LDLR mRNA Expression Research Articles

493 RESULTS OF LIVER RETRANSPLANTATION IN A MONOCENTRIC COHORT OF HCV INFECTED PATIENTS

quartile of LDLR mRNA expression in the PI biopsy survived with a significantly (Log-Rank test P < 0.05) better survival than those in the three lowest quartiles. Surviving graft (n = 34, median followup 44.8 months, range 8.6–72.3) had significantly higher LDLR (P < 0.01) and NPC1L1 (P < 0.05) mRNA expression in the PI biopsy and HMGCR (P < 0.05) mRNA expression in the PR biopsy than lost grafts (n = 13, median follow-up 6.0 months, range 0.03–43.7). Conclusions: In the settings of human liver transplantation: 1. hepatic LDLR mRNA is overexpressed immediately after graft reperfusion, suggesting an increased hepatocyte cholesterol uptake from blood; 2. hepatic upregulation of genes involved in cholesterol recruitment and synthesis is inversely related to the severity of IRI and is associated with better graft survival.

495 ARE LIVER TRANSPLANT HIV-1 INFECTED PATIENTS AT RISK TO DEVELOP HIV-1 DRUG RESISTANCE?

quartile of LDLR mRNA expression in the PI biopsy survived with a significantly (Log-Rank test P < 0.05) better survival than those in the three lowest quartiles. Surviving graft (n = 34, median followup 44.8 months, range 8.6–72.3) had significantly higher LDLR (P < 0.01) and NPC1L1 (P < 0.05) mRNA expression in the PI biopsy and HMGCR (P < 0.05) mRNA expression in the PR biopsy than lost grafts (n = 13, median follow-up 6.0 months, range 0.03–43.7). Conclusions: In the settings of human liver transplantation: 1. hepatic LDLR mRNA is overexpressed immediately after graft reperfusion, suggesting an increased hepatocyte cholesterol uptake from blood; 2. hepatic upregulation of genes involved in cholesterol recruitment and synthesis is inversely related to the severity of IRI and is associated with better graft survival.

Polysaccharide from fuzi (FPS) prevents hypercholesterolemia in rats.

Background and aimPolysaccharide from fuzi (FPS), a Chinese herbal medicine extract, has been demonstrated to exert lipid lowering affects. In this study we examined potential mechanisms underlying this affect, specifically alterations in expression of the LDL-receptor (LDL-R), 3-hydroxy-3-methyl glutaryl (HMG)-CoA reductase and cytochrome P450 7α-1 (CYP7α-1), using a rat model of hypercholesterolemia.Methods and resultsMale rats were fed either a normal or high cholesterol (HC) diet for two-weeks. Half of the rats on the HC diet were orally gavaged with FPS (224 mg/kg, 448 mg/kg or 896 mg/kg diet) daily. Serum lipid levels were quantified at end of the study period as were liver levels of LDL-R protein and mRNA expression of CYP7α-1 and HMG-CoA. Serum cholesterol and LDL-C concentrations were significantly elevated from control in HC rats, but not in those treated with FPS (P < 0.05). LDL-R expression was significantly decreased in the HC group compared to control (P < 0.05), but significantly increased in the FPS group (P < 0.05). HMG-CoA mRNA levels were significantly increased in the HC group compared both other groups (P < 0.05), while CYP7α-1 expression was significantly higher in the FPS group compared to both other groups (P < 0.05).ConclusionThese findings suggest that the cholesterol lowering effect of FPS in hypercholesteremic rats is caused at least in part by increased hepatic LDL-R and CYP7α-1 expression and decreased HMG-CoA expression. Further study is needed to determine precisely where and how FPS exerts these effects. FPS offers potential as a therapeutic agent for the treatment of hypercholesterolemia.

Developmental programming of lipid metabolism and aortic vascular function in C57BL/6 mice: a novel study suggesting an involvement of LDL-receptor

We have previously shown that a maternal high-fat diet, rich in saturated fatty acids (SFA), alters the lipid metabolism of their adult offspring. The present study was designed to investigate 1) whether alterations in hepatic LDL-receptor (LDL-r) expression may serve as a potential mechanism of developmental programming behind the altered lipid metabolism of the offspring, 2) whether altered lipid metabolism leads to aortic vascular dysfunction in the offspring, 3) whether deleterious effects of SFA exposure preweaning are influenced by postweaning diet, and 4) whether gender-specific programming effects are observed. Female C57Bl/6 mice were fed a high-SFA diet or regular chow during gestation and lactation while their pups, both male and female, received either SFA or a chow diet after weaning. Male offspring obtained from mothers fed an SFA diet and those who continued on chow postweaning had higher plasma triglycerides and total cholesterol, whereas female offspring had higher plasma total and LDL cholesterol levels, lower hepatic LDL-r mRNA expression, and reduced aortic contractile responses compared with the offspring that were fed chow throughout the study. A comparison of the postweaning diet revealed significantly lower hepatic LDL-r expression along with significantly higher plasma LDL-cholesterol concentration in the female offspring that were obtained from mothers fed an SFA diet and who continued on an SFA diet postweaning, compared with the female offspring that were obtained from mothers fed an SFA diet but who continued on chow postweaning. In conclusion, we report a novel observation of hepatic LDL-r-mediated programming of altered lipid metabolism, along with aortic vascular dysfunction, in the female offspring of mothers fed a high-SFA diet. Male offspring only exhibited dyslipidemia, suggesting gender-mediated programming. This study further highlighted the role of postweaning diets in overriding the effects of maternal programming.

Characterization and Expression of the Putative Ovarian Lipoprotein Receptor in the Kuruma Prawn, Marsupenaeus japonicus

Ovarian low density lipoproteins (LDL) such as vitellogenin (Vg) are the precursors of the major yolk protein vitellin, and constitute the major source of nutrients serving the developing embryo. The objective of this study was to gain a better understanding of crustacean egg development by focusing on the process of Vg internalization by its receptor (ovarian LDLR). First, an ovarian LDLR cDNA sequence in Marsupenaeus japonicus was determined. Ovarian LDLR mRNA expression was then examined, and was seen to be specific to the ovary, exhibiting highest levels during the previtellogenic stage. This pattern of ovarian LDLR expression is thought to signify preparation for yolk protein incorporation into the oocyte. Using immunoblotting techniques, an ovarian LDLR band was detected whose size was similar to that estimated from the deduced amino acid sequence. The ovarian LDLR protein was expressed only at the onset of vitellogenesis, and histological studies supported these observations. This is the first occasion that the ovarian LDLR and its expression dynamics during vitellogenesis have been fully characterized in a crustacean.

Berberine-induced LDLR up-regulation involves JNK pathway

Berberine, an herbal alkaloid, has been reported to have a lipid lowering effect by stabilizing hepatic LDLR mRNA in an ERK-dependent manner rather than promoting transcriptional activity. However, considering the complexity of interconnected signal pathways in biological processes, it is highly possible that there exist signal pathway(s) other than ERK pathway which contribute to the berberine-induced up-regulation of LDLR. In the present study, we examined possible involvement of other signal pathways in berberine-induced hepatic LDLR up-regulation. As evidenced by RT-PCR, berberine-induced LDLR mRNA expression was inhibited by JNK inhibitor SP600125 pretreatment. Furthermore, we demonstrate that putative c-jun binding site of LDLR promoter is important in berberine-induced LDLR transcription using luciferase assay. The result of EMSA also shows that berberine induces c-jun binding to LDLR promoter and this is decreased by SP600125 pretreatment. The present study demonstrates that berberine increases transcriptional activity of LDLR promoter and this involves JNK pathway.

Blockage of oncostatin M-induced LDL receptor gene transcription by a dominant-negative mutant of C/EBPβ

OM (oncostatin M) activates the human LDLR [LDL (low-density lipoprotein) receptor] gene transcription in HepG2 cells through the SIRE (sterol-independent regulatory element) of LDLR promoter. The SIRE sequence consists of a C/EBP (CCAAT/enhancer-binding protein)-binding site and a CRE (cAMP-response element). Our previous studies [Zhang, Ahlborn, Li, Kraemer and Liu (2002) J. Lipid Res. 43, 1477-1485; Zhang, Lin, Abidi, Thiel and Liu (2003) J. Biol. Chem. 278, 44246-44254] have demonstrated that OM transiently induces EGR-1 (early growth response gene product 1) expression and EGR-1 activates LDLR transcription primarily through a protein-protein interaction with C/EBPbeta, which serves as a co-activator of EGR-1. In the present study, we examined the direct role of C/EBPbeta as a transactivator in OM-regulated LDLR gene transcription independent of EGR-1. We show that OM induces C/EBPbeta expression with kinetics slower than EGR-1 induction. A significant increase in C/EBPbeta protein level is detected by 2 h of OM treatment and remains elevated for 24 h. Chromatin immunoprecipitation assays demonstrate that the amount of C/EBPbeta bound to the LDLR SIRE sequence is increased 2.8-fold of control by 2 h of OM treatment, reached the highest level of 8-fold by 4 h, and slowly declined thereafter. To further examine the requirement of C/EBPbeta in OM-stimulated LDLR expression, we developed a His-tagged dominant-negative mutant of C/EBPbeta (His-C/EBPbeta-P4; where P4 is plasmid 4 in our mutation series), consisting of the DNA-binding and leucine zipper domains of C/EBPbeta (amino acids 246-345). Expression of His-C/EBPbeta-P4 in HepG2 cells significantly diminishes the OM-induced increase in LDLR promoter activity and the elevation of endogenous LDLR mRNA expression. Taken together, these new findings identify C/EBPbeta as an OM-induced transactivator in LDLR gene transcription and provide a better understanding of the molecular mechanism underlying the sterol-independent regulation of LDLR expression.

Association of LDLR gene polymorphisms with LDLR mRNA expression in mononuclear cells and response to atorvastatin therapy in subjects with heterozygous familial hypercholesterolemia

Association of LDLR gene polymorphisms with LDLR mRNA expression in mononuclear cells and response to atorvastatin therapy in subjects with heterozygous familial hypercholesterolemia

Fatty acid regulates gene expression and growth of human prostate cancer PC-3 cells.

It has been proposed that the omega-6 fatty acids increase the rate of tumor growth. Here we test that hypothesis in the PC-3 human prostate tumor. We found that the essential fatty acids, linoleic acid (LA) and arachidonic acid (AA), and the AA metabolite PGE(2) stimulate tumor growth while oleic acid (OA) and the omega-3 fatty acid, eicosapentaenoic acid (EPA) inhibited growth. In examining the role of AA in growth response, we extended our studies to analyze changes in early gene expression induced by AA. We demonstrate that c-fos expression is increased within minutes of addition in a dose-dependent manner. Moreover, the immediate early gene cox-2 is also increased in the presence of AA in a dose-dependent manner, while the constitutive cox-1 message was not increased. Three hours after exposure to AA, the synthesis of PGE(2) via COX-2 was also increased. Previous studies have demonstrated that AA was primarily delivered by low density lipoprotein (LDL) via its receptor (LDLr). Since it is known that hepatomas, acute myelogenous leukemia and colorectal tumors lack normal cholesterol feedback, we examined the role of the LDLr in growth regulation of the PC-3 prostate cancer cells. Analysis of ldlr mRNA expression and LDLr function demonstrated that human PC-3 prostate cancer cells lack normal feedback regulation. While exogenous LDL caused a significant stimulation of cell growth and PGE(2) synthesis, no change was seen in regulation of the LDLr by LDL. Taken together, these data show that normal cholesterol feedback of ldlr message and protein is lost in prostate cancer. These data suggest that unregulated over-expression of LDLr in tumor cells would permit increased availability of AA, which induces immediate early genes c-fos and cox-2 within minutes of uptake.

Coordinate up-regulation of low-density lipoprotein receptor and cyclo-oxygenase-2 gene expression in human colorectal cells and in colorectal adenocarcinoma biopsies.

Many colorectal cancers have high levels of cyclo-oxygenase 2 (COX-2), an enzyme that metabolizes the essential fatty acids into prostaglandins. Since the low-density lipoprotein receptor (LDLr) is involved in the uptake of essential fatty acids, we studied the effect of LDL on growth and gene regulation in colorectal cancer cells. DiFi cells grown in lipoprotein-deficient sera (LPDS) grew more slowly than cells with LDL. LDLr antibody caused significant inhibition of tumor cell growth but did not affect controls. In addition, LDL uptake did not change in the presence of excess LDL, suggesting that ldlr mRNA lacks normal feedback regulation in some colorectal cancers. Analysis of the ldlr mRNA showed that excess LDL in the medium did not cause down-regulation of the message even after 24 hr. The second portion of the study examined the mRNA expression of ldlr and its co-regulation with cox-2 in normal and tumor specimens from patients with colorectal adenocarcinomas. The ratio of tumor:paired normal mucosa of mRNA expression of ldlr and of cox-2 was measured in specimens taken during colonoscopy. ldlr and cox-2 transcripts were apparent in 11 of 11 carcinomas. There was significant coordinate up-regulation both of ldlr and of cox-2 in 6 of 11 (55%) tumors compared with normal colonic mucosa. There was no up-regulation of cox-2 without concomitant up-regulation of ldlr. These data suggest that the LDLr is abnormally regulated in some colorectal tumors and may play a role in the up-regulation of cox-2.