Sandra Ballesteros

Leptin induces cardiac fibrosis through galectin-3, mtor and oxidative stress: potential role in obesity

Objective: Leptin acts as a cardiac profibrotic factor. However, the mechanisms underlying this effect are unclear. Therefore, we sought to elucidate the mediators involved in this process and the potential role of leptin in cardiac fibrosis associated with obesity. Methods: Male Wistar rats were fed either a high-fat diet (HFD; 33.5% fat), or a standard diet (3.5% fat) for 6 weeks. Results: HFD animals show cardiac hypertrophy, fibrosis and an increase in O2- production as evaluated by dihydroethidium. Echocardiographic parameters of cardiac structure and systolic function were similar in both groups. Cardiac levels of leptin, collagen I, galectin-3 and transforming growth factor &bgr; (TGF-&bgr;) were higher in HFD than in controls. In cardiac myofibroblasts, leptin (10–100 ng/ml) increased O2−, collagen I, galectin-3, TGF-&bgr; and connective tissue growth factor production (CTGF). These effects were prevented by the presence of either melatonin (10−3 mmol/l) or the inhibitor of mTOR, rapamycin (10−4 mmol/l). Blockage of galectin-3 activity by N-acetyllactosamine (LacNac 10−3 mmol/l) reduced both collagen I and O2.− production induced by leptin. The p70S6 kinase activation/phosphorylation, the downstream mediator of mTOR, induced by leptin was not modified by melatonin. Leptin reduced the metalloproteinase (MMP) 2 activity and the presence of melatonin, rapamycin or LacNac were unable to prevent it. Conclusion: The data suggest that leptin locally produced in the heart could participate in the fibrosis observed in HFD by affecting collagen turnover. Collagen synthesis induced by leptin seems to be mediated by the production of galectin-3, TGF-&bgr; and CTGF through oxidative stress increased by activation of mTOR pathway.

Aldosterone and the vascular system

Aldosterone can act in different tissues exerting physiological and pathological effects. At the vascular level, aldosterone affects endothelial function since administration of aldosterone impaired endothelium-dependent relaxations. In addition, the administration of mineralocorticoid receptor antagonists ameliorate relaxation to acetylcholine in models of both hypertension and atherosclerosis and in patients with heart failure. A reduction in nitric oxide levels seems to be the main mechanism underlying this effect due to a reduction in its production as well as an increase in its degradation by reactive oxygen species. Aldosterone is a pro-inflammatory factor that can participate in the vascular inflammatory process associated with different pathologies including hypertension through activation of the NFkappaB system, which mediates the vascular production of different cytokines. This mineralocorticoid also participates in the vascular remodeling observed in hypertensive rats since the administration of eplerenone improved the media-to-lumen ratio in these animals. This effect seems to be due to an increase in extracellular matrix. In summary, aldosterone through mineralocorticoid receptors can participate in the vascular damage associated with different pathologies including hypertension through its prooxidant, pro-inflammatory and profibrotic effects that triggered endothelial dysfunction, an inflammatory process and vascular remodeling.

The protective effect of irbesartan in rats fed a high fat diet is associated with modification of leptin-adiponectin imbalance.

Objective It has been shown that the renin–angiotensin system participates in the development of the metabolic syndrome. This study aimed to show whether the angiotensin II type 1 receptor blocker, irbesartan, exerts a protective effect against metabolic and cardiovascular abnormalities in rats fed a high fat diet (HFD). Methods Wistar rats (n = 30) were divided into three groups: (1) rats fed a standard diet for 7 weeks were used as a control group; (2) rats fed a HFD (33.5% fat) for 7 weeks; and (3) rats fed a HFD (33.5% fat) treated with irbesartan (0.1 mg/kg per day) for 7 weeks. Body weight, white and brown adipose tissue weight, plasma concentrations and protein expression of leptin and adiponectin in white adipose tissue, and glucose metabolism were investigated. Vascular reactivity in aortic rings and heart function were also evaluated. Results HFD rats showed increased (P < 0.05) body, epididymal and lumbar adipose tissue weights, but did not experience a change in brown adipose tissue weight. Irbesartan attenuated (P < 0.05) all of these parameters, but increased brown adipose tissue weight. The leptin/adiponectin ratio of plasma concentrations and protein expression in lumbar adipose tissue increased (P < 0.05) in HFD rats, and were normalized by irbesartan. Along with these changes, irbesartan improved (P < 0.05) insulin sensitivity and exaggerated responses to angiotensin I and II in the aorta. Conclusion Irbesartan reduced body and white adipose tissue weights, improved glucose metabolism and vascular function in the aorta. The correction of leptin–adiponectin imbalance may be an important mechanism participating in the protective effect of irbesartan in HFD rats.

Inflammation: A Link Between Hypertension and Atherosclerosis

High blood pressure levels are associated with increases in circulating levels of inflammation markers which can reflect vascular inflammatory processes, suggesting that hypertension is a low-grade inflammatory process. The vascular inflammation associated with hypertension could be the link between high blood pressure levels and the atherosclerotic process, which is the principal origin of cardiovascular disease, the leading cause of worldwide mortality. High blood pressure levels are accompanied by increases in oxidative stress due to both higher reactive oxygen specie (ROS) production and reduced ROS scavenging by antioxidant defence. This situation favours endothelial function alterations which allow the expression of adhesion molecules and initiation of fatty streak, the earliest structural change in the atherosclerotic process. At the same time, this inflammation, allows endothelial dysfunction since some inflammatory mediators can negatively affect endothelial cell function. Inflammation, therefore, plays a critical role in development and in complications of the atherothrombotic process. Changes in mechanical stress and activation of humoral factors such as the reninangiotensin- aldosterone system can be underlying not only increases in oxidative stress (and consequently endothelial dysfunction) but also the development of the inflammatory process associated with hypertension.

Factors involved in rosuvastatin induction of insulin sensitization in rats fed a high fat diet.

BACKGROUND AND AIM To investigate whether rosuvastatin can improve insulin sensitivity in overweight rats having a high fat diet (HFD). The potential mechanisms involved in this action were evaluated, including SIRT-1, other factors involved in glucose metabolism and stress signaling pathways. METHODS AND RESULTS Male Wistar rats (n = 30) were divided into three groups: (i) rats fed a standard diet (3.5% fat); (ii) rats fed a HFD (33.5% fat); and (iii) rats fed a HFD and treated with rosuvastatin (15 mg/kg/day). Evolution: 7 weeks. HFD rats showed increased body, epididymal and lumbar adipose tissue weights. Plasma levels of cholesterol, triglycerides, VLDL, glucose and insulin and leptin/adiponectin ratio were higher in HFD rats, and rosuvastatin treatment reduced them. SIRT-1, p53, PGC-1α, PPAR-γ and GLUT-4 protein levels in white adipose tissue (WAT) were lower, and JNK was higher in HFD rats compared to controls. Rosuvastatin treatment normalized expression of these mediators. Endothelium-dependent relaxation was reduced in mesenteric rings from HFD rats compared to controls and rosuvastatin enhanced it in HFD rats. CONCLUSION Rosuvastatin treatment reduced insulin resistance without affecting body weight or WAT loss in HFD rats. Reduction of leptin and JNK, and enhancement of SIRT-1, p53, PGC-1α, PPAR-γ and GLUT-4 expression in WAT could contribute to insulin sensitization. Normalization of SIRT-1 expression in WAT could be considered a key novel mechanism that aids in explaining the beneficial effects of rosuvastatin on the amelioration of glucose metabolism and the arrangement of multiple signaling pathways participating in insulin resistance in overweight HFD rats.

Cardiac L-type calcium current is increased in a model of hyperaldosteronism in the rat

Accumulating evidence supports the importance of aldosterone as an independent risk factor in the pathophysiology of cardiovascular disease. It has been postulated that aldosterone could contribute to ventricular arrhythmogeneity by modulation of cardiac ionic channels. The aim of this study was to analyse ex vivo the electrophysiological characteristics of the L‐type cardiac calcium current (ICaL) in a model of hyperaldosteronism in the rat. Aldosterone was administered for 3 weeks, and cardiac collagen deposition and haemodynamic parameters were analysed. In addition, RT‐PCR and patch‐clamp techniques were applied to study cardiac L‐type Ca2+ channels in isolated cardiomyocytes. Administration of aldosterone induced maladaptive cardiac remodelling that was related to increased collagen deposition, diastolic dysfunction and cardiac hypertrophy. In addition, ventricular myocytes isolated from the aldosterone‐treated group showed increased ICaL density and conductance and prolongation of the action potential duration. No changes in kinetics or in voltage dependence of activation and inactivation of ICaL were observed, but relative expression of CaV1.2 mRNA levels was higher in cardiomyocytes isolated from the aldosterone‐treated group. The present study demonstrates that aldosterone treatment induces myocardial fibrosis, cardiac hypertrophy, increase of ICaL density, upregulation of L‐type Ca2+ channels and prolongation of action potential duration. It could be proposed that aldosterone, through these mechanisms, might exert pro‐arrhythmic effects in the pathological heart.

Structural, functional, and molecular alterations produced by aldosterone plus salt in rat heart: association with enhanced serum and glucocorticoid-regulated kinase-1 expression.

We aimed to evaluate the structural, functional, inflammatory, and oxidative alterations, as well as serum and glucocorticoid-regulated kinase-1 (SGK-1) expression, produced in rat heart by aldosterone + salt administration. Fibrosis mediators such as connective tissue growth factor, matrix metalloproteinase 2, and tissue inhibitor of metalloproteinases 2 were also evaluated. Treatment with spironolactone was evaluated to prove mineralocorticoid mediation. Male Wistar rats received aldosterone (1 mg·kg−1·d−1) + 1% NaCl for 3 weeks. Half of the animals were treated with spironolactone (200 mg·kg−1·d−1). Systolic and diastolic blood pressures, left ventricle (LV) systolic pressure, and LV end-diastolic pressure were elevated (P < 0.05) in aldosterone + salt-treated rats. In aldosterone + salt-treated rats, -dP/dt decreased (P < 0.05), but +dP/dt was similar in all groups. Spironolactone normalized (P < 0.05) systolic blood pressure, diastolic blood pressure, LV systolic pressure, LV end-diastolic pressure, and -dP/dt. Relative heart weight, collagen content, messenger RNA expression of transforming growth factor beta, connective tissue growth factor, matrix metalloproteinase 2, tissue inhibitor of metalloproteinases 2, tumor necrosis factor alpha, interleukin-1β, p22phox, endothelial nitric oxide synhtase, and SGK-1 were increased (P < 0.05) in aldosterone + salt-treated rats, being reduced by spironolactone (P < 0.05). SGK-1 might be a key mediator in the structural, functional, and molecular cardiac alterations induced by aldosterone + salt in rats. All the observed changes and mediators are related with the activation of mineralocorticoid receptors.

Aldosterone Induces Renal Fibrosis and Inflammatory M1-Macrophage Subtype via Mineralocorticoid Receptor in Rats

We aimed to evaluate macrophages heterogeneity and structural, functional and inflammatory alterations in rat kidney by aldosterone + salt administration. The effects of treatment with spironolactone on above parameters were also analyzed. Male Wistar rats received aldosterone (1 mgkg-1d-1) + 1% NaCl for 3 weeks. Half of the animals were treated with spironolactone (200 mg kg-1d-1). Systolic and diastolic blood pressures were elevated (p<0.05) in aldosterone + salt–treated rats. Relative kidney weight, collagen content, fibronectin, macrophage infiltrate, CTGF, Col I, MMP2, TNF-α, CD68, Arg2, and SGK-1 were increased (p<0.05) in aldosterone + salt–treated rats, being reduced by spironolactone (p<0.05). Increased iNOS and IFN-γ mRNA gene expression (M1 macrophage markers) was observed in aldosterone + salt rats, whereas no significant differences were observed in IL-10 and gene ArgI mRNA expression or ED2 protein content (M2 macrophage markers). All the observed changes were blocked with spironolactone treatment. Macrophage depletion with liposomal clodronate reduced macrophage influx and inflammatory M1 markers (INF-γ or iNOS), whereas interstitial fibrosis was only partially reduced after this intervention, in aldosterone plus salt-treated rats. In conclusion, aldosterone + salt administration mediates inflammatory M1 macrophage phenotype and increased fibrosis throughout mineralocorticoid receptors activation.

Spironolactone prevents alterations associated with cardiac hypertrophy produced by isoproterenol in rats: involvement of serum‐ and glucocorticoid‐regulated kinase type 1

Persistent β‐adrenergic receptor stimulation with isoproterenol is associated with cardiac hypertrophy as well as cardiac synthesis of angiotensin II. Serum‐ and glucocorticoid‐regulated kinase type 1 (SGK‐1) is a key mediator in structural, functional and molecular cardiac effects of aldosterone in rats. This study was designed to investigate the cardiac effects of the mineralocorticoid receptor antagonist spironolactone on the response to isoproterenol treatment in rats, as well as the involvement of the main mediator of cellular aldosterone action, SGK‐1, in the heart. Male Wistar rats received isoproterenol (3 mg kg−1 day−1) or vehicle for 15 days. Half of the animals in each group were simultaneously treated with spironolactone (200 mg kg−1 day−1). Systolic and diastolic blood pressures were not significantly different among groups. Treatment with spironolactone normalized the increased left ventricular end‐diastolic pressure observed in isoproterenol‐treated rats. Isoproterenol treatment induced cardiac hypertrophy and increased collagen content, both of which were normalized by spironolactone treatment. The mRNA levels of transforming growth factor β, connective tissue growth factor, matrix metalloprotease 2, matrix metalloprotease inhibitor 2, tumour necrosis factor α, interleukin 1β, p22phox and xanthine dehydrogenase were increased (P < 0.05) in isoproterenol‐treated rats, and this effect was prevented by spironolactone (P < 0.05). Spironolactone also reduced the elevated SGK‐1 expression in isoproterenol‐treated rats. The observed reduction of the principal mediator of aldosterone cellular actions, SGK‐1, by spironolactone in hearts from isoproterenol‐treated rats suggests a role of mineralocorticoids in the cardiac hypertrophy, fibrosis, inflammation, oxidation and diastolic dysfunction induced by isoproterenol treatment in rats.

Protective effect of a pomace olive oil concentrated in triterpenic acids in alterations related to hypertension in rats: mechanisms involved.

SCOPE Despite the amount of information and research on the effects of virgin olive oil and its components in cardiovascular disease, little attention has been paid to the effects of pomace olive oil, an olive oil subproduct traditionally used in Spain. The aim of the present study was to evaluate the potential effects of a pomace olive oil concentrated in triterpenic acids (POCTA) on blood pressure, cardiac hemodynamics, and functional and molecular vascular alterations associated with hypertension in spontaneously hypertensive rats (SHR). METHODS AND RESULTS The study showed that POCTA attenuated the increase of blood pressure in SHR. This effect was associated with an improvement in endothelium-dependent relaxation, enhancement of vascular expression of endothelial nitric oxide synthase, and reduction of tumor necrosis factor alpha, transforming growth factor beta, and collagen I. Furthermore, POCTA improved cardiac hemodynamics (left ventricular systolic pressure and left ventricular end-diastolic pressure) and decreased relative kidney and lung weights. CONCLUSION POCTA exerts antihypertensive effects together with vascular and hypertension target organ protection in SHR. Since interest in pomace olive oil has been low, the results of this study contribute to increasing awareness of its biological and nutritional values.