Regulation Of Cholesterol Transport Research Articles

Regulation of Cholesterol Transporters by Nuclear Receptors

Atherosclerosis is a pathological condition characterized by the accumulation of plaques in the arteries, leading to cardiovascular diseases. The deposition of cholesterol in peripheral cells increases the risk of atherosclerosis. Reverse cholesterol transport (RCT) is essential to reduce the risk of atherosclerosis because it removes excessive cholesterol from the peripheral tissues. ATP-binding cassette transporters such as ABCA1, ABCG1, ABCG5, and ABCG8 are involved in the efflux of cholesterol. The upregulation of these ABC transporters enhances RCT, thereby promoting the removal of excess cholesterol from the body. The expression and activity of ABC transporters are regulated by transcriptional and post-transcriptional mechanisms, as well as by post-translational modifications. In this review, the regulation of ABC transporters by nuclear receptors such as farnesoid X receptor, liver X receptor, retinoid X receptor, retinoic acid receptor, and peroxisome proliferator-activated receptors is discussed. Pharmacological and natural compounds serving as agonists for the nuclear receptors have been identified to elevate the mRNA levels of the transporters. Consequently, it is anticipated that these compounds will attenuate the development of atherosclerosis through stimulation of the ABC transporters, thereby enhancing RCT and fecal cholesterol excretion. Understanding these regulatory processes can aid in the development of therapeutic approaches to prevent atherosclerosis.

Liver X receptors induce antiproliferative effects in basal-like breast cancer.

Liver X receptors (LXRs) are nuclear transcription factors important in the regulation of cholesterol transport, and glucose and fatty acid metabolism. The antiproliferative role of LXRs has been studied in a variety of malignancies and may represent a therapeutic opportunity in cancers lacking targeted therapies, such as triple-negative breast cancer. In this study, we investigated the impact of LXR agonists alone and in combination with carboplatin in preclinical models of breast cancer. In vitro experiments revealed a dose-dependent decrease in tumor cell proliferation in estrogen receptor-positive breast cancer cells, whereas LXR activation in vivo resulted in an increased growth inhibitory effect in a basal-like breast cancer model (in combination with carboplatin). Functional proteomic analysis identified differences in protein expression between responding and nonresponding models related to Akt activity, cell-cycle progression, and DNA repair. Furthermore, pathway analysis suggested that the LXR agonist in combination with carboplatin inhibits the activity of targets of E2F transcription factors and affects cholesterol homeostasis in basal-like breast cancer.

In This Issue

HomeCirculation ResearchVol. 132, No. 1In This Issue Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBIn This Issue Ruth Williams Ruth WilliamsRuth Williams Search for more papers by this author Originally published5 Jan 2023https://doi.org/10.1161/RES.0000000000000587Circulation Research. 2023;132:2Maintenance of Enteral ACE2 Prevents Diabetic Retinopathy in Type 1 Diabetes (p e1)Download figureDownload PowerPointProbiotic delivery of ACE2 improves gut integrity and retinopathy in diabetic mice, show Prasad et al.Type 1 diabetes has a complex etiology and pathology that are not entirely understood. In addition to the destruction of insulin-producing cells, a recently discovered feature of the disease (in both model rodents and humans) is that levels of angiotensin-converting enzyme 2 (ACE2)—a component of the renin-angiotensin system controlling hemodynamics—can be unusually low in certain tissues. Moreover, genetic deficiency of ACE2 in rodents, exacerbates aspects of diabetes such as gut permeability, systemic inflammation and diabetic retinopathy, while boosting ACE2 levels has been shown to ameliorate diabetic retinopathy in mice. Prasad and colleagues now show that ACE2 treatment also improves gut integrity and systemic inflammation as well as retinopathy, and that certain improvements can even be seen once diabetes has long been established. Six months after the onset of diabetes in model mice, oral doses of Lactobacillus paracasei engineered to express humanized ACE2 led to a reversal of the animal’s gut barrier dysfunction and retinopathy, the team showed. Humans with diabetic retinopathy also displayed evidence of increased gut permeability and low ACE2 levels, suggesting they may benefit from a similar probiotic treatment developed for clinical use.Epsin Nanotherapy Regulates Cholesterol Transport to Fortify Atheroma Regression (p e22)Download figureDownload PowerPointSuppressing epsin activity could be a new way to treat atherosclerosis, suggest Cui et al.Epsins are a family of plasma membrane proteins that drive endocytosis. They are expressed at varying levels throughout the tissues of the body, and recent research shows they are unusually abundant on macrophages within atherosclerotic lesions. Furthermore, in mice, macrophage-specific epsin loss results in a reduction in foam cell formation and plaque development. Cui and colleagues now show this effect on foam cells is because epsins normally promote the internalization of lipids into macrophages through their endocytic activity. But that’s not all. The proteins also impede cholesterol efflux from macrophages further exacerbating lipid retention, the team found. It turns out, epsins drive the endocytosis and degradation of a cholesterol efflux factor called ABCG1. Importantly, these proatherogenic activities of epsins could be stopped. Using macrophage-targeting nanoparticles carrying epsin-specific silencing RNAs, the team could suppress production of the protein in cultured macrophages, and could reduce the size and number of plaques in atherosclerosis-prone mice (via injection of the nanoparticles). Together the results suggest blocking epsins, via nanotherapy or other means, could be a therapeutic approach to stopping or slowing atherosclerosis progression.Inhibition of Eicosanoid Degradation Mitigates Fibrosis of the Heart (p 10)Download figureDownload PowerPointBlocking 15-PGDH quells fibroblast activation to prevent cardiac fibrosis in mice, report Rubino et al.After a myocardial infarction, the initial scar that forms is essential for protecting the muscle from further damage and rupture. But, if the fibrosis is extensive or prolonged, it can limit muscle function and ultimately lead to heart failure and death. Finding treatments that prevent or reverse fibrosis is thus a desirable clinical goal. To identify inhibitors of profibrotic activity, Rubino and colleagues screened a library of 546 known non-toxic compounds for their ability to block growth factor-induced activation of rat fibroblast cells. Of the nine compounds with such activity, the team focused on one—SW033291—that had previously been shown to prevent lung fibrosis in mice. This compound inhibits the enzyme 15-PGDH, which degrades signaling molecules known as eicosanoids, which are involved in, among other things, tissue repair. Further experiments showed the compound could also switch off the activation state of human cardiac fibroblasts isolated from failing hearts. The team went on to show that infusing SW033291 into mice could ameliorate experimentally induced cardiac fibrosis and diastolic dysfunction. The findings thus identify 15-PDGH as a profibrotic factor that could serve as a therapeutic target for mitigating heart fibrosis and failure. 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Epsin Nanotherapy Regulates Cholesterol Transport to Fortify Atheroma Regression.

Excess cholesterol accumulation in lesional macrophages elicits complex responses in atherosclerosis. Epsins, a family of endocytic adaptors, fuel the progression of atherosclerosis; however, the underlying mechanism and therapeutic potential of targeting Epsins remains unknown. In this study, we determined the role of Epsins in macrophage-mediated metabolic regulation. We then developed an innovative method to therapeutically target macrophage Epsins with specially designed S2P-conjugated lipid nanoparticles, which encapsulate small-interfering RNAs to suppress Epsins. We used single-cell RNA sequencing with our newly developed algorithm MEBOCOST (Metabolite-mediated Cell Communication Modeling by Single Cell Transcriptome) to study cell-cell communications mediated by metabolites from sender cells and sensor proteins on receiver cells. Biomedical, cellular, and molecular approaches were utilized to investigate the role of macrophage Epsins in regulating lipid metabolism and transport. We performed this study using myeloid-specific Epsin double knockout (LysM-DKO) mice and mice with a genetic reduction of ABCG1 (ATP-binding cassette subfamily G member 1; LysM-DKO-ABCG1fl/+). The nanoparticles targeting lesional macrophages were developed to encapsulate interfering RNAs to treat atherosclerosis. We revealed that Epsins regulate lipid metabolism and transport in atherosclerotic macrophages. Inhibiting Epsins by nanotherapy halts inflammation and accelerates atheroma resolution. Harnessing lesional macrophage-specific nanoparticle delivery of Epsin small-interfering RNAs, we showed that silencing of macrophage Epsins diminished atherosclerotic plaque size and promoted plaque regression. Mechanistically, we demonstrated that Epsins bound to CD36 to facilitate lipid uptake by enhancing CD36 endocytosis and recycling. Conversely, Epsins promoted ABCG1 degradation via lysosomes and hampered ABCG1-mediated cholesterol efflux and reverse cholesterol transport. In a LysM-DKO-ABCG1fl/+ mouse model, enhanced cholesterol efflux and reverse transport due to Epsin deficiency was suppressed by the reduction of ABCG1. Our findings suggest that targeting Epsins in lesional macrophages may offer therapeutic benefits for advanced atherosclerosis by reducing CD36-mediated lipid uptake and increasing ABCG1-mediated cholesterol efflux.

Retraction: Role of the apical and basolateral domains of the enterocyte in the regulation of cholesterol transport by a high glucose concentration.

Retraction: Role of the apical and basolateral domains of the enterocyte in the regulation of cholesterol transport by a high glucose concentration.

Regulation of Adipocyte Metabolic Homeostasis by SR‐BI and PCPE2

Obesity continues to be an epidemic in the United States, placing individuals at a higher risk of developing other comorbidities such as type 2 diabetes and cardiovascular disease. Adipocytes accumulate excess triglycerides and undergo hypertrophic expansion as a protective mechanism to avoid lipotoxicity. Adipocytes are also highly dynamic cells that perform many key metabolic processes including lipid and glucose metabolism. Recent collaborative studies demonstrated that SR‐BI function may require the extracellular matrix protein procollagen C‐endopeptidase enhancer 2 (PCPE2) to regulate cholesterol transport in hepatocytes and adipocytes. However, the roles of SR‐BI and PCPE2 in other adipocyte metabolic processes and whether they maintain their cooperative partnership for these functions remains unknown. This knowledge gap prompted our novel hypothesis that PCPE2 facilitates SR‐BI’s ability to regulate metabolic processes in adipocytes. To test our hypothesis, we have optimized an adipocyte model system where mesenchymal stem cells isolated from the outer ears of wild‐type (WT), SR‐BI knockout (SR‐BI‐/‐), and PCPE2‐/‐ mice are differentiated into adipocyte‐like cells. We validated our adipocyte model system by demonstrating increased Oil‐Red‐O staining, mRNA expression of adipogenesis markers, and adiponectin secretion over a 9‐day post‐differentiation period for all three genotypes. This model system was then used to test the roles of SR‐BI and PCPE2 on various metabolic functions, including glucose, fatty acid, and mitochondrial metabolism. Preliminary data suggest that loss of SR‐BI and PCPE2 impaired glucose uptake, despite observing elevated levels of GLUT4 at the cell surface. PCPE2‐/‐ adipocytes also showed increased response to insulin through AKT signaling, which may be responsible for the increased expression of GLUT4 at the cell surface. However, we observed that loss of SR‐BI or PCPE2 had no effect on transport of palmitic acid in adipocytes, despite there being elevated expression of fatty acid transporters (FABP4, CD36). Adipocytes lacking SR‐BI or PCPE2 showed an inverse response to insulin compared to WT adipocytes when measuring phosphorylation status of proteins responsible for mediating fatty acid synthesis (AMPK, ACC). These data suggest that although SR‐BI and PCPE2 do not appear to mediate uptake of palmitic acid, they may have altered lipid metabolism. Lastly, adipocytes lacking SR‐BI or PCPE2 exhibit changes in mitochondrial mass and morphology, but their role in maintaining healthy mitochondria remains inconclusive. Altogether, these data suggest that SR‐BI and PCPE2 appear to have independent roles in various steps of adipocyte metabolism, but their required partnership remains unclear.

The Effects of Diosgenin on Hypolipidemia and Its Underlying Mechanism: A Review.

Hyperlipidemia is a disorder of lipid metabolism, which is a major cause of coronary heart disease. Although there has been considerable progress in hyperlipidemia treatment, morbidity and risk associated with the condition continue to rise. The first-line treatment for hyperlipidemia, statins, has multiple side effects; therefore, development of safe and effective drugs from natural products to prevent and treat hyperlipidemia is necessary. Diosgenin is primarily derived from fenugreek (Trigonella foenum graecum) seeds, and is also abundant in medicinal herbs such as Dioscorea rhizome, Dioscorea septemloba, and Rhizoma polygonati, is a well-known steroidal sapogenin and the active ingredient in many drugs to treat cardiovascular conditions. There is abundant evidence that diosgenin has potential for application in correcting lipid metabolism disorders. In this review, we evaluated the latest evidence related to diosgenin and hyperlipidemia from clinical and animal studies. Additionally, we elaborate the pharmacological mechanism underlying the activity of diosgenin in treating hyperlipidemia in detail, including its role in inhibition of intestinal absorption of lipids, regulation of cholesterol transport, promotion of cholesterol conversion into bile acid and its excretion, inhibition of endogenous lipid biosynthesis, antioxidation and lipoprotein lipase activity, and regulation of transcription factors related to lipid metabolism. This review provides a deep exploration of the pharmacological mechanisms involved in diosgenin-hyperlipidemia interactions and suggests potential routes for the development of novel drug therapies for hyperlipidemia.

Abstract MP33: Coordination Of Metabolic Functions By SR-BI And PCPE2 In Adipocytes

Obesity continues to be an epidemic in the United States, placing individuals at a higher risk of developing other comorbidities such as type 2 diabetes and cardiovascular disease. Adipocytes accumulate excess triglycerides and undergo hypertrophic expansion as a protective mechanism to avoid lipotoxicity. Adipocytes are also highly dynamic cells that perform many key metabolic processes including lipid and glucose metabolism. Recent collaborative studies demonstrated that SR-BI function may require the extracellular matrix protein procollagen C-endopeptidase enhancer 2 (PCPE2) in to regulate cholesterol transport in hepatocytes and adipocytes. However, the roles of SR-BI and PCPE2 in other adipocyte metabolic processes remain unclear. This knowledge gap prompted our novel hypothesis that PCPE2 facilitates SR-BI’s ability to regulate metabolic processes in adipocytes. To test our hypothesis, we have optimized an adipocyte model system where mesenchymal stem cells isolated from the outer ears of wild-type (WT), SR-BI knockout (SR-BI -/- ), and PCPE2 -/- mice were differentiated into adipocyte-like cells. We validated our adipocyte model system by demonstrating increased Oil Red O staining, mRNA expression of adipogenesis markers, and adiponectin secretion over a 9-day post-differentiation period for all three genotypes. This model system was then used to test the roles of SR-BI and PCPE2 on various metabolic functions. Preliminary data suggests that absence of SR-BI or PCPE2 slightly impairs fatty acid uptake into adipocytes despite elevated gene expression of fatty acid transporters (FABP4, CD36) compared to WT. These data further suggest that SR-BI may rely on PCPE2 to aid in transport of fatty acids. Adipocytes lacking SR-BI or PCPE2 also displayed higher levels of mitochondrial reactive oxygen species, indicating that SR-BI and PCPE2 may be important for maintaining healthy mitochondria in adipocytes. These changes in function do not appear to depend on SR-BI oligomerization, as BS 3 crosslinking studies demonstrated the presence of SR-BI oligomers in adipocytes despite the loss of PCPE2. Altogether, these data suggest that SR-BI and PCPE2 may be reliant on each other and are important for mediating metabolic processes in adipocytes.

Recent developments in the regulation of cholesterol transport by natural molecules

The dysregulation of cholesterol metabolism is a high-risk factor for non-alcoholic fatty liver disease (NAFLD), dyslipidemia, and atherosclerosis (AS). Cholesterol transport maintains whole-body cholesterol homeostasis. Low-density apolipoprotein receptor (LDLR) mediates cholesterol uptake in cells and plays an important role in the primary route of circulatory cholesterol clearance in liver cells. Caveolins 1 is an integral membrane protein and shuttle between the cytoplasm and cell membrane. Caveolins 1 not only plays a role in promoting cholesterol absorption in cells but also in the transport of cellular cholesterol efflux by interacting with the ATP-binding cassette transporter A1 (ABCA1) and scavenger receptor class B type I (SR-BI). These proteins, which are associated with reverse cholesterol transport (RCT), are potential therapeutic targets for NAFLD and AS. Many studies have indicated that natural products have lipid-lowering effects. Moreover, natural molecules, derived from natural products, have the potential to be developed into novel drugs. However, the mechanisms underlying the regulation of cholesterol transport by natural molecules have not yet been adequately investigated. In this review, we briefly describe the process of cholesterol transport and summarize the mechanisms by which molecules regulate cholesterol transport. This article provides an overview of recent studies and focuses on the potential therapeutic effects of natural molecules; however, further high-quality studies are needed to firmly establish the clinical efficacies of natural molecules.

Gu-Ben-Fang-Xiao decoction modulates lipid metabolism by activating the AMPK pathway in asthma remission

Gu-Ben-Fang-Xiao decoction (GBFXD), derived from the traditional Chinese medicine Yu-Ping-Feng-San, is widely used in clinical settings and has obvious curative effects in respiratory diseases. GBFXD regulates cholesterol transport and lipid metabolism in chronic persistent asthma. There is evidence for its beneficial effects in the remission stage of asthma; however, its metabolic regulatory effects and underlying mechanisms during asthma remission are unclear. In the present study, we used liquid chromatography-mass spectrometry (LC-MS) to analyse the metabolic profile of mouse serum during asthma remission. The acquired LC–MS data were subjected to a multivariate analysis for identification of significantly altered metabolites. In total, 42 metabolites were significantly differentially expressed among the control, model, and GBFXD groups. In particular, levels of fatty acids, acylcarnitines, phosphatidylcholines, phosphatidylethanolamines, phosphatidylinositols, triglycerides, and diacylglycerols were altered during asthma remission. GBFXD may maintain lipid homeostasis on the lung surface by modulating lipid metabolism and may thereby alleviate asthma. We further quantified hypogeic acid (FA 16:1) based on targeted metabolomics and found that GBFXD may regulate fatty acid metabolism by activating the AMP-activated protein kinase (AMPK) pathway. These results support the use of GBFXD in patients with asthma remission.

TMEM97 facilitates the activation of SOCE by downregulating the association of cholesterol to Orai1 in MDA-MB-231 cells

The expression of TMEM97, a regulator of cholesterol transport, has been reported to be enhanced in some tumour cells. We have recently shown that TMEM97 is involved in the proliferation of the breast cancer cell line MDA-MB-231, probably through changes in store-operated calcium entry (SOCE). By using silencing and overexpression of TMEM97 in MDA-MB-231 cells (two manoeuvres that either reduce or increase the calcium influx, respectively), we show enhanced cholesterol uptake in these cells as compared to the non-tumoral breast cell line, MCF10A. The enhanced cholesterol uptake in MDA-MB-231 cells was inhibited by silencing TMEM97, while overexpression of this protein increased cholesterol uptake in MCF10A cells and, therefore, indicating that this protein plays a role in the enhanced cholesterol uptake in MDA-MB-231 cancer cell line. TMEM97 silencing and overexpression resulted in an increase and decrease in the association of cholesterol to the SOCE calcium channel Orai1, respectively. Interestingly, silencing of TMEM97 in MDA-MB-231 cells significantly reduced the co-localization of Orai1 with the SOCE regulatory protein STIM1. Finally, neither silencing nor overexpression of TMEM97 altered SOCE in MDA-MB-231 cells transfected with the cholesterol insensible mutant of Orai1(Y80E). Our results reveal a novel regulatory mechanism of SOCE that relies on TMEM97 activity that courses through the reduction of the cholesterol content in the plasma membrane, and subsequently, by impairing its interaction with Orai1.

The role of the retinoid receptor, RAR/RXR heterodimer, in liver physiology

Activated by retinoids, metabolites of vitamin A, the retinoic acid receptors (RARs) and the retinoid X receptors (RXRs) play important roles in a wide variety of biological processes, including embryo development, homeostasis, cell proliferation, differentiation and death. In this review, we summarized the functional roles of nuclear receptor RAR/RXR heterodimers in liver physiology. Specifically, RAR/RXR modulate the synthesis and metabolism of lipids and bile acids in hepatocytes, regulate cholesterol transport in macrophages, and repress fibrogenesis in hepatic stellate cells. We have also listed the specific genes that carry these functions and how RAR/RXR regulate their expression in liver cells, providing a mechanistic view of their roles in liver physiology. Meanwhile, we pointed out many questions regarding the detailed signaling of RAR/RXR in regulating the expression of liver genes, and hope future studies will address these issues.

Localisation and regulation of cholesterol transporters in the human hair follicle: mapping changes across the hair cycle

Cholesterol has long been suspected of influencing hair biology, with dysregulated homeostasis implicated in several disorders of hair growth and cycling. Cholesterol transport proteins play a vital role in the control of cellular cholesterol levels and compartmentalisation. This research aimed to determine the cellular localisation, transport capability and regulatory control of cholesterol transport proteins across the hair cycle. Immunofluorescence microscopy in human hair follicle sections revealed differential expression of ATP-binding cassette (ABC) transporters across the hair cycle. Cholesterol transporter expression (ABCA1, ABCG1, ABCA5 and SCARB1) reduced as hair follicles transitioned from growth to regression. Staining for free cholesterol (filipin) revealed prominent cholesterol striations within the basement membrane of the hair bulb. Liver X receptor agonism demonstrated active regulation of ABCA1 and ABCG1, but not ABCA5 or SCARB1 in human hair follicles and primary keratinocytes. These results demonstrate the capacity of human hair follicles for cholesterol transport and trafficking. Future studies examining the role of cholesterol transport across the hair cycle may shed light on the role of lipid homeostasis in human hair disorders.

Longitudinal [18F]FDG-PET/CT analysis of the glucose metabolism in ApoE-deficient mice

BackgroundStrong line of evidence suggests that the increased risk to develop AD may at least be partly mediated by cholesterol metabolism. A key regulator of cholesterol transport is the Apolipoprotein E4 (ApoE4), which plays a fundamental role in neuronal maintenance and repair. Impaired function of ApoE4 may contribute to altered cerebral metabolism leading to higher susceptibility to neurodegeneration.MethodsTo determine a possible link between ApoE function and alterations in AD in the brain of Apolipoprotein E-deficient mice (ApoE−/−) in a longitudinal manner metabolic and neurochemical parameters were analyzed. Cortical metabolism was measured by 2-deoxy-2-[18F]fluoroglucose ([18F]FDG)-PET/CT and proton magnetic resonance spectroscopy (1H-MRS) served to record neurochemical status.ResultsBy using [18F]FDG-PET/CT, we showed that brain metabolism declined significantly stronger with age in ApoE−/− versus wild type (wt) mice. This difference was particularly evident at the age of 41 weeks in almost each analyzed brain region. In contrast, the 1H-MRS-measured N-acetylaspartate to creatine ratio, a marker of neuronal viability, did not decline with age and did not differ between ApoE−/− and wt mice.ConclusionIn summary, this longitudinal in vivo study shows for the first time that ApoE−/− mice depict cerebral hypometabolism without neurochemical alterations.

4β-Hydroxycholesterol Signals From the Liver to Regulate Peripheral Cholesterol Transporters.

Activation of pregnane X receptor (PXR) elevates circulating 4β-hydroxycholesterol (4βHC), an agonist of liver X receptor (LXR). PXR may also regulate 25-hydroxycholesterol and 27-hydroxycholesterol. Our aim was to elucidate the roles of PXR and oxysterols in the regulation of cholesterol transporters. We measured oxysterols in serum of volunteers dosed with PXR agonist rifampicin 600 mg/day versus placebo for a week and analyzed the expression of cholesterol transporters in mononuclear cells. The effect of 4βHC on the transport of cholesterol and the expression of cholesterol transporters was studied in human primary monocyte-derived macrophages and foam cells in vitro. The expression of cholesterol transporters was measured also in rat tissues after dosing with a PXR agonist. The levels of 4βHC were elevated, while 25-hydroxycholesterol and 27-hydroxycholesterol remained unchanged in volunteers dosed with rifampicin. The expression of ATP binding cassette transporter A1 (ABCA1) was induced in human mononuclear cells in vivo. The influx of cholesterol was repressed by 4βHC, as was the expression of influx transporter lectin-like oxidized LDL receptor-1 in vitro. The cholesterol efflux and the expression of efflux transporters ABCA1 and ABCG1 were induced. The expression of inducible degrader of the LDL receptor was induced. In rats, PXR agonist increased circulating 4βHC and expression of LXR targets in peripheral tissues, especially ABCA1 and ABCG1 in heart. In conclusion, PXR activation-elevated 4βHC is a signaling molecule that represses cholesterol influx and induces efflux. The PXR-4βHC-LXR pathway could link the hepatic xenobiotic exposure and the regulation of cholesterol transport in peripheral tissues.

Abstract P178: Relationship of Apolipoproteins With Subclinical Cardiovascular Risk in Youth

Introduction: Apolipoproteins are key regulators of cholesterol transport and clearance with each apolipoprotein having a specific protective or atherogenic role. The relationship between subclinical cardiovascular risk and each of the apolipoproteins in the pediatric population is insufficiently described within the literature. Therefore, the purpose of this study was to examine the association of apolipoproteins with measures of vascular structure and function in pediatric population. Hypothesis: We hypothesized apolipoprotein AI, AII, and CII would demonstrate a positive association, and apolipoprotein B, B/AI ratio, CIII, CIII/CII ratio, and E a negative association with carotid intima-media thickness (cIMT) and carotid-radial pulse wave velocity (PWV). Methods: A cross-sectional study of 338 children and adolescents (160 males, 178 females) aged 8-21 years (mean age 13.0±2.8 years) with a range of adiposities from normal body weight to severe obesity (mean BMI 26.8±8.9 kg/m 2 ). Apolipoproteins (AI, AII, B, CII, CIII, and E) were measured via human apolipoprotein magnetic bead panel (Millipore, MA, USA). Ultrasound imaging of the carotid artery was used to measure cIMT. PWV, a measure of arterial stiffness, was assessed via applanation tonometry (SphygmoCor TM ). Total body fat percent (BF%) was measured using dual X-ray absorptiometry. Linear regression models were adjusted for Tanner stage, sex, and race with further adjustments for BF%. Data are presented as mean [95% CI] with Holms-adjusted p-values to account for multiple testing. All apolipoprotein ratios were scaled to 0.1 μg/mL. Methods: There were significant positive associations between PWV and apolipoproteins: AII (0.036 m/sec per 10 μg/mL [0.017, 0.056], p = 0.010), E (0.158 m/sec per 10 μg/mL [0.08, 0.235], p = 0.002), and CIII/CII ratio (0.033 [0.014, 0.052], p = 0.019). After adding BF% to the models, PWV remained positively associated with higher levels of apolipoproteins: AII (0.036 m/sec per 10 μg/mL [0.016, 0.055], p = 0.012), E (0.161 m/sec per 10 μg/mL [0.082, 0.239], p = 0.002), and CIII/CII ratio (0.033 [0.014, 0.052], p = 0.02). Before accounting for multiple testing, apolipoprotein CIII/CII ratio was positively associated with cIMT (0.001 [0, 0.003], p = 0.033), but failed to maintain significance after p-value correction. Otherwise, there were no significant associations between any apolipoprotein and cIMT in the presence or absence of BF%. Conclusions: These findings suggest higher levels of apolipoprotein AII, E, and CIII/CII ratio are associated with higher arterial stiffness (PWV) in pediatrics, both in the presence and absence of excess body fat. Apolipoproteins, specifically AII, E, and CIII/CII ratio, may exert their effects on vascular function (PWV) before altering vascular structure (cIMT), which is congruent with the chronological pathophysiology of atherosclerosis.

Serum proteomics analysis based on label-free revealed the protective effect of Chinese herbal formula Gu-Ben-Fang-Xiao

Gubenfangxiao decoction (GBFXD) is a traditional Chinese medicine formula derived from Yupingfengsan, an ancient formula widely used to treat respiratory diseases. In recent years, GBFXD has been applied to efficaciously and safely treat asthma. However, the mechanism of GBFXD is still not fully elucidated. The aim of this study was to employ the label-free proteomic method to explore the protective mechanism of GBFXD in respiratory syncytial virus (RSV)-ovalbumin (OVA) induced chronic persistent asthmatic mice. After RSV-OVA challenge, mice were orally administered GBFXD at a dose of 36 g/kg accompanied with OVA nasal spray once every 3 days for 28 days. The label-free proteomics-based liquid chromatography-tandem mass spectrometry method was used to explore the differentially abundant proteins (DAPs) in the serum from model mice compared with that in control mice (M:C), and in GBFXD-treated mice compared with that in model mice (G:M). The mass spectrometry proteomics data have been deposited to the ProteomeXchange with identifier PXD013244. A total of 69 significant DAPs were identified including 39 in M:C, 46 in G:M, and 16 common differential proteins. Bioinformatics analysis revealed that the DAPs of M:C were mainly involved in inflammatory response and were related to lipid metabolism. However, the DAPs of G:M mostly participated in stress response, inflammatory response, and epithelial cell proliferation. Serum levels of Apoa-1, Apoc-1, Cfd, and Lrg1, EGFR and Lrg1 in the lungs were consistent with the results of proteomic analysis. Apoa-1 and Apoc-1 were closely related to cholesterol transport, lipid metabolism balance, and airway epithelial integrity; Cfd participated in immune response, affecting the occurrence and development of inflammation; EGFR and Lrg1 were involved in epithelial cell proliferation, influencing the process of airway remodeling.In summary, these results indicated that GBFXD may affect inflammatory and immune response of asthma by regulating cholesterol transport and complement factor activation. Furthermore, it could repair damaged airway epithelium and avoid airway remodeling to prevent and treat asthma.

Novel insights into the evolution of the caveolin superfamily and mechanisms of antiapoptotic effects and cell proliferation in lamprey

Caveolin-1 is the main structural and functional component of caveolin, and it is involved in the regulation of cholesterol transport, endocytosis, and signal transduction. Moreover, changes in caveolin-1 play an important role in tumorigenesis and inflammatory processes. Previous studies have demonstrated that human caveolin-1 is mainly located in the cell membrane and exhibits cell type- and stage-dependent functional differences during cancer development and inflammatory responses. However, the role of Lamprey-caveolin-like (L-caveolin-like) in lamprey remained unknown. Here, we demonstrated that L-caveolin-like performs anti-inflammation and oncogenic functions and the function of caveolin-1 diverged during vertebrate evolution. Moreover, the results reveal the mechanism underlying the antiapoptotic effects of L-caveolin-like. An L-caveolin-like gene from Lampetra japonica (L. japonica) was identified and characterized. L-Caveolin-like was primarily distributed in the leukocytes, intestines and supraneural bodies (Sp-bodies) immune organs as indicated by Q-PCR and immunohistochemistry assays. The mRNA and protein expression levels of L-caveolin exhibited consistent increases in expression at 2 and 72 h in adult tissues after exposure to lipopolysaccharide (LPS) and in leukocytes stimulated by Vibrio anguillarum (V. anguillarum), Staphylococcus aureus (S. aureus), and Poly I:C. Furthermore, the overexpression of pEGFP-N1-L-caveolin-like was associated with a distinct localization in mitochondria, with decreased cytochrome C (Cyt C) and mitochondrial Cyt C oxidase subunit I (CO I) expression. In addition, increased cellular ATP levels suggested that this protein prevented mitochondrial damage. The overexpression of pEGFP-N1-L-caveolin-like led to the altered expression of factors related to apoptosis, such as decreased Caspase-9, Caspase-3, p53, and Bax expression and increased Bcl-2 expression. In addition, the overexpression of pEGFP-N1-L-caveolin-like promoted cell proliferation associated with upregulated EGF, bFGF, and PDGFB expression. Together, these findings indicated that the L-caveolin-like protein from L. japonica induced the activation of antiapoptotic effects via the mitochondrial Cyt C-mediated Caspase-3 signaling pathway. Our analysis further suggests that L-caveolin-like is an oncogene protein product and anti-inflammatory molecule from lamprey that evolved early in vertebrate evolution.

ABCA1 overexpression worsens colorectal cancer prognosis by facilitating tumour growth and caveolin‐1‐dependent invasiveness, and these effects can be ameliorated using the BET inhibitor apabetalone

At the time of diagnosis, 20% of patients with colorectal cancer present metastasis. Among individuals with primary lesions, 50% of them will develop distant tumours with time. Therefore, early diagnosis and prediction of aggressiveness is crucial for therapy design and disease prognosis. Tumoral cells must undergo significant changes in energy metabolism to meet increased structural and energetic demands for cell proliferation, and metabolic alterations are considered to be a hallmark of cancer. Here, we present the ATP‐binding cassette transporter (ABCA1), a regulator of cholesterol transport, as a new marker for invasion and colorectal cancer survival. ABCA1 is significantly overexpressed in patients at advanced stages of colorectal cancer, and its overexpression confers proliferative advantages together with caveolin‐1 dependent‐increased migratory and invasive capacities. Thus, intracellular cholesterol imbalances mediated by ABCA1 overexpression may contribute to primary tumour growth and dissemination to distant locations. Furthermore, we demonstrate here that increased levels of apolipoprotein A1 (APOA1), a protein involved in cholesterol efflux and high‐density lipoprotein constitution, in the extracellular compartment modulates expression of ABCA1 by regulating COX‐2, and compensate for ABCA1‐dependent excessive export of cholesterol. APOA1 emerges as a new therapeutic option to inhibit the promotion of colorectal cancer to metastasis by modulating intracellular cholesterol metabolism. Furthermore, we propose apabetalone, an orally available small molecule that is currently being evaluated in clinical trials for the treatment of atherosclerosis, as a new putative therapeutic option to prevent colorectal cancer progression by increasing APOA1 expression and regulating reverse transport of cholesterol.

The anti-cholesterolaemic effect of a consortium of probiotics: An acute study in C57BL/6J mice

Hypercholesterolaemia is a major risk factor for cardiovascular disease and it has been found that some probiotic bacteria possess cholesterol-lowering capabilities. In this study, the ability of the Lab4 probiotic consortium to hydrolyse bile salts, assimilate cholesterol and regulate cholesterol transport by polarised Caco-2 enterocytes was demonstrated. Furthermore, in wild-type C57BL/6J mice fed a high fat diet, 2-weeks supplementation with Lab4 probiotic consortium plus Lactobacillusplantarum CUL66 resulted in significant reductions in plasma total cholesterol levels and suppression of diet-induced weight gain. No changes in plasma levels of very low-density lipoprotein/low-density lipoprotein, high-density lipoprotein, triglycerides, cytokines or bile acids were observed. Increased amounts of total and unconjugated bile acids in the faeces of the probiotic-fed mice, together with modulation of hepatic small heterodimer partner and cholesterol-7α-hydroxylase mRNA expression, implicates bile salt hydrolase activity as a potential mechanism of action. In summary, this study demonstrates the cholesterol-lowering efficacy of short-term feeding of the Lab4 probiotic consortium plus L. plantarum CUL66 in wild-type mice and supports further assessment in human trials.