mT)Cl bound to the HSA subdomain IIA via His242 replacement of a Cl atom of Cu(Bp44 mT)Cl, and a coordination to Cu(2+). Furthermore, Cu(II) compounds released from HSA could be regulated at different pHs. In vivo data revealed that the HSA-Cu(Bp44 mT) complex increased copper's selectivity and capacity of inhibiting tumor growth compared to Cu(Bp44 mT)Cl alone.

Impact of glycation on structural and antioxidant function of human serum albumin: Relevance in diabetic complications

AIM

Non-enzymatic glycation impairs the structural and functional characterstics of human serum albumin (HSA) native conformation. Prolonged hyperglycemia causes cross links formation in proteins that may contribute to progression of diabetic complications.

METHODS

HSA (20μM) was incubated with different concentration of d-glucose100, 200, 300 and 400mg/dl for a period of 40 days in phosphate buffer saline (20mM pH=7.4) under sterile conditions. Incubated samples were extensively dialyzed and structural changes were analyzed by far and near UV circular dichroism spectra measurement. Fructosamine assay with nitroblue tetrazolonium was performed to confer isomerisation between glucose and protein. Aggregations of the glycated product (AGEs) formed during reduction of nitrobluetetrazolium dye were evaluated by transmission electron microscopy. Crosslinks aggregates were investigated by in-situ Congo red binding assay. Red blood cells hemolysis test was performed to decipher the antioxidant activity of albumin samples.

RESULTS

Fructosamine content in glycated albumin demonstrates the non-enzymatic addition of glucose to HSA and confers the formation of monoformazone (marker of glycation). Significant changes were found in the glycated samples of HSA compared to native (unmodified) in far and near UV circular dichroism. Transmission electron microscopy, Congo red staining, showed the formation of crosslink's aggregated mass in glycated HSA. Glycation of albumin reduces the antioxidant capacity of native albumin confirmed by red blood cells hemolysis test.

CONCLUSION

The finding of present study brings new evidences on the detrimental alterations of on albumin vital functions after non-enzymatic glycation with glucose. These results may emphasize the albumin associated diabetic complications under glycemic range of diabetes mellitus.

Assessment of the Dissociation Energetics of Some Selected Ligand Drugs Bound on Human Serum Albumin by Differential Scanning Calorimetry

Drug-protein binding may play a role in the thermal energetics of protein denaturation and could lead to the determination of its equilibrium dissociation parameter. The aim of this study was to assess the energetics of a drug that was bound to human serum albumin (HSA) during thermal denaturation. Drugs that were bound at a single high-affinity primary binding site on HSA, including diazepam and ibuprofen, were employed. Commercial HSA was treated with charcoal to remove stabilizers and adjusted to 20% w/v in a pH 7.4 buffered solution. Serial concentrations of individual drugs up to 0.16 mmole/g-protein were added to the cleaned HSA solutions whereas diazepam was added to a commercial HSA solution. Samples were subjected to differential scanning calorimetry (DSC) set to run from 37 to 90°C at 3.0°C/min. Binding of the drug slightly increased the denaturing temperature of the cleaned HSA due to a shift in the equilibrium toward the native protein bound with the drug. Diazepam depressed the denaturing temperature of the commercial HSA by competing with the stabilizers already bound to the primary site of the HSA. This yielded not only the HSA-stabilizer but also the HSA-diazepam type complexes that exhibited a different denaturation process. A rational approximation of the Lumry-Eyring protein denaturation model was used to treat the DSC endotherms. The approximated scheme: [Formula: see text] was successfully fitted to the data. It was used to determine the dissociation parameters for diazepam and ibuprofen bound to the HSA. These results were comparable to those obtained from other methods.

Improved dialytic removal of protein-bound uraemic toxins with use of albumin binding competitors: an in vitro human whole blood study

Protein-bound uraemic toxins (PBUTs) cause various deleterious effects in end-stage kidney disease patients, because their removal by conventional haemodialysis (HD) is severely limited by their low free fraction in plasma. Here we provide an experimental validation of the concept that the HD dialytic removal of PBUTs can be significantly increased by extracorporeal infusion of PBUT binding competitors. The binding properties of indoxyl sulfate (IS), indole-3-acetic acid (IAA) and hippuric acid (HIPA) and their binding competitors, ibuprofen (IBU), furosemide (FUR) and tryptophan (TRP) were studied in uraemic plasma. The effect of binding competitor infusion on fractional removal of PBUT was then quantified in an ex vivo single-pass HD model using uraemic human whole blood. The infusion of a combination of IBU and FUR increased the fractional removal of IS from 6.4 ± 0.1 to 18.3 ± 0.4%. IAA removal rose from 16.8 ± 0.3 to 34.5 ± 0.7%. TRP infusion increased the removal of IS and IAA to 10.5 ± 0.1% and 27.1 ± 0.3%, respectively. Moderate effects were observed on HIPA removal. Pre-dialyzer infusion of PBUT binding competitors into the blood stream can increase the HD removal of PBUTs. This approach can potentially be applied in current HD settings.

Risk factors for postoperative complications following oral surgery

Objective

The objective of this study was to clarify significant risk factors for postoperative complications in the oral cavity in patients who underwent oral surgery, excluding those with oral cancer.

Material and Methods

This study reviewed the records of 324 patients who underwent mildly to moderately invasive oral surgery (e.g., impacted tooth extraction, cyst excision, fixation of mandibular and maxillary fractures, osteotomy, resection of a benign tumor, sinus lifting, bone grafting, removal of a sialolith, among others) under general anesthesia or intravenous sedation from 2012 to 2014 at the Department of Oral and Maxillofacial Reconstructive Surgery, Hiroshima University Hospital.

Results

Univariate analysis showed a statistical relationship between postoperative complications (i.e., surgical site infection, anastomotic leak) and diabetes (p=0.033), preoperative serum albumin level (p=0.009), and operation duration (p=0.0093). Furthermore, preoperative serum albumin level (<4.0 g/dL) and operation time (≥120 minutes) were found to be independent factors affecting postoperative complications in multiple logistic regression analysis results (odds ratio 3.82, p=0.0074; odds ratio 2.83, p=0.0086, respectively).

Conclusion

Our results indicate that a low level of albumin in serum and prolonged operation duration are important risk factors for postoperative complications occurring in the oral cavity following oral surgery.

Human plasma lipocalins and serum albumin: Plasma alternative carriers?

Lipocalins are an evolutionarily conserved family of proteins that bind and transport a variety of exogenous and endogenous ligands. Lipocalins share a conserved eight anti-parallel β-sheet structure. Among the different lipocalins identified in humans, α-1-acid glycoprotein (AGP), apolipoprotein D (apoD), apolipoprotein M (apoM), α1-microglobulin (α1-m) and retinol-binding protein (RBP) are plasma proteins. In particular, AGP is the most important transporter for basic and neutral drugs, apoD, apoM, and RBP mainly bind endogenous molecules such as progesterone, pregnenolone, bilirubin, sphingosine-1-phosphate, and retinol, while α1-m binds the heme. Human serum albumin (HSA) is a monomeric all-α protein that binds endogenous and exogenous molecules like fatty acids, heme, and acidic drugs. Changes in the plasmatic levels of lipocalins and HSA are responsible for the onset of pathological conditions associated with an altered drug transport and delivery. This, however, does not necessary result in potential adverse effects in patients because many drugs can bind both HSA and lipocalins, and therefore mutual compensatory binding mechanisms can be hypothesized. Here, molecular and clinical aspects of ligand transport by plasma lipocalins and HSA are reviewed, with special attention to their role as alterative carriers in health and disease.

Electron microscopy imaging of proteins on gallium phosphide semiconductor nanowires

We have imaged GaP nanowires (NWs) incubated with human laminin, serum albumin (HSA), and blood plasma using both cryo-transmission electron microscopy and synchrotron based X-ray photoemission electron microscopy. This extensive imaging methodology simultaneously reveals structural, chemical and morphological details of individual nanowires and the adsorbed proteins. We found that the proteins bind to NWs, forming coronas with thicknesses close to the proteins' hydrodynamic diameters. We could directly image how laminin is extending from the NWs, maximizing the number of proteins bound to the NWs. NWs incubated with both laminin and HSA show protein coronas with a similar appearance to NWs incubated with laminin alone, indicating that the presence of HSA does not affect the laminin conformation on the NWs. In blood plasma, an intermediate sized corona around the NWs indicates a corona with a mixture of plasma proteins. The ability to directly visualize proteins on nanostructures in situ holds great promise for assessing the conformation and thickness of the protein corona, which is key to understanding and predicting the properties of engineered nanomaterials in a biological environment.

Generation of TALE nickase-mediated gene-targeted cows expressing human serum albumin in mammary glands

Targeting exogenous genes at milk protein loci via gene-targeting technology is an ideal strategy for producing large quantities of pharmaceutical proteins. Transcription- activator-like effector (TALE) nucleases (TALENs) are an efficient genome-editing tool. However, the off-target effects may lead to unintended gene mutations. In this study, we constructed TALENs and TALE nickases directed against exon 2 of the bovine β-lactoglobulin (BLG) locus. The nickases can induce a site-specific DNA single-strand break, without inducing double-strand break and nonhomologous end joining mediated gene mutation, and lower cell apoptosis rate than TALENs. After co-transfecting the bovine fetal fibroblasts with human serum albumin (HSA) gene-targeting vector and TALE nickase expression vectors, approximately 4.8% (40/835) of the cell clones contained HSA at BLG locus. Unexpectedly, one homozygous gene-targeted cell clone (1/835, 0.1%) was obtained by targeting both alleles of BLG in a single round of transfection. The recombinant protein mimicking the endogenous BLG was highly expressed and correctly folded in the mammary glands of the targeted cows, and the expression level of HSA was significantly increased in the homozygous targeted cows. Results suggested that the combination of TALE nickase-mediated gene targeting and somatic cell nuclear transfer is a feasible and safe approach in producing gene-targeted livestock.

Serum Albumin Is an Independent Predictor of Clinical Outcomes in Critically Ill Children

OBJECTIVES

Serum albumin is a strong biomarker of disease severity and prognosis in adult patients. In contrast, its value as predictor of outcome in critically ill children has not been established. We aimed to determine whether admission hypoalbuminemia is associated with outcome in a general pediatric population of critically ill patients, taking into account the inflammatory response, disease severity, and nutritional status of the patient.

DESIGN

Analysis of prospectively collected database.

SETTING

PICU of a teaching hospital.

PATIENTS

Two hundred seventy-one patients consecutively admitted. Neonates, patients with chronic liver or kidney disease, inborn errors of metabolism, those who received prior administration of albumin solution, and readmissions were excluded.

MEASUREMENTS AND MAIN RESULTS

Outcome variables were 60-day mortality, probability of ICU discharge at 60 days, and ventilator-free days. Potential exposure variables for the outcome were sex, age, nutritional status, albumin, C-reactive protein and serum lactate at admission, and Pediatric Index of Mortality 2 score. Admission hypoalbuminemia was present in 64.2% of patients. After adjustment for confounding factors, only serum lactate, Pediatric Index of Mortality 2 score, and serum albumin were associated with higher mortality: the increase of 1.0 g/dL in serum albumin at admission resulted in a 73% reduction in the hazard of death (hazard ratio, 0.27; 95% CI, 0.14-0.51; p < 0.001). The increase of 1 g/dL in serum albumin was also independently associated with a 33% rise in the probability of ICU discharge (subhazard ratio, 1.33; 95% CI, 1.07-1.64; p = 0.008) and increased ventilator-free-days (odds ratio, 1.86; 95% CI, 0.56-3.16; p = 0.005).

CONCLUSIONS

Hypoalbuminemia at admission to a PICU is associated with higher 60-day mortality, longer duration of mechanical ventilation, and lower probability of ICU discharge. These associations are independent of the magnitude of inflammatory response, clinical severity, and nutritional status.

TAT-HSA-α-MSH fusion protein with extended half-life inhibits tumor necrosis factor-α in brain inflammation of mice

Neuroinflammation constitutes a principal process involved in the progression of various central nervous system (CNS) disorders, including Parkinson's disease, Alzheimer's disease, ischemic stroke, and traumatic brain injury. The safety and efficacy of potential neuroprotective therapeutic agents is controversial and limited. Alpha-melanocyte-stimulating hormone (α-MSH) as a tridecapeptide derived from pro-opiomelanocortin displays potent anti-inflammatory and protective effects with a wide therapeutic window in brain damage. However, it is difficult to deliver effective concentrations of α-MSH into brain tissue via nondirect application. Besides, the half-life of the tridecapeptide is only a few minutes. In the present study, we generated a novel TAT-HSA-α-MSH by genetically fusing α-MSH with N-terminus 11-amino acid protein transduction domain of the human immunodeficiency virus Tat protein (TAT) and human serum albumin (HSA), which showed favorable pharmacokinetic properties and can effectively cross the blood brain barrier (BBB). The findings showed that TAT-HSA-α-MSH significantly inhibits NF-κB activation in human glioma cells A172 and tumor necrosis factor-α (TNF-α) production in experimental brain inflammation. These results indicate that TAT-HSA-α-MSH may be a potential therapeutic agent for treating neuroinflammation which plays a fundamental role in CNS disorders.

Mass spectrometry characterization of circulating human serum albumin microheterogeneity in patients with alcoholic hepatitis

Human serum albumin (HSA) is the most abundant plasma protein, endowed with several biological properties unrelated to its oncotic power, such as antioxidant and free-radicals scavenging activities, binding and transport of many endogenous and exogenous substances, and regulation of endothelial function and inflammatory response. These non-oncotic activities are closely connected to the peculiarly dynamic structure of the albumin molecule. HSA undergoes spontaneous structural modifications, mainly by reaction with oxidants and saccharides; however, patients with cirrhosis show extensive post-transcriptional changes at several molecular sites of HSA, the degree of which parallels the severity of the disease. The present work reports the development and application of an innovative LC-MS analytical method for a rapid and reproducible determination of the relative abundance of HSA isoforms in plasma samples from alcoholic hepatitis (AH) patients. A condition of severe oxidative stress, similar to that observed in AH patients, is associated with profound changes in circulating HSA microheterogeneity. More interestingly, the high resolution provided by the analytical platform allowed the monitoring of novel oxidative products of HSA never reported before.

Recombinant HSA-CMG2 Is a Promising Anthrax Toxin Inhibitor

Anthrax toxin is the major virulence factor produced by Bacillus anthracis. Protective antigen (PA) is the key component of the toxin and has been confirmed as the main target for the development of toxin inhibitors. The inhibition of the binding of PA to its receptor, capillary morphogenesis protein-2 (CMG2), can effectively block anthrax intoxication. The recombinant, soluble von Willebrand factor type A (vWA) domain of CMG2 (sCMG2) has demonstrated potency against anthrax toxin. However, the short half-life of sCMG2 in vivo is a disadvantage for its development as a new anthrax drug. In the present study, we report that HSA-CMG2, a protein combining human serum albumin (HSA) and sCMG2, produced in the Pichia pastoris expression system prolonged the half-life of sCMG2 while maintaining PA binding ability. The IC50 of HSA-CMG2 is similar to those of sCMG2 and CMG2-Fc in in vitro toxin neutralization assays, and HSA-CMG2 completely protects rats from lethal doses of anthrax toxin challenge; these same challenge doses exceed sCMG2 at a sub-equivalent dose ratio and overwhelm CMG2-Fc. Our results suggest that HSA-CMG2 is a promising inhibitor of anthrax toxin and may contribute to the development of novel anthrax drugs.

Oxidative changes in the blood and serum albumin differentiate rats with monoarthritis and polyarthritis

Adjuvant arthritis in rats, as rheumatoid arthritis in humans, may be of greater or lesser severity, namely polyarthritis and monoarthritis, respectively. The present study was planned to evaluate the oxidative changes in the blood and specifically in the serum albumin of rats with adjuvant-induced mono- and poly-arthritis. Total antioxidant capacity, thiols, carbonyl groups, albumin, uric acid and ascorbic acid were measured in the total serum. The specific oxidative status of albumin was also measured after separation by affinity chromatography. All serum oxidative parameters were close to normal in monoarthritic rats with the exception of the ascorbic acid concentration, which was 23 % lower, and albumin carbonyl groups, which were 64 % higher. Many modifications were found in polyarthritic rats, specially the ascorbic acid concentration (35 % lower) and albumin carbonyl groups (102 % higher). The results revealed that the levels of ascorbic acid in the serum and carbonyl groups in the albumin molecule can be regarded as indicators of the severity of arthritis since they were modified by both monoarthritis and polyarthritis, but to different degrees.

Binding of Sulpiride to Seric Albumins

The aim of this work was to study the interaction of sulpiride with human serum albumin (HSA) and bovine serum albumin (BSA) through the fluorescence quenching technique. As sulpiride molecules emit fluorescence, we have developed a simple mathematical model to discriminate the quencher fluorescence from the albumin fluorescence in the solution where they interact. Sulpiride is an antipsychotic used in the treatment of several psychiatric disorders. We selectively excited the fluorescence of tryptophan residues with 290 nm wavelength and observed the quenching by titrating HSA and BSA solutions with sulpiride. Stern-Volmer graphs were plotted and quenching constants were estimated. Results showed that sulpiride form complexes with both albumins. Estimated association constants for the interaction sulpiride–HSA were 2.20 (±0.08) × 10⁴ M⁻¹, at 37 °C, and 5.46 (±0.20) × 10⁴ M⁻¹, at 25 °C. Those for the interaction sulpiride-BSA are 0.44 (±0.01) × 10⁴ M⁻¹, at 37 °C and 2.17 (±0.04) × 10⁴ M⁻¹, at 25 °C. The quenching intensity of BSA, which contains two tryptophan residues in the peptide chain, was found to be higher than that of HSA, what suggests that the primary binding site for sulpiride in albumin should be located next to the sub domain IB of the protein structure.

Ultrasonic frequency analysis for estimating pH in albumin-rich biofluids

Ultrasound is known as a non-invasive imaging modality capable of propagating through highly scattering media such as tissue, blood, and other biological fluids, yet currently provides little chemical information. We have developed a straightforward and rapid methodology for estimating pH in albumin-rich biofluids based on analysis of ultrasonic frequencies. Albumin is the most abundant protein in serum and undergoes conformational changes with pH. It was shown that when ultrasound propagated through albumin solutions, the attenuation of collected ultrasound signals increased with pH. By measuring the ultrasound frequency spectra at several albumin concentrations and pH values, the pH of the solutions could be determined by multilinear regression. Differences in absolute protein content contributed to signal differences in the frequency profiles and were minimized through normalization of each spectrum by the sum of all its frequency intensities. This strategy was applied to human serum samples from multiple donors, for which a multilinear regression model was developed with a coefficient of determination (R(2)) of 0.93 and a standard error of estimate (SEE) of 0.08 pH units. The use of albumin as a pH indicator opens the doors for estimations in other albumin-rich media, such as amniotic fluid and cerebrospinal fluid.

An octamolybdate-metal organic framework hybrid for the efficient adsorption of histidine-rich proteins

Incorporation of octamolybdate (Mo₈O₂₆) into the metal–organic framework, MIL-101(Cr), produces a novel hybrid. The covalent interactions of the Mo₈O₂₆ moiety in the hybrid with the N-terminal site and the multi-metal binding site of proteins offer favorable adsorption performance towards histidine-rich proteins.

AISF-SIMTI Position Paper: The appropriate use of albumin in patients with liver cirrhosis

The use of human albumin is common in hepatology since international scientific societies support its administration to treat or prevent severe complications of cirrhosis, such as the prevention of post-paracentesis circulatory dysfunction after large-volume paracentesis and renal failure induced by spontaneous bacterial peritonitis, and the treatment of hepatorenal syndrome in association with vasoconstrictors. However, these indications are often disregarded, mainly because the high cost of human albumin leads health authorities and hospital administrations to restrict its use. On the other hand, physicians often prescribe human albumin in patients with advanced cirrhosis for indications that are not supported by solid scientific evidence and/or are still under investigation in clinical trials. In order to implement appropriate prescription of human albumin and to avoid its futile use, the Italian Association for the Study of the Liver (AISF) and the Italian Society of Transfusion Medicine and Immunohaematology (SIMTI) nominated a panel of experts, who reviewed the available clinical literature and produced practical clinical recommendations for the use of human albumin in patients with cirrhosis.

Non-enzymatic glycation mediated structure–function changes in proteins: case of serum albumin

Albumin, a major plasma protein with extraordinary ligand binding properties, transports various ligands ranging from drugs, hormones, fatty acids, and toxins to different tissues and organs in the body.

Dimeric binding of plant alkaloid ellipticine to human serum proteins

Induced exciton circular dichroism signals reveal the accommodation of a pair of ellipticine molecules to the subdomain IB of human serum albumin and the β-barrel of α₁-acid glycoprotein.

Hypoalbuminemia and Osteoporosis: Reappraisal of a Controversy

CONTEXT

Human studies have reported conflicting results on the association of hypoalbuminemia with osteoporosis.

OBJECTIVE

The aim of the study is to test the independent association between hypoalbuminemia and osteoporosis.

DESIGN

This is a cross-sectional observation.

SETTING AND PARTICIPANTS

Patients are the outpatient consecutive individuals with available clinical, laboratory, and densitometry data from 2001 to 2013 in our tertiary care academic medical center.

EXPOSURE

Exposure is hypoalbuminemia defined as serum albumin less than 3.5 g/dL.

MAIN OUTCOME MEASURE

Osteoporosis is defined as bone mineral density of 2.5 SD or less below the mean peak bone mass of young, healthy adults.

RESULTS

Overall, 21 121 patients were included. Mean of age was 61 years (SD 14). There were 4244 males (20.1%) and 1614 patients of African-American ethnicity (7.6%). There was a graded decrease in rate of osteoporosis from 28.0% (n = 33) at albumin of 3 g/dL or less to 9.3% (n = 1548) at albumin greater than 4 g/dL (P < .001) at the femoral neck and from 20.3% (n = 24) to 6.1% (n = 1011) at the total hip (P < .001). In a fully adjusted model, the odds of osteoporosis at albumin of 3 g/dL or less was 3.31-fold (95% confidence interval [CI] 2.08-5.28, P < .001) at the femoral neck, 2.98-fold (95% CI 1.76-5.01, P < .001) at the total hip, and 2.18-fold (95% CI 1.43-3.31, P < .001) at the lumbar spine as compared with albumin greater than 4 mg/dL. A similar independent association was identified with a longer-observed duration of hypoalbuminemia.

CONCLUSION

In a large population, we report an independent association of osteoporosis with lower levels of serum albumin and a longer-observed duration of hypoalbuminemia.

Blood-borne biomarkers and bioindicators for linking exposure to health effects in environmental health science

Environmental health science aims to link environmental pollution sources to adverse health outcomes to develop effective exposure intervention strategies that reduce long-term disease risks. Over the past few decades, the public health community recognized that health risk is driven by interaction between the human genome and external environment. Now that the human genetic code has been sequenced, establishing this "G × E" (gene-environment) interaction requires a similar effort to decode the human exposome, which is the accumulation of an individual's environmental exposures and metabolic responses throughout the person's lifetime. The exposome is composed of endogenous and exogenous chemicals, many of which are measurable as biomarkers in blood, breath, and urine. Exposure to pollutants is assessed by analyzing biofluids for the pollutant itself or its metabolic products. New methods are being developed to use a subset of biomarkers, termed bioindicators, to demonstrate biological changes indicative of future adverse health effects. Typically, environmental biomarkers are assessed using noninvasive (excreted) media, such as breath and urine. Blood is often avoided for biomonitoring due to practical reasons such as medical personnel, infectious waste, or clinical setting, despite the fact that blood represents the central compartment that interacts with every living cell and is the most relevant biofluid for certain applications and analyses. The aims of this study were to (1) review the current use of blood samples in environmental health research, (2) briefly contrast blood with other biological media, and (3) propose additional applications for blood analysis in human exposure research.

Hypoalbuminemia in colorectal cancer prognosis: Nutritional marker or inflammatory surrogate?

Albumin is the single most abundant protein in the human serum. Its roles in physiology and pathology are diverse. Serum albumin levels have been classically thought to reflect the nutritional status of patients. This concept has been challenged in the last two decades as multiple factors, such as inflammation, appeared to affect albumin levels independent of nutrition. In general, cancer patients have a high prevalence of hypoalbuminemia. As such, the role of hypoalbuminemia in patients with colorectal cancer has received significant interest. We reviewed the English literature on the prognostic value of pretreatment albumin levels in colorectal cancer. We also consolidated the evidence that led to the current understanding of hypoalbuminemia as an inflammatory marker rather than as a nutritional one among patients with colorectal cancer.

Human Albumin Improves Long-Term Behavioral Sequelae After Subarachnoid Hemorrhage Through Neurovascular Remodeling

OBJECTIVE

Subarachnoid hemorrhage results in significant long-lasting neurologic sequelae. Here, we investigated whether human albumin improves long-term outcomes in experimental subarachnoid hemorrhage and whether neurovascular remodeling is involved in the protection of albumin.

DESIGN

Laboratory investigation.

SETTING

Hospital research laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Rats underwent subarachnoid hemorrhage by endovascular perforation. Albumin of either 0.63 or 1.25 g/kg was injected IV immediately after the surgery. Modified Garcia test, beam-walking test, novel object recognition, and Morris water maze were employed to determine the behavioral deficits. The effects of albumin on early neurovascular dysfunction and chronic synaptic plasticity were also studied.

MEASUREMENTS AND MAIN RESULTS

Both doses of albumin significantly improved the sensorimotor scores (F = 31.277; p = 0.001) and cognitive performance (F = 7.982; p = 0.001 in novel object recognition test; and F = 3.431; p = 0.026 in the latency analysis of Morris water maze test) for at least 40 days after subarachnoid hemorrhage. There were remarkable microvasculature hypoperfusion, intracranial pressure rise, early vasoconstriction, neural apoptosis, and degeneration in subarachnoid hemorrhage rats, with albumin significantly attenuating such neurovascular dysfunction. Furthermore, albumin markedly prevented blood-brain barrier disruption, as indicated by less blood-brain barrier leakage, preserved blood-brain barrier-related proteins, and dampened gelatinase activities. The expressions of key synaptic elements were up-regulated with albumin supplementation in both acute and chronic phases. Accordingly, a higher dendritic spine density was observed in the prefrontal and hippocampal areas of albumin-treated subarachnoid hemorrhage animals.

CONCLUSIONS

Albumin at low-to-moderate doses markedly improves long-term neurobehavioral sequelae after subarachnoid hemorrhage, which may involve an integrated process of neurovascular remodeling.

Insulin Is Required to Maintain Albumin Expression by Inhibiting Forkhead Box O1 Protein

Diabetes is accompanied by dysregulation of glucose, lipid, and protein metabolism. In recent years, much effort has been spent on understanding how insulin regulates glucose and lipid metabolism, whereas the effect of insulin on protein metabolism has received less attention. In diabetes, hepatic production of serum albumin decreases, and it has been long established that insulin positively controls albumin gene expression. In this study, we used a genetic approach in mice to identify the mechanism by which insulin regulates albumin gene transcription. Albumin expression was decreased significantly in livers with insulin signaling disrupted by ablation of the insulin receptor or Akt. Concomitant deletion of Forkhead Box O1 (Foxo1) in these livers rescued the decreased albumin secretion. Furthermore, activation of Foxo1 in the liver is sufficient to suppress albumin expression. These results suggest that Foxo1 acts as a repressor of albumin expression.