Early remodeling of rat cardiac muscle induced by swimming training

The aim of the present investigation was to study the effect of acute swimming training with an anaerobic component on matrix metallopeptidase (MMP) activity and myosin heavy chain gene expression in the rat myocardium. Animals (male Wistar rats, weighing approximately 180 g) were trained for 6 h/day in 3 sessions of 2 h each for 1 to 5 consecutive days (N = 5 rats per group). Rats swam in basins 47 cm in diameter and 60 cm deep filled with water at 33 to 35ºC. After the training period a significant increase (P < 0.05) was observed in the heart weight normalized to body weight by about 22 and 35% in the groups that trained for 96 and 120 h, respectively. Blood lactate levels were significantly increased (P < 0.05) in all groups after all training sessions, confirming an anaerobic component. However, lactate levels decreased (P < 0.05) with days of training, suggesting that the animals became adapted to this protocol. Myosin heavy chain-ß gene expression, analyzed by real time PCR and normalized with GAPDH gene expression, showed a significant two-fold increase (P < 0.01) after 5 days of training. Zymography analysis of myocardium extracts indicated a single ~60-kDa activity band that was significantly increased (P < 0.05) after 72, 96, and 120 h, indicating an increased expression of MMP-2 and suggesting precocious remodeling. Furthermore, the presence of MMP-2 was confirmed by Western blot analysis, but not the presence of MMP-1 and MMP-3. Taken together, our results indicate that in these training conditions, the rat heart undergoes early biochemical and functional changes required for the adaptation to the new physiological condition by tissue remodeling.

Swimming training down-regulates plasma leptin levels, but not adipose tissue ob mRNA expression

The aim of the present study was to assess the effects of endurance training on leptin levels and adipose tissue gene expression and their association with insulin, body composition and energy intake. Male Wistar rats were randomly divided into two groups: trained (N = 18) and sedentary controls (N = 20). The trained group underwent swimming training for 9 weeks. Leptin and insulin levels, adiposity and leptin gene expression in epididymal and inguinal adipose tissue were determined after training. There were no differences in energy intake between groups. Trained rats had a decreased final body weight (-10%), relative and total body fat (-36 and -55%, respectively) and insulin levels (-55%) compared with controls (P < 0.05). Although trained animals showed 56% lower leptin levels (2.58 ± 1.05 vs 5.89 ± 2.89 ng/mL in control; P < 0.05), no difference in leptin gene expression in either fat depot was demonstrable between groups. Stepwise multiple regression analysis showed that lower leptin levels in trained rats were due primarily to their lower body fat mass. After adjustment for total body fat, leptin levels were still 20% (P < 0.05) lower in exercised rats. In conclusion, nine weeks of swimming training did not affect leptin gene expression, but did lead to a decrease in leptin levels that was independent of changes in body fat.

EFFECTS of 14-WEEK SWIMMING TRAINING PROGRAM on THE PSYCHOLOGICAL, HORMONAL, and PHYSIOLOGICAL PARAMETERS of ELITE WOMEN ATHLETES

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The response of the lactate minimum test to a 12-week swimming training

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Results from the April 2009 Gulf of Alaska Line Transect Survey (GOALS) in the Navy Training Exercise Area

Little is known about the present-day occurrence of cetaceans found in offshore waters in the Gulf of Alaska; however, whaling records and a few recent surveys have shown this area to be important habitat. The U.S. Navy maintains a maritime training area in the central Gulf of Alaska, east of Kodiak Island, and has requested additional information on marine mammal presence and use of this area. To describe the occurrence and distribution of marine mammals in and around the U.S. Navy training area, a line transect visual and acoustic survey was conducted 10-20 April 2009 from the NOAA ship Oscar Dyson. The primary survey area encompassed nearshore and offshore pelagic waters of the central Gulf of Alaska. Survey lines were designed to provide equal coverage of the nearshore and offshore habitat.

Responses of blood lactate concentration in aerobic and anaerobic training protocols at different swimming exercise intensities in rats

A swimming periodized experimental training model in rats in which different training protocols (TP) were classified in aerobic (A) and anaerobic (AN) intensity levels. The purpose of the present study was to verify if the classification of the TP used in the periodized training experimental model presented the blood lactate concentration [La] response adequate to the aerobic and anaerobic intensities levels. Twenty three male Wistar rats were divided into three groups. Two groups of swimming training (continuous, CT, n = 7, and periodized training, PET, n = 7) rats were evaluated during 5 weeks in eight different TP (TP-1 to TP-8) through the analysis of the [La] response. The third group was the sedentary control (SC, n = 9). The TP were classified in five intensity levels, three aerobic (A-1, A-2, A-3) and two anaerobic (AN-1, AN-2). Analysis of variance (ANOVA one-way, P<0.05) indicated significant differences in the [La] among the TP and among the five intensity levels. All TP of the A-2 and A-3 intensity levels differed from the A-1 and AN-1. The A-1 and AN-1 also differed among them. These findings demonstrate that the TP were classified properly at different levels of aerobic and anaerobic intensities, as based on the [La] response in a way similar to that of high performance swimming with humans. The results offer new perspectives for the study of exercise training in swimming rats at different levels intensity for performance or for health.

MicroRNAs 29 are involved in the improvement of ventricular compliance promoted by aerobic exercise training in rats

Soci UPR, Fernandes T, Hashimoto NY, Mota GF, Amadeu MA, Rosa KT, Irigoyen MC, Phillips MI, Oliveira EM. MicroRNAs 29 are involved in the improvement of ventricular compliance promoted by aerobic exercise training in rats. Physiol Genomics 43: 665-673, 2011. First published March 29, 2011; doi:10.1152/physiolgenomics.00145.2010.-MiRNAs regulate cardiac development, hypertrophy, and angiogenesis, but their role in cardiac hypertrophy (CH) induced by aerobic training has not previously been studied. Aerobic training promotes physiological CH preserving cardiac function. This study assessed involvement of miRNAs-29 in CH of trained rats. Female Wistar rats (n = 7/group) were randomized into three groups: sedentary (S), training 1 (T1), training 2 (T2). T1: swimming sessions of 60 min/5 days/wk/10 wk. T2: similar to T1 until 8th wk. On the 9th wk rats swam 2x/day, and on the 10th wk 3x/day. MiRNAs analysis was performed by miRNA microarray and confirmed by real-time PCR. We assessed: markers of training, CH by ratio of left ventricle (LV) weight/body wt and cardiomyocytes diameter, pathological markers of CH (ANF, skeletal alpha-actin, alpha/beta-MHC), collagen I and III (COLIAI and COLIIIAI) by real-time PCR, protein collagen by hydroxyproline (OH-proline) concentration, CF and CH by echocardiography. Training improved aerobic capacity and induced CH. MiRNAs-1, 133a, and 133b were downregulated as observed in pathological CH, however, without pathological markers. MiRNA-29c expression increased in T1 (52%) and T2 (123%), correlated with a decrease in COLIAI and COLIIIAI expression in T1 (27%, 38%) and T2 (33%, 48%), respectively. MiRNA-29c was inversely correlated to OH-proline concentration (r = 0.61, P = 0.05). The E/A ratio increased in T2, indicating improved LV compliance. Thus, these results show that aerobic training increase miR-29 expression and decreased collagen gene expression and concentration in the heart, which is relevant to the improved LV compliance and beneficial cardiac effects, associated with aerobic high performance training.

Endurance exercise training ameliorates insulin resistance and reticulum stress in adipose and hepatic tissue in obese rats

Obesity-induced endoplasmatic reticulum (ER) stress has been demonstrated to underlie the induction of obesity-induced JNK and NF-kappa B activation inflammatory responses, and generation of peripheral insulin resistance. On the other hand, exercise has been used as a crucial tool in obese and diabetic patients, and may reduce inflammatory pathway stimulation. However, the ability of exercise training to reverse endoplasmatic reticulum stress in adipose and hepatic tissue in obesity has not been investigated in the literature. Here, we demonstrate that exercise training ameliorates ER stress and insulin resistance in DIO-induced rats. Rats were fed with standard rodent chow (3,948 kcal kg(-1)) or high-fat diet (5,358 kcal kg(-1)) for 2 months. After that rats were submitted to swimming training (1 h per day, 5 days for week with 5% overload of the body weight for 8 weeks). Samples from epididymal fat and liver were obtained and western blot analysis was performed. Our results showed that swimming protocol reduces pro-inflammatory molecules (JNK, I kappa B and NF-kappa B) in adipose and hepatic tissues. In addition, exercise leads to reduction in ER stress, by reducing PERK and eIF2 alpha phosphorylation in these tissues. In parallel, an increase in insulin pathway signaling was observed, as confirmed by increases in IR, IRSs and Akt phosphorylation following exercise training in DIO rats. Thus, results suggest that exercise can reduce ER stress, improving insulin resistance in adipose and hepatic tissue.

Nitric oxide inhibition in paraventricular nucleus on cardiovascular and autonomic modulation after exercise training in unanesthetized rats

It is well known that regular physical exercise alter cardiac function and autonomic modulation of heart rate variability (HRV). The paraventricular nucleus of hypothalamus (PVN) is an important site of integration for autonomic and cardiovascular responses, where nitric oxide (NO) plays an important role. The aim of our study was to evaluate the cardiovascular parameters and autonomic modulation by means of spectral analysis after nitric oxide synthase (NOS) inhibition in the PVN in conscious sedentary (S) or swimming trained (ST) rats. After swimming training protocol, adult male Wistar rats, instrumented with guide cannulas to PVN and femoral artery and vein catheters were submitted to mean arterial pressure (MAP) and heart rate (HR) recording. At baseline, the physical training induced a resting bradycardia (S: 374 +/- 5, ST: 346 +/- 1 bpm) and promoted adaptations in HRV characterized by an increase in high-frequency oscillations (HF; 26.43 +/- 6.91 to 88.96 +/- 244) and a decrease in low-frequency oscillations (LF; 73.57 +/- 6.91 to 11.04 +/- 2.44) in normalized units. The microinjection of N(omega)-nitro-L-arginine methyl ester (L-NAME) in the PVN of sedentary and trained rats promoted increase in MAP and HR. L-NAME in the PVN did not significantly alter the spectral parameters of HRV of sedentary animals, however in the trained rats increased LF oscillations (11.04 +/- 2.44 to 27.62 +/- 6.97) and decreased HF oscillations (88.96 +/- 2.44 to 72.38 +/- 6.97) in normalized units compared with baseline. Our results suggest that NO in the PVN may collaborate to cardiac autonomic modulation after exercise training. (c) 2010 Elsevier B.V. All rights reserved.

Immune cell changes in swimmers : response to acute exercise and training

O treino competitivo envolve exercício intenso e prolongado, capaz de modular o número e actividade das células imunitárias. Quando demasiado exigente poderá induzir fadiga e aumentar a susceptibilidade a doenças. Esta dissertação apresenta três estudos desenvolvidos no âmbito da Imunologia do Exercício, considerando a análise da resposta celular imunitária sistémica aguda e crónica ao exercício aplicada em situações reais do treino competitivo de natação, controlando factores passíveis de influenciar esta resposta. Pretendeu-se avaliar a resposta imunitária a uma sessão de treino prolongada e intensa, durante as 24h de recuperação (Estudo 1) e a uma época de treino com sete meses (Estudo 2), e estudar a influência de um macrociclo de treino de quatro meses sobre a resposta imunitária à mesma sessão de treino e período de recuperação (Estudo 3), controlando sexo, fases do ciclo menstrual, maturidade, escalão, especialidade, performance, cargas de treino e sintomas respiratórios superiores (URS). A sessão de treino induziu a diminuição da vigilância imunitária adquirida imediatamente e, pelo menos nas 2h seguintes. Juvenis e seniores recuperaram totalmente 24h depois, mas não os juniores, reforçando a ideia da existência de uma janela aberta para a infecção após exercícios prolongados e intensos e sugerindo uma recuperação menos eficiente para os juniores. No período de treino mais intenso da época observou-se uma imunodepressão e maior prevalência de URS. No final da época, a imunidade inata diminuiu aparentando maior sensibilidade aos efeitos cumulativos da carga de treino, enquanto a imunidade adquirida parece ter recuperado após o taper. O macrociclo de treino atenuou a resposta imunitária à sessão de treino e aumentou o período de janela aberta às infecções (efeitos mais acentuados nos adolescentes). Os resultados evidenciam a importância de controlar alterações imunitárias durante a época competitiva, especialmente em períodos de treino intenso e quando se realizam sessões de treino intensas consecutivas com recuperações inferiores a 24h.

Exercise training attenuates acute hyperalgesia in streptozotocin-induced diabetic female rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Exercise training increases myocardial inotropic response in food restricted rats

This study evaluated the effects of exercise training on myocardial function and ultrastructure of rats submitted to different levels of food restriction (FR). Male Wistar-Kyoto rats, 60 days old, were submitted to free access to food, light FR (20%), severe FR (50%) and/or to swimming training (one hour per day with 5% of load, five days per week for 90 days). Myocardial function was evaluated by left ventricular papillary muscle under basal condition (calcium 1.25 mM), and after extracellular calcium elevation to 5.2 mM and isoproterenol (I PM) addition. The ultrastructure of the myocardium was examined in the papillary muscle. The training effectiveness was verified by improvement of myocardial metabolic enzyme activities. Both 20% and 50% food restriction protocols presented minor body and ventricular weights gain. The 20%-FR, in sedentary or trained rats, did not alter myocardial function or ultrastructure. The 50%-FR, in sedentary rats, caused myocardial dysfunction under basal condition, decreased response to inotropic stimulation, and promoted myocardial ultrastructural damage. The 50%-FR, in exercised rats, increased myocardial dysfunction under basal condition but increased response to inotropic stimulation although there was myocardial ultrastructural damage. In conclusion, the exercise training in severe restriction caused marked myocardial dysfunction at basal condition but increased myocardial response to inotropic stimulation. (c) 2005 Elsevier B.V.. All rights reserved.

Effects of Exercise Training on Hippocampus Concentrations of Insulin and IGF-1 in Diabetic Rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Maximal lactate steady state in rats submitted to swimming exercise

The higher concentration during exercise at which lactate entry in blood equals its removal is known as 'maximal lactate steady state' (MLSS) and is considered an important indicator of endurance exercise capacity. The aim of the present study was to determine MLSS in rats during swimming exercise. Adult male Wistar rats, which were adapted to water for 3 weeks, were used. After this, the animals were separated at random into groups and submitted once a week to swimming sessions of 20 min, supporting loads of 5, 6, 7, 8, 9 or 10% of body wt. for 6 consecutive weeks. Blood lactate was determined every 5 min to find the MLSS. Sedentary animals presented MLSS with overloads of 5 and 6% at 5.5 mmol/l blood lactate. There was a significant (P < 0.05) increase in blood lactate with the other loads. In another set of experiments, rats of the same strain, sex and age were submitted daily to 60 min of swimming with an 8% body wt. overload, 5 days/week, for 9 weeks. The rats were then submitted to a swimming session of 20 min with an 8% body wt. overload and blood lactate was determined before the beginning of the session and after 10 and 20 min of exercise. Sedentary rats submitted to the same acute exercise protocol were used as a control. Physical training did not alter the MLSS value (P < 0.05) but shifted it to a higher exercise intensity (8% body wt. overload). Taken together these results indicate that MLSS measured in rats in the conditions of the present study was reproducible and seemed to be independent of the physical condition of the animals. © 2001 Elsevier B.V. All rights reserved.