Leonardo dos Santos

Circulating Dipeptidyl Peptidase IV Activity Correlates with Cardiac Dysfunction in Human and Experimental Heart Failure

Background—The present study addresses the hypothesis that the activity of dipeptidyl peptidase IV (DPPIV), an enzyme that inactivates peptides that possess cardioprotective actions, correlates with adverse outcomes in heart failure (HF). The therapeutic potential of DPPIV inhibition in preventing cardiac dysfunction is also investigated. Methods and Results—Measurements of DPPIV activity in blood samples obtained from 190 patients with HF and 42 controls demonstrated that patients with HF exhibited an increase of ≈130% in circulating DPPIV activity compared with healthy subjects. Furthermore, an inverse correlation was observed between serum DPPIV activity and left ventricular (LV) ejection fraction in patients with HF. Similarly, radiofrequency LV ablation-induced HF rats displayed higher DPPIV activity in the plasma (≈50%) and heart tissue (≈3.5-fold) compared with sham-operated rats. Moreover, positive correlations were observed between the plasma DPPIV activity and LV end-diastolic pressure and lung congestion. Two days after surgery, 1 group of LV ablation-induced HF rats was treated with the DPPIV inhibitor sitagliptin (40 mg/kg BID) for 6 weeks, whereas the remaining rats were administered water. Hemodynamic measurements demonstrated that radiofrequency LV-ablated rats treated with sitagliptin exhibited a significant attenuation of HF-related cardiac dysfunction, including LV end-diastolic pressure, systolic performance, and chamber stiffness. Sitagliptin treatment also attenuated cardiac remodeling and cardiomyocyte apoptosis and minimized pulmonary congestion. Conclusions—Collectively, the results presented herein associate circulating DPPIV activity with poorer cardiovascular outcomes in human and experimental HF. Moreover, the results demonstrate that long-term DPPIV inhibition mitigates the development and progression of HF in rats.

Repercussions of training and detraining by water-based exercise on functional fitness and quality of life: a short-term follow-up in healthy older women

OBJECTIVE: To evaluate the effects of short‐term exercise detraining on the functional fitness of older women after a 12‐week water‐based exercise (WE) program. METHODS: Healthy older women (trained (TR) group) were submitted to 12 weeks WE (three 45 min sessions per week) followed by a 6‐week detraining period. A group of aged‐matched women without any exercise training (UN group) were evaluated during the same period. The aerobic power, measured by VO2max and 800 meters performance, and the neuromuscular fitness and quality of life were evaluated. All assessments were made at baseline, after 12 weeks of training and after 4 and 6 weeks of detraining. RESULTS: No changes were found for the UN group during the follow‐up study, but WE induced significant improvement in aerobic capacity, neuromuscular fitness and quality of life score. However, the upper and lower body strength, agility, flexibility, and body balance returned to UN levels (p>0.05) after 6 weeks of detraining. CONCLUSIONS: The results confirmed that 12 weeks of WE improves the functional fitness parameters and quality of life of older women. However, after a short detraining period of 4–6 weeks, the neuromuscular parameters and the quality of life score returns to baseline or untrained subject levels.

Ouabain changes arterial blood pressure and vascular reactivity to phenylephrine in L-NAME-induced hypertension.

Ouabain is an endogenous compound that has been associated with the genesis and maintenance of hypertension. This compound inhibits the Na+ pump activity, which leads to an accumulation of intracellular Na+ and ultimately might increase vascular tone. In nanomolar concentrations, it enhances vasopressor responses to phenylephrine in some vascular beds from normotensive and hypertensive rats. However, it is not known whether this action of ouabain is a common mechanism for all models of hypertension. The aim of this work was to determine whether ouabain can alter pressor responses to phenylephrine in rats with Nω-nitro-l-arginine methyl ester (l-NAME)–induced hypertension. In anesthetized rats, ouabain (0.18 &mgr;g/kg, i.v.) increased arterial blood pressure in l-NAME–treated rats but not in controls. Ganglionic blockade by hexamethonium (5 mg/kg, i.v.) prevented the increase in arterial blood pressure produced by ouabain in l-NAME–treated rats. Additional studies using isolated perfused tail artery preparations were performed to investigate which factors are involved in the action of ouabain in l-NAME–treated rats. The effects of 10 n M ouabain on the vasoconstrictor actions of phenylephrine were determined on preparations with intact or damaged endothelium or in the presence of tetraethylammonium (a K+-channel blocker). Ouabain reduced pressor actions of phenylephrine in preparations with an intact endothelium. However, after endothelial damage or infusing tetraethylammonium, the response to phenylephrine was increased after ouabain. In tails from l-NAME–treated rats, the functional activity of the Na+, K+-ATPase was reduced, and 10 n M ouabain did not produce any further reduction. In conclusion, in this model of hypertension, a low dose of ouabain (0.18 &mgr;g/kg) increased arterial blood pressure in vivo probably as a result of increased sympathetic tone. However, this effect was not accompanied by an enhanced action of phenylephrine on the tail vascular bed with an intact endothelium. The results suggest that this was due to the release of an endothelium-derived K+-channel opener.

Increased NHE3 Abundance and Transport Activity in Renal Proximal Tubule of Rats with Heart Failure

Heart failure (HF) is associated with a reduced effective circulating volume that drives sodium and water retention and extracellular volume expansion. We therefore hypothesized that Na(+)/H(+) exchanger isoform 3 (NHE3), the major apical transcellular pathway for sodium reabsorption in the proximal tubule, is upregulated in an experimental model of HF. HF was induced in male rats by left ventricle radiofrequency ablation. Sham-operated rats (sham) were used as controls. At 6 wk after surgery, HF rats exhibited cardiac dysfunction with a dramatic increase in left ventricular end-diastolic pressure. By means of stationary in vivo microperfusion and pH-dependent sodium uptake, we demonstrated that NHE3 transport activity was significantly higher in the proximal tubule of HF compared with sham rats. Increased NHE3 activity was paralleled by increased renal cortical NHE3 expression at both protein and mRNA levels. In addition, the baseline PKA-dependent NHE3 phosphorylation at serine 552 was reduced in renal cortical membranes of rats with HF. Collectively, these results suggest that NHE3 is upregulated in the proximal tubule of HF rats by transcriptional, translational, and posttranslational mechanisms. Enhanced NHE3-mediated sodium reabsorption in the proximal tubule may contribute to extracellular volume expansion and edema, the hallmark feature of HF. Moreover, our study emphasizes the importance of undertaking a cardiorenal approach to contain progression of cardiac disease.

Chronic iron overload in rats increases vascular reactivity by increasing oxidative stress and reducing nitric oxide bioavailability.

AIMS Iron overload in animal models and humans increases oxidative stress and induces cardiomyopathy. It has been suggested that the vasculature is also damaged, but the impacts on vascular reactivity and the underlying mechanisms remain poorly understood. In this study, we aimed to identify possible changes in the vascular reactivity of aortas from iron overloaded rats and investigate the underlying mechanisms. MAIN METHODS Rats were treated with 100mg/kg/day iron-dextran, ip, five days a week for four weeks and compared to a saline-injected group. KEY FINDINGS Chronic iron administration increased serum iron and transferrin saturation with significant deposition in the liver. Additionally, iron overload significantly increased the vasoconstrictor response in aortic rings as assessed in vitro, with reduced influence of endothelial denudation or l-NAME incubation on the vascular reactivity. In vitro assay with DAF-2 indicated reduced NO production in the iron overload group. Iron overload-induced vascular hyperactivity was reversed by incubation with tiron, catalase, apocynin, allopurinol and losartan. Moreover, malondialdehyde was elevated in the plasma, and O2(•-) generation and NADPH oxidase subunit (p22phox) expression were increased in the aortas of iron-loaded rats. SIGNIFICANCE Our results demonstrated that chronic iron overload is associated with altered vascular reactivity and the loss of endothelial modulation of the vascular tone. This iron loading-induced endothelial dysfunction and reduced nitric oxide bioavailability may be a result of increased production of reactive oxygen species and local renin-angiotensin system activation.

Potential Role of Dipeptidyl Peptidase IV in the Pathophysiology of Heart Failure

Dipeptidyl peptidase IV (DPPIV) is a widely expressed multifunctional serine peptidase that exists as a membrane-anchored cell surface protein or in a soluble form in the plasma and other body fluids. Numerous substrates are cleaved at the penultimate amino acid by DPPIV, including glucagon-like peptide-1 (GLP-1), brain natriuretic peptide (BNP) and stromal cell-derived factor-1 (SDF-α), all of which play important roles in the cardiovascular system. In this regard, recent reports have documented that circulating DPPIV activity correlates with poorer cardiovascular outcomes in human and experimental heart failure (HF). Moreover, emerging evidence indicates that DPPIV inhibitors exert cardioprotective and renoprotective actions in a variety of experimental models of cardiac dysfunction. On the other hand, conflicting results have been found when translating these promising findings from preclinical animal models to clinical therapy. In this review, we discuss how DPPIV might be involved in the cardio-renal axis in HF. In addition, the potential role for DPPIV inhibitors in ameliorating heart disease is revised, focusing on the effects of the main DPPIV substrates on cardiac remodeling and renal handling of salt and water.

Myocardial remodeling after large infarcts in rat converts post rest-potentiation in force decay

Miocárdio Remodelado después de Grandes Infartos en Ratas Convierte Potenciación Post-pausa en Disminucion de la Fuerza Danilo Sales Bocalini1, Leonardo dos-Santos4, Ednei Luiz Antonio1, Alexandra Alberta dos Santos1, Ana Paula Davel3, Luciana Venturini Rossoni2, Dalton Valentim Vassallo5, Paulo José Ferreira Tucci1 Departamento de Medicina Divisão de Cardiologia Universidade Federal de São Paulo1; Departamento de Fisiologia e Biofísica Instituto de Ciências Biomédicas Universidade de São Paulo2, São Paulo, SP; Departamento de Biologia Estrutural e Funcional Instituto de Biologia Universidade Estadual de Campinas3, Campinas, SP; Departamento de Ciências Fisiológicas Universidade Federal do Espírito Santo4; Departamento de Ciências Morfofuncionais Escola Superior de Ciências da Santa Casa de Misericórdia5, Vitória, ES, BrasilBACKGROUND Post-rest contraction (PRC) of cardiac muscle provides indirect information about the intracellular calcium handling. OBJECTIVE Our aim was to study the behavior of PRC, and its underlying mechanisms, in rats with myocardial infarction. METHODS Six weeks after coronary occlusion, the contractility of papillary muscles (PM) obtained from sham-operated (C, n=17), moderate infarcted (MMI, n=10) and large infarcted (LMI, n=14) rats was evaluated, following rest intervals of 10 to 60 seconds before and after incubation with lithium chloride (Li(+)) substituting sodium chloride or ryanodine (Ry). Protein expression of SR Ca(2+)-ATPase (SERCA2), Na(+)/Ca(2+) exchanger (NCX), phospholamban (PLB) and phospho-Ser(16)-PLB were analyzed by Western blotting. RESULTS MMI exhibited reduced PRC potentiation when compared to C. Opposing the normal potentiation for C, post-rest decays of force were observed in LMI muscles. In addition, Ry blocked PRC decay or potentiation observed in LMI and C; Li(+) inhibited NCX and converted PRC decay to potentiation in LMI. Although MMI and LMI presented decreased SERCA2 (72±7% and 47±9% of Control, respectively) and phospho-Ser(16)-PLB (75±5% and 46±11%, respectively) protein expression, overexpression of NCX (175±20%) was only observed in LMI muscles. CONCLUSION Our results showed, for the first time ever, that myocardial remodeling after MI in rats may change the regular potentiation to post-rest decay by affecting myocyte Ca(2+) handling proteins.FUNDAMENTO: La Contraccion pos pausa (CPP) del musculo cardiaco provee informaciones indirectas sobre la manejo del calcio intracelular. OBJETIVO: Nuestro objetivo fue estudiar el comportamiento de la CPP y sus mecanismos subyacentes en Ratas con infarto de miocardio. METODOS: Seis semanas despues de la oclusion coronaria, la contractilidad de los Musculos Papilares (MP) obtenidos a partir de Ratas sometidos a falsa cirurgia (C, n = 17), con infarto moderado (MMI, n = 10) y gran infarto (LMI, n = 14), fue evaluada despues de pausas de estimulos de 10 a 60 segundos antes y despues de la incubacion con cloruro de litio (Li+) en substitucion del cloruro de sodio o rianodina (Ry). La expresion proteica de SR Ca(2+)-ATPasa (SERCA2), intercambiador Na+/Ca2+ (NCX), fosfolamban (PLB) y fosfo-Ser (16)-PLB fue analizada por Western blotting. RESULTADOS: Los Ratas MMI presentaron potenciacion de CPP reducida en comparacion a los Ratas C. En oposicion a la potenciacion normal para Ratas C, fueron observadas decaimientos de fuerza post-reposo en los musculos de Ratas LMI. Ademas de eso, la Ry bloqueo la decaimiento o potenciacion de PRC observada en Ratas LMI y C; el Li+ inhibio el NCX y convirtio la decaimiento en potenciacion de CPP en Ratas LMI. Aunque los Ratas MMI y LMI hayan presentado disminucion en el SERCA2 (72 ± 7% y 47 ± 9% de Ratas control, respectivamente) y expresion proteica de fosfo-Ser16-PLB (75 ± 5% y 46 ± 11%, respectivamente), la superexpresion del NCX (175 ± 20%) solo fue observada en los musculos de Ratas LMI. CONCLUSION: Nuestros resultados mostraron, por primera vez, que el remodelado miocardico post-IAM en Ratas puede cambiar la potenciacion regular para decaimiento post-reposo, afectando las proteinas de manejo del Ca(2+) en miocitos.

HYPERBARIC OXYGENATION APPLIED IMMEDIATELY AFTER CORONARY OCCLUSION REDUCES MYOCARDIAL NECROSIS AND ACUTE MORTALITY IN RATS

1 Because in ischaemia there is a critical lack of O2, it has been reasoned that increasing O2 delivery to the ischaemic myocardium could serve as adjunctive therapy for acute myocardial infarction (MI). Accordingly, in the present study, the effect of early hyperbaric oxygenation (HBO) on mortality and MI size after coronary occlusion was examined in rats. 2 After coronary occlusion, male Wistar rats were randomly assigned to receive either HBO for 1 h in a hyperbaric chamber (100% O2 at 253 kPa; n = 106) or ambient O2 as the control (n = 111). The extent of myocardial necrosis was assessed (triphenyltetrazolium) immediately after treatment in the HBO (n = 50) and control (n = 47) groups. The remaining rats were evaluated 24 h after occlusion to enable calculation of MI size and mortality. 3 Immediately after therapy, the size of the MI was significantly greater in the control group compared with that in the HBO group (40 ± 3 vs 27 ± 2% of the left ventricle (LV), respectively; P < 0.001). The 24 h mortality of control rats was higher than that of HBO rats (34 vs 16%, respectively; P = 0.02). Control rats that survived 24 h had a larger MI than did HBO rats that survived 24 h (40 ± 4 vs 29 ± 3% of the LV, respectively; P = 0.005). Furthermore, large necrotic areas (> 40% of the LV) were more frequent in control than HBO rats (55 vs 27% of infarcted hearts, respectively; P = 0.01). There was less pulmonary congestion observed in HBO rats compared with control rats. 4 In conclusion, early therapy with HBO during the onset of an acute ischaemic event decreases the necrotic area and reduces acute mortality. These data support further investigation of HBO as an adjuvant therapy for acute MI.

Acute iron overload leads to hypothalamic-pituitary-gonadal axis abnormalities in female rats.

Iron plays a critical role in a mammals physiological processes. However, iron tissue deposits have been shown to act as endocrine disrupters. Studies that evaluate the effect of acute iron overload on hypothalamic-pituitary-gonadal (HPG) axis health are particularly sparse. This study demonstrates that acute iron overload leads to HPG axis abnormalities, including iron accumulation and impairment in reproductive tract morphology. Female rats were treated with iron-dextran (Fe rats) to assess their HPG morphophysiology. The increasing serum iron levels due to iron-dextran treatment were positively correlated with higher iron accumulation in the HPG axis and uterus of Fe rats than in control rats. An increase in the production of superoxide anions was observed in the pituitary, uterus and ovary of Fe rats. Morphophysiological reproductive tract abnormalities, such as abnormal ovarian follicular development and the reduction of serum estrogen levels, were observed in Fe rats. In addition, a significant negative correlation was obtained between ovary superoxide anion and serum estrogen levels. Together, these data provide in vivo evidence that acute iron overload is toxic for the HPG axis, a finding that may be associated with the subsequent development of the risk of reproductive dysfunction.

The contributions of dipeptidyl peptidase IV to inflammation in heart failure

Circulating dipeptidyl peptidase IV (DPPIV) activity correlates with cardiac dysfunction in humans and experimental heart failure (HF) models. Similarly, inflammatory markers are associated with poorer outcomes in HF patients. However, the contributions of DPPIV to inflammation in HF remain elusive. Therefore, this study aimed to investigate whether the cardioprotective effects of DPPIV inhibition after myocardial injury are accompanied by reduced cardiac inflammation, whether circulating DPPIV activity correlates with the levels of systemic inflammatory markers in HF patients, and whether leukocytes and/or splenocytes may be one of the sources of circulating DPPIV in HF. Experimental HF was induced in male Wistar rats by left ventricular myocardial injury after radiofrequency catheter ablation. The rats were divided into three groups: sham, HF, and HF + DPPIV inhibitor (sitagliptin). Six weeks after surgery, cardiac function, perfusion and inflammatory status were evaluated. Sitagliptin treatment improved cardiac function and perfusion, reduced macrophage infiltration, and diminished the levels of inflammatory biomarkers including TNF-α, IL-1β, and CCL2. In HF patients, serum DPPIV activity correlated with CCL2, suggesting that leukocytes may be the source of circulating DPPIV in HF. Unexpectedly, DPPIV release was higher in splenocytes from HF rats and similar in HF circulating mononuclear cells compared with those from sham, suggesting an organ-specific modulation of DPPIV in HF. Collectively, our data provide new evidence that the cardioprotective effects of DPPIV inhibition in HF may be due to suppression of inflammatory cytokines. Moreover, they suggest that a vicious circle between DPPIV and inflammation may contribute to HF development and progression.