<p>Interindividualne razlike u sastavu i aktivnosti crevne mikroflore mogu uticati na metabolizam lekova kao i na njihov konačan terapijski odgovor. Simvastatin je lek iz grupe statina i karakteri&scaron;e ga izuzetno mala rastvorljivost u vodi, mala bioraspoloživost (&lt;5%) i velike interindividualne razlike u terapijskom odgovoru čiji uzroci nisu u potpunosti obja&scaron;njeni. Poslednjih godina velika pažnja se posvećuje ispitivanjima žučnih kiselina u razvoju novih farmaceutskih formulacija zbog svoje uloge u solubilizaciji i modifikaciji prodora lekova kroz biolo&scaron;ke membrane. Zbog svega navedenog, u fokusu na&scaron;eg istraživanja su bile potencijalne interakcije između simvastatina, probiotskih bakterija i žučnih kiselina o kojima se vrlo malo zna, a od izuzetne su važnosti, zbog mogućeg uticaja na farmakokinetske i farmakodinamske osobine simvastatina, pa samim tim i na konačan terapijski odgovor kod pacijenta.Cilj istraživanja je bio da se ispita prodor i metabolizam simvastatina u probiotskim bakterijama kao i uticaj različitih žučnih kiselina na transport ovog leka u bakterijske ćelije. Takođe, cilj je bio da se ispita uticaj soli žučnih kiselina na distribucioni koeficijent simvastatina, kao i interakcije žučnih kiselina sa simvastatinom na nivou transportnih proteina probiotskih bakterija kako bi se objasnila priroda očekivanih interakcija.Identifikacija i kvantifikacija uzoraka vr&scaron;ena je metodom tečne hromatografije sa masenom spektrometrijom (LC-MS/MS). Kori&scaron;ćenjem programskih paketa VolSurf+ i Molinspiration, za identifikovane metabolite su izračunati molekulski deskriptori koji opisuju fizičko-hemijske i farmakokinetske osobine molekula. Određivanje distribucionog koeficijenta vr&scaron;eno je Shake-flask metodom. Interakcije žučnih kiselina sa simvastatinom na nivou transportnih proteina probiotskih bakterija ispitane su doking studijama pomoću SwissDock programa. Prilikom dvadesetčetvoročasovne inkubacije sa probiotskim bakterijama uočen je statistički značajan pad koncentracije simvastatina u ekstracelularnom sadržaju. Ukupan sadržaj simvastatina, kao zbir ekstracelulamog i intracelularnog sadržaja, je tokom čitavog ispitivanog perioda bio statistički značajno niži u odnosu na kontrolnu grupu bez probiotika navodeći na zaključak da se deo simvastatina tokom vremena metabolisao pod dejstvom enzima ispitivanih bakterija. Detektovano je i identifikovano 8 metaboličkih produkata simvastatina. Na osnovu izračunatih vrednosti molekulskih deskriptora, očekuje se da će metabolit M-452, koji predstavlja hidroksilovani produkt simvastatinske kiseline, pokazati najbolje rezultate u pogledu fizičko-hemijskih osobina i bioraspoloživosti u biolo&scaron;kom sistemu. Žučne kiseline nisu dovele do statistički značajne modifikacije transporta simvastatina u/iz probiotskih bakterija. Ipak, u nekim vremenskim tačkama primećena je ne&scaron;to veća koncentracija leka u ekstracelulamom prostoru u grupama sa žučnim kiselinama. Ove razlike se mogu delimično objasniti rezultatima određivanja distribucionog koeficijenta koji su pokazali da ispitivane žučne kiseline dovode do statistički značajnog smanjenja distribucionog koeficijenta simvastatina usled povećanja rastvorljivosti u vodenoj fazi. Rezultatima doking studija procenjeno je da ispitivane žučne kiseline imaju veći afinitet prema čak 80% multidrug transportera ispitivanih bakterija u odnosu na simvastatin &scaron;to govori o mogućnosti ostvarivanja interakcija žučnih kiselina sa ovim lekom na nivou transportnih proteina probiotskih bakterija. Na osnovu dobijenih rezultata možemo zaključiti da probiotske bakterije imaju ogroman uticaj na sudbinu simvastatina u biolo&scaron;kom sistemu. Uzimajući u obzir činjenicu da probiotske bakterije ulaze u sastav normalne crevne flore i da svaki organizam poseduje specifičan bakterijski sastav, trebalo bi posvetiti vi&scaron;e pažnje ispitivanju njegovog uticaja na farmakokinetiku lekova. Neophodna su dalja in vivo ispitivanja kako bi se utvrdila potencijalna farmakolo&scaron;ka aktivnost identifikovanih metabolita simvastatina nastalih pod dejstvom enzimske aktivnosti probiotskih bakterija. Povećanje rastvorljivosti simvastatina pomoću žučnih kiselina otvara mogućnost za dalja istraživanja u cilju razvoja novih farmaceutskih formulacija sa pobolj&scaron;anom bioraspoloživosti i farmakokinetskim osobinama.</p> / <p>Interindividual differences in the composition and activity of the gut microflora may affect the metabolism of drugs as well as their final therapeutic response. Simvastatin is drug from the group of statins and has extremely low water solubility, low bioavailability (&lt;5%) and high interindividual differences in therapeutic response whose causes are not fully understood. In recent years, great attention has been paid to studies of bile acids in the development of new pharmaceutical formulations because of their role in the drug solubilization and modification of drug transport through biological membranes. Accordingly, interactions between simvastatin, probiotic bacteria and bile acids were the focus of our research due to great importance and potential influence on the pharmacokinetic and pharmacodynamic properties of simvastatin, and therefore the final therapeutic response in the patients. The aim of the study was to investigate the simvastatin transport and metabolism in probiotic bacteria as well as the effect of various bile acids on drug transport into the bacterial cell. Additonally, the aim was to investigate the influence of bile salts on the distribution coefficient of simvastatin, and the interactions of bile acids with simvastatin at the level of probiotic transport proteins in order to elucidate the nature of expected interactions. Identification and quantification of samples were performed with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Molecular descriptors that describe the physico-chemical and pharmacokinetic properties of identified metabolites were calculated using the software packages VolSurf+ and Molinspiration. Determination of the distribution coefficient was performed using Shake-flask method. Interaction of bile acids with simvastatin at the level of bacterial transport proteins were studied using docking studies with SwissDock program. During the twenty-four hours of incubation with probiotic bacteria, simvastatin concentrations in the extracellular contet showed a statistically significant decrease. The total amount of simvastatin, as the sum of the extracellular and intracellular amount, during the whole study period, was significantly lower in comparison with control group without probiotics, suggesting that the part of simvastatin was metabolized by the enzymatic activity of studied bacteria. Accordingly, eight metabolic products of simvastatin were detected and identified. Based on the calculated values of molecular descriptors, it is expected that the metabolite M-452, which is the hydroxylated product of simvastatin acid, will show the best results in terms of physico-chemical properties and bioavailability in biological system. Bile acids did not show a significant influence on simvastatin transport into probiotic bacteria. However, in some time points, slightly higher drug concentrations in the extracellular medium in groups with bile acids were observed. These differences can be partly explained by the results of the determination of the distribution coefficients which showed that investigated bile acids lead to a statistically significant decrease in simvastatin distribution coefficient due to increased solubility in the aqueous phase. The results of docking studies estimated that studied bile acids have stronger affinities for the 80% of bacterial multidrug transporters compared to simvastatin indicating the possibility of achieving the interactions of bile acids with simvastatin at the level of transport proteins of probiotic bacteria. Based on the obtained results it could be concluded that probiotic bacteria have great influence on the fate of simvastatin in a biological system. Taking into account the fact that probiotic bacteria are the normal part of gut microflora and that each individual has specific bacterial fingerprint, more attention should be paid on studying its influence on drug pharmakocinetics. Further in vivo studies are required in order to determine potential pharmacological activity of identified simvastatin metabolites. Increased water solubility of simvastatin with bile acids may open the possibility for further investigations with the aim of development of new pharmaceutical formulation with improved bioavailability and pharmacokinetic properties.</p>

Le récepteur X des farnésoïdes (FXR) fait partie de la superfamille des récepteurs nucléaires et agit comme un facteur de transcription suite à la liaison d’un ligand spécifique. Le récepteur FXR, activé par les acides biliaires, joue un rôle essentiel dans le métabolisme des lipides et du glucose en plus de réguler l’homéostasie des acides biliaires. Notre laboratoire a récemment mis en évidence une nouvelle voie de régulation du récepteur PPARγ en réponse au récepteur de la ghréline. En effet, la ghréline induit l’activation transcriptionnelle de PPARγ via une cascade de signalisation impliquant les kinases Erk1/2 et Akt, supportant un rôle périphérique de la ghréline dans les pathologies associées au syndrome métabolique. Il est de plus en plus reconnu que la cascade métabolique impliquant PPARγ fait également intervenir un autre récepteur nucléaire, FXR. Dans ce travail, nous montrons que la ghréline induit l’activation transcriptionnelle de FXR de manière dose-dépendante et induit également la phosphorylation du récepteur sur ses résidus sérine. En utilisant des constructions tronquées ABC et CDEF de FXR, nous avons démontré que la ghréline régule l’activité de FXR via les domaines d’activation AF-1 et AF-2. L’effet de la ghréline et du ligand sélectif GW4064 sur l’induction de FXR est additif. De plus, nous avons démontré que FXR est la cible d’une autre modification post-traductionnelle, soit la sumoylation. En effet, FXR est un substrat cellulaire des protéines SUMO-1 et SUMO-3 et la sumoylation du récepteur est ligand-indépendante. SUMO-1 et SUMO-3 induisent l’activation transcriptionnelle de FXR de façon dose-dépendante. Nos résultats indiquent que la lysine 122 est le site prédominant de sumoylation par SUMO-1, quoiqu’un mécanisme de coopération semble exister entre les différents sites de sumoylation de FXR. Avec son rôle émergeant dans plusieurs voies du métabolisme lipidique, l’identification de modulateurs de FXR s’avère être une approche fort prometteuse pour faire face à plusieurs pathologies associées au syndrome métabolique et au diabète de type 2. / The farnesoid X receptor (FXR) is a ligand-activated transcription factor within the nuclear receptor superfamily. FXR is activated by bile acids and plays a crucial role in the regulation of glucose and lipid metabolism and in bile acid homeostasis. Our group has recently identified the contribution of the ghrelin receptor in the regulation of the nuclear receptor PPARγ. Indeed, ghrelin triggers transcriptional activation of PPARγ through a concerted signaling cascade involving Erk1/2 and Akt kinases. These results support the peripheral actions of ghrelin in diseases associated with the metabolic syndrome. It is recognized that there is interplay between PPARγ metabolic cascade and FXR. Here, we demonstrate that ghrelin promotes FXR transcriptional activity in a dose-dependent manner and also promotes its phosphorylation on serine residues. By using truncated ABC and CDEF constructs of FXR, we found that ghrelin induces FXR activity through the AF-1 and AF-2 activation domains. The ghrelin-induced FXR activity is additive to the induction by the selective agonist GW4064. Also, we demonstrate that FXR is the target of sumoylation, another post-translational modification. In particular, FXR is modified by SUMO-1 and SUMO-3 in a ligand-independent manner. SUMO-1 and SUMO-3 promote dose-dependent transcriptional activity of FXR. Our results show that lysine 122 is the prevalent site of sumoylation by SUMO-1, though a compensation mechanism seems to exist between the various sumoylation sites of FXR. With its emerging role in several metabolic cascades, identification of FXR modulators represents a promising approach for the treatment of the metabolic syndrome and type 2 diabetes.

The electrochemic's behaviour of the bile acids (cholic, glycocholic, deoxycholic, ursodeoxycholic and lithocholic acid) was studied on the meniscus-modified silver solid amalgam electrode (m-AgSAE) by differential pulse voltammery. Bile acids provide in the solution of the Britton - Robinson buffer and methanol (9:1) in the pH range 3.0 to 12.0 a cathodal signal in the high negative potentials: cholic acid, deoxycholic acid, ursodeoxycholic acid and lithocholic acid about −1400 mV and glycocholic acid, which alone is the conjugate with glycine, about −1500 mV. Cholic acid, glycocholic acid, deoxycholic acid and ursodeoxycholic acid provide the highest peaks to pH 5.0, approximately in their pKa values. Lithocholic acid provides peaks from pH 7.0. It was demonstrated by the cyclic voltammetry that the electrochemical behavior is influenced by the adsorption of the bile acids to the electrode; presumed reaction at the working electrode - a reduction of a proton of a carboxylic group, is controlled by the diffusion and the process is quasireversible. Utilization of the electrochemical reduction of bile acids for the voltammetric determination does not seem very suitable. It has been proven that the presence of the methanol deteriorates the measuring results for glycocholic acid. In the presence of...

Author: Nikola Jozefčeková Title: Endoglin and liver Form: Diploma Thesis University: Charles University, Faculty of Pharmacy in Hradec Králové Degree: Pharmacy This diploma thesis concludes the available information about endoglin, its isoforms in the liver and its impact on the liver during various pathological conditions. In the first part of the thesis describes morphology and physiology of the liver, its structure, histology and metabolic functions. Second part contains an information about endoglin, its isoforms and role in TGF-β signaling complex, expression of endoglin and regulation of the expression. In the third part are described liver diseases during which is expression of endoglin changed. This part deals with the significance of endoglin as a diagnostic and prognostic marker. Endoglin (CD105, TGF-β receptor III) is a homodimeric transmembrane glycoprotein and a membrane co-receptor TGF-β with high expression in endothelial cells. Endoglin plays an important role in the vascular development. Endoglin is involved in the processes of angiogenesis, vascular homeostasis and TGF-β signalization. It affects activity of TGF-βRII, ALK1 and ALK5 receptors. Due to the interactions with TGF-β complex, modulation of activity of ALK receptors and Smads, endoglin controls fibrotic and anti-...

<p>Zahvaljujući amfifilnoj strukturi i mogućnosti građenja konjugata, žučne kiseline - endogeno sintetisani produkti katabolizma holesterola su prepoznate kao potencijalni nosači lekova i promoteri transporta kroz biolo&scaron;ke membrane. Otkriće da aktivacijom specifičnih nuklearnih receptora reguli&scaron;u ekspresiju gena uključenih u plejadu signalnih puteva uključenih u metabolizam, proliferaciju i diferencijaciju ćelija i onkogenezu, pro&scaron;irilo je ulogu žučnih kiselina u odnosu na inicijalno opisanu ulogu intestinalnih emulgatora. Žučne kiseline se danas ne smatraju samo pasivnim nosačima lekova i promoterima transporta kroz biolo&scaron;ke membrane već i molekulima sa farmakodinamskom funkcijom, koji reguli&scaron;u različite aspekte integrativnog ćelijskog metabolizma. Doksorubicin je jedan od najče&scaron;će kori&scaron;ćenih antineoplastičkih agenasa i sastavna je komponenta mnogih hemoterapijskih protokola u lečenju solidnih i hematolo&scaron;kih maligniteta. Međutim, hepatotoksični i kardiotoksični efekti značajno ograničavaju upotrebu ovog, inače veoma korisnog antitumorskog agensa. Pojava odložene dozno-zavisne kardiotoksičnosti predstavlja značajan zdravstveni problem onkolo&scaron;kih pacijenata sa uspe&scaron;no lečenim malignitetom, naročito pacijenata lečenih u pedijatrijskom uzrastu. Budući da je razvoj novih lekova veoma dug i skup proces sa neizvesnim ishodom, pobolj&scaron;anje farmakodinamskih i farmakokinetskih svojstava već postojećih antitumorskih agenasa sa dokazanom efikasno&scaron;ću, uz smanjenje toksičnih efekata, predstavlja racionalan istraživački pristup u savremenoj medicini. Osnovni cilj ovog rada je ispitivanje uticaja žučnih kiselina ursodeoksiholne, henodeoksiholne i 12-okso-henodeoksiholne kiseline (12-monoketoholne kiseline) na citotoksičnu aktivnost doksorubicina prema MCF-7 ćelijskoj liniji humanog adenokarcinoma dojke i ispitivanje molekularnih mehanizama odgovornih za farmakodinamske efekte. Takođe su navedene žučne kiseline ispitane kao promoteri transporta koji utiči na prodor i kumulaciju doksorubicina u malignim ćelijama. U ovom radu je ispitan uticaj koadministracije navedenih žučnih kiselina sa doksorubicinom na odložene toksodinamske efekte (hepatotoksičnost i kardiotoksičnost) kod pacova, ali i efekti pretretmana žučnim kiselinama na koncentracije doksorubicina u krvi, bilijarnu ekskreciju leka kao i kumulaciju u jetri i miokardu eksperimentalnih životinja. Žučne kiseline su u netoksičnim koncentracijama potencirale in vitro citotoksične efekte doksorubicina na MCF-7 ćelijskoj liniji pri čemu je henodeoksiholna ispoljila sinergistički efekt, dok su ursodeoksiholna u 12-monoketoholna ispoljile aditivni citotoksični efekt sa doksorubicinom. Ispitivanjem molekularnih mehanizama citotoksičnih efekata utvrđeno je da su žučne kiseline u različitom stepenu potencirale apoptozu ćelija mitohondrijalnim putem uticajem na ekspresiju pro- i antiapoptotskih proteina na transkripcionom nivou i povećale stres endoplazmatskog retikuluma, ali i dovele do alteracija ekspresije gena koji kodiraju sintezu antioksidativnih enzima, transmembranskih efluks proteina i enzima uključenih u metaboličku inaktivaciju leka. Žučne kiseline u netoksičnim koncentracijama su takođe značajno povećale prodor i kumulaciju doksorubicina u MCF-7 ćelijskoj liniji. U in vivo sistemu, koadministracija žučnih kiselina nije rezultovala u pobolj&scaron;anju odloženih toksodinamskih efekata visokih doza doksorubicina na biohemijskom i molekularnom nivou. Međutim, nakon pretretmana žučnim kiselinama, vrednosti koncetracija doksorubicina u serumu su bile povi&scaron;ene nakon pretretmana urso- i henodeoksiholnom kiselinom i snižene nakon pretretmana 12-monoketoholnom kiselinom uz povećanje bilijarne sekrecije doksorubicina. Pored promena u farmakokinetskom profilu doksorubicina, pretretman žučnim kiselinama je blago redukovao prodor i kumulaciju doksorubicina u hepatocite i kardiomiocite. Na osnovu rezultata ove studije može se zaključiti da primena ispitivanih žučnih kiselina sa doksorubicinom povećava prodor i pobolj&scaron;ava farmakodinamski profil doksorubicina in vitro, na ćelijskom modelu humanog adenokarcinoma dojke. Pobolj&scaron;anje selektivnog preuzimanja i prodora doksorubicina u maligne ćelije koje nije praćeno povećanom kumulacijom u normalnim tkivima, kao i pobolj&scaron;anje antitumorskog dejstva doksorubicina sa mogućim smanjenjem doze uz smanjenje pojave dozno-zavisnih neželjenih dejstava doksorubicina čini žučne kiseline molekulima kandidatima za dalja ispitivanja u cilju razvoja novih, pobolj&scaron;anih antitumorskih terapijskih strategija.</p> / <p>Due to the amphiphilic structure and the significant conjugation potential, bile acids - endogenously synthesized products of cholesterol catabolism have been recognized as potential drug carriers and promoters of transport through biological membranes. The discovery that by activating specific nuclear receptors bile acids regulate the expression of genes involved in various signaling pathways including metabolism, cell proliferation and differentiation as well as carcinogenesis, expanded initially ascribed role of intestinal emulsifiers to the various fields. Bile acids are now considered not to act only as passive carriers of drugs and promoters of transport through biological membranes, but also as the molecules with pharmacodynamic activity, regulating various aspects of integrative cellular metabolism. Doxorubicin is one of the most commonly prescribed antineoplastic agents as an integral component of many chemotherapy protocols in the treatment of both solid and hematologic malignancies. However, hepatotoxic and cardiotoxic effects significantly limit the use of this, otherwise, very useful anti-tumor agent. The development of dose-dependent cardiotoxic side effects represents particular health issue in successfully treated oncological patients, especially among survivors of pediatric malignancies. Since the development of new drugs is very long and expensive process with an uncertain outcome, improving the pharmacodynamic and pharmacokinetic properties of the existing agents with proven efficacy, while reducing toxic side effects, represents a rational approach to research in modern medicine. The main objective of this work is to examine the role of bile acids: ursodeoxycholic, chenodeoxycholic and 12-oxo-chenodeoxycholic acid (12-monoketocholic acid) on the cytotoxic activity of doxorubicin in the MCF-7 human breast adenocarcinoma cell line, and to get insight on molecular mechanisms responsible for underlying pharmacodynamic effects. The capacity of bile acids to promote the transport and accumulation of doxorubicin in malignant cells was also evaluated. In addition, the effect of co-administration of the bile acids with doxorubicin on delayed toxodynamic effects (hepatotoxicity and cardiotoxicity) in rats, as well as the effects of bile acid pretreatment on the doxorubicin serum concentration and pharmacokinetic profile, biliary excretion of the drug as well as accumulation in the liver and myocardial cells of experimental animals were examined. Bile acids applied in non-toxic concentrations potentiated in vitro cytotoxic effects of doxorubicin in MCF-7 cell line. Chenodeoxycholic acid exhibited a synergistic effect, whereas ursodeoxycholic and 12-monoketocholic acid exhibited an additive cytotoxic effect with doxorubicin. By examining the underlying molecular mechanisms of cytotoxic effects, bile acids have been found to potentiate apoptosis of cells by mitochondrial-dependent pathway by modifying the expression of pro- and anti-apoptotic proteins at the transcriptional level and to increase endoplasmic reticulum stress, but also have altered the expression of genes encoding the synthesis of antioxidant enzymes, transmembrane efflux proteins and enzymes involved in metabolic inactivation of the drug. Non-toxic concentrations of bile acids also significantly increased the penetration and accumulation of doxorubicin in MCF-7 cell line. In the in vivo system, the co-administration of bile acid did not improved delayed toxodynamic effects of high dose of doxorubicin both at the biochemical and molecular levels. However, pretreatment with bile acids resulted in alterations of serum doxorubicin concentrations. Chenodeoxycholic and ursodeoxycholic acid elevated whereas 12-monoketocholic acid decreased serum doxorubicin concentrations. In addition to changing pharmacokinetic profile of doxorubicin on bile acid species-dependent manner, all bile acids have also increased excretion of drug by the biliary route, and slightly reduced penetration and accumulation of doxorubicin in hepatocytes and cardiomyocytes. Based on the results of this study, the administration of the examined bile acids with doxorubicin increases the penetration and improves the pharmacodynamic profile of doxorubicin in vitro on the cell model of human breast adenocarcinoma. The improvement of selective uptake and penetration of doxorubicin into malignant cells that is not accompanied by increased accumulation in normal tissues, as well as the improvement in the anti-tumor effects of doxorubicin with a possibility to reduce the dose and thereby the occurrence of dose-dependent undesirable effects of doxorubicin, render bile acids as the potential candidate molecules in developing novel antitumor therapeutic strategies.</p>

<p>Žučne kiseline deluju kao signalni molekuli u organizmu i uključene su u regulaciju brojnih metaboličkih, inflamatornih i imunomodulatornih procesa. Ova endogena jedinjenja ostvaruju svoje efekte najvećim delom putem nuklearnih receptora. Farnezoid X receptor (FXR) je glavni regulator homeostaze žučnih kiselina, a pokazano je da je značajno uključen i u procese inflamacije i kancerogeneze, prevashodno u jetri i intestinalnom traktu. Aktivacija FXR receptora predstavlja značajnu farmakolo&scaron;ku strategiju za terapiju holestatskih bolesti jetre, inflamatorne bolesti creva i karcinoma kolona. Definisana je uloga žučnih kiselina u signalnim putevima koji reguli&scaron;u ćelijski ciklus i doprinose razvoju ili regresiji maligniteta, ali je malo poznat uticaj ovih jedinjenja na epigenetske mehanizme regulacije ključnih ćelijskih procesa. Imajući u vidu da su efekti žučnih kiselina determinisani njihovom polarno&scaron;ću, cilj istraživanja je bio da se ispita uticaj sintetski dobijenog keto derivata holne kiseline, 12-monoketoholne kiseline (MKH), u komparaciji sa prirodnim žučnim kiselinama, hidrofobnom henodeoksiholnom kiselinom (HDH) i hidrofilnom ursodeoksiholnom kiselinom (UDH), na ćelijske procese apoptoze, oksidativnog stresa i inflamacije, koji su od značaja za hemoprevenciju i terapiju karcinoma kolona, u in vitro i in vivo sistemima. Cilj istraživanja je takođe obuhvatao i ispitivanje uloge odabranih žučnih kiselina u epigenetskoj regulaciji ovih procesa u ćelijama karcinoma kolona. Na in vivo modelu intrahepatične holestaze kod eksperimentalnih životinja, pokazano je da UDH i MKH ispoljavaju antiapoptotski, antioksidativni i antiinflamatorni efekat u jetri i intestinumu. Utvrđeno je da UDH i MKH sprečavaju mitohondrijalni put aktivacije apoptoze u jetri, dok UDH ispoljava antiapoptotski efekat i u intestinumu eksperimentalnih životinja sa holestazom. Ove dve žučne kiseline su u značajnoj meri modulirale ekspresiju gena uključenih u antioksidativnu za&scaron;titu, kao i aktivnost antioksidativnih enzima, u jetri i intestinumu eksperimentalnih životinja sa holestazom, ka nivoima ekspresije i aktivnosti kod zdravih, netretiranih životinja. Dok su UDH i MKH u dozi od 4 mg/kg ispoljile antiinflamatorno dejstvo u jetri i intestinumu smanjenjem ekspresije gena za proinflamatorni transkripcioni faktor NF-&kappa;B, primena HDH i MKH u dozi od 20 mg/kg je imala suprotan efekat. Na modelu HT-29 ćelijske linije adenokarcinoma kolona, utvrđeno je da polusintetska žučna kiselina MKH ispoljava značajno manju citotoksičnost u odnosu na HDH i ne&scaron;to veću citotoksičnost u odnosu na UDH. Epigenetski lek vorinostat je ispoljio sinergističko citotoksično dejstvo sa sve tri ispitivane žučne kiseline. Vorinostat je ostvario proapoptotski i antiproliferativni efekat u HT-29 ćelijama, koji je bio najizraženiji u kombinaciji sa MKH, s obzirom da je do&scaron;lo do značajnog povećanja odnosa ekspresije BAX i BCL2 gena i smanjenja ekspresije gena za marker proliferacije ciklin D1. Vorinostat je, takođe, značajno smanjio antioksidativni kapacitet HT-29 ćelija smanjenjem ekspresije NRF2 gena i sledstvenim smanjenjem ekspresije gena za antioksidativne enzime. HDH je dodatno smanjila, a MKH pobolj&scaron;ala antioksidativni kapacitet HT-29 ćelija modulacijom ekspresije NRF2 gena. U in vitro i in vivo sistemu u okviru ove doktorske disertacije je pokazano da, pored HDH kao poznatog endogenog agoniste FXR receptora, MKH takođe povećava ekspresiju gena za FXR i njegovog ciljnog gena za transkripcioni korepresor SHP, &scaron;to ukazuje da ova polusintetska žučna kiselina može da aktivira FXR. Osim toga, utvrđeno je da žučne kiseline ispoljavaju različite efekte prema ekspresiji gena za histon deacetilaze HDAC1 i HDAC2 u jetri i intestinumu eksperimentalnih životinja, kao i u HT-29 ćelijama karcinoma kolona, a jedino je UDH značajno smanjila ekspresiju gena za oba ispitivana enzima uključena u epigenetsku regulaciju ćelijskih procesa, i u isptivanim tkivima i HT-29 ćelijama. Rezultati na&scaron;eg rada ukazuju da bi se UDH i MKH mogle koristiti u hemoprevenciji karcinoma kolona u niskim dozama, s obzirom na utvrđene efekte u modulaciji ekspresije gena uključenih u procese apoptoze, oksidativnog stresa i inflamacije. Takođe, s obzirom na ostvaren sinergistički efekat žučnih kiselina sa epigenetskim antitumorskim agensom vorinostatom, otvara se mogućnost kombinovane farmakolo&scaron;ke strategije u terapiji solidnih tumora, koji u najvećem procentu pokazuju rezistenciju prema samom vorinostatu.</p> / <p>Bile acids act as signaling molecules in the organism and they are involved in the regulation of numerous metabolic, inflammatory and immunomodulatory processes. These endogenous compounds exert their effects mostly by binding and activation of nuclear receptors. Farnesoid X receptor (FXR) is the main regulator of bile acid homeostasis, and has been shown to be significantly involved in processes of inflammation and carcinogenesis, primarily in the liver and intestinal tract. Activation of FXR receptor represents a significant pharmacological strategy for the treatment of cholestatic liver disease, inflammatory bowel disease, and colon carcinoma. The role of bile acids in signaling pathways regulating the cell cycle and contributing to the development or regression of malignancies is well determined, but the effects of these compounds on epigenetic mechanisms of key cellular processes regulation is yet to be elucidated. Given that the effects of bile acids are mostly determined by their polarity, the aim of our study was to investigate in vitro and in vivo effects of semi-synthetic keto derivative of cholic acid, 12-monoketocholic acid (MKC), in comparison to natural bile acids, hydrophobic chenodeoxycholic acid (CDC) and hydrophilic ursodeoxycholic acid (UDC), on processes of apoptosis, oxidative stress and inflammation, which are significant for both&nbsp; chemoprevention and therapy of colon cancer. Besides, the aim of our study was to examine the role of selected bile acids in the epigenetic regulation of these processes in colon cancer cells. In in vivo model of intrahepatic cholestasis in experimental animals, it has been demonstrated that UDC and MKC exhibit antiapoptotic, antioxidant, and antiinflammatory effects in the liver and intestine. It was shown that UDC and MKC prevent the mitochondrial pathway of apoptosis activation in the liver, while UDC exhibits an antiapoptotic effect in the intestine of experimental animals with cholestasis as well. These two bile acids significantly modulated the expression of genes involved in antioxidant protection, as well as the activity of antioxidant enzymes, in the liver and intestine of experimental animals with cholestasis, towards levels of expression and activity in healthy, untreated animals. While UDC and MKC at a low dose of 4 mg/kg exhibited an antiinflammatory effect in the liver and intestine by reducing the expression of the gene encoding the proinflammatory transcription factor NF-&kappa;B, the application of CDC and MKC at a high dose of 20 mg/kg exerted the opposite effect. In HT-29 human adenocarcinoma cell line, it has been demonstrated that semi-synthetic bile acid MKC exhibits significantly lower cytotoxicity than CDC and slightly higher cytotoxicity than UDC. The epigenetic drug vorinostat has exhibited a synergistic cytotoxic effect with all three investigated bile acids. Vorinostat exerted proapoptotic and antiproliferative effects in HT-29 cells, which were most pronounced in combination with MKC, as there was a significant increase in the ratio of BAX and BCL2 genes expression and a decrease of the proliferation marker cyclin D1 gene expression. Vorinostat also significantly reduced the antioxidant capacity of HT-29 cells by reducing the expression of NRF2 gene and consequently decreasing the expression of genes encoding antioxidant enzymes. CDC further reduced, while MKC improved the antioxidant capacity of HT-29 cells by modulating the expression of NRF2 gene. In both in vitro and in vivo systems, it was demonstrated that, in addition to CDC as a known endogenous FXR agonist, MKC also increased the expression of the gene encoding FXR, and FXR target gene encoding transcriptional co-repressor SHP as well, indicating that this semi-synthetic bile acid can also activate FXR. Besides, bile acids have been shown to exert distinct effects on the expression of the histone deacetylases HDAC1 and HDAC2 gene in the liver and intestine of experimental animals, and in HT-29 colon cancer cells. Only UDC significantly reduced the expression of the genes for both studied enzymes involved in the epigenetic regulation of cell processes, in both tissues and HT-29 cells. The results of our work indicate that UDC and MKC could be used in chemoprevention of colon cancer at low doses, considering determined effects in the modulation of expression of the genes involved in processes of apoptosis, oxidative stress and inflammation. Furthermore, synergistic effects of bile acids with the epigenetic antitumor agent vorinostat open up the possibility of a combined pharmacological strategy in the treatment of solid tumors, which are at the high percentage resistant to the effects of vorinostat alone.</p>

In einer Zeit, in der eine Zunahme von ernährungsbedingten Erkrankungen in steigendem Maße zu beobachten ist, wird dem Getreide als Grundlage der menschlichen Ernährung erhöhte Aufmerksamkeit gewidmet. Ein hoher Verzehr von Ballaststoffen ist ein wesentlicher Aspekt in der präventiv-medizinischen Ernährung. Die von der Deutschen Gesellschaft für Ernährung vorgeschlagene tägliche Ballaststoffzufuhr liegt bei 30 g. Die Aufnahme von Ballaststoffen ist jedoch in Deutschland deutlich unterhalb dieser empfohlenen Menge.<br><br> Getreideprodukte, besonders vom Vollkorntyp, sind die wichtigste Quelle für Ballaststoffe. Deshalb sollten im Rahmen dieser Arbeit direkt verzehrsfähige, Ballaststoff-angereicherte Haferprodukte (vorwiegend Extrudate) mit hohen Gehalten an b-Glucanen und resistenter Stärke hergestellt, analysiert und nachfolgend auf relevante ernährungsphysiologische Wirkungen geprüft werden. Als Basis für die Produkte wurden Hafermehl und Haferkleie eingesetzt.<br> Der erste Teil der Arbeit beschäftigte sich mit der Analyse der Haferprodukte. Diese wiesen eine hohe Wasserbindungskapazität auf. Bei den Untersuchungen am Tiermodell wurde gezeigt, dass im Dünndarm eine größere Menge an Wasser durch die Haferprodukte gebunden wurde, was zu einem höheren Feuchtigkeitsanteil der gastrointestinalen Inhalte der Tiere führte, die ballaststoffreiches Futter erhielten.<br><br> Trotz der hydrothermischen Behandlung während der Extrusion wurden Produkte gewonnen, deren β-Glucane im hochmolekularen Zustand erhalten blieben und somit eine hohe Viskosität in wässrigen Lösungen beibehielten. In rheologischen Untersuchungen wurde bestätigt, dass die aus Haferprodukten isolierten β-Glucane ein pseudoplastisches Fließverhalten besitzen. Demgegenüber führte ein Autoklavieren der Produkte zu einer starken Depolymerisation der b-Glucane, was sich in einer Änderung der funktionellen Eigenschaften der b-Glucane widerspiegelte.<br><br> Im Mittelpunkt der Untersuchungen standen ernährungsphysiologische In-vitro- und In-vivo-Experimente mit Extrudaten und Proben auf der Basis von Hafer, die einen erhöhten Anteil an Ballaststoffen, speziell an b-Glucan und an resistenter Stärke, besaßen und die direkt verzehrbar sind. Diese Haferprodukte zeigten eine Reihe von ernährungsphysiologisch vorteilhaften und protektiven Wirkungen in In-vitro-Experimenten. So traten sie mit Gallensäuren unter den Bedingungen des Dünndarms in Wechselwirkung und waren gut mit Faecesflora vom Menschen fermentierbar. Die In-vitro-Verdauung von Maisstärke durch Pankreatin, wurde durch die ballaststoffreichen Haferprodukte partiell gehemmt. Dieser Befund lässt eine Abschwächung des postprandialen Glukoseanstieges erwarten.<br><br> In einem sechswöchigen Fütterungsversuch erhielten Ratten Diäten, die zu 50 % aus ballaststoffreichen Haferprodukten bestanden. Diese Haferprodukte bewirkten einen erhöhten Transport von Gallensäuren und neutralen Sterolen in den unteren Intestinaltrakt sowie deren verstärkte Ausscheidung. Durch den Verzehr der ballaststoffreichen Haferprodukte kam es zu Veränderungen in der Mikroflora, wobei sich besonders die coliformen Keime verminderten und die Keimzahlen der Lactobacillen sowie die Bifidobakterien erhöhten. Die Fermentation der Ballaststoffe führte zur erhöhten Bildung von kurzkettigen Fettsäuren einschließlich von Butyrat. Die Bildung der kurzkettigen Fettsäuren geht mit einer pH-Wert-Absenkung im Caecum und Colon einher, die wiederum für eine geringere Bildung von sekundären Gallensäuren verantwortlich ist.<br><br> Die Ergebnisse des Fütterungsversuchs an Ratten wurden prinzipiell durch eine vierwöchige Pilotstudie am Menschen, in der Probanden täglich 100 g Haferextrudat erhielten, bestätigt. Das Extrudat wurde von den Probanden gut akzeptiert. In der 4. Woche wurden eine geringe Abnahme der Cholesterolfraktionen im Serum, höhere Keimzahlen für Lactobacillen, Bifidobacterien und Bacteroides, geringere pH-Werte und Trockenmassegehalte in den Faeces, eine Zunahme der individuellen und Gesamt-SCFA sowie des Butyratanteils in den Faeces, eine erhöhte Ausscheidung an Steroiden, eine Zunahme der primären Gallensäuren und eine Abnahme des prozentualen Anteils an sekundären Gallensäuren sowie der Cholesterol-Metaboliten gefunden. Diese Parameter gingen 2 Wochen nach Beendigung der Intervention mit dem Haferextrudat wieder in Richtung der Ausgangswerte (0. Woche) zurück.<br><br> Die untersuchten Haferprodukte erwiesen sich als gut fermentierbare Substrate für die intestinale Mikroflora und können deshalb als ein Präbiotikum mit Ballaststoffcharakter eingeschätzt werden. Diese Produkte, die mit einem erhöhten Anteil an resistenter Stärke und wertvollen Haferballaststoffen hergestellt wurden, können dazu beitragen, die Ballaststofflücke in unserer Ernährung zu schließen und positive ernährungsphysiologische Effekte zu bewirken. / Cereal products, particularly from whole grains, are the most important source of dietary fibre in the western diet. A high intake of dietary fibre, which is an essential component in nutrition, is positively related to several physiological and metabolic effects. However, the daily intake of dietary fibre is below the recommended levels (30d/day) in most industrials country. Oat (Avena sativa L.) products are well accepted in human nutrition. Oats is an excellent source of different dietary fibre types, such as β-glucan, arabinoxylans and cellulose, and it contains high levels of proteins, lipids, vitamins, antioxidants and minerals.<br> A series of extrudates was prepared from oat meal, oat bran and Novelose 330®, differing in concentrations of individual dietary fibre components, such as β-glucan and resistant starch, as well as total dietary fibre.<br><br> The cereal dietary fibre, β-glucan, has outstanding functional and nutritional properties, because of its viscosity in aqueous systems and in the intestinal tract. The rheological behaviour of β-glucan (concentrations: 2% and 4%) isolated from extruded oat meal and from oat bran was evaluated using oscillatory and rheological measurements. In frequency sweep, the storage and loss moduli G′ and G″ of β-glucan preparations from extruded meal and from bran increased continuously with increasing frequency, showing a dominantly viscous behaviour. With increasing frequency, the elastic properties improved.<br><br> After simulated digestion, the digested dietary fibre-rich oat-based extrudates were used to evaluate their physiological effects in vitro. A strong interaction occurred between the digested extrudates and bile acids. The binding of bile acids increased with increasing proportions of oat bran, total dietary fibre, insoluble dietary fibre and β-glucan in the extrudates. Dihydroxy-bile acid was more strongly bound to the extrudates than trihydroxy- bile acid. Interactions at pH 5.0 were greater than at pH 6.5. During fermentation of digested extrudates with human faecal samples, concentrations of short-chain fatty acid formed and the molar proportion of butyrate increased continuously. Higher short-chain fatty acid concentrations were found when extrudates contained more oat bran, soluble and insoluble dietary fibre and β-glucan. Extrudates, on the basis of oat, have several beneficial nutritional and protective effects in vitro. Therefore, physiological effects occurring in the small and large intestine are also related to the dietary fibre composition of the cereal products.<br><br> The results found in vitro was examined in feeding experiments with animal models and in nutritional studies with human subjects.<br><br> Male Wistar rats were fed either an oat-free diet (control group) or diet containing 50% oat-based products (test groups) for 6 week. In most of the test group, following effects were observed compared with control group: higher water intake; slightly decreased total and LDL cholesterol in serum; higher count of Bifidobacteria as well as lower count numbers of Coliforms; greater mass of cecum walls and cecal contents; lower pH values in intestinal contents; higher concentration of acetate, propionate and butyrate in cecal contents and greater excretion of short-chain fatty acids; significantly more total bile acids in cecal contents; higher excretion of total bile acids and primary bile acids; lower proportion of secondary bile acids as well as higher concentration of neutral sterols in cecal contents, colonic contents and feces.<br><br> In the human study 12 volunteers consumed 100 g fiber-rich oat-based product (to the habitually diet) daily for 4 week. Following results were observed in the week 4 compared with the beginning of the experiment: higher water intake; slightly decreased total cholesterol in serum; lower pH values in feces; higher concentration of acetate, propionate and butyrate in feces; higher excretion of total bile acids and primary bile acids; lower proportion of secondary bile acids as well as higher concentration of neutral sterols in feces.<br><br> In conclusion, application of the dietary fiber-rich oat-based diets had a variety of beneficial physiological and protective effects in rats and human depending on their composition and amount, their technological pre-treatment and their functional properties. The major effects connected whit fermentation of dietary fibre components and their high formation of short-chain fatty acids as well as with higher excretion of steroids.

Les polymères amphiphiles sont largement utilisés pour les applications biomédicales et pharmaceutiques. Afin d’améliorer les chances de biocompatibilité des nouveaux polymères que nous voulons développer, nous avons utilisé des composés naturels, les acides biliaires, comme produits de départ dans la synthèse de ces polymères. De nouveaux polymères anioniques amphiphiles dérivés de l’acide cholique ont été préparés par polymérisation radicalaire par transfert d’atomes. Par un contrôle rigoureux des conditions de polymérisation, des bras de poly(acide acrylique) de différentes longueurs ont été greffés sur le squelette de l’acide cholique. L’architecture moléculaire des polymères a été étudiée par spectroscopie 1H RMN et par spectrométrie de masse. Ces polymères en étoile formés par l’acide biliaire modifié sont capables de s’agréger dans l’eau même si les groupements hydroxyles ont été remplacés par des segments plus volumineux. Il a été observé que les liaisons ester entre le polymère et le cœur d’acide cholique sont sensibles à l’hydrolyse en solution aqueuse. Pour remédier au problème de stabilité en solution aqueuse et pour avoir, en même temps, des bras hydrophiles non ioniques et biocompatibles, de l’oxyde d’éthylène a été polymérisé sur l’acide cholique par polymérisation anionique. Les liaisons éther formées entre le polymère et les groupements hydroxyles de l’acide biliaire sont plus stables que les liaisons ester sur le polymère de poly(acide acrylique). Les conditions de réaction de la polymérisation anionique ont été optimisées et ont donné des polymères aux architectures et aux masses molaires contrôlées. Les nouveaux polymères forment des agrégats sphériques tel qu’observé par microscopie électronique à transmission avec des échantillons préparés par la méthode de fracture à froid. Leur morphologie est différente de celle des agrégats cylindriques formés par les acides biliaires. Avec la méthode optimisée pour la polymérisation anionique, l’éther d’allyle et glycidyle a été polymérisé sur un dérivé d’acide cholique, suivi par une thiolation des liaisons doubles pour introduire l’amine ou l’acide sur la chaîne polymère. Cette addition radicalaire est efficace à plus de 90%. Les polymères qui en résultent sont solubles dans l’eau et s’agrègent à une certaine concentration critique. Il est particulièrement intéressant d’observer la thermosensibilité des polymères ayant des groupements amine, laquelle peut être modulée en acétylant partiellement les amines, donnant des points nuages entre 15 et 48°C. / Amphiphilic polymers are very useful in biomedical and pharmaceutical applications. To improve the biocompatibility of such polymers, we chose to use natural compounds such as bile acids as the starting material in the synthesis of the polymers. New anionic polymers have been prepared by atom transfer radical polymerization. Poly(acrylic acid) arms of various lengths have been grafted onto a bile acid core. The molecular architecture has been confirmed by 1H NMR spectroscopy and by mass spectrometry. The star polymers obtained from modified bile acid can aggregate in water, even though the hydroxyl groups were replaced by bulkier chains. The ester linkages between the polymers and the bile acid core are prone to hydrolysis in aqueous solutions. In order to improve the stability of the polymers in aqueous solutions and to introduce neutral and biocompatible hydrophilic arms, ethylene oxide has been polymerized onto a cholic acid core by anionic polymerization. The ether linkages formed between the hydroxyl groups of the bile acid and the poly(ethylene glycol) are more stable than the ester linkages formed with the poly(acrylic acid) polymers. The reaction conditions for the anionic polymerization have been optimized and provided well-defined polymers with narrow molecular weight distributions. The new polymers formed spherical aggregates as shown by transmission electron microscopy with samples prepared by the freeze-fracture technique. Their morphology is different from those of the cylindrical aggregates formed by bile salts. With the optimized method for anionic polymerization, allyl glycidyl ether was grafted onto a derivative of cholic acid, followed by thiolation, a radical addition, of the allyl groups to introduce amine or carboxylic acid groups to the polymer chains. This radical addition had an efficiency of more than 90%. The resulting polymers were water-soluble and were found to aggregate above a certain critical concentration. It is particularly interesting to observe thermosensitivity of the star polymers bearing amine groups. The thermosensitivity of such polymers can be further tuned by partial acetylation of the amine groups, yielding polymers with cloud points in the temperature range from 15 to 48°C.

Le récepteur X des farnésoïdes (FXR) fait partie de la superfamille des récepteurs nucléaires et agit comme un facteur de transcription suite à la liaison d’un ligand spécifique. Le récepteur FXR, activé par les acides biliaires, joue un rôle essentiel dans le métabolisme des lipides et du glucose en plus de réguler l’homéostasie des acides biliaires. Notre laboratoire a récemment mis en évidence une nouvelle voie de régulation du récepteur PPARγ en réponse au récepteur de la ghréline. En effet, la ghréline induit l’activation transcriptionnelle de PPARγ via une cascade de signalisation impliquant les kinases Erk1/2 et Akt, supportant un rôle périphérique de la ghréline dans les pathologies associées au syndrome métabolique. Il est de plus en plus reconnu que la cascade métabolique impliquant PPARγ fait également intervenir un autre récepteur nucléaire, FXR. Dans ce travail, nous montrons que la ghréline induit l’activation transcriptionnelle de FXR de manière dose-dépendante et induit également la phosphorylation du récepteur sur ses résidus sérine. En utilisant des constructions tronquées ABC et CDEF de FXR, nous avons démontré que la ghréline régule l’activité de FXR via les domaines d’activation AF-1 et AF-2. L’effet de la ghréline et du ligand sélectif GW4064 sur l’induction de FXR est additif. De plus, nous avons démontré que FXR est la cible d’une autre modification post-traductionnelle, soit la sumoylation. En effet, FXR est un substrat cellulaire des protéines SUMO-1 et SUMO-3 et la sumoylation du récepteur est ligand-indépendante. SUMO-1 et SUMO-3 induisent l’activation transcriptionnelle de FXR de façon dose-dépendante. Nos résultats indiquent que la lysine 122 est le site prédominant de sumoylation par SUMO-1, quoiqu’un mécanisme de coopération semble exister entre les différents sites de sumoylation de FXR. Avec son rôle émergeant dans plusieurs voies du métabolisme lipidique, l’identification de modulateurs de FXR s’avère être une approche fort prometteuse pour faire face à plusieurs pathologies associées au syndrome métabolique et au diabète de type 2. / The farnesoid X receptor (FXR) is a ligand-activated transcription factor within the nuclear receptor superfamily. FXR is activated by bile acids and plays a crucial role in the regulation of glucose and lipid metabolism and in bile acid homeostasis. Our group has recently identified the contribution of the ghrelin receptor in the regulation of the nuclear receptor PPARγ. Indeed, ghrelin triggers transcriptional activation of PPARγ through a concerted signaling cascade involving Erk1/2 and Akt kinases. These results support the peripheral actions of ghrelin in diseases associated with the metabolic syndrome. It is recognized that there is interplay between PPARγ metabolic cascade and FXR. Here, we demonstrate that ghrelin promotes FXR transcriptional activity in a dose-dependent manner and also promotes its phosphorylation on serine residues. By using truncated ABC and CDEF constructs of FXR, we found that ghrelin induces FXR activity through the AF-1 and AF-2 activation domains. The ghrelin-induced FXR activity is additive to the induction by the selective agonist GW4064. Also, we demonstrate that FXR is the target of sumoylation, another post-translational modification. In particular, FXR is modified by SUMO-1 and SUMO-3 in a ligand-independent manner. SUMO-1 and SUMO-3 promote dose-dependent transcriptional activity of FXR. Our results show that lysine 122 is the prevalent site of sumoylation by SUMO-1, though a compensation mechanism seems to exist between the various sumoylation sites of FXR. With its emerging role in several metabolic cascades, identification of FXR modulators represents a promising approach for the treatment of the metabolic syndrome and type 2 diabetes.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.