Potential role of acyl-coenzyme A:cholesterol transferase (ACAT) Inhibitors as hypolipidemic and antiatherosclerosis drugs

Bacterial polyynes uncovered: a journey through their bioactive properties, biosynthetic mechanisms, and sustainable production strategies

Covering: up to 2023Conjugated polyynes are natural compounds characterized by alternating single and triple carbon-carbon bonds, endowing them with distinct physicochemical traits and a range of biological activities. While traditionally sourced mainly from plants, recent investigations have revealed many compounds originating from bacterial strains. This review synthesizes current research on bacterial-derived conjugated polyynes, delving into their biosynthetic routes, underscoring the variety in their molecular structures, and examining their potential applications in biotechnology. Additionally, we outline future directions for metabolic and protein engineering to establish more robust and stable platforms for their production.

Unveiling the molecular mechanisms: dietary phytosterols as guardians against cardiovascular diseases

Until recently, the main pharmaceuticals used to control cholesterol and prevent cardiovascular disease (CVD) were statin-related drugs, known for their historical side effects. Therefore, there is growing interest in exploring alternatives, such as nutritional and dietary components, that could play a central role in CVD prevention. This review aims to provide a comprehensive understanding of how natural phytosterols found in various diets combat CVDs. We begin with a description of the overall approach, then we explore in detail the different direct and indirect mechanisms that contribute to reducing cardiovascular incidents. Phytosterols, including stigmasterol, β-sitosterol, ergosterol, and fucosterol, emerge as promising molecules within nutritional systems for protection against CVDs due to their beneficial effects at different levels through direct or indirect cellular, subcellular, and molecular mechanisms. Specifically, the mentioned phytosterols exhibit the ability to diminish the generation of various radicals, including hydroperoxides and hydrogen peroxide. They also promote the activation of antioxidant enzymes such as superoxide dismutase, catalase, and glutathione, while inhibiting lipid peroxidation through the activation of Nrf2 and Nrf2/heme oxygenase-1 (HO-1) signaling pathways. Additionally, they demonstrate a significant inhibitory capacity in the generation of pro-inflammatory cytokines, thus playing a crucial role in regulating the inflammatory/immune response by inhibiting the expression of proteins involved in cellular signaling pathways such as JAK3/STAT3 and NF-κB. Moreover, phytosterols play a key role in reducing cholesterol absorption and improving the lipid profile. These compounds can be used as dietary supplements or included in specific diets to aid control cholesterol levels, particularly in individuals suffering from hypercholesterolemia.

Antioxidant, LC-MS Analysis, and Cholinesterase Inhibitory Potentials of Phoenix dactylifera Cultivar Khudari: An In Vitro Enzyme Kinetics and In Silico Study

We evaluated the therapeutic potentials of Khudari fruit pulp, a functional food and cultivar of Phoenix dactylifera, against neurological disorders. Our results demonstrate a good amount of phytochemicals (total phenolic content: 17.77 ± 8.21 µg GA/mg extract) with a high antioxidant potential of aqueous extract (DPPH assay IC50 = 235.84 ± 11.65 µg/mL) and FRAP value: 331.81 ± 4.56 µmol. Furthermore, the aqueous extract showed the marked inhibition of cell-free acetylcholinesterase (electric eel) with an IC50 value of 48.25 ± 2.04 µg/mL, and an enzyme inhibition kinetics study revealed that it exhibits mixed inhibition. Thereafter, we listed the 18 best-matched phytochemical compounds present in aqueous extract through LC/MS analysis. The computational study revealed that five out of eighteen predicted compounds can cross the BBB and exert considerable aqueous solubility. where 2-{5-[(1E)-3-methylbuta-1,3-dien-1-yl]-1H-indol-3-yl}ethanol (MDIE) indicates an acceptable LD50. value. A molecular docking study exhibited that the compounds occupied the key residues of acetylcholinesterase with ΔG range between -6.91 and -9.49 kcal/mol, where MDIE has ∆G: -8.67 kcal/mol, which was better than that of tacrine, ∆G: -8.25 kcal/mol. Molecular dynamics analyses of 100 ns supported the stability of the protein-ligand complexes analyzed through RMSD, RMSF, Rg, and SASA parameters. TRP_84 and GLY_442 are the most critical hydrophobic contacts for the complex, although GLU_199 is important for H-bonds. Prime/MM-GBSA showed that the protein-ligand complex formed a stable confirmation. These findings suggest that the aqueous extract of Khudari fruit pulp has significant antioxidant and acetylcholinesterase inhibition potentials, and its compound, MDIE, forms stably with confirmation with the target protein, though this fruit of Khudari dates can be a better functional food for the treatment of Alzheimer's disease. Further investigations are needed to fully understand the therapeutic role of this plant-based compound via in vivo study.

Tear film impairment and meibomian gland loss in patients with polycystic ovary syndrome

OBJECTIVE

The aim of this prospective study is to comparatively assess the tear film, meibomian gland (MG), cornea and anterior chamber parameters and also subjective ocular complaints in patients with polycystic ovary syndrome (PCOS) and healthy control subjects.

MATERIALS AND METHODS

We included 53 eyes of the 53 patients diagnosed with PCOS and 57 eyes of the 57 healthy control subjects (who are non-pregnant, none of the following clinical findings of male pattern hair loss, hirsutism or acne and with regular menstrual cycles, who have no laboratory findings in her medical history that indicate hyperandrogenism, and who have ovaries that appear to be normal ultrasonographically. All subjects were referred to the masked ophthalmologist by the obstetrician and gynecologist. Participants underwent evaluation of the non-invasive tear film break-up time test (NI-BUT); loss of MGs by non-contact meibography, evaluation of cornea and anterior chamber parameters, and evaluation of subjective ocular complaints using the ocular surface disease index (OSDI).

RESULTS

The mean age of PCOS group and controls was 25.08 ± 4.88 and 25.44 ± 5.00 years, respectively. There was no statistically significant difference between the PCOS and control groups in terms of age (p = 0.732). Mean non-invasive first tear film breakup times (NIF-BUT) values of PCOS group and controls were 6.15 ± 4.99 and 10.48 ± 5.81 s, and mean non-invasive average tear film breakup times (NIAvg-BUT) values of PCOS group and controls were 8.48 ± 4.27 and 11.94 ± 4.64 s, respectively; both cases refer to a significant difference between the groups (p = 0.000). In PCOS group, loss of MG in the upper lids was 40.21%, in the lower lids was 53.45%; on the other hand, in control group 15.76% and 21.47%, respectively; both cases refer to a significant difference between the groups (p = 0.000). The number of patients with abnormal OSDI scores (scores ≥ 13 points) was significantly higher in PCOS group (54.7%) than in controls (19.3%) (p = 0.000). Anterior chamber volume (ACV) measured by the topography device in PCOS group was significantly lower (156.5 and 167.4) (p = 0.024).

CONCLUSION

Findings of this study indicated that tear film stability impaired in patients with PCOS and that this impairment was accompanied by the loss of MG, which play a key role in tear film stability.

Antihyperlipidemic Activity of Gut-Restricted LXR Inverse Agonists

Hyperlipidemia and increased circulating cholesterol levels are associated with increased cardiovascular disease risk. The liver X receptors (LXRs) are regulators of de novo lipogenesis and cholesterol transport and have been validated as potential therapeutic targets for the treatment of atherosclerosis. However, efforts to develop LXR agonists to reduce cardiovascular diseases have failed due to poor clinical outcomes-associated increased hepatic lipogenesis and elevated low-density lipoprotein (LDL) cholesterol (C). Here, we report that LXR inverse agonists are effective in lowering plasma LDL cholesterol and triglycerides in several models of hyperlipidemia, including the Ldlr null mouse model of atherosclerosis. Mechanistic studies demonstrate that LXR directly regulates the expression of Soat2 enzyme in the intestine, which is directly responsible for the re-uptake or excretion of circulating lipids. Oral administration of a gut-specific LXR inverse agonist leads to reduction of Soat2 expression in the intestine and effectively lowers circulating LDL cholesterol and triglyceride levels without modulating LXR target genes in the periphery. In summary, our studies highlight the therapeutic potential of the gut-restricted molecules to treat hyperlipidemia and atherosclerosis through the intestinal LXR-Soat2 axis.

Connecting the Dots Between Hypercholesterolemia and Alzheimer’s Disease: A Potential Mechanism Based on 27-Hydroxycholesterol

Alzheimer’s disease (AD), the most common cause of dementia, is a complex and multifactorial disease involving genetic and environmental factors, with hypercholesterolemia considered as one of the risk factors. Numerous epidemiological studies have reported a positive association between AD and serum cholesterol levels, and experimental studies also provide evidence that elevated cholesterol levels accelerate AD pathology. However, the underlying mechanism of hypercholesterolemia accelerating AD pathogenesis is not clear. Here, we review the metabolism of cholesterol in the brain and focus on the role of oxysterols, aiming to reveal the link between hypercholesterolemia and AD. 27-hydroxycholesterol (27-OHC) is the major peripheral oxysterol that flows into the brain, and it affects β-amyloid (Aβ) production and elimination as well as influencing other pathogenic mechanisms of AD. Although the potential link between hypercholesterolemia and AD is well established, cholesterol-lowering drugs show mixed results in improving cognitive function. Nevertheless, drugs that target cholesterol exocytosis and conversion show benefits in improving AD pathology. Herbs and natural compounds with cholesterol-lowering properties also have a potential role in ameliorating cognition. Collectively, hypercholesterolemia is a causative risk factor for AD, and 27-OHC is likely a potential mechanism for hypercholesterolemia to promote AD pathology. Drugs that regulate cholesterol metabolism are probably beneficial for AD, but more research is needed to unravel the mechanisms involved in 27-OHC, which may lead to new therapeutic strategies for AD.

Immune Checkpoint Therapies and Atherosclerosis: Mechanisms and Clinical Implications: JACC State-of-the-Art Review

Immune checkpoint inhibitor therapy has revolutionized the treatment of advanced malignancies in recent years. Numerous reports have detailed the myriad of possible adverse inflammatory effects of immune checkpoint therapies, including within the cardiovascular system. However, these reports have been largely limited to myocarditis. The critical role of inflammation and adaptive immunity in atherosclerosis has been well characterized in preclinical studies, and several emerging clinical studies indicate a potential role of immune checkpoint targeting therapies in the development and exacerbation of atherosclerosis. In this review, we provide an overview of the role of T-cell immunity in atherogenesis and describe the molecular effects and clinical associations of both approved and investigational immune checkpoint therapy on atherosclerosis. We also highlight the role of cholesterol metabolism in oncogenesis and discuss the implications of these associations on future treatment and monitoring of atherosclerotic cardiovascular disease in the oncologic population receiving immune checkpoint therapy.

ACAT2 Is a Novel Negative Regulator of Pig Intramuscular Preadipocytes Differentiation

Intramuscular fat (IMF) is considered as the fat deposited between muscle fibers. The extracellular matrix microenvironment of adipose tissue is of critical importance for the differentiation, remodeling and function of adipocytes. Therefore, in this study we extracted the muscle tissue centrifugal fluid (MTF) of the longissimus dorsi of Erhualian pigs to mimic the microenvironment of intramuscular pre-adipocytes. MTF of pigs with low intramuscular fat level can inhibit pig intramuscular pre-adipocytes differentiation. Then, proteomics technology (iTRAQ) was used to analyze the MTF with different IMF content, and it was found that individuals with high IMF had low ACAT2 (Acyl-CoA: cholesterol acyltransferases 2) levels, while individuals with low IMF had high ACAT2 levels. Significant changes took place in the pathways involved in coenzyme A, which are closely related to fat and cholesterol metabolism. Therefore, we speculate that ACAT2, as an important element involved in cholesterol metabolism, may become a potential molecular marker for the mechanism of pig intramuscular preadipocytes differentiation. Overexpression of ACAT2 in pig intramuscular pre-adipocytes can inhibit their differentiation, while adding ACAT2 inhibitor avasimibe can rescue the process. Knockdown of srebp2 or ldlr, which are two key genes closely related to ACAT2 and cholesterol metabolism, can inhibit pig intramuscular pre-adipocytes differentiation. Overall, our results suggest that ACAT2 is a novel negative regulator of intramuscular adipocyte differentiation through regulation of pparγ, cebpα signaling and srebp2/ldlr signaling involved in cholesterol metabolism.

A guide to understanding endoplasmic reticulum stress in metabolic disorders

BACKGROUND

The global rise of metabolic disorders, such as obesity, type 2 diabetes, and cardiovascular disease, demands a thorough molecular understanding of the cellular mechanisms that govern health or disease. The endoplasmic reticulum (ER) is a key organelle for cellular function and metabolic adaptation and, therefore disturbed ER function, known as "ER stress," is a key feature of metabolic disorders.

SCOPE OF REVIEW

As ER stress remains a poorly defined phenomenon, this review provides a general guide to understanding the nature, etiology, and consequences of ER stress in metabolic disorders. We define ER stress by its type of stressor, which is driven by proteotoxicity, lipotoxicity, and/or glucotoxicity. We discuss the implications of ER stress in metabolic disorders by reviewing evidence implicating ER phenotypes and organelle communication, protein quality control, calcium homeostasis, lipid and carbohydrate metabolism, and inflammation as key mechanisms in the development of ER stress and metabolic dysfunction.

MAJOR CONCLUSIONS

In mammalian biology, ER is a phenotypically and functionally diverse platform for nutrient sensing, which is critical for cell type-specific metabolic control by hepatocytes, adipocytes, muscle cells, and neurons. In these cells, ER stress is a distinct, transient state of functional imbalance, which is usually resolved by the activation of adaptive programs such as the unfolded protein response (UPR), ER-associated protein degradation (ERAD), or autophagy. However, challenges to proteostasis also impact lipid and glucose metabolism and vice versa. In the ER, sensing and adaptive measures are integrated and failure of the ER to adapt leads to aberrant metabolism, organelle dysfunction, insulin resistance, and inflammation. In conclusion, the ER is intricately linked to a wide spectrum of cellular functions and is a critical component in maintaining and restoring metabolic health.

Unwanted Hormonal and Metabolic Effects of Postoperative Adjuvant Mitotane Treatment for Adrenocortical Cancer

Simple Summary

Mitotane is the only drug approved for treatment of adrenocortical cancer. Although mitotane is a derivative of the pesticide dichlorodiphenyltrichloroethane (DDT), limited data are available on its toxicity. Herein, we reported on the type and frequency of mitotane adverse events and on supportive therapies used to deal with toxicity in 74 mitotane-treated patients. Beyond the expected glucocorticoid insufficiency, a significant number of patients had a deficit of mineralocorticoid hormones, hypothyroid state and impaired testicular function, while fertile women frequently developed ovarian cysts during mitotane treatment. Multiple hormone replacement therapies were needed in >30% of patients. Statins were used in 50% of patients for significant hypercholesterolemia. Supportive therapies were able to revert the biochemical alterations, although higher doses were frequently used due to pharmacokinetic interactions with mitotane. Our study underlines the need of a careful and global approach to manage mitotane toxicity, to make adjuvant therapy safer and easier for patients.

Abstract

Mitotane is widely used for the treatment of adrenocortical cancer (ACC), although the drug-related toxicity complicates its use. The aim of this study is to assess comprehensively the different endocrine and metabolic unwanted effects of the drug, and to provide data on the supportive therapies. We retrospectively analyzed 74 ACC patients adjuvantly treated with mitotane for ≥12 months. During the treatment period (40 months, 12–195), 32.4% of patients needed replacement therapy for mineralocorticoid deficit, 36.2% for hypothyroidism and 34.3% for male hypogonadism. In fertile women, hypogonadism was uncommon, while 65.4% of women developed ovarian cysts. Although no significant change in low-density lipoprotein (LDL) was observed, statins were started in 50% of patients for a significant increase in total cholesterol and triglycerides. Dyslipidemia occurred early, after a median time of 6 months from mitotane start. Conversely, testosterone replacement was usually started after >2 years. In many cases, ranging from 29.4% to 50% according to the side effect, toxicity occurred well before the achievement of the target mitotane concentrations. Supportive therapies were able to revert the biochemical alterations induced by mitotane, although higher doses were needed for a likely pharmacokinetic interaction of exogenous steroids and statins with mitotane. In conclusion, adjuvant mitotane therapy is associated with a spectrum of unwanted effects encompassing the function of different endocrine glands and requires a careful clinical and biochemical assessment associated with the therapeutic drug monitoring.

Effects of nanoparticle-mediated delivery of pitavastatin on atherosclerotic plaques in ApoE-knockout mice and THP-1-derived macrophages

The treatment of atherosclerosis remains complex. Pitavastatin serves an important role in the prevention and treatment of atherosclerosis. The present study aimed to investigate the effects of nanoparticle (NP)-mediated delivery of pitavastatin into atherosclerotic plaques as a novel treatment method for atherosclerosis. The results of the present study demonstrated that pitavastatin-NP was more effective in attenuating the size of atherosclerotic plaques and enhancing the stability of plaques in vitro compared with pitavastatin alone. In an apolipoprotein E (ApoE)-knockout mouse model of atherosclerosis, a single intravenous injection of fluorescein isothiocyanate-NP resulted in the delivery of NP into atherosclerotic plaques for up to 7 days post-injection. In ApoE-knockout mice and THP-1-derived macrophages, pitavastatin-NP attenuated the development of atherosclerosis, which was associated with regulating lipid metabolism, and inhibited the secretion of inflammatory markers compared with pitavastatin alone. Additionally, the treatment advantages of pitavastatin-NP were independent of lipid lowering. The results demonstrated that pitavastatin-NP administration was more effective in attenuating the development of atherosclerotic plaques compared with systemic administration of pitavastatin.

Recombinant Klotho protein enhances cholesterol efflux of THP-1 macrophage-derived foam cells via suppressing Wnt/β-catenin signaling pathway

BACKGROUND

Atherosclerosis (AS) is the basis of cardiovascular diseases, characterized by chronic inflammatory and lipid metabolism disorders. Although the anti-inflammatory effect of Klotho in AS has been clearly shown, its lipid-lowering effect is unclear. In this study, we examined the effects of recombinant Klotho (Re-KL) protein on lipid accumulation in foam cells.

METHODS

THP-1 cells were exposed to 100 nM phorbol myristate acetate for 24 h and then to oxidized low-density lipoprotein (ox-LDL; 80 mg/mL) to induce foam cell formation. Subsequently, the foam cells were incubated with Re-KL and/or DKK1, an inhibitor of the Wnt/β-catenin pathway.

RESULTS

Oil red O staining and cholesterol intake assay revealed that the foam cell model was constructed successfully. Pre-treatment of the foam cells with Re-KL decreased total cholesterol level, up-regulated the expression of ATP binding cassette transporter A1 (ABCA1) and G1 (ABCG1), and down-regulated the expression of acyl coenzyme a-cholesterol acyltransferase 1 (ACAT1) and members of the scavenger family (SR-A1 and CD36). In addition, the expression of Wnt/β-catenin pathway-related proteins in foam cells was significantly decreased by the stimulus of Re-KL. Interestingly, the effect of Re-KL was similar to that of DKK1 on foam cells.

CONCLUSIONS

The Re-KL-induced up-regulation of reverse cholesterol transport capacity promotes cholesterol efflux and reduces lipid accumulation by suppressing the Wnt/β-catenin pathway in foam cells.

Enhanced chemo-immunotherapy against melanoma by inhibition of cholesterol esterification in CD8+ T cells

Cholesterol facilitated the formation of T cell receptor on cytotoxic CD8⁺ T lymphocytes (CTLs). However, the activation of CD8⁺ T cells always resulted in the upregulation of acetyl-CoA acetyltransferase-1 (ACAT-1) and enhanced the esterification of cholesterol. To relieve the suppression on CD8⁺ T cells, an ACAT-1 inhibitor avasimibe was combined with chemo-immunotherapy. Paclitaxel and immunoadjuvant αGC were co-encapsulated in liposomes modified with pH sensitive TH peptide (PTX/αGC-TH-Lip). After intravenous injections, the combination of avasimibe significantly elevated the free cholesterol level and relieved the inhibition of CD8⁺ T cells caused by PTX/αGC-TH-Lip, leading to enhanced CTL responses and anti-tumor effects of PTX/αGC-TH-Lip in B16F10 melanoma xenograft and lung metastasis models. The adoptive immunotherapy further confirmed the enhanced anti-tumor immune responses of the combined strategy. The combination of avasimibe and PTX/αGC-TH-Lip was proven as a feasible approach to enhance the antitumor effects of chemo-immunotherapy by relieving the inhibition of CD8⁺ T cells.

ATR-101, a Selective and Potent Inhibitor of Acyl-CoA Acyltransferase 1, Induces Apoptosis in H295R Adrenocortical Cells and in the Adrenal Cortex of Dogs

ATR-101 is a novel, oral drug candidate currently in development for the treatment of adrenocortical cancer. ATR-101 is a selective and potent inhibitor of acyl-coenzyme A:cholesterol O-acyltransferase 1 (ACAT1), an enzyme located in the endoplasmic reticulum (ER) membrane that catalyzes esterification of intracellular free cholesterol (FC). We aimed to identify mechanisms by which ATR-101 induces adrenocortical cell death. In H295R human adrenocortical carcinoma cells, ATR-101 decreases the formation of cholesteryl esters and increases FC levels, demonstrating potent inhibition of ACAT1 activity. Caspase-3/7 levels and terminal deoxynucleotidyl transferase 2'-deoxyuridine 5'-triphosphate nick end labeled-positive cells are increased by ATR-101 treatment, indicating activation of apoptosis. Exogenous cholesterol markedly potentiates the activity of ATR-101, suggesting that excess FC that cannot be adequately esterified increases caspase-3/7 activation and subsequent cell death. Inhibition of calcium release from the ER or the subsequent uptake of calcium by mitochondria reverses apoptosis induced by ATR-101. ATR-101 also activates multiple components of the unfolded protein response, an indicator of ER stress. Targeted knockdown of ACAT1 in an adrenocortical cell line mimicked the effects of ATR-101, suggesting that ACAT1 mediates the cytotoxic effects of ATR-101. Finally, in vivo treatment of dogs with ATR-101 decreased adrenocortical steroid production and induced cellular apoptosis that was restricted to the adrenal cortex. Together, these studies demonstrate that inhibition of ACAT1 by ATR-101 increases FC, resulting in dysregulation of ER calcium stores that result in ER stress, the unfolded protein response, and ultimately apoptosis.

Potentiating the antitumour response of CD8(+) T cells by modulating cholesterol metabolism

CD8(+) T cells have a central role in antitumour immunity, but their activity is suppressed in the tumour microenvironment. Reactivating the cytotoxicity of CD8(+) T cells is of great clinical interest in cancer immunotherapy. Here we report a new mechanism by which the antitumour response of mouse CD8(+) T cells can be potentiated by modulating cholesterol metabolism. Inhibiting cholesterol esterification in T cells by genetic ablation or pharmacological inhibition of ACAT1, a key cholesterol esterification enzyme, led to potentiated effector function and enhanced proliferation of CD8(+) but not CD4(+) T cells. This is due to the increase in the plasma membrane cholesterol level of CD8(+) T cells, which causes enhanced T-cell receptor clustering and signalling as well as more efficient formation of the immunological synapse. ACAT1-deficient CD8(+) T cells were better than wild-type CD8(+) T cells at controlling melanoma growth and metastasis in mice. We used the ACAT inhibitor avasimibe, which was previously tested in clinical trials for treating atherosclerosis and showed a good human safety profile, to treat melanoma in mice and observed a good antitumour effect. A combined therapy of avasimibe plus an anti-PD-1 antibody showed better efficacy than monotherapies in controlling tumour progression. ACAT1, an established target for atherosclerosis, is therefore also a potential target for cancer immunotherapy.

Effect of ezetimibe plus pravastatin on endothelial dysfunction in patients with systemic lupus erythematosus

BACKGROUND

Patients with systemic lupus erythematosus (SLE) have a higher risk for cardiovascular disease (CVD), not fully explained by the conventional risk factors. These patients have endothelial dysfunction (ED) as an early process of atherosclerosis, which can be reversed with therapy.

OBJECTIVE

To determine the effect of ezetimibe plus pravastatin on endothelial function in patients with SLE after 12 months of treatment.

PATIENTS AND METHODS

An open study, before and after, which assessed the effect of ezetimibe plus pravastatin treatment, was performed. Twenty two patients (21 women and one man) with diagnosis of SLE were studied, with a mean age 40 ± 5 years. Endothelial dysfunction was evaluated using vascular ultrasound of the brachial artery in order to measure the flow-mediated vasodilation (FMV) basal and after 12 months of treatment with pravastatin 40 mg/day plus ezetimibe 10 mg/day. In addition, a lipid profile: total cholesterol (TC), HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C), and serum C-reactive protein (CRP), was done.

RESULTS

We found a basal FMV of 7.58% and 18.22% after 12 months of treatment, with an improvement of 10.64 points 95% CI (7.58-13.58), p < 0.001. TC decreased from 201.3 ± 58.9 mg/dL to 158.06 ± 50.13 mg/dL (p < 0.01); LDL-C from 125.78 ± 44.4 mg/dL to 78.8 ± 32.9 mg/dL (p < 0.001); HDL-C increased from 49.0 ± 16.8 mg/dL to 52.2 ± 13.8 mg/dL (p = 0.077). The basal and final concentrations of CRP were 4.49 and 2.8, respectively, with a mean decrease of 2.11 mg/dL, 95% CI (0.908-3.32), p < 0.002. Both drugs were well tolerated.

CONCLUSION

Ezetimibe plus pravastatin significantly improved FMV in patients with SLE, decreasing ED and the lipid profile. This treatment ameliorated an early process of atherosclerosis and a risk factor for CVD.

Cholesterol Absorption and Metabolism

Inhibitors of cholesterol absorption have been sought for decades as a means to treat and prevent cardiovascular diseases (CVDs) associated with hypercholesterolemia. Ezetimibe is the one clear success story in this regard, and other compounds with similar efficacy continue to be sought. In the last decade, the laboratory mouse, with all its genetic power, has become the premier experimental model for discovering the mechanisms underlying cholesterol absorption and has become a critical tool for preclinical testing of potential pharmaceutical entities. This chapter briefly reviews the history of cholesterol absorption research and the various gene candidates that have come under consideration as drug targets. The most common and versatile method of measuring cholesterol absorption is described in detail along with important considerations when interpreting results, and an alternative method is also presented. In recent years, reverse cholesterol transport (RCT) has become an area of intense new interest for drug discovery since this process is now considered another key to reducing CVD risk. The ultimate measure of RCT is sterol excretion and a detailed description is given for measuring neutral and acidic fecal sterols and interpreting the results.

Evolving targets for lipid-modifying therapy

The pathogenesis and progression of atherosclerosis are integrally connected to the concentration and function of lipoproteins in various classes. This review examines existing and emerging approaches to modify low-density lipoprotein and lipoprotein (a), triglyceride-rich lipoproteins, and high-density lipoproteins, emphasizing approaches that have progressed to clinical evaluation. Targeting of nuclear receptors and phospholipases is also discussed.

[Microbial metabolites that inhibit sterol biosynthesis, their chemical diversity and characteristics of mode of action]

Inhibitors of sterol biosynthesis (ISB) are widespread in nature and characterized by appreciable diversity both in their chemical structure and mode of action. Many of these inhibitors express noticeable biological activity and approved themselves in development of various pharmaceuticals. In this review there is a detailed description of biologically active microbial metabolites with revealed chemical structure that have ability to inhibit sterol biosynthesis. Inhibitors of mevalonate pathway in fungous and mammalian cells, exhibiting hypolipidemic or antifungal activity, as well as inhibitors of alternative non-mevalonate (pyruvate gliceraldehyde phosphate) isoprenoid pathway, which are promising in the development of affective antimicrobial or antiparasitic drugs, are under consideration in this review. Chemical formulas of the main natural inhibitors and their semi-synthetic derivatives are represented. Mechanism of their action at cellular and biochemical level is discussed. Special attention is given to inhibitors of 3-hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) reductase (group of lovastatin) and inhibitors of acyl-CoA-cholesterol-acyl transferase (ACAT) that possess hypolipidemic activity and could be affective in the treatment of atherosclerosis. In case of inhibitors of late stages of sterol biosynthesis (after squalene formation) special attention is paid to compounds possessing evident antifungal and antitumoral activity. Explanation of mechanism of anticancer and antiviral action of microbial ISB, as well as the description of their ability to induce apoptosis is given.

Basis of aggravated hepatic lipid metabolism by chronic stress in high-fat diet-fed rat

Our previous study has demonstrated that long-term stress, known as chronic stress (CS), can aggravate nonalcoholic fatty liver disease in high-fat diet (HFD)-fed rat. In this study, we tried to figure out which lipid metabolic pathways were impacted by CS in the HFD-fed rat. Male Sprague-Dawley rats (6 weeks of age, n = 8 per group) were fed with either standard diet or HFD with or without CS exposure for 8 weeks. Hepatic lipidosis, biochemical, hormonal, and lipid profile markers in serum and liver, and enzymes involved in de novo lipogenesis (DNL) of fatty acids (FAs) and cholesterol, β-oxidation, FAs uptake, triglycerides synthesis, and very low-density lipoprotein (VLDL) assembly in the liver were detected. CS exposure reduced hepatic lipidosis but further elevated hepatic VLDL content with aggravated dyslipidemia in the HFD-fed rats. There was a synergism between CS and HFD on VLDL production and dyslipidemia. PCR and western blot assays showed that CS exposure significantly promoted hepatic VLDL assembly in rats, especially in the HFD-fed rats, while it had little impact on DNL, β-oxidation, FAs uptake, and triglycerides synthesis in the HFD-fed rats. This phenomenon was in accordance with elevated serum glucocorticoid level. The critical influence of CS exposure on hepatic lipid metabolism in the HFD-fed rats is VLDL assembly which might be regulated by glucocorticoid.

Berberine decreases cholesterol levels in rats through multiple mechanisms, including inhibition of cholesterol absorption

OBJECTIVE

The objective was to determine the mechanisms of action of berberine (BBR) on cholesterol homeostasis using in vivo and in vitro models.

METHODS

Male Sprague-Dawley rats were fed the AIN-93G diet (normal control) or modified AIN-93G diet containing 28% fat, 2% cholesterol and 0.5% cholic acid with treatment of 0 (atherogenic control), 50, 100, and 150 mg/kg·d of BBR, respectively by gavaging in water for 8 weeks. Cholesterol absorption rate was measured with the dual stable isotope ratio method, and plasma lipids were determined using the enzymatic methods. Gene and protein expressions of Acyl-coenzyme A:cholesterol acyltransferase-2 were analyzed in vivo and in vitro. Cholesterol micellarization, uptake and permeability were determined in vitro.

RESULTS

Rats on the atherogenic diet showed significantly hypercholesterolemic characteristics compared to normal control rats. Treatment with BBR in rats on the atherogenic diet reduced plasma total cholesterol and nonHDL cholesterol levels by 29%-33% and 31%-41%, respectively, with no significant differences being observed among the three doses. The fractional dietary cholesterol absorption rate was decreased by 40%-51%. Rats fed the atherogenic diet showed lower plasma triacylglycerol levels, and no changes were observed after the BBR treatment. BBR interfered with cholesterol micellarization, decreased cholesterol uptake by Caco-2 cells and permeability through Caco-2 monolayer. BBR also inhibited the gene and protein expressions of acyl-coenzyme A cholesterol acyltransferease-2 in the small intestine and Caco-2 cells.

CONCLUSION

BBR lowered blood cholesterol levels at least in part through inhibiting the intestinal absorption and further by interfering with intraluminal cholesterol micellarization and decreasing enterocyte cholesterol uptake and secretion.

Evaluation and prognostic significance of ACAT1 as a marker of prostate cancer progression

INTRODUCTION

Prostate cancer is the second leading cause of cancer-related death among men in North America. While a majority of prostate cancer cases remain indolent, subsets of patients develop aggressive cancers, which may lead to death. The current methods of detection include digital rectal examination and the serum PSA test. However, due to lack of specificity, neither of these approaches is able to accurately discriminate between indolent and aggressive cancer, which is why there is a need for additional prognostic factors. Previously, we identified enzymes of the ketogenic pathway, particularly ACAT1, to be elevated in aggressive prostate cancer.

METHODS

In the current study, we assessed the diagnostic and prognostic potential of ACAT1 by analyzing its expression using immunohistochemistry on a tissue microarray consisting of 251 clinically localized prostate cancer patients who have undergone radical prostatectomy.

RESULTS

Using quantitative digital imaging software, we found that ACAT1 expression was significantly greater in cancerous cores compared to adjacent benign cores (P < 0.0001), in Gleason score (GS) ≥8 cancers versus GS≤6 cancers (P < 0.0001), GS≥8 cancers versus GS7 cancers (P = 0.001), as well as pT3/pT4 versus pT2 cancers (P = 0.001). In addition, ACAT1 predicted biochemical recurrence in univariate (HR, 1.81, CI = 1.13-2.9, P = 0.0128), and multivariate models (HR, 1.69, CI = 1.01-2.81, P = 0.0431) including pre-operative PSA level, Gleason score and pathological stage. In univariate time-to-recurrence analysis, ACAT1 expression predicted recurrence in ERG negative cases (P = 0.0025), whereas ERG positive cases did not display any differences.

DISCUSSION

Taken together, these findings indicate that ACAT1 expression could serve as a potential prognostic marker in prostate cancer, specifically in differentiating indolent and aggressive forms of cancer.

Association between single nucleotide polymorphism rs1044925 and the risk of coronary artery disease and ischemic stroke

The present study was performed to clarify the association between the acyl-CoA:cholesterol acyltransferase-1 (ACAT-1) single nucleotide polymorphism (SNP) rs1044925 and the risk of coronary artery disease (CAD) and ischemic stroke (IS) in the Guangxi Han population. Polymerase chain reaction and restriction fragment length polymorphism was performed to determine the genotypes of the ACAT-1 SNP rs1044925 in 1730 unrelated subjects (CAD, 587; IS, 555; and healthy controls; 588). The genotypic and allelic frequencies of rs1044925 were significantly different between the CAD patients and controls (p = 0.015) and borderline different between the IS patients and controls (p = 0.05). The AC/CC genotypes and C allele were associated with a decreased risk of CAD and IS (CAD: p = 0.014 for AC/CC vs. AA, p = 0.022 for C vs. A; IS: p = 0.014 for AC/CC vs. AA; p = 0.017 for C vs. A). The AC/CC genotypes in the healthy controls, but not in CAD or IS patients, were associated with an increased serum high-density lipoprotein cholesterol (HDL-C) concentration. The present study shows that the C allele carriers of ACAT-1 rs1044925 were associated with an increased serum HDL-C level in the healthy controls and decreased risk in CAD and IS patients.

Deciphering molecular mechanism underlying hypolipidemic activity of echinocystic Acid

Our previous study showed that a triterpene mixture, consisting of echinocystic acid (EA) and oleanolic acid (OA) at a ratio of 4 : 1, dose-dependently ameliorated the hyperlipidemia and atherosclerosis in rabbits fed with high fat/high cholesterol diets. This study was aimed at exploring the mechanisms underlying antihyperlipidemic effect of EA. Molecular docking simulation of EA was performed using Molegro Virtual Docker (version: 4.3.0) to investigate the potential targets related to lipid metabolism. Based on the molecular docking information, isotope labeling method or spectrophotometry was applied to examine the effect of EA on the activity of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, acyl-CoA:cholesterol acyltransferase (ACAT), and diacylglycerol acyltransferase (DGAT) in rat liver microsomes. Our results revealed a strong affinity of EA towards ACAT and DGAT in molecular docking analysis, while low binding affinity existed between EA and HMG-CoA reductase as well as between EA and cholesteryl ester transfer protein. Consistent with the results of molecular docking, in vitro enzyme activity assays showed that EA inhibited ACAT and DGAT, with IC₅₀ values of 103 and 139 μM, respectively, and exhibited no significant effect on HMG-CoA reductase activity. The present findings suggest that EA may exert hypolipidemic effect by inhibiting the activity of ACAT and DGAT.

HPLC-FLD determination of NBD-cholesterol, its ester and other metabolites in cellular lipid extracts

22-[N(-7-Nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-23,24-bisnor-5-cholen-3β-ol (NBD-cholesterol), a fluorescent cholesterol analog, was an extragenous cholesterol tracer used to study cholesterol absorption and metabolism in cultured cells. In order to measure free intracellular cholesterol and its esters, a precise and sensitive method employing high-performance liquid chromatography/fluorescence detection (HPLC-FLD) was developed for the first time. Method validation showed a limit of detection at 30 ng/mL. The calibration curve was linear within the range of 0.0625-10.0 µg/mL (r(2) = 0.999). Accuracy and precision were highlighted by good recovery and low variations. Apart from NBD-cholesteryl oleate, two additional cellular metabolites of NBD-cholesterol, probably an isomer and an oxidation product, were determined in the lipid extracts of Caco-2 human colon adenocarcinoma cells according to mass spectrometry. In AC29 mouse malignant mesothelioma cells overexpressing acyl-CoA:cholesterol acyltransferase-1 (ACAT1) or ACAT2, only the oxidized metabolite was detected. Using the newly developed method, YIC-C8-434, a known ACAT inhibitor, was shown to inhibit ACAT activity in Caco-2 cells, as well as in AC29/ACAT1 or AC29/ACAT2 cells. In conclusion, the sensitive and specific HPLC-FLD method is a powerful tool for simultaneous quantification of intracellular NBD-cholesterol and its oleoyl-ester.

Quantitative proteomics reveals that enzymes of the ketogenic pathway are associated with prostate cancer progression

Prostate cancer is the most common malignancy and the second leading cause of cancer-related deaths in men. One common treatment is androgen-deprivation therapy, which reduces symptoms in most patients. However, over time, patients develop tumors that are androgen-independent and ultimately fatal. The mechanisms that cause this transition remain largely unknown, and as a result, there are no effective treatments against androgen-independent prostate cancer. As a model platform, we used the LNCaP cell line and its androgen-independent derivative, LNCaP-SF. Utilizing stable isotope labeling with amino acids in cell culture coupled to mass spectrometry, we assessed the differential global protein expression of the two cell lines. Our proteomic analysis resulted in the quantification of 3355 proteins. Bioinformatic prioritization resulted in 42 up-regulated and 46 down-regulated proteins in LNCaP-SF cells relative to LNCaP cells. Our top candidate, HMGCS2, an enzyme involved in ketogenesis, was found to be 9-fold elevated in LNCaP-SF cells, based on peptide ratios. After analyzing the remaining enzymes of this pathway (ACAT1, BDH1, HMGCL, and OXCT1), we observed increased expression of these proteins in the LNCaP-SF cells, which was further verified using Western blotting. To determine whether these enzymes were up-regulated in clinical samples, we performed quantitative PCR and immunohistochemistry on human prostate cancer tissues, from which we observed significantly increased transcript and protein levels in high-grade cancer (Gleason grade ≥ 8). In addition, we observed significant elevation of these enzymes in the LuCaP 96AI castration-resistant xenograft. Further assessment of ACAT1 on human castration-resistant metastatic prostate cancer tissues revealed substantially elevated expression of ACAT1 in these specimens. Taken together, our results indicate that enzymes of the ketogenic pathway are up-regulated in high-grade prostate cancer and could serve as potential tissue biomarkers for the diagnosis or prognosis of high-grade disease.

Effects of compound X, a novel potent inhibitor of acyl-coenzyme A:cholesterol O-acyltransferase, on the adrenal gland of rats

To investigate the adrenal toxicity of a novel inhibitor of acyl-coenzyme A:cholesterol O-acyltransferase, compound X (CX), histopathological examinations, fat staining, adrenal cholesterol measurement, blood biochemistry, plasma corticosterone and ACTH measurement, ACTH-stimulation assay, and adrenal gene-expression analyses were done in rats in repeated-dose studies (experiment 1: 0, 3, 10, 30 and 150mg/kg for 4, 8, 15 and 28 days; experiment 2: 0, 3, 10,30 and 150mg/kg for 28 days; experiment 3: 0, 10, 30, 100 and 300mg/kg for 28 days). CX induced morphologic changes such as vacuolation and hypertrophy in the zona fasciculata (ZF) at ≥10mg/kg, and eosinophilic changes in the ZF at 150mg/kg. Vacuolation decreased in a dose-dependent manner and was replaced by eosinophilic changes. Inflammatory and fibrous changes were observed at ≥30mg/kg. These changes were expressed at early stages of dosing and were not exacerbated by extension of the administration period. Oil-red-O/Filipin staining showed depletion of cholesterol ester in dose-dependent manner and enabled adrenal cholesterol measurement. Filipin staining also revealed vacuoles to be composed of cholesterol esters. No significant changes were observed during the dosing period of CX for plasma corticosterone and ACTH levels. Gene-expression analyses showed up-regulation of Star and Abca1 mRNA levels at 300mg/kg. In conclusion, CX induced adrenal toxicity, but CX did not influence adrenocortical functions, and exacerbation of adrenal toxicities by extension of the administration period was not observed. Up-regulation of genes related to the transport of FC, such as Star and Abca1, were observed in CX groups, and these genes may be involved in the maintenance of adrenal structure and function in rats given CX.

ACAT-selective and Nonselective DGAT1 Inhibition

Acyl-coenzyme A: cholesterol O-Acyltransferase (ACAT) and Acyl-coenzyme A: diacylglycerol O-acyltransferase (DGAT) enzymes play important roles in synthesizing neutral lipids, and inhibitors of these enzymes have been investigated as potential treatments for diabetes and other metabolic diseases. Administration of a Acyl-coenzyme A: diacylglycerol O-acyltransferase 1 (DGAT1) inhibitor with very limited cellular selectivity over ACAT resulted in significant adrenocortical degenerative changes in dogs. These changes included macrosteatotic vacuolation associated with adrenocyte cell death in the zonae glomerulosa and fasciculata and minimal to substantial mixed inflammatory cell infiltration and were similar to those described previously for some ACAT inhibitors in dogs. In the mouse, similar but only transient adrenocortical degenerative changes were seen as well as a distinctive nondegenerative reduction in cortical fine vacuolation. In the marmoset, only the distinctive nondegenerative reduction in cortical fine vacuolation was observed, suggesting that the dog, followed by the mouse, is the most sensitive species for cortical degeneration. Biochemical analysis of adrenal cholesterol and cholesteryl ester indicated that the distinctive reduction in cortical fine vacuolation correlated with a significant reduction in cholesteryl ester in the mouse and marmoset, whereas no significant reduction in cholestryl ester, but an increase in free cholesterol was observed in dogs. Administration of a DGAT1 inhibitor with markedly improved selectivity over ACAT to the marmoset and the mouse resulted in no adrenal pathology at exposures sufficient to cause substantial DGAT1 but not ACAT inhibition, thereby implicating ACAT rather than DGAT1 inhibition as the probable cause of the observed adrenal changes. Recognizing that the distinctive nondegenerative reduction in cortical fine vacuolation in the mouse could be used as a histopathological biomarker for an in vivo model of the more severe changes observed in dogs, the mouse has subsequently been used as a model to select DGAT1 inhibitors free of adrenocortical toxicity.

Dynamics of PPARs, fatty acid metabolism genes and lipid classes in eggs and early larvae of a teleost

Dietary long chain polyunsaturated fatty acids (FA) have been recognized of crucial importance in early development of vertebrates, contributing to the impressive morphological and physiological changes both as building blocks and to energy production. The importance of lipids along development depends on ontogenetic, phylogenetic and environmental parameters. The expression patterns of FA metabolism genes have not been characterized in developing fish embryos nor compared to lipid class profiles. Full lipid metabolism only occurred after hatching, as revealed by alterations in lipid profiles and FA gene expression. Nonetheless, transcriptional changes of some FA genes were already present in embryos at notochord formation. Many genes displayed an expression profile opposed to the decrease of lipids along the development, while others responded solely to starvation. Transcription of most genes involved in FA metabolism had a strong correlation to PPARs' mRNA levels (α1, α2, β, γ). The comparison of mRNA expression of the genes with the lipid profiles produced new insights into the FA metabolism and regulation during the development of turbot larvae, providing the basis for future studies including comparative approaches with other vertebrate species.

Dyslipidemia, statins and prostate cancer

Dyslipidemia and prostate cancer are two of the most common medical conditions affecting adult males in the USA. In recent years, a large volume of research has focused on investigating the relationship between these two disease processes as well as the effect of the cholesterol-lowering medications, such as 3-hydroxyl-3-methylglutaryl-coenzyme A reductase inhibitors (better known as 'statins'), on the development and progression of prostate cancer. While there is a paucity of prospective research, encouraging results have been reported in several retrospective clinical studies. Additionally, basic science research has identified interactions between lipids and prostate cancer cells in several key areas. This article will discuss recent clinical and basic science research examining the relationship between dyslipidemia, statins and prostate cancer.

Specific Kv1.3 blockade modulates key cholesterol-metabolism-associated molecules in human macrophages exposed to ox-LDL

Cholesterol-metabolism-associated molecules, including scavenger receptor class A (SR-A), lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), CD36, ACAT1, ABCA1, ABCG1, and scavenger receptor class B type I, can modulate cholesterol metabolism in the transformation from macrophages to foam cells. Voltage-gated potassium channel Kv1.3 has increasingly been demonstrated to play an important role in the modulation of macrophage function. Here, we investigate the role of Kv1.3 in modulating cholesterol-metabolism-associated molecules in human acute monocytic leukemia cell-derived macrophages (THP-1 macrophages) and human monocyte-derived macrophages exposed to oxidized LDL (ox-LDL). Human Kv1.3 and Kv1.5 channels (hKv1.3 and hKv1.5) are expressed in macrophages and form a heteromultimeric channel. The hKv1.3-E314 antibody that we had generated as a specific hKv1.3 blocker inhibited outward delayed rectifier potassium currents, whereas the hKv1.5-E313 antibody that we had generated as a specific hKv1.5 blocker failed. Accordingly, the hKv1.3-E314 antibody reduced percentage of cholesterol ester and enhanced apoA-I-mediated cholesterol efflux in THP-1 macrophages and human monocyte-derived macrophages exposed to ox-LDL. The hKv1.3-E314 antibody downregulated SR-A, LOX-1, and ACAT1 expression and upregulated ABCA1 expression in THP-1 macrophages and human monocyte-derived macrophages. Our results reveal that specific Kv1.3 blockade represents a novel strategy modulating cholesterol metabolism in macrophages, which benefits the treatment of atherosclerotic lesions.

Sex-specific association of ACAT-1 rs1044925 SNP and serum lipid levels in the hypercholesterolemic subjects

Background

Acyl-CoA:cholesterol acyltransferase (ACAT) is a key enzyme in cellular cholesterol homeostasis and in atherosclerosis. The cellular cholesterol efflux correlated with serum high-density lipoprotein cholesterol (HDL-C) concentrations has shown to be impaired in hyperlipidemic mice. The present study was carried out to clarify the association of ACAT-1 rs1044925 single nucleotide polymorphism (SNP) and serum lipid levels in the hyperlipidemic subjects.

Methods

A total of 821 unrelated subjects (hyperlipidemia, 476; normolipidemia, 345) aged 15-80 were included in the study. Genotyping of the ACAT-1 rs1044925 SNP was performed by polymerase chain reaction and restriction fragment length polymorphism combined with gel electrophoresis, and then confirmed by direct sequencing.

Results

There was no significant difference in the genotypic and allelic frequencies of ACAT-1 rs1044925 SNP between the normolipidemic and hyperlipidemic subjects. The levels of total cholesterol (TC), HDL-C and apolipoprotein (Apo) AI in hyperlipidemic subjects were different between the AA and AC/CC genotypes in male but not in female (P < 0.05-0.01), the C allele carriers had higher serum TC, HDL-C and ApoAI levels than the C allele noncarriers. The association of genotypes and serum HDL-C and ApoAI levels in hyperlipidemia was found mainly in the male subjects with hypercholesterolemia but not in those with hypertriglyceridemia. There were no significant differences in serum lipid levels between the AA and AC/CC genotypes in the normolipidemic subjects.

Conclusions

The present study shows that the C allele carriers of ACAT-1 rs1044925 SNP in male hyperlipidemic subjects had higher serum TC, HDL-C and ApoAI levels than the C allele noncarriers. There is a sex (male)-specific association of ACAT-1 rs1044925 SNP and serum HDL-C and ApoAI levels in the hypercholesterolemic subjects.

Aqueous extract of Gleditsia sinensis Lam. fruits improves serum and liver lipid profiles and attenuates atherosclerosis in rabbits fed a high-fat diet

ETHNOPHARMACOLOGICAL RELEVANCE

Gleditsia sinensis Lam. has been used in the traditional Chinese medicine as a chief ingredient of many polyherbal formulations for the treatment of obesity and thrombosis.

AIM OF THE STUDY

To evaluate the effects of Gleditsia sinensis Lam. fruit aqueous extract (GAE) on hyperlipidemia and atherosclerosis in Japanese white rabbits on a high fat diet.

MATERIALS AND METHODS

Rabbits were divided into four groups: the normal control with a normal diet, and high-fat diet-fed model group and GAE-treated groups supplemented with GAE (6 or 12 mg/kg/day, p.o.), respectively. The groups fed high-fat diets were given i.v. with bovine serum albumin (BSA) on the 4th week to induce atherosclerosis. The serum lipid profile, including triglycerides (TG), total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C), was determined on the 0th, 4th, 8th and 14th week, respectively. And the activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and creatine kinase (CK) were measured simultaneously. At the end of the experiment, the rabbits were sacrificed, and the atherosclerotic plaques as well as the histopathological changes of aorta and liver were assessed by oil-red or HE staining, respectively, and the aorta and liver lipid profiles were also assayed.

RESULTS

Results showed that the prophylactic treatment with GAE could significantly decrease the lipid levels of serum, aorta and liver, attenuate aortic atherosclerosis and improve aortic remodeling without the significant liver and muscle toxicity.

CONCLUSION

The present findings suggest that GAE can effectively attenuate the atherosclerotic at least through anti-hyperlipidemic activity and thus has the therapeutic potential in treating hyperlipidemia-related cardiovascular diseases.

Increased expression of acyl-coenzyme A: cholesterol acyltransferase-1 and elevated cholesteryl esters in the hippocampus after excitotoxic injury

Significant increases in levels of cholesterol and cholesterol oxidation products are detected in the hippocampus undergoing degeneration after excitotoxicity induced by the potent glutamate analog, kainate (KA), but until now, it is unclear whether the cholesterol is in the free or esterified form. The present study was carried out to examine the expression of the enzyme involved in cholesteryl ester biosynthesis, acyl-coenzyme A: cholesterol acyltransferase (ACAT) and cholesteryl esters after KA excitotoxicity. A 1000-fold greater basal mRNA level of ACAT1 than ACAT2 was detected in the normal brain. ACAT1 mRNA and protein were upregulated in the hippocampus at 1 and 2 weeks after KA injections, at a time of glial reaction. Immunohistochemistry showed ACAT1 labeling of oligodendrocytes in the white matter and axon terminals in hippocampal CA fields of normal rats, and loss of staining in neurons but increased immunoreactivity of oligodendrocytes, in areas affected by KA. Gas chromatography-mass spectrometry analyses confirmed previous observations of a marked increase in level of total cholesterol and cholesterol oxidation products, whilst nuclear magnetic resonance spectroscopy showed significant increases in cholesteryl ester species in the degenerating hippocampus. Upregulation of ACAT1 expression was detected in OLN93 oligodendrocytes after KA treatment, and increased expression was prevented by an antioxidant or free radical scavenger in vitro. This suggests that ACAT1 expression may be induced by oxidative stress. Together, our results show elevated ACAT1 expression and increased cholesteryl esters after KA excitotoxicity. Further studies are necessary to determine a possible role of ACAT1 in acute and chronic neurodegenerative diseases.

Propiconazole induces alterations in the hepatic metabolome of mice: relevance to propiconazole-induced hepatocarcinogenesis

Propiconazole is a mouse hepatotumorigenic fungicide and has been the subject of recent investigations into its carcinogenic mechanism of action. The goals of this study were (1) to identify metabolomic changes induced in the liver by increasing doses of propiconazole in mice, (2) to interpret these results with key previously reported biochemical, transcriptomic, and proteomic findings obtained from mouse liver under the same treatment conditions, and (3) to relate these alterations to those associated with the carcinogenesis process. Propiconazole was administered to male CD-1 mice in the feed for 4 days with six mice per feed level (500, 1250, and 2500 ppm). The 2500 ppm dose level had previously been shown to induce both adenocarcinomas and adenomas in mouse liver after a 2-year continuous feed regimen. Endogenous biochemicals were profiled using liquid chromatography/mass spectrometry and gas chromatography/mass spectrometry methods and 261 were detected. The most populous biochemical class detected was lipids, followed by amino acids and then carbohydrates. Nucleotides, cofactors and vitamins, energy, peptides, and xenobiotics were also represented. Of the biochemicals detected, 159 were significantly altered by at least one dose of propiconazole and many showed strong dose responses. Many alterations in the levels of biochemicals were found in the glycogen metabolism, glycolysis, lipolysis, carnitine, and the tricarboxylic acid cycle pathways Several groups of metabolomic responses were ascribed to the metabolism and clearance of propiconazole: glucuronate, glutathione, and cysteine pathways. Groups of metabolic responses supported previous hypotheses on key events that can lead to propiconazole-induced tumorigenesis: oxidative stress and increases in the cholesterol biosynthesis pathway. Groups of metabolomic responses identified biomarkers associated with neoplasia: increases in glycolysis and increases in the levels of spermidine, sarcosine, and pseudouridine. These results extended the companion transcriptomic and proteomic studies and provided a more complete understanding of propiconazole's effects in mouse liver.

Interplay between cholesterol and drug metabolism

Cholesterol biosynthetic and metabolic pathways contain several branching points towards physiologically active molecules, such as coenzyme Q, vitamin D, glucocorticoid and steroid hormones, oxysterols, or bile acids. Sophisticated regulatory mechanisms are involved in maintenance of the homeostasis of not only cholesterol but also other cholesterogenic molecules. In addition to endogenous cues, cholesterol homeostasis needs to accommodate also to exogenous cues that are imported into the body, such as chemicals and medications. Steroid and nuclear receptors together with sterol regulatory element-binding protein (SREBP) mediate the fine tuning of biosynthetic and metabolic routes as well as transports of cholesterol and its derivatives. Similarly, drug/xenobiotic metabolism is the subject to the feedback regulation of cytochrome P450 enzymes and transporters. The regulatory mechanisms that maintain the homeostasis of cholesterogenic molecules and are involved in drug metabolism share similarities. Cholesterol and cholesterogenic compounds (bile acids, glucocorticoids, vitamin D, etc.) regulate the xenosensor signaling in drug-mediated induction of the major drug-metabolizing cytochrome P450 enzymes. The key cellular receptors, pregnane X receptor (PXR), constitutive androstane receptor (CAR), vitamin D receptor (VDR), and glucocorticoid receptor (GR) provide a functional cross-talk between the pathways maintaining cholesterol homeostasis and controlling the expression of drug-metabolizing enzymes. These receptors serve as metabolic sensors, resulting in a coordinate regulation of cholesterogenic compounds metabolism and of the defense against xenobiotic and endobiotic toxicity. Herein we present a comprehensive review of functional interactions between cholesterol homeostasis and drug metabolism involving the main nuclear and steroid receptors.

Alterations in cholesterol regulation contribute to the production of intratumoral androgens during progression to castration-resistant prostate cancer in a mouse xenograft model

BACKGROUND

Emerging evidence suggests that androgens and the androgen receptor (AR) are important mediators of castration-resistant prostate cancer (CRPC) progression. Increased expression of several enzymes responsible for cholesterol synthesis and conversion into downstream androgens has been documented in human CRPC tumors in comparison to primary tumors. Based on these observations it is hypothesized that cholesterol and its overall regulation within the cell are altered, thus modifying precursor levels for de novo androgen synthesis within the castrate tumoral environment.

METHODS

Tumoral steroid levels were assessed by LC-MS. Free and esterified cholesterol was quantified by LC-MS and a fluorescent assay. Gene and protein expression were assessed by RT-PCR and immunoblotting.

RESULTS

Herein, using a prostate cancer xenograft mouse model it is demonstrated by Western blot analysis that proteins responsible for cholesterol regulation (LDL-r, SR-B1, HMG-CoA reductase, ACAT1,2, ABCA1) are altered during disease progression to increase influx and synthesis of cholesterol as well as free cholesterol formation from cholesteryl ester stores. In turn this can provide increased amounts of precursor for intratumoral steroidogenesis after castration. Androgens- testosterone and dihydrotestosterone- coincidently increase at CRPC to physiologically relevant levels leading to the induction of AR expression and PSA production. Furthermore, cellular cholesterol homeostasis is maintained by increased cholesterol efflux at CRPC so that excess free cholesterol does not cause toxicity to the tumor cells.

CONCLUSIONS

Cellular cholesterol regulation processes are altered during progression to CRPC. Free cholesterol from increased biosynthesis or uptake is likely a precursor for intratumoral de novo androgen synthesis.

Cholesterol absorption and metabolism

Inhibitors of cholesterol absorption have been sought for decades as a means to treat and prevent cardiovascular diseases associated with hypercholesterolemia. Ezetimibe is the one clear success story in this regard, and other compounds with similar efficacy continue to be sought. In the last decade, the laboratory mouse, with all its genetic power, has become the premier experimental model for discovering the mechanisms underlying cholesterol absorption and has become a critical tool for preclinical testing of potential pharmaceutical entities. This chapter briefly reviews the history of cholesterol absorption research and the various gene candidates that have come under consideration as drug targets. The most common and versatile method of measuring cholesterol absorption is described in detail along with important considerations when interpreting results, and an alternative method is also presented. In recent years, reverse cholesterol transport has become an area of intense new interest for drug discovery since this process is now considered another key to reducing cardiovascular disease risk. The ultimate measure of reverse cholesterol transport is sterol excretion and a detailed description is given for measuring neutral and acidic fecal sterols and interpreting the results.

Cholesterol metabolism and transport in the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder, affecting millions of people worldwide. Apart from age, the major risk factor identified so far for the sporadic form of AD is possession of the epsilon4 allele of apolipoprotein E (APOE), which is also a risk factor for coronary artery disease (CAD). Other apolipoproteins known to play an important role in CAD such as apolipoprotein B are now gaining attention for their role in AD as well. AD and CAD share other risk factors, such as altered cholesterol levels, particularly high levels of low density lipoproteins together with low levels of high density lipoproteins. Statins--drugs that have been used to lower cholesterol levels in CAD, have been shown to protect against AD, although the protective mechanism(s) involved are still under debate. Enzymatic production of the beta amyloid peptide, the peptide thought to play a major role in AD pathogenesis, is affected by membrane cholesterol levels. In addition, polymorphisms in several proteins and enzymes involved in cholesterol and lipoprotein transport and metabolism have been linked to risk of AD. Taken together, these findings provide strong evidence that changes in cholesterol metabolism are intimately involved in AD pathogenic processes. This paper reviews cholesterol metabolism and transport, as well as those aspects of cholesterol metabolism that have been linked with AD.

Activated polyamine catabolism leads to low cholesterol levels by enhancing bile acid synthesis

Transgenic mice with activated polyamine catabolism due to overexpression of spermidine/spermine N(1)-acetyltransferase (SSAT) have significantly reduced plasma total cholesterol levels. In our study, we show that low cholesterol levels were attributable to enhanced bile acid synthesis in combination with reduced cholesterol absorption. Hepatic cholesterol 7alpha-hydroxylase (CYP7A1), the rate-limiting enzyme catalyzing the conversion of cholesterol to bile acids, plays an important role in the removal of excess cholesterol from the body. We suggest that by reducing activity of Akt activated polyamine catabolism increased the stability and activity of peroxisome proliferator-activated receptor gamma co-activator 1alpha, the critical activator of CYP7A1. This is supported by our finding that the treatment with SSAT activator, N (1) ,N(11)-diethylnorspermine, reduced significantly the amount of phosphorylated (active) Akt in HepG2 cells. In summary, activated-polyamine catabolism is a novel mechanism to regulate bile acid synthesis. Therefore, polyamine catabolism could be a potential therapeutic target to control hepatic CYP7A1 expression.

Acyl-coenzyme A:cholesterol acyltransferases

The enzymes acyl-coenzyme A (CoA):cholesterol acyltransferases (ACATs) are membrane-bound proteins that utilize long-chain fatty acyl-CoA and cholesterol as substrates to form cholesteryl esters. In mammals, two isoenzymes, ACAT1 and ACAT2, encoded by two different genes, exist. ACATs play important roles in cellular cholesterol homeostasis in various tissues. This chapter summarizes the current knowledge on ACAT-related research in two areas: 1) ACAT genes and proteins and 2) ACAT enzymes as drug targets for atherosclerosis and for Alzheimer's disease.

Hepatic denervation impairs the assembly and secretion of VLDL-TAG

VLDL secretion is a regulated process that depends on the availability of lipids, apoB and MTP. Our aim was to investigate the effect of liver denervation upon the secretion of VLDL and the expression of proteins involved in this process. Denervation was achieved by applying a 85% phenol solution onto the portal tract, while control animals were treated with 9% NaCl. VLDL secretion was evaluated by the Tyloxapol method. The hepatic concentration of TAG and cholesterol, and the plasma concentration of TAG, cholesterol, VLDL-TAG, VLDL-cholesterol and HDL-cholesterol were measured, as well as mRNA expression of proteins involved in the process of VLDL assembly. Hepatic acinar distribution of MTP and apoB was evaluated by immunohistochemistry. Denervation increased plasma concentration of cholesterol (125.3 +/- 10.1 vs. 67.1 +/- 4.9 mg dL(-1)) and VLDL-cholesterol (61.6 +/- 5.6 vs. 29.4 +/- 3.3 mg dL(-1)), but HDL-cholesterol was unchanged (45.5 +/- 6.1 vs. 36.9 +/- 3.9 mg dL(-1)). Secretion of VLDL-TAG (47.5 +/- 23.8 vs. 148.5 +/- 27.4 mg dL h(-1)) and mRNA expression of CPT I and apoB were reduced (p < 0.01) in the denervated animals. MTP and apoB acinar distribution was not altered in the denervated animals, but the intensity of the reaction was reduced in relation to controls.

Identification of putative active site residues of ACAT enzymes

In this report, we sought to determine the putative active site residues of ACAT enzymes. For experimental purposes, a particular region of the C-terminal end of the ACAT protein was selected as the putative active site domain due to its high degree of sequence conservation from yeast to humans. Because ACAT enzymes have an intrinsic thioesterase activity, we hypothesized that by analogy with the thioesterase domain of fatty acid synthase, the active site of ACAT enzymes may comprise a catalytic triad of ser-his-asp (S-H-D) amino acid residues. Mutagenesis studies revealed that in ACAT1, S456, H460, and D400 were essential for activity. In ACAT2, H438 was required for enzymatic activity. However, mutation of D378 destabilized the enzyme. Surprisingly, we were unable to identify any S mutations of ACAT2 that abolished catalytic activity. Moreover, ACAT2 was insensitive to serine-modifying reagents, whereas ACAT1 was not. Further studies indicated that tyrosine residues may be important for ACAT activity. Mutational analysis showed that the tyrosine residue of the highly conserved FYXDWWN motif was important for ACAT activity. Furthermore, Y518 was necessary for ACAT1 activity, whereas the analogous residue in ACAT2, Y496, was not. The available data suggest that the amino acid requirement for ACAT activity may be different for the two ACAT isozymes.

Separation of cellular nonpolar neutral lipids by normal-phase chromatography and analysis by electrospray ionization mass spectrometry

Neutral lipids are an important class of hydrophobic compounds found in all cells that play critical roles from energy storage to signal transduction. Several distinct structural families make up this class, and within each family there are numbers of individual molecular species. A solvent extraction protocol has been developed to efficiently isolate neutral lipids without complete extraction of more polar phospholipids. Normal-phase HPLC was used for the separation of cholesteryl esters (CEs), monoalkylether diacylglycerols, triacylglycerols, and diacylglycerols in a single HPLC run from this extract. Furthermore, minor lipids such as ubiquinone-9 could be detected in RAW 264.7 cells. Molecular species that make up each neutral lipid class can be analyzed both qualitatively and quantitatively by on-line LC-MS and LC-MS/MS strategies. The quantitation of >20 CE molecular species revealed that challenging RAW 264.7 cells with a Toll-like receptor 4 agonist caused a >20-fold increase in the content of CEs within cells, particularly those CE molecular species that contained saturated (14:0, 16:0, and 18:1) fatty acyl groups. Longer chain CE molecular species did not change in response to the activation of these cells.

Androgen-mediated cholesterol metabolism in LNCaP and PC-3 cell lines is regulated through two different isoforms of acyl-coenzyme A:Cholesterol Acyltransferase (ACAT)

BACKGROUND

The objective of this work was to determine the effect of an androgen agonist, R1881, on intracellular cholesterol synthesis and esterification in androgen-sensitive (AS) prostate cancer (LNCaP) cells.

METHODS

We investigated the activity and expression of cholesterol metabolism enzymes, HMG-CoA-reductase and ACAT in the LNCaP and PC-3 (androgen-independent control) models.

RESULTS

Microsomal PC-3 HMG-CoA-reductase activity was increased with R1881 despite having similar cholesterol levels while increased cholesterol levels in microsomes from LNCaPs treated with R1881 (L+) were associated with increased HMG-CoA reductase activity. Increased intracellular cholesteryl esters (CE) found in (L+) were not associated with an increased ACAT1 activity. There was no effect from androgen treatment on ACAT1 protein expression in theses cells; however, ACAT2 expression was induced upon R1881 treatment. In contrast, we found an increase in the in vitro ACAT1 activity in PC-3 cells treated with androgen (P+). Only ACAT1 expression was induced in P+. We further assessed the expression of STAT1 alpha, a transcriptional activator that modulates ACAT1 expression. STAT1 alpha expression and phosphorylation were induced in P+. To determine the role of the AR on ACAT1 expression and esterification, we treated PC-3 cells overexpressing the androgen receptor with R1881 (PAR+). AR expression was decreased in PAR+ cells; ACAT1 protein expression and cholesterol ester levels were also decreased, however, ACAT2 remained unchanged. STAT1 alpha expression was decreased in PAR+.

CONCLUSIONS

Overall, these findings support the importance of cholesterol metabolism regulation within prostate cancer cells and unravel a novel role for STAT1 alpha in prostate cancer metabolism.