Afamin is a new member of the albumin, alpha-fetoprotein, and vitamin D-binding protein gene family

Sex Differences in the Serum Proteomic Profile During Acute Low Back Pain-A Preliminary Study of the Relationship to Future Low Back Pain

The molecular processes driving the transition from acute to chronic low back pain (LBP) remain poorly understood and are likely to be sexually dimorphic. This study aimed to explore sex differences in the serum proteomic profile of people experiencing an acute LBP episode and determine if serum protein concentrations were associated with three-month outcome. Serum samples were collected through venepuncture from 30 female and 29 male participants experiencing an acute LBP episode. Serum samples underwent trypsin digestion and fractionation using hydrophobic interaction chromatography and were then analysed using mass-spectrometry. Mass-spectrometry spectra were searched in the Swissprot database for protein identification. Sex differences in protein abundance changes were evident upon inspection of fold changes. Multivariable data analysis identified 21 serum proteins during the acute episode that correctly classified 93% of males and 23 serum proteins that correctly classified 90% of females with ongoing LBP at 3 months. Pathway analysis suggested the differentially expressed proteins during acute LBP were frequently involved in immune, inflammatory, complement, or coagulation responses. This data provides preliminary evidence that biological processes during an acute LBP episode may contribute to the resolution, or persistence, of LBP symptoms at 3 months, however, these processes differ between males and females. PERSPECTIVE: Differential expression of serum proteins was observed between male and female participants during an acute LBP episode. This preliminary work provides a foundation for future research targeting distinct immune system processes in males and females that may interfere with the transition from acute to chronic LBP.

Circulating afamin positively correlated with the miR-122 expression and type 2 diabetes mellitus-related phenotype according to the duration of diabetes

Background

Afamin is a hepatokine that involves in glucose and lipids metabolism. miR-122 is mainly expressed in liver and involves in lipid and carbohydrate metabolism. This study aimed at investigating the circulating afamin, its correlation with type 2 diabetes mellitus (T2DM) and miR-122 gene expression in T2DM patients and healthy control subjects according to the duration of diabetes.

Methods

This case-control study included 220 participants, with 100 individuals serving as controls and 120 individuals diagnosed with type 2 diabetes mellitus (T2DM). The miR-122 gene expression was assessed using real-time PCR. The serum concentration of biochemical parameters such as glucose levels, lipid profile, and small-dense low-density lipoprotein (sdLDL) were measured using colorimetric kits. Circulating afamin and insulin levels were assayed using an ELISA kit. Glycated hemoglobin (HbA1c) was measured using capillary electrophoresis.

Results

Circulating afamin level was significantly higher in T2DM patients compared to the control group, (73.8 ± 10.8 vs. 65.9 ± 8.7, respectively; P < 0.001). Similarly, miR122 expression was significantly increased in T2DM patients compared to healthy control subjects (4.24 ± 2.01 vs. 1.00 ± 0.85, respectively; P < 0.001). Among patients diagnosed with T2DM, those with longstanding diabetes (>5 years) exhibited significantly higher levels of circulating afamin and miR-122 expression compared to individuals with a shorter duration of diabetes (≤5 years) (P < 0.05). Circulating afamin levels were significantly correlated with waist circumference, small-dense low-density lipoprotein (sdLDL), fasting blood sugar (FBS), insulin, resistance to insulin, and miR-122 expression, depending on the duration of the disease (P < 0.05). Furthermore, the performance of afamin as a diagnostic marker for T2DM was confirmed through receiver operating characteristic (ROC) analysis, yielding an area under the curve (AUC) of 0.7 (P < 0.001).

Conclusions

Circulating afamin involved in the T2DM-related complications and its concentration is positively correlated to the miR-122 expression, especially in patient with longstanding diabetes.

Comparison of Afamin Values in Umbilical Cord Blood After Delivery in Pregnancies With and Without Gestational Diabetes Mellitus

OBJECTIVE

Afamin is a protein that increases in gestational diabetes but its concentration in neonates hasn't been investigated. Our objective is to compare cord blood afamin levels in neonates born to mothers with and without diabetes, and to explore its relationship with maternal and neonatal variables.

METHODS

In this case control study, umbilical cord blood was collected for afamin measurement in pregestational/gestational diabetic pregnancies (n = 40) and healthy pregnancies (n = 45) after delivery. Correlation analysis was conducted to examine the relationship between afamin levels and maternal BMI, age, HbA1c, fasting and postprandial blood glucose, gestational age, birth weight.

RESULTS

The diabetic group had a higher median afamin level (p < 0.001). Afamin concentrations did not differ significantly between diabetic subgroups. The concentration of afamin in cord blood was independent of maternal BMI, age, HbA1c, blood glucose, gestational age, birth weight.

CONCLUSION

The concentration of afamin in cord blood of diabetic pregnancies is significantly higher, irrespective of other clinical factors.

Serum afamin and its implications in adult growth hormone deficiency: a prospective GH-withdrawal study

Introduction

Adult growth hormone deficiency (AGHD) is associated with a high prevalence of metabolic syndrome (MS), which contributes to the unfavorable cardiovascular risk profile in these patients. Insulin like growth factor-1 (IGF-1) is a widely used biomarker, however it does not always reflect the cardiometabolic risk and has a poor relationship with clinical efficacy endpoints. Consequently, there is an unmet need for biomarkers to monitor responses to GH-replacement. Afamin is a hormone-like glycoprotein, expressed in the liver. Higher afamin levels are strongly associated with MS and insulin resistance (IR). Although both MS and IR are very common in AGHD, afamin has not been investigated in these patients.

Purpose

To investigate afamin as a potential biomarker in patients with AGHD.

Materials and methods

Participants included 20 AGHD patients (11 GH-substituted and 9 GH-unsubstituted) and 37 healthy controls. Subjects underwent routine laboratory examinations, anthropometric measurements, body composition analysis using multi-frequency bioelectrical impedance analysis (InBody720) and measurement of serum afamin concentrations. In GH-substituted subjects, GH-substitution was withdrawn for 2 months. Measurements were carried out right before GH-withdrawal, at the end of the 2-month withdrawal period, and 1 month after reinstituting GH-replacement therapy (GHRT).

Results

GH-unsubstituted patients demonstrated higher afamin levels compared to controls (p=0.03). Afamin positively correlated with skeletal muscle mass, bone mineral content, total body water, extracellular- and intracellular water content, insulin (all, p<0.01), HOMA-IR (p=0.01) and C-peptide (p=0.03) levels in AGHD but not in healthy controls. In GH-substituted patients 2-month of GH-withdrawal caused significant changes in body composition, including decreased fat-free mass, skeletal muscle mass, total body water, and intracellular water content (all, p<0.01); but these changes almost fully recovered 1 month after reinstituting GHRT. Unexpectedly, afamin levels decreased after GH-withdrawal (p=0.03) and increased with reinstitution (p<0.01). Changes of afamin levels during GH-withdrawal positively correlated with changes of HOMA-IR (r=0.80; p<0.01) and changes of insulin (r=0.71; p=0.02).

Conclusion

Higher afamin levels in unsubstituted AGHD patients might indicate severe metabolic dysregulation. Significant changes accompanying GH-withdrawal and reinstitution, along with strong correlations with measures of IR, suggest that afamin could be a promising biomarker to monitor GHRT-associated changes of insulin sensitivity.

Multiplexed MRM-based proteomics for identification of circulating proteins as biomarkers of cardiovascular damage progression associated with diabetes mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) increases the risk of coronary heart disease (CHD) by 2-4 fold, and is associated with endothelial dysfunction, dyslipidaemia, insulin resistance, and chronic hyperglycaemia. The aim of this investigation was to assess, by a multimarker mass spectrometry approach, the predictive role of circulating proteins as biomarkers of cardiovascular damage progression associated with diabetes mellitus.

METHODS

The study considered 34 patients with both T2DM and CHD, 31 patients with T2DM and without CHD, and 30 patients without diabetes with a diagnosis of CHD. Plasma samples of subjects were analysed through a multiplexed targeted liquid chromatography mass spectrometry (LC-MS)-based assay, namely Multiple Reaction Monitoring (MRM), allowing the simultaneous detection of peptides derived from a protein of interest. Gene Ontology (GO) Analysis was employed to identify enriched GO terms in the biological process, molecular function, or cellular component categories. Non-parametric multivariate methods were used to classify samples from patients and evaluate the relevance of the analysed proteins' panel.

RESULTS

A total of 81 proteins were successfully quantified in the human plasma samples. Gene Ontology analysis assessed terms related to blood microparticles, extracellular exosomes and collagen-containing extracellular matrix. Preliminary evaluation using analysis of variance (ANOVA) of the differences in the proteomic profile among patient groups identified 13 out of the 81 proteins as significantly different. Multivariate analysis, including cluster analysis and principal component analysis, identified relevant grouping of the 13 proteins. The first main cluster comprises apolipoprotein C-III, apolipoprotein C-II, apolipoprotein A-IV, retinol-binding protein 4, lysozyme C and cystatin-C; the second one includes, albeit with sub-grouping, alpha 2 macroglobulin, afamin, kininogen 1, vitronectin, vitamin K-dependent protein S, complement factor B and mannan-binding lectin serine protease 2. Receiver operating characteristic (ROC) curves obtained with the 13 selected proteins using a nominal logistic regression indicated a significant overall distinction (p < 0.001) among the three groups of subjects, with area under the ROC curve (AUC) ranging 0.91-0.97, and sensitivity and specificity ranging from 85 to 100%.

CONCLUSIONS

Targeted mass spectrometry approach indicated 13 multiple circulating proteins as possible biomarkers of cardiovascular damage progression associated with T2DM, with excellent classification results in terms of sensitivity and specificity.

Investigation of serum afamin concentration in pregnant women diagnosed with late fetal growth restriction or small for gestational age fetus

OBJECTIVE

To investigate the afamin concentration in the serum of pregnant women diagnosed with late fetal growth restriction (FGR) or small for gestational age (SGA) in the third trimester.

METHODS

This prospective case-control study was conducted on 126 pregnant women, 42 of whom were diagnosed with late FGR in the third trimester, 43 were SGA, and 41 were healthy controls. The groups were compared in terms of maternal serum afamin concentrations.

RESULTS

Three groups were similar in terms of demographic characteristics and gestational age at blood sampling for afamin (p < .05). The median afamin concentration was determined as 199 ng/mL in the late FGR group, 153 ng/mL in the SGA group, and 108 ng/mL in the control group (p = .000). In the post-hoc analysis, while maternal serum afamin concentrations were found to be significantly higher in the late FGR group and SGA group compared to the control group but, this significance could not be shown between the FGR group and the SGA group (p = .00001, p = .005, p = .137, respectively). In the ROC analysis, the optimal cutoff value of serum afamin concentration to predict late FGR was determined as 141 ng/mL, with a sensitivity of 66.6% and a specificity of 85.3%.

CONCLUSIONS

The serum afamin concentration in the third trimester was found to be higher in pregnant women with late FGR compared to the SGA and control groups. Although afamin is seen as a promising molecule in the clinical prediction of late FGR, this needs to be supported by large series of studies.

Early Pregnancy Markers in the Serum of Ewes Identified via Proteomic and Metabolomic Analyses

The diagnosis of ewes' pregnancy status at an early stage is an efficient way to enhance the reproductive output of sheep and allow producers to optimize production and management. The techniques of proteomics and metabolomics have been widely used to detect regulatory factors in various physiological processes of animals. The aim of this study is to explore the differential metabolites and proteins in the serum of pregnant and non-pregnant ewes by proteomics and metabolomics. The serum of ewes at 21, 28 and 33 days after artificial insemination (AI) were collected. The pregnancy stratus of the ewes was finally determined through ultrasound examination and then the ewes were grouped as Pregnant (n = 21) or N on-pregnant (n = 9). First, the serum samples from pregnant or non-pregnant ewes at 21 days after AI were selected for metabolomic analysis. It was found that the level of nine metabolites were upregulated and 20 metabolites were downregulated in the pregnant animals (p < 0.05). None of these differential metabolomes are suitable as markers of pregnancy due to their small foldchange. Next, the proteomes of serum from pregnant or non-pregnant ewes were evaluated. At 21 days after AI, the presence of 321 proteins were detected, and we found that the level of three proteins were upregulated and 11 proteins were downregulated in the serum of pregnant ewes (p < 0.05). The levels of serum amyloid A (SAA), afamin (AFM), serpin family A member 6 (SERPINA6) and immunoglobulin-like domain-containing protein between pregnant and non-pregnant ewes at 21-, 28- and 33-days post-AI were also analyzed via enzyme-linked immunosorbent assay (ELISA). The levels of SAA and AFM were significantly higher in pregnant ewes than in non-pregnant ewes, and could be used as markers for early pregnancy detection. Overall, our results show that SAA and AFM are potential biomarkers to determine the early pregnancy status of ewes.

Clinical Significance of Neuregulin 4, Afamin, and SERPINB1 in Gestational Diabetes Mellitus and Their Relationship with Insulin Resistance

Objective

This study aims to explore the serum levels of neuregulin 4 (NRG4), afamin (AFM), and serpin family B member 1 (SERPINB1) in gestational diabetes mellitus (GDM) patients and their relationship with insulin resistance.

Method

Serum levels of AFM, SERPINB1, and NRG4 were measured in GDM (n = 58), and non-GDM women (n = 60) using enzyme-linked immunosorbent assay (ELISA) kits. Besides, the serum insulin and glucose levels were also measured followed by calculating the homeostatic model assessment of insulin resistance (HOMA-IR). The correlation was performed using the Pearson analysis.

Results

The increased serum levels of AFM and SERPINB1 were revealed in GDM patients as compared with non-GDM women, accompanied by the lower NRG4 serum level. ROCs for AFM concentrations showed an AUC of 0.629 (95% CI: 0.527∼0.731), 0.832 (95% CI: 0.754∼0.909) for the SERPINB1 serum level, and 0.626 (95% CI: 0.524∼0.728) for the NRG4 serum level. The threshold was 108.05 mg/L, 8.75 ng/mL, and 96.25 ng/mL of AFM, SERPINB1, and NRG4. Moreover, the combined ROC of AFM, SERPINB1, and NRG4 serum levels showed higher sensitivity (72.41%) and specificity (85.00%) for the diagnosis of GDM (AUC = 0.839; 95% CI: 0.764∼0.913). In GDM patients, the Pearson analysis revealed a significant correlation between AFM and SERPINB1 (r = 0.776), AFM and NRG4 (r = -0.799), as well as SERPINB1 and NRG4 (r = -0.783). Moreover, AFM and SERPINB1 serum concentrations in GDM patients were positively related to insulin levels, fasting glucose levels, and HOMA-IR values. However, the SERPINB1 serum level was negatively correlated with serum insulin and glucose levels and HOMA-IR.

Conclusion

Abnormal serum levels of NRG4, AFM, and SERPINB1, as highly sensitive diagnostic tools, are closely related to insulin resistance in GDM patients.

Serum Metabolomics and Proteomics to Study the Antihypertensive Effect of Protein Extracts from Tenebrio molitor

Hypertension is the leading risk factor for premature death worldwide and significantly contributes to the development of all major cardiovascular disease events. The management of high blood pressure includes lifestyle changes and treatment with antihypertensive drugs. Recently, it was demonstrated that a diet supplemented with Tenebrio molitor (TM) extracts is useful in the management of numerous pathologies, including hypertension. This study is aimed at unveiling the underlying mechanism and the molecular targets of intervention of TM dietary supplementation in hypertension treatment by means of proteomics and metabolomics techniques based on liquid chromatography coupled with high-resolution mass spectrometry. We demonstrate that serum proteome and metabolome of spontaneously hypertensive rats are severely altered with respect to their normotensive counterparts. Additionally, our results reveal that a diet enriched with TM extracts restores the expression of 15 metabolites and 17 proteins mainly involved in biological pathways associated with blood pressure maintenance, such as the renin–angiotensin and kallikrein–kinin systems, serin protease inhibitors, reactive oxygen scavenging, and lipid peroxidation. This study provides novel insights into the molecular pathways that may underlie the beneficial effects of TM, thus corroborating that TM could be proposed as a helpful functional food supplement in the treatment of hypertension.

Diagnostic circulating biomarkers to detect vision-threatening diabetic retinopathy: Potential screening tool of the future?

With the increasing prevalence of diabetes in developing and developed countries, the socio-economic burden of diabetic retinopathy (DR), the leading complication of diabetes, is growing. Diabetic retinopathy (DR) is currently one of the leading causes of blindness in working-age adults worldwide. Robust methodologies exist to detect and monitor DR; however, these rely on specialist imaging techniques and qualified practitioners. This makes detecting and monitoring DR expensive and time-consuming, which is particularly problematic in developing countries where many patients will be remote and have little contact with specialist medical centres. Diabetic retinopathy (DR) is largely asymptomatic until late in the pathology. Therefore, early identification and stratification of vision-threatening DR (VTDR) is highly desirable and will ameliorate the global impact of this disease. A simple, reliable and more cost-effective test would greatly assist in decreasing the burden of DR around the world. Here, we evaluate and review data on circulating protein biomarkers, which have been verified in the context of DR. We also discuss the challenges and developments necessary to translate these promising data into clinically useful assays, to detect VTDR, and their potential integration into simple point-of-care testing devices.

Afamin Levels and Their Correlation with Oxidative and Lipid Parameters in Non-diabetic, Obese Patients

Background: Afamin is a liver-produced bioactive protein and features α- and γ-tocopherol binding sites. Afamin levels are elevated in metabolic syndrome and obesity and correlate well with components of metabolic syndrome. Afamin concentrations, correlations between afamin and vitamin E, afamin and lipoprotein subfractions in non-diabetic, obese patients have not been fully examined. Methods: Fifty non-diabetic, morbidly obese patients and thirty-two healthy, normal-weight individuals were involved in our study. The afamin concentrations were measured by ELISA. Lipoprotein subfractions were determined with gel electrophoresis. Gas chromatography–mass spectrometry was used to measure α- and γ tocopherol levels. Results: Afamin concentrations were significantly higher in the obese patients compared to the healthy control (70.4 ± 12.8 vs. 47.6 ± 8.5 μg/mL, p < 0.001). Positive correlations were found between afamin and fasting glucose, HbA1c, hsCRP, triglyceride, and oxidized LDL level, as well as the amount and ratio of small HDL subfractions. Negative correlations were observed between afamin and mean LDL size, as well as the amount and ratio of large HDL subfractions. After multiple regression analysis, HbA1c levels and small HDL turned out to be independent predictors of afamin. Conclusions: Afamin may be involved in the development of obesity-related oxidative stress via the development of insulin resistance and not by affecting α- and γ-tocopherol levels.

Functional and Molecular Characters of Cancer Stem Cells Through Development to Establishment

Cancer stem cells (CSCs) are small subpopulation sharing similar properties like normal stem such as self-renewal and differentiation potential to direct tumor growth. Last few years, scientists considered CSCs as the cause of phenotypic heterogeneity in diverse cancer types. Also, CSCs contribute to cancer metastasis and recurrence. The cellular and molecular regulators influence on the CSCs' phenotype changing their behaviors in different stages of cancer progression. CSC markers play significance roles in cancer diagnosis and characterization. We delineate the cross-talks between CSCs and the tumor microenvironment that supports their intrinsic properties including survival, stemness, quiescence and their cellular and molecular adaptation. An insight into the markers of CSCs specific to organs is described.

Integrative Role of Albumin: Evolutionary, Biochemical and Pathophysiological Aspects

Being one of the main proteins in the human body and many animal species, albumin plays a crucial role in the transport of various ions, electrically neutral molecules and in maintaining the colloidal osmotic pressure of the blood. Albumin is able to bind almost all known drugs, many nutraceuticals and toxic substances, determining their pharmaco- and toxicokinetics. However, albumin is not only the passive but also the active participant of the pharmacokinetic and toxicokinetic processes possessing a number of enzymatic activities. Due to the thiol group of Cys34, albumin can serve as a trap for reactive oxygen and nitrogen species, thus participating in redox processes. The interaction of the protein with blood cells, blood vessels, and also with tissue cells outside the vascular bed is of great importance. The interaction of albumin with endothelial glycocalyx and vascular endothelial cells largely determines its integrative role. This review provides information of a historical nature, information on evolutionary changes, inflammatory and antioxidant properties of albumin, on its structural and functional modifications and their significance in the pathogenesis of some diseases.

Afamin predicts the prevalence and incidence of nonalcoholic fatty liver disease

OBJECTIVES

In the general population, increased afamin concentrations are associated with the prevalence and incidence of metabolic syndrome as well as type 2 diabetes. Although metabolic syndrome is commonly associated with nonalcoholic fatty liver disease (NAFLD), there exist no information on afamin and NAFLD.

METHODS

Afamin concentrations were cross-sectionally measured in 146 Austrian patients with NAFLD, in 45 patients without NAFLD, and in 292 age- and sex-matched healthy controls. Furthermore, the feasibility of afamin to predict incident NAFLD was evaluated in 1,434 adult participants in the population-based Cardiovascular Risk in Young Finns Study during a 10-year follow-up.

RESULTS

Median afamin concentrations were significantly higher in NAFLD patients (83.6 mg/L) than in patients without NAFLD (61.6 mg/L, p<0.0001) or in healthy controls (63.9 mg/L, p<0.0001). In age- and sex-adjusted logistic regression analyses a 10 mg/L increase of afamin was associated with a 1.5-fold increase of having NAFLD as compared with patients without NAFLD and the risk was even two-fold when compared with healthy controls. In the population-based cohort, afamin concentrations at baseline were significantly lower in participants without NAFLD (n=1,195) than in 239 participants who developed NAFLD (56.5 vs. 66.9 mg/L, p<0.0001) during the 10-year follow up, with highest afamin values observed in individuals developing severe forms of NAFLD. After adjustment for several potentially confounding parameters, afamin remained an independent predictor for the development of NAFLD (OR=1.37 [95% CI 1.23-1.54] per 10 mg/L increase, p<0.0001).

CONCLUSIONS

Afamin concentrations are increased in patients with NAFLD and independently predict the development of NAFLD in a population-based cohort.

Absorption, transportation, and distribution of vitamin E homologs

Vitamin E has eight different naturally occurring forms: four tocopherols and four tocotrienols. Because α-tocopherol has three asymmetric carbons, both natural α-tocopherol (RRR-α-tocopherol) and synthetic α-tocopherol (all-rac-α-tocopherol) are utilized in both pharmaceutical products and food additives. Therefore, determining the distribution of vitamin E in the body is very important. With regard to absorption, and transportation of vitamin E, it is suggested that the pathways mediated by three proteins (CD36, SR-BI, and NPC1L1) as well as passive diffusion affect absorption of vitamin E. Vitamin E homologs are mainly transported by very low-density lipoprotein (VLDL) with the α-tocopherol being recognized by the α-tocopherol transfer protein in liver. However, it is also suggested that chylomicrons (CMs) and high-density lipoprotein (HDL) are involved in transportation of vitamin E homologs from the small intestine to each section of peripheral tissue. In particular, it is speculated that vitamin E homologs transportation by CMs and HDL from enterocytes to peripheral tissues such as adipose tissue greatly affects the distribution of vitamin E homologs, excluding α-tocopherol. However, how lipoprotein lipase affects the incorporation of vitamin E homologs containing lipoprotein into peripheral tissues is unclear. Whether there is biodiscrimination when vitamin E homologs are incorporated into peripheral tissues from lipoprotein is an interesting question. It is likely that future research will reveal how individual vitamin E homologs are incorporated into peripheral tissue, especially the brain, adipose tissue, and skin.

Serum Albumin in Health and Disease: Esterase, Antioxidant, Transporting and Signaling Properties

Being one of the main proteins in the human body and many animal species, albumin plays a decisive role in the transport of various ions-electrically neutral and charged molecules-and in maintaining the colloidal osmotic pressure of the blood. Albumin is able to bind to almost all known drugs, as well as many nutraceuticals and toxic substances, largely determining their pharmaco- and toxicokinetics. Albumin of humans and respective representatives in cattle and rodents have their own structural features that determine species differences in functional properties. However, albumin is not only passive, but also an active participant of pharmacokinetic and toxicokinetic processes, possessing a number of enzymatic activities. Numerous experiments have shown esterase or pseudoesterase activity of albumin towards a number of endogeneous and exogeneous esters. Due to the free thiol group of Cys34, albumin can serve as a trap for reactive oxygen and nitrogen species, thus participating in redox processes. Glycated albumin makes a significant contribution to the pathogenesis of diabetes and other diseases. The interaction of albumin with blood cells, blood vessels and tissue cells outside the vascular bed is of great importance. Interactions with endothelial glycocalyx and vascular endothelial cells largely determine the integrative role of albumin. This review considers the esterase, antioxidant, transporting and signaling properties of albumin, as well as its structural and functional modifications and their significance in the pathogenesis of certain diseases.

Novel metabolic marker Afamin: A predictive factor for Large-for-Gestational-Age (LGA) fetus estimation in pregnancies with gestational diabetes mellitus?

OBJECTIVE

Gestational diabetes mellitus (GDM) affects both maternal and fetal/infant outcomes during and after pregnancy. The reason for the high incidence of large-for-gestational-age (LGA) infants in GDM patients despite close monitorization of glucose levels with early detection of the disease remains unclear to date. Our study aims to investigate the levels of the third-trimester novel marker afamin in GDM versus non-GDM pregnancies in terms of glycemic control status and their utility in the prediction of LGA fetuses.

MATERIAL AND METHODS

This prospective case-control study analysis involved 49 pregnant women with GDM diagnosed using the 75-g oral glucose tolerance test (75-g OGTT) and 40 randomly selected women with a similar body mass index (BMI) and gestational age (GA). Blood samples were collected in the third trimester of pregnancy. The afamin level was determined using a human afamin ELISA kit according to the manufacturer's procedure.

RESULTS

There was no significant difference found in BMI or GA of patients. Third-trimester afamin levels were 93.91 mg/L and 83.87 mg/L in the GDM and non-GDM groups, respectively (p=0.625). Afamin values of patients were not correlated with age, BMI, GA, HgA1c, 75-g OGTT fasting and 75-g OGTT 1-hour, or 75-g OGTT 2-hour values (p>0.05). GDM patients with LGA fetuses had significantly higher afamin values than patients with appropriate-for-gestational-age (AGA) fetuses (120.8 mg/L versus 91.26 mg/L, respectively). Between GDM patients with either LGA or AGA fetuses, there was no statistically significant difference found for age, BMI, GAs, insulin dose, 75-g OGTT results, or HgA1c values.

CONCLUSION

Our findings conclude that novel marker afamin levels could predict the risk of LGA infants independently of glycemic control status and provide insight into the pathogenesis of LGA fetuses, thus helping to reduce the risk of associated complications.

The Physiological Roles of Vitamin E and Hypovitaminosis E in the Transition Period of High-Yielding Dairy Cows

Simple Summary

In high-yield cows, most production diseases occur during transition periods. Alpha-tocopherol, the most biologically active form of vitamin E, declines in blood and reaches the lowest levels (hypovitaminosis E) around calving. Hypovitaminosis E is associated with the incidence of peripartum diseases. Therefore, many studies which have been published for more than 30 years have investigated the effects of α-tocopherol supplementation. This α-tocopherol deficiency was thought to be caused by complex factors. However, until recently, the physiological factors or pathways underlying hypovitaminosis E in the transition period have been poorly understood. In the last 10 years, the α-tocopherol-related genes expression, which regulate the metabolism, transportation, and tissue distribution of α-tocopherol in humans and rodents, has been reported in ruminant tissues. In this paper, we discuss at least six physiological phenomena that occur during the transition period and may be candidate factors predisposing to a decreased blood α-tocopherol level and hypovitaminosis E with changes in α-tocopherol-related genes expression.

Abstract

Levels of alpha-tocopherol (α-Toc) decline gradually in blood throughout prepartum, reaching lowest levels (hypovitaminosis E) around calving. Despite numerous reports about the disease risk in hypovitaminosis E and the effect of α-Toc supplementation on the health of transition dairy cows, its risk and supplemental effects are controversial. Here, we present some novel data about the disease risk of hypovitaminosis E and the effects of α-Toc supplementation in transition dairy cows. These data strongly demonstrate that hypovitaminosis E is a risk factor for the occurrence of peripartum disease. Furthermore, a study on the effectiveness of using serum vitamin levels as biomarkers to predict disease in dairy cows was reported, and a rapid field test for measuring vitamin levels was developed. By contrast, evidence for how hypovitaminosis E occurred during the transition period was scarce until the 2010s. Pioneering studies conducted with humans and rodents have identified and characterised some α-Toc-related proteins, molecular players involved in α-Toc regulation followed by a study in ruminants from the 2010s. Based on recent literature, the six physiological factors: (1) the decline in α-Toc intake from the close-up period; (2) changes in the digestive and absorptive functions of α-Toc; (3) the decline in plasma high-density lipoprotein as an α-Toc carrier; (4) increasing oxidative stress and consumption of α-Toc; (5) decreasing hepatic α-Toc transfer to circulation; and (6) increasing mammary α-Toc transfer from blood to colostrum, may be involved in α-Toc deficiency during the transition period. However, the mechanisms and pathways are poorly understood, and further studies are needed to understand the physiological role of α-Toc-related molecules in cattle. Understanding the molecular mechanisms underlying hypovitaminosis E will contribute to the prevention of peripartum disease and high performance in dairy cows.

Proteomics and metabolomics of HIV-associated neurocognitive disorders: A systematic review

HIV-associated neurocognitive disorders (HAND) are common features of the effect of human immunodeficiency virus (HIV)-1 within the central nervous system (CNS). The underlying neuropathophysiology of HAND is incompletely known. Furthermore, there are no markers to effectively predict or stratify the risk of HAND. Recent advancements in the fields of proteomics and metabolomics have shown promise in addressing these concerns, however, it is not clear if these approaches may provide new insight into pathways and markers related to HAND. We therefore conducted a systematic review of studies using proteomic and/or metabolomic approaches in the aim of identifying pathways or markers associated with neurocognitive impairment in people living with HIV (PLWH). Thirteen studies were eligible, including 11 proteomic and 2 metabolomic investigations of HIV-positive clinical samples (cerebrospinal fluid (CSF), brain tissue, and serum). Across varying profiling techniques and sample types, the majority of studies found an association of markers with neurocognitive function in PLWH. These included metabolic marker myo-inositol and proteomic markers superoxide dismutase, gelsolin, afamin, sphingomyelin, and ceramide. Certain markers were found to be dysregulated across various sample types. Afamin and gelsolin overlapped in studies of blood and CSF and sphingomyelin and ceramide overlapped in studies of CSF and brain tissue. The association of these markers with neurocognitive functioning may indicate the activity of certain pathways, potentially those related to the underlying neuropathophysiology of HAND.

Seminal Plasma and Serum Afamin Levels Are Associated with Infertility in Men with Oligoasthenoteratozoospermia

The plasma glycoprotein afamin has been previously identified as an alternative carrier protein for vitamin E in extravascular fluids such as plasma and cerebrospinal, ovarian follicular, and seminal fluids. However, to date, no study has established a relationship between afamin levels and infertility in women or men. The purposes of our study were (i) to assess the level of afamin in serum and seminal fluids in infertile men compared to healthy controls and (ii) to study the association between polymorphisms in afamin genes and male infertility. This observational, prospective study evaluated the afamin levels in serum and seminal fluids from infertile men (n = 39) and compared them to those in healthy controls (n = 30). We studied the association between single-nucleotide polymorphisms (SNPs) in the 5`-untranslated region (5`-UTR) of the afamin gene and infertility and analyzed a total of 1000 base pairs from the untranslated region of the afamin gene. Subjects with low sperm motility and low sperm concentration had higher median seminal afamin (18.9 ± 2.9 ng/mg of proteins) and serum afamin concentrations (24.1 ± 4.0 ng/mg of proteins) than subjects with normal sperm parameters (10.6 ± 1.4 ng/mg of proteins) (p < 0.02) (15.6 ± 1.4 ng/mg of proteins) (p < 0.002). A total of five different polymorphisms were found, including one deletion and four single-nucleotide polymorphisms (SNPs). A new transversion (A/T) (position 4:73481093) was identified in an oligoasthenoteratozoospermic patient and was associated with high levels of afamin in plasma and seminal fluids. The prevalence of this variant in our study in the case homozygous for TT is 0.985 (98.5%), and in the case heterozygous for TA is 0.015 (1.5%). Our results suggest that genetic variations in afamin might be associated with male infertility. These findings could significantly enhance our understanding of the molecular genetic causes of infertility.

Serum Afamin a Novel Marker of Increased Hepatic Lipid Content

AIM

Afamin is a liver-produced glycoprotein, a potential early marker of metabolic syndrome. Here we investigated regulation of afamin in a course of the metabolic disease development and in response to 3-month exercise intervention.

METHODS

We measured whole-body insulin sensitivity (euglycemic hyperinsulinemic clamp), glucose tolerance, abdominal adiposity, hepatic lipid content (magnetic resonance imaging/spectroscopy), habitual physical activity (accelerometers) and serum afamin (enzyme-linked immunosorbent assay) in 71 middle-aged men with obesity, prediabetes and newly diagnosed type 2 diabetes. Effects of 3-month exercise were investigated in 22 overweight-to-obese middle-aged individuals (16M/6F).

RESULTS

Prediabetes and type 2 diabetes, but not obesity, were associated with increased serum afamin (p<0.001). Afamin correlated positively with hepatic lipids, fatty liver index and liver damage markers; with parameters of adiposity (waist circumference, %body fat, adipocyte diameter) and insulin resistance (fasting insulin, C-peptide, HOMA-IR; p<0.001 all). Moreover, afamin negatively correlated with whole-body insulin sensitivity (M-value/Insulin, p<0.001). Hepatic lipids and fasting insulinemia were the most important predictors of serum afamin, explaining >63% of its variability. Exercise-related changes in afamin were paralleled by reciprocal changes in insulinemia, insulin resistance and visceral adiposity. No significant change in hepatic lipid content was observed.

CONCLUSIONS

Subjects with prediabetes and type 2 diabetes had the highest serum afamin levels. Afamin was more tightly related to hepatic lipid accumulation, liver damage and insulin resistance than to obesity.

Is afamin a potential early biomarker for subsequent development of preeclampsia? A nested case-control study

OBJECTIVE

The objective of this study is to determine if the second-trimester serum afamin is a reasonable predictor of preeclampsia (PE).

METHODS

In this nested case-control study, all pregnant women were screened by second-trimester screening test between 15 and 20 weeks of gestation and serum samples were collected and stored at -80 °C for biochemical analysis. All available stored samples from pregnant women who subsequently developed PE were thawed and the concentrations of afamin in the serum were measured. Control cases, chosen randomly from the same cohort whose blood was collected and stored in the same period as with the study group, who did not develop PE. Afamin levels were expressed ng/mL. Logistic regression was used to calculate adjusted odds ratio (aORs) for the prediction of PE.

RESULTS

A total of 39 women with PE and 46 controls were studied. Afamin levels were found to be significantly higher during the second trimester in women who developed PE compared to the control group. Afamin, at a cut-off level of 96.2 ng/mL, the aORs for PE was 28.6 (95% CI: 7.458-110.193). After adjustment for BMI, age, smoking, the aORs for PE was 65.6 (95% CI: 11.6-371.4; p = .001).

CONCLUSION

High levels of afamin in the early weeks of gestation in patients going on to develop PE later may be promising as a potential marker to predict PE in the first and second trimesters.

Plasma proteome atlas for differentiating tumor stage and post-surgical prognosis of hepatocellular carcinoma and cholangiocarcinoma

Although mass spectrometry-based plasma proteomics enables sensitive and large-scale discovery and validation of biomarkers for various diseases, its integrative application to hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) is not well investigated. Therefore, we analyzed albumin- and immunoglobulin G-depleted plasma samples from 148 and 60 patients with HCC and CCA, respectively, using liquid chromatography-tandem mass spectrometry. The algorithm used to measure the content of each protein was the percentage of exponentially modified protein abundance index. From 5320 proteins assayed in plasma, 53 and 25 biomarker candidates were identified for HCC and CCA, respectively. The abundance of six and two HCC markers particularly protruded in stage II and III, respectively, whereas plasma serine protease inhibitor was the sole marker the level of which steadily decreased with CCA progression. From a prognostic facet, we showed candidate markers and their cutoff levels for evaluating probability of tumor recurrence and patient survival period. Combination Kaplan-Meier models showed that HCC stage III or IV and both the content of alpha-2-HS-glycoprotein and apolipoprotein CIII <0.2% exhibited the poorest post-surgical recurrence-free and overall survivals. Furthermore, the content of afamin ≥0.2% played a significant role on the poor prognosis in patients with CCA. Our findings, taken together, characterized novel plasma biomarker signatures in dissecting tumor stages and post-surgical outcomes of HCC and CCA.

Macrocyclic peptides that inhibit Wnt signalling via interaction with Wnt3a

Here we report de novo macrocyclic peptide binders to Wnt3a, a member of the Wnt protein family. By means of the Random non-standard Peptides Integrated Discovery (RaPID) system, we have performed in vitro selection against the complex of mouse Wnt3a (mWnt3a) with human afamin (hAFM) to discover macrocyclic peptides that bind mWnt3a with K _D values as tight as 110 nM. One of these peptides, WAp-D04 (Wnt-AFM-peptide-D04), was able to inhibit the receptor-mediated signaling process, which was demonstrated in a Wnt3a-dependent reporter cell-line. Based on this initial hit, we applied a block-mutagenesis scanning display to identify a mutant inhibitor, WAp-D04-W10P, with 5-fold greater potency in a reporter assay. This work represents the first instance of molecules capable of inhibiting Wnt signaling through direct interaction with a Wnt protein, a molecular class for which targeting has been challenging due its highly hydrophobic nature.

Study the immunomodulation of anthracenedione in striped dwarf catfish, Mystus vittatus against pathogenic bacteria, Aeromonas hydrophila

Anthracenedione is a derivative of anthraquinone aromatic organic natural pigments found in senna, aloe latex, rhubarb, cascara, lichens, and fungi having broad range of bioactivity, including anti-cancer, anti-inflammatory, anti-microbial, anti-fungal, anti-oxidant, anti-viral activities suggesting potential for clinical purpose of many diseases. The effect of anthracenedione enriched diet on growth, hematology, innate and adaptive immune parameters as well as protection from Aeromonas hydrophila in Mystus vittatus was reported. The weight gain, feed intake, specific growth rate (SGR), and feed conversion ratio (FCR) were significantly increased in uninfected groups fed with 5 mg kg^-1 diet. The red blood cells (RBC) and white blood cells (WBC) count and the percentage of lymphocytes were significantly augmented in both infected and uninfected groups feeding with any diet. The percentage of monocytes, eosinophils, neutrophils and the biochemical profile such as total protein, albumin, and globulin also were significantly increased in the infected and uninfected groups fed with 5 mg kg^-1 enriched diet. The innate and adaptive immune parameters such as phagocytic activity, immunoglobulin M (IgM), respiratory burst activity, complement activity, and lysozyme activity were significantly increased in uninfected and infected groups fed with 5 or 10 mg kg^-1 diets but not with 1 mg kg^-1 diet. The serum superoxide dismutase (SOD) activity is significantly increased in the uninfected and infected fish fed with 5 mg kg^-1 diet but the increase was not significantly observed in 1 or 10 mg kg^-1 diets. The nitric oxide (NO) production is significantly elevated in both uninfected and infected groups fed with 5 mg kg^-1 diet. On the other hand, the lymphocyte proliferation and myeloperoxidase (MPO) activity were significantly increased the infected and uninfected groups fed with 5 and 10 mg kg^-1 diets. The cumulative mortality was found 5% with 1 and 5 mg kg^-1 diet groups while it was observed 10% mortality with 10 mg kg^-1 diet group. Based on the results, it is observed that feeding the uninfected and infected groups with 5 mg kg^-1 anthracenedione diet resulted in better improvement of growth, hematological, biochemical, and innate as well as adaptive immune parameters in M. vittatus against A. hydrophila.

Assessment of Serum Concentrations of Adropin, Afamin, and Neudesin in Children with Type 1 Diabetes

Introduction

The increasing knowledge of adropin, afamin, and neudesin and the regulation of glucose metabolism and insulin resistance allows for the assessment of the differences in their concentrations between the groups with varied duration of diabetes mellitus (DM).

Aim of the Study

Assessment of serum levels of adropin, afamin, and neudesin in children with type 1 diabetes, with respect to the disease duration.

Materials and Methods

The study consisted of 138 patients aged 5–18 years (M 40.58%). Children with type 1 diabetes (n = 68) were compared to the control group (n = 70). The diabetic group was divided into 4 subgroups: (I) newly diagnosed patients, after an episode of ketoacidosis (n = 14), (II) duration no longer than 5 years (n = 18), (III) 5 to 10 years (n = 27), and (IV) longer than 10 years (n = 9). Serum concentrations of adropin, afamin, and neudesin were assessed and compared between the groups of patients. The criterion for statistical significance was p < 0.05.

Results

The concentrations of adropin and afamin across all subgroups were lower than that in the control group, while neudesin levels were higher in diabetic patients compared to the control group. The differences were statistically significant.

Conclusions

Adropin, afamin, and neudesin may play a major role in the regulation of glucose metabolism and have a significant potential as novel biomarkers to predict future metabolic disorders. However, further multicentre studies on a larger cohort of patients are necessary to specify the role of these substances in the course and treatment of type 1 diabetes.

Identification of ApoA4 as a sphingosine 1-phosphate chaperone in ApoM- and albumin-deficient mice

HDL-bound ApoM and albumin are protein chaperones for the circulating bioactive lipid, sphingosine 1-phosphate (S1P); in this role, they support essential extracellular S1P signaling functions in the vascular and immune systems. We previously showed that ApoM- and albumin-bound S1P exhibit differences in receptor activation and biological functions. Whether the physiological functions of S1P require chaperones is not clear. We examined ApoM-deficient, albumin-deficient, and double-KO (DKO) mice for circulatory S1P and its biological functions. In albumin-deficient mice, ApoM was upregulated, thus enabling S1P functions in embryonic development and postnatal adult life. The Apom:Alb DKO mice reproduced, were viable, and exhibited largely normal vascular and immune functions, which suggested sufficient extracellular S1P signaling. However, Apom:Alb DKO mice had reduced levels (∼25%) of plasma S1P, suggesting that novel S1P chaperones exist to mediate S1P functions. In this study, we report the identification of ApoA4 as a novel S1P binding protein. Recombinant ApoA4 bound to S1P, activated multiple S1P receptors, and promoted vascular endothelial barrier function, all reflective of its function as a S1P chaperone in the absence of ApoM and albumin. We suggest that multiple S1P chaperones evolved to support complex and essential extracellular signaling functions of this lysolipid mediator in a redundant manner.

Afamin predicts gestational diabetes in polycystic ovary syndrome patients preconceptionally

BACKGROUND

Patients suffering from polycystic ovary syndrome (PCOS) are often insulin resistant and at elevated risk for developing gestational diabetes mellitus (GDM). The aim of this study was to explore afamin, which can be determined preconceptionally to indicate patients who will subsequently develop GDM. Serum concentrations of afamin are altered in conditions of oxidative stress like insulin resistance (IR) and correlate with the gold standard of IR determination, the HOMA index.

METHODS

Afamin serum concentrations and the HOMA index were analyzed post hoc in 63 PCOS patients with live births. Patients were treated at Essen University Hospital, Germany, between 2009 and 2018. Mann-Whitney U test, T test, Spearman's correlation, linear regression models and receiver-operating characteristic (ROC) analyses were performed for statistical analysis.

RESULTS

Patients who developed GDM showed significantly higher HOMA and serum afamin values before their pregnancy (P < 0.001, respectively). ROCs for afamin concentrations showed an area under the curve of 0.78 (95% confidence interval (CI) 0.65-0.90) and of 0.77 (95% CI 0.64-0.89) for the HOMA index. An afamin threshold of 88.6 mg/L distinguished between women who will develop GDM and those who will not with a sensitivity of 79.3% and a specificity of 79.4%. A HOMA index of 2.5 showed a sensitivity of 65.5% and a specificity of 88.2%.

CONCLUSION

The HOMA index and its surrogate parameter afamin are able to identify pre-pregnant PCOS patients who are at risk to develop GDM. Serum afamin concentrations are independent of fasting status and therefore an easily determinable biomarker.

Urinary afamin levels are associated with the progression of diabetic nephropathy

AIMS

In this study, we applied quantitative proteomic analysis to identify urinary proteins associated with diabetic nephropathy (DN).

METHODS

Two-dimensional image-converted analysis of liquid chromatography and mass spectrometry detected the proteins differentially excreted between normoalbuminuric and macroalbuminuric patients with type 2 diabetes mellitus (T2DM) (n = 6 each). Urinary levels of excreted proteins were measured by multiple reaction monitoring (MRM) analysis using an independent sample set (n = 77). Urinary afamin levels were measured by ELISA in T2DM and DN patients enrolled in this cohort study (n = 203).

RESULTS

One-hundred-four proteins displayed significant alterations in excretion. Nine of these candidates were validated by MRM analysis. Among them, the levels of afamin, CD44 antigen, and lysosome-associated membrane glycoprotein 2, which have not previously been implicated in DN, were significantly associated with both the urinary albumin to creatinine ratio (ACR) and eGFR. We further measured afamin levels in urine collected from T2DM patients who did not yet have significant kidney disease (ACR < 300 mg/g or eGFR change rate ≤ 3.3%/year). The urinary afamin to creatinine ratio (Afa/Cre) was significantly higher in patients who progressed to a more severe DN stage or had early renal decline than in patients who did not.

CONCLUSIONS

Afa/Cre was significantly increased in T2DM patients who subsequently developed DN. Afa/Cre may be useful to predict patients with T2DM at high risk of nephropathy before the development of macroalbuminuria or reduced kidney function, although further validation studies in a larger population are needed.

Urine afamin and afamin-creatinine ratio as biomarkers for kidney injury

AIM

The aim of this study was to evaluate the urine afamin (uAFM) and afamin-creatinine ratio (AfCR) levels in patients with glomerulonephritis.

PATIENTS & METHODS

We determined uAFM and AfCR of 247 healthy volunteers and 129 biopsy-proven glomerulonephritis patients.

RESULTS

Analytical evaluation study revealed the assay is a reliable and robust test for measuring uAFM. For reference intervals, uAFM and AfCR values were different significantly between males and females. uAFM and AfCR levels were significantly increased in patients with primary membranous nephropathy, IgA nephropathy and minimal change disease compared with healthy volunteers. uAFM and AfCR were positively correlated with urine albumin and albumin-creatinine ratio, respectively.

CONCLUSION

Our study suggested that uAFM and AfCR may be attractive biomarkers for kidney injury.

Afamin: an early predictor of preeclampsia

Purpose

Oxidative stress is involved in the pathogenesis of hypertensive disorders such as preeclampsia (PE) and associated with the human vitamin E-binding protein afamin. The aim of this study was, therefore, to analyse afamin in the first trimester of patients developing PE later in pregnancy and in control subjects without pregnancy complications.

Methods

In this retrospective study, 137 serum samples from the first trimester of pregnancy were analysed in a case–control study design. 39 patients developed PE (10 patients with early-onset and 29 patients with late onset disease) and 98 women had an uncomplicated pregnancy. Mann–Whitney U test, t test, logistic regression and ROC analyses were performed for statistical evaluation.

Results

Pregnant women developing PE presented with higher afamin concentrations in the first trimester [median 101.81 mg/L; interquartile range (IQR) 88.94–113.26] compared to subjects with uncomplicated pregnancy (median 86.40; IQR 75.26–96.92; p < 0.001). After adjusting for confounders, the odds ratio per afamin standard deviation was 1.60 (95% CI: 1.04–2.58; p = 0.04). An afamin threshold concentration of 87.8 mg/L exhibited the best sensitivity (79.5%) and specificity (57.1%) in predicting PE. Subgroup analysis of early- and late-onset disease resulted in substantially higher afamin concentrations in women with developing late-onset PE compared to controls (p < 0.001) with an odds ratio per afamin standard deviation of 1.62 (95% CI: 0.98–2.70; p = 0.06).

Conclusions

Serum afamin concentrations are elevated in the first trimester among patients developing PE compared to controls. Substantial differences were observed mainly among patients with late-onset PE.

Changes in serum afamin and vitamin E levels after selective LDL apheresis

BACKGROUND

Afamin is a plasma vitamin E-binding glycoprotein partially associated with ApoA1-containing high-density lipoprotein (HDL) subfractions. In a previous study, the serum vitamin E decreased after low-density lipoprotein (LDL) apheresis, while vitamin E/cholesterol ratio increased. We aimed to study the effect of LDL apheresis on serum afamin level.

METHODS

The serum level of afamin and oxidized LDL were measured by enzyme-linked immunosorbent assay in six severe heterozygous FH patients before and after their first LDL apheresis treatments and in seven healthy controls. We also investigated the changes in total cholesterol, LDL-C, HDL-C, ApoB, ApoA1, HDL subfractions, and α- and γ-tocopherol levels during the treatment. HDL subfractions were detected by an electrophoretic method on polyacrylamide gel (Lipoprint). Serum α- and γ-tocopherol levels were detected by gas chromatography-mass spectrometry.

RESULTS

The first treatment sessions decreased serum afamin levels by an average of 9.4%. Total cholesterol, LDL-C, HDL-C and ApoA1 levels decreased by 52.6; 61.8; 10.5; and 14.1%, respectively. We found that α- and γ-tocopherol levels markedly decreased (by 34.1 and 32.9%, respectively), while α- tocopherol/cholesterol and γ-tocopherol/cholesterol ratios significantly increased (by 41.4 and 40.3%, respectively). Oxidized LDL levels significantly decreased. There was a shift toward the larger HDL subfractions.

CONCLUSION

LDL apheresis moderately decreases the circulating levels of afamin parallel to lowering HDL-C and ApoA1 levels. Tocopherol levels decreases markedly compared to afamin levels, however, beneficial changes in vitamin E/cholesterol ratios, oxidized LDL levels and HDL subfraction distribution were detected. These additional effects of LDL apheresis may result in further cardiovascular risk reduction in FH patients.

Kaolin incorporated diet on growth and immune response in Ctenopharyngodon idellus against Aeromonas hydrophila

The effect of kaolin enriched diet on growth, hematology, and immune response in the grass carp Ctenopharyngodon idellus against Aeromonas hydrophila is reported. Both the infected and uninfected groups fed with kaolin enriched diet gained better weight, protein efficiency ratio (PER) and feed conversion ratio (FCR). The survival rate was 98.3% in control (C) and uninfected (UI) fed with 2 g kg^-1 kaolin diet, whereas it was 95.0% in uninfected (UI) fed with 1 g kg^-1 or infected (I) fed with 1 g kg^-1 kaolin diets. In both groups the red blood cell (RBC) and white blood cell (WBC) counts, percentage of lymphocytes and eosinophils, level of albumin and globulin increased in uninfected (UI) fed with 1, 2, and 3 g kg^-1 diets. The serum Ig level significantly increased in both groups when fed with 3 g kg^-1 diet, whereas the phagocytic activity did not increase significantly. Further the respiratory burst activity in both groups significantly increased with any supplemented diet. The serum superoxide dismutase (SOD) activity increased significantly in the infected group fed with 2 g kg^-1 diet and the uninfected group fed with 1 g kg^-1 diet. The complement activity was significantly enhanced in both groups when fed with 1 and 2 g kg^-1 diets; the lysozyme activity increased with 2 g kg^-1 diet; besides the group was 5% mortality whereas 10% mortality was observed when fed with 1 or 3 g kg^-1 diets. The present results suggest that C. idellus fed with kaolin enriched diet promotes growth, hematology, innate and adaptive immune response against Aeromonas hydrophila infection.

Is Afamin a novel biomarker for gestational diabetes mellitus? A pilot study

BACKGROUND

In search of potential early biomarkers for timely prediction of gestational diabetes mellitus (GDM), we focused on afamin, a vitamin E-binding protein in human plasma.. Afamin plays a role in anti-apoptotic cellular processes related to oxidative stress and is associated with insulin resistance and other features of metabolic syndrome. During uncomplicated pregnancy its serum concentrations increase linearly. The aim of this study was to investigate the suitability of afamin as early marker for predicting GDM.

METHODS

In a first-trimester cohort from a prospective observational study of adverse pregnancy outcomes we secondarily analyzed afamin concentrations in 59 patients diagnosed with GDM and 51 controls. Additionally, afamin concentrations were cross-sectionally examined in a mid-trimester cohort of 105 women and compared with results from a simultaneously performed oral glucose tolerance test (OGTT). Subgroup analysis comparing patients treated with either insulin (iGDM) or dietary intervention (dGDM) was performed in both cohorts. Patients were recruited at the University Hospital Essen, Germany, between 2003 and 2016.

RESULTS

Results were adjusted for body-mass-index (BMI) and gestational age. First and mid-trimester cohorts yielded significantly elevated afamin concentrations in patients with pathological OGTT compared to patients without GDM (first trimester cohort: mean, 113.4 mg/l; 95% CI, 106.4-120.5 mg/l and 87.2 mg/l; 95% CI, 79.7-94.7 mg/l; mid-trimester cohort: mean, 182.9 mg/l; 95% CI, 169.6-196.2 mg/l and 157.3 mg/l; 95% CI, 149.1-165.4 mg/l, respectively). In the first-trimester cohort, patients developing iGDM later in pregnancy presented with significantly higher afamin concentrations compared to patients developing dGDM and compared to patients without GDM. In the mid-trimester cohort, mean concentrations of afamin differed significantly between patients with dGDM compared to controls and between patients with iGDM and controls. Patients with iGDM showed only slightly higher afamin levels compared to patients with dGDM.

CONCLUSION

Afamin may serve as a new early biomarker for pathological glucose metabolism during pregnancy. Further research is needed to determine afamin's concentrations during pregnancy, its predictive value for early detection of pregnancies at high risk to develop GDM and its diagnostic role during the second trimester.

Expression, Purification, and Biochemical Characterization of Human Afamin

Afamin is an 87 kDa glycoprotein with five predicted N-glycosylation sites. Afamin's glycan abundance contributes to conformational and chemical inhomogeneity presenting great challenges for molecular structure determination. For the purpose of studying the structure of afamin, various forms of recombinantly expressed human afamin (rhAFM) with different glycosylation patterns were thus created. Wild-type rhAFM and various hypoglycosylated forms were expressed in CHO, CHO-Lec1, and HEK293T cells. Fully nonglycosylated rhAFM was obtained by transfection of point-mutated cDNA to delete all N-glycosylation sites of afamin. Wild-type and hypo/nonglycosylated rhAFM were purified from cell culture supernatants by immobilized metal ion affinity and size exclusion chromatography. Glycan analysis of purified proteins demonstrated differences in micro- and macro-heterogeneity of glycosylation enabling the comparison between hypoglycosylated, wild-type rhAFM, and native plasma afamin. Because antibody fragments can work as artificial chaperones by stabilizing the structure of proteins and consequently enhance the chance for successful crystallization, we incubated a Fab fragment of the monoclonal anti-afamin antibody N14 with human afamin and obtained a stoichiometric complex. Subsequent results showed sufficient expression of various partially or nonglycosylated forms of rhAFM in HEK293T and CHO cells and revealed that glycosylation is not necessary for expression and secretion.

Urine proteomics of primary membranous nephropathy using nanoscale liquid chromatography tandem mass spectrometry analysis

Background

Primary membranous nephropathy (PMN) is an important cause of nephrotic syndrome in adults. Urine proteome may provide important clues of pathophysiological mechanisms in PMN. In the current study, we analyzed and compared the proteome of urine from patients with PMN and normal controls.

Methods

We performed two technical replicates (TMT1 and TMT2) to analyze and compare the urine proteome from patients with PMN and normal controls by tandem mass tag (TMT) technology coupled with nanoscale liquid chromatography tandem mass spectrometry analysis (LC–MS/MS). Gene ontology (GO) enrichment analysis was performed to analyse general characterization of the proteins. The proteins were also matched against the database of Kyoto Encyclopedia of Genes and Genomes (KEGG). For validation, Western blot was used to analyze the selected proteins.

Results

A total of 509 proteins and 411 proteins were identified in TMT1 and TMT2, respectively. 249 proteins were both identified in two technical replicates. GO analysis and KEGG analysis revealed immunization and coagulation were predominantly involved. Among the differential protein, the overexcretion of alpha-1-antitrypsin (A1AT) and afamin (AFM) were validated by Western blot analysis.

Conclusions

Our data showed the important role of immunologic mechanism in the development of PMN, and the value of urinary A1AT and AFM in biomarker discovery of patients with PMN. The discovery of the overexcretion of A1AT and AFM in the urine can help to further elucidate pathogenetic mechanisms involved in PMN.

Electronic supplementary material

The online version of this article (10.1186/s12014-018-9183-3) contains supplementary material, which is available to authorized users.

Evolution of thyroid hormone distributor proteins

Thyroid hormones (THs) are evolutionarily old hormones, having effects on metabolism in bacteria, invertebrates and vertebrates. THs bind specific distributor proteins (THDPs) to ensure their efficient distribution through the blood and cerebrospinal fluid in vertebrates. Albumin is a THDP in the blood of all studied species of vertebrates, so may be the original vertebrate THDP. However, albumin has weak affinity for THs. Transthyretin (TTR) has been identified in the blood across different lineages in adults vs juveniles. TTR has intermediate affinity for THs. Thyroxine-binding globulin has only been identified in mammals and has high affinity for THs. Of these THDPs, TTR is the only one known to be synthesised in the brain and is involved in moving THs from the blood into the cerebrospinal fluid. We analysed the rates of evolution of these three THDPs: TTR has been most highly conserved and albumin has had the highest rate of divergence.

Plasma Concentrations of Afamin Are Associated With Prevalent and Incident Type 2 Diabetes: A Pooled Analysis in More Than 20,000 Individuals

OBJECTIVE

The human vitamin E-binding glycoprotein afamin is primarily expressed in the liver and has been associated with prevalent and incident metabolic syndrome. These data were in line with observations in transgenic mice. We thus investigated whether afamin concentrations are associated with prediabetes, type 2 diabetes, and insulin resistance (IR).

RESEARCH DESIGN AND METHODS

Individual-level baseline (n = 20,136) and follow-up data (n = 14,017) of eight prospective cohort studies were investigated. Study-level data were combined using random-effects meta-analyses. Main outcomes were prevalent and incident type 2 diabetes, prediabetes, and IR. Discrimination and reclassification of participants was analyzed for incident type 2 diabetes.

RESULTS

Mean afamin concentrations between studies ranged from 61 to 73 mg/L. The eight studies included 1,398 prevalent and 585 incident cases of type 2 diabetes. Each increase of afamin by 10 mg/L was associated with prevalent type 2 diabetes (odds ratio [OR] 1.19 [95% CI 1.12-1.26], P = 5.96 × 10^-8). Afamin was positively associated with IR assessed by HOMA-IR (β 0.110 [95% CI 0.089-0.132], P = 1.37 × 10^-23). Most importantly, afamin measured at baseline was an independent predictor for 585 incident cases of type 2 diabetes (OR 1.30 [95% CI 1.23-1.38], P = 3.53 × 10^-19) and showed a significant and valuable gain in risk classification accuracy when added to this extended adjustment model.

CONCLUSIONS

This pooled analysis in >20,000 individuals showed that afamin is strongly associated with IR, prevalence, and incidence of type 2 diabetes independent of major metabolic risk factors or parameters. Afamin might be a promising novel marker for the identification of individuals at high risk for the development of type 2 diabetes.

Detection of lithospermate B in rat plasma at the nanogram level by LC/MS in multi reaction monitoring mode

Low bioavailability and high binding affinity to plasma proteins led to the difficulty for the quantitative detection of lithospermate B (LSB) in plasma. This study aimed to develop a protocol for detecting LSB in plasma. A method was employed to quantitatively detect LSB of 5–500 ng/mL by LC/MS spectrometry in multi reaction monitoring mode via monitoring two major fragments with m/z values of 519 and 321 in the MS2 spectrum. To set up an adequate extraction solution to release LSB captured by plasma proteins, recovery yields of LSB extracted from rat plasma acidified by formic acid or HCl in the presence or absence of EDTA and caffeic acid were detected and compared using the above quantitative method. High recovery yield (~90%) was achieved when LSB (5–500 ng/mL) mixed in rat plasma was acidified by HCl (5 M) in the presence of EDTA (0.5 M) and caffeic acid (400 μg/mL). The lower limit of detection and the lower limit of quantification for LSB in the spiked plasma were calculated to be 1.8 and 5.4 ng/mL, respectively. Good accuracy (within ±10%) and precision (less than 10%) of intra- and inter-day quality controlled samples were observed. Oral bioavailability of LSB in rat model was detected via this optimized extraction method, and the maximum plasma concentration (C_max) was found to be 1034.3 ± 510.5 μg/L at t_max around 10 min, and the area under the plasma concentration–time curve (AUC) was 1414.1 ± 851.2 μg·h/L.

Genome-Wide Identification and Comparative Analysis of Albumin Family in Vertebrates

Albumins are the most well-known globular proteins, and the most typical representatives are the serum albumins. However, less attention was paid to the albumin family, except for the human and bovine serum albumin. To characterize the features of albumin family, we have mined all the putative albumin proteins from the available genome sequences. The results showed that albumin is widely distributed in vertebrates, but not present in the bacteria and archaea. The phylogenetic analysis of vertebrate albumin family implied an evolutionary relationship between members of serum albumin, α-fetoprotein, vitamin D–binding protein, and afamin. Meanwhile, a new member from the albumin family was found, namely, extracellular matrix protein 1. The structural analysis revealed that the motifs for forming the internal disulfide bonds are highly conserved in the albumin family, despite the low overall sequence identity across the family. The domain arrangement of albumin proteins indicated that most of vertebrate albumins contain 3 characteristic domains, arising from 2 evolutionary patterns. And a significant trend has been observed that the albumin proteins in higher vertebrate species tend to possess more characteristic domains. This study has provided the fundamental information required for achieving a better understanding of the albumin distribution, phylogenetic relationship, characteristic motif, structure, and new insights into the evolutionary pattern.

Afamin promotes glucose metabolism in papillary thyroid carcinoma

Circulating afamin (AFM) concentrations have been investigated as a tumor biomarker in various types of carcinomas. However, suitable cell lines expressing human afamin have not yet been reported and current knowledge of the functions of afamin, particularly at the mechanistic molecular level, is very limited. In the current study, thyroid cancer cell lines 8505c and K1 were used to investigate the potential functions of afamin. AFM over-expression models and vector controls of 8505c (8505c + AFM and 8505c + NC) and K1 (K1 + AFM and K1 + NC) were successfully established by Lenti-LV5-AFM and Lenti-LV5-NC transfection. The change of gene expression was detected by qRT-PCR and western blotting analysis. (18)F-FDG imaging in xenografts model was performed using a micro PET/CT. We found that protein level of GAPDH, GLUT1, HK2, p-AKT, AKT, p-mTOR and PARP1 were up-regulated in K1 + AFM cells when compared to K1 and K1 + NC. While in 8505c, 8505c + NC and 8505c cells, the expression level of these genes were not significantly changed. (18)F-FDG uptake was much higher in K1 + AFM cells when compared to K1 and K1 + NC in vitro and in vivo. In conclusion, afamin could promote glycometabolism by up-regulating the glucose metabolism key enzymes in papillary thyroid carcinoma. These findings reveal new clues of the molecular function of AFM.

Active and water-soluble form of lipidated Wnt protein is maintained by a serum glycoprotein afamin/α-albumin

Wnt plays important role during development and in various diseases. Because Wnts are lipidated and highly hydrophobic, they can only be purified in the presence of detergents, limiting their use in various in vitro and in vivo assays. We purified N-terminally tagged recombinant Wnt3a secreted from cells and accidentally discovered that Wnt3a co-purified with a glycoprotein afamin derived from the bovine serum included in the media. Wnt3a forms a 1:1 complex with afamin, which remains soluble in aqueous buffer after isolation, and can induce signaling in various cellular systems including the intestical stem cell growth assay. By co-expressing with afamin, biologically active afamin-Wnt complex can be easily obtained in large quantity. As afamin can also solubilize Wnt5a, Wnt3, and many more Wnt subtypes, afamin complexation will open a way to put various Wnt ligands and their signaling mechanisms under a thorough biochemical scrutiny that had been difficult for years.

DOI:http://dx.doi.org/10.7554/eLife.11621.001

The Wnt signaling pathway helps animal cells to communicate with each other to coordinate the formation of tissues and organs. The pathway relies on a protein called Wnt that is released from cells and binds to a receptor protein called Frizzled on the surface of other cells to trigger changes in gene activation. Defects in the Wnt signaling pathway contribute to cancer and other diseases.

Great progress has been made in understanding Wnt signaling, but certain types of experiments have been hindered because it has been difficult to isolate pure Wnt proteins. This is partly because Wnt proteins are attached to a fatty molecule that is important for their activity but also makes these proteins “hydrophobic,” or repelled by water.

Hydrophobic proteins have a strong tendency to clump or aggregate when they are isolated from cells, which reduces the biological activity of proteins. Adding detergents to the aggregates can break them apart, but can also hinder the proteins’ activities and cannot be used in all experiments. Previous research has shown that mammalian cells grown in the presence of blood serum can produce Wnt proteins that do not aggregate. Blood serum is a complex mixture of different molecules obtained from blood and is commonly added to cells grown in the laboratory. However, adding serum can have also undesirable effects and it is not understood why serum stops Wnt proteins forming aggregates.

Using biochemical methods, Mihara et al. have now identified the component in blood serum that prevents Wnt proteins from aggregating. The experiments showed that a protein in the blood serum called afamin binds tightly to Wnt proteins. Furthermore, the complex between afamin and Wnt was biologically active, and could bind to the Frizzled receptor and trigger an appropriate response in cells.

Mihara et al. then generated cells that produced both afamin and Wnt and used them to purify large amounts of biologically active Wnt/afamin complexes. This method avoids the potentially undesirable effects of using detergents or serum, and will therefore likely be useful for future experiments and therapeutic applications. Further work is also needed to understand why afamin binds to Wnt proteins and whether this is important for Wnt signaling.

DOI:http://dx.doi.org/10.7554/eLife.11621.002

Comparative studies on drug binding to the purified and pharmaceutical-grade human serum albumins: Bridging between basic research and clinical applications of albumin

Human serum albumin (HSA), the most abundant protein in blood plasma, is a monomeric multidomain protein that possesses an extraordinary capacity for binding, so that serves as a circulating depot for endogenous and exogenous compounds. During the heat sterilization process, the structure of pharmaceutical-grade HSA may change and some of its activities may be lost. In this study, to provide deeper insight on this issue, we investigated drug-binding and some physicochemical properties of purified albumin (PA) and pharmaceutical-grade albumin (PGA) using two known drugs (indomethacin and ibuprofen). PGA displayed significantly lower drug binding capacity compared to PA. Analysis of the quenching and thermodynamic parameters indicated that intermolecular interactions between the drugs and the proteins are different from each other. Surface hydrophobicity as well as the stability of PGA decreased compared to PA, also surface hydrophobicity of PA and PGA increased upon drugs binding. Also, kinetic analysis of pseudo-esterase activities indicated that Km and Vmax parameters for PGA enzymatic activity are more and less than those of PA, respectively. This in vitro study demonstrates that the specific drug binding of PGA is significantly reduced. Such studies can act as connecting bridge between basic research discoveries and clinical applications.

Afamin--A pleiotropic glycoprotein involved in various disease states

The human glycoprotein afamin was discovered as the fourth member of the albumin gene family. Despite intense research over the last 20 years, our knowledge of afamin's physiological or pathophysiological functions is still very limited. Circulating afamin is primarily of hepatic origin and abundant concentrations are found in plasma, cerebrospinal, ovarian follicular and seminal fluids. In vitro binding studies revealed specific binding properties for vitamin E. A previously performed analytical characterization and clinical evaluation study of an enzyme-linked immunosorbent assay for quantitative measurement of afamin in human plasma demonstrated that the afamin assay meets the quality specifications for laboratory medicine. Comparative proteomics has identified afamin as a potential biomarker for ovarian cancer and these findings were confirmed by quantitative immunoassay of afamin and validated in independent cohorts of patients with ovarian cancer. Afamin has also been investigated in other types of carcinoma. Most of these studies await further evaluation with validated quantitative afamin assays and require validation in larger patient cohorts. Transgenic mice overexpressing the human afamin gene revealed increased body weight and increased blood concentrations of lipids and glucose. These transgenic mouse data were in line with three large human population-based studies showing that afamin is strongly associated with the prevalence and development of the metabolic syndrome. This review summarizes and discusses the molecular, biochemical and analytical characterization of afamin as well as possible clinical applications of afamin measurement.