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Metabolic effects of bile lipids
Žížalová, Kateřina ; Leníček, Martin (advisor) ; Jirsa, Milan (referee) ; Dvořák, Karel (referee)
Bile acids act as important fat emulsifiers in the human body. However, it is increasingly becoming apparent that they also play a role as important signalling molecules. Bile acids are a relatively heterogeneous group differing also in their metabolic effects. Their individual proportion in the body is highly variable and strongly influenced by the composition of the microbiome. The importance of individual bile acids is not yet well enough described to be fully exploited in clinical practice. For this reason, the determination of bile acids by enzymatic methods seems to be considered sufficient in most departments. Another and more reliable option is the increasingly widespread use of liquid chromatography-tandem mass spectrometry (LC-MS/MS). The aim of my work was to test the reliability of the enzymatic method and to introduce a method for the determination of bile acids, including the measurement of such atypical ones for example microbial conjugates and keto- and isoderivatives. Moreover, I aimed to test sample preparation for the measurement of 7α-hydroxy-4-cholesten-3-one, the bile acid biosynthesis marker. We used these methods to investigate the changes in bile acid composition changes in iron overload rats. In this rat model of genetically determined disorders of iron metabolism, bile...
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Metabolism of immunosuppressants in children with inflammatory bowel disease
Pospíšilová, Kristýna ; Bronský, Jiří (advisor) ; Leníček, Martin (referee) ; Dědek, Petr (referee)
Metabolism of immunosuppressants in children with inflammatory bowel disease Abstract Thiopurines are still used as the main immunosuppressants in the maintenance therapy of paediatric Crohn's disease. According to official guidelines, in case of failure, biological therapy (mainly infliximab or adalimumab) is generally commenced. The present thesis focuses on the possibilities of therapy optimization in children in whom the conventional Crohn's disease therapy has failed based on the metabolism of administered immunosuppressive medications. We confirmed that the knowledge of thiopurine metabolites concentration in red blood cells may help to monitor patients' adherence to therapy. However, according to our observations in children on combination therapy of infliximab and thiopurine lower concentrations of 6- thioguanine (the active metabolite of thiopurines) seems to be effective compared to what has been expected. We presented a web application designed to partially substitute for the thiopurine metabolite measurements based on easily available laboratory data. Last, but not least, we confirmed that the clinical effect and safety profile of both adalimumab and infliximab are similar in the treatment of paediatric Crohn's disease. Only in case of family history of atopic dermatitis adalimumab may be preferred.
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Serum markers of cholesterol 7α hydroxylase activity
Bohdanecká, Alena ; Leníček, Martin (advisor) ; Kovář, Jan (referee)
Cholesterol 7-hydroxylase (CYP7A1) is the rate limiting enzyme of the classical pathway of bile acid (BA) synthesis, which catabolizes approximately half of cholesterol in man. Determination of CYP7A enzymatic activity is a key subject of lipid metabolism research. Direct determination of CYP7A1 activity in hepatic biopsy is mostly not allowed for ethical reasons, so indirect methods are used with serum markers such as 7α-hydroxy-4-cholestene-3- one (C4). The first, methodical aim of the work was to convert the introduced HPLC method for the determination of C4 to LC-MS in order to increase the sensitivity. We focused on the solid phase extraction step, adjusting the composition and volumes of the washing and elution solution. By converting the method from HPLC to LC-MS, the sensitivity was increased approximately 7 times (LD = 1.39 ng/ml). In the second, clinical part of our work, we attempted to confirm the preliminary results of our laboratory on the distribution of C4 in lipoprotein fractions (LPP) in order to find parameter that would correlate with CYP7A1 activity better than C4 level itself. Preliminary results (performed in healthy individuals) showed that most of C4 is carried on HDL, and that the C4 distribution within LPP fractions is similar among examined subjects. We repeated the...
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The importance of biosynthetic and catabolic pathway of cholesterol in inflammatory and tumor diseases
Leníček, Martin ; Vítek, Libor (advisor) ; Haluzík, Martin (referee) ; Mareček, Zdeněk (referee)
This thesis focuses on the importance of intermediate products of biosynthetic and catabolic pathway of cholesterol. The aim of the first part of the thesis is mainly to investigate, whether statins (HMG- CoA reductase inhibitors) possess antitumor properties and to compare the differences in antitumor potential of individual statins. The other part of the thesis aims at the utilization of 7α-hydroxycholest-4-en-3-one (C4), a promising marker of cholesterol 7α-monooxygenase (CYP7A1) activity and bile acid malabsorption. We demonstrated antitumor effect of statins on an experimental model of pancreatic cancer. Individual statins, however, differed significantly in their efficacy, depending on their physico-chemical properties. Our data suggests, that the most likely (but not the only) mechanism of antitumor effect of statins is decreased prenylation of signaling proteins, especially Ras protooncogene. We set up a reliable method for measurement of C4, which facilitated our research in CYP7A1 regulation. We demonstrated, that promoter polymorphism -203A>C might affect CYP7A1 activity, that diurnal variability of CYP7A1 activity might be triggered by insulin, and that insulin resistance in patients with non-alcoholic fatty liver disease impedes the feedback regulation of CYP7A1, which may lead to disease...
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Serum markers of cholesterol 7α hydroxylase activity
Bohdanecká, Alena ; Leníček, Martin (advisor) ; Kovář, Jan (referee)
Cholesterol 7-hydroxylase (CYP7A1) is the rate limiting enzyme of the classical pathway of bile acid (BA) synthesis, which catabolizes approximately half of cholesterol in man. Determination of CYP7A enzymatic activity is a key subject of lipid metabolism research. Direct determination of CYP7A1 activity in hepatic biopsy is mostly not allowed for ethical reasons, so indirect methods are used with serum markers such as 7α-hydroxy-4-cholestene-3- one (C4). The first, methodical aim of the work was to convert the introduced HPLC method for the determination of C4 to LC-MS in order to increase the sensitivity. We focused on the solid phase extraction step, adjusting the composition and volumes of the washing and elution solution. By converting the method from HPLC to LC-MS, the sensitivity was increased approximately 7 times (LD = 1.39 ng/ml). In the second, clinical part of our work, we attempted to confirm the preliminary results of our laboratory on the distribution of C4 in lipoprotein fractions (LPP) in order to find parameter that would correlate with CYP7A1 activity better than C4 level itself. Preliminary results (performed in healthy individuals) showed that most of C4 is carried on HDL, and that the C4 distribution within LPP fractions is similar among examined subjects. We repeated the...
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Regulation of liver regeneration as assessed by means of molecular genetics
Rychtrmoc, David ; Červinková, Zuzana (advisor) ; Leníček, Martin (referee) ; Pospíšilová, Šárka (referee)
Regulation of liver regeneration as assessed by means of molecular genetics Liver regeneration is a noteworthy phenomenon of a vigorous tissue recovery following a wide variety of damaging events. Regenerative ability of the liver is unique among the mammalian visceral organs and plays its role in pathophysiology of heterogeneous hepatic diseases. The recovery process occurs in three phases of which the termination remains the least elucidated. Even the questions of regeneration termination timing and of completeness of organ build-up are still controversial despite decades of studies. The aim of the present thesis was to analyse gene expression data pertinent to late phase of liver regeneration.We evaluated the course of spontaneous recovery in rats subjected to 2/3 partial hepatectomy. Because of lack of generally agreed parameter of hepatic regeneration completeness we proposed a proprietary indicator denoted as %LReg, based on organ and whole body weight assessments performed throughout the study. Gene expression analysis was first performed using DNA microarrays and consequently by real-time RT-PCR. Whole genome scale transcriptional analysis yielded vast amount of data covering gene expression dynamics of fourteen post-surgery days after 2/3 partial hepatectomy in adult male rats. This intervention in...
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The role of cholesterol 7alpha-hydroxylase in regulation of cholesterolemia
Cejpková, Monika ; Kovář, Jan (advisor) ; Leníček, Martin (referee)
The aim of the theses is to characterize the mechanism that participate in the regulation of activity of cholesterol 7α-hydroxylase (CYP7A1) - the key enzyme of classical pathway of bile acids synthesis. The function and metabolism of cholesterol and bile acid is described at the beginning. Cholesterol is a substrate for CYP7A1 and bile acids are produced in the reaction catalyzed by the enzyme. The other parth of theses is dedicated to feedback inhibition of CYP7A1 by bile acids and describes particular regulatory pathways involved. The crucial factors for CYP7A1 expression are bile acids response elements (BARE) in the promoter of CYP7A1 gene. Central role is played by farnesoid X receptor activated by bile salts that induces expression of protein called small heterodimer partner (SHP) in the liver. SHP interacts with trancription factors in BARE and inhibits CYP7A1 transcription. In the instestine FXR induces fibroblast growth factor 19 (FGF19) that activates signalling pathways leading to inhibition of CYP7A1 in the liver. The activity of CYP7A1 can be regulated independently of FXR - there is a role for hormones (insulin, glucagon), glucose, activation of proinflammatory cytokines and other nuclear receptors (pregnane X receptor and vitamin D receptor), that participate in protection of the...
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The importance of biosynthetic and catabolic pathway of cholesterol in inflammatory and tumor diseases
Leníček, Martin ; Vítek, Libor (advisor) ; Haluzík, Martin (referee) ; Mareček, Zdeněk (referee)
This thesis focuses on the importance of intermediate products of biosynthetic and catabolic pathway of cholesterol. The aim of the first part of the thesis is mainly to investigate, whether statins (HMG- CoA reductase inhibitors) possess antitumor properties and to compare the differences in antitumor potential of individual statins. The other part of the thesis aims at the utilization of 7α-hydroxycholest-4-en-3-one (C4), a promising marker of cholesterol 7α-monooxygenase (CYP7A1) activity and bile acid malabsorption. We demonstrated antitumor effect of statins on an experimental model of pancreatic cancer. Individual statins, however, differed significantly in their efficacy, depending on their physico-chemical properties. Our data suggests, that the most likely (but not the only) mechanism of antitumor effect of statins is decreased prenylation of signaling proteins, especially Ras protooncogene. We set up a reliable method for measurement of C4, which facilitated our research in CYP7A1 regulation. We demonstrated, that promoter polymorphism -203A>C might affect CYP7A1 activity, that diurnal variability of CYP7A1 activity might be triggered by insulin, and that insulin resistance in patients with non-alcoholic fatty liver disease impedes the feedback regulation of CYP7A1, which may lead to disease...
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