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A moderate carnitine deficiency exacerbates isoproterenol-induced myocardial injury in rats
No full textPurpose: The myocardium is largely dependent upon oxidation of fatty acids for the production of ATP. Cardiac contractile abnormalities and failure have been reported after acute emotional stress and there is evidence that catecholamines are responsible for acute stress-induced heart injury. We hypothesized that carnitine deficiency increases the risk of stress-induced heart injury.
Methods: Carnitine deficiency was induced in Wistar rats by adding 20 mmol/L of sodium pivalate to drinking water (P). Controls (C) received equimolar sodium bicarbonate and a third group (P + Cn) received pivalate along with 40 mmol/L carnitine. After 15 days, 6 rats/group were used to evaluate function of isolated hearts under infusion of 0.1 μM isoproterenol and 20 rats/group were submitted to a single subcutaneous administration of 50 mg/kg isoproterenol.
Results: Isoproterenol infusion in C markedly increased the heart rate, left ventricular (LV) systolic pressure and coronary flow rate. In P rats, isoproterenol increased the heart rate and LV systolic pressure but these increases were not paralleled by a rise in the coronary flow rate and LV diastolic pressure progressively increased. Subcutaneous isoproterenol induced 15 % mortality rate in C and 50 % in P (p < 0.05). Hearts of surviving P rats examined 15 days later appeared clearly dilated, presented a marked impairment of LV function and a greater increase in tumor necrosis factor α (TNFα) levels. All these detrimental effects were negligible in P + Cn rats.
Conclusions: Our study suggests that carnitine deficiency exposes the heart to a greater risk of injury when sympathetic nerve activity is greatly stimulated, for example during emotional, mental or physical stress
Carnitine, mitochondrial function and therapy
No full textCarnitine is important for cell function and survival primarily because of its involvement in the multiple equilibria between acylcarnitine and acyl-CoA esters established through the enzymatic activities of the family of carnitine acyltransferases. These have different acyl chain-length specificities and intracellular compartment distributions, and act in synchrony to regulate multiple aspects of metabolism, ranging from fuel-selection and -sensing, to the modulation of the signal transduction mechanisms involved in many homeostatic systems. This review aims to rationalise the extensive range of experimental and clinical data that have been obtained through the pharmacological use of L-carnitine and its short-chain acylesters, over the past two decades, in terms of the basic biochemical mechanisms involved in the effects of carnitine on the various cellular acyl-CoA pools in health and disease. (C) 2009 Elsevier B.V. All rights reserved
Increased platelet phosphatidylserine exposure and caspase activation in chronic uremia
No full textPlatelet activation is associated with exposure of the aminophospholipid phosphatidylserine (PS) to the outer hemi-leaflet of the plasma membrane bilayer, which seems to be involved in the coagulation process. Because platelet activation may occur in patients suffering from chronic uremia, which is frequently associated with a thrombophilic tendency, we studied whether uremic platelets show an increased propensity to expose PS on the outer membrane leaflet and whether this process is linked with important functional and molecular changes. Flow cytometric percentage of annexin V-positive platelets, a measure of PS externalization, was significantly elevated (P < 0.001) in uremic patients when compared to normal controls under both unstimulated and agonist-stimulated conditions. Uremic platelet procoagulant activity, as measured by thrombin generation, was more than twice as high (4.13 +/- 0.3 micro mL(-1)) as that found in normal controls (1.86 +/- 0.2 micro mL(-1)). Two independent assays showed that the enzymatic activity of caspase-3, a protease involved in the loss of membrane PS asymmetry, was significantly greater in the platelets of uremic subjects than in those of healthy controls. PS exposure in agonist-stimulated platelets was markedly reduced by inhibition of caspase-3 activity but was not affected by inhibition of calpain activity. These results support the view that the thrombophilic susceptibility of uremic patients may be partly ascribed to increased PS exposure to the outer membrane leaflet of platelets. This process seems to be causally linked to an increase in caspase-3 activity, particularly during platelet activation
Involvement of phosphatidylserine exposure in the recognition and phagocytosis of uremic erythrocytes
No full textCell surface-exposed phosphatidylserine (PS) represents a signal for macrophage recognition and cell phagocytosis. This study examines PS exposure and susceptibility to erythrocyte phagocytosis in patients with chronic uremia in an attempt to assess the possible pathogenic mechanism behind cell removal in a condition associated with shortened erythrocyte life. Both PS-expressing erythrocytes and erythrophagocytosis (human monocyte-derived macrophages ingesting one or more erythrocytes) were significantly increased in uremic patients compared with healthy controls. Phagocytosed uremic erythrocytes appeared intact, suggesting they were identified before lysis through some surface change recognized by the macrophages. The degree of phagocytosis was markedly greater for PS-positive than PS-negative fluorescence-activated cell sorter (FACS)-sorted uremic erythrocytes. A significant correlation (r = 0.655) was found between the percentage of PS-expressing red blood cells (RBCs) and the percentage of phagocytosing macrophages in uremic patients. Reconstitution experiments showed the ability of uremic plasma to promote both PS exposure and erythrophagocytosis, the latter without direct interaction with the macrophage population. Phagocytosis of uremic erythrocytes was strongly inhibited when the macrophages were preincubated with glycerophosphorylserine (GPS), a structural derivative of PS, but this was not the case with the equivalent derivative of phosphatidylethanolamine, glycerophosphorylethanolamine. This inhibition appeared to be specific because GPS failed to inhibit the phagocytosis of opsonized uremic erythrocytes that occurs through an Fc receptor-mediated pathway. These findings suggest that a PS-recognition mechanism may promote the susceptibility of uremic RBCs to phagocytosis and thus be involved in the shortened erythrocyte life span of uremia
Effect of ischemia and reperfusion on antioxidant enzymes and mitochondrial inner membrane proteins in perfused rat heart.
No full textAbstract- Experiments were performed to investigate the effects of 60 min severe global ischemia followed by 30 min reperfusion on the antioxidant enzymatic system in the isolated perfused rat heart. Ischemia induced a significant increase of cytoplasmic and mitochondrial selenium-dependent glutathione peroxidase (EC 1.11.1.9) activity. In reperfused hearts, only the mitochondrial form showed a further significant increase. Glutathione reductase (EC 1.6.4.2) was increased in ischemic hearts, whilst the reperfused hearts showed a decrease towards the level found in aerobic hearts. Mitochondrial superoxide dismutase (EC 1.15.1.1) activity was depressed in ischemic as well as in reperfused hearts, though the cytoplasmic form was unmodified. Catalase (EC 1.11.1.6), glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and glutathione transferase (EC 2.5.1.18) activities were unchanged throughout the experiment. Ischemia and reperfusion induced a significant fall in tissue-reduced glutathione content concomitant with an increase of its oxidized form. We have also studied the mitochondrial inner membrane proteins for both molecular weight, with Coomassie blue, and thiol status, with monobromobimane stain, using a sodium dodecyl sulfate polyacrylamide gel electrophoresis technique. Neither ischemia nor reperfusion effected any relevant modification of the molecular weight of the mitochondrial inner-membrane proteins either in the presence or absence of a reducing agent. However, two of these proteins with an apparent molecular weight of 52,0000 and 12,000 showed a decrease in the monobromobimane stain, probably due to the oxidation of their thiol groups
Quali soluzioni future per la dialisi peritoneale?
Full text linkLa dialisi peritoneale è una efficace tecnica sostitutiva della funzione renale nel paziente uremico, tuttavia è generalmente sotto-utilizzata. Ciò è almeno in parte attribuibile agli effetti sfavorevoli su integrità e funzione peritoneale (bioincompatibilità) delle attuali soluzioni a base di glucosio. L’uso delle soluzioni standard può indurre nel peritoneo diverse alterazioni quali infiammazione, transizione mesotelio-mesemchima e neoangiogenesi. Lo stadio finale è rappresentato dalla fibrosi, che causa una
riduzione della capacità di filtrazione peritoneale che può arrivare alla completa insufficienza ultrafiltrativa con necessità di passare all’emodialisi. Oltre che locale (peritoneo) la bioincompatibilità può anche essere sistemica per l’eccessivo assorbimento di glucosio presente nel dialisato. Diverse strategie sono state impiegate per migliorare la biocompatibilità delle soluzioni per dialisi peritoneale, sulla base dei suggeriti fattori causali. Le soluzioni disponibili in commercio alternative alle standard includono quelle con bassi livelli di prodotti di degradazione del glucosio e pH neutro e quelle con
icodestrina o aminoacidi. Tali soluzioni possono offrire alcuni benefici clinici ma hanno alcune limitazioni e la loro biocompatibilità è oggetto di discussione. Strategie più recenti includono l’uso nel dialisato di agenti citoprotettivi o di agenti osmo-metabolici. In questo lavoro vengono presi in esame i diversi approcci allo sviluppo di nuove soluzioni per dialisi peritoneale, atti a migliorare l’outcome clinico del paziente e la sopravvivenza della tecnica, di possibile impiego in un futuro auspicabilmente prossimo
Mechanisms of action of SGLT2 inhibitors and their beneficial effects on the cardiorenal axis
No full textLarge clinical studies conducted with sodium-glucose co-transporter 2 inhibitors (SGLT2i) in patients with type 2 diabetes and heart failure with reduced ejection fraction have demonstrated their ability to achieve both cardiac and kidney benefits. Although there is huge evidence on SGLT2i-mediated clinical benefits both in diabetic and non-diabetic patients, the pathophysiological mechanisms underlying their efficacy are still poorly understood. Some favorable mechanisms are likely due to the prompt glycosuric action which is associated with natriuretic effects leading to hemodynamic benefits as well as a reduction in glomerular hyperfiltration and renin-angiotensin-aldosterone system activation. In addition to the renal mechanisms, SGLT2i may play a relevant role in cardiorenal axis protection by improving the cardiomyocyte metabolism, by exerting anti-fibrotic and anti-inflammatory actions, and by increasing cardioprotective adipokine expression. New studies will be needed to better understand the specific molecular mechanisms that mediate the SGLT2i favorable effects in patients suffering diabetes. Our aim is to first discuss about the molecular mechanisms underlying the cardiovascular benefits of SGLT2i in each of the main organs involved in the cardiorenal axis. Furthermore, we update on the most recent clinical trials evaluating the beneficial effects of SGLT2i in treatment of both diabetic and non-diabetic patients suffering heart failure
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