August 7, 2020PLoS ONEOpen Access

Resistance training prevents right ventricle hypertrophy in rats exposed to secondhand cigarette smoke

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Why the study?

Secondhand cigarette smoke exposure causes diverse diseases, and it was unknown whether resistance training prevents right ventricle wall thickening induced by secondhand smoke exposure.

Does resistance training prevent right ventricle hypertrophy in rats exposed to secondhand cigarette smoke?

Structured PICO

Does resistance training prevent right ventricle hypertrophy in rats exposed to secondhand cigarette smoke?

Population

32 male Wistar rats, aged 45 days

Intervention

Resistance training (climbing a vertical ladder with progressive load, once a day, 5 days a week) for 16 weeks, with or without secondhand cigarette smoke exposure (smoke of 4 cigarettes for 30 min, twice daily, 5 days a week)

Comparator

Sedentary control (no intervention) and sedentary smoke-exposed rats

Outcome

Right ventricle wall thickness measured by histopathological analysissurrogate

Resistance training prevents right ventricular hypertrophy in rats exposed to secondhand cigarette smoke, though it may negatively impact skeletal muscle fiber diameter in this population.

Limitations

Did not perform right cardiac catheterization (RCC) and transthoracic echocardiography (ET) for detection of pulmonary hypertension
Did not study reactive oxygen species (ROS)
Did not characterize the specific type of macrophages in the liver

Implication

RT may attenuate smoke-induced RV remodeling in rats; leaves open whether benefits translate to humans.

Abstract

Exposure to secondhand cigarette smoke is associated with the development of diverse diseases. Resistance training has been considered one of the most useful tools for patients with pulmonary disease, improving their quality of life. This study aimed to evaluate the effect of resistance training (RT) on the prevention of thickening of the right ventricle wall of rats exposed to secondhand cigarette smoke. Thirty-two Wistar rats were divided into four groups: Control (C), Smoker (S), Exercised (E) and Exercised Smoker (ES). The smoker groups were exposed to the smoke of four cigarettes for 30 min, twice daily, five days a week, for 16 weeks. The exercised groups climbed on a vertical ladder with progressive load, once a day, five days a week, for 16 weeks. The heart, trachea, lung, liver and gastrocnemius muscle were removed for histopathological analysis. Pulmonary emphysema (S and ES vs C and E, P < 0.0001) and pulmonary artery thickness enlargement (S vs C and E, P = 0.003, ES vs C, P = 0.003) were detected in the smoking groups. There was an increase in the right ventricle thickness in the S group compared with all other groups (P < 0.0001). An increase in resident macrophages in the liver was detected in both smoking groups compared with the C group (P = 0.002). Additionally, a relevant reduction of the diameter of the muscle fibers was detected only in ES compared with the C, S and E groups (P = 0.0002), impairing, at least in part, the muscle mass in exercised smoking rats. Therefore, it was concluded that resistance training prevented the increase of thickness of the right ventricle in rats exposed to secondhand cigarette smoke, but it may be not so beneficial for the skeletal muscle of smoking rats.