Low-intensity aerobic exercise improves cardiac remodelling of adult spontaneously hypertensive rats.

We evaluated the influence of aerobic training on cardiac remodeling in untreated spontaneously hypertensive rats (SHR). Four experimental groups were used: sedentary (W-SED, n=27) and trained (WEX, n=31) normotensive Wistar rats, and sedentary (SHR-SED, n=27) and exercised (SHR-EX, n=32) hypertensive rats. At 13 months old, trained groups underwent treadmill exercise five days a week for four months. Statistical analysis: ANOVA or Kruskal-Wallis. Exercised groups had higher physical capacity. Hypertensive groups presented left ventricular (LV) concentric hypertrophy with impaired function. Left atrium diameter, LV posterior wall thickness and relative thickness, and isovolumetric relaxation time were lower in SHR-EX than SHR-SED. Interstitial collagen fraction and Type I-Type III collagen ratio were higher in SHR-SED than W-SED. In SHR-EX these parameters had intermediate values between W-EX and SHRSED with no differences between either group. Myocardial matrix metalloproteinase-2 activity, evaluated by zymography, was higher in SHR-SED than W-SED and SHR-EX. TIMP-2 was higher in hypertensive than normotensive groups. In conclusion, low intensity aerobic exercise reduces left atrium dimension and LV posterior wall thickness, and improves functional capacity, diastolic function, and metalloproteinase-2 activity in adult SHR.

Exercise during transition from compensated left ventricular hypertrophy to heart failure in aortic stenosis rats.

We evaluated the influence of aerobic exercise on cardiac remodelling during the transition from compensated left ventricular (LV) hypertrophy to clinical heart failure in aortic stenosis (AS) rats. Eighteen weeks after AS induction, rats were assigned into sedentary (AS) and exercised (AS-Ex) groups. Results were compared to Sham rats. Exercise was performed on treadmill for 8 weeks. Exercise improved functional capacity. Echocardiogram showed no differences between AS-Ex and AS groups. After exercise, fractional shortening and ejection fraction were lower in AS-Ex than Sham. Myocyte diameter and interstitial collagen fraction were higher in AS and AS-Ex than Sham; however, myocyte diameter was higher in AS-Ex than AS. Myocardial oxidative stress, evaluated by lipid hydroperoxide concentration, was higher in AS than Sham and was normalized by exercise. Gene expression of the NADPH oxidase subunits NOX2 and NOX4, which participate in ROS generation, did not differ between groups. Activity of the antioxidant enzyme superoxide dismutase was lower in AS and AS-Ex than Sham and glutathione peroxidase was lower in AS-Ex than Sham. Total and reduced myocardial glutathione, which is involved in cellular defence against oxidative stress, was lower in AS than Sham and total glutathione was higher in AS-Ex than AS. The MAPK JNK was higher in AS-Ex than Sham and AS groups. Phosphorylated P38 was lower in AS-Ex than AS. Despite improving functional capacity, aerobic exercise does not change LV function in AS rats. Exercise restores myocardial glutathione, reduces oxidative stress, impairs JNK signalling and further induces myocyte hypertrophy.

N-Acetylcysteine Influence on Oxidative Stress and Cardiac Remodeling in Rats During Transition from Compensated Left Ventricular Hypertrophy to Heart Failure.

BACKGROUND/AIMS: To evaluate the effects of the antioxidant N-acetylcysteine (NAC) on cardiac structure and function in rats with long-term ascending aortic stenosis (AS). METHODS: Four months after inducing AS, Wistar rats were assigned into the groups Sham, AS, and AS treated with NAC (AS-NAC) and followed for eight weeks. Cardiac structure and function were evaluated by echocardiogram. Myocardial antioxidant enzymes activity was measured by spectrophotometry and malondialdehyde serum concentration by HPLC. Gene expression of NADPH oxidase subunits NOX2, NOX4, p22 phox, and p47 phox was assessed by real time RT-PCR and protein expression of MAPK proteins by Western blot. Statistical analyzes were performed with Goodman and ANOVA or Mann-Whitney Results: NAC restored myocardial total glutathione (Sham 20.8±3.00; AS 12.6±2.92; AS-NAC 17.6±2.45 nmol/g tissue; p<0.05 AS vs Sham and AS-NAC). Malondialdehyde serum concentration was lower in AS-NAC and myocardial lipid hydroperoxide was higher in AS (Sham 199±48.1; AS 301±36.0; AS-NAC 181±41.3 nmol/g tissue). Glutathione peroxidase activity was lower in AS than Sham. Echocardiogram showed LV concentric hypertrophy with systolic and diastolic dysfunction before and after treatment; no differences were observed between AS-NAC and AS groups. NAC reduced p-ERK and p-JNK protein expression, attenuated myocardial fibrosis, and decreased the frequency of right ventricular hypertrophy. CONCLUSION: N-acetylcysteine restores myocardial total glutathione, reduces systemic and myocardial oxidative stress, improves MAPK signaling, and attenuates myocardial fibrosis in aortic stenosis rats.

Modulation of MAPK and NF-954;B Signaling Pathways by Antioxidant Therapy in Skeletal Muscle of Heart Failure Rats.

BACKGROUND/AIMS: Although increased oxidative stress plays a role in heart failure (HF)-induced skeletal myopathy, signaling pathways involved in muscle changes and the role of antioxidant agents have been poorly addressed. We evaluated the effects of N-acetylcysteine (NAC) on intracellular signaling pathways potentially modulated by oxidative stress in soleus muscle from HF rats. METHODS AND RESULTS: Four months after surgery, rats were assigned to Sham, myocardial infarction (MI)-C (without treatment), and MI-NAC (treated with N-acetylcysteine) groups. Two months later, echocardiogram showed left ventricular dysfunction in MI-C; NAC attenuated diastolic dysfunction. Oxidative stress was evaluated in serum and soleus muscle; malondialdehyde was higher in MI-C than Sham and did not differ between MI-C and MI-NAC. Oxidized glutathione concentration in soleus muscle was similar in Sham and MI-C, and lower in MI-NAC than MI-C (Sham 0.168 ± 0.056; MI-C 0.223 ± 0.073; MI-NAC 0.136 ± 0.023 nmol/mg tissue; p = 0.014). Western blot showed increased p-JNK and decreased p38, ERK1/2, and p-ERK1/2 in infarcted rats. NAC restored ERK1/2. NF-954;B p65 subunit was reduced; p-Ser276 in p65 and I954;B was increased; and p-Ser536 unchanged in MI-C compared to Sham. NAC did not modify NF-954;B p65 subunit, but decreased p-Ser276 and p-Ser536. CONCLUSION: N-acetylcysteine modulates MAPK and NF-954;B signaling pathways in soleus muscle of HF rats.

Early Spironolactone Treatment Attenuates Heart Failure Development by Improving Myocardial Function and Reducing Fibrosis in Spontaneously Hypertensive Rats.

BACKGROUND: We evaluated the role of the aldosterone blocker spironolactone in attenuating long-term pressure overload-induced cardiac remodeling and heart failure (HF) in spontaneously hypertensive rats (SHR). METHODS AND RESULTS: Thirteen month-old male SHR were assigned to control (SHR-C, n=20) or spironolactone (SHR-SPR, 20 mg/kg/day, n=24) groups for six months. Normotensive Wistar-Kyoto rats (WKY, n=15) were used as controls. Systolic blood pressure was higher in SHR groups and unchanged by spironolactone. Right ventricular hypertrophy, which characterizes HF in SHR, was less frequent in SHR-SPR than SHR-C. Echocardiographic parameters did not differ between SHR groups. Myocardial function was improved in SHR-SPR compared to SHR-C [developed tension: WKY 4.85±0.68; SHR-C 5.22±1.64; SHR-SPR 6.80±1.49 g/mm2; -dT/dt: WKY 18.0 (16.0­19.0); SHR-C 20.8 (18.4­25.1); SHR-SPR 28.9 (24.2­34.6) g/mm2/s]. Cardiomyocyte cross-sectional area and total collagen concentration (WKY 1.06±0.34; SHR-C 1.85±0.63; SHR-SPR 1.28±0.39 µg/mg wet tissue) were greater in SHR-C than WKY and SHR-SPR. Type 3 collagen expression was lower in SHR-C than WKY and unchanged by spironolactone. Soluble collagen, type I collagen, and lysyl oxidase did not differ between groups. CONCLUSION: Early spironolactone treatment decreases heart failure development frequency by improving myocardial systolic and diastolic function and attenuating hypertrophy and fibrosis in spontaneously hypertensive rats.

Long-term low intensity physical exercise attenuates heart failure development in aging spontaneously hypertensive rats.

BACKGROUND: Physical exercise is a strategy to control hypertension and attenuate pressure overload-induced cardiac remodeling. The influence of exercise on cardiac remodeling during uncontrolled hypertension is not established. We evaluated the effects of a long-term low intensity aerobic exercise protocol on heart failure (HF) development and cardiac remodeling in aging spontaneously hypertensive rats (SHR). METHODS: Sixteen month old SHR (n=50) and normotensive Wistar-Kyoto (WKY, n=35) rats were divided into sedentary (SED) and exercised (EX) groups. Rats exercised in treadmill at 12 m/min, 30 min/day, 5 days/week, for four months. The frequency of HF features was evaluated at euthanasia. STATISTICAL ANALYSES: ANOVA and Tukey or Mann-Whitney, and Goodman test. RESULTS: Despite slightly higher systolic blood pressure, SHR-EX had better functional capacity and lower HF frequency than SHR-SED. Echocardiography and tissue Doppler imaging showed no differences between SHR groups. In SHR-EX, however, left ventricular (LV) systolic diameter, larger in SHR-SED than WKY-SED, and endocardial fractional shortening, lower in SHR-SED than WKY-SED, had values between those in WKY-EX and SHR-SED not differing from either group. Myocardial function, assessed in LV papillary muscles, showed improvement in SHR-EX over SHR-SED and WKY-EX. LV myocardial collagen fraction and type I and III collagen gene expression were increased in SHR groups. Myocardial hydroxyproline concentration was lower in SHR-EX than SHR-SED. Lysyl oxidase gene expression was higher in SHR-SED than WKY-SED. CONCLUSION: Exercise improves functional capacity and reduces decompensated HF in aging SHR independent of elevated arterial pressure. Improvement in functional status is combined with attenuation of LV and myocardial dysfunction and fibrosis.

Influence of N- acetylcysteine on oxidative stress in slow-twitch soleus muscle of heart failure rats.

BACKGROUND: Chronic heart failure is characterized by decreased exercise capacity with early exacerbation of fatigue and dyspnea. Intrinsic skeletal muscle abnormalities can play a role in exercise intolerance. Causal or contributing factors responsible for muscle alterations have not been completely defined. This study evaluated skeletal muscle oxidative stress and NADPH oxidase activity in rats with myocardial infarction (MI) induced heart failure. METHODS AND RESULTS: Four months after MI, rats were assigned to Sham, MI-C (without treatment), and MI-NAC (treated with N-acetylcysteine) groups. Two months later, echocardiogram showed left ventricular dysfunction in MI-C; NAC attenuated diastolic dysfunction. In soleus muscle, glutathione peroxidase and superoxide dismutase activity was decreased in MI-C and unchanged by NAC. 3-nitrotyrosine was similar in MI-C and Sham, and lower in MI-NAC than MI-C. Total reactive oxygen species (ROS) production was assessed by HPLC analysis of dihydroethidium (DHE) oxidation fluorescent products. The 2-hydroxyethidium (EOH)/DHE ratio did not differ between Sham and MI-C and was higher in MI-NAC. The ethidium/DHE ratio was higher in MI-C than Sham and unchanged by NAC. NADPH oxidase activity was similar in Sham and MI-C and lower in MI-NAC. Gene expression of p47(phox) was lower in MI-C than Sham. NAC decreased NOX4 and p22(phox) expression. CONCLUSIONS: We corroborate the case that oxidative stress is increased in skeletal muscle of heart failure rats and show for the first time that oxidative stress is not related to increased NADPH oxidase activity.

Aldosterone blockade reduces mortality without changing cardiac remodeling in spontaneously hypertensive rats.

BACKGROUND: The role of aldosterone blockers during transition from long-term compensated hypertrophy to dilated failure is not completely understood. In this study we evaluated the effects of early administration of spironolactone on cardiac remodeling, myocardial function, and mortality in spontaneously hypertensive rats (SHR). METHODS: Sixteen-month-old SHR received no treatment (SHR-C, n=72) or spironolactone (SHR-SPR, 20 mg/kg/day, n=34) for six months. Echocardiogram was performed before and after treatment. Myocardial function was analyzed in left ventricular (LV) papillary muscle preparations. Myocardial collagen and hydroxyproline concentration were evaluated by morphometry and spectrophotometry, respectively. LV gene expression was assessed by real time RT-PCR. STATISTICS: Student's t test; Log rank test (Kaplan Meyer). RESULTS: SHR-C and SHR-SPR presented mortality rates of 71 and 38%, respectively (p=0.004). Systolic arterial pressure did not differ between groups (SHR-C 199±43; SHR-SPR 200±35 mmHg). Initial and final echocardiograms did not show significant differences in cardiac structures or LV function between groups. Myocardial function was similar between groups at basal and after inotropic stimulation. Collagen fractional area, hydroxyproline concentration, gene expression for α- and ß-myosin heavy chain, atrial natriuretic peptide, and Serca2a were not different between groups. CONCLUSION: Early spironolactone administration reduces mortality without changing cardiac remodeling in spontaneous hypertensive rats.

Combined exercise training in asymptomatic elderly with controlled hypertension: effects on functional capacity and cardiac diastolic function.

BACKGROUND: Aging is associated with changes in cardiac structure and function that are associated with left ventricular diastolic dysfunction. Whether diastolic functional alterations during senescence are manifestations of the intrinsic aging process or related to cardiac adaptations to a more sedentary lifestyle is still unsettled. This was a prospective study evaluating the effects of a 6-month combined exercise training period on functional capacity and diastolic function in sedentary elderly patients with controlled arterial hypertension. MATERIAL/METHODS: Functional capacity was assessed by exercise stress test and muscle strength was evaluated by the one-repetition maximum test. Cardiac structures and function were analyzed by transthoracic echocardiography. RESULTS: Fifteen patients, 68±8 years old, completed the training program. Exercise training significantly improved physical capacity (distance walked: 551±92 vs. 630±153 m, P<0.05; work load: 7.2±1.7 vs. 8.5±3.0 METs, P<0.05) and upper and lower extremity muscle strength (P<0.001). Arterial blood pressure significantly decreased after training (systolic blood pressure: 134±9 vs. 128±8 mmHg; diastolic blood pressure: 82±7 vs. 77±6 mmHg; P<0.05). Cardiac structures and left and right systolic and diastolic function did not change after combined training (P>0.05). CONCLUSIONS: Combined and supervised training for a 6-month period increases physical capacity and muscle strength in elderly patients with controlled arterial hypertension without changing resting left ventricular diastolic function.

Aerobic Exercise During Advance Stage of Uncontrolled Arterial Hypertension.

AIM: To evaluate the influence of physical training on myocardial function, oxidative stress, energy metabolism, and MAPKs and NF-κB signaling pathways in spontaneously hypertensive rats (SHR), at advanced stage of arterial hypertension, which precedes heart failure development. METHODS: We studied four experimental groups: normotensive Wistar rats (W, n = 27), trained W (W-EX, n = 31), SHR (n = 27), and exercised SHR (SHR-EX, n = 32). At 13 months old, the exercise groups underwent treadmill exercise 5 days a week for 4 months. In vitro myocardial function was analyzed in left ventricular (LV) papillary muscle preparations. Antioxidant enzyme activity and energy metabolism were assessed by spectrophotometry. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity was analyzed by lucigenin reduction and protein expression by Western blot. Statistical analyzes: ANOVA and Tukey or Kruskal-Wallis and Dunn tests. RESULTS: SHR-EX had a lower frequency of heart failure features than SHR. Myocardial function and antioxidant enzyme activity were better in SHR-EX than SHR. Lipid hydroperoxide concentration, and phosphorylated JNK and total IkB protein expression were higher in hypertensive than control groups. Malondialdehyde, NADPH oxidase activity, total JNK, phosphorylated p38, phosphorylated and total p65 NF-κB, and phosphorylated IkB did not differ between groups. Protein expression from total p38, and total and phosphorylated ERK were higher in SHR than W. Lactate dehydrogenase and phosphorylated ERK were lower and citrate synthase and ß-hydroxyacyldehydrogenase were higher in SHR-EX than SHR. CONCLUSION: Exercise improves physical capacity, myocardial function, and antioxidant enzyme activity; reduces the frequency of heart failure features and ERK phosphorylation; and normalizes energy metabolism in SHR.

Chronic heart failure-induced skeletal muscle atrophy, necrosis, and changes in myogenic regulatory factors.

BACKGROUND: Although intrinsic skeletal muscle abnormalities can influence exercise intolerance during heart failure (HF), the factors responsible for muscle changes have not been elucidated. In this study we evaluated the expression of myogenic regulatory factors (MRF), myosin heavy chain (MyHC) isoforms, and fiber trophism in the soleus muscle of rats with myocardial infarction-induced heart failure. METHOD/RESULTS: Six months after surgery, 2 groups of rats were studied: sham, and infarcted rats with HF (MI/HF+, MI size: 41.1±6.3% of total left ventricular area). In the infarcted group, microscopic evaluation revealed scattered foci of fiber necrosis in combination with inflammatory cells, phagocytosis, and increased fibrous tissue. The frequency of necrotic fibers was significantly higher in the MI/HF+ group than in the sham. The MI/HF+ group had atrophy of type I, IC/IIC, and IIA fibers compared to the sham group (P<0.05). MyoD gene expression was higher in the MI/HF+ group (sham: 1.00±0.49; MI/HF+: 2.53±0.71 arbitrary units; P<0.001). Myogenin and MRF4 gene expression was similar in both groups. Myogenin protein levels were reduced in the MI/HF+ group (sham: 1.00±0.21; MI/HF+: 0.74±0.21 arbitrary units; P=0.026). MyoD and MRF4 protein levels, as well as the MyHC distribution, were not different between groups. The MI/HF+ group had higher TNF-α and IL-6 serum concentrations than the sham group. CONCLUSIONS: Heart failure-induced skeletal muscle atrophy is combined with fiber necrosis, increased MyoD gene expression and decreased myogenin protein levels.

Effects of growth hormone on cardiac remodeling and soleus muscle in rats with aortic stenosis-induced heart failure.

BACKGROUND: Skeletal muscle wasting is often observed in heart failure (HF). The growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis is impaired in HF. In this study, we evaluated the effects of GH on soleus muscle and cardiac remodeling in rats with aortic stenosis (AS)-induced HF. METHODS: AS was created by placing a stainless-steel clip on the ascending aorta. After clinically detecting HF, GH (2 mg/kg/day) was subcutaneously injected for 14 days (AS-GH group). Results were compared with those from Sham and non-treated AS groups. Transthoracic echocardiogram was performed before and after treatment. Protein expression was evaluated by Western blot and satellite cells activation by immunofluorescence. Statistical analyzes: ANOVA and Tukey or Kruskal-Wallis and Student-Newman-Keuls. RESULTS: Before treatment both AS groups presented a similar degree of cardiac injury. GH prevented body weight loss and attenuated systolic dysfunction. Soleus cross-sectional fiber areas were lower in both AS groups than Sham (Sham 3,556±447; AS 2,882±422; AS-GH 2,868±591 µm2; p=0.016). GH increased IGF-1 serum concentration (Sham 938±83; AS 866±116; AS-GH 1167±166 ng/mL; p<0.0001) and IGF-1 muscle protein expression and activated PI3K protein. Neural cell adhesion molecule (NCAM) immunofluorescence was increased in both AS groups. Catabolism-related intracellular pathways did not differ between groups. CONCLUSION: Short-term growth hormone attenuates left ventricular systolic dysfunction in rats with aortic stenosis-induced HF. Despite preserving body weight, increasing serum and muscular IGF-1 levels, and stimulating PI3K muscle expression, GH does not modulate soleus muscle trophism, satellite cells activation or intracellular pathways associated with muscle catabolism.

Effects of late exercise on cardiac remodeling and myocardial calcium handling proteins in rats with moderate and large size myocardial infarction.

BACKGROUND: Physical exercise attenuates myocardial infarction (MI)-induced cardiac remodeling. However, it is unsettled whether late exercise modulates post-infarction cardiac remodeling differentially according to infarct size. We investigated the effects of exercise started at late stage heart failure on cardiac remodeling in rats with moderate and large sized MI. METHODS: Three months after MI, rats were assigned into sedentary and exercise groups. Exercise rats underwent treadmill for three months. After assessing infarct size by histological analysis, rats were subdivided into four groups: moderate MI sedentary (Mod MI-Sed; n=7), Mod MI exercised (Mod MI-Ex; n=7), Large MI-Sed (n=11), and Large MI-Ex (n=10). RESULTS: Before exercise, MI-induced cardiac changes were demonstrated by comparing results to a Sham group; alterations were more intense in rats with large than moderate MI size. Systolic function, evaluated by echocardiogram using the variation in LV fractional area change between after and before exercise, was improved in exercise than sedentary groups. Calsequestrin expression increased in exercised compared to sedentary groups. L-type calcium channel was higher in Mod MI-Ex than Mod MI-Sed. SERCA2a, phospholamban, and Na(+)/Ca(2+) exchanger expression did not differ between groups. CONCLUSION: Late exercise improves systolic function and modulates intracellular calcium signaling proteins in rats with moderate and large MI.

Echocardiographic detection of congestive heart failure in postinfarction rats.

In studies of congestive heart failure (CHF) treatment, it is essential to select animals with a similar degree of cardiac dysfunction. However, this is difficult to establish without hemodynamic evaluation in rat postinfarction-induced CHF. This study aimed to diagnose CHF in long-term follow-up postinfarction rats using only echocardiographic criteria through a J-tree cluster analysis and Fisher's linear discriminant function. Two sets of sham and infarcted rats were studied. The first was used to perform cluster analysis and the second to prospectively validate the results. Six months after inducing myocardial infarction (MI), rats were subjected to transthoracic echocardiography. Infarct size was measured by histological analysis. Six echocardiographic variables were used in the cluster analysis: left ventricular (LV) systolic dimension, LV diastolic dimension-to-body weight ratio, left atrial diameter-to-body weight ratio, LV posterior wall shortening velocity, E wave, and isovolumetric relaxation time. Cluster analysis joined the rats into one sham and two MI groups. One MI cluster had more severe anatomical and echocardiographic changes and was called MI with heart failure (MI/HF+, n = 24, infarct size: 42.7 ± 5.8%). The other had less severe changes and was called MI without heart failure (MI/HF-, n = 11, infarct size: 32.3 ± 9.9%; P < 0.001 vs. MI/HF+). Three rats with small infarct size (21.6 ± 2.2%) presenting mild cardiac alterations were misallocated in the sham group. Fisher's linear discriminant function was built using these groups and used to prospectively classify additional groups of sham-operated (n = 20) and infarcted rats (n = 57) using the same echocardiographic parameters. The discriminant function therefore detected CHF with 100% specificity and 80% sensitivity considering allocation in MI/HF+ and sham group, and 100% specificity and 58.8% sensitivity considering MI/HF+ and MI/HF- groups, taking into account pathological criteria of CHF diagnosis. Echocardiographic analysis can be used to accurately predict congestive heart failure in postinfarction rats.