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Author: Amanda R. Stram Publisher: ISBN: Category : Languages : en Pages : 150
Book Description
Rationale: The childhood heart disease of Friedreich's Ataxia (FRDA) is characterized by hypertrophy and failure. It is caused by loss of frataxin (FXN), a mitochondrial protein involved in energy homeostasis. FRDA model hearts have increased mitochondrial protein acetylation and impaired sirtuin 3 (SIRT3) deacetylase activity. Protein acetylation is an important regulator of cardiac metabolism and SIRT3 is protective in heart disease. The underlying pathophysiology of heart failure in FRDA is unclear. I suspect that increased acetylation in FRDA heart mitochondria damages cardiac energy homeostasis by inhibiting activity of key enzymes involved in heart metabolism. Objective: My project tested the hypothesis that altered acetylation of mitochondrial proteins contributes to the cardiomyopathy of FRDA. Methods: Conditional mouse models of FRDA cardiomyopathy with ablation of FXN (FXN KO) or FXN and SIRT3 (FXN/SIRT3 DKO) in the heart were compared to healthy controls. Hearts were evaluated using echocardiography, cardiac catheterization, histology, protein acetylation and expression. FXN KO mice were treated with NAD+ replacement therapy with nicotinamide riboside (NR), and FXN/SIRT3 DKO mice were treated with FXN protein replacement therapy. Results: Acetylation was temporally progressive and paralleled evolution of heart failure in the FXN KO model. High levels of acetylation were associated with cardiac fibrosis, mitochondrial damage, impaired fat metabolism, and diastolic and systolic dysfunction. Acetylation correlated strongly with worse heart function, and loss of SIRT3 in the FXN KO mouse resulted in significant decrease in ejection fraction and fractional shortening. Treatment of the FXN/SIRT3 DKO with FXN protein therapy reduced acetylation but was not sufficient to fully rescue heart function. Increasing NAD+ with NR-treatment in the FXN KO lead to increased mitochondrial protein acetylation and did not improve cardiac outcome. Conclusion: I found a strong negative correlation between heart function and mitochondrial protein acetylation. My findings also provide evidence that absence of SIRT3 expression in the FXN KO heart exacerbates features of heart failure, and that SIRT3 expression is necessary to rescue the FXN KO heart. These results suggest that SIRT3 inactivation and abnormal acetylation contribute to the pathophysiology of heart disease in FRDA.
Author: Amanda R. Stram Publisher: ISBN: Category : Languages : en Pages : 150
Book Description
Rationale: The childhood heart disease of Friedreich's Ataxia (FRDA) is characterized by hypertrophy and failure. It is caused by loss of frataxin (FXN), a mitochondrial protein involved in energy homeostasis. FRDA model hearts have increased mitochondrial protein acetylation and impaired sirtuin 3 (SIRT3) deacetylase activity. Protein acetylation is an important regulator of cardiac metabolism and SIRT3 is protective in heart disease. The underlying pathophysiology of heart failure in FRDA is unclear. I suspect that increased acetylation in FRDA heart mitochondria damages cardiac energy homeostasis by inhibiting activity of key enzymes involved in heart metabolism. Objective: My project tested the hypothesis that altered acetylation of mitochondrial proteins contributes to the cardiomyopathy of FRDA. Methods: Conditional mouse models of FRDA cardiomyopathy with ablation of FXN (FXN KO) or FXN and SIRT3 (FXN/SIRT3 DKO) in the heart were compared to healthy controls. Hearts were evaluated using echocardiography, cardiac catheterization, histology, protein acetylation and expression. FXN KO mice were treated with NAD+ replacement therapy with nicotinamide riboside (NR), and FXN/SIRT3 DKO mice were treated with FXN protein replacement therapy. Results: Acetylation was temporally progressive and paralleled evolution of heart failure in the FXN KO model. High levels of acetylation were associated with cardiac fibrosis, mitochondrial damage, impaired fat metabolism, and diastolic and systolic dysfunction. Acetylation correlated strongly with worse heart function, and loss of SIRT3 in the FXN KO mouse resulted in significant decrease in ejection fraction and fractional shortening. Treatment of the FXN/SIRT3 DKO with FXN protein therapy reduced acetylation but was not sufficient to fully rescue heart function. Increasing NAD+ with NR-treatment in the FXN KO lead to increased mitochondrial protein acetylation and did not improve cardiac outcome. Conclusion: I found a strong negative correlation between heart function and mitochondrial protein acetylation. My findings also provide evidence that absence of SIRT3 expression in the FXN KO heart exacerbates features of heart failure, and that SIRT3 expression is necessary to rescue the FXN KO heart. These results suggest that SIRT3 inactivation and abnormal acetylation contribute to the pathophysiology of heart disease in FRDA.
Author: Gregory Randall Wagner Publisher: ISBN: Category : Acetylation Languages : en Pages : 252
Book Description
Friedreich's Ataxia (FRDA) is a rare and poorly understood autosomal recessive disease caused by a pathological deficiency of the mitochondrial protein frataxin. Patients suffer neurodegeneration, ataxia, diabetes, and heart failure. In an effort to understand the mechanisms of heart failure in FRDA, we investigated the role of the protein modification acetylation, which is highly abundant on mitochondrial proteins and has been implicated in regulating intermediary metabolism. Using mouse models of FRDA, we found that cardiac frataxin deficiency causes progressive hyperacetylation of mitochondrial proteins which is correlated with loss of respiratory chain subunits and an altered mitochondrial redox state. Mitochondrial protein hyperacetylation could be reversed by the mitochondria-localized deacetylase SIRT3 in vitro, suggesting a defect in endogenous SIRT3 activity. Consistently, frataxin-deficient cardiac mitochondria showed significantly decreased rates of fatty acid oxidation and complete oxidation to carbon dioxide. However, the degree of protein hyperacetylation in FRDA could not be fully explained by SIRT3 loss. Our data suggested that intermediary metabolites and perhaps acetyl-CoA, which is required for protein acetylation, are accumulating in frataxin-deficient mitochondria. Upon testing the hypothesis that mitochondrial protein acetylation is non-enzymatic, we found that the minimal chemical conditions of the mitochondrial matrix are sufficient to cause widespread non-enzymatic protein acetylation in vitro. These data suggest that mitochondrial protein hyperacetylation in FRDA cardiomyopathy mediates progressive post-translational suppression of mitochondrial oxidative pathways which is caused by a combination of SIRT3 deficiency and, likely, an accumulation of unoxidized acetyl-CoA capable of initiating non-enzymatic protein acetylation. These findings provide novel insight into the mechanisms underlying a poorly understood and fatal cardiomyopathy and highlight a fundamental biochemical mechanism that had been previously overlooked in biological systems.
Author: Gaetano Santulli Publisher: Springer ISBN: 3319553305 Category : Science Languages : en Pages : 644
Book Description
This text covers the basic principles of mitochondrial dynamics in cardiovascular medicine, with particular emphasis on their functional roles in physiology and disease. The book will include articles pertaining to mitochondrial fitness on a global basis, providing therefore an update on the progress made in several aspects in the field. Thus, it will assist scientists and clinicians alike in furthering basic and translational research. Organized in sections focusing on: basic science, mitochondrial dysfunction in cardiac disorders, in vascular disorders, in metabolic disorders, in kidney disease, therapeutic challenges and options, this essential volume fills imperative gaps in understanding and potentially treating several cardiovascular disorders.
Author: Jose Guadalupe Gomez-Arroyo Publisher: ISBN: Category : Languages : en Pages : 388
Book Description
Right ventricular dysfunction is the most frequent cause of death in patients with pulmonary arterial hypertension. Although abnormal energy substrate use has been implicated in the development of chronic left heart failure, data describing such metabolic remodeling in failing right ventricular tissue remain incomplete. In the present dissertation we sought to characterize metabolic gene expression changes and mitochondrial dysfunction in functional and dysfunctional RV hypertrophy. Two different rat models of RV hypertrophy were studied. The model of right ventricular failure (SU5416/hypoxia) exhibited a significantly decreased gene expression of peroxisome proliferator-activated receptor- coactivator-1[alpha], peroxisome proliferator- activated receptor-[alpha] and estrogen-related receptor-[alpha]. The expression of multiple peroxisome proliferator-activated receptor- coactivator-1[alpha] target genes required for fatty acid oxidation was similarly decreased. Decreased peroxisome proliferator-activated receptor- coactivator-1[alpha] expression was also associated with a net loss of mitochondrial protein and oxidative capacity. Reduced mitochondrial number was associated with a downregulation of transcription factor A, mitochondrial, and other genes required for mitochondrial biogenesis. Electron microscopy demonstrated that, in right ventricular failure tissue, mitochondria had abnormal shape and size. Lastly, respirometric analysis demonstrated that mitochondria isolated from right ventricular failure tissue had a significantly reduced ADP- stimulated (state 3) rate for complex I. Conversely, functional right ventricular hypertrophy in the pulmonary artery banding model showed normal expression of peroxisome proliferator-activated receptor- coactivator-1[alpha], whereas the expression of fatty acid oxidation genes was either preserved or unregulated. Moreover, pulmonary artery banding-right ventricular tissue exhibited preserved transcription factor A mitochondrial expression and mitochondrial respiration despite elevated right ventricular pressure-overload. We conclude that right ventricular dysfunction, but not functional right ventricular hypertrophy in rats, demonstrates a gene expression profile compatible with a multilevel impairment of fatty acid metabolism and significant mitochondrial dysfunction, partially independent of chronic pressure-overload.
Author: Edward Lau Publisher: ISBN: Category : Languages : en Pages : 235
Book Description
The cardiac mitochondrial proteome contains ~1,500 distinct proteins that carry out necessary metabolic and energetic processes in the heart. To sustain cardiac function, the mitochondrial proteome must be maintained in constant renewal, or turnover, especially under stress conditions. Disruptions of protein turnover can lead to protein damage and proteotoxicity, a hallmark of many heart disease etiologies. Current quantitative proteomics experiments largely focus on the measurement of the steady-state abundance, or changes therein, of proteins that are present in a system, and give little insights into the underlying regulations of protein synthesis, degradation, and homeostasis. Protein turnover rates provide this missing temporal dimension of information, and can inform on the potential mechanism through which protein abundance may permute during the development of disease (e.g., via increased synthesis or decreased degradation). Currently, such investigations are hampered by the fact that the technology to measure protein turnover in animals on a large scale has not been well developed. This dissertation outlines a new method to measure protein turnover half-life in the cardiac mitochondrion. Basic features of the regulation of protein turnover in the mitochondrion are discussed, and how protein dynamics permutes in early-stage heart failure after hypertrophic stimuli is described. In total, we measured the turnover rates of 2,986 proteins in the mouse heart under basal conditions, isoproterenol stimulus, and post-stimulus recovery, including 1,078 proteins from isolated mitochondria. The data revealed widespread, bidirectional changes in protein turnover in 35 functional categories, and further identified a number of novel candidate disease proteins with significantly up-regulated turnover rates in disease, including HK1, ALDH1B1, and PHB, which have been obscured from previous investigations due to their inconspicuous changes in steady-state abundance. Combinatorial analysis of protein expression and protein turnover data indicates that the remodeling heart is characterized by decreased turnover but increased expression of a cohort of mitochondrial proteins including FXN, LETM1, and CYC1, suggesting a potential class of candidate disease proteins whose impaired degradation is associated with remodeling. I further discuss the implications of the data to the cardiac remodeling process at large and how such investigations may be translated to human studies in the future. Taken together, the results suggest that comparisons of protein turnover rates can be a powerful new tool to understand the temporal dynamics of disease progression in the heart.
Author: Georges Kanaan Publisher: ISBN: Category : Languages : en Pages :
Book Description
Mitochondrial dysfunction is a common feature in a wide range of disorders and diseases from obesity, diabetes, cancer to cardiovascular diseases. The overall goal of my doctoral research has been to investigate mitochondrial metabolic dysfunction in skeletal and cardiac muscles in the context of chronic disease development. Perinatal nutrition is well known to affect risk for insulin resistance, obesity, and cardiovascular disease during adulthood. The underlying mechanisms however, are poorly understood. Previous research from our lab showed that the in utero maternal undernutrition mouse model is one in which skeletal and cardiac muscle physiology and metabolism is impaired. Here we used this model to study the impact of in utero undernutrition on offspring skeletal primary muscle cells and to determine if there is a cell autonomous phenotype. Metabolic analyses using extracellular flux technologies revealed a shift from oxidative to glycolytic metabolism in primary myotubes. Gene expression profiling identified significant changes in mRNA expression, including an upregulation of cell stress and OXPHOS genes and a downregulation of cell division genes. However, there were no changes in levels of marker proteins for mitochondrial oxidative phosphorylation (OXPHOS). Findings are consistent with the conclusion that susceptibility to metabolic disease in adulthood can be caused at least in part by muscle defects that are programmed in utero and mediated by impaired mitochondrial function. In my second project, the effects of the absence of glutaredoxin-2 (Grx2) on redox homeostasis and on mitochondrial dynamics and energetics in cardiac muscle from mice were investigated. Previous work in our lab established that Grx2-deficient mice exhibit fibrotic cardiac hypertrophy, and hypertension, and that complex I of OXPHOS is defective in isolated mitochondria. Here we studied the role of Grx2 in the control of mitochondrial structure and function in intact cells and tissue, as well as the role of GRX2 in human heart disease. We demonstrated that the absence of Grx2 impacts mitochondrial fusion, ultrastructure and energetics in mouse primary cardiomyocytes and cardiac tissue and that provision of the glutathione precursor, N-acetylcysteine (NAC) did not restore glutathione redox or prevent impairments. Furthermore we used data from the human Genotype-Tissue Expression consortium to show that low GRX2 expression is associated with increased fibrosis, hypertrophy, and infarct in the left ventricle. Altogether, our results indicate that GRX2 plays a major role in cardiac mitochondrial structure and function, and protects against left ventricle pathologies in humans. In my third project, we collaborated with cardiac surgeon, Dr. Calum Redpath, of the Ottawa Heart Institute to study atrial mitochondrial metabolism in atrial fibrillation patients with and without type 2 diabetes (T2DM). T2DM is a major risk factor for atrial fibrillation, but the causes are poorly understood. Atrial appendages from coronary artery bypass graft surgery were collected and analyzed. We showed an impaired complex I respiration in diabetic patients with atrial fibrillation compared to diabetic patients without atrial fibrillation. In addition, and for the first time in atrial fibrillation patients, mitochondrial supercomplexes were studied; results showed no differences in the assembly of the "traditional" complexes but a decrease in the formation of "high oligomeric" complexes. A strong trend for increased protein oxidation was also observed. There were no changes in markers for OXPHOS protein levels. Overall findings reveal novel aspects of mitochondrial dysfunction in atrial fibrillation and diabetes in humans. Overall, our results reveal that in utero undernutrition affects the programming of skeletal muscle primary cells, thereby increasing susceptibility to metabolic diseases. In addition, we show that GRX2 impacts cardiac mitochondrial dynamics and energetics in both mice and humans. Finally, we show impaired mitochondrial function and supercomplex assembly in humans with atrial fibrillation and T2DM. Ultimately, understanding the mechanisms causing mitochondrial dysfunction in muscle tissues during chronic disease development will increase our capacity to identify effective prevention and treatment strategies.
Author: José Marín-García Publisher: Springer Science & Business Media ISBN: 0387255745 Category : Medical Languages : en Pages : 415
Book Description
Mitochondria have been pivotal in the development of some of the most important ideas in modern biology. Since the discovery that the organelle has its own DNA and specific mutations were found in association with neuromuscular and cardiovascular diseases and with aging, an extraordi-nary number of publications have followed, and the term mitochondrial medicine was coined. Furthermore, our understanding of the multiple roles that mitochondria play in cardiac cell homeostasis opened the door for intensive experimentation to understand the pathogenesis and to find new treatments for cardiovascular diseases. Besides its role in adenosine triphosphate generation, mitochondria regu-late a complex network of cellular interactions, involving (1) generation and detoxification of reactive oxygen species, including superoxide anion, hy-drogen peroxide, and hydroxyl radical; (2) maintenance of the antioxidant glutathione in a reduced state and adequate level of mitochondrial matrix superoxide dismutase; (3) cytoplasmic calcium homeostasis, particularly under conditions of cellular calcium loading; (4) transport of metabolites between cytoplasm and matrix; (5) both programmed (apoptosis) and necrotic cell death; and (6) cell growth and development. It is therefore not surprising that this organelle has come to be the center stage in many current investigations of cardiovascular diseases, aging, and agi- related disease. Concomitant with these advances, an impressive effort is under- way for the development of new tools and methodologies to study mitochondrial structure and function, including powerful ways to visualize, monitor, and alter the organelle function to assess the genetic consequences of these perturbations.
Author: Phung Nhat Thai Publisher: ISBN: 9781369616774 Category : Languages : en Pages :
Book Description
Cardiomyopathy, clinically manifest as congestive heart failure (HF), is characterized by abnormalities in cardiac mitochondrial function, including altered mitochondrial respiration, impaired production of ATP, increased reactive oxygen species (ROS) generation, elevated cellular apoptosis, and premature opening of the mitochondrial permeability transition pore (mPTP). The 18-kDa mitochondrial translocator protein (TSPO) has been shown to be involved in all said changes that occur during HF. Furthermore, prior research has found that this particular protein responds to stressful conditions, such as during neurological diseases, cancer formation, and even cardiovascular diseases, suggesting that it may have a role during HF. Although this protein has been shown to partake in cardiovascular diseases, surprisingly no research has explored it in the context of HF, the end stage of many cardiovascular diseases. To determine if the TSPO plays a role during heart failure, we subjected wild-type (WT) C57Bl/6J mice to 8 weeks of transverse aortic constriction (TAC), a pressure overload model of heart failure. We found that the TSPO expression level significantly increased during HF, which prompted us to explore if this response was adaptive or maladaptive. We therefore generated conditional, cardiac-specific knockout (KO) mice, and subjected them to the same HF condition. Using echocardiography, we found in vivo that the progression towards HF was much slower in KO mice. In addition to greater cardiac dilation, WT TAC mice also showed more severe signs of clinical manifestations of HF. To examine why knocking out the protein was adaptive during the progression towards HF, we investigated some of the proposed functions of the TSPO found in the literature: ROS production, mitochondrial calcium uptake, mPTP opening, ATP generation, and mitochondrial autophagy (mitophagy). We have demonstrated that with HF, there was diminished mitochondrial calcium uptake, more opening of mPTP opening, reduced energy production, overproduction of ROS, and impaired mitochondrial quality control. Knocking out the TSPO before TAC enhanced mitochondrial calcium uptake and energy production, limited ROS production, and improved mitophagy, ultimately improving cardiac function. Although further studies are needed to elucidate more specific mechanisms, these preliminary data suggest that the TSPO is a good candidate for drug therapy in the context of HF.
Author: Amanda R. Stram
Author: Amanda R. Stram
Author: Sebastiano Sciarretta
Author: Gregory Randall Wagner
Author: Gaetano Santulli
Author: Jose Guadalupe Gomez-Arroyo
Author: Edward Lau
Author: Georges Kanaan
Author: José Marín-García
Author: Lionel H. Opie
Author: Phung Nhat Thai