Impaired cardiomyocyte contractility and calcium handling are hallmarks of left ventricular contractile dysfunction. Exercise training has been used as a remarkable strategy in the treatment of heart disease. The microRNA-1, which targets sodium/calcium exchanger 1 (NCX), and microRNA-214, which targets sarcoplasmic reticulum calcium ATPase-2a (Serca2a), are involved in cardiac function regulation. Thus, the aim of this study was to evaluate the effect of exercise training on cardiac microRNA-1 and −214 expression after myocardial infarction. Wistar rats were randomized into four groups: sedentary sham (S-SHAM), sedentary infarction (S-INF), trained sham (T-SHAM), and trained infarction (T-INF). Exercise training consisted of 60 min/days, 5 days/week for 10 weeks with 3 % of body weight as overload beginning four weeks after myocardial infarction. MicroRNA-1 and −214 expressions were, respectively, decreased (52 %) and increased (54 %) in the S-INF compared to the S-SHAM, while exercise training normalized the expression of these microRNAs. The microRNA targets NCX and Serca-2a protein expression were, respectively, decreased (55 %) and increased (34 %) in the T-INF group compared to the S-INF group. These results suggest that exercise training restores microRNA-1 and −214 expression levels and prevents change in both NCX and Serca-2a protein and gene expressions. Altogether, our data suggest a molecular mechanism to restore ventricular function after exercise training in myocardial infarction rats.

Aims: To determine the effects of resistance training (RT) on the expression of microRNA (miRNA)-214 and its target in sarcoplasmic reticulum Ca²⁺-ATPase (SERCA2a), and on the morphological and mechanical properties of isolated left ventricular myocytes. Main methods: Male Wistar rats were divided into two groups (n = 7/group): Control (CO) or trained (TR). The exercise-training protocol consisted of: 4 × 12 bouts, 5×/week during 8 weeks, with 80% of one repetition maximum. Key findings: RT increased the left ventricular myocyte width by 15% and volume by 12%, compared with control animals (p < 0.05). The time to half relaxation and time to peak were 8.4% and 4.4% lower, respectively, in cells from TR group as compared to CO group (p < 0.05). RT decreased miRNA-214 level by 18.5% while its target SERCA2a expression were 18.5% higher (p < 0.05). Significance: Our findings showed that RT increases single left ventricular myocyte dimensions and also leads to faster cell contraction and relaxation. These mechanical adaptations may be related to the augmented expression of SERCA2a which, in turn, may be associated with the epigenetic modification of decreased miRNA-214 expression.

O receptor de angiotensina II tipo I (AT1) tem uma importante participação no desenvolvimento da hipertrofia cardíaca. Em um trabalho publicado anteriormente, por nosso grupo, demonstramos que o bloqueio do receptor AT1 durante o treinamento de força inibiu a hipertrofia cardíaca em ratos. Por isso, o objetivo deste trabalho foi estudar a participação do receptor AT1 na ativação de vias de sinalização intracelular relacionadas com o aumento da síntese de proteína em ratos submetidos a uma sessão de exercício de força. Para isso, realizamos um experimento com seis grupos de animais (n = 6; cada): controle (Con), exercitado e sacrificado cinco minutos após o exercício (Exe 5), exercitado e sacrificado 30 minutos após o exercício (Exe 30), controle tratado com losartan (Con Los), tratado com losartan, exercitado e sacrificado cinco minutos após o exercício (Exe 5 Los), tratado com losartan, exercitado e sacrificado 30 minutos após o exercício (Exe 30 Los). Os resultados mostram que no grupo Exe 5 e Exe 30 ocorreu um aumento de 63% (P < 0,05) e 62% (P < 0,05), respectivamente, na fosforilação da proteína AKT comparado com o grupo controle. Enquanto a fosforilação da mTor foi aumentada 65% (P < 0,05) somente no grupo Exe 30 comparado com o grupo controle, sendo estes efeitos bloqueados pelo uso do losartan nos grupos Exe 5 Los e Exe 30 Los. Portanto, esses resultados, juntamente com nossos resultados prévios, demonstram que o receptor AT1 tem participação na ativação da AKT e mTOR após uma sessão de exercício de força.The angiotensin II type I (AT1) receptor has an important participation in the development of cardiac hypertrophy. Previously, we have shown that AT1 receptor participates in the cardiac hypertrophy induced by resistance training in rats. Here, we studied the involvement of AT1 receptor in the activation of intracellular signaling pathways related to the concentric HC in rats submitted to a session of strength exercise. Male Wistar rats were divided into 6 groups (n= 6 each): control (Con); exercised and killed 5 minutes after exercise (Exe 5); exercised and killed 30 minutes after exercise (Exe 30); control treated with Losartan (Con Los); treated with Losartan, exercised and killed 5 minutes after the exercise (Exe Los 5); treated with Losartan, exercised and killed 30 minutes after training (Exe Los 30). The results show that phosphorylation activity of AKT in group Exe 5 and Exe 30 increased 63% (P < 0.05) and 62% (P < 0.05), respectively, compared with Con. Whereas the phosphorylation of mTOR was increased 65% (P < 0.05), compared to Con, only in the group Exe 30. Furthermore, these effects were blocked by losartan treatment in groups Exe Los 5 and Exe Los 30. These results, together with ours previous data shows that the AT1 receptor has an role in the activation of AKT and mTOR pathway after a session of strength exercise