Neuroendocrine changes in chronic cardiac failure

Role of Vasoactive Hormone-Induced Signal Transduction in Cardiac Hypertrophy and Heart Failure

Heart failure is the common concluding pathway for a majority of cardiovascular diseases and is associated with cardiac dysfunction. Since heart failure is invariably preceded by adaptive or maladaptive cardiac hypertrophy, several biochemical mechanisms have been proposed to explain the development of cardiac hypertrophy and progression to heart failure. One of these includes the activation of different neuroendocrine systems for elevating the circulating levels of different vasoactive hormones such as catecholamines, angiotensin II, vasopressin, serotonin and endothelins. All these hormones are released in the circulation and stimulate different signal transduction systems by acting on their respective receptors on the cell membrane to promote protein synthesis in cardiomyocytes and induce cardiac hypertrophy. The elevated levels of these vasoactive hormones induce hemodynamic overload, increase ventricular wall tension, increase protein synthesis and the occurrence of cardiac remodeling. In addition, there occurs an increase in proinflammatory cytokines and collagen synthesis for the induction of myocardial fibrosis and the transition of adaptive to maladaptive hypertrophy. The prolonged exposure of the hypertrophied heart to these vasoactive hormones has been reported to result in the oxidation of catecholamines and serotonin via monoamine oxidase as well as the activation of NADPH oxidase via angiotensin II and endothelins to promote oxidative stress. The development of oxidative stress produces subcellular defects, Ca2+-handling abnormalities, mitochondrial Ca2+-overload and cardiac dysfunction by activating different proteases and depressing cardiac gene expression, in addition to destabilizing the extracellular matrix upon activating some metalloproteinases. These observations support the view that elevated levels of various vasoactive hormones, by producing hemodynamic overload and activating their respective receptor-mediated signal transduction mechanisms, induce cardiac hypertrophy. Furthermore, the occurrence of oxidative stress due to the prolonged exposure of the hypertrophied heart to these hormones plays a critical role in the progression of heart failure.

Future scope and challenges for congestive heart failure: Moving towards development of pharmacotherapy

Heart failure is invariably associated with cardiac hypertrophy and impaired cardiac performance. Although several drugs have been developed to delay the progression of heart failure, none of the existing interventions have shown beneficial effects in reducing morbidity and mortality. In order to determine specific targets for future drug development, we have discussed different mechanisms involving both cardiomyocytes and non-myocyte (extracellular matrix) alterations for the transition of cardiac hypertrophy to heart failure as well as for the progression of heart failure. We have emphasized the role of oxidative stress, inflammatory cytokines, metabolic alterations and Ca2+-handling defects in adverse cardiac remodeling and heart dysfunction in hypertrophied myocardium. Alterations in the regulatory process due to several protein kinases as well as participation of mitochondrial Ca2+-overload, activation of proteases and phospholipases and changes in gene expression for subcellular remodeling have also been described for the occurrence of cardiac dysfunction. Association of cardiac arrhythmia with heart failure has been explained as a consequence of catecholamine oxidation products. Since these multifactorial defects in extracellular matrix and cardiomyocytes are evident in the failing heart, it is a challenge for experimental cardiologists to develop appropriate combination drug therapy for improving cardiac function in heart failure.

Physical Performance and Non-Esterified Fatty Acids in Men and Women after Transcatheter Aortic Valve Implantation (TAVI)

Background: Men and women with valvular heart disease have different risk profiles for clinical endpoints. Non-esterified fatty acids (NEFA) are possibly involved in cardio-metabolic disease. However, it is unclear whether NEFA concentrations are associated with physical performance in patients undergoing transcatheter aortic valve implantation (TAVI) and whether there are sex-specific effects. Methods: To test the hypothesis that NEFA concentration is associated with sex-specific physical performance, we prospectively analysed data from one hundred adult patients undergoing TAVI. NEFA concentrations, physical performance and anthropometric parameters were measured before and 6 and 12 months after TAVI. Physical performance was determined by a six-minute walking test (6-MWT) and self-reported weekly bicycle riding time. Results: Before TAVI, NEFA concentrations were higher in patients (44 women, 56 men) compared to the normal population. Median NEFA concentrations at 6 and 12 months after TAVI were within the reference range reported in the normal population in men but not women. Men but not women presented with an increased performance in the 6-MWT over time (p = 0.026, p = 0.142, respectively). Additionally, men showed an increased ability to ride a bicycle after TAVI compared to before TAVI (p = 0.034). NEFA concentrations before TAVI correlated with the 6-MWT before TAVI in women (Spearman’s rho −0.552; p = 0.001) but not in men (Spearman’s rho −0.007; p = 0.964). No association was found between NEFA concentrations and physical performance 6 and 12 months after TAVI. Conclusions: NEFA concentrations improved into the reference range in men but not women after TAVI. Men but not women have an increased physical performance after TAVI. No association between NEFA and physical performance was observed in men and women after TAVI.

Oxidative Stress as A Mechanism for Functional Alterations in Cardiac Hypertrophy and Heart Failure

Although heart failure due to a wide variety of pathological stimuli including myocardial infarction, pressure overload and volume overload is associated with cardiac hypertrophy, the exact reasons for the transition of cardiac hypertrophy to heart failure are not well defined. Since circulating levels of several vasoactive hormones including catecholamines, angiotensin II, and endothelins are elevated under pathological conditions, it has been suggested that these vasoactive hormones may be involved in the development of both cardiac hypertrophy and heart failure. At initial stages of pathological stimuli, these hormones induce an increase in ventricular wall tension by acting through their respective receptor-mediated signal transduction systems and result in the development of cardiac hypertrophy. Some oxyradicals formed at initial stages are also involved in the redox-dependent activation of the hypertrophic process but these are rapidly removed by increased content of antioxidants in hypertrophied heart. In fact, cardiac hypertrophy is considered to be an adaptive process as it exhibits either normal or augmented cardiac function for maintaining cardiovascular homeostasis. However, exposure of a hypertrophied heart to elevated levels of circulating hormones due to pathological stimuli over a prolonged period results in cardiac dysfunction and development of heart failure involving a complex set of mechanisms. It has been demonstrated that different cardiovascular abnormalities such as functional hypoxia, metabolic derangements, uncoupling of mitochondrial electron transport, and inflammation produce oxidative stress in the hypertrophied failing hearts. In addition, oxidation of catecholamines by monoamine oxidase as well as NADPH oxidase activation by angiotensin II and endothelin promote the generation of oxidative stress during the prolonged period by these pathological stimuli. It is noteworthy that oxidative stress is known to activate metallomatrix proteases and degrade the extracellular matrix proteins for the induction of cardiac remodeling and heart dysfunction. Furthermore, oxidative stress has been shown to induce subcellular remodeling and Ca²⁺-handling abnormalities as well as loss of cardiomyocytes due to the development of apoptosis, necrosis, and fibrosis. These observations support the view that a low amount of oxyradical formation for a brief period may activate redox-sensitive mechanisms, which are associated with the development of cardiac hypertrophy. On the other hand, high levels of oxyradicals over a prolonged period may induce oxidative stress and cause Ca²⁺-handling defects as well as protease activation and thus play a critical role in the development of adverse cardiac remodeling and cardiac dysfunction as well as progression of heart failure.

Chromogranin A - unspecific neuroendocrine marker. Clinical utility and potential diagnostic pitfalls

Chromogranin A, despite a number of limitations, is still the most valuable marker of neuroendocrine tumors (NETs). Granins belong to the family of acidic proteins that constitute a major component of secretory granules of various endocrine and neuroendocrine cells, which are components of both the classical endocrine glands and the diffuse neuroendocrine system. These cells are a potential source of transformation into neuroendocrine tumors. The awareness of potential causes influencing the false results of its concentrations simplifies diagnosis and treatment. One of the disadvantages of this marker is its non-specificity and the existence of a number of pathological processes leading to an increase in its concentration, which often results in confusion and diagnostic difficulties. The molecular structure is characterized by a number of sites susceptible to the proteolytic activity of enzymes, resulting in the formation of a number of biologically active peptides. Presumably they act as precursors of active proteins. Chromogranin expression correlates with the amount of secretory vesicles in neuroendocrine cells. The peptide chain during biochemical changes becomes a precursor of biologically active proteins with a wide range of activities. There are a number of commercially available kits for the determination of chromogranin A, which differ in methodology. We present the evaluation of chromogranin A as a marker of neuroendocrine tumors in clinical practice and the possible factors that may affect the outcome of its concentration.