Resistance Exercise Training Mitigates Cardiac Remodeling Induced by a High-Fat Diet in Rodents: A Systematic Review. / O Treinamento Resistido Atenua a Remodelação Cardíaca Induzida por uma Dieta Hiperlipídica em Roedores: Uma Revisão Sistemática.

BACKGROUND: Obesity is associated with the development of cardiovascular diseases and is a serious public health problem. In animal models, high-fat diet (HFD) feeding impairs cardiac structure and function and promotes oxidative stress and apoptosis. Resistance exercise training (RT), however, has been recommended as coadjutant in the treatment of cardiometabolic diseases, including obesity, because it increases energy expenditure and stimulates lipolysis. OBJECTIVE: In this systematic review, we aimed to assess the benefits of RT on the heart of rats and mice fed HFD. METHODS: Original studies were identified by searching PubMed, Scopus, and Embase databases from December 2007 to December 2022. This study was conducted in accordance with the criteria established by PRISMA and registered in PROSPERO (CRD42022369217). The risk of bias and methodological quality was evaluated by SYRCLE and CAMARADES, respectively. Eligible studies included original articles published in English that evaluated cardiac outcomes in rodents submitted to over 4 weeks of RT and controlled by a sedentary, HFD-fed control group (n = 5). RESULTS: The results showed that RT mitigates cardiac oxidative stress, inflammation, and endoplasmic reticulum stress. It also modifies the activity of structural remodeling markers, although it does not alter biometric parameters, histomorphometric parameters, or the contractile function of cardiomyocytes. CONCLUSION: Our results indicate that RT partially counteracts the HFD-induced adverse cardiac remodeling by increasing the activity of structural remodeling markers; elevating mitochondrial biogenesis; reducing oxidative stress, inflammatory markers, and endoplasmic reticulum stress; and improving hemodynamic, anthropometric, and metabolic parameters.

FUNDAMENTO: A obesidade está associada ao desenvolvimento de doenças cardiovasculares e constitui um grave problema de saúde pública. Em modelos animais, a alimentação com uma dieta hiperlipídica (DH) compromete a estrutura e a função cardíaca e promove estresse oxidativo e apoptose. O treinamento resistido (TR), entretanto, tem sido recomendado como coadjuvante no tratamento de doenças cardiometabólicas, incluindo a obesidade, porque aumenta o gasto energético e estimula a lipólise. OBJETIVO: Na presente revisão sistemática, nosso objetivo foi avaliar os benefícios do TR no coração de ratos e camundongos alimentados com DH. MÉTODOS: Foram identificados estudos originais por meio de busca nas bases de dados PubMed, Scopus e Embase de dezembro de 2007 a dezembro de 2022. O presente estudo foi conduzido de acordo com os critérios estabelecidos pelo PRISMA e registrado no PROSPERO (CRD42022369217). O risco de viés e a qualidade metodológica foram avaliados pelo SYRCLE e CAMARADES, respectivamente. Os estudos elegíveis incluíram artigos originais publicados em inglês que avaliaram desfechos cardíacos em roedores submetidos a mais de 4 semanas de TR e controlados por um grupo controle sedentário alimentado com DH (n = 5). RESULTADOS: Os resultados mostraram que o TR atenua o estresse oxidativo cardíaco, a inflamação e o estresse do retículo endoplasmático. Também modifica a atividade de marcadores de remodelamento estrutural, apesar de não alterar parâmetros biométricos, parâmetros histomorfométricos ou a função contrátil dos cardiomiócitos. CONCLUSÃO: Nossos resultados indicam que o TR parcialmente neutraliza o remodelamento cardíaco adverso induzido pela DH, aumentando a atividade dos marcadores de remodelamento estrutural; elevando a biogênese mitocondrial; reduzindo o estresse oxidativo, marcadores inflamatórios e estresse do retículo endoplasmático; e melhorando os parâmetros hemodinâmicos, antropométricos e metabólicos.

Combined physical training protects the left ventricle from structural and functional damages in experimental pulmonary arterial hypertension.

BACKGROUND: Under the adverse remodeling of the right ventricle and interventricular septum in pulmonary arterial hypertension (PAH) the left ventricle (LV) dynamics is impaired. Despite the benefits of combined aerobic and resistance physical trainings to individuals with PAH, its impact on the LV is not fully understood. OBJECTIVE: To test whether moderate-intensity combined physical training performed during the development of PAH induced by MCT in rats is beneficial to the LV's structure and function. METHODS: Male Wistar rats were divided into two groups: Sedentary Hypertensive Survival (SHS, n = 7); and Exercise Hypertensive Survival (EHS, n = 7) to test survival. To investigate the effects of combined physical training, another group of rats were divided into three groups: Sedentary Control (SC, n = 7); Sedentary Hypertensive (SH, n = 7); and Exercise Hypertensive (EH, n = 7). PAH was induced through an intraperitoneal injection of MCT (60 mg/kg). Echocardiographic evaluations were conducted on the 22nd day after MCT administration. Animals in the EHS and EH groups participated in a combined physical training program, alternating aerobic (treadmill running: 50 min, 60% maximum running speed) and resistance (ladder climbing: 15 climbs with 1 min interval, 60% maximum carrying load) exercises, one session/day, 5 days/week for approximately 4 weeks. RESULTS: The physical training increased survival and tolerance to aerobic (i.e., maximum running speed) and resistance (i.e., maximum carrying load) exertions and prevented reductions in ejection fraction and fractional shortening. In addition, the physical training mitigated oxidative stress (i.e., CAT, SOD and MDA) and inhibited adverse LV remodeling (i.e., Collagen, extracellular matrix, and cell dimensions). Moreover, the physical training preserved the amplitude and velocity of contraction and hindered the reductions in the amplitude and velocity of the intracellular Ca2+ transient in LV single myocytes. CONCLUSION: Moderate-intensity combined physical training performed during the development of MCT-induced PAH in rats protects their LV from damages to its structure and function and hence increases their tolerance to physical exertion and prolongs their survival.

Is melatonin as an ergogenic hormone a myth? a systematic review and meta-analysis.

PURPOSE: Melatonin supplementation has been disclosed as an ergogenic substance. However, the effectiveness of melatonin supplementation in healthy subjects has not been systematically investigated. The present study analyzed the effects of melatonin supplementation on physical performance and recovery. In addition, it was investigated whether exercise bout or training alter melatonin secretion in athletes and exercise practitioners. METHODS: This systematic review and meta-analysis were conducted and reported according to the guidelines outlined in the PRISMA statement. Based on the search and inclusion criteria, 21 studies were included in the systematic review, and 19 were included in the meta-analysis. RESULTS: Melatonin supplementation did not affect aerobic performance relative to time trial (-0.04; 95% CI: -0.51 to 0.44) and relative to VO2 (0.00; 95% CI: -0.57 to 0.57). Also, melatonin supplementation did not affect strength performance (0.19; 95% CI: -0.28 to 0.65). Only Glutathione Peroxidase (GPx) secretion increased after melatonin supplementation (1.40; 95% CI: 0.29 to 2.51). Post-exercise melatonin secretion was not changed immediately after an exercise session (0.56; 95% CI: -0.29 to 1.41) and 60 min after exercise (0.56; 95% CI: -0.29 to 1.41). CONCLUSION: The data indicate that melatonin is not an ergogenic hormone. In contrast, melatonin supplementation improves post-exercise recovery, even without altering its secretion.

Effects of voluntary running on the skeletal muscle of rats with pulmonary artery hypertension.

The effects of voluntary running on the skeletal muscle of rats with pulmonary arterial hypertension (PAH) were tested in the present study. PAH was induced in rats by a single injection of monocrotaline (MCT, 60 mg/kg). Rats in the sedentary hypertension (HS) group had their tolerance to physical exertion reduced throughout the experiment, while those in the sedentary control (SC), exercise control (EC), exercise hypertension (EH) and median exercise (EM) groups maintained or increased. Despite that, the muscular citrate synthase activity was not different between groups. The survival time was higher in the EH (32 days) than in the SH (28 days) (p = 0.0032). SH and EH groups showed a lower percentage of muscle fiber and a higher percentage of extracellular matrix compared to control groups (p < 0.0001). However, the EM and EH groups presented higher percentage of muscle fiber and lower percentage of extracellular matrix than SH group (p < 0.0001). Regarding muscular gene expression, the SH and EM groups showed a lower expression of PGC1-α (p = 0.0024) and a higher expression of VEGF (p = 0.0033) compared to SC, while PGC1-α was elevated in the EH. No difference between groups was found for the carbonylated protein levels (p > 0.05), while the TNF-α/IL-10 ratio was augmented in the EH (p = 0.0277). In conclusion, voluntary running augments the proportion of fiber and affects the gene expression of inflammatory and mitochondrial biogenesis' markers in the skeletal muscle of rats with MCT-induced PAH, which benefits their survival and tolerance to physical effort.

Skeletal muscle dysfunctions in pulmonary arterial hypertension: Effects of aerobic exercise training.

Pulmonary arterial hypertension is associated with skeletal muscle myopathy and atrophy and impaired exercise tolerance. Aerobic exercise training has been recommended as a non-pharmacological therapy for deleterious effects imposed by pulmonary arterial hypertension. Aerobic physical training induces skeletal muscle adaptations via reduced inflammation, improved anabolic processes, decreased hypoxia and regulation of mitochondrial function. These benefits improve physical exertion tolerance and quality of life in patients with pulmonary arterial hypertension. However, the mechanisms underlying the therapeutic potential of aerobic exercise to skeletal muscle disfunctions in patients with pulmonary arterial hypertension are not well understood yet. This minireview highlights the pathways involved in skeletal muscle adaptations to aerobic exercise training in patients with pulmonary arterial hypertension.

Effects of β-hydroxy-β-methylbutyrate (hmb) and resistance training on body fat and lipid metabolism signaling pathways

ABSTRACT Excess body fat is a serious problem for increasing the risk of cardiovascular diseases such as obesity, compromising the health and quality of life of the population. In this sense, resistance training (RT) is type of physical exercise which improves body composition by increasing lean mass and reducing fat mass. RT in combination with nutrition (i.e. protein supplementation) is a key intervention to improve body fat metabolism and reducing obesity. Concerning protein supplementation, the β-hydroxy-β-methylbutyrate (HMB) is a metabolite of the branched-chain amino acid leucine that has demonstrated positive effects on body fat reduction. However, the effects of combining HMB supplementation with RT related to adipose tissue metabolic activity are controversial and warrant further investigation. This study analyzed the effects of HMB supplementation associated with RT on body fat concentration and lipid metabolism signaling pathways.

RESUMEN El exceso de grasa corporal es un problema grave que aumenta tu riesgo de enfermedades y problemas de salud, tales como enfermedad cardíaca, diabetes, presión arterial alta y ciertos tipos de cáncer. En este sentido, y dentro del ejercicio físico, el entrenamiento de resistencia (ER) es un tipo de entrenamiento con pesos que mejora la composición corporal aumentando la masa magra y perdiendo masa grasa. El ER asociado con la nutrición (ej. suplementación proteica) es una excelente intervención para mejorar el metabolismo de los lípidos al reducir la grasa corporal. En relación con la suplementación proteica el β-hidroxi-β-metilbutirato (HMB) es un metabolito del aminoácido de cadena ramificada esencial leucina que ha demostrado efectos positivos en la reducción de grasa corporal. Sin embargo, los efectos de la suplementación con HMB asociados con TR relacionados con la actividad metabólica del tejido adiposo son controvertidos y necesita la realización de investigaciones adicionales. Este estudio analizó los efectos de la suplementación con HMB asociados con TR en la concentración de grasa corporal y en las vías de señalización que participan en la regulación del metabolismo de los lípidos.

Effects of aerobic exercise training and açai supplementation on cardiac structure and function in rats submitted to a high-fat diet.

This study evaluated the effect of aerobic exercise training (AET) and supplementation with açai on cardiac structure and function in rats submitted to a high-fat diet. Two-month old Fischer male rats were divided into 5 groups: Control (C), High-fat Diet (H), High-fat Diet + Açai (HA), High-fat Diet + AET (HT), High-fat Diet + Açai + AET (HAT). The high-fat diet had 21.8% lard and 1% cholesterol (H and HT), or supplemented with 1% lyophilized açai pulp (HA and HAT). The HT and HAT groups performed AET on a treadmill (5 days/week, 1 h/day, 60% of the maximum running speed) for 8 weeks. Exercise tolerance test were performed, and adiposity index calculated. After euthanasia, the left ventricle (LV) was dissected and processed for histological, single myocyte intracellular calcium ([Ca2+]i) transient and contractility, oxidative stress and gene expression analysis. AET improved running capacity and reduced the adiposity index. Both AET and açai supplementation inhibited the increase in the LV collagen content, the deleterious effects on the [Ca2+]i transient and contractility in cardiomyocytes and the increment in oxidative stress, caused by the consumption of a high-fat diet. Aerobic exercise training and açai supplementation can mitigate damage caused by high-fat diet in cardiac structure and function, though the combination of treatments had no additional effects.

Aerobic Exercise Increases the Damage to the Femoral Properties of Growing Rats with Protein-Based Malnutrition

Abstract The present study investigated the effects of aerobic physical training on the femoral morphological, densitometric and biomechanical properties in growing male rats subjected to protein-based malnutrition. Four-week-old male Wistar rats were randomized into groups of 10 animals: Control Sedentary (CS), Control Trained (CT), Malnourished Sedentary (MS) and Malnourished Trained (MT). Control and malnourished animals received diets with 12% protein and 6% protein, respectively. The trained groups were submitted to a treadmill running program for 8 weeks. Total proteins and albumin were analyzed in the animals' blood plasma. Histological, densitometric and biomechanical analyzes were performed on the animals' femur. Body mass gain, physical performance, biochemical markers and the femoral morphological, densitometric and biomechanical properties were determined. Exercise tolerance increased in trained groups. Malnourished animals exhibited lower serum protein and albumin levels than controls. Porosity and trabecular bone density were not different between groups. The femoral maximum load, maximum load until fracture, resilience, stiffness, tenacity and densitometric properties were reduced by malnutrition. Physical training associated with malnutrition exacerbated the impairment in the femoral maximum load, maximum load until fracture, bone mineral content and density. Aerobic physical training worsens the damages induced by protein-based malnutrition in the femoral biomechanical and densitometric properties of growing male rats.

Mesenchymal stem cell therapy associated with endurance exercise training: Effects on the structural and functional remodeling of infarcted rat hearts.

We tested the effects of early mesenchymal stem cell (MSC) therapy associated with endurance exercise on the structural and functional cardiac remodeling of rats with myocardial infarctation (MI). Male Wistar rats (40 days old) were divided into 6 groups: control and exercise sham; control and exercise MI; and control and exercise MI MSC. MI was surgically induced and bone marrow-derived MSCs were immediately injected via caudal vein (concentration: 1 × 10(6 )cells). Twenty-four hours later ET groups exercised on a treadmill (5 days/week; 60 min/day; 60% of maximal running velocity) for 12 weeks. Structural and functional changes were determined by echocardiography. Contractility and intracellular global calcium ([Ca(2 +)]i) transient were measured in myocytes from the left ventricular (LV) non-infarcted area. Calcium regulatory proteins were measured by Western blot. MI increased (p < 0.05) heart, ventricular and LV weights and its ratios to body weight; LV internal dimension in diastole (LVID-D) and in systole (LVID-S) and LV free wall in diastole (LVFW-D), but reduced the thickness of interventricular septum in systole (IVS-S), ejection fraction (EF) and fractional shortening (FS). MI augmented (p < 0.05) the times to peak and to half relaxation of cell shortening as well as the amplitude of the [Ca(2 +)]i transient and the times to peak and to half decay. Early MSCs therapy restored LVFW-D, IVS-S and the amplitude and time to half decay of the [Ca(2 +)]i transient. Early endurance exercise intervention increased (p < 0.05) LVFW-S, IVS-S, EF and FS, and reduced the times to peak and to half relaxation of cell shortening, and the amplitude of the [Ca(2 +)]i transient. Exercise training also increased the expression of left ventricular SERCA2a and PLBser16. Nevertheless, the combination of these therapies did not cause additive effects. In conclusion, combining early MSCs therapy and endurance exercise does not potentiate the benefits of such treatments to structural and functional cardiac remodeling in infarcted rats.

Treinamento em corrida de baixa intensidade: propriedades estruturais e mecânicas da epífise proximal do fêmur de ratas osteopênicas / Low-intensity running training: structural and mechanical properties of the proximal femoral epiphysis in osteopenic female rats / Entrenamiento en carrera de baja intensidade: propriedades estructurales y mecánicas de la epífisis proximal femoral de ratas osteopénicas

Este estudo investigou os efeitos do treinamento em corrida de baixa intensidade (TCBI) sobre propriedades estruturais e mecânicas da epífise proximal do fêmur de ratas osteopênicas. Ratas Wistar [idade = 20 semanas; massa corporal = 271,42 ± 17,6 g] foram submetidas à ovariectomia (OVX) ou laparotomia (SHAM) e alocadas em quatro grupos: corrida OVX (CO, n = 12), controle OVX (CONO, n = 12), corrida SHAM (CS, n = 12) e controle SHAM (CONS, n = 12). Quinze dias pós-cirurgia, os grupos CO e CS foram submetidos ao TCBI em esteira (16 m/min, 60 min/dia, cinco dias/semana) por 10 semanas. O TCBI não alterou os efeitos deletérios da osteopenia induzida por ovariectomia sobre a densidade mineral do fêmur, a quantidade de osso trabecular no trocanter e colo do fêmur, a tenacidade e a força máxima de fratura do colo do fêmur de ratas.

This study investigated the effects of low-intensity running training (LIRT) on the structural and mechanical properties of the proximal femoral epiphysis in osteopenic female rats. Female Wistar rats [age = 20 weeks, body mass = 271.42 ± 17.6 g] were subjected to ovariectomy (OVX) or laparotomy (SHAM) and divided into four groups: running OVX (RO, n = 12), control OVX (CO, n = 12), running SHAM (RS, n = 12) and control SHAM (CS, n = 12). Two weeks after surgery RO and RS groups were submitted to a progressive LITR on a treadmill (60 min / day, 5 days / week) for 10 weeks. The LIRT did not alter the deleterious effects induced by ovariectomy on the femoral bone mineral density, the quantity of trabecular bone in the femoral great trocanter and neck, and femoral neck tenacity and resistance to fracture in female rats.

Este estudio investigó los efectos del entrenamiento en carera de baja intensidad (ECBI) en las propiedades estructurales y mecánicas de la epífisis proximal femoral de ratas osteopénicas. Ratas Wistar con edad de 20 semanas (peso corporal: 271.42 ± 17,6 g) fueran sometidas a ooforectomía (OVX) o laparotomía (SHAM) y asignados en cuatro grupos: carera OVX (CO, n = 12), control OVX (CONO, n = 12), carera SHAM (CS, n = 12) y control SHAM (CONS, n = 12). Quince días después de la cirugía los grupos CO y CS fueran sometidos al ECBI (16 m/ min; 60 min/día, 5 dias/semana) durante 10 semanas. El ECBI no cambió los efectos deletéreos de la osteopenia inducida por ooforectomía sobre la densidad mineral del fémur, la cantidad de hueso trabecular en el trocánter y cuello del fémur, la tenacidad y la resistencia ósea a la fractura del cuello del fémur de ratas.

Regional effects of low-intensity endurance training on structural and mechanical properties of rat ventricular myocytes.

We tested the effects of low-intensity endurance training (LIET) on the structural and mechanical properties of right (RV) and left ventricular (LV) myocytes. Male Wistar rats (4 mo old) were randomly divided into control (C, n = 7) and trained (T, n = 7, treadmill running at 50-60% of maximal running speed for 8 wk) groups. Isolated ventricular myocyte dimensions, contractility, Ca(2+) transients {intracellular Ca(2+) concentration ([Ca(2+)]i)}, and ventricular [Ca(2+)]i regulatory proteins were measured. LIET augmented cell length (C, 152.5 ± 2.0 µm vs. T, 162.2 ± 2.1 µm; P < 0.05) and volume (C, 5,162 ± 131 µm(3) vs. T, 5,506 ± 132 µm(3); P < 0.05) in the LV but not in the RV. LIET increased cell shortening (C, 7.5 ± 0.3% vs. T, 8.6 ± 0.3%; P < 0.05), the [Ca(2+)]i transient amplitude (C, 2.49 ± 0.06 F/F0 vs. T, 2.82 ± 0.06 F/F0; P < 0.05), the expression of sarcoplasmic reticulum Ca(2+)-ATPase 2a (C, 1.07 ± 0.13 vs. T, 1.59 ± 0.12; P < 0.05), and the levels of phosphorylated phospholamban at serine 16 (C, 0.99 ± 0.11 vs. T, 1.34 ± 0.10; P < 0.05), and reduced the total phospholamban-to-sarcoplasmic reticulum Ca(2+)-ATPase 2a ratio (C, 1.19 ± 0.15 vs. T, 0.40 ± 0.16; P < 0.05) in the LV without changing such parameters in the RV. In conclusion, LIET affected the structure and improved the mechanical properties of LV but not of RV myocytes in rats, helping to characterize the functional and morphological changes that accompany the endurance training-induced cardiac remodeling.

The benefits of endurance training in cardiomyocyte function in hypertensive rats are reversed within four weeks of detraining.

The aim of the present study was to verify the effects of low-intensity endurance training and detraining on the mechanical and molecular properties of cardiomyocytes from spontaneously hypertensive rats (SHRs). Male SHRs and normotensive control Wistar rats at 16-weeks of age were randomly divided into eight groups of eight animals: NC8 and HC8 (normotensive and hypertensive control for 8weeks); NT8 and HT8 (normotensive and hypertensive trained at 50-60% of maximal exercise capacity for 8weeks); NC12 and HC12 (normotensive and hypertensive control for 12weeks); NDT and HDT (normotensive and hypertensive trained for 8weeks and detrained for 4weeks). The total exercise time until fatigue (TTF) was determined by a maximal exercise capacity test. Resting heart rate (RHR) and systolic arterial pressure (SAP) were measured. After the treatments, animals were killed by cervical dislocation and left ventricular myocytes were isolated by enzymatic dispersion. Isolated cells were used to determine intracellular global Ca(2+) ([Ca(2+)]i) transient and cardiomyocyte contractility (1Hz; ~25°C). [Ca(2+)]i regulatory proteins were measured by Western blot, and the markers of pathologic cardiac hypertrophy by quantitative real-time polymerase chain reaction (q-RT-PCR). Exercise training augmented the TTF (NC8, 11.4±1.5min vs. NT8, 22.5±1.4min; HC8, 11.7±1.4min vs. HT8, 24.5±1.3min; P<0.05), reduced RHR (NT8initial, 340±8bpm vs. NT8final, 322±10bpm; HT8initial, 369±8bpm vs. HT8final, 344±10bpm; P<0.05), and SBP in SHR animals (HC8, 178±3mmHg vs. HT8, 161±4mmHg; P<0.05). HC8 rats showed a slower [Ca(2+)]i transient (Tpeak, 83.7±1.8ms vs. 71.7±2.4ms; T50%decay, 284.0±4.3ms vs. 264.0±4.1ms; P<0.05) and cell contractility (Vshortening, 86.1±6.7µm/s vs. 118.6±6.7µm/s; Vrelengthening, 57.5±7.4µm/s vs. 101.3±7.4µm/s; P<0.05), and higher expression of ANF (300%; P<0.05), skeletal α-actin (250%; P<0.05) and a decreased α/ß-MHC ratio (70%; P<0.05) compared to NC8. Exercise training increased [Ca(2+)]i transient (NC8, 2.39±0.06F/F0 vs. NT8, 2.72±0.06F/F0; HC8, 2.28±0.05F/F0 vs. HT8, 2.82±0.05F/F0; P<0.05), and cell contractility (NC8, 7.4±0.3% vs. NT8, 8.4±0.3%; HC8, 6.8±0.3% vs. HT8, 7.8±0.3%; P<0.05). Furthermore, exercise normalized the expression of ANF, skeletal α-actin, and the α/ß-MHC ratio in HT8 rats, augmented the expression of SERCA2a (NC8, 0.93±0.15 vs. NT8, 1.49±0.14; HC8, 0.83±0.13 vs. HT8, 1.32±0.14; P<0.05) and PLBser16 (NC8, 0.89±0.18 vs. NT8, 1.23±0.17; HC8, 0.77±0.17 vs. HT8, 1.32±0.16; P<0.05), and reduced PLBt/SERCA2a (NC8, 1.21±0.19 vs. NT8, 0.50±0.21; HC8, 1.38±0.17 vs. HT8, 0.66±0.21; P<0.05). However, all these adaptations returned to control values within 4weeks of detraining in both SHR and normotensive control animals. In conclusion, low-intensity endurance training induces positive benefits to left ventricular myocyte mechanical and molecular properties, which are reversed within 4weeks of detraining.

Morfologia e contratilidade em cardiomiócitos de ratos com baixo desempenho para o exercício físico / Morphology and contractility in cardiomyocytes of rats with low exercise performance

FUNDAMENTO: A capacidade aeróbica é fundamental para o desempenho físico, e a baixa capacidade aeróbica está relacionada ao desencadeamento de diversas doenças cardiovasculares. OBJETIVO: Comparar a contratilidade e a morfologia de cardiomiócitos isolados de ratos com baixo desempenho e desempenho padrão para o exercício físico. MÉTODOS: Ratos Wistar, com 10 semanas de idade, foram submetidos a um protocolo de corrida em esteira até a fadiga, e foram divididos em dois grupos: Baixo Desempenho (BD) e Desempenho Padrão (DP). Em seguida, após eutanásia, o coração foi removido rapidamente e, por meio de dissociação enzimática, os cardiomiócitos do ventrículo esquerdo foram isolados. O comprimento celular e dos sarcômeros e a largura dos cardiomiócitos foram medidos usando-se um sistema de detecção de bordas. Os cardiomiócitos isolados foram estimulados eletricamente a 1 e 3 Hz e a contração celular foi medida registrando-se a alteração do seu comprimento. RESULTADOS: O comprimento celular foi menor no grupo BD (157,2 ± 1,3µm; p < 0,05) em relação ao DP (161,4 ± 1,3 µm), sendo o mesmo resultado observado para o volume dos cardiomiócitos (BD, 25,5 ± 0,4 vs. DP, 26,8 ± 0,4 pL; p < 0,05). Os tempos para o pico de contração (BD, 116 ± 1 vs. DP, 111 ± 2ms) e para o relaxamento total (BD, 143 ± 3 vs. DP, 232 ± 3 ms) foram maiores no grupo BD. CONCLUSÃO: Conclui-se que os miócitos do ventrículo esquerdo dos animais de baixo desempenho para o exercício físico apresentam menores dimensões que os dos animais de desempenho padrão, além de apresentarem perdas na capacidade contrátil.

BACKGROUND: Aerobic capacity is essential to physical performance, and low aerobic capacity is related to the triggering of various cardiovascular diseases. OBJECTIVE: To compare the morphology and contractility of isolated rat cardiomyocytes with low performance and standard performance for exercise. METHODS: Wistar rats with 10 weeks of age underwent a protocol of treadmill running to fatigue, and were divided into two groups: Low Performance (LP) and Standard Performance (SP). Then, the animals were sacrificed, the heart was quickly removed and, by means of enzymatic dissociation, left ventricular cardiomyocytes were isolated. The cell and sarcomeres length and width of cardiomyocytes were measured using an edge detection system. The isolated cardiomyocytes were electrically stimulated at 1 and 3 Hz and cell contraction was measured by registering the change of their length. RESULTS: The cell length was shorter in the LP group (157.2 1.3µm; p < 0.05) compared to SP (161.4 1.3µm), and the same result was observed for the volume of cardiomyocytes (LP, 25.5 0.4. vs. SP, 26.8 ± 0.4 pL; p < 0.05). The time to peak contraction (LP, 116 1 vs. SP 111 2ms) and total relaxation (LP, 143 3 vs. SP 232 3ms) were higher in the LP group. CONCLUSION: We conclude that left ventricular myocytes of animals with low performance for exercise are smaller than animals with standard performance. In addition to that, they present losses in contractile capacity.

Morphology and contractility in cardiomyocytes of rats with low exercise performance.

BACKGROUND: Aerobic capacity is essential to physical performance, and low aerobic capacity is related to the triggering of various cardiovascular diseases. OBJECTIVE: To compare the morphology and contractility of isolated rat cardiomyocytes with low performance and standard performance for exercise. METHODS: Wistar rats with 10 weeks of age underwent a protocol of treadmill running to fatigue, and were divided into two groups: Low Performance (LP) and Standard Performance (SP). Then, the animals were sacrificed, the heart was quickly removed and, by means of enzymatic dissociation, left ventricular cardiomyocytes were isolated. The cell and sarcomeres length and width of cardiomyocytes were measured using an edge detection system. The isolated cardiomyocytes were electrically stimulated at 1 and 3 Hz and cell contraction was measured by registering the change of their length. RESULTS: The cell length was shorter in the LP group (157.2 ± 1.3 µm; p < 0.05) compared to SP (161.4 ± 1.3 µm), and the same result was observed for the volume of cardiomyocytes (LP, 25.5 ± 0.4 vs. SP, 26.8 ± 0.4 pL; p < 0.05). The time to peak contraction (LP, 116 ± 1 vs. SP 111 ± 2 ms) and total relaxation (LP, 143 ± 3 vs. SP 232 ± 3 ms) were higher in the LP group. CONCLUSION: We conclude that left ventricular myocytes of animals with low performance for exercise are smaller than animals with standard performance. In addition to that, they present losses in contractile capacity.