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The Intensive Care Unit-Acquired Weakness: the role of mitochondrial dysfunction in its pathogenesis
Jiroutková, Kateřina ; Duška, František (advisor) ; Houštěk, Josef (referee) ; Maňák, Jan (referee)
BACKGROUND: ICU-acquired weakness impairs functional outcome in survivors of critical illness. Therefore, deepening our understanding of its pathogenesis is an important goal as muscle-specific therapeutic targets are urgently needed. Systemic inflammation and sepsis are the main risk factors of ICUAW, and these syndromes are associated with mitochondrial dysfunction. The aim of our study was to collect reliable information on the mitochondrial function of human skeletal muscle in the protracted phase of critical illness. Additionally, we explored mitochondrial respiratory parameters following experimentally induced changes in the availability or composition of selected nutrients (fatty acids and glutamine). MATERIALS and METHODS: Vastus lateralis muscle biopsy samples from patients with ICU- acquired weakness and age-matched healthy controls were obtained. In human skeletal muscle tissue homogenates mitochondrial functional indices were assessed by high- resolution respirometry, individual functional capacities of respiratory complexes were measured by spectrophotometry and correlated with concentrations of electron transport chain key subunits measured by western blot. Additionally, using human myoblasts and myotubes we studied the influence of extracellular environment manipulations by...
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Effect of selected drugs on mitochondrial metabolism in an in vitro model of human skeletal muscle
Krajčová, Adéla ; Anděl, Michal (advisor) ; Kieslichová, Eva (referee) ; Houštěk, Josef (referee)
Introduction: Increasing number of reports reflect that mitochondrial dysfunction can be induced by some of the commonly used drugs and can play a key role in the development of their adverse effects. One of these drugs is a phenol derivative propofol. Propofol is an intravenous, fast and short-acting hypnotic agent, routinely used either for induction and maintenance of anaesthesia during surgery, or for sedation in intensive care units. Propofol infusion syndrome (PRIS) is a rare, but serious adverse effect of the drug with a very high mortality. Typical features of the syndrome include metabolic acidosis, arrhythmias, ECG changes that are similar to those of Brugada syndrome, hypertriglyceridemia, fever, hepatomegaly, rhabdomyolysis, cardiac and/or renal failure. The risk of the syndrome increases with raising dose and duration of propofol administration (˃48 hours). The mechanism of the syndrome is still unknown: pilot studies performed on animal models are suggestive of its mitochondrial origin. In the first part of the study, we performed the analysis of 153 published case reports and all experimental studies related to PRIS. Another aim of the study was to test hypothesis of propofol- induced mitochondrial damage by in vitro exposure of human skeletal muscle-derived cells to a range of...
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Study of metabolic syndrome in mice model: roles of dietary lipids, adipose tissue and AMP-activated protein kinase
Medříková, Daša ; Kopecký, Jan (advisor) ; Houštěk, Josef (referee) ; Novotný, Jiří (referee)
Obesity and associated metabolic disorders, e. g. metabolic syndrome, represent a considerable health threat for modern society. Due to sedentary lifestyle, high caloric intake and changes in composition of diet, prevalence of obesity is increasing worldwide. One of the possible causes contributing to higher prevalence of obesity in recent population could be the change of fatty acids (FA) composition of dietary lipids, with the shift in the content of n-6 and n-3 FA toward n-6 FA. In contrast to n-6 FA, n-3 FA are known for their anti-atherogenic, anti-obesogenic and anti-inflammatory properties. In our experiments in mice, the capability of naturally occurred and chemically modified n- 3 long chain polyunsaturated fatty acids (LC-PUFA) in prevention and reversal of specific parts of metabolic syndrome was demonstrated. A specific chemical derivative of docosahexaenoic acid was proven to be very effective in preventing and improving metabolic conditions of animals exposed to high-fat (HF) diet challenge. Further, the involvement of AMP-activated protein kinase (AMPK), a master regulator of lipid metabolism, in skeletal muscle thermogenesis induced by HF-feeding was investigated. Activation of AMPK in the HF-fed mice is most possibly caused by increased leptin levels and represents an important link...
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Regulation and Disorders of Mammalian Cytochrome c Oxidase
Kovářová, Nikola ; Houštěk, Josef (advisor) ; Stibůrek, Lukáš (referee) ; Kalous, Martin (referee)
Cytochrome c oxidase (COX) represents the terminal enzyme complex of respiratory chain metabolic pathway and it occurs as monomer, dimer or as a part of respiratory supercomplexes in the inner mitochondrial membrane. COX assembly process is complicated, highly regulated and depends on many ancillary proteins. Mutations in COX subunits, which are encoded by mitochondrial and nuclear DNA, or in genes encoding its assembly proteins are frequent cause of very severe mitochondrial disorders. SURF1 assembly protein participates in the first steps of COX assembly, but its exact function is not yet clarified. In humans, mutations of SURF1 gene lead to severe COX defect and fatal neurodegenerative disorder, Leigh syndrome. Knockout of SURF1 gene in mouse causes isolated COX defect as well, but less pronounced and without involvement of CNS. The aim of the thesis was detailed analysis of disturbed COX biogenesis in a condition of SURF1 gene mutations or SURF1 gene knockout, from assembly of COX monomer to interaction of COX into supercomplexes, and to the impact of isolated COX defect on other OXPHOS complexes. Mutations of SURF1 gene in patient's fibroblasts led to marked accumulation of COX assembly intermediates and to a defect in formation of functional COX monomer, which was preferentially built into an...
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Genetic and functional characterisation of mitochondrial diseases caused by ATP synthase defects
Tauchmannová, Kateřina ; Houštěk, Josef (advisor) ; Flachs, Pavel (referee) ; Kutejová, Eva (referee)
Disorders of ATP synthase, the key enzyme of mitochondrial energy provision belong to the most severe metabolic diseases presenting mostly as early-onset mitochondrial encephalo-cardio-myopathies. Mutations in four nuclear genes can result in isolated deficiency of ATP synthase, all sharing a similar biochemical phenotype - pronounced decrease in the content of fully assembled and functional ATP synthase complex. The thesis summarises studies on two distinct causes of ATP synthase deficiency. First is TMEM70 protein, a novel ancillary factor of ATP synthase, which represents most frequent determinant of severe inborn deficiency of ATP synthase. TMEM70 is a 21 kDa protein of the inner mitochondrial membrane, facilitating the biogenesis of mitochondrial ATP synthase, possibly through TMEM70 protein region exposed to the mitochondrial matrix, but the proper regulatory mechanism remains to be elucidated. In TMEM70-lacking patient fibroblasts the low content of ATP synthase induces compensatory adaptive upregulation of mitochondrial respiratory chain complexes III and IV, interestingly by a posttranscriptional mechanisms. The second type of ATP synthase deficiency studied was mtDNA m.9205delTA mutation affecting maturation of MT-ATP8/MT-ATP6/MT-CO3 mRNA and thus biosynthesis of Atp6 (subunit a) and Cox3...
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Structural and Functional Interactions of Mitochondrial ADP-Phosphorylating Apparatus
Nůsková, Hana ; Houštěk, Josef (advisor) ; Kolarov, Jordan (referee) ; Kuda, Ondřej (referee) ; Panicucci Zíková, Alena (referee)
The complexes of the oxidative phosphorylation (OXPHOS) system in the inner mitochondrial membrane are organised into structural and functional super-assemblies, so-called supercomplexes. This type of organisation enables substrate channelling and hence improves the overall OXPHOS efficiency. ATP synthase associates into dimers and higher oligomers. Within the supercomplex of ATP synthasome, it interacts with ADP/ATP translocase (ANT), which exchanges synthesised ATP for cytosolic ADP, and inorganic phosphate carrier (PiC), which imports phosphate into the mitochondrial matrix. The existence of this supercomplex is generally accepted. Experimental evidence is however still lacking. In this thesis, structural interactions between ATP synthase, ANT and PiC were studied in detail. In addition, the interdependence of their expression was examined either under physiological conditions in rat tissues or using model cell lines with ATP synthase deficiencies of different origin. Specifically, they included mutations in the nuclear genes ATP5E and TMEM70 that code for subunit ε and the ancillary factor of ATP synthase biogenesis TMEM70, respectively, and a microdeletion at the interface of genes MT-ATP6 and MT-COX3 that impairs the mitochondrial translation of both subunit a of ATP synthase and subunit Cox3...
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Effect of selected drugs on mitochondrial metabolism in an in vitro model of human skeletal muscle
Krajčová, Adéla ; Anděl, Michal (advisor) ; Kieslichová, Eva (referee) ; Houštěk, Josef (referee)
Introduction: Increasing number of reports reflect that mitochondrial dysfunction can be induced by some of the commonly used drugs and can play a key role in the development of their adverse effects. One of these drugs is a phenol derivative propofol. Propofol is an intravenous, fast and short-acting hypnotic agent, routinely used either for induction and maintenance of anaesthesia during surgery, or for sedation in intensive care units. Propofol infusion syndrome (PRIS) is a rare, but serious adverse effect of the drug with a very high mortality. Typical features of the syndrome include metabolic acidosis, arrhythmias, ECG changes that are similar to those of Brugada syndrome, hypertriglyceridemia, fever, hepatomegaly, rhabdomyolysis, cardiac and/or renal failure. The risk of the syndrome increases with raising dose and duration of propofol administration (˃48 hours). The mechanism of the syndrome is still unknown: pilot studies performed on animal models are suggestive of its mitochondrial origin. In the first part of the study, we performed the analysis of 153 published case reports and all experimental studies related to PRIS. Another aim of the study was to test hypothesis of propofol- induced mitochondrial damage by in vitro exposure of human skeletal muscle-derived cells to a range of...
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