Serum fetuin-A levels are independently correlated with vascular endothelial growth factor and C-reactive protein concentrations in type 2 diabetic patients with diabetic retinopathy

Fetuin-B Overexpression Promotes Inflammation in Diabetic Retinopathy Through Activating Microglia and the NF-κB Signaling Pathway

PURPOSE

To investigate the expression, source, role, and mechanism of Fetuin-B (FETUB) in diabetic retinopathy (DR).

METHODS

ELISA and immunofluorescence were used to analyze the concentration of FETUB in plasma, aqueous fluid, and tissue specimens of patients with DR and healthy controls. Immunofluorescence, q-PCR, and western blotting were used to examine the expression of FETUB in DR mice and cells cultured with different concentrations of glucose. BV2 microglia cell line and DR mice were treated using FETUB recombination protein and FETUB shRNA to explore the function of FETUB in DR by q-PCR, western blotting, and immunofluorescence.

RESULTS

FETUB concentrations in plasma, aqueous fluid, and tissue specimens were significantly increased in DR patients. The mice in DR group had a higher concentration of FETUB in the retina and liver tissues than those in the control group, and the expression of FETUB was increased in both ARPE19 and BV2 cells under a high-glucose environment. The ratio of p-P65 (Phospho-P65)/P65 and the expression levels of TNF-α, VEGF, and ionized calcium binding adaptor molecule (IBA)-1 were increased in BV2 cells cultured with FETUB recombinant protein, while they were decreased in BV2 cells transfected with FETUB shRNA. Immunofluorescence staining showed that there were more IBA-1+ activated microglia in the retinas of the FETUB recombination protein group than in the retinas of the DR group, and there were fewer IBA-1+ activated microglia in the retinas of the FETUB shRNA group than in the retinas of the DR group.

CONCLUSIONS

FETUB sourced from endocrine, autocrine, and paracrine pathways could promote inflammation in DR by activating the NF-κB pathway and microglia.

Inflammation and retinal degenerative diseases

Vision is an ability that depends on the precise structure and functioning of the retina. Any kind of stress or injury can disrupt the retinal architecture and leads to vision impairment, vision loss, and blindness. Immune system and immune response function maintain homeostasis in the microenvironment. Several genetic, metabolic, and environmental factors may alter retinal homeostasis, and these events may initiate various inflammatory cascades. The prolonged inflammatory state may contribute to the initiation and development of retinal disorders such as glaucoma, age-related macular degeneration, diabetic retinopathy, and retinitis pigmentosa, which pose a threat to vision. In the current review, we attempted to provide sufficient evidence on the role of inflammation in these retinal disorders. Moreover, this review paves the way to focus on therapeutic targets of the disease, which are found to be promising.

Evaluation of Fetuin-A level in diabetic retinopathy

Background

Diabetic retinopathy (DR) is a micro-vascular consequence of diabetes mellitus (DM) that manifests clinically as retinal ischemia, neovascularization, altered retinal permeability, and macular edema. In the adult population, DR is now considered a leading cause of blindness. Fetuin-A is a multifunctional glycoprotein that, because of its dual role in insulin resistance and angiogenesis, could be an early trigger of DR pathogenesis.

Objective

This study aimed to evaluate the level of Fetuin-A in diabetic patients with and without retinopathy and demonstrate if it could be used as an early indicator of DR.

Patients and methods

A case–control study enrolled 45 participants selected from Al-Zahraa University Hospital, between March 2021 and October 2021, they were divided into three groups: Group 1: healthy control group (n=15); Group 2: type 2 diabetic patients without DR (n=15); and Group 3: type 2 diabetic patients with DR (n=15). All groups were age- and sex-matched and were investigated by enzyme-linked immunosorbent assay (ELISA) to evaluate serum level of Fetuin-A.

Results

There was a highly significant difference of FBG, 2HPP, and HbA1c between the studied groups (p< 0.001), while there was no significant difference between the three studied groups regarding Fetuin-A. There were no significant correlation between Fetuin-A, glycemic parameters, and diabetic duration in Groups 2 and 3.

Conclusion

Fetuin-A has no significant role in the pathogenesis of diabetic retinopathy.

Serum Glycoproteomic Alterations in Patients with Diabetic Retinopathy

The precise molecular mechanisms of diabetic retinopathy (DR) pathogenesis are unclear, and treatment options are limited. There is an urgent need to discover and develop novel therapeutic targets for the treatment of this disease. Glycosylation is a post-translational modification that plays a critical role in determining protein structure, function, and stability. Recent studies have found that serum glycoproteomic changes are associated with the presence or progression of several inflammatory diseases. However, very little is known about the glycoproteomic changes associated with DR. In this study, glycoproteomic profiling of the serum of diabetic patients with and without DR was performed. A total of 15 glycopeptides from 11 glycoproteins were found to be significantly altered (5 upregulated and 10 downregulated) within the serum glycoproteome of DR patients. These glycoproteins are known to be involved in the maintenance of the extracellular matrix and complement system through peptidolytic activity or regulation.

Serum fetuin-B level is an independent marker for nonalcoholic fatty liver disease in patients with type 2 diabetes

OBJECTIVE

Previous studies have assessed serum fetuin-B and its relation to nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM) and as a link between them through inducing insulin resistance (IR). Therefore, we examined the potential of serum fetuin-B to be an independent marker for NAFLD in patients with T2DM.

PATIENTS AND METHODS

The study group consisted of 270 patients with T2DM. Clinical and laboratory features were evaluated. The NAFLD severity was graded by ultrasound into three subgroups: grade 0 (no fatty liver), grade 1 (mild fatty liver), and grade 2-3 (medium to severe fatty liver). Fetuin-B, retinol-binding protein-4, and adiponectin were measured.

RESULTS

Patients with grade 2-3 NAFLD had high fetuin-B levels in comparison with non-NAFLD group. Age and sex adjusted fetuin-B demonstrated positive correlations with triglycerides, γ-glutamyl transferase, fasting plasma glucose, 2-h postprandial plasma glucose, homeostasis model assessment of IR, fasting insulin, glycated hemoglobin, high-sensitivity C-reactive protein, and estimated glomerular filtration rate, but it had a negative correlation with serum creatinine. Adiponectin level was decreased with increasing NAFLD severity, but no difference was found in retinol-binding protein-4. The estimated odds ratio (OR) for the occurrence of grade 2-3 NAFLD was increased significantly with increasing levels of fetuin-B (OR: 3.92; 95% confidence interval: 2.14-8.32 vs. OR: 8.91; 95% confidence interval: 4.22-18.41). The OR of fetuin-B in the uppermost tertile group was still significant after controlling for homeostasis model assessment of IR, glycated hemoglobin, waist circumference, BMI, hepatic enzymes, high-density lipoprotein cholesterol, triglycerides, and high-sensitivity C-reactive protein.

CONCLUSIONS

Our study demonstrated that serum fetuin-B had an independent association with NAFLD in patients with T2DM.

Serum Vascular Endothelial Growth Factor Levels Correlate with Severity of Retinopathy in Diabetic Patients: A Systematic Review and Meta-Analysis

Background

Investigations regarding serum and plasma vascular endothelial growth factor (VEGF) levels in patients with diabetic retinopathy (DR) are conflicting. This meta-analysis is aimed at determining whether serum and plasma VEGF levels are associated with DR and its severity in diabetic patients.

Methods

PubMed and EMBASE were used to search for published studies, and serum and plasma VEGF levels were compared among DR, nonproliferative diabetic retinopathy (NPDR), proliferative diabetic retinopathy (PDR), and nondiabetic retinopathy (NDR) patients. Standardized mean differences (SMD) and 95% confidence interval (CI) were pooled using a random effects model.

Results

A total of 29 studies comprising 1805 DR (or NPDR or PDR) patients and 1699 NDR patients were included. ELISA was used to evaluate serum or plasma VEGF levels in all except for two studies included in this meta-analysis. Overall, serum VEGF levels were significantly higher in DR patients (SMD: 0.74, 95% CI: 0.44-1.03) than those in NDR patients, while plasma VEGF levels were not in the comparison (SMD: 0.40, 95% CI: −0.13-0.92). Similarly, NPDR (SMD: 0.51, 95% CI: 0.22-0.80) and PDR (SMD: 1.32, 95% CI: 0.79-1.85) patients had higher serum VEGF levels compared with NDR patients, but the difference was not significant in plasma samples (SMD: 0.24, 95% CI: −0.47-0.95; SMD: 0.37, 95% CI: −0.30-1.05). In addition, serum VEGF levels were higher in PDR patients than those in NPDR patients (SMD: 0.87, 95% CI: 0.41-1.33), but plasma VEGF levels were not (SMD: −0.00, 95% CI: −0.31-0.31). The subgroup and metaregression analysis revealed that the study location, study design, and publication year of a study have certain influence on heterogeneity between studies in serum or plasma samples.

Conclusions

VEGF levels in the serum instead of those in the plasma correlate to the presence and severity of DR in diabetic patients. Further large-scale studies are required to confirm these findings.

The Clinical Significance and Potential Role of C-Reactive Protein in Chronic Inflammatory and Neurodegenerative Diseases

C-reactive protein (CRP) is an acute-phase protein synthesized by hepatocytes in response to pro-inflammatory cytokines during inflammatory/infectious processes. CRP exists in conformationally distinct forms such as the native pentameric CRP and monomeric CRP (mCRP) and may bind to distinct receptors and lipid rafts and exhibit different functional properties. It is known as a biomarker of acute inflammation, but many large-scale prospective studies demonstrate that CRP is also known to be associated with chronic inflammation. This review is focused on discussing the clinical significance of CRP in chronic inflammatory and neurodegenerative diseases, such as cardiovascular disease, type 2 diabetes mellitus, age-related macular degeneration, hemorrhagic stroke, Alzheimer’s disease, and Parkinson’s disease, including recent advances on the implication of CRP and its forms specifically on the pathogenesis of these diseases. Overall, we highlight the advances in these areas that may be translated into promising measures for the diagnosis and treatment of inflammatory diseases.

Circulating Serum Fatty Acid-Binding Protein 4 Levels Predict the Development of Diabetic Retinopathy in Type 2 Diabetic Patients

PURPOSE

Fatty acid-binding protein 4 (FABP4) has been implicated in the pathology of diabetes and macrovascular diseases. Serum FABP4 levels were determined in type 2 diabetic patients without diabetic retinopathy (DR) at admission in order to investigate a possible contribution of FABP4 to the increased risk of 5-year incidence of DR.

DESIGN

Cohort study.

METHODS

A total of 738 patients with type 2 diabetes without DR were consecutively enrolled and followed up prospectively. Retinopathy evaluation was annually performed by ophthalmologists in the following 5 years. Multivariate analyses were performed using logistic regression models.

RESULTS

During the follow-up period, 152 (20.60% [95% CI: 17.68%-23.51%]) patients developed DR and 60 (8.13% [95% CI: 6.16%-10.10%]) patients developed vision-threatening DR (VTDR). Nonparametric Spearman rank correlation revealed a statistically significant positive correlation between serum FABP 4 level and international Clinical Diabetic Retinopathy Severity Scales (r = 0.348; P < .001). After adjustment for other established risk factors, in multivariate models comparing the third and fourth quartiles against the first quartile of the FABP4, levels of FABP4 were associated with DR and the adjusted risk of DR increased by 124% (OR = 2.24 [95% CI 1.65-3.68], P = .006) and 227% (3.27 [2.04-5.56], P < .001), respectively. Similarly, the adjusted risk of VTDR increased by 140% (OR = 2.40 [95% CI 1.32-3.82], P = .001) and 278% (3.78 [2.17-6.59], P < .001), respectively.

CONCLUSION

FABP4 shows potential as a novel biomarker for DR prediction in Chinese patients with T2DM, and strict glycemic control and more frequent retinal examination should be highlighted for T2DM patients with the highest quartile range of FABP4.

The association between circulating fetuin-A levels and type 2 diabetes mellitus risk: systematic review and meta-analysis of observational studies

BACKGROUND AND OBJECTIVE

Fetuin-A is a liver-derived circulating protein that is associated with insulin resistance and diabetes. The objective of this systematic review and meta-analysis of published observational studies was to investigate mean levels of fetuin-A in T2D patients and the relationship between blood fetuin-A levels and T2D risk.

MATERIALS AND METHODS

PubMed, Embase, Google Scholar, Web of Science, and The Cochrane Library were systematically searched for potential relevant studies up to 1 December 2016. Natural logarithm-transformed estimate risks, standard mean differences on the basis of Hedges's adjusted g, and 95% confidence intervals (CIs) were calculated for all eligible studies and were combined to measure the pooled data using random-effects model.

RESULTS

A total of 32 studies including 27 case-control and 5 cohort studies were included in the current study. Fetuin-A levels in T2D patients were significantly higher than control groups [Hedges' g = 1.73, 95% CI (1.25-2.22), P < 0.001], with significant heterogeneity across studies (P < 0.001, I ² = 98.46%). Findings from meta-analyses of cohort studies showed a statistically significant association between fetuin-A levels and T2D risk [rate ratio = 1.62, 95% CI (1.26-2.08), P < 0.001], with no significant heterogeneity (P = 0.10, I ² = 46.06%).

CONCLUSION

We found a significant relationship between the fetuin-A levels with T2D risk. Although fetuin-A may be as a potential screening and prediction biomarker or a therapeutic target in T2D patients, further studies are required in this regard.

Serum concentrations of fetuin B in lipodystrophic patients

OBJECTIVE

Fetuin B is an adipokine/hepatokine which is significantly elevated in insulin resistance/type 2 diabetes mellitus and hepatic steatosis. Regulation of fetuin B in patients with lipodystrophy (LD) - a disease group which is characterized by subcutaneous adipose tissue loss, hypertriglyceridemia, hepatic steatosis, insulin resistance, and dysregulation of several adipokines - has not been elucidated so far.

MATERIAL AND METHODS

Serum fetuin B levels were determined in 37 patients with LD, as well as in a control cohort consisting of 37 non-LD participants matched for age, gender, and body mass index. Furthermore, fetuin B was correlated with parameters of lipid metabolism, glucose control, renal function, and inflammation.

RESULTS

Median fetuin B serum levels were not significantly different between patients with LD (2980.7 µg/l; interquartile range: 841.7 µg/l) and non-LD controls (2647.3 µg/l; interquartile range: 923.6 µg/l; p = .105). Fetuin B was associated with age, body mass index, markers of renal function, and C reactive protein (CRP) in univariate correlation analyses. The associations with age and creatinine remained significant in multiple linear regression analysis.

CONCLUSIONS

Fetuin B serum concentrations are not significantly different between patients with LD and non-LD controls. Fetuin B does not seem to be a major pathogenetic factor in LD.

Emerging Human Fetuin A Assays for Biomedical Diagnostics

Human fetuin A (HFA) plays a prominent pathophysiological role in numerous diseases and pathophysiological conditions with considerable biomedical significance; one example is the formation of calciprotein particles in osteoporosis and impaired calcium metabolisms. With impressive advances in in vitro diagnostic assays during the last decade, ELISAs have become a workhorse in routine clinical diagnostics. Recent diagnostic formats involve high-sensitivity immunoassay procedures, surface plasmon resonance, rapid immunoassay chemistries, signal enhancement, and smartphone detection. The current trend is toward fully integrated lab-on-chip platforms with smartphone readouts, enabling health-care practitioners and even patients to monitor pathological changes in biomarker levels. This review provides a critical analysis of advances made in HFA assays along with the challenges and future prospects.

Changes of serum C-reactive protein and fetuin-A levels in patients with acute angle-closure glaucoma and type 2 diabetes mellitus

AIM: To investigate the changes of serum C-reactive protein (CRP) and fetuin-A (AHSG) levels in patients with acute angle-closure glaucoma and type 2 diabetes mellitus.

METHODS: Serum levels of CRP and AHSG were determined by ELISA and nephelometry in 37 patients with acute angle-closure glaucoma and type 2 diabetes mellitus (group A) and 21 patients with acute angle-closure glaucoma only (group B). At the same time, 15 healthy controls were enrolled.

RESULTS: Serum levels of CRP and AHSG in groups A and B were significantly higher than those in group C (P < 0.05). Serum levels of CRP and AHSG in group A were significantly higher than those in group B (9.51 mg/L ± 3.21 mg/L vs 5.93 mg/L ± 0.87 mg/L; 376.33 μg/mL ± 9.17 μg/mL vs 315.59 μg/mL ± 10.75 μg/mL, P < 0.05).

CONCLUSION: CRP and AHSG may be involved in the development and pathogenesis of acute angle-closure glaucoma with type 2 diabetes mellitus.

Regulatory SNPs Alter the Gene Expression of Diabetic Retinopathy Associated Secretary Factors

OBJECTIVES

Diabetic retinopathy (DR) is a common microvascular complication in both type I and type II diabetes. Several previous reports indicated the serum centration of some secretary factors were highly associated with DR. Therefore, we hypothesis regulatory SNPs (rSNPs) genotype in secretary factors may alter these gene expression and lead to DR.

METHODS

At first, pyrosequencing were applying to screen the SNPs which present allele frequency different in DR and DNR. Then individual genotyping was processed by Taqman assays in Taiwanese DR and DNR patients. To evaluate the effect of SNP allele on transcriptional activity, we measured promoter activity using luciferase reporter constructs.

RESULTS

We found the frequencies of the CC, CG, and GG genotype of the rs2010963 polymorphism were 15.09%, 47.14%, and 37.74% in DR and 12.90%, 19.35%, and 67.74% in DNR, respectively (p = 0.0205). The prevalence of DR was higher (p = 0.00793) in patients with the CC or CG genotype (62.26% and 32.26% for DR and DNR, respectively) compared with the patients with the GG genotype. To evaluate the effect of rs2010963-C allele on transcriptional activity, we measured promoter activity using luciferase reporter constructs. The rs2010963-C reporter showed 1.6 to 2-fold higher luciferase activity than rs2010963-G in 3 cell lines.

CONCLUSION

Our data proposed rs2010963-C altered the expression level of VEGFA in different tissues. We suggested small increase but long term exposure to VEGFA may lead to DR finally.