scholarly journals A discoordinate increase in the cellular amount of 3-hydroxy-3-methylglutaryl-CoA reductase results in the loss of rate-limiting control over cholesterogenesis in a tumour cell-free system

1989 ◽  
Vol 258 (2) ◽  
pp. 421-425 ◽  
Author(s):  
N I Azrolan ◽  
P S Coleman
Keyword(s):  
Cholesterol Biosynthesis ◽  
Normal Liver ◽  
Preliminary Evidence ◽  
Free System ◽  
Normal Rat ◽  
Morris Hepatoma ◽  
Coa Reductase ◽  
Rate Limiting ◽  
Hydroxymethylglutaryl Coa Reductase ◽  
Tumour System

Cholesterol biosynthesis was characterized in cell-free post-mitochondrial supernatant systems prepared from both normal rat liver and Morris hepatoma 3924A. The rate of cholesterol synthesis per cell was 9-fold greater in the tumour system than in that from normal liver, and the tumour systems showed the loss of rate-limiting control at the hydroxymethylglutaryl-CoA reductase (HMGR)-catalysed step. The apparent absence of rate-limiting control over cell-free tumour cholesterogenesis was traced primarily to a discoordinate and dramatic increase in the amount of HMGR in the tumour relative to the liver system. Preliminary evidence for an altered control of the post-lanosterol portion of the pathway was also obtained with the tumour system.

scholarly journals 3-Hydroxy-3-methylglutaryl coenzyme A reductase localization in rat liver peroxisomes and microsomes of control and cholestyramine-treated animals: quantitative biochemical and immunoelectron microscopical analyses.

1986 ◽  
Vol 103 (3) ◽  
pp. 875-886 ◽  
Author(s):  
G A Keller ◽  
M Pazirandeh ◽  
S Krisans
Keyword(s):  
Rat Liver ◽  
Coenzyme A ◽  
Specific Activity ◽  
Reductase Activity ◽  
Cholesterol Biosynthesis ◽  
Normal Liver ◽  
Hmg Coa Reductase ◽  
The Matrix ◽  
Coa Reductase ◽  
Liver Peroxisomes

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, a key regulatory enzyme involved in cholesterol biosynthesis, has recently been reported to be present in rat liver peroxisomes (Keller, G.A., M.C. Barton, D.J. Shapiro, and S.J. Singer, 1985, Proc. Natl. Acad. Sci. USA, 82:770-774). Immunoelectron labeling of ultrathin frozen sections of normal liver, using two monoclonal antibodies to purified rat liver microsomal HMG-CoA reductase, indicated that the enzyme is present in the matrix of peroxisomes. This study is a quantitative biochemical and immunoelectron microscopical analysis of HMG-CoA reductase in rat liver peroxisomes and microsomes of normal and cholestyramine-treated animals. Cholestyramine treatment produced a six- to sevenfold increase in the specific activity of peroxisomal HMG-CoA reductase, whereas the microsomal HMG-CoA reductase specific activity increased by about twofold. Using a computer program that calculates optimal linear combinations of marker enzymes, it was determined that between 20 and 30% of the total reductase activity was located in the peroxisomes of cholestyramine-treated animals. Less than 5% of the reductase activity was present in peroxisomes under control conditions. Quantitation of the immunoelectron microscopical data was in excellent agreement with the biochemical results. After cholestyramine treatment there was an eightfold increase in the density of gold particles per peroxisome, and we estimate about a threefold increase in the labeling of the ER.

scholarly journals Inhibition by the fungicide fenpropimorph of cholesterol biosynthesis in 3T3 fibroblasts

1988 ◽  
Vol 256 (3) ◽  
pp. 829-834 ◽  
Author(s):  
M F Corio-Costet ◽  
N Gerst ◽  
P Benveniste ◽  
F Schuber
Keyword(s):  
Mammalian Cells ◽  
Higher Plants ◽  
Reductase Activity ◽  
Cholesterol Biosynthesis ◽  
Acetate Incorporation ◽  
3T3 Fibroblasts ◽  
Dependent Inhibition ◽  
Dose Dependent Inhibition ◽  
Coa Reductase ◽  
Hydroxymethylglutaryl Coa Reductase

Fenpropimorph (N-[3-(p-t-butylphenyl)-2-methylpropyl]-cis-2,6-dimethylmorpholine), a morpholine fungicide known to be an inhibitor of sterol biosynthesis in fungi and in higher plants, was demonstrated to be an efficient inhibitor of cholesterol biosynthesis in cultured Swiss 3T3 fibroblasts. Treatment of the mammalian cells with fenpropimorph resulted in a dose-dependent inhibition of [14C]acetate incorporation into the C27 sterols [IC50 (concentration causing half-maximal inhibition) = 0.5 microM], which was accompanied by an accumulation of polar sterols and a decrease in cellular hydroxymethylglutaryl-CoA reductase activity. Exposure of the cells to the drug affected cell growth. Analysis of the sterols in the growth-arrested and in the pulse-labelled cells indicate that fenpropimorph has, in the sterol-biosynthetic pathway, target enzymes in mammalian cells different from those in the other phyla. Whereas in plants and fungi fenpropimorph mainly affects sterol isomerases and reductases, in the fibroblasts its main target seems to be the demethylation of lanosterol.

scholarly journals High-Risk Polymorphisms Associated with the Molecular Function of Human HMGCR Gene Infer the Impedance of Cholesterol Biosynthesis

2021 ◽  
Author(s):  
Keshob Chandra Das ◽  
Mohammad Uzzal Hossain ◽  
Md Moniruzzaman ◽  
Md Salimullah ◽  
Sharif Akhteruzzaman
Keyword(s):  
Solvent Accessibility ◽  
Cholesterol Biosynthesis ◽  
Functional Domain ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
Functional Instability ◽  
Structural Evaluation ◽  
Coa Reductase ◽  
Rate Limiting ◽  
Major Target

Abstract Background: HMG-CoA reductase or HMGCR (3-Hydroxy-3-methylglutaryl-CoA reductase) is a rate-limiting enzyme involved in cholesterol biosynthesis. HMGCR plays an important role in the possible occurrence of hypercholesterolemia leading to atherosclerosis and coronary heart disease. This enzyme is a major target for cholesterol lowering drugs such as “statins” which blocks the synthesis of mevalonate, a precursor for cholesterol biosynthesis. This study aims to characterize deleterious mutations and classify functional Single Nucleotide Polymorphisms (SNPs) of the HMGCR gene through analysis of functional and structural evaluation, domain association, solvent accessibility, and energy minimization studies. Results: Among 6,815 SNP entries from different databases, approximately 388 SNPs were found to be missense. Analysis showed that seven missense SNPs are more likely to have deleterious effects. A tertiary model of the mutant protein was constructed to determine the functional and structural effects of the HMGCR mutation. In addition, the location of the mutations suggests that they may have deleterious effects because most of the mutations are resides in the functional domain of the protein. The findings from the bunch of bioinformatics tools predicted that rs147043821 and rs193026499 missense SNPs could cause significant structural and functional instability in the mutated proteins of the HMGCR gene. Conclusion: Therefore, the results of the current study would undoubtedly be accommodating in future endeavors concerning drug discovery and therapeutics against hypercholesterolemia.

scholarly journals N-acetylneuraminic acid, phosphate and thiol groups of pyruvate kinase isoenzymes from Morris hepatoma 7777 and normal rat liver.

1997 ◽  
Vol 44 (2) ◽  
pp. 201-208 ◽  
Author(s):  
J Ignacak ◽  
M Gumińska
Keyword(s):  
Pyruvate Kinase ◽  
Electrophoretic Mobility ◽  
Rat Liver ◽  
Amino Acid Content ◽  
Normal Liver ◽  
Regulatory Change ◽  
Thiol Groups ◽  
Acetylneuraminic Acid ◽  
Normal Rat ◽  
Morris Hepatoma

The highest amount of N-acetylneuraminic acid (AcNeu) was found in pyruvate kinase isoenzyme L from normal rat liver (24 moles/mole of enzyme tetramer), with the highest electrophoretic mobility. On the other hand, isoenzyme M2 from Morris hepatoma 7777, with the lowest electrophoretic mobility, had the lowest AcNeu content (5 moles/mole of enzyme tetramer). This tumour isoenzyme M2 of pyruvate kinase was, however, characterised by the highest phosphate content (12 moles/mole protein), in comparison to isoenzyme L (3 moles/mole protein) or normal liver isoenzyme M2 (6 moles/mole protein). This could indicate a regulatory change caused by reversible enzyme phosphorylation and dephosphorylation or sialization and desialization. Despite these differences, the sum of the two negatively charged residues was lower in tumour pyruvate kinase isoenzyme M2, with the slowest migration rate, than in normal rat liver isoenzyme M2. Moreover, isoenzyme M2 from tumour material, in comparison with isoenzyme M2 from normal rat liver, had a twice as high content of thiol groups (20 moles/mole protein), especially of free and superficially located ones, than the isoenzyme M2 from normal liver (10 moles/mole protein). This may explain abnormal susceptibility of tumour isoenzyme M2 to stereospecific inhibition by exogenous L-cysteine, and indicate genetically dependent changes in amino-acid content of tumour enzyme which take place during cell tumourigenic transformation.

Statins in Sepsis

2010 ◽  
Vol 23 (1) ◽  
pp. 38-49 ◽  
Author(s):  
Paul P. Dobesh ◽  
Stephanie M. Swahn, PharmD Candidate ◽  
Evan J. Peterson, PharmD Candidate ◽  
Keith M. Olsen
Keyword(s):  
Cholesterol Biosynthesis ◽  
Platelet Activating Factor ◽  
Population Based ◽  
Sepsis Syndrome ◽  
Positive Effects ◽  
Rate Limiting Step ◽  
Poor Outcomes ◽  
Coa Reductase ◽  
The Impact ◽  
Rate Limiting

Sepsis is a common intensive care unit event occurring in approximately 750 000 patients annually, with a case mortality rate approaching 50%. Sepsis is characterized by a chaotic and excessive release of inflammatory cytokines and procoagulants including tumor necrosis factor, interleukin (IL)-1, IL-6, IL-8, platelet-activating factor, and tissue factor. Efforts to inhibit individual cytokines in order to modify poor outcomes have been generally disappointing, suggesting the need to target multiple inflammatory mediators to obtain clinical benefit. Statins lower lipids by inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, which in turn inhibits the rate-limiting step in cholesterol biosynthesis. In addition to lowering total cholesterol, statins have pleiotropic effects on inflammation and immunity. Instead of impacting a single entity in the sepsis syndrome, statins may have positive effects on multiple inflammatory, immunomodulating, and coagulation targets involved in the development of infection and sepsis. There have been a number of institutional- and population-based studies that have evaluated the impact of statins in patients with infection and sepsis. Most of these studies, but not all, have demonstrated a number of positive outcomes in patients with statins, including reduction in mortality. Based on these data, statins are a promising therapy in the management of patients with sepsis and warrant larger and more rigorous clinical trials.

scholarly journals A Novel Statin Compound from Monacolin J Produced Using CYP102A1-Catalyzed Regioselective C-Hydroxylation

2021 ◽  
Vol 14 (10) ◽  
pp. 981
Author(s):  
Ngoc Tan Cao ◽  
Ngoc Anh Nguyen ◽  
Chan Mi Park ◽  
Gun Su Cha ◽  
Ki Deok Park ◽  
...  
Keyword(s):  
Cholesterol Biosynthesis ◽  
Liver Microsomes ◽  
Red Yeast Rice ◽  
High Catalytic Activity ◽  
Hmg Coa Reductase ◽  
Drug Candidates ◽  
New Strategy ◽  
Statin Drug ◽  
Coa Reductase ◽  
Rate Limiting

Statins inhibit the 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMG-CoA reductase), which is the rate-limiting enzyme in cholesterol biosynthesis. Statin therapy reduces morbidity and mortality in those who are at high risk of cardiovascular disease. Monacolin J is a statin compound, which is an intermediate in the lovastatin biosynthesis pathway, in the fungus Aspergillus terreus. It is also found in red yeast rice, which is made by culturing rice with the yeast Monascus purpureus. Monacolin J has a hydroxyl substituent at position C’-8 of monacolin L. Here, a new statin derivative from monacolin J was made through the catalysis of CYP102A1 from Bacillus megaterium. A set of CYP102A1 mutants of monacolin J hydroxylation with high catalytic activity was screened. The major hydroxylated product was C-6′a-hydroxymethyl monacolin J, whose structure was confirmed using LC–MS and NMR analysis. The C-6′a-hydroxymethyl monacolin J has never been reported before. It showed a greater ability to inhibit HMG-CoA reductase than the monacolin J substrate itself. Human liver microsomes and human CYP3A4 also showed the ability to catalyze monacolin J in producing the same product of the CYP102A1-catalyzed reaction. This result motivates a new strategy for the development of a lead for the enzymatic and chemical processes to develop statin drug candidates.

scholarly journals Polyphenols from Citrus Tacle® Extract Endowed with HMGCR Inhibitory Activity: An Antihypercholesterolemia Natural Remedy

Molecules ◽  
2021 ◽  
Vol 26 (18) ◽  
pp. 5718
Author(s):  
Fedora Grande ◽  
Maria Antonietta Occhiuzzi ◽  
Maria Rosaria Perri ◽  
Giuseppina Ioele ◽  
Bruno Rizzuti ◽  
...  
Keyword(s):  
Cholesterol Biosynthesis ◽  
Citrus Fruit ◽  
Direct Interaction ◽  
Binding Modes ◽  
Vitro Assay ◽  
Docking Simulations ◽  
Natural Remedy ◽  
Coa Reductase ◽  
Hydroxymethylglutaryl Coa Reductase

Tacle® is a citrus fruit obtained from the crossbreeding of Clementine and Tarocco cultivars. This fruit retains a promising nutraceutical potential most likely due to a high content in polyphenols, among which the main constituents are the two glycosides naringin and hesperidin. Herein, we evaluated, through an in vitro assay, the capability of Tacle extracts to inhibit the hydroxymethylglutaryl-CoA reductase enzyme, which plays a key role in cholesterol biosynthesis. The results obtained spurred us to investigate whether the anti-enzymatic activity observed may be due to a direct interaction of aglycones naringenin and hesperetin with the enzyme catalytic site. Molecular docking simulations indicated that these two compounds are able to anchor to the protein with binding modes and affinities similar to those found for statins, which represent mainstream medications against hypercholesterolemia. The overall results showed an interesting nutraceutical potential of Tacle, suggesting that its extract could be used for dietary supplementation in the treatment of moderate hypercholesterolemia.

scholarly journals Stimulation of liver cholesterol synthesis by actinomycin D

1968 ◽  
Vol 109 (5) ◽  
pp. 775-785 ◽  
Author(s):  
F. De Matteis
Keyword(s):  
Actinomycin D ◽  
Ketone Bodies ◽  
Cholesterol Biosynthesis ◽  
Mevalonic Acid ◽  
Liver Cholesterol ◽  
Tenfold Increase ◽  
Coa Reductase ◽  
Rate Limiting ◽  
Stimulation Of

1. An eightfold increase in the incorporation of [2−14C]acetate into liver cholesterol in vivo was observed 24hr. after starved rats had been given actinomycin D (0·5mg./kg. of body wt.). Liver cholesterol radioactivity declined faster in the treated animals, suggesting a greater rate of cholesterol turnover. 2. Liver slices from treated animals showed a tenfold increase in the incorporation of [2−14C]acetate into cholesterol; conversion into CO2 and into fatty acids was less markedly increased, and conversion into ketone bodies was not significantly affected. 3. The patterns of conversion into liver cholesterol in vivo of the lactone and the sodium salt of mevalonic acid differed markedly. The former was converted at a faster rate and to a greater extent than the latter. Treatment with actinomycin D increased the conversion of both forms of mevalonic acid into liver cholesterol, but only to a small extent. 4. Stimulation of the incorporation of acetate into cholesterol occurred at 4hr. after the administration of actinomycin D but not at 2hr. The response was abolished by the simultaneous administration of dl-ethionine or puromycin. 5. Pre-feeding with a cholesterol-rich diet greatly diminished the stimulation of conversion of acetate into cholesterol caused by actinomycin D, though it did not completely suppress it. Adrenalectomized animals responded to the drug, but much less markedly. 6. It is concluded that actinomycin D stimulates the synthesis of cholesterol in the liver at a stage in the pathway before mevalonic acid, by a mechanism that probably requires protein synthesis. A likely site would be the β-hydroxy-β-methylglutaryl-CoA reductase, the rate-limiting enzyme in cholesterol biosynthesis. Some possible mechanisms by which the drug may lead to increased activity of this enzyme are considered.

scholarly journals The role of substrate supply in the regulation of cholesterol biosynthesis in rat hepatocytes

1983 ◽  
Vol 210 (3) ◽  
pp. 625-632 ◽  
Author(s):  
C R Pullinger ◽  
G F Gibbons
Keyword(s):  
Biosynthetic Pathway ◽  
Reductase Activity ◽  
Cholesterol Biosynthesis ◽  
Rat Hepatocytes ◽  
Sterol Synthesis ◽  
Hmg Coa Reductase ◽  
Coa Reductase ◽  
Opposing Effects ◽  
Hydroxymethylglutaryl Coa Reductase

1. Compactin, (-)-hydroxycitrate and dexamethasone gave rise to a decrease in the rate of cholesterol production in hepatocytes from fed rats by interfering with the flow of substrate into the sterol biosynthetic pathway. The cells responded to the deficit of biosynthetic sterol by increasing the activity of hydroxymethylglutaryl-CoA reductase (HMG-CoA reductase). 2. Compactin and (-)-hydroxycitrate gave similar results in hepatocytes from rats starved for 24 h but in this case dexamethasone had no significant effect. 3. Exogenous oleate interferes with the production of carbohydrate-derived acetyl-CoA and also gives rise initially to opposing effects on the rate of sterol synthesis and HMG-CoA reductase activity. Over a longer period, however, oleate itself was capable of replacing carbohydrate as the major source of carbon for sterol synthesis. 4. The increase in HMG-CoA reductase activity observed when liver cells were incubated in the presence of compactin, (-)-hydroxycitrate or oleate could be partially reversed by the simultaneous presence of glucagon. 5. Under some physiological conditions, a deficiency of biosynthetic cholesterol or of a related precursor may lead to an increase in the activity of HMG-CoA reductase.

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