OBJECTIVETo 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.

METHODSLNCaP 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.

RESULTSThe 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).

CONCLUSIONTransient 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.

Androgens ; pharmacology ; Cell Differentiation ; Cell Line, Tumor ; Cell Proliferation ; Cholesterol ; metabolism ; Humans ; Male ; Neurosecretory Systems ; metabolism ; Prostatic Neoplasms ; metabolism ; pathology ; Receptors, LDL ; metabolism ; Sterol Regulatory Element Binding Protein 1 ; metabolism ; Sterol Regulatory Element Binding Protein 2 ; metabolism

OBJECTIVETo investigate the effect of RNA interference (RNAi)-mediated silencing of the SREBP2 on inflammatory cytokine-induced cholesterol accumulation in HepG2 cells.

METHODSShort-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.

RESULTSSREBP2 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.

CONCLUSIONInflammatory cytokine exacerbated cholesterol accumulation in HepG2 via disrupting SREBP2. RNAi-mediated inhibition of SREBP2 expression significantly ameliorated the cholesterol accumulation induced by inflammatory cytokine.

Cholesterol ; metabolism ; Hep G2 Cells ; Humans ; Inflammation ; RNA Interference ; RNA, Small Interfering ; Sterol Regulatory Element Binding Protein 2 ; genetics ; Tumor Necrosis Factor-alpha ; pharmacology

OBJECTIVETo 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.

METHODS16 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.

RESULTSBlood 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.

CONCLUSIONSInflammation causes lipid accumulation in liver via disrupting SREBP-2 and LDLr expression.

Animals ; Apolipoproteins E ; genetics ; Cholesterol, LDL ; metabolism ; Fatty Liver ; metabolism ; Inflammation ; metabolism ; Liver ; metabolism ; Male ; Mice ; Mice, Knockout ; Receptors, LDL ; metabolism ; Sterol Regulatory Element Binding Protein 2 ; metabolism

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.
Azetidines ; pharmacology ; Biological Transport ; Cholesterol ; metabolism ; Ezetimibe ; Fatty Acids ; metabolism ; Humans ; Membrane Proteins ; metabolism ; Metabolic Syndrome ; physiopathology ; Receptors, Cytoplasmic and Nuclear ; metabolism ; Sterol Regulatory Element Binding Protein 2 ; metabolism

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.
Alkanes ; chemistry ; Animals ; Cholesterol ; metabolism ; Hepatocytes ; drug effects ; metabolism ; Humans ; Hyperlipidemias ; drug therapy ; genetics ; metabolism ; Insulin ; metabolism ; Insulin Resistance ; Liver ; drug effects ; metabolism ; Male ; Mice ; Mice, Inbred C57BL ; Petroleum ; analysis ; Plant Extracts ; administration & dosage ; chemistry ; isolation & purification ; Rosmarinus ; chemistry ; Sterol Regulatory Element Binding Protein 1 ; genetics ; metabolism ; Sterol Regulatory Element Binding Protein 2 ; genetics ; metabolism

BACKGROUNDSterol 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.

METHODSTwo 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.

RESULTSThe 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).

CONCLUSIONSOur 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.

Adult ; Asian Continental Ancestry Group ; genetics ; Female ; Femur Head Necrosis ; genetics ; Genetic Predisposition to Disease ; Humans ; Insulin-Like Growth Factor Binding Protein 3 ; genetics ; Male ; Middle Aged ; Polymerase Chain Reaction ; Polymorphism, Genetic ; genetics ; Sterol Regulatory Element Binding Protein 2 ; genetics

OBJECTIVETo investigate the short- and long-term effects of Xuezhikang (XZK), an extract of cholestin, on proprotein convertase subtilisin/kexin type 9 (PCSK9) level.

METHODSThirty 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.

RESULTSPCSK9 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.

CONCLUSIONXZK 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.

Animals ; Biological Products ; chemistry ; Drugs, Chinese Herbal ; pharmacology ; Female ; Humans ; Lipids ; blood ; Male ; Middle Aged ; Proprotein Convertase 9 ; blood ; Rats, Sprague-Dawley ; Receptors, LDL ; genetics ; metabolism ; Sterol Regulatory Element Binding Protein 2 ; genetics ; metabolism ; Time Factors

OBJECTIVETo investigate the effects of hypoxia on lipid metabolism in the normal human hepatic cell line L02 and to investigate the underlying molecular mechanisms.

METHODSL02 cells were exposed to hypoxic conditions (experimental groups: at 1% O2, 5% CO2, 94% N2 for 3, 6, 12, 24, or 48 hours) or normoxic conditions (control group: at 21% O2). Lipid droplet accumulation and triglyceride content were measured in each group by oil red O staining and biochemical assay, respectively. The mRNA expression levels of hypoxia-inducible factor (HIF)-2a and sterol regulatory element binding protein (SREBP)-1c were detected by reverse transcription-polymerase chain reaction. Protein expression levels of HIF-2a, adipose differentiation-related protein (ADRP), and Fas were tested by Western blot analysis.

RESULTSLipid droplet accumulation and the triglyceride content were significantly higher in the hypoxia group than the normoxia group. In addition, the hypoxia groups had significantly down-regulated mRNA expression of SREBP-1c (12h: 0.236+/-0.043, 24 h: 0.287+/-0.044, 48 h: 0.342+/-0.049 vs. normoxia: 0.503+/-0.037; F = 28.37, P less than 0.01) and FAS protein (12 h: 0.562+/-0.054, 24 h: 0.674+/-0.062, 48 h: 0.682+/-0.057 vs normoxia: 0.857+/-0.069; F = 16.08, P less than 0.01). In normoxic cells, little or no expression of HIF-2a protein was detected by Western blot. In hypoxic cells, HIF-2a protein expression peaked at 6h (0.973+/-0.067). ADRP protein expression was significantly higher in hypoxia groups than in the normoxia group (12 h: 0.319+/-0.043, 24 h: 0.732+/-0.056 and 48 h: 0.873+/-0.066 vs. 0.211+/-0.019; all, P less than 0.05.

CONCLUSIONExposure to hypoxic conditions might induce lipidosis in normal human hepatic cells by stimulating HIF-2a and ADRP expression.

Basic Helix-Loop-Helix Transcription Factors ; metabolism ; Cell Hypoxia ; Cell Line ; Down-Regulation ; Hepatocytes ; metabolism ; Humans ; Lipid Metabolism ; Membrane Proteins ; metabolism ; Oxygen ; metabolism ; Perilipin-2 ; Sterol Regulatory Element Binding Protein 1 ; metabolism

OBJECTIVETo 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).

METHODSLDL 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.

RESULTSCompared 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).

CONCLUSIONWithin a defined dose range, ox-LDL can dose-dependently enhance the expressions of SREBP-2 and HMGCR mRNA in macrophages from patients with ACS.

Acute Coronary Syndrome ; blood ; Dose-Response Relationship, Drug ; Humans ; Hydroxymethylglutaryl CoA Reductases ; genetics ; metabolism ; Lipoproteins, LDL ; pharmacology ; Macrophages ; metabolism ; RNA, Messenger ; genetics ; metabolism ; Sterol Regulatory Element Binding Protein 2 ; genetics ; metabolism

OBJECTIVETo explore the intervention of Huayu Qutan Recipe (HQR) on liver SREBP-2 signal pathway of hyperlipidemia rats of Pi deficiency syndrome (PDS).

METHODSTotally 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.

RESULTSCompared 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.

CONCLUSIONSPi 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.

Animals ; Cholesterol, HDL ; Cholesterol, LDL ; Drugs, Chinese Herbal ; therapeutic use ; Hyperlipidemias ; drug therapy ; Liver ; Male ; Medicine, Chinese Traditional ; RNA, Messenger ; Rats ; Rats, Sprague-Dawley ; Signal Transduction ; Sterol Regulatory Element Binding Protein 2 ; metabolism ; Triglycerides