Effects of emodin on lipid accumulation and inflammation in hepatocytes / 中国中药杂志

The aim of this study was to explore the effect of emodin on lipid accumulation and inflammation in hepatocytes. The cell morphology was observed by microscopy. LDH release was detected by the kit. Levels of intracellular lipid droplets were observed by oil red O staining. The contents of TC and TG in cells were detected by the kit. Western blot was used to determine protein expressions of FASN,SREBF2,APOB,IL-6 and p-NF-κB in hepatocytes. The results showed that the levels of L02 cell LDH were significantly increased after being treated with emodin,and the cells showed shrinkage,volume reduction,decrease in quantity with the increase of dose. Red lipid droplets were observed in L02 hepatocytes. Intracellular TC and TG contents of L02 cell increased in a concentrationdependent manner,with significant differences between medium and high-dose groups( P < 0. 05). Protein expressions of FASN,SREBF2,IL-6 and p-NF-κB were significantly higher than those of the control group,and the expression level of APOB was significantly lower than that of the control group( P<0. 05). In conclusion,emodin could induce lipid accumulation and inflammatory damage in hepatocytes in a dose-dependent manner,which in turn could damage liver cells. This process was related to the up-regulation of FASN,SREBF2,IL-6,p-NF-κB,as well as the down-regulation of the protein expression of APOB.

Effects of ingredients of Korean brown rice cookies on attenuation of cholesterol level and oxidative stress in high-fat diet-fed mice

BACKGROUND/OBJECTIVES: Owing to health concerns related to the consumption of traditional snacks high in sugars and fats, much effort has been made to develop functional snacks with low calorie content. In this study, a new recipe for Korean rice cookie, dasik, was developed and its antioxidative, lipid-lowering, and anti-inflammatory effects and related mechanisms were elucidated. The effects were compared with those of traditional rice cake dasik (RCD), the lipid-lowering effect of which is greater than that of traditional western-style cookies. MATERIALS/METHODS: Ginseng-added brown rice dasik (GBRD) was prepared with brown rice flour, fructooligosaccharide, red ginseng extract, and propolis. Mice were grouped (n = 7 per group) into those fed a normal AIN-76 diet, a high-fat diet (HFD), and HFD supplemented with RCD or GBRD. Dasik in the HFD accounted for 7% of the total calories. The lipid, reactive oxygen species, and peroxynitrite levels, and degree of lipid peroxidation in the plasma or liver were determined. The expression levels of proteins involved in lipid metabolism and inflammation, and those of antioxidant enzymes were determined by western blot analysis. RESULTS: The plasma and hepatic total cholesterol concentrations in the GBRD group were significantly decreased via downregulation of sterol regulatory element-binding protein-2 and 3-hydroxy-3-methylglutaryl-CoA reductase (P < 0.05). The hepatic peroxynitrite level was significantly lower, whereas glutathione was higher, in the GBRD group than in the RCD group. Among the antioxidant enzymes, catalase (CAT) and glutathione peroxidase (GPx) were significantly upregulated in the GBRD group (P < 0.05). In addition, nuclear factor-kappaB (NF-κB) expression in the GBRD group was significantly lower than that in the RCD group. CONCLUSIONS: GBRD decreases the plasma and hepatic cholesterol levels by downregulating cholesterol synthesis. This new dasik recipe also improves the antioxidative and anti-inflammatory status in HFD-fed mice via CAT and GPx upregulation and NF-κB downregulation. These effects were significantly higher than those of RCD.

Petroleum ether sub-fraction of rosemary extract improves hyperlipidemia and insulin resistance by inhibiting SREBPs / 中国天然药物

As a culinary and medicinal herb, rosemary is widely used. The present work aimed to investigate the effects of rosemary extracts on metabolic diseases and the underlying mechanisms of action. Liver cells stably expressing SREBP reporter were used to evaluate the inhibitory effects of different fractions of rosemary extracts on SREBP activity. The obese mice induced by Western-type diet were orally administered with rosemary extracts or vehicle for 7 weeks, the plasma and tissue lipids were analyzed. SREBPs and their target genes were measured by quantitative RT-PCR. We demonstrated that the petroleum ether sub-fraction of rosemary extracts (PER) exhibited the best activity in regulating lipid metabolism by inhibiting SREBPs, while water and n-BuOH sub-fraction showed the SREBPs agonist-effect. After PER treatment, there was a significant reduction of total SREBPs in liver cells. PER not only decreased SREBPs nuclear abundance, but also inhibited their activity, resulting in decreased expression of SREBP-1c and SREBP-2 target genes in vitro and in vivo. Inhibiting SREBPs by PER decreased the total triglycerides and cholesterol contents of the liver cells. In the mice fed with Western-type diet, PER treatment decreased TG, TC, ALT, glucose, and insulin in blood, and improved glucose tolerance and insulin sensitivity. Furthermore, PER treatment also decreased lipid contents in liver, brown adipose tissue, and white adipose tissue. Our results from the present study suggested that petroleum ether fraction of rosemary extracts exhibited the best potential of improving lipid metabolism by inhibiting SREBPs activity.

Short- and long-term effects of xuezhikang, an extract of cholestin, on serum proprotein convertase subtilisin/kexin type 9 levels / 中国结合医学杂志

<p><b>OBJECTIVE</b>To investigate the short- and long-term effects of Xuezhikang (XZK), an extract of cholestin, on proprotein convertase subtilisin/kexin type 9 (PCSK9) level.</p><p><b>METHODS</b>Thirty rats were randomly divided into three groups and were given saline, XZK 1,200 mg/kg or lovastatin 10 mg/kg respectively by daily gavage for 3 days (n=10 for each). Sixteen patients without previous lipid-lowering drug treatment for dyslipidemia received XZK 1,200 mg daily for 8 weeks. Fasting blood samples and liver tissue were collected at day 3 for rats, while the blood samples were obtained at baseline and week 8 from patients. The serum PCSK9 and lipid profile were measured. The expression of hepatic low density lipoprotein (LDL) receptor and sterol regulatory element binding protein 2 (SREBP-2) were measured by real time-PCR.</p><p><b>RESULTS</b>PCSK9 levels in rats were significantly increased in the XZK and lovastatin groups (P=0.002, P=0.003 vs. control) at day 3, while no significant differences were found in the levels of lipid parameters. PCSK9 levels in patients increased by 34% (P=0.006 vs. baseline) accompanied by total cholesterol and LDL-cholesterol decreased by 22% and 28% P=0.001, P=0.002 vs. baseline). The hepatic mRNA levels of LDL-receptor and SREBP-2 were significantly increased in the XZK and lovastatin groups.</p><p><b>CONCLUSION</b>XZK has significant impact on PCSK9 in a short- and long-term manner in both rats and humans. Moreover, the data indicated that as lovastatin, XZK increased PCSK9 levels through SREBP-2 pathway.</p>

Effects of SIRT1 gene knock-out via activation of SREBP2 protein-mediated PI3K/AKT signaling on osteoarthritis in mice / 华中科技大学学报（医学）（英德文版）

This study investigated the effects of SIRT1 gene knock-out on osteoarthritis in mice, and the possible roles of SREBP2 protein and the PI3K/AKT signaling pathway in the effects. Mice were randomly divided into a normal group and a SIRT1 gene knock-out group (6 mice in each group). In these groups, one side of the knee anterior cruciate ligament was traversed, and the ipsilateral medial meniscus was cut to establish an osteoarthritis model of knee joint. The countralateral synovial bursa was cut out, serving as controls. The knee joint specimens were then divided into four groups: SIRT1control group (group A, n=6); SIRT1osteoarthritis group (group B, n=6); SIRT1control group (group C, n=6); SIRT1osteoarthritis group (group D, n=6). HE staining, Masson staining, Safranin O-Fast Green staining and Van Gieson staining were used to observe the morphological changes in the articular cartilage of the knee. Immunohistochemical staining was employed to detect the expression of SIRT1, SREBP2, VEGF, AKT, HMGCR and type II collagen proteins. SA-β-gal staining was utilized to evaluate chondrocyte aging. The results showed clear knee joint cartilage destruction and degeneration in the SIRT1osteoarthritis group. The tidal line was twisted and displaced anteriorly. Type II collagen was destroyed and distributed unevenly. Compared with the SIRT1osteoarthritis group and SIRT1control group, SIRT1 protein expression was not obviously changed in the SIRT1osteoarthritis group (P>0.05), while the expression levels of the SREBP2, VEGF and HMGCR proteins were significantly increased (P<0.05) and the levels of AKT and type II collagen proteins were significantly decreased (P<0.05). SIRT1 gene knock-out may aggravate cartilage degeneration in osteoarthritis by activating the SREBP2 protein-mediated PI3K/AKT signalling pathway, suggesting that SIRT1 gene may play a protective role against osteoarthritis.

Effect of high-fat diet on cholesterol metabolism in rats and its association with Na⁺/K⁺-ATPase/Src/pERK signaling pathway / 华中科技大学学报（医学）（英德文版）

Abnormal cholesterol metabolism is associated with an elevated risk of developing atherosclerosis, hypertension, and diabetes etc. Na(+)/K(+)-ATPase was found to regulate cholesterol synthesis, distribution and trafficking. This study aimed to examine the effect of high-fat diet on cholesterol metabolism in rats and the role of Na(+)/K(+)-ATPase/Src/ERK signaling pathway in the process. Forty male SD rats were evenly divided into high-fat diet group and control group at random. Animals in the former group were fed on high-fat diet for 12 weeks, and those fed on basic diet served as control. Blood lipids, including total cholesterol (TC), triglyceride (TG), high density lipoprotein-cholesterol (HDL-C), and low density lipoprotein-cholesteral (LDL-C) levels, were detected at 3, 6 and 12 weeks. The ratio of cholesterol content in cytoplasm to that in cell membrane was detected in liver tissues. RT-PCR and Western blotting were used to measure the expression of lipid metabolism-associated genes (HMG-CoA reductase and SREBP-2) after 12-week high-fat diet. Na(+)/K(+)-ATPase/Src/ERK signaling pathway-related components (Na(+)/K(+)-ATPase α1, Src-PY418 and pERK1/2) were also measured by Western blotting. The results showed that the serum TC, TG, and LDL-C levels were significantly higher in high-fat diet group than those in control group, while the HDL-C level was significantly lower in high-fat diet group at 6 weeks (P<0.01). High-fat diet led to an increase in the cholesterol content in the cytoplasm and cell membrane. The ratio of cholesterol content in cytoplasm to that in cell membrane was elevated over time. The expression of HMG-CoA reductase and SREBP-2 was significantly suppressed at mRNA and protein levels after 12-week high-fat diet (P<0.05). Moreover, high-fat diet promoted the expression of Na(+)/K(+)-ATPase α1 but suppressed the phosphorylation of Src-PY418 and ERK1/2 at 12 weeks (P<0.05). It was concluded that high-fat diet regulates cholesterol metabolism, and Na(+)/K(+)-ATPase signaling pathway is involved in the process possibly by regulating the expression of lipid metabolism-associated proteins HMG-CoA reductase and SREBP-2.

Inhibition of proprotein convertase subtilisin/kexin type 9: a novel mechanism of berberine and 8-hydroxy dihydroberberine against hyperlipidemia / 中国结合医学杂志

<p><b>OBJECTIVE</b>To investigate the effect and molecular mechanisms of different doses of 8-hydroxy dihydroberberine (Hdber) for the treatment of hyperlipidemia in rats.</p><p><b>METHODS</b>A rat model of hyperlipidemia was established by feeding rats a high-fat diet for 4 weeks in 70 rats of 80 animals, and 10 rats were randomly selected as control group. The hyperlipidemic rats were then randomly divided into the following groups: a model group (MOD); a berberine group [BBR, 156 mg/(kg day)]; Hdber groups, which were treated with different doses of Hdber [78, 39 and 19.5 mg/(kg day)]; and a simvastatin group [SIM, 4 mg/(kg day)]. The corresponding therapy was administered to the rats of each treatment via gastric tubes. Normal animals were used as a control group. The blood levels of various lipids, including total cholesterol, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, free fatty acid (FFA), apolipoprotein AI(Apo-AI) and apolipoprotein B (Apo-B) were examined. The protein expressions of low-density lipoprotein receptor (LDL-R), sterol regulatory element-binding protein 2 (SREBP-2), 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) and proprotein convertase subtilisin/kexin type 9 (PCSK-9) in liver tissues were determined by Western blot analysis.</p><p><b>RESULTS</b>Compared with the control group of rats, the model group demonstrated a deteriorated blood lipid profile and exhibited increased expression levels of PCSK-9 protein in their liver tissues (P<0.01). In addition, the high-fat diet decreased the expression levels of LDL-R, SREBP-2 and HMGCR proteins in murine liver tissues. However, the addition of berberine or Hdber reversed the blood lipid profile changes (P<0.05 or P<0.01), decreased the expression levels of PCSK-9 proteins (P<0.01), and increased the expression levels of LDL-R proteins in the hyperlipidemic rats (P<0.01). These compounds did not significantly influence the expression levels of SREBP-2 and HMGCR proteins in the hyperlipidemic rats.</p><p><b>CONCLUSIONS</b>Hdber is effective in the treatment of hyperlipidemia in rats. The therapeutic mechanisms of Hdber may be associated with increasing the expression of LDL-R protein and decreasing the expression of PCSK-9 protein in liver tissues.</p>

Intervention of Huayu Qutan Recipe on liver SREBP-2 signal pathway of hyperlipidemia rats of pi deficiency syndrome / 中国中西医结合杂志

<p><b>OBJECTIVE</b>To explore the intervention of Huayu Qutan Recipe (HQR) on liver SREBP-2 signal pathway of hyperlipidemia rats of Pi deficiency syndrome (PDS).</p><p><b>METHODS</b>Totally 100 SPF grade SD rats were randomly divided into the blank control group, the hyperlipidemia group, the hyperlipidemia treatment group, the PDS hyperlipidemia group, and the PDS hyperlipidemia treatment group, 20 in each group. Common granular forage was fed to rats in the blank control group. High fat forage was fed to rats in the hyperlipidemia group and the hyperlipidemia treatment group. Rats in the PDS hyperlipidemia group and the PDS hyperlipidemia treatment group were treated with excessive labor and improper diet for modeling. They were administered refined lard by gastrogavage (3 mL each time, twice per day) and fed with high fat forage on the odd days, and fed with wild cabbage freely on even days. The modeling lasted for 30 days. Rats in the hyperlipidemia treatment group and PDS hyperlipidemia treatment group were administered with Huayu Qutan Recipe (20 mL/kg) by gastrogavage, once a day, for 30 successive days. Levels of serum cholesterol (TC), triglyceride (TG), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), and serum amylase (AMY) were detected by automatic biochemical analyzer. D-xylose excretion rate was determined using phloroglucinol method. Morphological changes of liver and the lipid deposition in liver were observed using HE stain and oil red O stain respectively, mRNA and protein expression levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), cholesterol 7α-hydroxylase 1 (CYP7A1), LDL-R, and sterol regulatory element binding protein-2 (SREBP-2) were detected using real time RT-PCR and Western blotting.</p><p><b>RESULTS</b>Compared with the blank control group, serum levels of TC (1.84 ± 0.19 mmol/L, 2.23 ± 0.43 mmol/L) and LDL-C (0.99 ± 0.24 mmol/L, 1.13 ± 0.56 mmol/L) were higher in the hyperlipidemia group and the PDS hyperlipidemia group, serum levels of HDL-C (0.41 ± 0.66 mmol/L, 0.41 ± 0.11 mmol/L) and AMY activities (351 ± 45 mmol/L, 153 ± 30 mmol/L) were lower, and urinary D-xylose excretion rates were lower (26.9 ± 2.1 ng/mL, 15.0 ± 1.7 ng/mL) (all P < 0.05). Lipid deposition occurred in liver cells. Much fat vacuoles occurred in the cytoplasm. Expression levels of HMGCR, CYP7A1, LDL-R, and SREBP-2 mRNA and proteins in liver significantly decreased (P < 0.01). Compared with the hyperlipidemia group, serum levels of TC and LDL-C significantly increased (P < 0. 05), AMY activities and urinary D-xylose excre- tion rates significantly decreased in the PDS hyperlipidemia group (P < 0.01). A large amount of lipid deposition occurred in liver. The atrophy of liver cells was obviously seen. Expression levels of CYP7A1, LDL-R, and SREBP-2 mRNA and proteins in liver were significantly lower (P < 0.01, P < 0.05). Serum levels of TC and LDL-C significantly decreased (P < 0.05), AMY activities and urinary D-xylose excretion rates significantly increased in the hyperlipidemia treatment group (P < 0.01). Expression levels of CYP7A1, LDL-R, and SREBP-2 mRNA and proteins in liver were significantly increased (P < 0.01, P < 0.05). Compared with the PDS hyperlipidemia group, serum level of TC significantly decreased (P < 0.05), HDL-C levels, AMY activities and urinary D-xylose excretion rates significantly increased in the PDS hyperlipidemia treatment group (P < 0.01),expression levels of CYP7A1, LDL-R, and SREBP-2 mRNA and proteins in liver were significantly increased (P < 0.01). Similar changes occurred in the two treatment groups.</p><p><b>CONCLUSIONS</b>Pi deficiency exacerbates abnormal serum TC level and the lipid deposition in liver. These might be related to regulating expression levels of LDL-R, HMGCR, and CYP7A1 genes in the SREBP-2 signal pathway. HQR could regulate this pathway to intervene abnormal metabolism of TC.</p>

Changes of intracellular cholesterol metabolism in neuroendocrine differentiation of prostate cancer and their significance / 中华男科学杂志

<p><b>OBJECTIVE</b>To explore the roles of intracellular cholesterol metabolism in neuroendocrine (NE) differentiation of prostate cancer based on an androgen-independent prostate cancer NE cell model induced by androgen deprivation.</p><p><b>METHODS</b>LNCaP cells were cultured in androgen-depleted medium, and NE phenotypes were identified by observing the changes in cell morphology, molecular markers (SgIII, NSE and CgA) and cell proliferation. The expression and distribution of cholesterol and Sg III were determined by immunofluorescence staining. The expressions of the key genes LDL-R, SREBP-1 and SREBP-2 involved in cholesterol synthesis and uptake were detected by semi-quantitative RT-PCR.</p><p><b>RESULTS</b>The LNCaP cells showed shrinking bodies and extending axons after androgen deprivation, and all the molecular markers, such as Sg III, NSE and CgA, significantly increased in a time-dependent manner, while the cell proliferation was obviously inhibited (P < 0.05). The cholesterol distribution in the LNCaP cells after NE differentiation presented remarkable aggregation at the axon terminals. However, there were no significant differences in the expression of cholesterol between the two types of cells, nor in the changes of the expressions of key genes LDL-R, SREBP-1 and SREBP-2 involved in cholesterol synthesis and uptake (P > 0.05).</p><p><b>CONCLUSION</b>Transient androgen depletion could successfully induce NE differentiation of LNCaP cells, and the intracellular cholesterol could re-distribute into axon terminals to enhance the formation of neurosecretory granules.</p>

Effect of RNAi-mediated silencing of SREBP2 gene on inflammatory cytokine-induced cholesterol accumulation in HepG2 cells / 中华肝脏病杂志

<p><b>OBJECTIVE</b>To investigate the effect of RNA interference (RNAi)-mediated silencing of the SREBP2 on inflammatory cytokine-induced cholesterol accumulation in HepG2 cells.</p><p><b>METHODS</b>Short-hairpin (sh)RNA targeting SREBP2 or negative control (NC) shRNA were transfected into HepG2 cells by a liposomal method. G418-selective culturing was used to obtain the SREBP2 shRNA HepG2 and NC shRNA HepG2 cell lines. The two cell lines were cultured in serum-free medium and left untreated (control) or treated with TNF-a (20 ng/ml), low-density lipoprotein (LDL) loading (100 mug/ml), or a combination LDL plus TNF-a treatment. Lipid accumulation was evaluated by oil red O (ORO) staining. Intracellular cholesterol level was measured by enzymatic assay. The mRNA and protein levels of SREBP2 and its downstream target genes, LDL receptor (LDLr), and HMGCoA reductase, were measured by real-time PCR and Western blotting, respectively.</p><p><b>RESULTS</b>SREBP2 shRNA HepG2 and NC shRNA HepG2 stable cell lines were successfully established. ORO staining and cholesterol quantitative analysis showed that LDL loading significantly increased intracellular cholesterol and that expression of SREBP2 further exacerbated the inflammatory cytokine-induced lipid accumulation, as seen in NC shRNA HepG2 cells. LDL loading of NC shRNA HepG2 decreased the gene and protein expressions of SREBP2, LDLr, and HMGCoA reductase, but the suppressive effect was overridden by inflammatory cytokine. SREBP2 shRNA HepG2 cells showed lower levels of cholesterol accumulation under LDL loading and inflammatory stress conditions. Moreover, the mRNA and protein levels of SREBP2, LDLr, and HMGCoA reductase were much lower than in NC shRNA HepG2 cells under the same conditions.</p><p><b>CONCLUSION</b>Inflammatory cytokine exacerbated cholesterol accumulation in HepG2 via disrupting SREBP2. RNAi-mediated inhibition of SREBP2 expression significantly ameliorated the cholesterol accumulation induced by inflammatory cytokine.</p>

Association of sterol regulatory element binding protein 2 and insulin-like growth factor binding protein 3 genetic polymorphisms with avascular necrosis of the femoral head in the Chinese population / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Sterol regulatory element binding protein (SREBP)-2 plays a key role in lipid homeostasis by stimulating gene expression of cholesterol biosynthetic pathways. The insulin-like growth factor binding protein (IGFBP) family regulates growth and metabolism, especially bone cell metabolism, and correlates with osteonecrosis. However, association of their gene polymorphisms with risk of avascular necrosis of the femoral head (ANFH) has rarely been reported. We determined whether SREBP-2 and IGFBP-3 gene polymorphisms were associated with increased ANFH risk in the Chinese population.</p><p><b>METHODS</b>Two single nucleotide polymorphisms of SREBP2 gene, rs2267439 and rs2267443, and one of IGFBP-3 gene, rs2453839, were selected and genotyped in 49 ANFH patients and 42 control individuals by direct sequencing assay.</p><p><b>RESULTS</b>The frequencies of rs2267439 TT and rs2267443 GA of SREBP2 and rs2453839 TT and CT of IGFBP-3 in the ANFH group showed increased and decreased tendencies (against normal control group), respectively. Interaction analysis of genes revealed that the frequency of carrying rs2267439 TT and rs2267443 GA genotypes of SREBF-2 in ANFH patients was significantly higher than in the control group (P < 0.05). Association analysis between polymorphisms and clinical phenotype demonstrated that the disease course in ANFH patients with the rs2453839 TT genotype of IGFBP-3 was significantly shorter than that of CT + CC carriers (P < 0.01). CT + CC genotype frequency in patients with stage III/IV bilateral hip lesions was significantly higher than in those with stage III/IV unilateral lesions and stage II/III bilateral lesions (P < 0.05 - 0.02).</p><p><b>CONCLUSIONS</b>Our results suggested that interaction of SREBP-2 gene polymorphisms and the relationship between the polymorphisms and clinical phenotype of IGFBP-3 were closely related to increased ANFH risk in the Chinese population. The most significant finding was that the CT + CC genotype carriers of IGFBP-3 rs2453839 were highly associated with the development of ANFH.</p>

Progress of Niemann-Pick type C1 Like 1 on cholesterol metabolism / 生理学报

The polytopic transmembrane protein, Niemann-Pick type C1 Like 1 (NPC1L1), is the key point of exogenous cholesterol absorption and plays an important role in cholesterol metabolism. However, the molecular mechanism of NPC1L1's role in cholesterol uptake remains unclear. NPC1L1 expression is highly regulated by a variety of molecular actors. Nuclear receptors regulate NPC1L1 expression through its promoter region. Polyunsaturated fatty acids down-regulates NPC1L1 expression by the way of sterol regulatory element binding protein 2 (SREBP2). In addition, curcumin and sphingosine-phosphate take part in the regulation of NPC1L1 expression. NPC1L1 has been recognized as an essential protein for sterol absorption and is the molecular target of ezetimibe. Moreover, inhibition of the expression of NPC1L1 has been shown to have beneficial effects on components of the metabolic syndrome. The recent progress in the structure, function and regulation of NPC1L1 is reviewed.

Inflammation enhances the accumulation of lipid in ApoE/SRA/CD36 KO mice liver / 中华肝脏病杂志

<p><b>OBJECTIVE</b>To investigate if inflammatory stress enhances liver lipid accumulation via SREBPs mediated dysregulation of low density protein receptor (LDLr) expression in apolipoprotein E, scavenger receptors class A and CD36 triple knockout (ApoE/SRA/CD36 KO) mice.</p><p><b>METHODS</b>16 Male ApoE/SRA/CD36 KO mice were subcutaneously injected with 0.5 ml 10% casein or PBS. The mice were fed a Western diet (Harlan, TD88137) containing 21% fat and 0.15% of cholesterol for 14 weeks. Animals were sacrificed and blood samples were collected. The serum amyloid A (SAA), IL-6, total cholesterol (TC), LDL and high density protein (HDL) were assayed. The lipid accumulation in liver was evaluated by Oil Red O staining. The mRNA and protein expression of SREBP-2, SREBPs cleavage activating protein (SCAP) and LDLr were analyzed by Real-Time Polymerase Chain Reaction (RT-PCR) and immunohistochemistry staining.</p><p><b>RESULTS</b>Blood levels of SAA [(26.60+/-3.24) ng/ml vs (14.35+/-1.73) ng/ml, P < 0.01] and IL-6 [(36.37+/-2.20) pg/ml vs (18.02+/-4.87) pg/ml, P < 0.01] were higher, while TC [(7.72+/-1.70) mmol/L vs (13.23+/-3.61)mmol/L, P less than 0.01], LDL-cholesterol [(2.94+/-0.44) mmol/L vs (9.28+/-3.66) mmol/L, P less than 0.01] and HDL cholesterol [(2.24+/-0.63) mmol/L vs (4.13+/-0.42) mmol/L, P less than 0.01] were lower in inflamed mice compared to controls. ORO staining showed that lipid accumulation in the liver was more extensive in inflamed group despite lower blood lipid levels. Meanwhile, Real Time PCR data showed inflammation induced the expression of LDLr (4.56 fold), SCAP (3.14 fold) and SREBP-2 (14.72 fold) in liver. Immunohistochemical staining also indicated increased proteins expression in the liver, which was consistent with mRNA data.</p><p><b>CONCLUSIONS</b>Inflammation causes lipid accumulation in liver via disrupting SREBP-2 and LDLr expression.</p>

Oxidized low-density lipoprotein enhances the expressions of SREBP-2 and HMGCR mRNA in macrophages derived from the monocytes of patients with acute coronary syndrome / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of oxidized low-density lipoprotein (ox-LDL) on the expressions of sterol regulatory element binding protein-2 (SREBP-2) and hydroxymethylglutaryl CoA reductase (HMGCR) in the macrophages derived from monocytes of patients with acute coronary syndrome (ACS).</p><p><b>METHODS</b>LDL was oxidized by Cu2+ to prepare ox-LDL, and peripheral monocytes were isolated by density gradient centrifugation from patients with ACS diagnosed by coronary arteriography. Macrophages derived from the monocytes after phorbol myristate acetate (PMA) stimulation were treated with ox-LDL at the concentrations of 0, 20, 40, and 100 ng/ml, and the changes in the expressions of SREBP-2 and HMGCR were detected by real-time RT-PCR.</p><p><b>RESULTS</b>Compared with the control cells, the macrophages treated with ox-LDL showed significantly increased expressions of SREBP-2 and HMGCR mRNA (P<0.05). In cells treated with ox-LDL, the expressions of SREBP-2 and HMGCR mRNA differed significantly with the dose administered (P<0.05).</p><p><b>CONCLUSION</b>Within a defined dose range, ox-LDL can dose-dependently enhance the expressions of SREBP-2 and HMGCR mRNA in macrophages from patients with ACS.</p>

Red yeast rice increases excretion of bile acids in hamsters / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To investigate the hypocholesterolemic activity of red yeast rice (RYR) and its underlying mechanism.</p><p><b>METHODS</b>Three groups of hamsters were fed either the control diet or one of the two experimental diets containing by weight 0.1% RYR (0.1RYR) or 0.3% RYR (0.3RYR). Blood (0.5 mL) was collected from the retro-orbital sinus into a heparinized capillary tube at the end of week 0, 3, and 6. Plasma lipoproteins were measured using enzymatic kits, while fecal neutral and acidic sterols were quantified using a gas-liquid chromatography.</p><p><b>RESULTS</b>Plasma total cholesterol was reduced by 12% in 0.1RYR group and by 18% in 0.3RYR group compared with the control value. Similarly, plasma triacylglycerol was decreased by 11% in 0.1RYR group and by 24% in 0.3RYR group. Western blotting analysis demonstrated that RYR had no effect on sterol regulatory element binding protein 2, liver X receptor, 3-hydroxy-3-methylglutary-CoA reductase, LDL receptor, and cholesterol-7alpha-hydroxylase. HPLC analysis confirmed that RYR contained 0.88% monacolin K. It was recently found that RYR supplementation increased excretion of fecal acidic sterols by 3-4 folds compared with the control value.</p><p><b>CONCLUSION</b>Hypocholesterolemic activity of RYR is mediated at least partially by enhancement of acidic sterol excretion.</p>

Sterol-independent repression of low density lipoprotein receptor promoter by peroxisome proliferator activated receptor gamma coactivator-1alpha (PGC-1alpha)

Peroxisome proliferator activated receptor (PPAR) gamma coactivator-1alpha (PGC-1alpha) may be implicated in cholesterol metabolism since PGC-1alpha co-activates estrogen receptor alpha (ERalpha) transactivity and estrogen/ERalpha induces the transcription of LDL receptor (LDLR). Here, we show that overexpression of PGC-1alpha in HepG2 cells represses the gene expression of LDLR and does not affect the ERalpha-induced LDLR expression. PGC-1alpha suppressed the LDLR promoter-luciferase (pLR1563-luc) activity regardless of cholesterol or functional sterol-regulatory element-1. Serial deletions of the LDLR promoter revealed that the inhibition by PGC-1alpha required the LDLR promoter regions between -650 bp and -974 bp. Phosphorylation of PGC-1alpha may not affect the suppression of LDLR expression because treatment of SB202190, a p38 MAP kinase inhibitor, did not reverse the LDLR down-regulation by PGC-1alpha. This may be the first report showing the repressive function of PGC-1alpha on gene expression. PGC-1alpha might be a novel modulator of LDLR gene expression in a sterol-independent manner, and implicated in atherogenesis.

Mechanisms of dysregulation of low-density lipoprotein receptor expression in HepG2 cells induced by inflammatory cytokines / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Low-density lipoprotein (LDL) receptor is normally regulated via a feedback system that is dependent on intracellular cholesterol levels. We have demonstrated that cytokines disrupt cholesterol-mediated LDL receptor feedback regulation causing intracellular accumulation of unmodified LDL in peripheral cells. Liver is the central organ for lipid homeostasis. The aim of this study was to investigate the regulation of cholesterol exogenous uptake via LDL receptor and its underlying mechanisms in human hepatic cell line (HepG2) cells under physiological and inflammatory conditions.</p><p><b>METHODS</b>Intracellular total cholesterol (TC), free cholesterol (FC) and cholesterol ester (CE) were measured by an enzymic assay. Oil Red O staining was used to visualize lipid droplet accumulation in cells. Total cellular RNA was isolated from cells for detecting LDL receptor, sterol regulatory element binding protein (SREBP)-2 and SREBP cleavage-activating protein (SCAP) mRNA levels using real-time quantitative PCR. LDL receptor and SREBP-2 protein expression were examined by Western blotting. Confocal microscopy was used to investigate the translocation of SCAP-SREBP complex from the endoplasmic reticulum (ER) to the Golgi by dual staining with anti-human SCAP and anti-Golgin antibodies.</p><p><b>RESULTS</b>LDL loading increased intracellular cholesterol level, thereby reduced LDL receptor mRNA and protein expression in HepG2 cells under physiological conditions. However, interleukin 1 beta (IL-1 beta) further increased intracellular cholesterol level in the presence of LDL by increasing both LDL receptor mRNA and protein expression in HepG2. LDL also reduced the SREBP and SCAP mRNA level under physiological conditions. Exposure to IL-1 beta caused over-expression of SREBP-2 and also disrupted normal distribution of SCAP-SREBP complex in HepG2 by enhancing translocation of SCAP-SREBP from the ER to the Golgi despite a high concentration of LDL in the culture medium.</p><p><b>CONCLUSIONS</b>IL-1 beta disrupts cholesterol-mediated LDL receptor feedback regulation by enhancing SCAP-SREBP complex translocation from the ER to the Golgi, thereby increasing SREBP-2 mediated LDL receptor expression even in the presence of high concentration of LDL. This results in LDL cholesterol accumulation in hepatic cells via LDL receptor pathway under inflammatory stress.</p>