Exercise training in aging: hemodynamic, metabolic, and oxidative stress evaluations

Age- and Phenotype-Dependent Changes in Circulating MMP-2 and MMP-9 Activities in Normotensive and Hypertensive Rats

Matrix metalloproteinases (MMPs) are important in the pathogenesis of numerous diseases. The present study aimed to monitor the activation of MMP-2 and MMP-9 in spontaneously hypertensive rats (SHR) and their normotensive counterparts-Wistar-Kyoto rats (WKY). The animals were divided according to age (7, 20, and 52 weeks) and phenotype into: WKY-7, WKY-20, WKY-52, SHR-7, SHR-20 and SHR-52 groups. MMP plasma activities were determined by gelatine zymography. We monitored selected parameters of oxidative stress and antioxidant status. N-terminal pro-brain natriuretic peptide (NT-proBNP) was determined as a marker of heart function and neurohumoral activation. SHR-7 showed higher MMP-2 activity compared with WKY-7, while SHR-52 showed lower MMP-2 and MMP-9 activities compared with WKY-52. Examining age-dependent changes in MMP activities, we found a decrease in MMP-2 activity and increase in MMP-9 activity with increasing age in both phenotypes. Parameters of oxidative stress and antioxidant status as well as NT-proBNP levels were not significantly worsened due to aging in SHR. Our results suggest that hypertension is accompanied by varying MMP activation during aging. The results of our study may indicate that MMP-2 inhibition is therapeutically applicable during the development of hypertension, while in developed, stabilized and uncomplicated hypertension, systemic MMP-2 and MMP-9 inhibition may not be desirable.

Exercise capacity in different stages of hypertension in spontaneously hypertensive rats

BACKGROUND

The aim of the present study was to investigate the exercise capacity of hypertensive rats at different stages of development of hypertension and to determine the most suitable index to evaluate the exercise capacity in different strains.

METHODS

Male spontaneously hypertensive rat (SHR) and normotensive Wistar rats (NWR) of 5, 8, 12 and 16 weeks were submitted to the exercise capacity test. The exercise running time was measured and the workload was calculated.

RESULTS

Normotensive and hypertensive rats when assess the exercise capacity by exercise running time exhibited a reduction in exercise performance over time. Moreover, hypertensive rats showed lower exercise capacity compared to normotensive control when analyzed by workload.

CONCLUSIONS

The present results indicate that hypertensive rats exhibit reduced exercise capacity compared to normotensive rats regardless of age assessed. Beside that, in experiments with strains with different body mass the most reliable index to assess exercise capacity is workload.

Exercise training initiated at old stage of lifespan attenuates aging-and ovariectomy-induced cardiac and renal oxidative stress: Role of baroreflex

BACKGROUND

The association of aging and menopause is a potent risk factor for cardiometabolic disease. We studied the impact of aerobic exercise training (ET) initiated in the old stage of lifespan in hemodynamics, metabolic, autonomic and oxidative stress.

METHODS

Aged (18 months old) female Wistar rats were divided into: ovariectomized and untrained (AG-OVX), and ovariectomized and trained (AG-OVXt, ET for 8 weeks). Intact aged (AG) and young female rats (3 months old; Y) were also studied. Blood pressure and metabolic parameters were measured. Baroreflex sensitivity (BRS) was studied by bradycardic (BR) and tachycardic (TR) responses to vasoactive drugs. Cardiac and renal lipid peroxidation (LPO), catalase (CAT), superoxide dismutase (SOD) and gluthatione peroxidase (GPx), and gluthatione redox balance (GSH/GSSG) were analyzed.

RESULTS

AG-OVXt group increased aerobic performance in 35%, decreased adipose tissue and triglycerides in 36% and 27%, respectively, and improved insulin tolerance in 50% in comparison to AG-OVX. AG-OVX presented hypertensive levels of blood pressure (systolic: 155 ± 5, diastolic: 111 ± 3 mmHg). In contrast, AG-OVXt presented blood pressure values similar to Y rats (systolic: 129 ± 3, diastolic: 112 ± 3 mmHg). TR and BR were reduced by 70% and 46%, respectively, in AG-OVX vs. Y. Once more, AG-OVXt presented similar results to Y. ET decreased LPO in the heart and kidney. In the latter, renal CAT and SOD were corrected by ET, while cardiac redox balance was partially recovered. Improved BRS was correlated with improved oxidative stress markers.

CONCLUSIONS

Even when initiated after aging and ovariectomy deleterious effects, ET is able to normalize BRS and highly improve cardiac and renal oxidative stress.

Moderate Treadmill Exercise Training Improves Cardiovascular and Nitrergic Response and Resistance to Trypanosoma cruzi Infection in Mice

There is evidence suggesting that exercise training (ET) acts as a factor toward resistance to Trypanosoma cruzi infection. However, the effects of mean arterial pressure (MAP), heart rate (HR), and nitric oxide (NO) during the acute phase of infection has not been elucidated yet. Swiss mice were randomly assigned into four groups: sedentary control (SC, n = 30), trained control (TC, n = 30), sedentary infected (SI, n = 30), and trained infected (TI, n = 30). ET was performed on the treadmill for 9 weeks. After training, the mice were infected with 5 × 10³ trypomastigotes of T. cruzi (Y strain) or PBS. We observed resting bradycardia and improved performance in trained animals compared with sedentary ones. On the 20th day post-infection (DPI), we found a decrease in HR in SI animals compared to TI animals (699.73 ± 42.37 vs. 742.11 ± 25.35 bpm, respectively, P < 0.05). We also observed increased production of NO in cardiac tissue on the 20th DPI in the SI group, normalized in TI group (20.73 ± 2.74 vs. 6.51 ± 1.19 μM, respectively). Plasma pro-inflammatory cytokines (IL-12, TNF-α, IFN-γ,) and MCP-1 were increased in SI animals, but decreased in TI animals. The increase in parasitemia on the 15th and 17th DPI in the SI group was attenuated in the TI group. Our results suggest that previous ET plays a preventive role in resistance to T. cruzi infection, modulating cardiovascular aspects, inflammatory reaction, and NO levels of infected mice.

Exercise Training Prevents Cardiovascular Derangements Induced by Fructose Overload in Developing Rats

The risks of chronic diseases associated with the increasing consumption of fructose-laden foods are amplified by the lack of regular physical activity and have become a serious public health issue worldwide. Moreover, childhood eating habits are strongly related to metabolic syndrome in adults. Thus, we aimed to investigate the preventive role of exercise training undertaken concurrently with a high fructose diet on cardiac function, hemodynamics, cardiovascular autonomic modulation and oxidative stress in male rats after weaning. Male Wistar rats were divided into 4 groups (n = 8/group): Sedentary control (SC), Trained control (TC), Sedentary Fructose (SF) and Trained Fructose (TF). Training was performed on a treadmill (8 weeks, 40–60% of maximum exercise test). Evaluations of cardiac function, hemodynamics, cardiovascular autonomic modulation and oxidative stress in plasma and in left ventricle (LV) were performed. Chronic fructose overload induced glucose intolerance and an increase in white adipose tissue (WAT) weight, in myocardial performance index (MPI) (SF:0.42±0.04 vs. SC:0.24±0.05) and in arterial pressure (SF:122±3 vs. SC:113±1 mmHg) associated with increased cardiac and vascular sympathetic modulation. Fructose also induced unfavorable changes in oxidative stress profile (plasmatic protein oxidation- SF:3.30±0.09 vs. SC:1.45±0.08 nmol/mg prot; and LV total antioxidant capacity (TRAP)- SF: 2.5±0.5 vs. SC:12.7±1.7 uM trolox). The TF group showed reduced WAT, glucose intolerance, MPI (0.35±0.04), arterial pressure (118±2mmHg), sympathetic modulation, plasmatic protein oxidation and increased TRAP when compared to SF group. Therefore, our findings indicate that cardiometabolic dysfunctions induced by fructose overload early in life may be prevented by moderate aerobic exercise training.

Positive effect of combined exercise training in a model of metabolic syndrome and menopause: autonomic, inflammatory, and oxidative stress evaluations

It is now well established that after menopause cardiometabolic disorders become more common. Recently, resistance exercise has been recommended as a complement to aerobic (combined training, CT) for the treatment of cardiometabolic diseases. The aim of this study was to evaluate the effects of CT in hypertensive ovariectomized rats undergoing fructose overload in blood pressure variability (BPV), inflammation, and oxidative stress parameters. Female rats were divided into the following groups ( n = 8/group): sedentary normotensive Wistar rats (C), and sedentary (FHO) or trained (FHOT) ovariectomized spontaneously hypertensive rats undergoing and fructose overload. CT was performed on a treadmill and ladder adapted to rats in alternate days (8 wk; 40–60% maximal capacity). Arterial pressure (AP) was directly measured. Oxidative stress and inflammation were measured on cardiac and renal tissues. The association of risk factors (hypertension + ovariectomy + fructose) promoted increase in insulin resistance, mean AP (FHO: 174 ± 4 vs. C: 108 ± 1 mmHg), heart rate (FHO: 403 ± 12 vs. C: 352 ± 11 beats/min), BPV, cardiac inflammation (tumor necrosis factor-α-FHO: 65.8 ± 9.9 vs. C: 23.3 ± 4.3 pg/mg protein), and oxidative stress cardiac and renal tissues. However, CT was able to reduce mean AP (FHOT: 158 ± 4 mmHg), heart rate (FHOT: 303 ± 5 beats/min), insulin resistance, and sympathetic modulation. Moreover, the trained rats presented increased nitric oxide bioavailability, reduced tumor necrosis factor-α (FHOT: 33.1 ± 4.9 pg/mg protein), increased IL-10 in cardiac tissue and reduced lipoperoxidation, and increased antioxidant defenses in cardiac and renal tissues. In conclusion, the association of risk factors promoted an additional impairment in metabolic, cardiovascular, autonomic, inflammatory, and oxidative stress parameters and combined exercise training was able to attenuate these dysfunctions.

Dynamic resistance training decreases sympathetic tone in hypertensive ovariectomized rats

The aim of this study was to investigate the effects of resistance exercise training on hemodynamics and cardiac autonomic control in ovariectomized spontaneously hypertensive rats. Female rats were divided into 4 groups: sedentary control (SC), sedentary hypertensive (SH), sedentary hypertensive ovariectomized (SHO), and resistance-trained hypertensive ovariectomized (RTHO). Resistance exercise training was performed on a vertical ladder (5 days/week, 8 weeks) at 40-60% maximal load. Direct arterial pressure was recorded. Vagal and sympathetic tones were measured by heart rate (HR) responses to methylatropine (3 mg/kg, iv) and propranolol (4 mg/kg, iv). Ovariectomy resulted in additional increases in blood pressure in hypertensive rats and was associated with decreased vagal tone. Resistance exercise trained rats had lower mean arterial pressure than untrained rats (RTHO: 159±2.2 vs SHO: 177±3.4 mmHg), as well as resting bradycardia (RTHO: 332±9.0 vs SHO: 356±5 bpm). Sympathetic tone was also lower in the trained group. Moreover, sympathetic tone was positively correlated with resting HR (r=0.7, P<0.05). The additional arterial pressure increase in hypertensive rats caused by ovarian hormone deprivation was attenuated by moderate-intensity dynamic resistance training. This benefit may be associated with resting bradycardia and reduced cardiac sympathetic tone after training, which suggests potential benefits of resistance exercise for the management of hypertension after ovarian hormone deprivation.

Diabetic hyperglycemia attenuates sympathetic dysfunction and oxidative stress after myocardial infarction in rats

Background

Previous research has demonstrated that hyperglycemia may protect the heart against ischemic injury. The aim of the present study was to investigate the association between hyperglycemia and myocardial infarction on cardiovascular autonomic modulation and cardiac oxidative stress profile in rats. Male Wistar rats were divided into: control (C), diabetic (D), myocardial infarcted (MI) and diabetic infarcted rats (DMI).

Methods

Diabetes was induced by streptozotocin (STZ, 50 mg/Kg) at the beginning of the protocol and MI was induced by left coronary occlusion 15 days after STZ. Thirty days after streptozocin-induced diabetes, cardiovascular autonomic modulation was evaluated by spectral analysis, and oxidative stress profile was determined by antioxidant enzyme activities and superoxide anion, together with protein carbonylation and redox balance of glutathione (GSH/GSSG).

Results

The diabetic and infarcted groups showed decreased heart rate variability and vagal modulation (p < 0.05); however, sympathetic modulation decreased only in diabetic groups (p < 0.05). Sympatho/vagal balance and vascular sympathetic modulation were increased only in the MI group (p < 0.05). Diabetes promoted an increase in catalase concentration (p < 0.05). Glutathione peroxidase activity was increased only in DMI when compared to the other groups (p < 0.05). Superoxide anion and protein carbonylation were increased only in MI group (p < 0.05). Cardiac redox balance, as evaluated by GSH/GSSG, was lower in the MI group (p < 0.05).

Conclusions

These data suggest that hyperglycemia promotes compensatory mechanisms that may offer protection against ischemia, as demonstrated by increased antioxidants, decreased pro-oxidants and protein damage, possibly related to the improvements in both redox balance and sympathetic modulation to the heart.

Effects of ovariectomy on the secretory apparatus in the right atrial cardiomyocytes of middle-aged mice

OBJECTIVE

The aim of the present study was to evaluate the effects of ovariectomy on the secretory apparatus of natriuretic peptides in right atrial cardiomyocytes.

METHODS

Nine-month-old mice underwent bilateral ovariectomy or sham surgery. The blood exam of the ovariectomized mice showed results consistent with castrated females. Systolic blood pressure was measured after ovariectomy (9 mo of age) and at the moment of sacrifice (12 mo of age). Fragments of the right atrium were collected and prepared for electron microscopy examination. The following variables were quantified: the quantitative density and area of the natriuretic peptide granules, the relative volume of euchromatin in the nucleus, the number of pores per 10 μm of the nuclear membrane and the relative volumes of the mitochondria and Golgi complex.

RESULTS

The cardiomyocytes obtained from ovariectomized mice indicated that the quantitative density and the area of secretory granules of natriuretic peptides were significantly lower compared with the sham-operated mice. Furthermore, there was a decrease in the relative volume of euchromatin, a lower density of nuclear pores, and lower relative volumes of the mitochondria and Golgi complex in the ovariectomized mice compared with the sham-operated mice. These findings suggest a pool with a low turnover rate, i.e., low synthesis and elimination of natriuretic peptides.

CONCLUSION

A lack of estrogen caused hypotrophy of the secretory apparatus in right atrial cardiomyocytes that could explain the weak synthesis of natriuretic peptides in mice. Furthermore, one of the mechanisms of blood pressure control was lost, which may explain, in part, the elevated blood pressure in ovariectomized mice.

Pleiotropic effects of simvastatin in physically trained ovariectomized rats

This study tested the hypothesis that simvastatin treatment can improve cardiovascular and autonomic functions and membrane lipoperoxidation, with an increased effect when applied to physically trained ovariectomized rats. Ovariectomized rats were divided into sedentary, sedentary+simvastatin and trained+simvastatin groups (n = 8 each). Exercise training was performed on a treadmill for 8 weeks and simvastatin (5 mg/kg) was administered in the last 2 weeks. Blood pressure (BP) was recorded in conscious animals. Baroreflex sensitivity was evaluated by the tachycardic and bradycardic responses to BP changes. Cardiac vagal and sympathetic effects were determined using methylatropine and propranolol. Oxidative stress was evaluated based on heart and liver lipoperoxidation using the chemiluminescence method. The simvastatin-treated groups presented reduced body weight and mean BP (trained+simvastatin = 99 ± 2 and sedentary+simvastatin = 107 ± 2 mmHg) compared to the sedentary group (122 ± 1 mmHg). Furthermore, the trained group showed lower BP and heart rate compared to the other groups. Tachycardic and bradycardic responses were enhanced in both simvastatin-treated groups. The vagal effect was increased in the trained+simvastatin group and the sympathetic effect was decreased in the sedentary+simvastatin group. Hepatic lipoperoxidation was reduced in sedentary+simvastatin (≈21%) and trained+simvastatin groups (≈57%) compared to the sedentary group. Correlation analysis involving all animals demonstrated that cardiac lipoperoxidation was negatively related to the vagal effect (r = -0.7) and positively correlated to the sympathetic effect (r = 0.7). In conclusion, improvement in cardiovascular and autonomic functions associated with a reduction of lipoperoxidation with simvastatin treatment was increased in trained ovariectomized rats.

The effect of exercise on the oxidative stress induced by experimental lung injury

AIM

The effects of physical exercise on oxidative stress parameters and immunocontent of NF-кβ/p65 in lung of rats submitted to lung injury, as well as its possible protective effect on the changes in the alveolar-capillary barrier (total cell count, lactate dehydrogenase and total protein) in the bronchoalveolar lavage fluid (BALF) and the inflammatory infiltration in the pulmonary parenchyma were evaluated.

MAIN METHODS

Wistar rats were submitted to two months of physical exercise and after this period, lung injury was induced by intratracheal instillation of lipopolysaccharide (dose of 100 μg/100 g body weight). Twelve hours after injury, the animals were sacrificed and lung and BALF were collected.

KEY FINDINGS

Results showed an increase in reactive species production, lipid peroxidation, oxidative damage to protein, as well as in nitrite levels and NF-кβ/p65 immunocontent in lung of rats submitted to lung injury. Physical exercise was able to totally prevent the increase in reactive species, nitrite levels and NF-кβ/p65 immunocontent, but partially prevented the damage to protein. Superoxide dismutase and catalase were not changed in lung injury group, but the activities of these enzymes were increased in lung injury plus exercise group. Non-enzymatic antioxidant capacity, glutathione content and glutathione peroxidase were decreased and exercise totally prevented such effects. Rats subjected to lung injury presented an increase in total cell, lactate dehydrogenase and total protein; exercise partially prevented the increase in lactate dehydrogenase.

SIGNIFICANCE

These findings suggest that physical exercise may prevent, at least partially, the oxidative damage caused by experimental lung injury, suggesting that exercise may have an important role as protector in this condition.

Combined influence of intermittent exercise and temperature stress on the modulation of fluoride toxicity

Regardless of the circumstantial evidences on the involvement of fluoride on the etiology and pathogenesis of fluorosis, several lines of evidences strongly indicate the influence of modulator factors such as duration of fluoride exposure, age, temperature, and physical activity. This study has been designed to investigate the combined influence of intermittent exercise and temperature stress on the modulation of fluoride toxicity. Three-month-old Wistar male rats were exposed to high sodium fluoride (600 ppm) through drinking water for 1 month and the rats were then subjected to swimming exercise at different temperatures (20°C, 25°C, 30°C, and 35°C). Oxidative stress indices analyzed showed fluoride-induced oxidative stress in biological tissues studied like brain, heart, liver, and kidney. Exercise regimen coupled with different temperatures were found to be effective in bringing the oxidative stress indices to near normal level indicating decreased free radical production which may be a compensatory mechanism to counteract against the detrimental effects of fluoride. Further, the deleterious effects of fluoride significantly reduced at 25°C and 30°C demonstrating that the thermoneutral temperatures were effective in reducing the toxicity level.

Walking promotes metabolic and baroreflex sensitivity improvement in fructose-fed male rats

The aim of this study was to investigate metabolic and cardiovascular responses to walking in fructose-fed rats. Male Wistar rats were divided into control (C), sedentary fructose (SF) and walking fructose (WF). Fructose-fed rats received D-fructose (100 g/l). WF rats walked on a treadmill at constant load (0.3 km/h) during 1 h/day, 5 days/week for 8 weeks. Measurements of triglyceride concentrations, adipose tissue and glycemia were carried out together with insulin tolerance test to evaluate metabolic profile. Arterial pressure (AP) signals were directly recorded. Baroreflex sensitivity (BR) was evaluated by the reflex tachycardia (TR) and bradycardia (BR) to AP changes. The results showed that walking decreased the adipose tissue (SF: 6.5 ± 0.4; WF: 2.8 ± 0.1; C: 3.0 ± 0.3 g), blood triglyceride levels (SF: 291 ± 6.5; WF: 150 ± 8.1; C: 103 ± 4.5 mg/dl) and increased insulin sensitivity (SF: 2.5 ± 0.2; WF: 3.3 ± 0.32; C: 4.8 ± 0.4 %/min). Baroreflex sensitivity was improved in the WF group expressed by BR (SF: 0.75 ± 0.10; WF: 1.18 ± 0.10; C: 1.5 ± 0.14 ms/mmHg) and TR (SF: 0.80 ± 0.12; WF: 1.21 ± 0.10; C: 1.35 ± 0.11 ms/mmHg), as well as when verified by the alpha index. Although the WF group showed decreased AP when compared with the SF group, the values still enhanced in relation to C rats (SF: 137 ± 2; WF: 129 ± 1; C: 115 ± 6 mmHg). Our findings allow a better understanding of the effects of walking, a low-intensity exercise training, on the hemodynamic and metabolic aspects of male rats with metabolic syndrome and indicate that walking seems to be particularly effective in treating metabolic disturbances in this model.

A brief review of chronic exercise intervention to prevent autonomic nervous system changes during the aging process

The aging process is associated with alterations in the cardiovascular and autonomic nervous systems. Autonomic changes related to aging involve parasympathetic and sympathetic alterations leading to a higher incidence of cardiovascular disease morbidity and mortality. Several studies have suggested that physical exercise is effective in preventing deleterious changes. Chronic exercise in geriatrics seems to be associated with improvement in the cardiovascular system and seems to promote a healthy lifestyle. In this review, we address the major effects of aging on the autonomic nervous system in the context of cardiovascular control. We examine the use of chronic exercise to prevent cardiovascular changes during the aging process.

Exercise training impacts the myocardial metabolism of older individuals in a gender-specific manner

Aging is associated with decreases in aerobic capacity, cardiac function, and insulin sensitivity as well as alterations in myocardial substrate metabolism. Endurance exercise training (EET) improves cardiac function in a gender-specific manner, and EET has been shown to improve whole body glucose tolerance, but its effects on myocardial metabolism are unclear. Accordingly, we studied the effect of EET on myocardial substrate metabolism in older men and women. Twelve healthy older individuals (age: 60-75 yr; 6 men and 6 women) underwent PET with [(15)O]water, [(11)C]acetate, [(11)C]glucose, and [(11)C]palmitate for the assessment of myocardial blood flow (MBF), myocardial O(2) consumption (MVo(2)), myocardial glucose utilization (MGU), and myocardial fatty acid utilization (MFAU), respectively, at rest and during dobutamine infusion (10 microg.kg(-1).min(-1)). Measurements were repeated after 11 mo of EET. Maximal O(2) uptake (Vo(2max)) increased (P = 0.005) after EET. MBF was unaffected by training, as was resting MVo(2); however, posttraining dobutamine MVo(2) was significantly higher (P = 0.05), as was MGU (P < 0.04). Although overall dobutamine MFAU was unchanged, posttraining dobutamine MFAU increased in women (P = 0.01) but decreased in men (P = 0.03). Thus, EET in older individuals improves the catecholamine response of myocardial glucose metabolism. Moreover, gender differences exist in the myocardial fatty acid metabolic response to training. These findings suggest a role for altered myocardial substrate metabolism in modulating the cardiovascular benefits of EET in older individuals.

Maximal exercise test is a useful method for physical capacity and oxygen consumption determination in streptozotocin-diabetic rats

Background

The aim of the present study was to investigate the relationship between speed during maximum exercise test (ET) and oxygen consumption (VO₂) in control and STZ-diabetic rats, in order to provide a useful method to determine exercise capacity and prescription in researches involving STZ-diabetic rats.

Methods

Male Wistar rats were divided into two groups: control (CG, n = 10) and diabetic (DG, n = 8). The animals were submitted to ET on treadmill with simultaneous gas analysis through open respirometry system. ET and VO₂ were assessed 60 days after diabetes induction (STZ, 50 mg/Kg).

Results

VO₂ maximum was reduced in STZ-diabetic rats (72.5 ± 1 mL/Kg/min^-1) compared to CG rats (81.1 ± 1 mL/Kg/min^-1). There were positive correlations between ET speed and VO₂ (r = 0.87 for CG and r = 0.8 for DG), as well as between ET speed and VO₂ reserve (r = 0.77 for CG and r = 0.7 for DG). Positive correlations were also obtained between measured VO₂ and VO₂ predicted values (r = 0.81 for CG and r = 0.75 for DG) by linear regression equations to CG (VO₂ = 1.54 * ET speed + 52.34) and DG (VO₂ = 1.16 * ET speed + 51.99). Moreover, we observed that 60% of ET speed corresponded to 72 and 75% of VO₂ reserve for CG and DG, respectively. The maximum ET speed was also correlated with VO₂ maximum for both groups (CG: r = 0.7 and DG: r = 0.7).

Conclusion

These results suggest that: a) VO₂ and VO₂ reserve can be estimated using linear regression equations obtained from correlations with ET speed for each studied group; b) exercise training can be prescribed based on ET in control and diabetic-STZ rats; c) physical capacity can be determined by ET. Therefore, ET, which involves a relatively simple methodology and low cost, can be used as an indicator of cardio-respiratory capacity in future studies that investigate the physiological effect of acute or chronic exercise in control and STZ-diabetic male rats.

Efeitos fisiológicos do treinamento físico em pacientes portadores de diabetes tipo 1

Insulinoterapia, atividade física regular e planejamento alimentar, em conjunto, consistem na abordagem mais completa no tratamento de portadores de diabetes mellitus tipo 1 (DM1). Estudos clínicos e experimentais têm evidenciado os benefícios do treinamento físico em indivíduos com DM1, tais como melhora na sensibilidade à insulina, redução das doses de insulina e atenuação das disfunções autonômicas e cardiovasculares. Essa revisão aborda as adaptações fisiológicas ao treinamento físico no indivíduo com DM1 e discute as recomendações e prescrição de atividade física para esta população.

Baroreflex sensitivity improvement is associated with decreased oxidative stress in trained spontaneously hypertensive rat

BACKGROUND

Baroreflex sensitivity (BRS) impairment has been associated with endothelial dysfunction and oxidative stress.

METHODS

Because exercise training could improve endothelial function in spontaneously hypertensive rats (SHR), the effect of moderate exercise training on oxidative stress and BRS was investigated. Groups were divided into sedentary and trained Wistar-Kyoto rats (S-WK, n = 7 and T-WK, n = 6) and SHR (S-SHR and T-SHR, n = 9 each). Exercise training was performed on a treadmill (5 days/week, 60 min, 10 weeks), and the lactate threshold (20 m/min) was used to determine moderate intensity.

RESULTS

Exercise training reduced mean arterial pressure in WK and SHR (S-WK 127 +/- 4, T-WK 105 +/- 5, S-SHR 169 +/- 4 versus T-SHR 140 +/- 4 mmHg; P < 0.01). Baroreflex bradycardic (S-WK -1.89 +/- 0.15, T-WK -2.11 +/- 0.37, S-SHR -0.80 +/- 0.09 versus T-SHR -1.29 +/- 0.10 bpm/mmHg; P < 0.0001) and tachycardic (S-WK 2.57 +/- 0.19, T-WK 2.73 +/- 0.21, S-SHR 1.18 +/- 0.07 versus T-SHR 2.02 +/- 0.10 bpm/mmHg; P < 0.0001) responses were significantly different between groups. Lipoperoxidation in erythrocytes (S-WK 11 320 +/- 739, T-WK 10 397 +/- 765, S-SHR 20 511 +/- 1627 versus T-SHR 10 211 +/- 589 counts per second (cps)/mg haemoglobin; P < 0.0001) and aortas (S-WK 12 424 +/- 2219, T-WK 7917 +/- 726, S-SHR 26 957 +/- 1772 versus T-SHR 17 777 +/- 1923 cps/mg protein; P < 0.0001) was reduced in T-SHR compared with S-SHR. Inverse correlations were observed between both bradycardic and tachycardic responses and lipoperoxidation in erythrocytes (r = 0.56 and r = -0.77, respectively; P < 0.01) and aortas (r = 0.77 and r = -0.80, respectively; P < 0.0001).

CONCLUSION

Our results indicate that exercise training decreases oxidative stress, which is related to an improvement in BRS in SHR.

Photoprotection by topical application of Achyrocline satureioides ('Marcela')

It has been demonstrated that the use of topical antioxidants can contribute to controling the free radicals excess produced by ultraviolet (UV) irradiation of the skin, being beneficial for processes such as photo aging and eventually cancer. Some plant extracts, particularly because of their polyphenolic constituents, can be beneficial for skin photo damage. Plant extracts of Achyrocline satureioides (AS) and Epilobium parviflorum (EP), potent antioxidant medicinal plants, were mixed with a cosmetic base and applied to the back skin of rabbits. Afterwards the skin was exposed to 1 h of UV irradiation from a known source. The production of the hydroxyl (OH.) radical was assessed in the skin after UV by measuring 2,3-dyhydroxybenzoic acid (2,3-DHBA), produced by the hydroxylation of sodium salicylate, previously injected intracutaneously (i.c.) in the irradiated areas. The UV provoked a marked increase in 2,3-DHBA that was significantly decreased by the AS cosmetic preparation. The EP extract did not show any effect on 2,3-DHBA production. It is concluded that the cosmetic preparation containing the AS extract is able to scavenge OH. production likely to be due to the presence of high concentrations of flavonoid aglycones such as quercetin, luteolin and 3-O-methylquercetin.

Radicais livres de oxigênio e exercício: mecanismos de formação e adaptação ao treinamento físico

O interesse acerca dos mecanismos de geração e adaptação de radicais livres de oxigênio (RLO) ao exercício aumentou significativamente a partir da demonstração de sua relação com o consumo de oxigênio. Os RLO são formados pela redução incompleta do oxigênio, gerando espécies que apresentam alta reatividade para outras biomoléculas, principalmente lipídios e proteínas das membranas celulares e, até mesmo, o DNA. As injúrias provocadas por estresse oxidativo apresentam efeitos cumulativos e estão relacionadas a uma série de doenças, como o câncer, a aterosclerose e o diabetes. O exercício físico agudo, em função do incremento do consumo de oxigênio, promove o aumento da formação de RLO. No entanto, o treinamento físico é capaz de gerar adaptações capazes de mitigar os efeitos deletérios provocados pelos RLO. Estas adaptações estão relacionadas a uma série de sistemas, dos quais os mais importantes são os sistemas enzimáticos, compostos pela superóxido dismutase, catalase e glutationa peroxidase, e o não enzimático, composto por ceruloplasmina, hormônios sexuais, coenzima Q, ácido úrico, proteínas de choque térmico e outros. Tais adaptações, apesar das controvérsias sobre os mecanismos envolvidos, promovem maior resistência tecidual a desafios oxidativos, como aqueles proporcionados pelo exercício de alta intensidade e longa duração. As técnicas de avaliação de estresse oxidativo, na maioria das vezes, não são capazes de detectar injúria em exercícios de curta duração. Dessa forma, esforços estão sendo feitos para o estudo de esforços físicos realizados por longos períodos de tempo ou efetuados até a exaustão. Novos marcadores de lesão por ação dos RLO estão sendo descobertos e novas técnicas para sua determinação estão sendo criadas. O objetivo deste trabalho é discutir os mecanismos da formação dos RLO e das adaptações ao estresse oxidativo crônico provocado pelo treinamento físico.

Exercise training changes autonomic cardiovascular balance in mice

Experiments were performed to investigate the influence of exercise training on cardiovascular function in mice. Heart rate, arterial pressure, baroreflex sensitivity, and autonomic control of heart rate were measured in conscious, unrestrained male C57/6J sedentary ( n = 8) and trained mice ( n = 8). The exercise training protocol used a treadmill (1 h/day; 5 days/wk for 4 wk). Baroreflex sensitivity was evaluated by the tachycardic and bradycardic responses induced by sodium nitroprusside and phenylephrine, respectively. Autonomic control of heart rate and intrinsic heart rate were determined by use of methylatropine and propranolol. Resting bradycardia was observed in trained mice compared with sedentary animals [485 ± 9 vs. 612 ± 5 beats/min (bpm)], whereas mean arterial pressure was not different between the groups (106 ± 2 vs. 108 ± 3 mmHg). Baroreflex-mediated tachycardia was significantly enhanced in the trained group (6.97 ± 0.97 vs. 1.6 ± 0.21 bpm/mmHg, trained vs. sedentary), whereas baroreflex-mediated bradycardia was not altered by training. The tachycardia induced by methylatropine was significantly increased in trained animals (139 ± 12 vs. 40 ± 9 bpm, trained vs. sedentary), whereas the propranolol effect was significantly reduced in the trained group (49 ± 11 vs. 97 ± 11 bpm, trained vs. sedentary). Intrinsic heart rate was similar between groups. In conclusion, dynamic exercise training in mice induced a resting bradycardia and an improvement in baroreflex-mediated tachycardia. These changes are likely related to an increased vagal and decreased sympathetic tone, similar to the exercise response observed in humans.

Long-term combined beneficial effects of physical training and metabolic treatment on atherosclerosis in hypercholesterolemic mice

The pathogenic mechanisms by which physical exercise influences atherosclerotic lesion formation remain poorly understood. Because vigorous physical training increases oxidative stress, this study tested the hypothesis that graduated and moderate physical exercise together with metabolic intervention (l-arginine and antioxidants) may contribute to increased vascular protection. Exercise training in mice was induced by graduated swimming. In hypercholesterolemic male mice on an atherogenic high-cholesterol diet, graduated and moderate exercise lowered plasma cholesterol and decreased atherosclerotic lesions compared with sedentary control mice. Antioxidants (1.0% vitamin E added to the chow and 0.05% vitamin C added to the drinking water) and l-arginine (6% in drinking water) supplementation to exercising hypercholesterolemic mice further and synergistically reduced atherosclerosis compared with untreated exercised mice. Arterial oxidation-specific epitopes and systemic oxidative stress were reduced by metabolic intervention. Graduated chronic exercise elicited an increase in production of nitric oxide through increased endothelial nitric oxide synthase expression and ameliorated scavenger activities. Thus, metabolic intervention with l-arginine and antioxidants together with graduated and moderate exercise training reduce atherosclerotic lesion formation.

Long-term exercise down-regulates leptin receptor mRNA in the arcuate nucleus

The purpose of this study was to investigate the effects of exercise on blood leptin concentrations and expression of leptin receptor subtype-b (Ob-Rb) mRNA in the arcuate nucleus of hypothalamus (ARC). Male Wistar rats (26 weeks old) underwent regular wheel exercise for 12 weeks. The expression of Ob-Rb mRNA in the ARC decreased at the end of the study period despite reductions of abdominal fat-pad weight and serum leptin concentration. Serum 1,5-anhydroglucitol levels were higher in exercising rats, suggesting lower serum insulin levels in exercising rats. Our results suggested that 12-week wheel exercise reduced the expression of Ob-Rb mRNA in the ARC probably through improvement in insulin resistance.

Reactive oxygen species in pregnant rats: effects of exercise and thermal stress

With the aim of evaluating the effect of interaction between physical training or exercise only during pregnancy and thermal stress on oxidative stress, and antioxidant mechanism sedentary pregnant rats (PS), exercised pregnant rats only during pregnancy (PE) and trained rats submitted to also exercise during pregnancy (PT) were compared (N=63). Exercise sessions consisted of swimming at 80% of maximal work load supported into water at 28 degrees C (hypothermia, PS 28, PE28, PT28) or 35 degrees C (thermal neutrality, PS35, PE35, PT35) or 39 degrees C (hyperthermia, PS39, PE39, PT39), for 30 min. The initial body weight in all groups of rats was from 177 to 207 g. On the 20th day of pregnancy, 24 h after the last immersion or swimming session venous blood was collected to determine oxidative stress. Plasma concentrations of means malondialdehyde (MDA) values measured as thiobarbituric acid reactive substances (TBARS); total glutathione (GSH) and vitamin E were determined. The oxidative stress index was calculated from the ratio TBARS/GSH and TBARS/Vitamin E. TBARS did not change on the group PE at different temperatures of water; TBARS were higher for PS28 than PS35 and PS39; PT35 had higher values than PT28 and PT39. For GSH, PS39 was lower than PS35; PE28 was higher than PE35 and PE39 and PT35 were lower than PT28 and PT39. Plasma concentration of vitamin E did not present any difference for sedentary rats at different water temperatures, but for PE28, the values were lower than for PE35 and PE39, whereas PT39 was lower than PT35 and PT28. In relation to TBARS/GSH, it was verified an increase in oxidative stress for PS28 (in relation to PS35 and PS39), PE35, and PT35 (in relation to PE28 and PE39 or PT28 and PT39); regarding the ratio TBARS/vitamin E, the highest values were obtained at 35 degrees C for PS and PT groups and at 39 for PE group. These results have shown the great complexity of the interaction between physical training, thermal stress and pregnancy. Apparently, hypothermia produces large index of oxidative stress only in sedentary rats, but this index was greater at 35 degrees C in relation to extreme temperatures for trained rats. These results have suggested that physical training allows a more efficient activation of antioxidant mechanisms under thermal stress.

Aging-induced decrease in the PPAR-alpha level in hearts is improved by exercise training

Peroxisome proliferator-activated receptor (PPAR)-alpha, a transcriptional activator, regulates genes of fatty acid (FA) metabolic enzymes. To study the contribution of PPAR-alpha to exercise training-induced improvement of FA metabolic capacity in the aged heart, we investigated whether PPAR-alpha signaling and expression of its target genes in the aged heart are affected by exercise training. We used hearts of sedentary young rat (4 mo old), sedentary aged rat (23 mo old), and swim-trained aged rat (23 mo old, training for 8 wk). The mRNA and protein expression of PPAR-alpha in the heart was significantly lower in the sedentary aged rats compared with the sedentary young rats and was significantly higher in the swim-trained aged rats compared with the sedentary aged rats. The activity of PPAR-alpha DNA binding to the transcriptional regulating region on the FA metabolic enzyme genes, the mRNA expression of 3-hydroxyacyl CoA dehydrogenase (HAD) and carnitine palmitoyl transferase-I, which are PPAR-alpha target genes, and the enzyme activity of HAD in the heart altered in association with changes of the myocardial PPAR-alpha mRNA and protein levels. These findings suggest that exercise training improves aging-induced downregulation in myocardial PPAR-alpha-mediated molecular system, thereby contributing to the improvement of the FA metabolic enzyme activity in the trained-aged hearts.

Cardiovascular control in experimental diabetes

Several studies have reported impairment in cardiovascular function and control in diabetes. The studies cited in this review were carried out from a few days up to 3 months after streptozotocin administration and were concerned with the control of the circulation. We observed that early changes (5 days) in blood pressure control by different peripheral receptors were maintained for several months. Moreover, the impairment of reflex responses observed after baroreceptor and chemoreceptor stimulation was probably related to changes in the efferent limb of the reflex arc (sympathetic and parasympathetic), but changes also in the central nervous system could not be excluded. Changes in renal sympathetic nerve activity during volume expansion were blunted in streptozotocin-treated rats, indicating an adaptive natriuretic and diuretic response in the diabetic state. The improvement of diabetic cardiovascular dysfunction induced by exercise training seems to be related to changes in the autonomic nervous system. Complementary studies about the complex interaction between circulation control systems are clearly needed to adequately address the management of pathophysiological changes associated with diabetes.

High level of physical activity preserves the cardioprotective effect of preinfarction angina in elderly patients

OBJECTIVES

The study investigated the effects of physical activity on preinfarction angina, a clinical equivalent of ischemic preconditioning (PC), in adult and elderly patients with acute myocardial infarction (AMI).

BACKGROUND

Preinfarction angina seems to confer protection against in-hospital mortality in adult but not in elderly patients. However, it has been experimentally demonstrated that exercise training restores the protective effect of PC in the aging heart.

METHODS

We retrospectively verified whether physical activity preserved the protective effect of preinfarction angina against in-hospital mortality in 557 elderly patients with AMI. Physical activity was quantified according to the Physical Activity Scale for the Elderly (PASE).

RESULTS

In-hospital mortality was 22.2% in elderly patients with preinfarction angina and 27.2% in those without (p = 0.20). When the PASE score was stratified in quartiles (0 to 40, 41 to 56, 57 to 90, >90), a high score was strongly associated with reduced in-hospital mortality (30.8%, 32.2%, 17.2% and 15.3%, respectively, p < 0.001 for trend). Interestingly, a high level of physical activity reduced in-hospital mortality in elderly patients with preinfarction angina (35.7%, 35.4%, 12.3% and 4.23%, respectively, p < 0.001 for trend) but not in those without (23.0%, 27.2%, 26.0% and 35.0%, respectively, p = 0.35 for trend). Accordingly, the protective role of preinfarction angina on in-hospital mortality was present only in elderly patients showing a high level of physical activity (adjusted odds ratio, 0.09; 95% confidence interval, 0.01 to 0.57; p < 0.05).

CONCLUSIONS

Physical activity and not preinfarction angina protects against in-hospital mortality in elderly patients with myocardial infarction. Nevertheless, the protective effect of preinfarction angina is preserved in elderly patients with a high level of physical activity.

Aging and baroreflex control of RSNA and heart rate in rats

Aging is associated with altered autonomic control of cardiovascular function, but baroreflex function in animal models of aging remains controversial. In this study, pressor and depressor agent-induced reflex bradycardia and tachycardia were attenuated in conscious old (24 mo) rats [57 and 59% of responses in young (10 wk) Wistar rats, respectively]. The intrinsic heart rate (HR, 339 +/- 5 vs. 410 +/- 10 beats/min) was reduced in aged animals, but no intergroup differences in resting mean arterial blood pressure (MAP, 112 +/- 3 vs. 113 +/- 5 mmHg) or HR (344 +/- 9 vs. 347 +/- 9 beats/min) existed between old and young rats, respectively. The aged group also exhibited a depressed (49%) parasympathetic contribution to the resting HR value (vagal effect) but preserved sympathetic function after intravenous methylatropine and propranolol. An implantable electrode revealed tonic renal sympathetic nerve activity (RSNA) was similar between groups. However, old rats showed impaired baroreflex control of HR and RSNA after intravenous nitroprusside (-0.63 +/- 0. 18 vs. -1.84 +/- 0.4 bars x cycle(-1) x mmHg(-1) x s(-1)). Therefore, aging in rats is associated with 1) preserved baseline MAP, HR, and RSNA, 2) impaired baroreflex control of HR and RSNA, and 3) altered autonomic control of resting HR.

Exercise training restores ischemic preconditioning in the aging heart

OBJECTIVES

To investigate the effects of ischemic preconditioning in hearts from adult and both sedentary and trained senescent rats.

BACKGROUND

Ischemic preconditioning does not prevent postischemic dysfunction in the aging heart, probably because of reduction of cardiac norepinephrine release. Exercise training can reverse the age-related decrease of norepinephrine production.

METHODS

We investigated the effects on mechanical parameters of ischemic preconditioning against 20 min of global ischemia followed by 40 min of reperfusion in isolated perfused hearts from adult (six months) and sedentary or trained (six weeks of graduated swim training) senescent (24 months) rats. Norepinephrine release in coronary effluent was determined by high-performance liquid chromatography.

RESULTS

Final recovery of percent-developed pressure was significantly improved after preconditioning in adult hearts (91.6+/-9.6%) versus unconditioned controls (54.2+/-5.1%, p<0.01). The effect of preconditioning on developed pressure recovery was absent in sedentary but present in trained senescent hearts (39.6+/-4.1% vs. 64.3+/-7.1%, p<0.05). Norepinephrine release significantly increased after preconditioning in adult and in trained but not in sedentary senescent hearts. The depletion of myocardial norepinephrine stores by reserpine abolished preconditioning effects in adult and trained senescent hearts.

CONCLUSIONS

In adult and trained but not in sedentary senescent hearts, preconditioning reduces postischemic dysfunction and is associated with an increase in norepinephrine release. Preconditioning was blocked by reserpine in both adult and trained senescent hearts. Thus, exercise training may restore preconditioning in the senescent heart through an increase of norepinephrine release.

Effects of exercise training on autonomic and myocardial dysfunction in streptozotocin-diabetic rats

Several investigators have demonstrated that diabetes is associated with autonomic and myocardial dysfunction. Exercise training is an efficient non-pharmacological treatment for cardiac and metabolic diseases. The aim of the present study was to investigate the effects of exercise training on hemodynamic and autonomic diabetic dysfunction. After 1 week of diabetes induction (streptozotocin, 50 mg/kg, iv), male Wistar rats (222 +/- 5 g, N = 18) were submitted to exercise training for 10 weeks on a treadmill. Arterial pressure signals were obtained and processed with a data acquisition system. Autonomic function and intrinsic heart rate were studied by injecting methylatropine and propranolol. Left ventricular function was assessed in hearts perfused in vitro by the Langendorff technique. Diabetes (D) bradycardia and hypotension (D: 279 +/- 9 bpm and 91 +/- 4 mmHg vs 315 +/- 11 bpm and 111 +/- 4 mmHg in controls, C) were attenuated by training (TD: 305 +/- 7 bpm and 100 +/- 4 mmHg). Vagal tonus was decreased in the diabetic groups and sympathetic tonus was similar in all animals. Intrinsic heart rate was lower in D (284 +/- 11 bpm) compared to C and TD (390 +/- 8 and 342 +/- 14 bpm, respectively). Peak systolic pressure developed at different pressures was similar for all groups, but +dP/dt max was decreased and -dP/dt max was increased in D. In conclusion, exercise training reversed hypotension and bradycardia and improved myocardial function in diabetic rats. These changes represent an adaptive response to the demands of training, supporting a positive role of physical activity in the management of diabetes.

Exercise reverses peripheral insulin resistance in trained L-NAME-hypertensive rats

Several studies have demonstrated an increase in peripheral resistance to insulin associated with hypertension. To assess the hemodynamic and metabolic effects of exercise training, normotensive and N(omega)-nitro-L-arginine methyl ester (L-NAME)-hypertensive male Wistar rats were submitted to low-intensity treadmill exercise training for 10 weeks and compared with their sedentary controls. Blood pressure signals were obtained and processed with a data acquisition system (CODAS, 1 kHz) to evaluate mean arterial pressure, heart rate, autonomic control of heart rate, and baroreflex sensitivity. Exercise training induced a nonsignificant 6.5-mm Hg decrease in mean arterial pressure in trained hypertensive rats (163+/-9 mm Hg) compared with sedentary hypertensive rats (169.5+/-5. 5 mm Hg). The hypertensive groups showed impairment of baroreflex function in response to changes in arterial pressure compared with sedentary controls. Furthermore, exercise training improved the tachycardic response to decreasing arterial pressure and reduced intrinsic heart rate in trained control rats compared with all other groups. Sedentary hypertensive rats presented a decrease in body weight compared with normotensive animals. Basal evaluation of the glucose/insulin ratio showed increased insulin resistance in sedentary (28.4+/-3) and trained (23.5+/-2.7) hypertensive rats compared with sedentary control rats (40.5+/-3). However, the glucose/insulin ratio evaluated during the exercise session in trained rats showed an improvement in insulin resistance (54.5+/-5 for control rats and 44+/-9 for hypertensive rats). In conclusion, L-NAME-induced hypertension is accompanied by an increase in insulin resistance in rats. The improvement in peripheral insulin sensitivity during exercise and the body weight gain observed in trained hypertensive rats may support the positive role of physical activity in the management of hypertension.