Fetuin-A in the developing brain

Influence of Adipokines on Metabolic Dysfunction and Aging

Currently, 30% of the global population is overweight or obese, with projections from the World Obesity Federation suggesting that this figure will surpass 50% by 2035. Adipose tissue dysfunction, a primary characteristic of obesity, is closely associated with an increased risk of metabolic abnormalities, such as hypertension, hyperglycemia, and dyslipidemia, collectively termed metabolic syndrome. In particular, visceral fat accretion is considered as a hallmark of aging and is strongly linked to higher mortality rates in humans. Adipokines, bioactive peptides secreted by adipose tissue, play crucial roles in regulating appetite, satiety, adiposity, and metabolic balance, thereby rendering them key players in alleviating metabolic diseases and potentially extending health span. In this review, we elucidated the role of adipokines in the development of obesity and related metabolic disorders while also exploring the potential of certain adipokines as candidates for longevity interventions.

Post-translational modifications glycosylation and phosphorylation of the major hepatic plasma protein fetuin-A are associated with CNS inflammation in children

Fetuin-A is a liver derived plasma protein showing highest serum concentrations in utero, preterm infants, and neonates. Fetuin-A is also present in cerebrospinal fluid (CSF). The origin of CSF fetuin-A, blood-derived via the blood-CSF barrier or synthesized intrathecally, is presently unclear. Fetuin-A prevents ectopic calcification by stabilizing calcium and phosphate as colloidal calciprotein particles mediating their transport and clearance. Thus, fetuin-A plays a suppressive role in inflammation. Fetuin-A is a negative acute-phase protein under investigation as a biomarker for multiple sclerosis (MS). Here we studied the association of pediatric inflammatory CNS diseases with fetuin-A glycosylation and phosphorylation. Paired blood and CSF samples from 66 children were included in the study. Concentration measurements were performed using a commercial human fetuin-A/AHSG ELISA. Of 60 pairs, 23 pairs were analyzed by SDS-PAGE following glycosidase digestion with PNGase-F and Sialidase-AU. Phosphorylation was analyzed in 43 pairs by Phos-TagTM acrylamide electrophoresis following alkaline phosphatase digestion. Mean serum and CSF fetuin-A levels were 0.30 ± 0.06 mg/ml and 0.644 ± 0.55 μg/ml, respectively. This study showed that serum fetuin-A levels decreased in inflammation corroborating its role as a negative acute-phase protein. Blood-CSF barrier disruption was associated with elevated fetuin-A in CSF. A strong positive correlation was found between the CSF fetuin-A/serum fetuin-A quotient and the CSF albumin/serum albumin quotient, suggesting predominantly transport across the blood-CSF barrier rather than intrathecal fetuin-A synthesis. Sialidase digestion showed increased asialofetuin-A levels in serum and CSF samples from children with neuroinflammatory diseases. Desialylation enhanced hepatic fetuin-A clearance via the asialoglycoprotein receptor thus rapidly reducing serum levels during inflammation. Phosphorylation of fetuin-A was more abundant in serum samples than in CSF, suggesting that phosphorylation may regulate fetuin-A influx into the CNS. These results may help establish Fetuin-A as a potential biomarker for neuroinflammatory diseases.

The structure, biosynthesis, and biological roles of fetuin-A: A review

Fetuin-A is a heterodimeric plasma glycoprotein containing an A-chain of 282 amino acids and a B-chain of 27 amino acid residues linked by a single inter-disulfide bond. It is predominantly expressed in embryonic cells and adult hepatocytes, and to a lesser extent in adipocytes and monocytes. Fetuin-A binds with a plethora of receptors and exhibits multifaceted physiological and pathological functions. It is involved in the regulation of calcium metabolism, osteogenesis, and the insulin signaling pathway. It also acts as an ectopic calcification inhibitor, protease inhibitor, inflammatory mediator, anti-inflammatory partner, atherogenic factor, and adipogenic factor, among other several moonlighting functions. Fetuin-A has also been demonstrated to play a crucial role in the pathogenesis of several disorders. This review mainly focuses on the structure, synthesis, and biological roles of fetuin-A. Information was gathered manually from various journals via electronic searches using PubMed, Google Scholar, HINARI, and Cochrane Library from inception to 2022. Studies written in English and cohort, case-control, cross-sectional, or experimental studies were considered in the review, otherwise excluded.

Could Fetuin-A Be a Biomarker for Autism Spectrum Disorder and Cognitive Developmental Delay?

Early detection of cognitive developmental delay (CDD) and autism spectrum disorder (ASD) is challenging, despite the numerous scientific studies conducted and different therapeutic strategies. Lack of a biomarker for autism is a limiting factor for early diagnosis, which could provide better outcome with early start of therapy. Because of the high serum fetuin-A concentration during intrauterine life, it has been suggested that fetuin-A may have a role in brain development. The current study sought to determine if fetuin-A, a multifunctional glycoprotein thought to have a role in brain development, may be used as a biomarker for the diagnosis of ASD and developmental delay. The study involved 55 children with cognitive developmental delays and 40 healthy children. Two categories of children with cognitive developmental delays were identified. The participants were subjected to a psychiatric assessment as well as developmental testing. Only 54.5% of the 55 individuals had CDD, whereas 45.5% had ASD. Using an ELISA kit, the levels of serum fetuin-A were determined spectrophotometrically. The serum fetuin-A levels in the patients from the test group were found to be significantly lower than in the healthy individuals (p < 0.001). The cutoff value for the serum fetuin-A levels for cognitive developmental delay and autism spectrum disorder was 518 µg/liter, according to the results of ROC analysis (84.6% sensitivity and 91.4% specificity, AUC: 0.95, p < 0.001). The findings suggest that the serum fetuin-A level may be used to diagnose autism spectrum disorder and cognitive developmental delays.

The possible link between Fetuin-A Protein and Neuro-inflammation in Children with Autism Spectrum Disorder

Objectives

To investigate the blood plasma levels of Fetuin-A protein in children with Autism Spectrum Disorder (ASD) and healthy controls that could offer novel diagnostic biomarkers of disease development in ASD. Another objective was to investigate the severity of autistic children by Childhood Autism Rating Scale (CARS) and Short Sensory Profile (SSP).

Methods

This case control study was carried out at Autism Research and Treatment (ART) Center, King Saud University, Riyadh, Saudi Arabia, from October 2019 to February 2020. Plasma concentration of Fetuin-A was analyzed by enzyme-linked immunosorbent assay (ELISA) in ASD subjects (n=46) and normal controls (n=44). Correlation among Fetuin-A levels, CARS and SSP was established by Spearman's correlation coefficient (r).

Results

Overall, autistic children had significantly (p= 0.0.02) lower Fetuin-A concentration [50.76 (22.2-68.5) ng/ml] than those of healthy controls [53.7 (35.6-99.7) ng/ml] [median (interquartile range)]. Children with mild to moderate autism (n=24, 52%) also showed significantly lower Fetuin-A levels [50.0 (30.0-68.2) ng/ml], (p =0.02} than healthy controls [53.7 (35.6-99.7) ng/ml] [median (IQR)]. However, there was no significant change (p = 0.71) observed between the Fetuin-A levels of children with severe autism [51.8 (22.2-68.5)] ng/ml, mild to moderate autism [50 (30-68.2)] ng/ml [median (IQR)] and healthy controls (p=0.12). Also no significant correlations between Fetuin-A, CARS and SSP were observed (CARS, r= 0.024, p=0.88; SSP, r= -0.003, p=0.98).

Conclusion

Overall the low Fetuin-A plasma values in ASD subjects, most likely show that Fetuin-A could be associated in the physiology of autism. Further studies with larger patient and control cohorts will be necessary to determine whether Fetuin-A can be used as a biomarker for ASD.

Phenotypic subgrouping and multi-omics analyses reveal reduced diazepam-binding inhibitor (DBI) protein levels in autism spectrum disorder with severe language impairment

BACKGROUND

The mechanisms underlying autism spectrum disorder (ASD) remain unclear, and clinical biomarkers are not yet available for ASD. Differences in dysregulated proteins in ASD have shown little reproducibility, which is partly due to ASD heterogeneity. Recent studies have demonstrated that subgrouping ASD cases based on clinical phenotypes is useful for identifying candidate genes that are dysregulated in ASD subgroups. However, this strategy has not been employed in proteome profiling analyses to identify ASD biomarker proteins for specific subgroups.

METHODS

We therefore conducted a cluster analysis of the Autism Diagnostic Interview-Revised (ADI-R) scores from 85 individuals with ASD to predict subgroups and subsequently identified dysregulated genes by reanalyzing the transcriptome profiles of individuals with ASD and unaffected individuals. Proteome profiling of lymphoblastoid cell lines from these individuals was performed via 2D-gel electrophoresis, and then mass spectrometry. Disrupted proteins were identified and compared to the dysregulated transcripts and reported dysregulated proteins from previous proteome studies. Biological functions were predicted using the Ingenuity Pathway Analysis (IPA) program. Selected proteins were also analyzed by Western blotting.

RESULTS

The cluster analysis of ADI-R data revealed four ASD subgroups, including ASD with severe language impairment, and transcriptome profiling identified dysregulated genes in each subgroup. Screening via proteome analysis revealed 82 altered proteins in the ASD subgroup with severe language impairment. Eighteen of these proteins were further identified by nano-LC-MS/MS. Among these proteins, fourteen were predicted by IPA to be associated with neurological functions and inflammation. Among these proteins, diazepam-binding inhibitor (DBI) protein was confirmed by Western blot analysis to be expressed at significantly decreased levels in the ASD subgroup with severe language impairment, and the DBI expression levels were correlated with the scores of several ADI-R items.

CONCLUSIONS

By subgrouping individuals with ASD based on clinical phenotypes, and then performing an integrated transcriptome-proteome analysis, we identified DBI as a novel candidate protein for ASD with severe language impairment. The mechanisms of this protein and its potential use as an ASD biomarker warrant further study.

Fetuin-A protein distribution in mature inflamed and ischemic brain tissue

Background

The liver-derived plasma protein fetuin-A is strongly expressed during fetal life, hence its name. Fetuin-A protein is normally present in most fetal organs and tissues, including brain tissue. Fetuin-A was neuroprotective in animal models of cerebral ischemia and lethal chronic inflammation, suggesting a role beyond the neonatal period. Little is known, however, on the presence of fetuin-A in mature human brain tissue under different physiological and pathological conditions.

Methods

We studied by immunohistochemistry (IHC) the distribution of fetuin-A protein in mature human brain autopsy tissues from patients without neurological disease, patients with inflammatory brain disorders, and patients with ischemic brain lesions. To identify fetuin-A-positive cells in these tissues we co-localized fetuin-A with GFAP (astrocytes) and CD68 (macrophages, activated microglia).

Results and discussion

Unlike previous reports, we detected fetuin-A protein also in mature human brain as would be expected from an abundant plasma protein also present in cerebrospinal fluid. Fetuin-A immunoreactivity was increased in ischemic white matter and decreased in inflamed cerebellar tissue. Fetuin-A immunostaining was predominantly associated with neurons and astrocytes. Unlike the developing brain, the adult brain lacked fetuin-A immunostaining in CD68-positive microglia. Our findings suggest a role for fetuin-A in tissue remodeling of neonatal brain, which becomes obsolete in the adult brain, but is re-activated in damaged brain tissue. To further assess the role of fetuin-A in the mature brain, animal models involving ischemia and inflammation need to be studied.

Serum Fetuin-A Levels in Patients with Bilateral Basal Ganglia Calcification

BACKGROUND AND PURPOSE

The idiopathic basal ganglia calcification (Fahr syndrome) may occur due to senility. Fetuin-A is a negative acute phase reactant which inhibits calcium-phosphorus precipitation and vascular calcification. In this study, we aimed to evaluate whether serum fetuin-A levels correlate with bilateral basal ganglia calcification.

METHOD

Forty-five patients who had bilateral basal ganglia calcification on brain CT were selected according to the inclusion and exclusion criteria, and 45 age and gender-matched subjects without basal ganglia calcification were included for the control group. Serum fetuin-A levels were measured from venous blood samples. All participants were divided into two groups; with and without basal ganglia calcification. These groups were divided into subgroups regarding age (18-32 and 33-45 years of age) and gender (male, female).

RESULTS

We detected lower levels of serum fetuin-A in patients with basal ganglia calcification compared with the subjects without basal ganglia calcification. In all subgroups (female, male, 18-32 years and 33-45 years), mean fetuin-A levels were significantly lower in patients with basal ganglia calcification (p = 0.017, p = 0.014, p = 0.024, p = 0.026, p = 0.01 respectively). And statistically significantly lower levels of fetuin-A was found to be correlated with the increasing densities of calcification in the calcified basal ganglia group (p-value: <0.001).

CONCLUSION

Considering the role of fetuin-A in tissue calcification and inflammation, higher serum fetuin-A levels should be measured in patients with basal ganglia calcification. We believe that the measurement of serum fetuin-A may play a role in the prediction of basal ganglia calcification as a biomarker.

An astrocyte derived extracellular matrix coating reduces astrogliosis surrounding chronically implanted microelectrode arrays in rat cortex

Available evidence suggests that the magnitude of the foreign body response (FBR) to implants placed in cortical brain tissue is affected by the extent of vasculature damage following device insertion and the magnitude of the ensuing macrophage response. Since the extracellular matrix (ECM) serves as a natural hemostatic and immunomodulatory agent, we examined the ability of an FDA-approved neurosurgical hemostatic coating and an ECM coating derived from primary rat astrocytes to reduce the FBR surrounding a penetrating microelectrode array chronically implanted in rat cortex. Using quantitative methods, we examined various components of the FBR in vitro and after implantation. In vitro assays showed that both coatings accelerated coagulation in a similar fashion but only the astrocyte-derived material suppressed macrophage activation. In addition, the ECM coating derived from astrocytes, also decreased the astrogliotic response 8 weeks after implantation. Neither coating had a significant influence on the intensity or spatial distribution of FBR biomarkers 1 week after implantation or on degree of macrophage activation or neuronal survival at the later time point. The results show that microelectrode coatings with similar hemostatic properties but different immunomodulatory characteristics differentially affect the FBR to an anchored, single-shank, silicon microelectrode array. The results also support the concept that divergent biological pathways affect the various components of the FBR in the CNS and suggests that decreasing its impact will require a multifaceted approach.

Association of AHSG with alopecia and mental retardation (APMR) syndrome

Alopecia with mental retardation syndrome (APMR) is a very rare autosomal recessive condition that is associated with total or partial absence of hair from the scalp and other parts of the body as well as variable intellectual disability. Here we present whole-exome sequencing results of a large consanguineous family segregating APMR syndrome with seven affected family members. Our study revealed a novel predicted pathogenic, homozygous missense mutation in the AHSG (OMIM 138680) gene (AHSG: NM_001622:exon7:c.950G>A:p.Arg317His). The variant is predicted to affect a region of the protein required for protein processing and disrupts a phosphorylation motif. In addition, the altered protein migrates with an aberrant size relative to healthy individuals. Consistent with the phenotype, AHSG maps within APMR linkage region 1 (APMR 1) as reported before, and falls within runs of homozygosity (ROH). Previous families with APMR syndrome have been studied through linkage analyses and the linkage resolution did not allow pointing out to a single gene candidate. Our study is the first report to identify a homozygous missense mutation for APMR syndrome through whole-exome sequencing.

The Effect of Chronic Methamphetamine Exposure on the Hippocampal and Olfactory Bulb Neuroproteomes of Rats

Nowadays, drug abuse and addiction are serious public health problems in the USA. Methamphetamine (METH) is one of the most abused drugs and is known to cause brain damage after repeated exposure. In this paper, we conducted a neuroproteomic study to evaluate METH-induced brain protein dynamics, following a two-week chronic regimen of an escalating dose of METH exposure. Proteins were extracted from rat brain hippocampal and olfactory bulb tissues and subjected to liquid chromatography-mass spectrometry (LC-MS/MS) analysis. Both shotgun and targeted proteomic analysis were performed. Protein quantification was initially based on comparing the spectral counts between METH exposed animals and their control counterparts. Quantitative differences were further confirmed through multiple reaction monitoring (MRM) LC-MS/MS experiments. According to the quantitative results, the expression of 18 proteins (11 in the hippocampus and 7 in the olfactory bulb) underwent a significant alteration as a result of exposing rats to METH. 13 of these proteins were up-regulated after METH exposure while 5 were down-regulated. The altered proteins belonging to different structural and functional families were involved in processes such as cell death, inflammation, oxidation, and apoptosis.

The relevance of human fetal subplate zone for developmental neuropathology of neuronal migration disorders and cortical dysplasia

The human fetal cerebral cortex develops through a series of partially overlapping histogenetic events which occur in transient cellular compartments, such as the subplate zone. The subplate serves as waiting compartment for cortical afferent fibers, the major site of early synaptogenesis and neuronal differentiation and the hub of the transient fetal cortical circuitry. Thus, the subplate has an important but hitherto neglected role in the human fetal cortical connectome. The subplate is also an important compartment for radial and tangential migration of future cortical neurons. We review the diversity of subplate neuronal phenotypes and their involvement in cortical circuitry and discuss the complexity of late neuronal migration through the subplate as well as its potential relevance for pathogenesis of migration disorders and cortical dysplasia. While migratory neurons may become misplaced within the subplate, they can easily survive by being involved in early subplate circuitry; this can enhance their subsequent survival even if they have immature or abnormal physiological activity and misrouted connections and thus survive into adulthood. Thus, better understanding of subplate developmental history and various subsets of its neurons may help to elucidate certain types of neuronal disorders, including those accompanied by epilepsy.

Cerebrospinal fluid fetuin-A is a biomarker of active multiple sclerosis

Background:

There is an urgent need for biomarkers in multiple sclerosis (MS) that can reliably measure ongoing disease activity relative to inflammation, neurodegeneration, and demyelination/remyelination. Fetuin-A was recently identified as a potential biomarker in MS cerebrospinal fluid (CSF). Fetuin-A has diverse functions, including a role in immune pathways.

Objective:

The objective of this research is to investigate whether fetuin-A is a direct indicator of disease activity.

Methods:

We measured fetuin-A in CSF and plasma of patients with MS and correlated these findings to clinical disease activity and natalizumab response. Fetuin-A expression was characterized in MS brain tissue and in experimental autoimmune encephalomyelitis (EAE) mice. We also examined the pathogenic role of fetuin-A in EAE using fetuin-A-deficient mice.

Results:

Elevated CSF fetuin-A correlated with disease activity in MS. In natalizumab-treated patients, CSF fetuin-A levels were reduced one year post-treatment, correlating with therapeutic response. Fetuin-A was markedly elevated in demyelinated lesions and in gray matter within MS brain tissue. Similarly, fetuin-A was elevated in degenerating neurons around demyelinated lesions in EAE. Fetuin-A-deficient mice demonstrated delayed onset and reduced severity of EAE symptoms.

Conclusions:

Our results show that CSF fetuin-A is a biomarker of disease activity and natalizumab response in MS. Neuronal expression of fetuin-A suggests that fetuin-A may play a pathological role in the disease process.