Serum FABP5 concentration is a potential biomarker for residual risk of atherosclerosis in relation to cholesterol efflux from macrophages

Consumption of tree nuts as snacks stimulates changes in plasma fatty acid profiles and adipose tissue gene expression in young adults at risk for metabolic syndrome

BACKGROUND AND AIMS

The prevalence of metabolic syndrome has been increasing in young adults, concomitant with the occurrence of increased abdominal adiposity. We previously reported that consuming tree nuts, as replacement for typical high-carbohydrate snacks, reduces visceral fat and waist circumference in young adults who have one or more metabolic syndrome risk factors. We aimed to investigate the effects of tree nuts snack consumption on plasma and adipose tissue fatty acid profiles along with changes in the expression of adipose tissue genes involved in thermogenesis, glycemia, adipocyte signaling, lipolysis, and immunity.

METHODS

A randomized parallel-arm 16-week intervention trial was conducted in 84 adults aged 22-36 years. Participants in both groups were provided with caloric goals for weight maintenance, daily menus, and pre-portioned snacks at every other week visits with study registered dietitians. Changes in dietary fatty acid intakes, plasma and abdominal subcutaneous adipose tissue (SAT) triglycerides fatty acid profiles using gas-liquid chromatography, and the expression of 241 genes in abdominal SAT were evaluated.

RESULTS

Consuming tree nuts snacks increased mono- and polyunsaturated fatty acid intakes yielding a 9-fold greater dietary unsaturated to saturated fat ratio. The tree nuts snack group also had significantly greater improvements in plasma 16:1/16:0 ratio; plasma phospholipids oleic and gamma linolenic acid content; plasma diglycerides, triglycerides, and cholesterol esters oleic acid content; and total plasma monounsaturated fatty acids. While abdominal SAT only showed trends for increased oleic acid content and unsaturated to saturated fat ratio, the tree nuts snacks participants had altered expression of 13 genes in abdominal SAT that have roles in nutrient sensing, energy homeostasis, and vulnerability to obesity.

CONCLUSIONS

Replacing typical high-carbohydrate snacks with tree nuts results in more favorable dietary, plasma, and adipose tissue fatty acid profiles that could aid in preventing the development of excess adiposity and cardiometabolic disease states including metabolic syndrome.

CLINICAL TRIAL REGISTRY

This trial was registered at clinicaltrials.gov NCT03969264.

Fatty acid binding proteins-mediated mitochondrial dysfunction in the development of age-related diseases: A review

Fatty acid-binding proteins (FABPs) act as lipid chaperones and play a role in the pathological processes of various lipid signaling pathways. Mitochondria are crucial for the regulation of lipid metabolism. As an aging marker, lipid-mediated mitochondrial dysfunction has been observed in the etiology of numerous diseases, including neurodegenerative diseases, metabolic syndromes, cardiovascular diseases, and tumorigenesis. Members of the FABP family have been identified to regulate mitochondrial function. Targeting FABPs specifically may provide a promising approach to improve mitochondrial function and treat age-related diseases. This review summarizes the connection between FABPs and mitochondrial function and highlights certain FABPs involved in age-related diseases that hold significant therapeutic promise.

Direct sensing of dietary ω-6 linoleic acid through FABP5-mTORC1 signaling

Diet influences macronutrient availability to cells, and although mechanisms of sensing dietary glucose and amino acids are well characterized, less is known about sensing lipids. We defined a nutrient signaling mechanism involving fatty acid-binding protein 5 (FABP5) and mechanistic target of rapamycin complex 1 (mTORC1) that is activated by the essential polyunsaturated fatty acid (PUFA) ω-6 linoleic acid (LA). FABP5 directly bound to the regulatory-associated protein of mTOR (Raptor) to enhance formation of functional mTORC1 and substrate binding, ultimately converging on increased mTOR signaling and proliferation. The amounts of FABP5 protein were increased in tumors and serum from triple-negative compared with those from receptor-positive breast cancer patients, which highlights its potential role as a biomarker that mediates cellular responses to ω-6 LA intake in this disease subtype.

Expression and Secretion of Intraocular Fatty Acid-Binding Protein 4 (ioFABP4) and 5 (ioFABP5) Are Regulated by Glucose Levels and Fatty Acids

Intraocularly, fatty acid-binding protein 4 (FABP4) and 5 (FABP5) mainly originate from human ocular choroidal fibroblasts (HOCF), and human nonpigmented ciliary epithelium (HNPCE) cells have been suggested to be pivotally involved in intraocular pathophysiology. To elucidate the unidentified regulatory mechanisms of the gene expression and protein secretion of FABPs, the effects of glucose levels, fatty acids (FAs), and peroxisome proliferator-activated receptor (PPAR) modulators were studied. To elucidate the additional biological role of FABPs, laser choroidal neovascularization (CNV) in Fabp4-/- and Fabp4/5-/- mice was analyzed by fluorescein angiography. By changing glucose levels, the secretion and expression of FABP4 in HOCF were significantly upregulated, whereas the secretion and expression of FABP5 in HNPCE decreased. The administration of various FAs, particularly docosahexaenoic acid (DHA), markedly increased the expression and secretion of both FABPs. PPAR modulators also influenced the secretion and expression of FABPs. In vivo, wild-type retina exhibited evident CNV with high fluorescein intensity, while Fabp4-/- retina showed reduced CNV formation and Fabp4/5-/- retina displayed evident CNV along with vitreous leakage. These findings suggest that (1) the production and secretion of intraocular FABP4 and FABP5 are distinctly regulated by glucose levels, FAs, and PPARs; and (2) intraocular FABP4 and FABP5 are critical for inducing retinal neovascularization and maintaining the blood-aqueous barrier.

IL-6R (trans-signaling) is a key regulator of reverse cholesterol transport in lipid-laden macrophages

Atherosclerosis is a cardiovascular disease caused by cholesterol-laden arterial plaques. This study evaluated the correlation between interleukin-6 (IL-6), its receptors (IL6R/CD126), and glycoprotein 130 (gp130) alongside atherosclerosis biomarkers in a cohort of 142 subjects, equally divided between lean and obese individuals. Subsequent analyses used THP-1-derived macrophages to assess the biochemical impact of inhibiting IL-6 receptors. IL-6 secretion increased with atherosclerosis in obese subjects, while IL6R/CD126 and gp130 on monocytes decreased. Pharmacological gp130 inhibition altered lipid metabolism, increasing LDLR gene expression and cholesterol synthesis via SREBF2 and mevalonate kinase, along with HMG-CoA reductase at protein levels. gp130-deficient cells produced more cholesterol and had lower ABCA1 levels, suggesting hindered cholesterol efflux. Filipin III staining confirmed cholesterol retention in gp130-inhibited cells. Ex-vivo investigation on lean PBMCs further defined the impact of gp130 inhibition on the reduction of cholesterol efflux. Our results indicates gp130 is crucial for macrophage reverse cholesterol transport and may be a target for atherosclerosis treatments.

The Association of the Cholesterol Efflux Capacity with the Paraoxonase 1 Q192R Genotype and the Paraoxonase Activity

AIMS

Paraoxonase 1 (PON1) binds to high-density lipoprotein (HDL) and protects against atherosclerosis. However, the relationship between functional PON1 Q192R polymorphism, which is associated with the hydrolysis of paraoxon (POXase activity) and atherosclerotic cardiovascular disease (ASCVD), remains controversial. As the effect of PON1 Q192R polymorphism on the HDL function is unclear, we investigated the relationship between this polymorphism and the cholesterol efflux capacity (CEC), one of the biological functions of HDL, in association with the PON1 activity.

METHODS

The relationship between PON1 Q192R polymorphisms and CEC was investigated retrospectively in 150 subjects without ASCVD (50 with the PON1 Q/Q genotype, 50 with the Q/R genotype, and 50 with the R/R genotype) who participated in a health screening program. The POXase and arylesterase (AREase: hydrolysis of aromatic esters) activities were used as measures of the PON1 activity.

RESULTS

The AREase activity was positively correlated with CEC independent of the HDL cholesterol levels. When stratified by the PON1 Q192R genotype, the POXase activity was also positively correlated with CEC independent of HDL cholesterol. PON1 Q192R R/R genotype carriers had a lower CEC than Q/Q or Q/R genotype carriers, despite having a higher POXase activity. Moreover, in a multiple regression analysis, the PON1 Q192R genotype was associated with the degree of CEC, independent of the HDL cholesterol and POXase activity.

CONCLUSIONS

The PON1 Q192R R allele is associated with reduced CEC in Japanese people without ASCVD. Further studies on the impact of this association on the severity of atherosclerosis and ASCVD development are thus called for.

Impaired Cholesterol Efflux Capacity rather than Low HDL-C Reflects Oxidative Stress under Acute Myocardial Infarction

AIMS

Acute myocardial infarction (AMI) causes irreversible damage to cardiomyocytes due to the discontinuation of oxygen supply and leads to systemic oxidative stress. It has been reported that high-density lipoprotein (HDL) particles have antioxidant capacity, and reduced antioxidant capacity is associated with decreased cholesterol efflux capacity (CEC). The purpose of this study was to clarify the usefulness of CEC measurement in patients with AMI.

METHODS

We investigated the association between CEC and oxidative stress status in a case-control study. This study included 193 AMI cases and 445 age- and sex-matched controls. We examined the associations of CEC with HDL-cholesterol (HDL-C) and oxidized human serum albumin (HSA), an index of systemic oxidative stress status, and the effect of aldehyde dehydrogenase 2 (ALDH2) rs671 polymorphism, which has been reported to affect HDL-C level and risk for MI, on these associations.

RESULTS

Both bivariable and multivariable analyses showed that CEC was positively correlated with HDL-C levels in both AMI cases and controls, with a weaker correlation in AMI cases than in controls. In AMI cases, oxidized HSA levels were associated with CEC in both bivariable and multivariable analyses, but not with HDL-C. These associations did not differ among the ALDH2 genotypes.

CONCLUSIONS

CEC, but not HDL-C level, reflects systemic oxidative stress status in patients with AMI. CEC measurement for patients with AMI may be useful in that it provides information on systemic oxidative stress status as well as atherosclerosis risk.

Fatty acid-binding protein 5 is a functional biomarker and indicator of ferroptosis in cerebral hypoxia

The progression of human degenerative and hypoxic/ischemic diseases is accompanied by widespread cell death. One death process linking iron-catalyzed reactive species with lipid peroxidation is ferroptosis, which shows hallmarks of both programmed and necrotic death in vitro. While evidence of ferroptosis in neurodegenerative disease is indicated by iron accumulation and involvement of lipids, a stable marker for ferroptosis has not been identified. Its prevalence is thus undetermined in human pathophysiology, impeding recognition of disease areas and clinical investigations with candidate drugs. Here, we identified ferroptosis marker antigens by analyzing surface protein dynamics and discovered a single protein, Fatty Acid-Binding Protein 5 (FABP5), which was stabilized at the cell surface and specifically elevated in ferroptotic cell death. Ectopic expression and lipidomics assays demonstrated that FABP5 drives redistribution of redox-sensitive lipids and ferroptosis sensitivity in a positive-feedback loop, indicating a role as a functional biomarker. Notably, immunodetection of FABP5 in mouse stroke penumbra and in hypoxic postmortem patients was distinctly associated with hypoxically damaged neurons. Retrospective cell death characterized here by the novel ferroptosis biomarker FABP5 thus provides first evidence for a long-hypothesized intrinsic ferroptosis in hypoxia and inaugurates a means for pathological detection of ferroptosis in tissue.

Identification of key genes for atherosclerosis in different arterial beds

Atherosclerosis (AS) is the pathologic basis of various cardiovascular and cerebrovascular events, with a high degree of heterogeneity among different arterial beds. However, mechanistic differences between arterial beds remain unexplored. The aim of this study was to explore key genes and potential mechanistic differences between AS in different arterial beds through bioinformatics analysis. Carotid atherosclerosis (CAS), femoral atherosclerosis (FAS), infrapopliteal atherosclerosis (IPAS), abdominal aortic atherosclerosis (AAS), and AS-specific differentially expressed genes (DEGs) were screened from the GSE100927 and GSE57691 datasets. Immune infiltration analysis was used to identify AS immune cell infiltration differences. Unsupervised cluster analysis of AS samples from different regions based on macrophage polarization gene expression profiles. Weighted gene co-expression network analysis (WGCNA) was performed to identify the most relevant module genes with AS. Hub genes were then screened by LASSO regression, SVM-REF, and single-gene differential analysis, and a nomogram was constructed to predict the risk of AS development. The results showed that differential expression analysis identified 5, 4, 121, and 62 CAS, FAS, IPAS, AAS-specific DEGs, and 42 AS-common DEGs, respectively. Immune infiltration analysis demonstrated that the degree of macrophage and mast cell enrichment differed significantly in different regions of AS. The CAS, FAS, IPAS, and AAS could be distinguished into two different biologically functional and stable molecular clusters based on macrophage polarization gene expression profiles, especially for cardiomyopathy and glycolipid metabolic processes. Hub genes for 6 AS (ADAP2, CSF3R, FABP5, ITGAX, MYOC, and SPP1), 4 IPAS (CLECL1, DIO2, F2RL2, and GUCY1A2), and 3 AAS (RPL21, RPL26, and RPL10A) were obtained based on module gene, gender stratification, machine learning algorithms, and single-gene difference analysis, respectively, and these genes were effective in differentiating between different regions of AS. This study demonstrates that there are similarities and heterogeneities in the pathogenesis of AS between different arterial beds.

Transcriptome-wide N6-methyladenosine methylation profile of atherosclerosis in mice

BACKGROUND

Atherosclerosis (AS) is a critical pathological event during the progression of cardiovascular diseases. It exhibits fibrofatty lesions on the arterial wall and lacks effective treatment. N6-methyladenosine (m6A) is the most common modification of eukaryotic RNA and plays an important role in regulating the development and progression of cardiovascular diseases. However, the role of m6A modification in AS remains largely unknown. Therefore, in this study, we explored the transcriptome distribution of m6A modification in AS and its potential mechanism.

METHODS

Methylation Quantification Kit was used to detect the global m6A levels in the aorta of AS mice. Western blot was used to analyze the protein level of methyltransferases. Methylated RNA immunoprecipitation with next-generation sequencing (MeRIP-seq) and RNA sequencing (RNA-seq) were used to obtain the first transcriptome range analysis of the m6A methylene map in the aorta of AS mice, followed by bioinformatics analysis. qRT-PCR and MeRIP-qRT-PCR were used to measure the mRNA and m6A levels in target genes.

RESULTS

The global m6A and protein levels of methyltransferase METTL3 were significantly increased in the aorta of AS mice. However, the protein level of demethylase ALKBH5 was significantly decreased. Through MeRIP-seq, we obtained m6A methylation maps in AS and control mice. In total, 26,918 m6A peaks associated with 13,744 genes were detected in AS group, whereas 26,157 m6A peaks associated with 13,283 genes were detected in the control group. Peaks mainly appeared in the coding sequence (CDS) regions close to the stop codon with the RRACH motif. Moreover, functional enrichment analysis demonstrated that m6A-containing genes were significantly enriched in AS-relevant pathways. Interestingly, a negative correlation between m6A methylation abundance and gene expression level was found through the integrated analysis of MeRIP-seq and RNA-seq data. Among the m6A-modified genes, a hypo-methylated but up-regulated (hypo-up) gene Fabp5 may be a potential biomarker of AS.

CONCLUSIONS

Our study provides transcriptome-wide m6A methylation for the first time to determine the association between m6A modification and AS progression. Our study lays a foundation for further exploring the pathogenesis of AS and provides a new direction for the treatment of AS.

Fatty Acid-Binding Proteins Identification during the Evolution of Metabolic Syndrome: A Raman Spectroscopy-Based Approach

Excess fat in abdominal deposits is a risk factor for multiple conditions, including metabolic syndrome (MetS); lipid metabolism plays an essential role in these pathologies; fatty acid-binding proteins (FABPs) are dedicated to the cytosolic transport of fat. FABP4, whose primary source is adipose tissue, is released into the circulation, acting as an adipokine, while FABP5 also accompanies the adverse effects of MetS. FABP4 and 5 are potential biomarkers of MetS, but their behavior during syndrome evolution has not been determined. Raman spectroscopy has been applied as an alternative method to disease biomarker detection. In this work, we detected spectral changes related to FABP4 and 5 in the serum at different points of time, using an animal model of a high-fat diet-induced MetS. FABP4 and 5 spectral changes show a contribution during the evolution of MetS, which indicates alteration to a molecular level that predisposes to established MetS. These findings place FABPs as potential biomarkers of MetS and Raman spectroscopy as an alternative method for MetS assessment.

A novel hepatocellular carcinoma-specific mTORC1-related signature for anticipating prognosis and immunotherapy

Tumor oncogenesis, cancer metastasis, and immune evasion were substantially impacted by the mammalian target of the rapamycin complex 1 (mTORC1) pathway. However, in hepatocellular carcinoma (HCC), no mTORC1 signaling-based gene signature has ever been published. mTORC1 scores were computed employing a single sample gene set enrichment analysis based on databases including the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). The PAG1, LHFPL2, and FABP5 expression levels were obtained to construct a mTORC1 pathway-related model. In two databases, the overall survival (OS) rate was shorter for high-mTORC1 score patients compared to those with low scores. The activation of TFs in the group with high risk was enhanced, such as the HIF-1 pathway. Additionally, it was discovered that a high mTORC1 score was linked to an immune exclusion phenotype and enhanced immunosuppressive cell infiltration. Notably, it was discovered that high-mTORC1 scores patients had poorer immunotherapeutic results and might not gain benefit from immunotherapy. When compared to the low HCC metastatic cell lines, the high HCC metastatic cell lines have overexpressed levels of PAG1, LHFPL2, and FABP5 expression. The expression of PAG1, LHFPL2, and FABP5 was inhibited by the MAPK and mTORC1 pathway inhibitors. Our study identified mTORC1 score signature can aid in the development of individualized immunotherapy protocols and predict the HCC patients' prognoses.

Additive Effects of Drinking Habits and a Susceptible Genetic Polymorphism on Cholesterol Efflux Capacity

AIMS

High levels of high-density lipoprotein cholesterol (HDL-C) are not necessarily effective in preventing atherosclerotic cardiovascular disease, and cholesterol efflux capacity (CEC) has attracted attention regarding HDL functionality. We aimed to elucidate whether drinking habits are associated with CEC levels, while also paying careful attention to confounding factors including serum HDL-C levels, other life style factors, and rs671 (＊2), a genetic polymorphism of the aldehyde dehydrogenase 2 (ALDH2) gene determining alcohol consumption habit.

METHODS

A cross-sectional study was performed in 505 Japanese male subjects who were recruited from a health screening program. Associations of HDL-C and CEC levels with drinking habits and ALDH2 genotypes were examined.

RESULTS

The genotype frequencies of ALDH2 ＊1/＊1 (homozygous wild-type genotype), ＊1/＊2 and ＊2/＊2 (homozygous mutant genotype) were 55%, 37% and 8%, respectively. Both HDL-C and CEC levels were higher in ALDH2 ＊1/＊1 genotype carriers than in ＊2 allele carriers. Although HDL-C levels were higher in subjects who had a drinking habit than in non-drinkers, CEC levels tended to be lower in subjects with ≥ 46 g/day of alcohol consumption than in non-drinkers. Furthermore, CEC levels tended to be lower in ALDH2 ＊1/＊1 genotype carriers with a drinking habit of ≥ 46 g/day than non-drinkers, while for ＊2 allele carriers, CEC levels tended to be lower with a drinking habit of 23-45.9 g/day compared to no drinking habit.

CONCLUSIONS

Our results suggest that heavy drinking habits may tend to decrease CEC levels, and in the ALDH2 ＊2 allele carriers, even moderate drinking habits may tend to decrease CEC levels.

Single-cell RNA sequencing reveals a novel inhibitory effect of ApoA4 on NAFL mediated by liver-specific subsets of myeloid cells

The liver immune microenvironment is a key element in the development of hepatic inflammation in NAFLD. ApoA4 deficiency increases the hepatic lipid burden, insulin resistance, and metabolic inflammation. However, the effect of ApoA4 on liver immune cells and the precise immune cell subsets that exacerbate fatty liver remain elusive. The aim of this study was to profile the hepatic immune cells affected by ApoA4 in NAFL. We performed scRNA-seq on liver immune cells from WT and ApoA4-deficient mice administered a high-fat diet. Immunostaining and qRT-PCR analysis were used to validate the results of scRNA-seq. We identified 10 discrete immune cell populations comprising macrophages, DCs, granulocytes, B, T and NK&NKT cells and characterized their subsets, gene expression profiles, and functional modules. ApoA4 deficiency led to significant increases in the abundance of specific subsets, including inflammatory macrophages (2-Mφ-Cxcl9 and 4-Mφ-Cxcl2) and activated granulocytes (0-Gran-Wfdc17). Moreover, ApoA4 deficiency resulted in higher Lgals3, Ctss, Fcgr2b, Spp1, Cxcl2, and Elane levels and lower Nr4a1 levels in hepatic immune cells. These genes were consistent with human NAFLD-associated marker genes linked to disease severity. The expression of NE and IL-1β in granulocytes and macrophages as key ApoA4 targets were validate in the presence or absence of ApoA4 by immunostaining. The scRNA-seq data analyses revealed reprogramming of liver immune cells resulted from ApoA4 deficiency. We uncovered that the emergence of ApoA4-associated immune subsets (namely Cxcl9+ macrophage, Cxcl2+ macrophage and Wfdc17+ granulocyte), pathways, and NAFLD-related marker genes may promote the development of NAFL. These findings may provide novel therapeutic targets for NAFL and the foundations for further studying the effects of ApoA4 on immune cells in various diseases.

Establishment and validation of a cholesterol metabolism-related prognostic signature for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) represents the most important type of liver cancer, the 5-year survival rate for advanced HCC is 2%. The heterogeneity of HCC makes previous models fail to achieve satisfactory results. The role of Cholesterol-based metabolic reprogramming in cancer has attracted more and more attention. In this study, we screened cholesterol metabolism-related genes (CMRGs) based on a systematical analysis from TCGA and GEO database. Then, we constructed a prognostic signature based on the screened 5 CMRGs: FDPS, FABP5, ANXA2, ACADL and HMGCS2. The clinical value of the five CMRGs was validated by TCGA database and HPA database. HCC patients were assigned to the high-risk and low-risk groups on the basis of median risk score calculated by the five CMRGs. We evaluated the signature in TCGA database and validated in ICGC database. The results revealed that the prognostic signature had good prognostic performance, even among different clinicopathological subgroups. The function analysis linked CMRGs with KEGG pathway, such as cell adhesion molecules, drug metabolism-cytochrome P450 and other related pathways. In addition, patients in the high-risk group exhibited characteristics of high TP53 mutation, high immune checkpoints expression and high immune cell infiltration. Furthermore, based on the prognostic signature, we identified 25 most significant small molecule drugs as potential drugs for HCC patients. Finally, a nomogram combined risk score and TNM stage was constructed. These results indicated our prognostic signature has an excellent prediction performance. This study is expected to provide a potential diagnostic and therapeutic strategies for HCC.

Proteomic Characterization of Atherosclerotic Lesions In Situ Using Percutaneous Coronary Intervention Angioplasty Balloons-Brief Report

BACKGROUND

Materials extracted from atherosclerotic arteries can disclose data about the molecular pathology of cardiovascular disease, but obtaining such samples is complex and requires invasive surgery. To overcome this barrier, this study investigated whether angioplasty balloons inflated during standard percutaneous coronary interventions retain proteins from treated (dilated) atherosclerotic lesions and whether proteomic analysis of this material could provide data on lesion protein profiles and distinguish between patients with stable and unstable coronary artery disease.

METHODS

Patients with ST-segment-elevation myocardial infarction and stable angina pectoris were subjected to routine percutaneous coronary interventions. All angioplasty balloons inflated in a coronary artery were collected. Proteins retained on the balloons were extracted and analyzed using shotgun proteomic analysis.

RESULTS

Proteomics identified and quantified 1365 unique proteins captured on percutaneous coronary intervention balloons. Control balloons inflated in the ascending aorta showed minimal nonspecific protein binding, indicating specificity to the luminal region of atherosclerotic lesions of the diseased artery wall. Clustering and principal component analyses showed that ST-segment-elevation myocardial infarction and stable angina pectoris subjects could be separated by variations in protein content and abundance. We identified 206 proteins as differentially abundant between ST-segment-elevation myocardial infarction and stable angina pectoris subjects. Pathway analysis indicated several enriched processes in the ST-segment-elevation myocardial infarction group involved in neutrophil-mediated immunity and platelet activation.

CONCLUSIONS

Disease-related proteins from coronary artery lesions adhere to angioplasty balloons and constitute a source of material for proteomic analysis. This approach can identify proteins and processes occurring in unstable coronary atherosclerotic lesions and suggest novel therapeutic approaches.

Phthalate monoesters act through peroxisome proliferator-activated receptors in the mouse ovary

Widespread use of phthalates as solvents and plasticizers leads to everyday human exposure. The mechanisms by which phthalate metabolites act as ovarian toxicants are not fully understood. Thus, this study tested the hypothesis that the phthalate metabolites monononyl phthalate (MNP), monoisononyl phthalate (MiNP), mono(2-ethylhexyl) phthalate (MEHP), monobenzyl phthalate (MBzP), monobutyl phthalate (MBP), monoisobutyl phthalate (MiBP), and monoethyl phthalate (MEP) act through peroxisome proliferator-activated receptors (PPARs) in mouse granulosa cells. Primary granulosa cells were isolated from CD-1 mice and cultured with vehicle control (dimethyl sulfoxide) or MNP, MiNP, MEHP, MBzP, MBP, MiBP, or MEP (0.4-400 μM) for 24 h. Following culture, qPCR was performed for known PPAR targets, Fabp4 and Cd36. Treatment with the phthalate metabolites led to significant changes in Fabp4 and Cd36 expression relative to control in dose-dependent or nonmonotonic fashion. Primary granulosa cell cultures were also transfected with a DNA plasmid containing luciferase expressed under the control of a consensus PPAR response element. MNP, MiNP, MEHP, and MBzP caused dose-dependent changes in expression of luciferase, indicating the presence of functional endogenous PPAR receptors in the granulosa cells that respond to phthalate metabolites. The effects of phthalate metabolites on PPAR target genes were inhibited in most of the cultures by co-treatment with the PPAR-γ inhibitor, T0070907, or with the PPAR-α inhibitor, GW6471. Collectively, these data suggest that some phthalate metabolites may act through endogenous PPAR nuclear receptors in the ovary and that the differing structures of the phthalates result in different levels of activity.

The Biological Functions and Regulatory Mechanisms of Fatty Acid Binding Protein 5 in Various Diseases

In recent years, fatty acid binding protein 5 (FABP5), also known as fatty acid transporter, has been widely researched with the help of modern genetic technology. Emerging evidence suggests its critical role in regulating lipid transport, homeostasis, and metabolism. Its involvement in the pathogenesis of various diseases such as metabolic syndrome, skin diseases, cancer, and neurological diseases is the key to understanding the true nature of the protein. This makes FABP5 be a promising component for numerous clinical applications. This review has summarized the most recent advances in the research of FABP5 in modulating cellular processes, providing an in-depth analysis of the protein's biological properties, biological functions, and mechanisms involved in various diseases. In addition, we have discussed the possibility of using FABP5 as a new diagnostic biomarker and therapeutic target for human diseases, shedding light on challenges facing future research.

FABP5 Deficiency Impairs Mitochondrial Function and Aggravates Pathological Cardiac Remodeling and Dysfunction

Fatty acid-binding protein 5 (FABP5) is an important member of the FABP family and plays a vital role in the metabolism of fatty acids. However, few studies have examined the role of FABP5 in pathological cardiac remodeling and heart failure. The aim of this study was to explore the role of FABP5 in transverse aortic constriction (TAC)-induced pathological cardiac remodeling and dysfunction in mice. Quantitative RT-PCR (qRT-PCR) and western blotting (WB) analysis showed that the levels of FABP5 mRNA and protein, respectively, were upregulated in hearts of the TAC model. Ten weeks after TAC in FABP5 knockout and wild type control mice, echocardiography, histopathology, qRT-PCR, and WB demonstrated that FABP5 deficiency aggravated cardiac injury (both cardiac hypertrophy and fibrosis) and dysfunction. In addition, transmission electron microscopy, ATP detection, and WB revealed that TAC caused severe impairment to mitochondria in the hearts of FABP5-deficient mice compared with that in control mice. When FABP5 was downregulated by siRNA in primary mouse cardiac fibroblasts, FABP5 silencing increased oxidative stress, reduced mitochondrial respiration, and increased the expression of myofibroblast activation marker genes in response to treatment with transforming growth factor-β. Our findings demonstrate that FABP5 deficiency aggravates cardiac pathological remodeling and dysfunction by damaging cardiac mitochondrial function.

Identification of differentially expressed proteins involved in fetal scarless wound healing using a rat model of cleft lip

In early pregnancy, fetal skin wounds can heal quickly and undergo a transition period from scarless healing to scar formation. The aim of the present study was to identify potential biomarkers associated with scarless repair of cleft lips, in order to determine the intrinsic factors leading to scar formation in embryonic tissue. A stable model of cleft lip was established using microsurgery by constructing a wedge-shaped cleft lip-like defect in fetal rats at gestational age (GA) 16.5 and GA18.5. The GA16.5 and GA18.5 groups were used to model scarless healing and scar formation, respectively. The fetuses were returned to the uterus following surgery, then removed 72 h after the procedure. Macroscopic observation of the cleft defect and histological examination were carried out. Reverse transcription-quantitative (RT-q) PCR and parallel reaction monitoring (PRM) were used to detect mRNA and protein expression levels, respectively. The upper-left lip completely healed 72 h after surgery in the GA16.5 group of fetal rats. However, this was not the case in the GA18.5 group. Histological examination indicated new follicles visible under the epidermis of the scarless group (GA16.5). Scarring was visible on the upper-left cleft lip wound of the fetal rats in the GA18.5 group. The expression of some growth and pro-inflammatory factors, including TNF-α, were also different between two groups. Label-free quantification was used to identified differentially expressed proteins and five differentially expressed proteins (Smad4, Fabp5, S100a4, S100a8 and S100a9) were identified. The relative expression of these molecules at the mRNA and protein levels were measured using RT-qPCR and PRM. These molecules may represent potential biomarkers for the scarless repair of fetal rat cleft lip wounds.

Serum fatty acid-binding protein 5 is a significant factor in hepatocellular carcinoma progression independent of tissue expression level

Fatty acid-binding protein 5 (FABP5) is highly expressed in hepatocellular carcinoma (HCC) tissues and is related to HCC progression. In this study, we analyzed the potential of serum FABP5 (sFABP5) as a tumor marker in HCC and its clinical significance in HCC progression. We compared the sFABP5 concentration in patients with HCC (HCC group) with that of patients with hepatitis without HCC (hepatitis group). Moreover, we measured the FABP5 expression levels in resected HCC tissues (tFABP5) and analyzed their relationship with sFABP5. We also performed cell-based assays using FABP5 knockout and overexpressing HCC cell lines to analyze the effect of extrinsic FABP5 (exFABP5) on HCC cells. We showed that sFABP5 was not a useful tumor marker for HCC, as HCC and sFABP5 were not correlated. However, sFABP5 and tFABP5 significantly correlated with survival after surgery for HCC, while sFABP5 and tFABP5 were independent of each other. In cell-based assays, exFABP5 was taken up by HCC cell lines and positively affected cell survival under glucose-depleted conditions by complementing the endogenous FABP5 function. In conclusion, sFABP5 had a significant impact on HCC progression irrespective of tFABP5 by augmenting cell viability under glucose-depleted conditions. As tFABP5 and sFABP5 are important factors that are independent of each other in HCC progression, both of them should be considered independently in improving the prognosis of patients with HCC.

Differential DNA methylation profile in infants born small-for-gestational-age: association with markers of adiposity and insulin resistance from birth to age 24 months

INTRODUCTION

Prenatal growth restraint followed by rapid postnatal weight gain increases lifelong diabetes risk. Epigenetic dysregulation in critical windows could exert long-term effects on metabolism and confer such risk.

RESEARCH DESIGN AND METHODS

We conducted a genome-wide DNA methylation profiling in peripheral blood from infants born appropriate-for-gestational-age (AGA, n=30) or small-for-gestational-age (SGA, n=21, with postnatal catch-up) at age 12 months, to identify new genes that may predispose to metabolic dysfunction. Candidate genes were validated by bisulfite pyrosequencing in the entire cohort. All infants were followed since birth; cord blood methylation profiling was previously reported. Endocrine-metabolic variables and body composition (dual-energy X-ray absorptiometry) were assessed at birth and at 12 and 24 months.

RESULTS

GPR120 (cg14582356, cg01272400, cg23654127, cg03629447), NKX6.1 (cg22598426, cg07688460, cg17444738, cg12076463, cg10457539), CPT1A (cg14073497, cg00941258, cg12778395) and IGFBP 4 (cg15471812) genes were hypermethylated (GPR120, NKX6.1 were also hypermethylated in cord blood), whereas CHGA (cg13332653, cg15480367, cg05700406), FABP5 (cg00696973, cg10563714, cg16128701), CTRP1 (cg19231170, cg19472078, cg0164309, cg07162665, cg17758081, cg18996910, cg06709009), GAS6 (N/A), ONECUT1 (cg14217069, cg02061705, cg26158897, cg06657050, cg15446043) and SLC2A8 (cg20758474, cg19021975, cg11312566, cg12281690, cg04016166, cg03804985) genes were hypomethylated in SGA infants. These genes were related to β-cell development and function, inflammation, and glucose and lipid metabolism and associated with body mass index, body composition, and markers of insulin resistance at 12 and 24 months.

CONCLUSION

In conclusion, at 12 months, abnormal methylation of GPR120 and NKX6.1 persists and new epigenetic marks further involved in adipogenesis and energy homeostasis arise in SGA infants. These abnormalities may contribute to metabolic dysfunction and diabetes risk later in life.

New Classification of Macrophages in Plaques: a Revolution

PURPOSE

Macrophages play vital roles in the development of atherosclerosis in responding to lipid accumulation and inflammation. Macrophages were classified as inflammatory (M1) and alternatively activated (M2) macrophage types based on results of in vitro experiments. On the other hand, the composition of macrophages in vivo is more complex and remains unresolved. This review summarizes the transcriptional variations of macrophages in atherosclerosis plaques that were discovered by single-cell RNA sequencing (scRNA-seq) to better understand their contribution to atherosclerosis.

RECENT FINDINGS

ScRNA-seq provides a more detailed transcriptional landscape of macrophages in atherosclerosis, which challenges the traditional view. By mining the data of GSE97310, we discovered the transcriptional variations of macrophages in LDLR^-/- mice that were fed with high-fat diet (HFD) for 11 and 20 weeks. Cells were represented in a two-dimensional tSNE plane and clusters were identified and annotated via Seurat and SingleR respectively, which were R toolkits for single-cell genomics. The results showed that in healthy conditions, Trem2^hi (high expression of triggering receptors expressed on myeloid cells 2)-positive, inflammatory, and resident-like macrophages make up 68%, 18%, and 6% of total macrophages respectively. When mice were fed with HFD for 11 weeks, Trem2^hi, monocytes, and monocyte-derived dendritic cells take possession of 40%, 18%, and 17% of total macrophages respectively. After 20 weeks of HFD feeding, Trem2^hi, inflammatory, and resident-like macrophages occupied 12%, 37%, and 35% of total macrophages respectively. The phenotypes of macrophages are very different from the previous studies. In general, Trem2^hi macrophages are the most abundant population in healthy mice, while the proportion of monocytes increases after 11 weeks of HFD. Most importantly, inflammatory and resident-like macrophages make up 70% of the macrophage populations after 20 weeks of HFD. These strongly indicate that inflammatory and resident-like macrophages promote the progression of atherosclerosis plaques.

Independent and Distinct Associations of FABP4 and FABP5 With Metabolic Parameters in Type 2 Diabetes Mellitus

Objective: Among fatty acid-binding proteins (FABPs), secreted forms of FABP4 and FABP5, which are expressed in adipocytes and macrophages, act as bioactive molecules. We investigated concentrations of FABP4 and FABP5 in patients with type 2 diabetes mellitus. Methods: As a sub-analysis study of the Randomized Evaluation of Anagliptin vs. Sitagliptin On low-density lipoproteiN cholesterol in diabetes (REASON) trial, 256 patients (male/female: 146/110, age: 68 ± 10 years) with type 2 diabetes mellitus and dyslipidemia who were receiving statin therapy were recruited. Patients who had been treated with a thiazolidinedione were excluded. Results: Several drugs which may modulate FABP4 levels including statins, dipeptidyl peptidase-4 inhibitors and angiotensin II receptor blockers had been administered in 100, 81, and 51% of the recruited patients, respectively. The level of FABP4, but not that of FABP5, was significantly higher in females than in males. Multivariable linear regression analysis demonstrated that waist circumference (β = 0.21), estimated glomerular filtration rate (β = -0.31), triglycerides (β = 0.16), and FABP5 (β = 0.39) were independent predictors of FABP4 level after adjusting age and sex. On the other hand, FABP5 level was independently associated with levels of FABP4 (β = 0.57) and high-density lipoprotein (HDL) cholesterol (β = -0.12). Conclusions: Concentrations of FABP4 and FABP5 are independent predictors of each other in patients with type 2 diabetes mellitus. There are distinct independent associations of FABP4 with renal dysfunction, adiposity and hypertriglyceridemia and there is a distinct independent association of FABP5 with a low HDL cholesterol level in type 2 diabetic patients with dyslipidemia at high risks for cardiovascular disease who are receiving statin therapy.

Macrophage fatty acid metabolism and atherosclerosis: The rise of PUFAs

Among the pathways involved in the regulation of macrophage functions, the metabolism of unsaturated fatty acids is central. Indeed, unsaturated fatty acids act as precursors of bioactive molecules such as prostaglandins, leukotrienes, resolvins and related compounds. As components of phospholipids, they have a pivotal role in cell biology by regulating membrane fluidity and membrane-associated cellular processes. Finally, polyunsaturated fatty acids (PUFAs) are also endowed with ligand properties for numerous membrane or nuclear receptors. Although myeloid cells are dependent on the metabolic context for the uptake of essential FAs, recent studies showed that these cells autonomously handle the synthesis of n-3 and n-6 long chain PUFAs such as arachidonic acid and eicosapentaenoic acid. Moreover, targeting PUFA metabolism in macrophages influences pathological processes, including atherosclerosis, by modulating macrophage functions. Omics evidence also supports a role for macrophage PUFA metabolism in the development of cardiometabolic diseases in humans. Currently, there is a renewed interest in the role of n-3/n-6 PUFAs and their oxygenated derivatives in the onset of atherosclerosis and plaque rupture. Purified n-3 FA supplementation appears as a potential strategy in the treatment and prevention of cardiovascular diseases. In this context, the ability of immune cells to handle and to synthesize very long chain PUFA must absolutely be integrated and better understood.

Fatty Acid-Binding Protein 4 in Cardiovascular and Metabolic Diseases

Fatty acid-binding proteins (FABPs), a family of lipid chaperones, contribute to systemic metabolic regulation via several lipid signaling pathways. Fatty acid-binding protein 4 (FABP4), known as adipocyte FABP (A-FABP) or aP2, is mainly expressed in adipocytes and macrophages and plays important roles in the development of insulin resistance and atherosclerosis in relation to metabolically driven low-grade and chronic inflammation, referred to as ‘metaflammation’. FABP4 is secreted from adipocytes in a non-classical pathway associated with lipolysis and acts as an adipokine for the development of insulin resistance and atherosclerosis. Circulating FABP4 levels are associated with several aspects of metabolic syndrome and cardiovascular disease. Ectopic expression and function of FABP4 in cells and tissues are also related to the pathogenesis of several diseases. Pharmacological modification of FABP4 function by specific inhibitors, neutralizing antibodies or antagonists of unidentified receptors would be novel therapeutic strategies for several diseases, including obesity, diabetes mellitus, atherosclerosis and cardiovascular disease. Significant roles of FABP4 as a lipid chaperone in physiological and pathophysiological conditions and the possibility of FABP4 being a therapeutic target for metabolic and cardiovascular diseases are discussed in this review.

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.

Circulating Fatty Acid-Binding Protein 4 Concentration Predicts the Progression of Carotid Atherosclerosis in a General Population Without Medication

BACKGROUND

Fatty acid-binding protein 4 (FABP4), which is expressed in both adipocytes and macrophages, is secreted from the cells and acts as an adipokine. An elevated circulating FABP4 level is associated with insulin resistance and atherosclerosis.

METHODS AND RESULTS

We investigated the causative association between FABP4 level and progression of atherosclerosis in subjects of the Tanno-Sobetsu Study, a population-based cohort. In 281 subjects without medication (male/female: 109/172) in the year 2010 or 2013, the carotid intima-media thickness (CIMT) assessed using carotid ultrasonography was significantly correlated with age, adiposity, blood pressure, renal dysfunction and levels of cholesterol, triglycerides, fasting glucose, HbA1c and FABP4 (r=0.331, P<0.001). Multiple regression analysis demonstrated that age, sex and FABP4 concentration were independent predictors of CIMT. A total of 78 (male/female: 29/49) of the 156 subjects in 2010 underwent carotid ultrasonography again in 2013. The change in CIMT each year during that 3-year period (mean±SD: 3.8±22.3 µm/year) was positively correlated with basal levels of high-sensitivity C-reactive protein (hsCRP) (r=0.231, P=0.046) and FABP4 (r=0.267, P=0.018) in 2010. After adjustment for age, sex and hsCRP level, the basal FABP4 level was independently associated with the change in CIMT per year.

CONCLUSIONS

FABP4 concentration is an independent predictor of the progression of carotid atherosclerosis.