Inhibition Of Cholesterol Synthesis Research Articles

Oleanolic acid inhibits cholesterol synthesis by suppressing the expression and enzymatic activity of HMGCR

ABSTRACT This study investigated the impact of Oleanolic Acid (OA) on cholesterol metabolism and. MTT assays demonstrated that OA had no cytotoxic effects on HepG2 cells at concentrations below 20 μM. Subsequent experiments focused on 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCR), a key enzyme in cholesterol biosynthesis. OA significantly reduced HMGCR protein expression without affecting other enzymes. Further investigations revealed that OA reduced the protein and mRNA expression of HMGCR and its upstream regulator Sterol regulatory element binding protein-2 (SREBP-2) in HepG2 cells. OA activated Adenosine 5’-monophosphate (AMP)-activated protein kinase (AMPK), enhancing HMGCR phosphorylation and inhibiting its activity. Molecular docking experiments suggested that OA could suppress HMGCR enzymatic activity through hydrophobic interactions, reducing catalytic efficiency. Overall, OA downregulated HMGCR expression and activity, leading to decreased cholesterol synthesis. These findings highlight OA’s regulatory role in cholesterol metabolism and its potential for improving atherosclerosis (AS), supporting its application in functional food development.

Post-surgery statin use contributes to favorable outcomes in patients with early breast cancer

BackgroundStatins are a group of lipid-lowering drugs with pleiotropic effects that include, but are not limited to the inhibition of cholesterol synthesis resulting in a wide range of anti-inflammatory, anti-tumor, immunomodulatory, and anti-thrombotic properties. This study aimed to determine the impact of the prior to- or after- breast surgery usage of statins on the tumor prognosis in breast cancer (BC) patients. MethodsA cohort of patients diagnosed with early invasive ductal BC (n=301) at the Hospital Italiano de Buenos Aires, Argentina, with a minimum follow-up period of 10 years after the surgical procedure were included and stratified according to the time of use of statins and type of statin used. Then, local relapse-free survival (RFS), metastasis-free survival (MFS), bone metastasis-free survival (BMFS), visceral metastasis-free (VMFS), mixed metastasis (bone and visceral)-free survival (mix-MFS) and overall survival (OS) were analyzed. ResultsStatins usage after breast surgery was related with lesser metastatic occurrence (p=0.017), lower number of metastatic foci (p=0.034) and fewer dead events (p=0.041), as well as longer MFS (p=0.013) and OS (p=0.027). When stratified by the nature of statins (hydrophilic or lipophilic), only the relatively hydrophilic statin rosuvastatin (ROSU) had an impact on the increase of MFS and OS (p=0.018 and p=0.030, respectively). ConclusionPost-surgery statins usage was associated with increased MFS and OS, with increased benefits of ROSU over simvastatin (SIM) or atorvastatin (ATOR). These results set the rationale for additional studies addressing the use of statins, and particularly, rosuvastatin, to improve the outcome of BC patients.

The Molecular Mechanism of circRNA-11228/miR-103/INSIG1 Pathway Regulating Milk Fat Synthesis in Bovine Mammary Epithelial Cells

Milk, known for its high content of short- and medium-chain fatty acids and unsaturated fatty acids, has attracted substantial attention due to its nutritional and health value. The regulation of fatty acid metabolism by non-coding RNAs has become a subject of growing attention, particularly in relation to fatty acid production at the transcriptional/epigenetic and post-transcriptional levels. This study established the circRNA-11228/miR-103/INSIG1 (insulin-inducible gene) regulatory network using methods such as qRT-PCR, dual luciferase reporting, and Western blot, with INSIG1 serving as the starting point. The experimental validation of circRNA-11228’s impact on cholesterol levels, lipid droplet secretion, and unsaturated fatty acid content was conducted using various assays, including triglycerides, cholesterol, oil red O, andEdU(5-ethynyl-2’-deoxyuridine) in bovine mammary epithelial cells (BMECs). Furthermore, the transfection of mimics and inhibitors synthesized from miR-103 into BMECs confirmed that miR-103 can promote cholesterol synthesis and lipid droplet secretion. Conversely, the INSIG1 gene was found to inhibit cholesterol synthesis and lipid droplet secretion. The “remediation” experiment validated the ability of miR-103 to alleviate the cellular effect of circRNA-11228. Taken together, our findings indicate that the binding of circRNA-11228 to miR-103 inhibits the expression of the target gene INSIG, thereby regulating milk fat production in BMECs. This study offers novel insights into producing high-quality milk and new ways to improve the dietary composition of residents.

Abstract 1095: Prox1 transcription factor and its downstream signaling - A new therapeutic target for rhabdomyosarcoma

Abstract Rhabdomyosarcoma (RMS) stands as the predominant soft tissue sarcoma in children, characterized by a high-grade neoplasm composed of cells resembling skeletal myoblasts. Despite being prevalent, patients with metastatic or recurrent rhabdomyosarcoma still experience poor outcomes, underscoring the necessity for novel treatments. We have recently shown that PROX1 is a critical factor in RMS tumor growth and myogenic characteristics (Gizaw NY, et al. PNAS 2022). As PROX1 has previously been associated with tumor metabolism in colorectal cancer, we investigated further its role in RMS metabolism. Our findings demonstrate that PROX1 plays a crucial role in regulating RMS cell metabolism. Specifically, silencing of PROX1 resulted in decreased lipid and oxidative metabolism, which was accompanied by an increase in glycolysis and triglyceride accumulation. RNA sequencing and Gene Set Enrichment Analysis revealed downregulation of all genes involved in the cholesterol synthesis pathway in PROX1-silenced RMS cells. Our studies further reveal that inhibiting cholesterol synthesis, akin to PROX1 silencing, can effectively inhibit RMS cell growth. Our results provide novel insights into the role of PROX1 in RMS metabolism and highlight the potential of PROX1-regulated metabolic pathways as promising targets for the development of novel RMS therapies. Citation Format: Nebeyu Y. Gizaw, Tom Böhling, Mika Sampo, Kari Alitalo, Riikka M. Kivela. Prox1 transcription factor and its downstream signaling - A new therapeutic target for rhabdomyosarcoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1095.

Identification of a mechanism promoting mitochondrial sterol accumulation during myocardial ischemia-reperfusion: role of TSPO and STAR.

Hypercholesterolemia is a major risk factor for coronary artery diseases and cardiac ischemic events. Cholesterol per se could also have negative effects on the myocardium, independently from hypercholesterolemia. Previously, we reported that myocardial ischemia-reperfusion induces a deleterious build-up of mitochondrial cholesterol and oxysterols, which is potentiated by hypercholesterolemia and prevented by translocator protein (TSPO) ligands. Here, we studied the mechanism by which sterols accumulate in cardiac mitochondria and promote mitochondrial dysfunction. We performed myocardial ischemia-reperfusion in rats to evaluate mitochondrial function, TSPO, and steroidogenic acute regulatory protein (STAR) levels and the related mitochondrial concentrations of sterols. Rats were treated with the cholesterol synthesis inhibitor pravastatin or the TSPO ligand 4'-chlorodiazepam. We used Tspo deleted rats, which were phenotypically characterized. Inhibition of cholesterol synthesis reduced mitochondrial sterol accumulation and protected mitochondria during myocardial ischemia-reperfusion. We found that cardiac mitochondrial sterol accumulation is the consequence of enhanced influx of cholesterol and not of the inhibition of its mitochondrial metabolism during ischemia-reperfusion. Mitochondrial cholesterol accumulation at reperfusion was related to an increase in mitochondrial STAR but not to changes in TSPO levels. 4'-Chlorodiazepam inhibited this mechanism and prevented mitochondrial sterol accumulation and mitochondrial ischemia-reperfusion injury, underlying the close cooperation between STAR and TSPO. Conversely, Tspo deletion, which did not alter cardiac phenotype, abolished the effects of 4'-chlorodiazepam. This study reveals a novel mitochondrial interaction between TSPO and STAR to promote cholesterol and deleterious sterol mitochondrial accumulation during myocardial ischemia-reperfusion. This interaction regulates mitochondrial homeostasis and plays a key role during mitochondrial injury.

Arenobufagin modulation of PCSK9-mediated cholesterol metabolism induces tumor-associated macrophages polarisation to inhibit hepatocellular carcinoma progression

BackgroundThe tumor microenvironment (TME) of hepatocellular carcinoma is heterogeneous enough to be prone to drug resistance and multidrug resistance during treatment, and reprogramming of cholesterol metabolism in TME mediates tumor-associated macrophages (TAMs) polarization, which has an impact on the regulation of malignant tumor progression. Arenobufagin (ARBU) was extracted and isolated from toad venom (purity ≥98 %), which is the main active ingredient of the traditional Chinese medicine Chan'su with good anti-tumor effects. PurposeTo investigate the regulatory effect of ARBU on lipid metabolism in tumor microenvironment, interfere with macrophage polarization, and determine its mechanism of action on liver cancer progression. MethodsIn this study, the inhibitory effect of ARBU on the proliferation of Hepa1–6 in C57 mice and the safety of administration were evaluated by establishing a transplanted tumor model of Hepa1–6 hepatocellular carcinoma mice and using 5-FU as a positive control drug. In addition, we constructed a co-culture system of Hepa1–6 cells and primary mouse macrophages to study the effects of ARBU on the polarization phenotypic transformation of macrophages and the proliferation and migration of hepatoma cells. The influence of ARBU on the metabolism of lipids in the hepatocellular carcinoma mouse model was investigated by combining it with lipidomics technology. The influence of ARBU on the PCSK9/LDL-R signaling pathway and macrophage polarization, which regulate cholesterol metabolism, was tested by using qRT-PCR, gene editing, IF, and WB. ConclusionARBU significantly inhibited the proliferation of Hepa1–6 in vivo and in vitro, regulated cholesterol metabolism, and promoted the M1-type polarization of macrophages in the tumor microenvironment. ARBU inhibits cholesterol synthesis in the TME through the PCSK9/LDL-R signaling pathway, thereby blocking macrophage M2 polarization, promoting apoptosis of the tumor cells, and inhibiting their proliferation and migration.

Alendronate modulates cytokine responses in healthy young individuals after BCG vaccination

Bacillus Calmette–Guérin (BCG) vaccination induces memory characteristics in innate immune cells and their progenitors, a process called trained immunity mediated by epigenetic and metabolic reprogramming. Cholesterol synthesis plays an amplifying role in trained immunity through mevalonate release. Nitrogen-containing bisphosphonates (N-BPs), such as alendronate, can inhibit cholesterol synthesis. We explored their effects on trained immunity induced by BCG in a placebo-controlled clinical study (NL74082.091.20) in young, healthy individuals. Participants receiving single-dose oral alendronate on the day of BCG vaccination had more neutrophils and plasma cells one month after treatment. Alendronate led to reduced proinflammatory cytokine production by PBMCs stimulated with heterologous bacterial and viral stimuli one month later. Furthermore, the addition of alendronate transcriptionally suppressed multiple immune response pathways in PBMCs upon stimulation. Our findings indicate that N-BPs modulate the long-lasting effects of BCG vaccination on the cytokine production capacity of innate immune cells.

A gut-derived hormone regulates cholesterol metabolism

The reciprocal coordination between cholesterol absorption in the intestine and de novo cholesterol synthesis in the liver is essential for maintaining cholesterol homeostasis, yet the mechanisms governing the opposing regulation of these processes remain poorly understood. Here, we identify a hormone, Cholesin, which is capable of inhibiting cholesterol synthesis in the liver, leading to a reduction in circulating cholesterol levels. Cholesin is encoded by a gene with a previously unknown function (C7orf50 in humans; 3110082I17Rik in mice). It is secreted from the intestine in response to cholesterol absorption and binds to GPR146, an orphan G-protein-coupled receptor, exerting antagonistic downstream effects by inhibiting PKA signaling and thereby suppressing SREBP2-controlled cholesterol synthesis in the liver. Therefore, our results demonstrate that the Cholesin-GPR146 axis mediates the inhibitory effect of intestinal cholesterol absorption on hepatic cholesterol synthesis. This discovered hormone, Cholesin, holds promise as an effective agent in combating hypercholesterolemia and atherosclerosis.

Statins affect human iPSC-derived cardiomyocytes by interfering with mitochondrial function and intracellular acidification.

Statins are effective drugs in reducing cardiovascular morbidity and mortality by inhibiting cholesterol synthesis. These effects are primarily beneficial for the patient's vascular system. A significant number of statin users suffer from muscle complaints probably due to mitochondrial dysfunction, a mechanism that has recently been elucidated. This has raised our interest in exploring the effects of statins on cardiac muscle cells in an era where the elderly and patients with poorer functioning hearts and less metabolic spare capacity start dominating our patient population. Here, we investigated the effects of statins on human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-derived CMs). hiPSC-derived CMs were exposed to simvastatin, atorvastatin, rosuvastatin, and cerivastatin at increasing concentrations. Metabolic assays and fluorescent microscopy were employed to evaluate cellular viability, metabolic capacity, respiration, intracellular acidity, and mitochondrial membrane potential and morphology. Over a concentration range of 0.3-100µM, simvastatin lactone and atorvastatin acid showed a significant reduction in cellular viability by 42-64%. Simvastatin lactone was the most potent inhibitor of basal and maximal respiration by 56% and 73%, respectively, whereas simvastatin acid and cerivastatin acid only reduced maximal respiration by 50% and 42%, respectively. Simvastatin acid and lactone and atorvastatin acid significantly decreased mitochondrial membrane potential by 20%, 6% and 3%, respectively. The more hydrophilic atorvastatin acid did not seem to affect cardiomyocyte metabolism. This calls for further research on the translatability to the clinical setting, in which a more conscientious approach to statin prescribing might be considered, especially regarding the current shift in population toward older patients with poor cardiac function.

A molecular docking study on inhibition of HMG CoA reductase with respect to phytochemicals of Terminalia cuneata Roth.

Inhibition of cholesterol synthesis by targeting the enzyme hydroxyl methyl glutarate coenzyme reductase (HMGCR), a rate-limiting enzyme in the mevalonate pathway, has been identified as a promising approach. The most commonly employed drugs for the treatment of hyperlipidemia, statins, have been identified with some risk factors for muscle-related side effects. In this present study, an attempt is made to inhibit the HMG-CoA reductase enzyme using phytochemicals of Terminalia cuneata by in silico approach. The software AutoDock 4.2 was used for the docking study. We used atorvastatin and lovastatin as positive control. We also found the drug likeliness and bioactivity score of all inhibitors using the mol-inspiration prediction tool. We found that most of the compounds showed the best binding energy results against the targeted enzyme.

Can Rosuvastatin Reduce the Risk of Thrombosis in Patients with Hypercholesterolemia with its Effect on Coagulation Factors and Homocysteine Levels?

Hypercholesterolemia is one of the main risk factors for vascular thrombosis in individuals. Therefore, the use of statins is very effective in reducing cholesterol and can reduce the risk of thrombosis in these patients. Rosuvastatin, a member of the statin family which, inhibits cholesterol synthesis. Very few studies have been done in relation to how rosuvastatin can affect thrombosis. So, this research has been tried whether rosuvastatin can have an effect on coagulation factors and homocysteine as risk factors for thrombosis in hypercholesterolemia? In this experimental study, 60 patients (30 men and 30 women with a mean age of 40- 70 years) diagnosed with hypercholesterolemia (cholesterol >250 mg/dl) participated in this research. 30 patients were prescribed rosuvastatin (20 mg/day), and 30 patients were simultaneously taken placebo for three months. All parameters, including FVIII, FV, Fibrinogen, D-Dimer, plasma homocysteine level and lipid profile, were measured before and after treatment. All the results were statistically compared between the two groups. In patients who took rosuvastatin, the drug was able to significantly reduce the concentrations of total cholesterol, triglycerides, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) (P <0.001). Also, rosuvastatin was able to reduce the concentrations of homocysteine significantly, D-Dimer (P <0.001), coagulation factor VIII and factor V (P <0.05). In patients with hypercholesterolemia who took the placebo, did not affect the mentioned variables (P >0.05). According to the results, it seems that rosuvastatin may be able to reduce the risk of thrombosis in patients by affecting coagulation factors and homocysteine levels.

Therapeutic potential of Simvastatin and Doxycycline combination for Alzheimer’s disease

Alzheimer’s disease (AD) is a progressive neurodegenerative brain disorder resulting from Amyloid β (Aβ) accumulation. It leads to a decrease in memory and an increase in the production of reactive oxygen species and reactive nitrogen species and also increases Tubulin-associated unit phosphorylation. During AD, the cholesterol levels in the brain increase, and these regions are called lipid rafts. These lipid rafts are hosts for β and γ secretases. As a result, mono fibrils develop, which leads to Aβ oligomerization and, eventually, Aβ accumulation. Hence, the present study was designed to evaluate the protective effect of Simvastatin (cholesterol synthesis inhibitor) and Doxycycline (anti-amyloidogenic drug) for Aβ clearance in an Aβ-induced AD model, in female C57BL/6 mice. The mice were evaluated for spatial memory and olfactory sensation using the Morris water maze and Buried pellet test, respectively. The group treated with the combination of Simvastatin and Doxycycline at two different concentrations showed a recovery of memory and olfactory sensation when compared to the control group. The results have shown that the high-dose combination of Simvastatin and Doxycycline exhibits cholesterol lowering property by blocking the 3-hydroxy-3-methylglutaryl coenzyme A reductase pathway, thereby regulating cholesterol, and eventually resulting in anti-Alzheimer’s activity.

N6-methyladenosine-modified circular RNA family with sequence similarity 126, member A affects cholesterol synthesis and malignant progression of prostate cancer cells by targeting microRNA-505-3p to mediate calnexin.

Prostate cancer (PCa) is the most commonly diagnosed malignancy in men. In tumor biology, n6-methyladenosine (m6A) can mediate the production of circular RNAs (circRNAs). This study focused on the mechanism of m6A-modified circRNA family with sequence similarity 126, member A (FAM126A) in PCa. Cell counting kit-8 assay, colony formation assay, 5-ethynyl-2'-deoxyuridine assay, transwell assay, and xenograft mouse models were applied to study the role of circFAM126A in PCa cell growth and tumor metastasis, and cellular triglyceride and cholesterol levels were measured to assess cholesterol synthesis. RNA immunoprecipitation, RNA pull-down, luciferase reporter gene assay, and western blot were adopted to explore the underlying molecular mechanism. Data showed that circFAM126A was upregulated in PCa and promoted PCa progression in vitro. m6A modification of circFAM126A enhanced transcriptional stability. CircFAM126A targeted microRNA (miR)-505-3p to mediate calnexin (CANX). Up-regulating miR-505-3p or inhibiting CANX suppressed cholesterol synthesis and malignant progression in PCa cells. Overexpressing CANX suppressed the inhibitory effect of circFAM126A silencing or miR-505-3p upregulation on PCa cells. Our current findings provide a new therapeutic strategy for the treatment of PCa.

Abnormal Cholesterol Metabolism and Lysosomal Dysfunction Induce Age-Related Hearing Loss by Inhibiting mTORC1-TFEB-Dependent Autophagy.

Cholesterol is a risk factor for age-related hearing loss (ARHL). However, the effect of cholesterol on the organ of Corti during the onset of ARHL is unclear. We established a mouse model for the ARHL group (24 months, n = 12) and a young group (6 months, n = 12). Auditory thresholds were measured in both groups using auditory brainstem response (ABR) at frequencies of 8, 16, and 32 kHz. Subsequently, mice were sacrificed and subjected to histological analyses, including transmission electron microscopy (TEM), H&E, Sudan Black B (SBB), and Filipin staining, as well as biochemical assays such as IHC, enzymatic analysis, and immunoblotting. Additionally, mRNA extracted from both young and aged cochlea underwent RNA sequencing. To identify the mechanism, in vitro studies utilizing HEI-OC1 cells were also performed. RNA sequencing showed a positive correlation with increased expression of genes related to metabolic diseases, cholesterol homeostasis, and target of rapamycin complex 1 (mTORC1) signaling in the ARHL group as compared to the younger group. In addition, ARHL tissues exhibited increased cholesterol and lipofuscin aggregates in the organ of Corti, lateral walls, and spiral ganglion neurons. Autophagic flux was inhibited by the accumulation of damaged lysosomes and autolysosomes. Subsequently, we observed a decrease in the level of transcription factor EB (TFEB) protein, which regulates lysosomal biosynthesis and autophagy, together with increased mTORC1 activity in ARHL tissues. These changes in TFEB and mTORC1 expression were observed in a cholesterol-dependent manner. Treatment of ARHL mice with atorvastatin, a cholesterol synthesis inhibitor, delayed hearing loss by reducing the cholesterol level and maintaining lysosomal function and autophagy by inhibiting mTORC1 and activating TFEB. The above findings were confirmed using stress-induced premature senescent House Ear Institute organ of Corti 1 (HEI-OC1) cells. The findings implicate cholesterol in the pathogenesis of ARHL. We propose that atorvastatin could prevent ARHL by maintaining lysosomal function and autophagy by inhibiting mTORC1 and activating TFEB during the aging process.

Cinobufacini injection delays hepatocellular carcinoma progression by regulating lipid metabolism via SREBP1 signaling pathway and affecting macrophage polarization

Ethnopharmacological relevanceCinobufacini injection, an aqueous extract of the toad, is a commonly used anti-tumor animal herbal medicine in clinical practice. It has the effects of detoxifying, reducing swelling, and relieving pain. Aims of the studyTo investigate the effects of Cinobufacini injection on hepatocellular carcinoma progression by regulating lipid metabolism and macrophage polarization in the tumor microenvironment and to identify the potential molecular mechanisms. Materials and methodsTo establish the axillary transplantation tumor model of hepatocellular carcinoma Hepa1-6 in C57BL/6 mice, and to evaluate the inhibitory effect of Cinobufacini injection on hepatocellular carcinoma in vivo as well as drug delivery security. Combined metabolomics and transcriptomics analysis of the effect of Cinobufagin Injection on tumor microenvironment. An in vitro mouse co-culture model of peritoneal macrophages and Hepa1-6 cells was established to research the effects of Cinobufacini injection on macrophage polarization, hepatocellular carcinoma cell growth, migration, and changes in lipid metabolism. Cinobufacini injection inhibition of the AMPK/SREBP1/FASN signaling pathway regulating cholesterol metabolism and affecting macrophage polarization was examined using qRT-PCR, lentiviral transfection, immunofluorescence, and Western blot. ResultIn vivo experiments demonstrated that Cinobufacini injection treatment significantly inhibited the growth of Hepa1-6 hepatomas, along with a reduction in cholesterol content and a decrease in the percentage of M2 macrophages in tumor tissue. In vitro, we found that Cinobufacini injection inhibits IL-4-induced M2 macrophage polarization, reduces the cholesterol content of Hepa1-6 cells in a co-culture system, and inhibits the promotion of hepatocellular carcinoma cells by M2 macrophages. In addition, successful overexpression of SREBP1 in Hepa1-6 cells showed more pronounced cellular activity whereas Cinobufacini injection inhibited this change and reduced intracellular lipid levels. ConclusionCinobufacini injection inhibits cholesterol synthesis within the tumor microenvironment via the AMPK/SERBP1/FASN signaling pathway, which in turn blocks the M2 polarization of macrophages, leading to the weakening of hepatocellular carcinoma growth and migration, and the promotion of its apoptosis. Our findings provide an important Introduction to understanding the molecular mechanism of Cinobufacini injection's anticancer activity and provide reliable theoretical and experimental support for its clinical application.

MicroRNA-206-3p suppresses hepatic lipogenesis and cholesterol synthesis while driving cholesterol efflux.

Hepatosteatosis, hypertriglyceridemia, and hypertriglyceridemia are interconnected metabolic disorders. This study is designed to characterize how microRNA-206-3p (miR-206) simultaneously prevents de novo lipogenesis (DNL), cholesterol synthesis, and VLDL production in hepatocytes while promoting cholesterol efflux in macrophages. MiR-206 levels were reduced in hepatocytes and macrophages of mice subjected to a high-fat, high-cholesterol diet (HFHC). A negative feedback between LXRα (liver X receptor) and miR-206 is formed to maintain high LXRα and low miR-206 in hepatocytes. Systemic administration of miR-206 alleviated hepatosteatosis, hypertriglyceridemia and hypercholesterolemia in mice. A significant reduction in LDL-cholesterol and VLDL-cholesterol but unaltered HDL-cholesterol was observed in miR-206-treated mice. Mirroring these findings, miR-206 reprogrammed the transcriptome of hepatocytes towards inhibition of DNL, cholesterol synthesis, and assembly and secretion of VLDL. In macrophages, miR-206 activated expression of genes regulating cholesterol efflux. Hepatocyte-specific expression of miR-206 reduced hepatic and circulating triglycerides and cholesterol as well as VLDL production, while transplantation of macrophages bearing miR-206 facilitated cholesterol efflux. Mechanistically, miR-206 directly targeted Lxrα and Hmgcr in hepatocytes but facilitated expression of Lxrα in macrophages by targeting macrophage-specific TRPS1 (tricho-rhino-phalangeal syndrome 1), a transcription repressor of Lxrα. By targeting Hmgcr and Lxrα, miR-206 inhibited DNL, VLDL production and cholesterol synthesis in hepatocytes, whereas it drove cholesterol efflux by activating the TRPS1-LXRα axis. MiR-206, through differentially modulating LXRα signaling in hepatocytes and macrophages, inhibits DNL, promotes cholesterol efflux, and concurrently hinders cholesterol synthesis and VLDL production. MiR-206 simulates the functions of lipid-lowering medications, statins and LXRα agonists.

Macrophage AMPK β1 activation by PF-06409577 reduces the inflammatory response, cholesterol synthesis, and atherosclerosis in mice

Atherosclerotic cardiovascular disease is characterized by both chronic low-grade inflammation and dyslipidemia. The AMP-activated protein kinase (AMPK) inhibits cholesterol synthesis and dampens inflammation but whether pharmacological activation reduces atherosclerosis is equivocal. In the current study, we found that the orally bioavailable and highly selective activator of AMPKβ1 complexes, PF-06409577, reduced atherosclerosis in two mouse models in a myeloid-derived AMPKβ1 dependent manner, suggesting a critical role for macrophages. In bone marrow-derived macrophages (BMDMs), PF-06409577 dose dependently activated AMPK as indicated by increased phosphorylation of downstream substrates ULK1 and acetyl-CoA carboxylase (ACC), which are important for autophagy and fatty acid oxidation/de novo lipogenesis, respectively. Treatment of BMDMs with PF-06409577 suppressed fatty acid and cholesterol synthesis and transcripts related to the inflammatory response while increasing transcripts important for autophagy through AMPKβ1. These data indicate that pharmacologically targeting macrophage AMPKβ1 may be a promising strategy for reducing atherosclerosis.

Pineal Gland Hormone Melatonin Inhibits Migration of Hematopoietic Stem/Progenitor Cells (HSPCs) by Downregulating Nlrp3 Inflammasome and Upregulating Heme Oxygenase-1 (HO-1) Activity.

Hematopoietic stem progenitor cells (HSPCs) follow the diurnal circulation rhythm in peripheral blood (PB) with nadir during late night and peak at early morning hours. The level of these cells in PB correlates with activation of innate immunity pathways, including complement cascade (ComC) that drives activation of Nlrp3 inflammasome. To support this, mice both in defective ComC activation as well as Nlrp3 inflammasome do not show typical changes in the diurnal level of circulating HSPCs. Migration of HSPCs is also impaired at the intracellular level by the anti-inflammatory enzyme heme oxygenase-1 (HO-1) which is an inhibitor of Nlrp3 inflammasome. It is also well known that circadian rhythm mediates PB level of melatonin released from the pineal gland. Since trafficking of HSPCs is driven by innate immunity-induced sterile inflammation and melatonin has an anti-inflammatory effect, we hypothesized that melatonin could negatively impact the release of HSPCs from BM into PB by inhibiting Nlrp3 inflammasome activation. We provide anevidence that melatonin being a ''sleep regulating pineal hormone'' directly inhibits migration of HSPCs both in vitro migration assays and in vivo during pharmacological mobilization. This correlated with inhibition of cholesterol synthesis required for a proper membrane lipid raft (MLRs) formation and an increase in expression of HO-1-an inhibitor of Nlrp3 inflammasome. Since melatonin is a commonly used drug, this should be considered while preparing a patient for the procedure of HSPCs mobilization. More importantly, our studies shed more mechanistic light on a role of melatonin in the diurnal circulation of HSPCs.

Cholesterol biogenesis is a PTEN-dependent actionable node for the treatment of endocrine therapy-refractory cancers.

PTEN and PIK3CA mutations are the most prevalent PI3K pathway alterations in prostate, breast, colorectal, and endometrial cancers. p110β becomes the prominent PI3K isoform upon PTEN loss. In this study, we aimed to understand the molecular mechanisms of PI3K dependence in the absence of PTEN. Using online bioinformatical tools, we examined two publicly available microarray datasets with aberrant PI3K activation. We found that the rate-limiting enzyme of cholesterol biogenesis, SQLE, was significantly upregulated in p110β-hyperactivated or PTEN-deficient mouse prostate tumors. Concomitantly, the expression of cholesterol biosynthesis pathway enzymes was directly correlated with PI3K activation status in microarray datasets and diminished upon PTEN re-expression in PTEN-null prostate cancer cells. Particularly, PTEN re-expression decreased SQLE protein levels in PTEN-deficient prostate cancer cells. We performed targeted metabolomics and detected reduced levels of cholesteryl esters as well as free cholesterol upon PTEN re-expression. Notably, PTEN-null prostate and breast cancer cell lines were more sensitive to pharmacological intervention with the cholesterol pathway than PTEN-replete cancer cells. Since steroid hormones use sterols as structural precursors, we studied whether cholesterol biosynthesis may be a metabolic vulnerability that enhances antihormone therapy in PTEN-null castration-resistant prostate cancer cells. Coinhibition of cholesterol biosynthesis and the androgen receptor enhanced their sensitivity. Moreover, PTEN suppression in endocrine therapy-resistant luminal-A breast cancer cells leads to an increase in SQLE expression and a corresponding sensitization to the inhibition of cholesterol synthesis. According to our data, targeting cholesterol biosynthesis in combination with the hormone receptor signaling axis can potentially treat hormone-resistant prostate and breast cancers.

BDE-209-induced genotoxicity, intestinal damage and intestinal microbiota dysbiosis in zebrafish (Danio Rerio)

The environmental presence of polybrominated diphenyl ethers (PBDEs) is ubiquitous due to their wide use as brominated flame retardants in industrial products. As a common congener of PBDEs, decabromodiphenyl ether (BDE-209) can pose a health risk to animals as well as humans. However, to date, few studies have explored BDE-209's toxic effects on the intestinal tract, and its relevant mechanism of toxicity has not been elucidated. In this study, adult male zebrafish were exposed to BDE-209 at 6 μg/L, 60 μg/L and 600 μg/L for 28 days, and intestinal tissue and microbial samples were collected for analysis to reveal the underlying toxic mechanisms. Transcriptome sequencing results demonstrated a dose-dependent pattern of substantial gene differential expression in the group exposed to BDE-209, and the differentially expressed genes were mainly concentrated in pathways related to protein synthesis and processing, redox reaction, and steroid and lipid metabolism. In addition, BDE-209 exposure caused damage to intestinal structure and barrier function, and promoted intestinal oxidative stress, inflammatory response, apoptosis and steroid and lipid metabolism disorders. Mechanistically, BDE-209 induced intestinal inflammation by increasing the levels of TNF-α and IL-1β and activating the NFκB signaling pathway, and might induce apoptosis through the p53-Bax/Bcl2-Caspase3 pathway. BDE-209 also significantly inhibited the gene expression of rate-limiting enzymes such as Sqle and 3βhsd (p < 0.05) to inhibit cholesterol synthesis. In addition, BDE-209 induced lipid metabolism disorders through the mTOR/PPARγ/RXRα pathway. 16S rRNA sequencing results showed that BDE-209 stress reduced the richness and diversity of intestinal microbiota, and reduced the abundance of probiotics (e.g., Bifidobacterium and Faecalibacterium). Overall, the results of this study help to clarify the intestinal response mechanism of BDE-209 exposure, and provide a basis for evaluating the health risks of BDE-209 in animals.