The coronary artery disease-associated gene C6ORF105 is expressed in human macrophages under the transcriptional control of PPARγ

Adtrp regulates thermogenic activity of adipose tissue via mediating the secretion of S100b

Brown and beige adipose tissues dissipate chemical energy in the form of heat to maintain your body temperature in cold conditions. The impaired function of these tissues results in various metabolic diseases in humans and mice. By bioinformatical analyses, we identified a functional thermogenic regulator of adipose tissue, Androgen-dependent tissue factor pathway inhibitor [TFPI]-regulating protein (Adtrp), which was significantly overexpressed in and functionally activated the mature brown/beige adipocytes. Hereby, we knocked out Adtrp in mice which led to multiple abnormalities in thermogenesis, metabolism, and maturation of brown/beige adipocytes causing excess lipid accumulation in brown adipose tissue (BAT) and cold intolerance. The capability of thermogenesis in brown/beige adipose tissues could be recovered in Adtrp KO mice upon direct β3-adrenergic receptor (β3-AR) stimulation by CL316,243 treatment. Our mechanistic studies revealed that Adtrp by binding to S100 calcium-binding protein b (S100b) indirectly mediated the secretion of S100b, which in turn promoted the β3-AR mediated thermogenesis via sympathetic innervation. These results may provide a novel insight into Adtrp in metabolism via regulating the differentiation and thermogenesis of adipose tissues in mice.

Androgen-dependent tissue factor pathway inhibitor regulating protein: a review of its peripheral actions and association with cardiometabolic diseases

The first genome-wide association study on coronary artery disease (CAD) in the Han Chinese population identified C6orf105 as a susceptibility gene. The C6orf105 gene was later found to encode for a protein that regulates tissue factor pathway inhibitor (TFPI) expression in endothelial cells in an androgen-dependent manner, and the novel protein was thus termed androgen-dependent TFPI-regulating protein (ADTRP). Since the identification of ADTRP, there have been several studies associating genetic variants on the ADTRP gene with CAD risk, as well as research providing mechanistic insights on this novel protein and its functional role. ADTRP is a membrane protein, whose expression is upregulated by androgen, GATA-binding protein 2, oxidized low-density lipoprotein, peroxisome proliferator-activated receptors, and low-density lipoprotein receptors. ADTRP regulates multiple downstream targets involved in coagulation, inflammation, endothelial function, and vascular integrity. In addition, ADTRP functions as a fatty acid esters of hydroxy fatty acid (FAHFA)-specific hydrolase that is involved in energy metabolism. Current evidence suggests that ADTRP may play a role in the pathogenesis of atherosclerosis, CAD, obesity, and metabolic disorders. This review summarizes the current literature on ADTRP, with a focus on the peripheral actions of ADTRP, including expression, genetic variations, signaling pathways, and function. The evidence linking ADTRP and cardiometabolic diseases will also be discussed.

Molecular Phylogenetic Analysis of the AIG Family in Vertebrates

Androgen-inducible genes (AIGs), which can be regulated by androgen level, constitute a group of genes characterized by the presence of the AIG/FAR-17a domain in its protein sequence. Previous studies on AIGs demonstrated that one member of the gene family, AIG1, is involved in many biological processes in cancer cell lines and that ADTRP is associated with cardiovascular diseases. It has been shown that the numbers of AIG paralogs in humans, mice, and zebrafish are 2, 2, and 3, respectively, indicating possible gene duplication events during vertebrate evolution. Therefore, classifying subgroups of AIGs and identifying the homologs of each AIG member are important to characterize this novel gene family further. In this study, vertebrate AIGs were phylogenetically grouped into three major clades, ADTRP, AIG1, and AIG-L, with AIG-L also evident in an outgroup consisting of invertebrsate species. In this case, AIG-L, as the ancestral AIG, gave rise to ADTRP and AIG1 after two rounds of whole-genome duplications during vertebrate evolution. Then, the AIG family, which was exposed to purifying forces during evolution, lost or gained some of its members in some species. For example, in eutherians, Neognathae, and Percomorphaceae, AIG-L was lost; in contrast, Salmonidae and Cyprinidae acquired additional AIG copies. In conclusion, this study provides a comprehensive molecular phylogenetic analysis of vertebrate AIGs, which can be employed for future functional characterization of AIGs.

Hepatic ADTRP overexpression does not influence lipid and glucose metabolism

The peroxisome proliferator activated receptors (PPARs) are a group of transcription factors belonging to the nuclear receptor superfamily. Since most target genes of either PPARs are implicated in lipid and glucose metabolism, regulation by PPARs could be used as a screening tool to identify novel genes involved in lipid or glucose metabolism. Here, we identify Adtrp, a serine hydrolase enzyme that was reported to catalyze the hydrolysis of fatty acid esters of hydroxy fatty acids (FAHFAs), as a novel PPAR-regulated gene. Adtrp was significantly upregulated by PPARα activation in mouse primary hepatocytes, liver slices, and whole liver. In addition, Adtrp was upregulated by PPARγ activation in 3L3-L1 adipocytes and in white adipose tissue. ChIP-SEQ identified a strong PPAR binding site in the immediate upstream promoter of the Adtrp gene. Adenoviral-mediated hepatic overexpression of Adtrp in diet-induced obese mice caused a modest increase in plasma non-esterified fatty acids but did not influence diet-induced obesity, liver triglyceride levels, liver lipidomic profiles, liver transcriptomic profiles, and plasma cholesterol, triglycerides, glycerol, and glucose levels. Moreover, hepatic Adtrp overexpression did not lead to significant changes in FAHFA levels in plasma or liver and did not influence glucose and insulin tolerance. Finally, hepatic overexpression of Adtrp did not influence liver triglycerides and levels of plasma metabolites after a 24h fast. Taken together, our data suggest that despite being a PPAR-regulated gene, hepatic Adtrp does not seem to play a major role in lipid and glucose metabolism and does not regulate FAHFA levels.

Insights into the Functional Role of ADTRP (Androgen-Dependent TFPI-Regulating Protein) in Health and Disease

The novel protein ADTRP, identified and described by us in 2011, is androgen-inducible and regulates the expression and activity of Tissue Factor Pathway Inhibitor, the major inhibitor of the Tissue Factor-dependent pathway of coagulation on endothelial cells. Single-nucleotide polymorphisms in ADTRP associate with coronary artery disease and myocardial infarction, and deep vein thrombosis/venous thromboembolism. Some athero-protective effects of androgen could exert through up-regulation of ADTRP expression. We discovered a critical role of ADTRP in vascular development and vessel integrity and function, manifested through Wnt signaling-dependent regulation of matrix metalloproteinase-9. ADTRP also hydrolyses fatty acid esters of hydroxy-fatty acids, which have anti-diabetic and anti-inflammatory effects and can control metabolic disorders. Here we summarize and analyze the knowledge on ADTRP and try to decipher its functions in health and disease.

Detection of ADTRP in circulation and its role as a novel biomarker for coronary artery disease

Androgen dependent tissue factor pathway inhibitor regulating protein (ADTRP) is a novel protein associated with coronary artery disease (CAD) susceptibility, and reduced mRNA expression of ADTRP was shown to be associated with increased CAD risk. This study aimed to determine and compare circulating ADTRP levels between CAD patients and controls, and to test the performance of plasma ADTRP as a biomarker for CAD. We measured plasma ADTRP, tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and high sensitivity-C reactive protein (hs-CRP) levels in 362 CAD patients, 150 angiographically negative CAD controls, and 83 healthy adults with no known clinical or medical conditions using commercial ELISA. Statistical analyses were performed using receiver operator characteristic (ROC) curves, quantile regression and logistic regression, with adjustments for age, gender, ethnicity and BMI. CAD patients had significantly lower plasma ADTRP levels 1,545 (1,087–2,408) pg/ml as compared to CAD controls 2,259 (1,533–3,778) pg/ml and healthy adults 3,904 (2,732–5,463) pg/ml. Plasma ADTRP outperformed the other three inflammatory biomarkers (TNF-α, IL-6 and hs-CRP) for CAD (Area under ROC curve: 0.67, Odds ratio (OR): 0.907). Our study has shown for the first time that ADTRP is present in circulation, and that plasma ADTRP may be a novel independent biomarker for CAD.

ADTRP regulates TFPI expression via transcription factor POU1F1 involved in coronary artery disease

Genomic variants in both ADTRP and TFPI genes are associated with risk of coronary artery disease (CAD). ADTRP regulates TFPI expression and endothelial cell functions involved in the initiation of atherosclerotic CAD. ADTRP also specifies primitive myelopoiesis and definitive hematopoiesis by upregulating TFPI expression. However, the underlying molecular mechanism is unknown. Here we show that transcription factor POU1F1 is the key by which ADTRP regulates TFPI expression. Luciferase reporter assays, chromatin-immunoprecipitation (ChIP) and electrophoretic mobility shift assay (EMSA) in combination with analysis of large and small deletions of the TFPI promoter/regulatory region were used to identify the molecular mechanism by which ADTRP regulates TFPI expression. Genetic association was assessed using case-control association analysis and phenome-wide association analysis (PhenGWA). ADTRP regulates TFPI expression at the transcription level in a dose-dependent manner. The ADTRP-response element was localized to a 50 bp region between -806 bp and -756 bp upstream of TFPI transcription start site, which contains a binding site for POU1F1. Deletion of POU1F1-binding site or knockdown of POU1F1 expression abolished ADTRP-mediated transcription of TFPI. ChIP and EMSA demonstrated that POU1F1 binds to the ADTRP response element. Genetic analysis identified significant association between POU1F1 variants and risk of CAD. PhenGWA identified other phenotypic traits associated with the ADTRP-POU1F1-TFPI axis such as lymphocyte count (ADTRP), waist circumference (TFPI), and standing height (POU1F1). These data identify POU1F1 as a transcription factor that regulates TFPI transcription in response to ADTRP, and link POU1F1 variants to risk of CAD for the first time.

Biomarkers from circulating neutrophil transcriptomes have potential to detect unruptured intracranial aneurysms

BACKGROUND

Intracranial aneurysms (IAs) are dangerous because of their potential to rupture and cause deadly subarachnoid hemorrhages. Previously, we found significant RNA expression differences in circulating neutrophils between patients with unruptured IAs and aneurysm-free controls. Searching for circulating biomarkers for unruptured IAs, we tested the feasibility of developing classification algorithms that use neutrophil RNA expression levels from blood samples to predict the presence of an IA.

METHODS

Neutrophil RNA extracted from blood samples from 40 patients (20 with angiography-confirmed unruptured IA, 20 angiography-confirmed IA-free controls) was subjected to next-generation RNA sequencing to obtain neutrophil transcriptomes. In a randomly-selected training cohort of 30 of the 40 samples (15 with IA, 15 controls), we performed differential expression analysis. Significantly differentially expressed transcripts (false discovery rate < 0.05, fold change ≥ 1.5) were used to construct prediction models for IA using four well-known supervised machine-learning approaches (diagonal linear discriminant analysis, cosine nearest neighbors, nearest shrunken centroids, and support vector machines). These models were tested in a testing cohort of the remaining 10 neutrophil samples from the 40 patients (5 with IA, 5 controls), and model performance was assessed by receiver-operating-characteristic (ROC) curves. Real-time quantitative polymerase chain reaction (PCR) was used to corroborate expression differences of a subset of model transcripts in neutrophil samples from a new, separate validation cohort of 10 patients (5 with IA, 5 controls).

RESULTS

The training cohort yielded 26 highly significantly differentially expressed neutrophil transcripts. Models using these transcripts identified IA patients in the testing cohort with accuracy ranging from 0.60 to 0.90. The best performing model was the diagonal linear discriminant analysis classifier (area under the ROC curve = 0.80 and accuracy = 0.90). Six of seven differentially expressed genes we tested were confirmed by quantitative PCR using isolated neutrophils from the separate validation cohort.

CONCLUSIONS

Our findings demonstrate the potential of machine-learning methods to classify IA cases and create predictive models for unruptured IAs using circulating neutrophil transcriptome data. Future studies are needed to replicate these findings in larger cohorts.

Identification of a new adtrp1-tfpi regulatory axis for the specification of primitive myelopoiesis and definitive hematopoiesis

A genomic variant in the human ADTRP [androgen-dependent tissue factor (TF) pathway inhibitor (TFPI) regulating protein] gene increases the risk of coronary artery disease, the leading cause of death worldwide. TFPI is the TF pathway inhibitor that is involved in coagulation. Here, we report that adtrp and tfpi form a regulatory axis that specifies primitive myelopoiesis and definitive hematopoiesis, but not primitive erythropoiesis or vasculogenesis. In zebrafish, there are 2 paralogues for adtrp (i.e., adtrp1 and adtrp2). Knockdown of adtrp1 expression inhibits the specification of hemangioblasts, as shown by decreased expression of the hemangioblast markers, etsrp, fli1a, and scl; blocks primitive hematopoiesis, as shown by decreased expression of pu.1, mpo, and l-plastin; and disrupts the specification of hematopoietic stem cells (definitive hematopoiesis), as shown by decreased expression of runx1 and c-myb However, adtrp1 knockdown does not affect erythropoiesis during primitive hematopoiesis (no effect on gata1 or h-bae1) or vasculogenesis (no effect on kdrl, ephb2a, notch3, dab2, or flt4). Knockdown of adtrp2 expression does not have apparent effects on all markers tested. Knockdown of adtrp1 reduced the expression of tfpi, and hematopoietic defects in adtrp1 morphants were rescued by tfpi overexpression. These data suggest that the regulation of tfpi expression is one potential mechanism by which adtrp1 regulates primitive myelopoiesis and definitive hematopoiesis.-Wang, L., Wang, X., Wang, L., Yousaf, M., Li, J., Zuo, M., Yang, Z., Gou, D., Bao, B., Li, L., Xiang, N., Jia, H., Xu, C., Chen, Q., Wang, Q. K. Identification of a new adtrp1-tfpi regulatory axis for the specification of primitive myelopoiesis and definitive hematopoiesis.

Androgen inhibits key atherosclerotic processes by directly activating ADTRP transcription

Low androgen levels are associated with an increased risk of coronary artery disease (CAD), thrombosis and myocardial infarction (MI), suggesting that androgen has a protective role. However, little is known about the underlying molecular mechanism. Our genome-wide association study identified the ADTRP gene encoding the androgen-dependent TFPI regulating protein as a susceptibility gene for CAD and MI. The expression level of ADTRP was regulated by androgen, but the molecular mechanism is unknown. In this study, we identified the molecular mechanism by which androgen regulates ADTRP expression and tested the hypothesis that androgen plays a protective role in cardiovascular disease by activating ADTRP expression. Luciferase assays with an ADTRP promoter luciferase reporter revealed that androgen regulated ADTRP transcription in a dose- and time-dependent manner, and the effect was abolished by three different androgen inhibitors, including pyrvinium pamoate, bicalutamide, and cyproterone acetate. Chromatin-immunoprecipitation showed that the androgen receptor bound to a half androgen response element (ARE, TGTTCT) located at +324bp from the ADTRP transcription start site. The ARE is required for concentration-dependent transcriptional activation of ADTRP. HL-60 monocyte adhesion to EAhy926 endothelial cells (ECs) and transmigration across the EC layer, the two processes critical to development of CAD and MI, were inhibited by androgen, but the effect was rescued by ADTRP siRNA and exacerbated by overexpression of ADTRP and its downstream genes PIK3R3 and MIA3. These data suggest that one molecular mechanism by which androgen confers protection against CAD is stimulation of ADTRP expression.

Identification of a molecular signaling gene-gene regulatory network between GWAS susceptibility genes ADTRP and MIA3/TANGO1 for coronary artery disease

Coronary artery disease (CAD) is the leading cause of death worldwide. GWAS have identified >50 genomic loci for CAD, including ADTRP and MIA3/TANGO1. However, it is important to determine whether the GWAS genes form a molecular network. In this study, we have uncovered a novel molecular network between ADTRP and MIA3/TANGO1 for the pathogenesis of CAD. We showed that knockdown of ADTRP expression markedly down-regulated expression of MIA3/TANGO1. Mechanistically, ADTRP positively regulates expression of PIK3R3 encoding the regulatory subunit 3 of PI3K, which leads to activation of AKT, resulting in up-regulation of MIA3/TANGO1. Both ADTRP and MIA3/TANGO1 are involved in endothelial cell (EC) functions relevant to atherosclerosis. Knockdown of ADTRP expression by siRNA promoted oxidized-LDL-mediated monocyte adhesion to ECs and transendothelial migration of monocytes, inhibited EC proliferation and migration, and increased apoptosis, which was reversed by expression of constitutively active AKT1 and MIA3/TANGO1 overexpression, while the over-expression of ADTRP in ECs blunted these processes. Knockdown of MIA3/TANGO1 expression also promoted monocyte adhesion to ECs and transendothelial migration of monocytes, and vice versa for overexpression of MIA3/TANGO1. We found that ADTRP negatively regulates the levels of collagen VII and ApoB in HepG2 and endothelial cells, which are downstream regulatory targets of MIA3/TANGOI. In conclusion, we have uncovered a novel molecular signaling pathway for the pathogenesis of CAD, which involves a novel gene-gene regulatory network. We show that ADTRP positively regulates PIK3R3 expression, which leads to activation of AKT and up-regulation of MIA3/TANGO1, thereby regulating endothelial cell functions directly relevant to atherosclerosis.

Peroxisome Proliferator-Activated Receptor γ Induces the Expression of Tissue Factor Pathway Inhibitor-1 (TFPI-1) in Human Macrophages

Tissue factor (TF) is the initiator of the blood coagulation cascade after interaction with the activated factor VII (FVIIa). Moreover, the TF/FVIIa complex also activates intracellular signalling pathways leading to the production of inflammatory cytokines. The TF/FVIIa complex is inhibited by the tissue factor pathway inhibitor-1 (TFPI-1). Peroxisome proliferator-activated receptor gamma (PPARγ) is a transcription factor that, together with PPARα and PPARβ/δ, controls macrophage functions. However, whether PPARγ activation modulates the expression of TFP1-1 in human macrophages is not known. Here we report that PPARγ activation increases the expression of TFPI-1 in human macrophages in vitro as well as in vivo in circulating peripheral blood mononuclear cells. The induction of TFPI-1 expression by PPARγ ligands, an effect shared by the activation of PPARα and PPARβ/δ, occurs also in proinflammatory M1 and in anti-inflammatory M2 polarized macrophages. As a functional consequence, treatment with PPARγ ligands significantly reduces the inflammatory response induced by FVIIa, as measured by variations in the IL-8, MMP-2, and MCP-1 expression. These data identify a novel role for PPARγ in the control of TF the pathway.

Coronary artery disease susceptibility gene ADTRP regulates cell cycle progression, proliferation, and apoptosis by global gene expression regulation

The ADTRP gene encodes the androgen-dependent TFPI-regulating protein and is a susceptibility gene for contrary artery disease (CAD). We performed global gene expression profiling for ADTRP knock-down using microarrays in human HepG2 cells. Follow-up real-time RT-PCR analysis demonstrated that ADTRP knock-down regulates a diverse set of genes, including upregulation of seven histone genes, downregulation of multiple cell cycle genes (CCND1, CDK4, and CDKN1A), and upregulation of apoptosis genes (CASP7 and PDCD2) in HepG2 cells and endothelial cells. Consistently, ADTRP increases the number of S phase cells during cell cycle, promotes cell proliferation, and inhibits apoptosis. Our study provides novel insights into the function of ADTRP and biological pathways involving ADTRP, which may be involved in the pathogenesis of CAD.

Association of single nucleotide polymorphism rs2076185 in chromosome 6P24.1 with premature coronary artery diseases in Chinese Han population

OBJECTIVES

To study the association of single nucleotide polymorphism (SNP) rs2076185 in chromosome 6p24.1 with the premature coronary artery diseases (PCAD) in Chinese Han population.

METHODS

A total of 1382 patients were divided into the PCAD group and the control group based on their coronary arteriography (CAG) results. Their SNP rs2076185 were analyzed by the mass-spectrometry. Their allele and genotype frequency in Hardy-Weinberg equilibrium were calculated for assessment. Logistic regression was employed to remove confounding factors and correlate SNP rs2076185 with PCAD.

RESULTS

The allele and genotype frequencies of the control group were in Hardy-Weinberg equilibrium (P > 0.05). The frequencies of allele G of rs2076185 were 54.2% in the PCAD group and 49.5% in the control group. The difference was significant (P = 0.042). The genotype distribution of rs2076185 of the two groups was also significantly different. The univariate analysis showed that the rs2076185 polymorphisms were associated with the PCAD only in the additive model (OR: 0.828, 95% CI: 0.711-0.964, P = 0.014), and in the dominant model (OR: 0.753, 95% CI: 0.591-0.958, P = 0.021). After removing the confounding variables, the rs2076185 polymorphisms was associated with PCAD in the additive model (OR: 0.775, 95% CI: 0.648-0.928, P = 0.005), in the dominant model (OR: 0.698, 95% CI: 0.527-0.925, P = 0.012), and in the recessive model (OR: 0.804, 95% CI: 0.538-0.983, P = 0.038).

CONCLUSION

Allele G of rs2076185 reduces the PCAD risks in Chinese Han population, therefore it could be a coronary artery diseases protective factor in Chinese Han population.

Common Variants in Promoter of ADTRP Associate with Early-Onset Coronary Artery Disease in a Southern Han Chinese Population

The first genome-wide association study for coronary artery disease (CAD) in the Han Chinese population, we reported recently, had identified rs6903956 in gene ADTRP on chromosome 6p24.1 as a novel susceptibility locus for CAD. The risk allele of rs6903956 was associated with decreased mRNA expression of ADTRP. To further study the correlation of ADTRP expression and CAD, in this study we evaluated the associations of eight common variants in the expression-regulating regions of ADTRP with CAD in the Southern Han Chinese population. Rs169790 in 3’UTR, rs2076189 in 5’UTR, four SNPs (rs2076188, rs7753407, rs11966356 and rs1018383) in promoter, and two SNPs (rs3734273, rs80355771) in the last intron of ADTRP were genotyped in 1716 CAD patients and 1572 controls. The correlations between these loci and total or early-onset CAD were investigated. None of these loci was discovered to associate with total CAD (P > 0.05). However, with early-onset CAD, significant both allelic and genotypic associations of rs7753407, rs11966356 and rs1018383 were identified, after adjustment for risk factors of age, gender, hypertension, diabetes, lipid profiles and smoking (adjusted P < 0.05). A haplotype AGCG (constructed by rs2076188, rs7753407, rs11966356 and rs1018383) was identified to protect subjects from early-onset CAD (OR = 0.332, 95% CI = 0.105–0.879, adjusted P = 0.010). Real-time quantitative reverse transcription polymerase chain reaction assay showed that the risk alleles of the associated loci were significantly associated with decreased expression of ADTRP mRNA. Moreover, the average level of ADTRP mRNA expression in early-onset CAD cases was significantly lower than that in controls. Our results provide new evidence supporting the association of ADTRP with the pathogenesis of early-onset CAD.