scholarly journals Soya phytoestrogens, genistein and daidzein, decrease apolipoprotein B secretion from HepG2 cells through multiple mechanisms

2002 ◽  
Vol 366 (2) ◽  
pp. 531-539 ◽  
Author(s):  
Nica M. BORRADAILE ◽  
Linda E. de DREU ◽  
Lisa J. WILCOX ◽  
Jane Y. EDWARDS ◽  
Murray W HUFF
Keyword(s):  
Hepg2 Cells ◽  
Cholesterol Synthesis ◽  
Cholesterol Metabolism ◽  
Plasma Cholesterol ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Mrna Levels ◽  
Apo B ◽  
Cellular Cholesterol ◽  
Apob Secretion

Diets containing the soya-derived phytoestrogens, genistein and daidzein, decrease plasma cholesterol in humans and experimental animals. The mechanisms responsible for the hypocholesterolaemic effects of these isoflavones are unknown. The present study was conducted to determine if genistein and daidzein regulate hepatocyte cholesterol metabolism and apolipoprotein (apo) B secretion in cultured human hepatoma (HepG2) cells. ApoB secretion was decreased dose-dependently by up to 63% and 71% by genistein and daidzein (100μM; P<0.0001) respectively. In contrast, no effect on apoAI secretion was observed. Cellular cholesterol synthesis was inhibited 41% by genistein (100μM; P<0.005) and 18% by daidzein (100μM; P<0.05), which was associated with significant increases in 3-hydroxy-3-methylglutaryl-CoA reductase mRNA. Cellular cholesterol esterification was decreased 56% by genistein (100μM; P<0.04) and 29% by daidzein (100μM; P<0.04); however, mRNA levels for acyl-CoA:cholesterol acyltransferase (ACAT) 1 and ACAT2 were unaffected. At 100μM, both isoflavones equally inhibited the activities of both forms of ACAT in cells transfected with either ACAT1 or ACAT2. Genistein (100μM) and daidzein (100μM) significantly decreased the activity of microsomal triacylglycerol transfer protein (MTP) by 30% and 24% respectively, and significantly decreased MTP mRNA levels by 35% and 55%. Both isoflavones increased low-density lipoprotein (LDL)-receptor mRNA levels by 3- to 6-fold (100μM; P<0.03) and significantly increased the binding, uptake and degradation of 125I-labelled LDL, suggesting that enhanced reuptake of newly secreted apoB-containing lipoproteins contributed to the net decrease in apoB secretion. These results indicate that genistein and daidzein inhibit hepatocyte apoB secretion through several mechanisms, including inhibition of cholesterol synthesis and esterification, inhibition of MTP activity and expression and increased expression of the LDL-receptor.

scholarly journals Effect of reduced low-density lipoprotein receptor level on HepG2 cell cholesterol metabolism

1998 ◽  
Vol 329 (1) ◽  
pp. 81-89 ◽  
Author(s):  
Lahoucine IZEM ◽  
Eric RASSART ◽  
Lassana KAMATE ◽  
Louise FALSTRAULT ◽  
David RHAINDS ◽  
...  
Keyword(s):  
Hepg2 Cell ◽  
Hepg2 Cells ◽  
Cholesterol Metabolism ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Constitutive Expression ◽  
Density Lipoprotein ◽  
Low Density ◽  
Apo B ◽  
Acat Activity

Low-density lipoproteins (LDL) are taken up by both LDL receptor (LDLr)-dependent and -independent pathways. In order to determine the importance of these pathways in the activity of the various enzymes that are important in maintaining the cellular cholesterol level in hepatic cells, we created HepG2 cells expressing lower levels of LDLr. Thus HepG2 cells were transfected with a constitutive expression vector (pRc/CMV) containing a fragment of LDLr cDNA inserted in an antisense manner. Stable transformants were obtained that showed significant reductions of 42, 72 and 85% of LDLr protein levels compared with the control, as demonstrated by immunoblotting and confirmed by the LDL binding assay. The best inactivation was achieved with the construct containing the first 0.7 kb of LDLr cDNA. Incubating the different HepG2 cell subtypes with LDL showed similar association of apolipoprotein B (apo B) or cholesteryl esters from LDL with the cells, indicating that the LDLr deficiency did not significantly affect LDL uptake by the cell. However, apoB degradation was reduced significantly by 71-82% in the most LDLr-deficient HepG2 cells. We also found that 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCoA red) activity is significantly increased by 32-35% in HepG2 cells expressing very low levels of LDLr that also demonstrate a significant decrease of 20% in acyl-CoA:cholesterol acyltransferase (ACAT) activity. However, these effects are moderate compared with those observed when cells were incubated in lipoprotein-depleted medium, where a > 900% increase in HMGCoA red activity and a loss of 60% of ACAT activity was observed. Thus, in HepG2 cells, different levels of LDLr affect LDL-apoB degradation, but have very little effect on LDL association, HMGCoA red and ACAT activities, revealing that LDLr is more important in the clearance of LDL-apoB than in HepG2 cell cholesterol homoeostasis, a role that should be attributable to both LDLr-dependent and -independent pathways.

scholarly journals Lathosterol in plasma measures cholesterol synthesis and identifies the efficiency of dietary phytosterols in reducing the plasma cholesterol concentration

2020 ◽  
Author(s):  
Valeria Sutti Nunes ◽  
Angela Oliveira Godoy Ilha ◽  
Guilherme Silva Ferreira ◽  
Renata Paula Assis Bombo ◽  
Milessa Silva Afonso ◽  
...  
Keyword(s):  
Cholesterol Synthesis ◽  
Plasma Cholesterol ◽  
Density Lipoprotein ◽  
Lipoprotein Cholesterol ◽  
Cholesterol Concentration ◽  
Synthesis Rate ◽  
Soy Milk ◽  
Apo B ◽  
Cholesterol Ratio ◽  
Placebo Phase

Abstract Background Because the plasma campesterol/cholesterol ratio does not differ between groups that absorb different amounts of cholesterol measured by the gold standard isotopic procedure we investigated whether the intestinal absorption of phytosterols (PS) depends on the body's cholesterol synthesis rate. Methods 38 volunteers (58 ± 12 years; low-density lipoprotein cholesterol (LDL-C) ≥ 130 mg/dL) were randomly assigned to consume 400 mL/day of soy milk or soy milk + PS (1.6 g/day) for 4 weeks in a double-blind, placebo-controlled, cross-over study. Blood samples were collected and markers of phytosterol (PS) absorption and non-cholesterol sterol synthesis precursors measured. Results PS treatment reduced plasma total cholesterol concentration (-5,5%, p < 0.001), LDL-C (-7.6%, p < 0.001), triglycerides (-13.6%, p < 0.0085), and apolipoprotein B (apo B) (-6.3%, p < 0.008), without changing high density lipoprotein cholesterol (HDL-C concentration). The lathosterol-to-cholesterol ratio in serum predicted the serum cholesterol response to PS feeding where high basal cholesterol synthesis was associated with lack of response of plasma cholesterol to PS in the diet. Cholesterol synthesis being elevated in the placebo phase in non-responders to dietary PS indicated they were resistant to further synthesis rise, whereas responders, because they have lower synthesis rate than non-responders in the placebo phase, are capable expanding synthesis under the effect of alimentary PS. Conclusions responders absorbed more PS than non-responders likely resulting from responders delivering less endogenous cholesterol than non-responders into the intestinal lumen that facilitates greater absorption of PS by the intestine.

Mutations that affect membrane receptor for LDL are useful for studying normal receptor function

1982 ◽  
Vol 243 (1) ◽  
pp. E5-E14
Author(s):  
R. G. Anderson
Keyword(s):  
Cell Biology ◽  
Cholesterol Metabolism ◽  
Plasma Cholesterol ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Cholesterol Transport ◽  
Low Density ◽  
Receptor Function ◽  
Coated Pits

Low-density lipoprotein (LDL), the major plasma cholesterol transport protein, is taken up by cells through a receptor-mediated process. After internalization through specialized segments of the cell surface called coated pits, the LDL is degraded in the lysosome and the released cholesterol is used by cells to meet various metabolic needs. The discovery of the LDL receptor and the studies of its function have provided new insights into both the biochemical aspects of cholesterol metabolism and the cell biology of receptor-mediated endocytosis. Of paramount importance in all of these studies has been the availability of human cells that express one or more allelic mutations that affect the function of the LDL receptor. These mutations have been valuable for assessing normal receptor function. Just as important, these mutations have been used as a reference point in the development of various cytochemical and biochemical techniques for studying receptor activity.

scholarly journals Two Weeks of Western Diet Disrupts Liver Molecular Markers of Cholesterol Metabolism in Rats

2020 ◽  
Author(s):  
Roxane Saint-Amand ◽  
Emilienne T. Ngo Sock ◽  
Samantha Quinn ◽  
Jean-Marc Lavoie ◽  
David H. St-Pierre
Keyword(s):  
De Novo ◽  
Cholesterol Metabolism ◽  
Plasma Cholesterol ◽  
Ldl Receptor ◽  
Mrna Levels ◽  
Fat Pad ◽  
Cholesterol Uptake ◽  
Cholesterol Levels ◽  
Gene Coding ◽  
Main Regulator

Abstract Background The present study was designed to test the hypothesis that excessive fat accumulations impair cholesterol metabolism mainly through alterations in the LDL-receptor (LDL-R) pathway in liver. Method: Rats were either submitted to standard (SD), high fat (HFD; 60% kcal) or western (WD; 40% fat + 35% sucrose (17.5% fructose)) diets for 2 or 6 weeks. Results Weight gain (~ 40 g) was observed only following 6 weeks of the obesogenic diets (P < 0.01). Compared to the 2-week treatment, obesogenic diets tripled fat pad weight (~ 20 vs 7 g) after 6 weeks. Hepatic triglyceride (TG) levels were greater in response to both the WD and HFD compared to the SD (P < 0.01) at 2 and 6 weeks and their concentrations were greater (P < 0.05) in WD than HFD at 2 weeks. Plasma cholesterol levels were higher (P < 0.05) in animals submitted to WD. After 2 and 6 weeks, liver expression of LDL-R, PCSKk9 and SREBP2, involved in LDL-cholesterol uptake, was lower in animals submitted to WD than in others treated with HFD or SD (P < 0.01). Similarly, LRP1 and ACAT2 mRNA levels were lower (P < 0.01) among WD compared to SD-fed rats. Expression of the gene coding the main regulator of endogenous cholesterol synthesis, HMGCoAR was reduced in response to WD compared to SD and HFD at 2 (P < 0.001) and 6 (P < 0.05) weeks. Being enriched in fructose, the WD strongly promoted the expression of ChREBP and ACC, two key regulators of de novo lipogenesis. Conclusion These results show that the WD promptly increased TG levels in the liver by potentiating dietary fat storage and de novo lipogenesis. This impaired the pathway of hepatic cholesterol uptake via the LDL-R axis, promoting a rapid increase in plasma cholesterol levels.

scholarly journals Inhibition of cholesterol synthesis reduces low-density-lipoprotein apoprotein B production without decreasing very-low-density-lipoprotein apoprotein B synthesis in rabbits

1984 ◽  
Vol 219 (1) ◽  
pp. 321-323 ◽  
Author(s):  
A La Ville ◽  
R Moshy ◽  
P R Turner ◽  
N E Miller ◽  
B Lewis
Keyword(s):  
Cholesterol Synthesis ◽  
Plasma Cholesterol ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Competitive Inhibitor ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Apo B ◽  
Apoprotein B ◽  
Kinetics Of

The kinetics of the apoprotein B (apo B) of very-low-density (VLDL; d less than 1.006) and low-density (LDL; d 1.019-1.063) lipoproteins were studied in six rabbits by using radioiodinated homologous lipoproteins, before and during oral administration of mevinolin (5 mg/kg per day), a competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (EC 1.1.1.34), to explore the mechanism by which the drug reduces LDL synthesis. Before treatment LDL-apo B production greatly exceeded VLDL-apo B production in all animals, indicating that a large proportion of plasma LDL was derived from a VLDL-independent pathway. Five animals responded to mevinolin with a fall in plasma cholesterol (mean change − 53%; P less than 0.01). This was associated with a 66% decrease in LDL-apo B synthesis (P less than 0.05). In contrast, VLDL-apo B synthesis was unaffected by mevinolin. Furthermore, in all but one animal the decrement in LDL-apo B synthesis was greater than the rate of VLDL-apo B synthesis before treatment, demonstrating that mevinolin had reduced the VLDL-independent production of LDL.

Hydrogen sulfide accumulates LDL receptor precursor via downregulating PCSK9 in HepG2 cells

2020 ◽  
Vol 319 (6) ◽  
pp. C1082-C1096
Author(s):  
Yong Huang ◽  
Ke Ning ◽  
Wen-Wen Li ◽  
Ge Lin ◽  
Cui-Lan Hou ◽  
...  
Keyword(s):  
Hydrogen Sulfide ◽  
Transcriptional Activation ◽  
Hepg2 Cells ◽  
Mrna Level ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Cholesterol Homeostasis ◽  
Mrna Levels ◽  
Sodium Hydrosulfide ◽  
Protein Levels

Endogenous hydrogen sulfide (H2S) affects cholesterol homeostasis and liver X receptor α (LXRα) expression. However, whether low-density lipoprotein (LDL) receptor (LDLR), a key player in cholesterol homeostasis, is regulated by exogenous H2S through LXRα signaling has not been determined. We investigated the effects of sodium hydrosulfide (NaHS, H2S donor) on LDLR expression in the presence or absence of LXR agonists, T0901317 or GW3965 in HepG2 cells. We found that H2S strongly accumulated LDLR precursor in the presence of T0901317. Hence, LDLR transcription and the genes involved in LDLR precursor maturation and degradation were studied. T0901317 increased the LDLR mRNA level, whereas H2S did not affect LDLR transcription. H2S had no significant effect on the expression of LXRα and inducible degrader of LDLR (IDOL). H2S and T0901317 altered mRNA levels of several enzymes for N- and O-glycosylation and endoplasmic reticulum (ER) chaperones assisting LDLR maturation, but did not affect their protein levels. H2S decreased proprotein convertase subtilisin/kexin type 9 (PCSK9) protein levels and its mRNA level elevated by T0901317. T0901317 with PCSK9 siRNA also accumulated LDLR precursor as did T0901317 with H2S. High glucose increased PCSK9 protein levels and attenuated LDLR precursor accumulation induced by T0901317 with H2S. Taken together, H2S accumulates LDLR precursor by downregulating PCSK9 expression but not through the LXRα-IDOL pathway, LDLR transcriptional activation, or dysfunction of glycosylation enzymes and ER chaperones. These results also indicate that PCSK9 plays an important role in LDLR maturation in addition to its well-known effect on the degradation of LDLR mature form.

scholarly journals Rutin and Quercetin Decrease Cholesterol in HepG2 Cells but Not Plasma Cholesterol in Hamsters by Oral Administration

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3766
Author(s):  
Ning Liang ◽  
Yuk-Man Li ◽  
Zouyan He ◽  
Wangjun Hao ◽  
Yimin Zhao ◽  
...  
Keyword(s):  
Oral Administration ◽  
Hepg2 Cells ◽  
Cholesterol Metabolism ◽  
Plasma Cholesterol ◽  
Regulatory Element ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
In Vivo Studies

Rutin (R) and quercetin (Q) are two widespread dietary flavonoids. Previous studies regarding the plasma cholesterol-lowering activity of R and Q generated inconsistent results. The present study was therefore carried out to investigate the effects of R and Q on cholesterol metabolism in both HepG2 cells and hypercholesterolemia hamsters. Results from HepG2 cell experiments demonstrate that both R and Q decreased cholesterol at doses of 5 and 10 µM. R and Q up-regulated both the mRNA and protein expression of sterol regulatory element binding protein 2 (SREBP2), low-density lipoprotein receptor (LDLR), and liver X receptor alpha (LXRα). The immunofluorescence study revealed that R and Q increased the LDLR expression, while only Q improved LDL-C uptake in HepG2 cells. Results from hypercholesterolemia hamsters fed diets containing R (5.5 g/kg diet) and Q (2.5 g/kg diet) for 8 weeks demonstrate that both R and Q had no effect on plasma total cholesterol. In the liver, only Q reduced cholesterol significantly. The discrepancy between the in vitro and in vivo studies was probably due to a poor bioavailability of flavonoids in the intestine. It was therefore concluded that R and Q were effective in reducing cholesterol in HepG2 cells in vitro, whereas in vivo, the oral administration of the two flavonoids had little effect on plasma cholesterol in hamsters.

scholarly journals Ligand selectivity of 105 kDa and 130 kDa lipoprotein-binding proteins in vascular-smooth-muscle-cell membranes is unique

1996 ◽  
Vol 317 (1) ◽  
pp. 297-304 ◽  
Author(s):  
Valery N. BOCHKOV ◽  
Vsevolod A. TKACHUK ◽  
Maria P. PHILIPPOVA ◽  
Dimitri V. STAMBOLSKY ◽  
Fritz R. BÜHLER ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Binding Proteins ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Low Density ◽  
Dextran Sulphate ◽  
Apo B ◽  
Ligand Selectivity ◽  
Lipoprotein Binding

Using ligand blotting techniques, with low-density lipoprotein (LDL) as ligand, we have previously described the existence of atypical lipoprotein-binding proteins (105 kDa and 130 kDa) in membranes from human aortic medial tissue. The present study demonstrates that these proteins are also present in membranes from cultured human (aortic and mesenteric) and rat (aortic) vascular smooth-muscle cells (VSMCs). To assess the relationship of 105 and 130 kDa lipoprotein-binding proteins to known lipoprotein receptors, ligand binding specificity was studied. We tested effects of substances known to antagonize ligand binding to either the LDL [apolipoprotein B,E (apo B,E)] receptor (dextran sulphate, heparin, pentosan polysulphate, protamine, spermine, histone), the scavenger receptor (dextran sulphate, fucoidin), the very-low-density-lipoprotein (VLDL) receptor [receptor-associated protein (RAP)], or LDL receptor-related protein (RAP, α2-macroglobulin, lipoprotein lipase, exotoxin-A). None of these substances, with the exception of dextran sulphate, influenced binding of LDL to either 105 or 130 kDa proteins. Sodium oleate or oleic acid, known stimuli for the lipoprotein binding activity of the lipolysis-stimulated receptor, were also without effect. LDL binding to 105 and 130 kDa proteins was inhibited by anti-LDL (apo B) antibodies. LDL and VLDL bound to 105 and 130 kDa proteins with similar affinities (蝶50 μg/ml). The unique ligand selectivity of 105 and 130 kDa proteins supports the existence of a novel lipoprotein-binding protein that is distinct from all other currently identified LDL receptor family members. The similar ligand selectivity of 105 and 130 kDa proteins suggests that they may represent variant forms of an atypical lipoprotein-binding protein.

Bile Acids: The Good, the Bad, and the Ugly

Physiology ◽  
1999 ◽  
Vol 14 (1) ◽  
pp. 24-29 ◽  
Author(s):  
Alan F. Hofmann
Keyword(s):  
Bile Acids ◽  
Enterohepatic Circulation ◽  
Cholesterol Metabolism ◽  
Plasma Cholesterol ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Lipid Absorption ◽  
Bile Acid Metabolism ◽  
Cholesterol Levels ◽  
Density Lipoprotein Receptor

Bile acids, amphipathic end products of cholesterol metabolism, are “good” in the infant because they enhance lipid absorption and thereby promote growth. Bile acids also induce bile flow and biliary lipid secretion. The enterohepatic circulation of bile acids is “bad” in the adult because it downregulates hepatocyte low-density lipoprotein receptor activity and thereby elevates plasma cholesterol levels. Defects in bile acid metabolism such as impaired biosynthesis or transport are “ugly” because they cause morbidity and death. New approaches for treating these defects are being developed.

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