We recently characterized male DahlS.Z-Lepr fa /Lepr fa (Dahl salt-sensitive (DS)/obese) rats, which were established from a cross between Dahl salt-sensitive and Zucker rats, as a new animal model of metabolic syndrome (MetS). We have now investigated cardiac pathophysiology and metabolic changes in female DS/obese rats in comparison with homozygous lean female littermates (DahlS.Z-Lepr + /Lepr + , or DS/lean, rats). Animals were maintained on a normal diet and were subjected to echocardiography followed by various pathological analyses at 15 weeks of age. Systolic blood pressure was significantly higher in female DS/obese rats than in DS/lean females at 12 weeks of age and thereafter. The survival rate of DS/obese rats was significantly lower than that of DS/lean rats at 15 weeks. Body weight, as well as visceral and subcutaneous fat mass were significantly increased in DS/obese rats, which also manifested left ventricular (LV) diastolic dysfunction and marked LV hypertrophy and fibrosis. In addition, myocardial oxidative stress and inflammation were increased in DS/obese rats compared with DS/lean rats. Serum insulin and triglyceride levels as well as the ratio of low-density lipoprotein-to high-density lipoprotein-cholesterol levels were markedly elevated in DS/obese rats, whereas fasting serum glucose concentrations were similar in the two rat strains. The phenotype of female DS/obese rats is similar to that of MetS in humans. These animals also develop salt-sensitive hypertension and LV diastolic dysfunction as well as LV hypertrophy and fibrosis, and these changes are associated with increased cardiac oxidative stress and inflammation. Keywords: cardiac hypertrophy; diastolic dysfunction; metabolic syndrome; myocardial fibrosis; salt-sensitive hypertension INTRODUCTION Metabolic syndrome (MetS), a complex of highly debilitating disorders including hypertension, diabetes mellitus and dyslipidemia, is associated with the development of visceral obesity. 1 Adipocytes in visceral fat of obese humans secrete a variety of biological agents that are known as adipocytokines and include proinflammatory cytokines such as tumor necrosis factor (TNF)-a and interleukin (IL)-6 as well as angiotensinogen and leptin. 2 Recent studies have revealed intricate interactions among adipocytes, the sympathetic nervous system and the renin-angiotensin-aldosterone system (RAAS) that contribute to the disturbed metabolic state associated with obesity. 3 Indeed, adipose tissue is thought to have an important role in the development of both hypertension and other complications related to insulin resistance. Activation of the RAAS and associated oxidative stress can result in mitochondrial abnormalities, altered bioenergetics and the accumulation of lipids in the heart, and thereby increase susceptibility to metabolic cardiomyopathy. 4

Abstract-The clinical efficacy of exercise training in individuals with heart failure is well established, but the mechanism underlying such efficacy has remained unclear. An imbalance between cardiac hypertrophy and angiogenesis is implicated in the transition to heart failure. We investigated the effects of exercise training on cardiac pathophysiology in hypertensive rats. Dahl salt-sensitive rats fed a high-salt diet from 6 weeks of age were assigned to sedentary or exercise (swimming)-trained groups at 9 weeks. Exercise training attenuated the development of heart failure and increased survival, without affecting blood pressure, at 18 weeks. It also attenuated left ventricular concentricity without a reduction in left ventricular mass or impairment of cardiac function. Interstitial fibrosis was increased and myocardial capillary density was decreased in the heart of sedentary rats, and these effects were attenuated by exercise. Exercise potentiated increases in the phosphorylation of Akt and mammalian target of rapamycin observed in the heart of sedentary rats, whereas it inhibited the downregulation of proangiogenic gene expression apparent in these animals. The abundance of the p110␣ isoform of phosphatidylinositol 3-kinase was decreased, whereas those of the p110␥ isoform of phosphatidylinositol 3-kinase and the phosphorylation of extracellular signal-regulated kinase and p38 mitogen-activated protein kinase were increased, in the heart of sedentary rats, and all of these effects were prevented by exercise. Thus, exercise training had a beneficial effect on cardiac remodeling and attenuated heart failure in hypertensive rats, with these effects likely being attributable to the attenuation of left ventricular concentricity and restoration of coronary angiogenesis through activation of phosphatidylinositol 3-kinase ( Key Words: hypertension Ⅲ sodium-dependent Ⅲ heart failure Ⅲ exercise Ⅲ hypertrophy Ⅲ rats Ⅲ Dahl Ⅲ coronary angiogenesis .H eart failure is a final common consequence of various forms of heart disease and is a leading cause of mortality worldwide. Cardiac hypertrophy associated with pathological conditions such as hypertension, myocardial infarction, and valvular heart disease has been thought to be an adaptive response to increased external load, given that it can result in normalization of the increase in wall stress induced by mechanical overload. However, increased cardiac mass is also associated with increased morbidity and mortality, 1 with sustained overload eventually leading to heart failure.The serine-threonine protein kinase Akt is an important mediator of phosphatidylinositol 3-kinase (PI3K) signaling and regulates multiple cellular functions. 2 PI3K-Akt signaling is implicated in the regulation of cardiac growth, contractile function, and coronary angiogenesis. [3][4][5] A mismatch between the number of coronary capillaries and the size of cardiomyocytes, resulting in myocardial hypoxia, is thought to develop during the progression of cardiac hypertrophy. 6 Indeed, studies have in...

Objective:The DahlS.Z-Leprfa/Leprfa (DS/obese) rat strain was established from a cross between Dahl salt-sensitive rats and Zucker fatty (fa/fa) rats, the latter of which harbor a missense mutation in the leptin receptor gene (Lepr). We examined whether DS/obese rats might be a suitable animal model of metabolic syndrome in humans.Methods:The systemic pathophysiological and metabolic characteristics of DS/obese rats were determined and compared with those of homozygous lean littermates, namely, DahlS.Z-Lepr+/Lepr+ (DS/lean) rats.Results:Systolic blood pressure was higher in DS/obese rats fed a normal diet than in DS/lean rats at 11 weeks of age and thereafter. The survival rate of DS/obese rats was significantly lower than that of DS/lean rats at 18 weeks. Body weight, visceral and subcutaneous fat mass, as well as heart, kidney and liver weights, were increased in DS/obese rats at 18 weeks compared with DS/lean rats. Serum low-density lipoprotein (LDL)-cholesterol, triglyceride and insulin concentrations, as well as the ratio of LDL-cholesterol to high-density lipoprotein-cholesterol levels, were increased in DS/obese rats, whereas serum glucose concentration did not differ significantly between DS/obese and DS/lean rats. Creatinine clearance was decreased and urinary protein content was increased in DS/obese rats, which also manifested lipid accumulation in the liver and elevation of serum alanine aminotransferase levels.Conclusion:These results show that the phenotype of DS/obese rats is similar to that of humans with metabolic syndrome, and that these animals may thus be an appropriate model for this condition.

Cilnidipine attenuated LV fibrosis and diastolic dysfunction as well as LV concentricity to a greater extent than did amlodipine in Dahl salt-sensitive rats. The superior cardioprotective action of cilnidipine is likely attributable, at least in part, to the greater antioxidant and anti-inflammatory effects associated with inhibition of cardiac RAS gene expression observed with this drug.

Abstract-Although recent clinical trials have found an increased incidence of cardiovascular disease in women on estrogen replacement therapy, the underlying mechanism remains unclear. We have recently characterized DahlS.Z-Lepr fa /Lepr fa (DS/obese) rats, derived from a cross between Dahl salt-sensitive and Zucker rats, as a new animal model of metabolic syndrome. We have now examined the effects of estrogen replacement on cardiac pathophysiology in ovariectomized female DS/obese (Ovx-DS/obese) rats. Animals subjected to ovariectomy at 7 weeks of age were implanted subcutaneously with a 60-day release pellet containing 0.5 mg of 17␤-estradiol (E 2 ) or placebo at 8 weeks. Age-matched female homozygous lean littermates (DahlS.Z-Lepr ϩ /Lepr ϩ or DS/lean rats) of DS/obese rats served as controls. Animals were maintained on a normal diet and were subjected to echocardiography followed by various pathological analyses at 13 weeks of age. Ovx-DS/obese rats manifested hypertension at 7 weeks of age and thereafter and showed left ventricular (LV) fibrosis and diastolic dysfunction at 13 weeks. Treatment with E 2 attenuated hypertension in Ovx-DS/obese rats but had no effect on blood pressure in ovariectomized female DS/lean (Ovx-DS/lean) rats. E 2 treatment exacerbated LV fibrosis and diastolic dysfunction, as well as further increased cardiac oxidative stress and inflammation in Ovx-DS/obese rats, and it elicited similar effects in Ovx-DS/lean rats. E 2 reduced food intake, body weight, and visceral fat content in both Ovx-DS/obese and Ovx-DS/lean rats. E 2 treatment attenuated hypertension and obesity but exacerbated LV fibrosis and diastolic dysfunction in Ovx-DS/obese rats, with these latter effects being associated with increased cardiac oxidative stress and inflammation. (Hypertension. 2012;59:694-704.) • Online Data Supplement Key Words: metabolic syndrome Ⅲ estrogen Ⅲ hypertension Ⅲ myocardial fibrosis Ⅲ diastolic dysfunction Ⅲ oxidative stress Ⅲ inflammation M etabolic syndrome (MetS), a complex of highly debilitating disorders including hypertension, diabetes mellitus, and dyslipidemia, is associated with the development of visceral obesity. 1 MetS afflicts both men and women and increases the risk of heart disease in both sexes, although it appears to inflict a greater burden in women. The incidence of cardiovascular disease among women is low before menopause but steadily increases thereafter. 2 This increase is thought to result in part from the loss of endogenous estrogen and its associated cardioprotective effects. 3 A key issue faced by most postmenopausal women is the potential impact of estrogen replacement therapy on the prevalence of cardiovascular disease. Estrogen replacement in postmenopausal women has been associated with a reduced risk of cardiovascular disease. 4 However, the Heart and Estrogen/Progestin Replacement Study 5 and the Women's Health Initiative Study 6 do not support the notion that hormone replacement therapy protects the cardiovascular system but rather suggest the opposite vi...

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The mineralocorticoid aldosterone regulates sodium and water homeostasis in the human body. The combination of excess aldosterone and salt loading induces hypertension and cardiac damage. However, little is known of the effects of aldosterone on blood pressure and cardiac pathophysiology in the absence of salt loading. We have now investigated the effects of salt status and blockade of mineralocorticoid receptors (MRs) on cardiac pathophysiology in uninephrectomized Sprague-Dawley rats implanted with an osmotic minipump to maintain hyperaldosteronism. The rats were fed a low-salt (0.0466% NaCl in chow) or high-salt (0.36% NaCl in chow plus 1% NaCl in drinking water) diet in the absence or presence of treatment with a subdepressor dose of the MR antagonist spironolactone (SPL). Aldosterone excess in the setting of low salt intake induced substantial cardiac remodeling and diastolic dysfunction without increasing blood pressure. These effects were accompanied by increased levels of oxidative stress and inflammation as well as increased expression of genes related to the renin-angiotensin and endothelin systems in the heart. All of these cardiac changes were completely blocked by the administration of SPL. On the other hand, aldosterone excess in the setting of high salt intake induced hypertension and a greater extent of cardiac injury, with the cardiac changes being only partially attenuated by SPL in a manner independent of its antihypertensive effect. The combination of dietary salt restriction and MR antagonism is thus a promising therapeutic option for the management of hypertensive patients with hyperaldosteronism or relative aldosterone excess.

Although thiazide diuretics are commonly used to supplement angiotensin receptor blockers for treatment of hypertension, the mechanism underlying the therapeutic effects of this drug combination remains unclear. We investigated the antihypertensive and cardioprotective effects of combination therapy with losartan (LOS) and hydrochlorothiazide (HCTZ), in comparison with those of either drug alone, in Dahl salt-sensitive hypertensive rats. Rats fed a high-salt diet from 6 weeks of age were treated with LOS, HCTZ, both drugs (COMB) and vehicle from 6 to 11 weeks. The salt-induced increase in systolic blood pressure was attenuated moderately by LOS and to a greater extent by HCTZ and COMB. Left ventricular (LV) hypertrophy and fibrosis, diastolic dysfunction, as well as angiotensin-converting enzyme and angiotensin II type 1A (AT 1A ) receptor gene expression were attenuated similarly by LOS and HCTZ and more so by COMB. LOS downregulated expression of the AT 1A receptor gene, without affecting that of the AT 2 receptor gene, in the aorta. In contrast, neither HCTZ nor COMB affected aortic expression of the AT 1A receptor gene, but both markedly upregulated that of the AT 2 receptor gene. The salt-induced decrease in the plasma concentration of nitric oxide metabolites was attenuated substantially by LOS and abolished by both HCTZ and COMB. In conclusion, the combination of LOS and HCTZ attenuated hypertension, as well as LV remodeling and diastolic dysfunction, more effectively than did LOS or HCTZ alone in rats with salt-sensitive hypertension. Modulation of the cardiac and vascular renin-angiotensin system may have contributed to these beneficial effects of the drug combination.