Hepatic Forkhead Box Protein A3 Regulates ApoA-I (Apolipoprotein A-I) Expression, Cholesterol Efflux, and Atherogenesis

Hepatic FOXA3 overexpression prevents Western diet-induced obesity and MASH through TGR5

Forkhead transcription factor 3 (FOXA3) has been shown to regulate metabolism and development. Hepatic FOXA3 is reduced in obesity and fatty liver disease. However, the role of hepatic FOXA3 in regulating obesity or steatohepatitis remains to be investigated. In this work, C57BL/6 mice were i.v. injected with AAV8-ALB-FOXA3 or the control virus. The mice were then fed a chow or Western diet for 16 weeks. The role of hepatic FOXA3 in energy metabolism and steatohepatitis was investigated. Plasma bile acid composition and the role of Takeda G protein-coupled receptor 5 (TGR5) in mediating the metabolic effects of FOXA3 were determined. Overexpression of hepatic FOXA3 reduced hepatic steatosis in chow-fed mice and attenuated Western diet-induced obesity and steatohepatitis. FOXA3 induced lipolysis and inhibited hepatic genes involved in bile acid uptake, resulting in elevated plasma bile acids. The beneficial effects of hepatic FOXA3 overexpression on Western diet-induced obesity and steatohepatitis were abolished in Tgr5-/- mice. Our data demonstrate that overexpression of hepatic FOXA3 prevents Western diet-induced obesity and steatohepatitis via activation of TGR5.

Microarray analysis identifies human apoA-IMilano and apoA-II as determinants of the liver gene expression related to lipid and energy metabolism

The phenotype of individuals carrying the apolipoprotein A-IMilano (apoA-IM), the mutant form of human apoA-I (apoA-I), is characterized by very low concentrations of HDL and apoA-I, and hypertriglyceridemia. Paradoxically, these subjects are not found to be at increased risk of premature cardiovascular disease compared to controls. Besides, various in vitro and in vivo studies have demonstrated that apoA-IM possesses greater anti-atherosclerotic activity compared to apoA-I. The molecular mechanisms explaining the apoA-IM carrier's phenotype and the apoA-IM higher efficacy are still not fully elucidated. To investigate such mechanisms, we crossed previously generated apoA-I (A-I k-in) or apoA-IM knock-in mice (A-IM k-in) with transgenic mice expressing human apoA-II but lacking murine apoA-I (hA-II) to generate hA-II/A-I k-in, and hA-II/A-IM k-in, respectively. These genetically modified mice completely reproduced the apoA-IM carrier's phenotype, including hypoalphalipoproteinemia and hypertriglyceridemia. Furthermore, by using the microarray methodology, we investigated the intrinsic differences in hepatic gene expression among these k-in mouse lines. The expression of 871, 1,018, 1129 and 764 genes was significantly altered between 1) hA-II/A-I and hA-II/A-IM k-in; 2) A-IM and hA-II/A-IM k-in; 3) A-I and A-IM; 4) A-I and hA-II/A-I k-in liver samples, respectively. Bioinformatics analysis highlighted that the hepatic expression of two genes, Elovl6 and Gatm, related to fatty acid/lipid and energy metabolism, respectively, is influenced by the presence of the apoA-IM natural variant and/or apoA-II.

Characterisation of forkhead box protein A3 as a key transcription factor for hepatocyte regeneration

Background & Aims

Liver regeneration is vital for the recovery of liver function after injury, yet the underlying mechanism remains to be elucidated. Forkhead box protein A3 (FOXA3), a member of the forkhead box family, plays important roles in endoplasmic reticulum stress sensing, and lipid and glucose homoeostasis, yet its functions in liver regeneration are unknown.

Methods

Here, we explored whether Foxa3 regulates liver regeneration via acute and chronic liver injury mice models. We further characterised the molecular mechanism by chromatin immunoprecipitation sequencing and rescue experiments in vivo and in vitro. Then, we assessed the impact of Foxa3 pharmacological activation on progression and termination of liver regeneration. Finally, we confirmed the Foxa3-Cebpb axis in human liver samples.

Results

Foxa3 is dominantly expressed in hepatocytes and cholangiocytes and is induced upon partial hepatectomy (PH) or carbon tetrachloride (CCl4) administration. Foxa3 deficiency in mice decreased cyclin gene levels and delayed liver regeneration after PH, or acute or chronic i.p. CCl4 injection. Conversely, hepatocyte-specific Foxa3 overexpression accelerated hepatocytes proliferation and attenuated liver damage in an CCl4-induced acute model. Mechanistically, Foxa3 directly regulates Cebpb transcription, which is involved in hepatocyte division and apoptosis both in vivo and in vitro. Of note, Cebpb overexpression in livers of Foxa3-deficient mice rescued their defects in cell proliferation and regeneration upon CCl4 treatment. In addition, pharmacological induction of Foxa3 via cardamonin speeded up hepatocyte proliferation after PH, without interfering with liver regeneration termination. Finally, Cebpb and Ki67 levels had a positive correlation with Foxa3 expression in human chronic disease livers.

Conclusions

These data characterise Foxa3 as a vital regulator of liver regeneration, which may represent an essential factor to maintain liver mass after liver injury by governing Cebpb transcription.

Impact and Implications

Liver regeneration is vital for the recovery of liver function after chemical insults or hepatectomy, yet the underlying mechanism remains to be elucidated. Herein, via in vitro and in vivo models and analysis, we demonstrated that Forkhead box protein A3 (FOXA3), a Forkhead box family member, maintained normal liver regeneration progression by governing Cebpb transcription and proposed cardamonin as a lead compound to induce Foxa3 and accelerate liver repair, which signified that FOXA3 may be a potential therapeutic target for further preclinical study on treating liver injury.

Deletion of hepatic small heterodimer partner ameliorates development of nonalcoholic steatohepatitis in mice

Small heterodimer partner (SHP, Nr0b2) is an orphan nuclear receptor that regulates bile acid, lipid, and glucose metabolism. Shp-/- mice are resistant to diet-induced obesity and hepatic steatosis. In this study, we explored the potential role of SHP in the development of nonalcoholic steatohepatitis (NASH). A 6-month Western diet (WD) regimen was used to induce NASH. Shp deletion protected mice from NASH progression by inhibiting inflammatory and fibrotic genes, oxidative stress, and macrophage infiltration. WD feeding disrupted the ultrastructure of hepatic mitochondria in WT mice but not in Shp-/- mice. In ApoE-/- mice, Shp deletion also effectively ameliorated hepatic inflammation after a 1 week WD regimen without an apparent antisteatotic effect. Moreover, Shp-/- mice resisted fibrogenesis induced by a methionine- and choline-deficient diet. Notably, the observed protection against NASH was recapitulated in liver-specific Shp-/- mice fed either the WD or methionine- and choline-deficient diet. Hepatic cholesterol was consistently reduced in the studied mouse models with Shp deletion. Our data suggest that Shp deficiency ameliorates NASH development likely by modulating hepatic cholesterol metabolism and inflammation.

Zinc Improves Semen Parameters in High-Fat Diet-Induced Male Rats by Regulating the Expression of LncRNA in Testis Tissue

This study aimed to identify differentially expressed LncRNAs in testis tissue of male rats induced by high-fat diet and their changes after zinc supplementation, by constructing a high-fat feeding rat model, and then supplemented with zinc, and observed the expression of LncRNA in three groups of normal, high-fat fed, and zinc-intervened rats. Experimental studies show that the semen parameters of male rats with high-fat diet were decreased but recovered after zinc supplementation, and the related LncRNA also changed. Zinc may improve the high-fat diet-induced reduction of semen parameters by changing the expression of related LncRNA.

Hepatic Energy Metabolism under the Local Control of the Thyroid Hormone System

The energy homeostasis of the organism is orchestrated by a complex interplay of energy substrate shuttling, breakdown, storage, and distribution. Many of these processes are interconnected via the liver. Thyroid hormones (TH) are well known to provide signals for the regulation of energy homeostasis through direct gene regulation via their nuclear receptors acting as transcription factors. In this comprehensive review, we summarize the effects of nutritional intervention like fasting and diets on the TH system. In parallel, we detail direct effects of TH in liver metabolic pathways with regards to glucose, lipid, and cholesterol metabolism. This overview on hepatic effects of TH provides the basis for understanding the complex regulatory network and its translational potential with regards to currently discussed treatment options of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) involving TH mimetics.

The role of FOXA family transcription factors in glucolipid metabolism and NAFLD

Abnormal glucose metabolism and lipid metabolism are common pathological processes in many metabolic diseases, such as nonalcoholic fatty liver disease (NAFLD). Many studies have shown that the forkhead box (FOX) protein subfamily FOXA has a role in regulating glucolipid metabolism and is closely related to hepatic steatosis and NAFLD. FOXA exhibits a wide range of functions ranging from the initiation steps of metabolism such as the development of the corresponding metabolic organs and the differentiation of cells, to multiple pathways of glucolipid metabolism, to end-of-life problems of metabolism such as age-related obesity. The purpose of this article is to review and discuss the currently known targets and signal transduction pathways of FOXA in glucolipid metabolism. To provide more experimental evidence and basis for further research and clinical application of FOXA in the regulation of glucolipid metabolism and the prevention and treatment of NAFLD.

FOXA3 Polymorphisms Are Associated with Metabolic Parameters in Individuals with Subclinical Atherosclerosis and Healthy Controls-The GEA Mexican Study

FOXA3 is a transcription factor involved in the macrophage cholesterol efflux and macrophage reverse cholesterol transport reducing the atherosclerotic lesions. Thus, the present study aimed to establish if the FOXA3 polymorphisms are associated with subclinical atherosclerosis (SA) and cardiometabolic parameters. Two FOXA3 polymorphisms (rs10410870 and rs10412574) were determined in 386 individuals with SA and 1070 controls. No association with SA was observed. The rs10410870 polymorphism was associated with a low risk of having total cholesterol >200 mg/dL, non-HDL-cholesterol > 160 mg/dL, and a high risk of having LDL pattern B and insulin resistance adipose tissue in individuals with SA, and with a high risk of having interleukin 10 <p25 and magnesium deficiency in controls. The rs10412574 polymorphism was associated with a low risk of insulin resistance of the adipose tissue and a high risk of aspartate aminotransferase >p75 in individuals with SA, and with a low risk of LDL pattern B and a high risk of a magnesium deficiency in controls. Independent analysis in 846 individuals showed that the rs10410870 polymorphism was associated with a high risk of aortic valve calcification. In summary, FOXA3 polymorphisms were not associated with SA; however, they were associated with cardiometabolic parameters in individuals with and without SA.

Hepatic Lipid Metabolism Disorder and Atherosclerosis

Lipid metabolism disorder plays a fundamental role in the pathogenesis of atherosclerosis. As the largest metabolic organ of the human body, liver has a key role in lipid metabolism by influencing fat production, fat decomposition, and the intake and secretion of serum lipoproteins. Numerous clinical and experimental studies have indicated that the dysfunction of hepatic lipid metabolism is closely tied to the onset of atherosclerosis. However, the identity and functional role of hepatic lipid metabolism responsible for these associations remain unknown. This review presented that cholesterol synthesis, cholesterol transport, and the metabolism of triglyceride, lipoproteins, and fatty acids are all associated with hepatic lipid metabolism and atherosclerosis. Moreover, we also discussed the roles of gut microbiota, inflammatory response, and oxidative stress in the pathological association between hepatic lipid metabolism and atherosclerosis. These significant evidences support strongly that hepatic lipid metabolism disorders may increase the risk of atherosclerosis.

Gut Metabolite Trimethylamine-N-Oxide in Atherosclerosis: From Mechanism to Therapy

Atherosclerosis is associated with various pathological manifestations, such as ischemic heart disease, ischemic stroke, and peripheral arterial disease, and remains a leading cause of public health concern. Atherosclerosis is an inflammatory disease characterized by endothelial dysfunction; vascular inflammation; and the deposition of lipids, cholesterol, calcium, and cellular debris within the vessel wall intima. In-depth studies of gut flora in recent years have shown that bacterial translocation and the existence of bacterial active products in blood circulation can affect the inflammatory state of the whole blood vessel. The gut flora is considered to be a large “secretory organ,” which produces trimethylamine-N-oxide (TMAO), short-chain fatty acids and secondary bile acids by breaking down the ingested food. Studies have shown that TMAO is an independent risk factor for the occurrence of malignant adverse cardiovascular events, but whether it is harmful or beneficial to patients with cardiovascular diseases with mild or no clinical manifestations remains controversial. We review the relationship between TMAO and its precursor (L-carnitine) and coronary atherosclerosis and summarize the potential molecular mechanism and therapeutic measures of TMAO on coronary atherosclerosis.

FOXA3 induction under endoplasmic reticulum stress contributes to non-alcoholic fatty liver disease

BACKGROUND & AIMS

Chronic endoplasmic reticulum (ER) stress in the liver has been shown to play a causative role in non-alcoholic fatty liver disease (NAFLD) progression, yet the underlying molecular mechanisms remain to be elucidated. Forkhead box A3 (FOXA3), a member of the FOX family, plays critical roles in metabolic homeostasis, although its possible functions in ER stress and fatty liver progression are unknown.

METHODS

Adenoviral delivery, siRNA delivery, and genetic knockout mice were used to crease FOXA3 gain- or loss-of-function models. Tunicamycin (TM) and a high-fat diet (HFD) were used to induce acute or chronic ER stress in mice. Chromatin immunoprecipiation (ChIP)-seq, luciferase assay, and adenoviral-mediated downstream gene manipulations were performed to reveal the transcriptional axis involved. Key axis protein levels in livers from healthy donors and patients with NAFLD were assessed via immunohistochemical staining.

RESULTS

FOXA3 transcription is specifically induced by XBP1s upon ER stress. FOXA3 exacerbates the excessive lipid accumulation caused by the acute ER-inducer TM, whereas FOXA3 deficiency in hepatocytes and mice alleviates it. Importantly, FOXA3 deficiency in mice reduced diet-induced chronic ER stress, fatty liver, and insulin resistance. In addition, FOXA3 suppression via siRNA or adeno-associated virus delivery ameliorated the fatty liver phenotype in HFD-fed and db/db mice. Mechanistically, ChIP-Seq analysis revealed that FOXA3 directly regulates Period1 (Per1) transcription, which in turn promotes the expression of lipogenic genes, including Srebp1c, thus enhancing lipid synthesis. Of pathophysiological significance, FOXA3, PER1, and SREBP1c levels were increased in livers of obese mice and patients with NAFLD.

CONCLUSION

The present study identified FOXA3 as the bridging molecule that links ER stress and NAFLD progression. Our results highlighted the role of the XBP1s-FOXA3-PER1/Srebp1c transcriptional axis in the development of NAFLD and identified FOXA3 as a potential therapeutic target for fatty liver disease.

LAY SUMMARY

The molecular mechanisms linking endoplasmic reticulum stress to non-alcoholic fatty liver disease (NAFLD) progression remain undefined. Herein, via in vitro and in vivo analysis, we identified Forkhead box A3 (FOXA3) as a key bridging molecule. Of pathophysiological significance, FOXA3 protein levels were increased in livers of obese mice and patients with NAFLD, indicating that FOXA3 could be a potential therapeutic target in fatty liver disease.

CRISPR/Cas9 Mediated Deletion of the Angiotensinogen Gene Reduces Hypertension: A Potential for Cure?

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Hydroxytyrosol Plays Antiatherosclerotic Effects through Regulating Lipid Metabolism via Inhibiting the p38 Signal Pathway

Purpose

Hydroxytyrosol (HT) processes multiaspect pharmacological properties such as antithrombosis and antidiabetes. The aim of this study was to explore the antistherosclerotic roles and relevant mechanisms of HT.

Methods

Male apoE^−/− mice were randomly divided into 2 groups: the control group and the HT group (10 mg/kg/day orally). After 16 weeks, blood tissue, heart tissue, and liver tissue were obtained to detect the atherosclerotic lesions, histological analysis, lipid parameters, and inflammation. And the underlying molecular mechanisms of HT were also studied in vivo and in vitro.

Results

HT administration significantly reduced the extent of atherosclerotic lesions in the aorta of apoE^−/− mice. We found that HT markedly lowered the levels of serum TG, TC, and LDL-C approximately by 17.4% (p = 0.004), 15.2% (p = 0.003), and 17.9% (p = 0.009), respectively, as well as hepatic TG and TC by 15.0% (p < 0.001) and 12.3% (p = 0.003), respectively, while inducing a 26.9% (p = 0.033) increase in serum HDL-C. Besides, HT improved hepatic steatosis and lipid deposition. Then, we discovered that HT could regulate the signal flow of AMPK/SREBP2 and increase the expression of ABCA1, apoAI, and SRBI. In addition, HT reduced the levels of serum CRP, TNF-α, IL-1β, and IL-6 approximately by 23.5% (p < 0.001), 27.8% (p < 0.001), 18.4% (p < 0.001), and 19.1% (p < 0.001), respectively, and induced a 1.4-fold increase in IL-10 level (p = 0.014). Further, we found that HT might regulate cholesterol metabolism via decreasing phosphorylation of p38, followed by activation of AMPK and inactivation of NF-κB, which in turn triggered the blockade of SREBP2/PCSK9 and upregulation of LDLR, apoAI, and ABCA1, finally leading to a reduction of LDL-C and increase of HDL-C in the circulation.

Conclusion

Our results provide the first evidence that HT displays antiatherosclerotic actions via mediating lipid metabolism-related pathways through regulating the activities of inflammatory signaling molecules.

Hepatocyte ATF3 protects against atherosclerosis by regulating HDL and bile acid metabolism

Activating transcription factor (ATF)3 is known to have an anti-inflammatory function, yet the role of hepatic ATF3 in lipoprotein metabolism or atherosclerosis remains unknown. Here we show that overexpression of human ATF3 in hepatocytes reduces the development of atherosclerosis in Western-diet-fed Ldlr^-/- or Apoe^-/- mice, whereas hepatocyte-specific ablation of Atf3 has the opposite effect. We further show that hepatic ATF3 expression is inhibited by hydrocortisone. Mechanistically, hepatocyte ATF3 enhances high-density lipoprotein (HDL) uptake, inhibits intestinal fat and cholesterol absorption and promotes macrophage reverse cholesterol transport by inducing scavenger receptor group B type 1 (SR-BI) and repressing cholesterol 12α-hydroxylase (CYP8B1) in the liver through its interaction with p53 and hepatocyte nuclear factor 4α, respectively. Our data demonstrate that hepatocyte ATF3 is a key regulator of HDL and bile acid metabolism and atherosclerosis.

Effect of functional single nucleotide polymorphism g.-572 A > G of apolipoprotein A1 gene on resistance to ketosis in Chinese Holstein cows

The ketosis has negative effects on the high-yielding dairy cows during early lactation. Apolipoprotein A1 (APOA1) is a component of high-density lipoprotein. However, the association of APOA1 gene with ketosis, and the molecular mechanisms of expression of APOA1 gene are not fully understood in dairy cows. In this study, expression of APOA1 in the liver and blood was investigated by RT-qPCR and immunohistochemistry, and genetic variation in the 5'-flanking region of the AOPA1 gene was also screened and identified. In addition, correlation of the single nucleotide polymorphisms (SNPs) of APOA1 gene with blood ketone characters, and activity of APOA1 promoter were analyzed in dairy cows. The results showed that ApoA1 protein was expressed in the liver, and the mRNA level of APOA1 was significantly higher in the cows with ketosis comparing to the healthy cows. In addition, a novel SNP (g.-572 A > G) in the core promoter of the APOA1 gene was identified between base g.-714 and g.-68 through transient transfection in both HepG2 cell and FFb cell, and luciferase report assay. Moreover, there was lower concentration of blood β-hydroxybutyrate in cows with genotype GG comparing to the cows with genotypes AA and AG. This study reported for the first time that the genetic variant g.-572 A > G in the core promoter region of APOA1 gene was associated with the ketosis in Chinese Holstein cows, and g.-572 A > G may be used as a genetic marker for ketosis prevention.

Atherosclerosis: cell biology and lipoproteins

PURPOSE OF REVIEW

Lipoproteins have significant role in both the promotion and prevention of atherosclerosis. This brief review will focus on recent reports on relationship between HDL and HDL subclasses and their composition and function, the role of apoC-III in metabolism of triglyceride-rich lipoproteins, the impact of Lipoprotein (a) (Lp(a)) on endothelial cells, and the mechanism of uptake of aggregated LDL by macrophages.

RECENT FINDINGS

The complexity of the protein and lipid content of murine and human HDL and their relationship to its cholesterol efflux capacity have been examined. HDL has also been shown to have both antiatherogenic and proatherogenic properties. The relationship between apoC-III and LPL activity, apoprotein E mediated clearance of triglyceride-rich lipoproteins and the potential importance of apoC-III in the increased risk of cardiovascular disease in type 1 diabetics has been investigated. Oxidized phospholipid in Lp(a) promotes endothelial cells inflammatory and glycolytic responses. TLR4 participates in the uptake of aggregated LDL to contribute to foam cell formation.

SUMMARY

These studies contribute to our mechanistic understanding of how lipoproteins contribute to atherogenesis and identify potential therapeutic targets.

Glucose restriction delays senescence and promotes proliferation of HUVECs via the AMPK/SIRT1-FOXA3-Beclin1 pathway

Caloric restriction (CR) is an important means to delay senescence, and glucose restriction is one of the measures to achieve CR. On the basis of our previous work and bioinformatics analysis, we hypothesized that glucose restriction can up-regulate autophagy, inhibit senescence and promote proliferation via the AMPK/SIRT1-FOXA3-Beclin1 pathway in human umbilical vein endothelial cells (HUVECs). We found that compared with 5.5 mmol/L and 25 mmol/L glucose, 2.5 mmol/L glucose restriction significantly reduced senescence, enhanced autophagy, increased migration speed, relieved G₀/G₁ phase arrest and enhanced proliferation of HUVECs. Furthermore, glucose restriction up-regulated AMPKα1, SIRT1, FOXA3 and Beclin1 expression in HUVECs. Additionally, we demonstrated that AMPKα1 phosphorylated FOXA3 at S170 and S305 in the cytoplasm and promoted FOXA3 nuclear translocation under glucose restriction. FOXA3 in the nucleus was deacetylated by SIRT1 at K214 and K221. Deacetylated FOXA3 specifically bound to +109 C in the Beclin1 transcriptional regulatory region, and significantly enhanced Beclin1 transcription and expression. siRNA knock down of AMPKα1, SIRT1, FOXA3 or Beclin1 expression impaired the glucose restriction-induced inhibition of senescence, enhanced autophagy, increased migration, and induced proliferation of HUVECs. This study confirmed that glucose restriction can enhance autophagy, inhibit senescence, and enhance proliferation of HUVECs through the AMPK/SIRT1-FOXA3-Beclin1 pathway.

LncRNA TUG1 regulates ApoM to promote atherosclerosis progression through miR-92a/FXR1 axis

This study aims to explore the possible mechanism of TUG1 regulating ApoM in AS. To this end, expression levels of TUG1 and ApoM were measured in high fat dieted C57BL/6J mice, normal dieted C57BL/6J mice, ob/ob mice and db/db mice. LV‐TUG1 or sh‐TUG1 was injected into C57BL/6J mice before isolating peritoneal macrophages to measure cholesterol efflux (CE) and expression levels of ABCA1, ABCG1 and SR‐BI. Meanwhile, CE in RAW264.7 cells was also measured after cell transfection. Dual luciferase reporter assay and anti‐AGO2 RIP were applied to verify the relationship among TUG1, FXR1 and miR‐92a. Total cholesterol (TC), triglyceride (TG), low‐density lipoprotein cholesterin (LDL‐C), high‐density lipoprotein cholesterol (HDL‐C) as well as expressions of inflammatory cytokines (TNF‐α, IL‐1β and IL‐6) in plasma were measured. Knock‐down or expressed TUG1, FXR1 or miR‐92a in NCTC 1469 cells or in ApoE−/− AS mice to determine the alteration on ApoM and plaque size. TUG1 was highly expressed while ApoM was down‐regulated in high fat dieted C57BL/6J mice, b/ob and db/db mice. Overexpression of TUG1 could reduce the expression of ApoM, ABCA1 and ABCG1 in addition to slowing down CE rate. Reversed expression pattern was found in cells with knock‐down of TUG1. TUG1 can compete with FXR1 to bind miR‐92a. FXR1 negatively target ApoM. Overexpression of TUG1 in ApoE−/− mice can increase plaque size and enhance macrophage contents accordingly. TUG1 can inhibit ApoM in both liver tissues and plasma to inhibit CE through regulating miR‐92a/ FXR1 axis. TUG1 is a promising target for AS treatment.

Collapse of the hepatic gene regulatory network in the absence of FoxA factors

Here, Reizel et al. investigated the FoxA factor's role in maintaining the regulatory network needed for liver development, and ablated all FoxA genes in the adult mouse liver. They found that loss of FoxA caused rapid and massive reduction in the expression of critical liver genes, and that FoxA proteins are be required for maintaining enhancer activity, chromatin accessibility, nucleosome positioning, and binding of HNF4α.

The FoxA transcription factors are critical for liver development through their pioneering activity, which initiates a highly complex regulatory network thought to become progressively resistant to the loss of any individual hepatic transcription factor via mutual redundancy. To investigate the dispensability of FoxA factors for maintaining this regulatory network, we ablated all FoxA genes in the adult mouse liver. Remarkably, loss of FoxA caused rapid and massive reduction in the expression of critical liver genes. Activity of these genes was reduced back to the low levels of the fetal prehepatic endoderm stage, leading to necrosis and lethality within days. Mechanistically, we found FoxA proteins to be required for maintaining enhancer activity, chromatin accessibility, nucleosome positioning, and binding of HNF4α. Thus, the FoxA factors act continuously, guarding hepatic enhancer activity throughout adult life.

Functionally analyzing the important roles of hepatocyte nuclear factor 3 (FoxA) in tumorigenesis

Transcriptional factors (TFs) play a central role in governing gene expression under physiological conditions including the processes of embryonic development, metabolic homeostasis and response to extracellular stimuli. Conceivably, the aberrant dysregulations of TFs would dominantly result in various human disorders including tumorigenesis, diabetes and neurodegenerative diseases. Serving as the most evolutionarily reserved TFs, Fox family TFs have been explored to exert distinct biological functions in neoplastic development, by manipulating diverse gene expression. Recently, among the Fox family members, the pilot roles of FoxAs attract more attention due to their functions as both pioneer factor and transcriptional factor in human tumorigenesis, particularly in the sex-dimorphism tumors. Therefore, the pathological roles of FoxAs in tumorigenesis have been well-explored in modulating inflammation, immune response and metabolic homeostasis. In this review, we comprehensively summarize the impressive progression of FoxA functional annotation, clinical relevance, upstream regulators and downstream effectors, as well as valuable animal models, and highlight the potential strategies to target FoxAs for cancer therapies.

High Density Lipoproteins: Metabolism, Function, and Therapeutic Potential

High Density Lipoproteins (HDLs) have long been considered as “good cholesterol,” beneficial to the whole body and, in particular, to cardio-vascular health. However, HDLs are complex particles that undergoes dynamic remodeling through interactions with various enzymes and tissues throughout their life cycle, making the complete understanding of its functions and roles more complicated than initially expected. In this review, we explore the novel understanding of HDLs' behavior in health and disease as a multifaceted class of lipoprotein, with different size subclasses, molecular composition, receptor interactions, and functionality. Further, we report on emergent HDL-based therapeutics tested in small and larger scale clinical trials and their mixed successes.

CXCL12 promotes atherosclerosis by downregulating ABCA1 expression via the CXCR4/GSK3β/β-cateninT120/TCF21 pathway

CXC chemokine ligand 12 (CXCL12) is a member of the CXC chemokine family and mainly acts on cell chemotaxis. CXCL12 also elicits a proatherogenic role, but the molecular mechanisms have not been fully defined yet. We aimed to reveal if and how CXCL12 promoted atherosclerosis via regulating lipid metabolism. In vitro, our data showed that CXCL12 could reduce ABCA1 expression, and it mediated cholesterol efflux from THP-1-derived macrophages to apoA-I. Data from the luciferase reporter gene and chromatin immunoprecipitation assays revealed that transcription factor 21 (TCF21) stimulated the transcription of ABCA1 via binding to its promoter region, which was repressed by CXCL12. We found that CXCL12 increased the levels of phosphorylated glycogen synthase kinase 3β (GSK3β) and the phosphorylation of β-catenin at the Thr120 position. Inactivation of GSK3β or β-catenin increased the expression of TCF21 and ABCA1. Further, knockdown or inhibition of CXC chemokine receptor 4 (CXCR4) blocked the effects of CXCL12 on TCF21 and ABCA1 expression and the phosphorylation of GSK3β and β-catenin. In vivo, the overexpression of CXCL12 in Apoe^-/- mice via lentivirus enlarged the atherosclerotic lesion area and increased macrophage infiltration in atherosclerotic plaques. We further found that the overexpression of CXCL12 reduced the efficiency of reverse cholesterol transport and plasma HDL-C levels, decreased ABCA1 expression in the aorta and mouse peritoneal macrophages (MPMs), and suppressed cholesterol efflux from MPMs to apoA-I in Apoe^-/- mice. Collectively, these findings suggest that CXCL12 interacts with CXCR4 and then activates the GSK-3β/β-catenin^T120/TCF21 signaling pathway to inhibit ABCA1-dependent cholesterol efflux from macrophages and aggravate atherosclerosis. Targeting CXCL12 may be a novel and promising strategy for the prevention and treatment of atherosclerotic cardiovascular diseases.