• Journal of Microbiology and Biotechnology
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• v.34 no.2
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• pp.425-435
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• 2024

Schisandra chinensis extract (SCE) protects against hypocholesterolemia by inhibiting proprotein convertase subtilisin/kexin 9 (PCSK9) protein stabilization. We hypothesized that the hypocholesterolemic activity of SCE can be attributable to upregulation of the PCSK9 inhibition-associated low-density lipoprotein receptor (LDLR). Male mice were fed a low-fat diet or a Western diet (WD) containing SCE at 1% for 12 weeks. WD increased final body weight and blood LDL cholesterol levels as well as alanine transaminase and aspartate aminotransferase expression. However, SCE supplementation significantly attenuated the increase in blood markers caused by WD. SCE also attenuated WD-mediated increases in hepatic LDLR protein expression in the obese mice. In addition, SCE increased LDLR protein expression and attenuated cellular PCSK9 levels in HepG2 cells supplemented with delipidated serum (DLPS). Non-toxic concentrations of schisandrin A (SA), one of the active components of SCE, significantly increased LDLR expression and tended to decrease PCSK9 protein levels in DLPS-treated HepG2 cells. High levels of SA-mediated PCSK9 attenuation was not attributable to reduced PCSK9 gene expression, but was associated with free PCSK9 protein degradation in this cell model. Our findings show that PCSK9 secretion can be significantly reduced by SA treatment, contributing to reductions in free cholesterol levels.

• Journal of Microbiology and Biotechnology
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• v.32 no.11
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• pp.1406-1415
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• 2022

The formation of macrophage foam cells stimulated by oxidized low-density lipoprotein (ox-LDL) is deemed an important cause of atherosclerosis. Transcription factor Yin Yang 1 (YY1), which is a universally expressed multifunctional protein, is closely related to cell metabolism disorders such as lipid metabolism, sugar metabolism, and bile acid metabolism. However, whether YY1 is involved in macrophage inflammation and lipid accumulation still remains unknown. After mouse macrophage cell line RAW264.7 cells were induced by ox-LDL, YY1 and proprotein convertase subtilisin/kexin type 9 (PCSK9) expressions were found to be increased while low-density lipoprotein receptor (LDLR) expression was lowly expressed. Subsequently, through reverse transcription-quantitative polymerase chain reaction (RT-qPCR), Western blot analysis, Oil Red O staining and cholesterol quantification, it turned out that silencing of YY1 attenuated the inflammatory response and lipid accumulation in RAW264.7 cells caused by ox-LDL. Moreover, results from the JASPAR database, chromatin immunoprecipitation (ChIP) assay, luciferase reporter assay and Western blot analysis suggested that YY1 activated PCSK9 by binding to PCSK9 promoter and modulated the expression of LDLR in the downstream of PCSK9. In addition, the results of functional experiments demonstrated that the inhibitory effects of YY1 interference on ox-LDL-mediated macrophage inflammation and lipid accumulation were reversed by PCSK9 overexpression. To sum up, YY1 depletion inhibited its activation of PCSK9, thereby reducing cellular inflammatory response, cholesterol homeostasis imbalance, and lipid accumulation caused by ox-LDL.

• Journal of Food Hygiene and Safety
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• v.31 no.2
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• pp.113-118
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• 2016

Proprotein convertase subtilisin/kexin type 9 (PCSK9), is a protein mainly secreted by a liver. The PCSK9 plays an important role in low density lipoprotein (LDL) metabolism acting as a repressor of LDL receptor through transportation of the LDLR to the lysosome for degradation. Thus, the PCSK9 inhibitor suppresses PCSK9-regulated degradation of the LDL receptor as a LDL-lowering medicine. However, little is known about the role of PCSK9 in the reproductive system. Therefore, in the present study, we investigated Pcsk9 expression in male reproductive tracts including penises, prostates and testes using rats in response to their diets between a normal diet and a high-fat diet with cholesterol. Based on our previous study, the high-fat diet elevates concentration of total cholesterol and LDL in serum whereas it reduces the concentration of plasma high density lipoprotein (HDL). In addition, it dramatically affects to morphological changes of the male reproductive organs. Consistent with these results, the expression of Pcsk9 was substantially decreased in the penile tissues (P < 0.001) from rats fed a high fat diet as compared to a normal diet. Moreover, it slightly reduced in the prostate and testes (P < 0.05) of rats in response to a high fat diet. Localization of Pcsk9 was predominantly detected in urethral epithelium of penises, cylinder-shaped cells of prostate glands, and spermatogonia, spermatocytes and spermatid of testes of rats. Collectively, results of current study provide invaluable insights into the Pcsk9 gene with respect to its tissue- and cell-specific expression by a high fat diet with cholesterol.

• The Korea Journal of Herbology
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• v.35 no.4
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• pp.45-50
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• 2020

Objective : This study was performed to evaluate the toxicity after a single oral administration of black raspberry extract to male and female Sprague-Dawley (SD) rats and to determine the approximate lethal dose (ALD). Methods : We previously showed that the black raspberry extract repressed the simvastatin-mediated expression of Proprotein convertase subtilisin/kexin type 9 (PCSK9) and improved Low-Density Lipoprotein cholesterol (LDL-C) uptake by hepatocytes through the induction of the Low-Density Lipoprotein Receptor expression in hepatocytes. The groups consisted of black raspberry extract groups, as an oral dose of 2,000 mg/kg and a control group. 5 weeks SD rats were randomly assigned to 4 groups of 5 rats. Each male and female SD rats were administered orally once. For 14 days after the administration, mortality, clinical signs, changes in body weight, and necropsy findings were observed according to the "Standard for Toxicity Study of Pharmaceuticals" of Korea Food and Drug Administration (KFDA) guideline and "Acute Oral Toxicity- Fixed Dose Procedure" of OECD Test Guideline. Results : There were no cases of mortality in the group administered with 2,000 mg/kg of male and female, and no abnormalities in body weight change and clinical signs. Also, no gross abnormalities were observed at the autopsy. Conclusions : As a result of a single oral administration of the black raspberry extract to SD rats, the ALD was determined to exceed 2,000 mg/kg for both male and female SD rats.

• Journal of Lipid and Atherosclerosis
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• v.7 no.2
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• pp.77-87
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• 2018

Lowering serum low-density lipoprotein cholesterol (LDL-C) is the mainstay for reduction of risk of cardiovascular disease (CVD), the second most common cause of death in Korea. The 2015 Korean guidelines for management of dyslipidemia strongly recommend the use of statins in patients at risk of CVD. Statin therapy, which is the gold standard for CVD, reduces LDL-C level by 40% to 60% and is generally well tolerated. However, many patients are intolerant to statins and discontinue therapy or become nonadherent to therapy because of actual/perceived side effects. The most common of these side effects is the statin-associated muscle symptom (SAMS). Discontinuation and repetitive re-challenge with statins can help identify SAMS. If serum creatinine kinase level is more than 10 times the upper limit of normal, statin therapy must be stopped immediately, and the physician should identify possible causes including rhabdomyolysis and treat appropriately. In other patients, it might help to switch to a less potent statin or to use statins at intermittent non-daily dosing. To achieve target LDL-C level, non-statin lipid-lowering therapies such as dietary modifications, ezetimibe, and bile acid sequestrants may be added. Several new drugs have recently been approved for lowering LDL-C level. Alirocumab and evolocumab are monoclonal antibodies that inhibit proprotein convertase subtilisin/kexin type 9, and both drugs cause large reductions in LDL-C, similar to statins. Lomitapide and mipomersen are orphan drugs used as adjuncts to other lipid-lowering therapies in patients with homozygous familial hypercholesterolemia.

• Korean Journal of Food Science and Technology
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• v.51 no.3
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• pp.272-277
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• 2019

The effects of medium-chain enriched diacylglycerol (MCE-DAG) oil on hepatic cholesterol homeostasis were investigated. HepG2 hepatocytes were treated with either 0.5, 1.0, or $1.5{\mu}g/mL$ of MCE-DAG for 48 h. There was no evidence of cytotoxicity by MCE-DAG up to $1.5{\mu}g/mL$. The level of proteins for cholesterol uptake including CLATHRIN and LDL receptor increased by MCE-DAG in a dose-dependent manner (p<0.05). Furthermore, proprotein convertase subtilisin/kexin type 9, an inhibitor of LDLR, was dose-dependently diminished (p<0.05), indicating cholesterol clearance raised. MCE-DAG significantly increased 3-hydroxy-3-methylglutaryl-coenzyme A reductase and acetyl-CoA acetyltransferase2 (p<0.05), required for cholesterol synthesis, and their transcriptional regulator sterol regulatory element-binding protein2 (p<0.05). These findings suggest that given conditions of prolonged sterol fasting in the current study activated both hepatic cholesterol synthesis and clearance by MCE-DAG. However, total intracellular level of cholesterol was not altered by MCE-DAG. Taken together, MCE-DAG has the potential to prevent hypercholesterolemia by increasing hepatic cholesterol uptake without affecting intracellular cholesterol level.

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.11
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• pp.1278-1285
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• 2017

Accumulation of excess low density lipoprotein (LDL) cholesterol in the blood can initiate and accelerate atherosclerosis. Statins mediate the transactivation of proprotein convertase subtilisin/kexin type 9 (PCSK9), which in turn limits their cholesterol-lowering effects via LDL receptor (LDLR) degradation. The objective of this study was to investigate whether or not Allium tuberosum (AT) regulates LDLR and PCSK9. Mice were fed a low fat control diet (LD) or Western diet (WD) supplemented with AT (1%, w/w). AT significantly attenuated total and LDL cholesterol levels in mice fed WD (P<0.05). AT also significantly inhibited hepatic PCSK9 gene expression (P<0.05) while AT maintained hepatic LDLR gene expression. To further investigate AT-mediated PCSK9 regulation, HepG2 cells were treated with 10% delipidated serum (DLPS) in the presence or absence of AT. Non-toxic level of AT dose-dependently increased the LDLR protein level, and AT at $400{\mu}g/mL$ markedly inhibited PCSK9 protein expression. Similarly, AT significantly increased LDLR gene expression, whereas it significantly down-regulated PCSK9 gene expression. AT-mediated reduction of PCSK9 gene expression is likely due to decreased hepatic nuclear factor $1{\alpha}$ ($HNF1{\alpha}$) expression, but not SREBP2 in HepG2 cells under lipid-depleted conditions. AT-mediated PCSK9 inhibition contributed to LDLR protein stabilization via protection against LDLR lysosomal degradation in HepG2 cells under lipid-depleted conditions. Further investigation is warranted to determine the active components of AT and whether or not these components are effective in reducing hypercholesterolemia.

• Journal of Nutrition and Health
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• v.51 no.4
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• pp.275-286
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• 2018

Purpose: Our previous study demonstrated that persimmon (Diospyros kaki Thumb.) at different stages of ripening provided different protective effects against high-fat/cholesterol diet (HFD)-induced dyslipidemia in rats. In this study, we compared the metabolites profile and gene expressions related to triglyceride (TG)/cholesterol metabolism in vitro and in vivo after treating with persimmon water extracts (PWE) or tannin-enriched persimmon concentrate (TEP). Methods: Primary and secondary metabolites in test materials were determined by GC-TOF/MS, UHPLC-LTQ-ESI-IT-MS/MS, and UPLC-Q-TOF-MS. The expression of genes related to TG and cholesterol metabolism were determined by RT-PCR both in HepG2 cells stimulated by oleic acid/palmitic acid and in liver tissues obtained from Wistar rats fed with HFD and PWE at 0, 150, 300, and 600 mg/d (experiment I) or TEP at 0, 7, 14, and 28 mg/d (experiment II) by oral gavage for 9 weeks. Results: PLS-DA analysis and heatmap analysis demonstrated significantly differential profiling of metabolites of PWE and TEP according to processing of persimmon powder. In vitro, TEP showed similar hypolipidemic effects as PWE, but significantly enhanced hypocholesterolemic effects compared to PWE in sterol regulatory element-binding protein 2 (SREBP2), HMG-CoA reductase (HMGCR), proprotein convertase subtilisin/kexin type 9 (PCSK9), cholesterol $7{\alpha}-hydroxylase$ (CYP7A1), and low density lipoprotein receptor (LDLR) gene expression. Consistently, TEP and PWE showed similar hypolipidemic capacity in vivo, but significantly enhanced hypocholesterolemic capacity in terms of SREBP2, HMGCR, and bile salt export pump (BSEP) gene expression. Conclusion: These results suggest that column extraction after hot water extraction may be a good strategy to enhance tannins and long-chain fatty acid amides, which might cause stimulation of hypocholesterolemic actions through downregulation of cholesterol biosynthesis gene expression and upregulation of LDL receptor gene expression.