Iron depletion (ID) has been shown to induce the liver expression of Cyp7a1, the rate-limiting enzyme initiating conversion of cholesterol to bile acids (BA), although the effect on bile acids metabolism and bile production is unknown. Therefore, we investigated changes in bile secretion and BA synthesis during diet-induced iron depletion (ID) in rats. ID increased bile flow along with augmented biliary excretion of bile acids, glutathione, cholesterol and phospholipids. Accordingly, we found transcriptional upregulation of the Cyp7a1, Cyp8b1, and Cyp27a1 BA synthetic enzymes, as well as induction of the Abcg5/8 cholesterol transporters in ID rat livers. In contrast, intravenous infusion of3H-taurocholate failed to elicit any difference in biliary secretion of this compound in the ID rats. This corresponded with unchanged expression of canalicular rate-limiting transporters for BA as well as glutathione. We also observed that ID substantially changed the spectrum of BA in bile and decreased plasma concentrations of BA and cholesterol. Experiments with differentiated human hepatic HepaRG cells confirmed human CYP7A1 orthologue upregulation resulting from reduced iron concentrations. Results employing a luciferase reporter gene assay suggest that the transcriptional activation of the CYP7A1 promoter under ID conditions works independent of farnesoid X (FXR), pregnane X (PXR) and liver X (LXRα) receptors activation. It can be concluded that this study characterizes the molecular mechanisms of modified bile production as well as cholesterol as along with BA homeostasis during ID. We propose complex upregulation of BA synthesis, and biliary cholesterol secretion as the key factors affected by ID.

• MeSH
• buněčné linie MeSH
• cholesterol-7-alfa-hydroxylasa biosyntéza   MeSH
• cholesterol metabolismus   MeSH
• cytochrom P450 CYP271 biosyntéza   MeSH
• glutathion metabolismus   MeSH
• krysa rodu rattus MeSH
• lidé MeSH
• potkani Wistar MeSH
• steroid-12-alfa-hydroxylasa biosyntéza   MeSH
• železo nedostatek   MeSH
• žlučové kyseliny a soli biosyntéza   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• lidé MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The treatment of hypercholesterolemia with bile acid (BA) sequestrants results in upregulation of BA synthesis through the classical pathway initiated by cholesterol 7alpha-hydroxylase (CYP7A1). To characterize the detailed dynamics of serum lipid and BA concentrations and the BA synthesis rate in response to treatment with BA sequestrants and to determine whether the -203A/C promoter polymorphism of the CYP7A1 encoding gene (CYP7A1) affects such a response, this pilot study was carried out in healthy men (8 homozygous for the -203A allele and 8 homozygous for the -203C allele of CYP7A1). The subjects were treated for 28 days with colesevelam and blood was drawn for analysis before and on days 1, 3, 7, 14 and 28 of treatment. The response of lipids, BA, fibroblast growth factor-19 (FGF19) and 7alpha-hydroxy-4-cholesten-3-one (C4) to colesevelam did not differ between carriers of -203A and -203C alleles; their data were then aggregated for further analysis. Colesevelam treatment caused immediate suppression of FGF19 concentration and a fivefold increase in CYP7A1 activity, as assessed from C4 concentration, followed by a 17 % decrease in LDL-cholesterol. Although total plasma BA concentrations were not affected, the ratio of cholic acid/total BA rose from 0.25+/-0.10 to 0.44+/-0.16 during treatment at the expense of decreases in chenodeoxycholic and deoxycholic acid.

• MeSH
• alely MeSH
• cholagoga a choleretika farmakologie   MeSH
• cholestenony krev   MeSH
• cholesterol-7-alfa-hydroxylasa genetika   metabolismus   MeSH
• dospělí MeSH
• fibroblastové růstové faktory metabolismus   MeSH
• genotyp MeSH
• hormony štítné žlázy metabolismus   MeSH
• kolesevelam farmakologie   MeSH
• krevní glukóza metabolismus   MeSH
• LDL-cholesterol krev   MeSH
• lidé středního věku MeSH
• lidé MeSH
• metabolismus lipidů účinky léků   MeSH
• pilotní projekty MeSH
• polymorfismus genetický MeSH
• zdraví dobrovolníci pro lékařské studie MeSH
• žlučové kyseliny a soli metabolismus   MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

In clinical part of the study the hypothesis that hypercholesterolemic patients - carriers of -203C variant in cholesterol 7alpha-hydroxylase (CYP7A1) gene respond to 4-week therapy with bile acid sequestrant by more pronounced decrease in cholesterolemia than -203A variant carriers will be tested. The dynamics of changes in concentration of cholesterol, lipoproteins, glucose and factors affecting insulin sensitivity induced by changes in bile acid metabolism after sequestrant administration will be studied in healthy volunteers. It will be also analyzed how the changes in bile acid metabolism affect glucoregulation and thyroid function. In molecular biology part of the project the dual luciferase assay will be used to analyze in detail the role of particular polymorphisms in promoter region and first intron of CYP7A1 gene (polymorphisms being in tight linkage disequilibrium with -203A/C polymorphism) in regulation of cholesterol-7alpha-hydroxylase gene expression.

V klinické části projektu bude testována hypotéza, že hypercholesterolemičtí pacienti - nositelé varianty -203C v genu kódujícím cholesterol-7alfa-hydroxylasu (CYP7A1) odpovídají na 4týdenní léčbu sekvestranty žlučových kyselin podstatně větším poklesem cholesterolémie než nositelé varianty -203A. Dynamika změn koncentrace cholesterolu, lipoproteinů, glukózy a faktorů ovlivňujících inzulínosenzitivitu indukovaných změnami v metabolismu žlučových kyselin po podání sekvestrantu bude studována u zdravých dobrovolníků. Dále bude analyzováno, jak změny v metabolismu žlučových kyselin ovlivní glykoregulaci a funkci štítné žlázy. V molekulárně biologické části projektu bude metodou duálního luciferasového stanovení detailně analyzována úloha polymorfismů v promotorové oblasti a 1. intronu genu kódujícího CYP7A1 v regulaci exprese cholesterol-7alfa-hydroxylasy.

• MeSH
• cholesterol-7-alfa-hydroxylasa MeSH
• cholesterol MeSH
• genetika MeSH
• inzulinová rezistence MeSH
• žlučové kyseliny a soli MeSH

• Konspekt
• Biochemie. Molekulární biologie. Biofyzika
• NLK Obory
• vnitřní lékařství
• biologie
• NLK Publikační typ
• závěrečné zprávy o řešení grantu IGA MZ ČR

AIM: To determine whether the promoter polymorphism -203A>C of cholesterol-7α-hydroxylase encoding gene (CYP7A1) affects diurnal variation in CYP7A1 enzyme activity. METHODS: The study included 16 healthy male volunteers - 8 homozygous for -203A and 8 homozygous for the -203C allele of CYP7A1. Three 15-hour examinations (from 7am to 10pm) were carried out for each of the participants: after one-day treatment with cholestyramine; after one-day treatment with chenodeoxycholic acid (CDCA); and a control examination without any treatment. The plasma concentration of 7α-hydroxy-4-cholesten-3-one (C4), a marker of CYP7A1 activity, was determined in all the experiments at 90-min intervals. RESULTS: CYP7A1 activity was up-regulated after treatment with cholestyramine and suppressed after treatment with CDCA. There were no differences between -203A and -203C allele carriers in the response of enzyme activity to both drugs. In the control experiment, -203A allele carriers displayed diurnal variation in enzyme activity, whereas CYP7A1 activity did not change in -203C allele carriers. These results were confirmed by modeling the dynamics of C4 using polynomial regression. CONCLUSION: The promoter polymorphism of the CYP7A1 gene has a pronounced impact on diurnal variation in CYP7A1 activity.

• MeSH
• aktivace enzymů MeSH
• cholestenony krev   MeSH
• cholesterol-7-alfa-hydroxylasa genetika   metabolismus   MeSH
• cholesterol krev   MeSH
• cirkadiánní rytmus fyziologie   MeSH
• dospělí MeSH
• lidé MeSH
• plocha pod křivkou MeSH
• polymorfismus genetický * MeSH
• promotorové oblasti (genetika) MeSH
• upregulace MeSH
• žlučové kyseliny a soli biosyntéza   MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

1. To compare the effectiveness of different drug forms of silymarin: standardized extract of silymarin (SS), micronized silymarin (MS) and silymarin in the form of phytosome (PS) on dyslipidemia and liver fat accumulation in a model of metabolic syndrome, in non-obese hereditary hypertriglyceridemic rats. The second aim of this study was to slightly uncover the silymarin action on enzymes and proteins involved in cholesterol metabolism and excretion. 2. Silymarin administered to hereditary hypertriglyceridemic rats as dietary supplements (1%) for 4 weeks significantly lowered the plasma levels of triglycerides, total cholesterol and markedly increased HDL cholesterol level. Western blot analyses showed significant increase in the protein expression of CYP7A1 and CYP4A and increase in protein expression of selected ABC transporters. Silymarin in the form of phytosome and micronized silymarin were more effective forms of silymarin. 3. These findings suggest that silymarin may favorably affect the metabolism of cholesterol and triglycerides in rats with metabolic syndrome. Raising HDL levels suggests potentially important anti-atherogenic effect of silymarin. The changes in expression of cytochromes P450 and ABC transporters involved in cholesterol metabolism and excretion could be partially responsible for the hypolipidemic effect of silymarin.

• MeSH
• ABC transportéry metabolismus   MeSH
• biologická dostupnost MeSH
• cholesterol-7-alfa-hydroxylasa metabolismus   MeSH
• cytochrom P450 CYP4A metabolismus   MeSH
• dyslipidemie krev   komplikace   farmakoterapie   MeSH
• játra účinky léků   enzymologie   MeSH
• lipidy krev   MeSH
• metabolický syndrom krev   komplikace   farmakoterapie   MeSH
• potkani Wistar MeSH
• silymarin farmakologie   terapeutické užití   MeSH
• western blotting MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Epigallocatechin gallate (EGCG) has been shown to be protective in various experimental models of liver injury, although opposite effects have also been reported. Since its effect on biliary physiology has not been thoroughly investigated, the present study evaluated effect of EGCG on bile flow and bile acid homeostasis in rats. Compared to controls, EGCG treatment decreased bile flow by 23%. Hepatic paracellular permeability and biliary bile acid excretion were not altered by EGCG administration, but biliary glutathione excretion was reduced by 70%. Accordingly, the main glutathione transporter on the hepatocyte canalicular membrane, multidrug resistance-associated protein 2 (Mrp2), was significantly decreased at the protein level. EGCG administration also doubled plasma bile acid levels compared to controls. While protein levels of the main hepatic bile acid transporters were unchanged, the rate-limiting enzyme in the bile acid synthesis, Cyp7a1, was significantly increased by EGCG. Enhanced bile acid synthesis in these animals was also confirmed by a 2-fold increase in plasma marker 7α-hydroxy-4-cholesten-3-one. In contrast, EGCG markedly downregulated major bile acid transporters (Asbt and Ostα) and regulatory molecules (Shp and Fgf15) in the ileum. When EGCG was coadministered with ethinylestradiol, a potent cholestatic agent, it did not show any additional effect on the induced cholestasis. This study shows ability of EGCG to raise plasma bile acid concentrations, mainly through Cyp7a1 upregulation, and to decrease bile production through reduction in Mrp2-mediated bile acid-independent bile flow. In conclusion, our data demonstrate that under certain conditions EGCG may induce cholestasis.

• MeSH
• ABC transportéry genetika   MeSH
• cholestáza chemicky indukované   MeSH
• cholestenony metabolismus   MeSH
• cholesterol-7-alfa-hydroxylasa genetika   metabolismus   MeSH
• down regulace účinky léků   MeSH
• ethinylestradiol farmakologie   MeSH
• glutathion metabolismus   MeSH
• hepatocyty účinky léků   metabolismus   MeSH
• homeostáza účinky léků   MeSH
• ileum účinky léků   metabolismus   MeSH
• katechin analogy a deriváty   toxicita   MeSH
• krysa rodu rattus MeSH
• permeabilita MeSH
• potkani Wistar MeSH
• upregulace účinky léků   MeSH
• žlučové kyseliny a soli biosyntéza   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Cholesterol 7?-hydroxylase (CYP7A1), the key regulatory enzyme of bile acid synthesis, displays a pronounced diurnal variation. To better understand the regulation of CYP7A1 activity, three daylong examinations were carried out in 12 healthy men. The concentrations of 7?-hydroxycholest-4-en-3-one (C4), a surrogate marker of CYP7A1 activity, bile acids (BA), insulin, glucose, nonesterified fatty acids, triglycerides, and cholesterol were measured in serum in 90-min intervals from 7 AM till 10 PM. To lower and to increase BA concentration during the study, the subjects received cholestyramine and chenodeoxycholic acid (CDCA), respectively, in two examinations. No drug was used in the control examination. There was a pronounced diurnal variation of C4 concentration with a peak around 1 PM in most of the subjects. The area under the curve (AUC) of C4 concentration was five times higher and three times lower when subjects were treated with cholestyramine and CDCA, respectively. No relationship was found between AUC of C4 and AUC of BA concentration, but AUC of C4 correlated positively with that of insulin. Moreover, short-term treatment with cholestyramine resulted in about 10 % suppression of glycemia throughout the day. Our results suggest that insulin is involved in the regulation of diurnal variation of CYP7A1 activity in humans.

• MeSH
• aktivace enzymů MeSH
• anticholesteremika aplikace a dávkování   MeSH
• cholestenony krev   MeSH
• cholesterol-7-alfa-hydroxylasa metabolismus   MeSH
• cholesterol krev   MeSH
• cholestyraminová pryskyřice aplikace a dávkování   MeSH
• cirkadiánní rytmus fyziologie   MeSH
• dospělí MeSH
• financování organizované MeSH
• gastrointestinální látky aplikace a dávkování   MeSH
• inzulin krev   MeSH
• klinické zkoušky jako téma MeSH
• krevní glukóza metabolismus   MeSH
• kyselina chenodeoxycholová metabolismus   MeSH
• kyseliny mastné neesterifikované krev   MeSH
• lidé MeSH
• referenční hodnoty MeSH
• triglyceridy krev   MeSH
• žlučové kyseliny a soli metabolismus   MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH

Response to hypolipidemic treatment is genetically regulated. We will study decreases of plasma lipids depending on candidate genes for apo E, A1 and A5, cytochrome P4503A4, hepatic lipase, cholesterol 7alfa hydroxylase and ABC -G8 and -A1 transporters.

Odpověď na léčbu hypolipidemiky je regulována i geneticky. Budeme sledovat pokles lipidových parametrů v závislosti na genech pro apolipoproteiny E, A1 a A5, pro cytochrom P4503A4, jaterní lipázu, cholesterol 7alfa hydroxylázu a ABC transportéry G8 a A1.

• MeSH
• ABC transportéry MeSH
• apolipoproteiny A MeSH
• apolipoproteiny E MeSH
• ateroskleróza farmakoterapie   MeSH
• cholesterol-7-alfa-hydroxylasa MeSH
• dyslipidemie farmakoterapie   MeSH
• genotyp MeSH
• hypolipidemika terapeutické užití   MeSH
• imunologická odpověď na dávku MeSH
• lipoproteinlipasa MeSH
• polymorfismus genetický MeSH
• statiny MeSH
• systém (enzymů) cytochromů P-450 MeSH
• výsledek terapie MeSH

• Konspekt
• Biochemie. Molekulární biologie. Biofyzika
• NLK Obory
• vnitřní lékařství
• biologie
• NLK Publikační typ
• závěrečné zprávy o řešení grantu IGA MZ ČR

Snížení vysokých hladin plazmatického cholesterolu a triglyceridů je velice důležité v prevenci a léčbě kardiovaskulárních onemocnění. U většiny jedinců je léčba změnou životního stylu (úpravou dietních zvyklostí a zvýšenou fyzickou aktivitou) nedostatečná a je nutné přistoupit k farmakologické terapii. Statiny, inhibitory enzymu 3-hydroxy-3-methylglutaryl koenzym- A reduktázy, jsou dobře tolerovaným lékem první volby u pacientů s dyslipidémií. U různých pacientů s identickou terapií je ale prokázána velká variabilita účinku statinů a zdá se, že příčinou je především odlišná genetická predispozice každého jedince. Regulace odpovědi na hypolipidemickou léčbu je pod polygenní kontrolou. Analýza kombinací variant účastněných genů může pomoci detekovat existenci „hyper-“ a „hypo-“ responderů, tj. jedinců, kteří na léčbu reagují dobře (a je možno začít s nižší dávkou medikamentu), nebo špatně či vůbec (zde nebude statin lékem první volby), případně může napomoci identifi kovat nemocné náchylné k nežádoucím vedlejším účinkům. Mezi geny s popsaným efektem na účinnost farmakologické léčby hyperlipidemií patří mimojiné geny pro cytochromy, apolipoproteiny E a A1 a cholesterol 7-? hydroxylázu.

Reduction of high plasma levels of cholesterol and triglycerides is one of the most important steps in the prevention and treatment of cardiovascular disease. In most cases, changes in lifestyle (improvement of diet, increased physical activity) are not suffi cient and it is necessary to initiate pharmacological treatment. Statins, inhibitors of 3-hydroxy-3- -methylglutaryl coenzyme-A reductase are well-tolerated drugs of choice in hyperlipidaemic patients. Nevertheless, the effect of statins substantially differs between individuals and it is clear that these differences are caused mostly by the genetic predisposition. The regulation of statin effi cacy is defi nitely under polygenic control. Detailed analysis of gene- -gene interaction could help to detect „hyper-“ and „hypo-“ responders – individuals, who respond well to the treatment (and therefore lower drug doses can be used), or those who respond poorly (then statin would not be the drug of fi rst choice). Also patients susceptible to side effects can be identifi ed. There are several studies showing that some genes (and their variants) (e.g. genes coding for cytochromes, apolipoproteins E and A1, and cholesterol 7-? hydroxylase) are important genetic determinants of statin treatment effi cacy.

• MeSH
• apolipoprotein A-I genetika   účinky léků   MeSH
• cholesterol-7-alfa-hydroxylasa genetika   účinky léků   MeSH
• dyslipidemie farmakoterapie   komplikace   MeSH
• farmakogenetika metody   normy   trendy   MeSH
• financování organizované MeSH
• lidé MeSH
• medicína založená na důkazech trendy   MeSH
• nežádoucí účinky léčiv komplikace   prevence a kontrola   MeSH
• polymorfismus genetický genetika   účinky léků   MeSH
• statiny farmakokinetika   farmakologie   terapeutické užití   MeSH
• systém (enzymů) cytochromů P-450 farmakologie   MeSH
• Check Tag
• lidé MeSH
• Geografické názvy
• Česká republika MeSH

Circadian variation in cholesterol 7alpha-hydroxylase (CYP7A1) activity will be studied in healthy volunteers homozygous either for -204A or -204C variant in CYP7A1 gene promoter. Circadian variation in CYP7A1 activity will be studied under basal conditions and after stimulation and inhibition of CYP7A1 gene expression using drugs (colestipol and chenodeoxycholic acid, respectively). The activity of both CYP7A1 gene promoter variants will be studied in vitro using dual lucipherase assay both under basalconditions and after stimulation.

Cirkadiánní variace v aktivitě cholesterol 7alfa-hydroxylázy (CYP7A1) bude studována u zdravých dobrovolníků homozygotních pro variantu -204A nebo -204C v promotoru genu pro CYP7A1. Cirkadiánní variace v aktivitě CYP7A1 bude studována za bazálních podmínek a po stimulaci nebo inhibici exprese genu pro CYP7A1 pomocí léků (colestipolu a kyseliny chenodeoxycholové). Aktivita obou variant promotoru genu pro CYP7A1 bude studována in vitro technikou duální luciferázové eseje jak za bazálních podmínek, tak postimulaci.

• MeSH
• cholesterol-7-alfa-hydroxylasa MeSH
• chronobiologické poruchy MeSH
• LDL-cholesterol MeSH
• polymorfismus genetický MeSH

• Konspekt
• Biochemie. Molekulární biologie. Biofyzika
• NLK Obory
• biologie
• vnitřní lékařství
• NLK Publikační typ
• závěrečné zprávy o řešení grantu IGA MZ ČR