Different association of circulating levels of adipocyte and epidermal fatty acid-binding proteins with metabolic syndrome and coronary atherosclerosis in Chinese adults

Correlation between the serum FABP4, ANGPTL3, and ANGPTL4 levels and coronary artery disease

BACKGROUND

Lipid metabolism related factors, such as angiopoietin-like protein 3 (ANGPTL3), angiopoietin-like 4 (ANGPTL4), fatty acid-binding protein 4 (FABP4) are newly discovered factors that can affect coronary artery disease (CAD). In this study, we aimed to investigate the relationship between CAD and these lipid metabolism factors.

HYPOTHESIS

ANGPTL3, ANGPTL4, and FABP4 may provide a new method for the control of CAD risk factors and the prevention and treatment of CAD.

METHODS

We enrolled 284 consecutive inpatients with suspected CAD and divided them into CAD and non-CAD groups based on the coronary angiography results. Serum ANGPTL3, ANGPTL4, FABP4, and tumor necrosis factor-α (TNF-α) levels were estimated using the enzyme-linked immunosorbent assay. Multivariate logistic regression was used to assess the risk factors for CAD. The receiver operating characteristic curve was used to determine the cutoff and diagnostic values.

RESULTS

The serum TNF-α, FABP4, ANGPTL3, and ANGPTL4 values showed a significant difference between the CAD and non-CAD groups (p < .05). After adjusting for confounding factors, the FABP4, ANGPTL3, and ANGPTL4 levels were independently associated with CAD (p < .05). The ANGPTL3 expression level was an independent risk factor for CAD in patients with hypertension, but not in those without hypertension. The ANGPTL3 > 67.53 ng/mL, ANGPTL4 > 29.95 ng/mL, and FABP4 > 1421.25 ng/L combination had the highest diagnostic value for CAD.

CONCLUSION

ANGPTL3, ANGPTL4, and FABP4 were identified as independent risk factors for CAD and have valuable clinical implications for the diagnosis and treatment of CAD.

Circulating FABP-4 Levels in Patients with Atherosclerosis or Coronary Artery Disease: A Comprehensive Systematic Review and Meta-Analysis

Background

Cardiovascular diseases (CDs), notably coronary artery disease (CAD) due to atherosclerosis, impose substantial global health and economic burdens. Fatty acid-binding proteins (FABPs), including FABP-4, have been recently linked to CDs. This study conducted a systematic review and meta-analysis to examine FABP-4 levels in CAD and atherosclerosis patients, exploring their potential links to these conditions.

Methods

A systematic review and meta-analysis were done based on the PRISMA guideline. The international databases including Medline, Embase, Cochrane Library, Scopus, Web of Science, and UpToDate were searched to find all related studies on the effect of FABP-4 on patients with CAD or atherosclerosis which were published till June 2022 without language restriction. The Cochran's Q-test and I2 statistic were applied to assess heterogeneity, a random effect model was used to estimate the pooled standardized mean difference (SMD), a metaregression method was utilized to investigate the factors affecting heterogeneity between studies, and Egger's test was used to assess the publication bias.

Results

Of 1051 studies, 9 studies with a sample size of 2327 were included in the systematic review and meta-analysis. The level of circulating FABP-4 in the patient groups was significantly higher than in the control groups (SMD = 0.60 (95% CI: 0.30 to 0.91, I2: 91.47%)). The SMD in female and male patients were 0.26 (95% CI: 0.01 to 0.52, I2: 0%) and 0.22 (95% CI: 0.08 to 0.35, I2: 44.7%), respectively. There was considerable heterogeneity between the studies. The countries had a positive relationship with heterogeneity (coefficient = 0.29, p < 0.001); but BMI, lipid indices, gender, study design, and type of kit had no effect on the heterogeneity. No publication bias was observed (p: 0.137).

Conclusion

In summary, this meta-analysis revealed elevated circulating FABP-4 levels in CDs, suggesting its potential as a biomarker for these conditions. Further research is warranted to explore its clinical relevance.

Fatty-Acid-Binding Protein 4 as a Novel Contributor to Mononuclear Cell Activation and Endothelial Cell Dysfunction in Atherosclerosis

Background—Elevated circulating fatty-acid-binding protein 4 (FABP4) levels may be linked with cardiovascular events. This study aimed to investigate the mechanistic role of FABP4 in atherosclerosis. Methods—We recruited 22 patients with angiographically proven coronary artery disease (CAD) and 40 control subjects. Mononuclear cells (MNCs) and human coronary endothelial cells (HCAECs) were used for in vitro study. Results—Patients with CAD were predominantly male with an enhanced prevalence of hypertension, diabetes, and smoking history. FABP4 concentrations were up-regulated in culture supernatants of MNCs from CAD patients, which were positively correlated with the patients’ age, waist–hip ratio, body mass index, serum creatinine, type 2 diabetes, and the presence of hypertension. The adhesiveness of HCAECs to monocytic cells can be activated by FABP4, which was reversed by an FABP4 antibody. FABP4 blockade attenuated the oxidized low-density lipoprotein (oxLDL)-induced expression of ICAM-1, VCAM-1, and P-selectin. FABP4 impaired the tube formation and migration via the ERK/JNK/STAT-1 signaling pathway. FABP4 suppressed phosphorylation of eNOS and expression of SDF-1 protein, both of which can be reversed by treatment with VEGF. Blockade of FABP4 also improved the oxLDL-impaired cell function. Conclusion—We discovered a novel pathogenic role of FABP4 in MNC activation and endothelial dysfunction in atherosclerosis. FABP4 may be a therapeutic target for modulating atherosclerosis.

Altered epidermal fatty acid-binding protein expression in hepatocellular carcinoma predicts unfavorable outcomes

Objective

Hepatocellular carcinoma (HCC) is a rapidly proliferating malignancy that requires large amounts of fatty acids to synthesize cellular membranes and provide energy. Epidermal fatty acid-binding protein (EFABP) is uniquely expressed in epidermal cells, but its role and expression in HCC are not clear.

Subjects and methods

A total of 804 HCC specimens were collected to construct a tissue microarray (TMA) and for immunohistochemistry (IHC) analysis. The relationship between EFABP expression and clinical features of patients with HCC was analyzed.

Results

The EFABP IHC score for HCC tissue was 0.76±0.69, being significantly higher than that for matched nontumorous tissue (0.48±0.55; P<0.001). Using the median IHC score (ie, 0.8) in the tumorous tissue, a high level of EFABP expression was found in 57.3% (461/804) of the cases. Patients with HCC displaying high EFABP expression had poorer tumor differentiation (P=0.029), more vascular invasion (P=0.006), and a higher proportion of late TNM stage disease (P=0.042). Kaplan-Meier analysis revealed that the patients with high EFABP expression had significantly worse outcomes in terms of overall survival (P=0.003), worse disease-free survival (P=0.021), and a higher probability of recurrence (P=0.014). Multivariate analysis indicated that EFABP expression was an independent prognostic variable for overall survival (P=0.021) and disease-free survival (P=0.044). For HCC recurrence, only vascular invasion (P=0.020) and EFABP expression (P=0.026) were independent risk factors.

Conclusion

Our data revealed that EFABP expression was increased in HCC samples. High EFABP expression was correlated with shorter survival times in patients with HCC and served as an independent factor for worse outcomes. Our study therefore provides a promising bio-marker for the prognostic prediction of HCC and a potential therapeutic target for the disease.

Serum Fatty Acid Binding Protein 4 Concentrations Are Positively and Independently Associated with Blood Pressure and Abdominal Fat among Parameters in Health Check-Ups in Ordinary Middle-Aged Japanese Males

We wished to examine potential associations among blood concentrations of fatty acid-binding protein (FABP) 4 and parameters in health check-ups such as abdominal fat area (AFA) and blood pressure (BP) in middle-aged Japanese males. We conducted a cross-sectional study of males who participated in health check-ups in Japan. We excluded participants diagnosed with metabolic diseases by the time of their check-up. A total of 305 subjects (30-64 [mean±standard deviation, 47.3±8.5] y) were recruited. Areas of total-abdominal, visceral and subcutaneous fat were measured using computed tomography. We compared the association of serum concentrations of FABP4 with various clinical parameters by Pearson product-moment correlation coefficient (PPMCC) analyses, and by step-wise multivariate linear regression analyses (MLRA). PPMCC analyses showed that blood concentrations of FABP4 were positively associated with: body mass index; areas of fat (total abdominal, visceral, subcutaneous); systolic BP; diastolic BP; total cholesterol; low-density lipoprotein-cholesterol; triacylglycerol; activities of γ-glutamyl transpeptidase, aspartate aminotransferase and alanine aminotransferase; white blood cell count; and levels of creatinine. Step-wise MLRA showed that AFAs (visceral and subcutaneous) and diastolic BP were positively and independently associated with serum concentrations of FABP4 among the parameters tested. These data suggest that serum concentrations of FABP4 are independently and positively associated with BP and AFA among parameters measured in health check-ups in middle-aged Japanese males.

C1q/TNF-related protein-1: an adipokine marking and promoting atherosclerosis

AIMS

We investigated the association of the adipokine C1q/TNF-related protein (CTRP) 1 with coronary artery disease (CAD), and the biological vascular effects of CTRP1.

METHODS AND RESULTS

We analysed CTRP1 levels in sera of CAD patients (n = 451) and non-CAD controls (n = 686), and in coronary endarterectomy specimens (n = 32), non-atherosclerotic internal mammary arteries (n = 26), aortic atherosclerotic plaques (n = 15), and non-atherosclerotic aortic samples (n = 10). C1q/TNF-related protein-levels were higher in sera, endarterectomy specimens, aortic atherosclerotic plaques, and peripheral blood mononuclear cells (PBMCs) from CAD patients compared with controls, and were related to CAD severity. The production of CTRP1 was profusely induced by inflammatory cytokines and itself caused a concentration-dependent expression of adhesion molecules and inflammatory markers in human endothelial cells, human peripheral blood monocytes, and THP-1 cells. C1q/TNF-related protein-1 induced p38-dependent monocyte-endothelium adhesion in vitro and the recruitment of leucocytes to mesenteric venules in C57BL/6 mice. Immunohistochemistry of atherosclerotic femoral arteries exhibited CD68 and VE-cadherin loci-associated increased CTRP1 expression in plaques. Compared with saline, intraperitoneal injection of recombinant CTRP1 protein (200 μg/kg) every other day promoted atherogenesis in apoE(-/-) mice at 24 weeks. However, pro-atherogenic effects were significantly attenuated in CTRP1(-/-)/apoE(-/-) double-knockout mice compared with apoE(-/-) mice, with a consistent decrease in vascular adhesion molecule, phospho-p38 and TNF-α expression and macrophage infiltration in plaque in CTRP1(-/-) and double-knockout mice. Tumour necrosis factor-α-induced expression of adhesion molecules and cytokines were lower in primary endothelial cells and macrophages from CTRP(-/-) mice than in those from C57BL/6 mice.

CONCLUSION

C1q/TNF-related protein-1 is a marker of atherosclerosis in humans and promotes atherogenesis in mice.

Impact of epidermal fatty acid binding protein on 2D-NMR-assessed atherogenic dyslipidemia and related disorders

BACKGROUND

The role of circulating FABP5 on metabolic alterations is under active evaluation. On the other hand, FABP5 SNPs (rs454550 and rs79370435) seem to modulate its effect.

OBJECTIVES

Our aim was to examine the role of circulating FABP5 levels and its main SNPs in atherogenic dyslipidemia (AD) assessed by 2D-Nuclear Magnetic Resonance (NMR) and related metabolic and inflammation markers. We hypothesized that circulating FABP5 may be a biomarker for metabolic risk.

METHODS

We studied 459 subjects admitted to the metabolism unit because of lipid metabolism disturbances and/or associated disorders. After a 6-week lipid-lowering drug wash-out period, anamnesis and physical examination were performed. Carotid intime-media thickness (cIMT) was measured by ultrasound. FABP5, FABP4, lipids, metabolic proteins, and enzymes were determined by biochemical methods. The lipid profile was assessed by NMR. The rs454550 and rs79370435 FABP5 gene variants were also determined.

RESULTS

The FABP5 plasma levels were positively correlated with adiposity, glucose metabolism, and lipolysis parameters and were associated with AD, as assessed by NMR. There was a significant positive correlation between hsCRP and FABP5. The presence of type 2 diabetes, obesity, metabolic syndrome, or AD was associated with higher FABP5 plasma levels (P < .005). The FABP5 concentrations, but not those of FABP4, were higher in patients with carotid plaques. FABP5 was a main determinant of plaque presence according to logistic regression analysis. The rare rs454550 allele was hyper-represented in nonobese subjects (P = .011).

CONCLUSIONS

FABP5 is a biomarker of adiposity-associated metabolic derangements that include AD thus underscoring the concomitant presence of inflammation. FABP5 is associated with increased subclinical atherosclerosis.

Evaluation of circulating adipokines and abdominal obesity as predictors of significant myocardial ischemia using gated single-photon emission computed tomography

Objective

Coronary artery disease (CAD) is associated with abdominal obesity and metabolic syndrome. Adipocytes secrete adipokines, including the newly discovered adipocyte fatty acid binding protein (A-FABP) and chemerin. Adipokines contribute to the pathogenesis of CAD. In patients with CAD, the presence of significant ischemia predicts adverse outcomes. It is unknown whether adipokines can be better predictors of the presence of significant myocardial ischemia than conventional risk factors. This study aimed to compare adipokines with clinical risk factors and abdominal obesity as predictive factors for significant myocardial ischemia.

Methods

One hundred and ninety-six adults with suspected, but unproven, CAD were consecutively enrolled. The main measures were clinical and biochemical parameters and stress myocardial perfusion imaging with gated myocardial perfusion single-photon emission computed tomography (SPECT), with computed tomography (CT) attenuation correction. The abdominal visceral fat area was examined using a hybrid SPECT/CT scanner. Serum levels of high-sensitivity C-reactive protein (hs-CRP) and adipokines (adiponectin, A-FABP, and chemerin) were evaluated.

Results

A-FABP levels correlated significantly with adiponectin, hs-CRP, body mass index, waist circumference, and visceral fat area. A-FABP was significantly associated with metabolic syndrome (OR 3.2, 95% CI 1.6–6.4, p = 0.001), significant myocardial ischemia (OR 1.9, 95% CI 1.0–3.4, p = 0.05), and stress lung-to-heart ratio (β = 0.03, p = 0.03) on SPECT. Chemerin was significantly associated with serum triglyceride levels but not with metabolic syndrome, significant ischemia, or stress lung-to-heart ratio on SPECT. A-FABP was better at detecting significant inducible ischemia than other biomarkers, although this was a modest improvement (area under ROC curve 0.579, 95% CI 0.46–0.69).

Conclusions

Serum A-FABP concentrations correlate significantly with visceral fat area, metabolic syndrome, and predicted significant myocardial ischemia on SPECT. This may help to more accurately assess CAD risk, especially in patients with metabolic syndrome.

Structural basis for ligand regulation of the fatty acid-binding protein 5, peroxisome proliferator-activated receptor β/δ (FABP5-PPARβ/δ) signaling pathway

Fatty acid-binding proteins (FABPs) are a widely expressed group of calycins that play a well established role in solubilizing cellular fatty acids. Recent studies, however, have recast FABPs as active participants in vital lipid-signaling pathways. FABP5, like its family members, displays a promiscuous ligand binding profile, capable of interacting with numerous long chain fatty acids of varying degrees of saturation. Certain "activating" fatty acids induce the protein's cytoplasmic to nuclear translocation, stimulating PPARβ/δ transactivation; however, the rules that govern this process remain unknown. Using a range of structural and biochemical techniques, we show that both linoleic and arachidonic acid elicit FABP5's translocation by permitting allosteric communication between the ligand-sensing β2 loop and a tertiary nuclear localization signal within the α-helical cap of the protein. Furthermore, we show that more saturated, nonactivating fatty acids inhibit nuclear localization signal formation by destabilizing this activation loop, thus implicating FABP5 specifically in cis-bonded, polyunsaturated fatty acid signaling.

Circulating FABP4 and FABP5 levels are differently linked to OSA severity and treatment

OBJECTIVE

To evaluate circulating adipocyte and epidermal fatty acid-binding protein (FABP4 and FABP5) concentrations in patients with obstructive sleep apnea (OSA), as well as the effects of continuous positive airway pressure (CPAP) treatment.

METHODS

Our cross-sectional study included 125 patients. After polysomnography, 58 participants met the criteria for CPAP treatment and were included in a closed cohort study of 8 weeks of CPAP treatment. General anthropometric and biochemical data and circulating FABP4 and FABP5 levels were determined in all patients at baseline and after CPAP treatment in those receiving this therapy.

RESULTS

Circulating FABP4 but not FABP5 levels were higher in patients with OSA (P = 0.003). FABP4 but not FABP5 values were associated with parameters of OSA severity independently of age, gender, adiposity and insulin resistance (P < 0.05). FABP4 but not FABP5 concentrations were determinants of OSA presence (OR: 1.11, P = 0.010) and severity (OR: 1.06, P = 0.020). After CPAP treatment, FABP4 levels decreased in the more severe patients (P = 0.019), while FABP5 levels increased in all patients (P < 0.001).

CONCLUSIONS

FABP4 is directly associated with obstructive sleep apnea severity and did not change with continuous positive airway pressure treatment, while FABP5 was not associated with obstructive sleep apnea severity and increased with continuous positive airway pressure treatment. FABP4 and FABP5 have different associations with obstructive sleep apnea. FABP4 but not FABP5 could be considered a marker of metabolic alterations in obstructive sleep apnea patients.

Cigarette smoke decreases airway epithelial FABP5 expression and promotes Pseudomonas aeruginosa infection

Cigarette smoking is the primary cause of Chronic Obstructive Pulmonary Disease (COPD), which is characterized by chronic inflammation of the airways and destruction of lung parenchyma. Repeated and sustained bacterial infections are clearly linked to disease pathogenesis (e.g., exacerbations) and a huge burden on health care costs. The airway epithelium constitutes the first line of host defense against infection and our previous study indicated that Fatty Acid Binding Protein 5 (FABP5) is down regulated in airway epithelial cells of smokers with COPD as compared to smokers without COPD. We hypothesized that cigarette smoke (CS) exposure down regulates FABP5, thus, contributing to a more sustained inflammation in response to bacterial infection. In this report, we show that FABP5 is increased following bacterial infection but decreased following CS exposure of primary normal human bronchial epithelial (NHBE) cells. The goal of this study was to address FABP5 function by knocking down or overexpressing FABP5 in primary NHBE cells exposed to CS. Our data indicate that FABP5 down regulation results in increased P. aeruginosa bacterial load and inflammatory cytokine levels (e.g., IL-8) and decreased expression of the anti-bacterial peptide, β defensin-2. On the contrary, FABP5 overexpression exerts a protective function in airway epithelial cells against P. aeruginosa infection by limiting the production of IL-8 and increasing the expression of β defensin-2. Our study indicates that FABP5 exerts immunomodulatory functions in the airway epithelium against CS exposure and subsequent bacterial infection through its modulation of the nuclear receptor peroxisome proliferator-activated receptor (PPAR)-γ activity. These findings support the development of FABP5/PPAR-γ-targeted therapeutic approach to prevent airway inflammation by restoring antimicrobial immunity during COPD exacerbations.

Fatty acid-binding protein 4 impairs the insulin-dependent nitric oxide pathway in vascular endothelial cells

Background

Recent studies have shown that fatty acid-binding protein 4 (FABP4) plasma levels are associated with impaired endothelial function in type 2 diabetes (T2D). In this work, we analysed the effect of FABP4 on the insulin-mediated nitric oxide (NO) production by endothelial cells in vitro.

Methods

In human umbilical vascular endothelial cells (HUVECs), we measured the effects of FABP4 on the insulin-mediated endothelial nitric oxide synthase (eNOS) expression and activation and on NO production. We also explored the impact of exogenous FABP4 on the insulin-signalling pathway (insulin receptor substrate 1 (IRS1) and Akt).

Results

We found that eNOS expression and activation and NO production are significantly inhibited by exogenous FABP4 in HUVECs. FABP4 induced an alteration of the insulin-mediated eNOS pathway by inhibiting IRS1 and Akt activation. These results suggest that FABP4 induces endothelial dysfunction by inhibiting the activation of the insulin-signalling pathway resulting in decreased eNOS activation and NO production.

Conclusion

These findings provide a mechanistic linkage between FABP4 and impaired endothelial function in diabetes, which leads to an increased cardiovascular risk.

Small lipid-binding proteins in regulating endothelial and vascular functions: focusing on adipocyte fatty acid binding protein and lipocalin-2

Dysregulated production of adipokines from adipose tissue plays a critical role in the development of obesity-associated cardiovascular abnormalities. A group of adipokines, including adipocyte fatty acid binding protein (A-FABP) and lipocalin-2, possess specific lipid-binding activity and are up-regulated in obese human subjects and animal models. They act as lipid chaperones to promote lipotoxicity in endothelial cells and cause endothelial dysfunction under obese conditions. However, different small lipid-binding proteins modulate the development of vascular complications in distinctive manners, which are partly attributed to their specialized structural features and functionalities. By focusing on A-FABP and lipocalin-2, this review summarizes recent advances demonstrating the causative roles of these newly identified adipose tissue-derived lipid chaperones in obesity-related endothelial dysfunction and cardiovascular complications. The specific lipid-signalling mechanisms mediated by these two proteins are highlighted to support their specialized functions. In summary, A-FABP and lipocalin-2 represent potential therapeutic targets to design drugs for preventing vascular diseases associated with obesity.

LINKED ARTICLES

This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.