Effects of exercise training on atrophy gene expression in skeletal muscle of mice with chronic allergic lung inflammation

We evaluated the effects of chronic allergic airway inflammation and of treadmill training (12 weeks) of low and moderate intensity on muscle fiber cross-sectional area and mRNA levels of atrogin-1 and MuRF1 in the mouse tibialis anterior muscle. Six 4-month-old male BALB/c mice (28.5 ± 0.8 g) per group were examined: 1) control, non-sensitized and non-trained (C); 2) ovalbumin sensitized (OA, 20 µg per mouse); 3) non-sensitized and trained at 50 percent maximum speed _ low intensity (PT50 percent); 4) non-sensitized and trained at 75 percent maximum speed _ moderate intensity (PT75 percent); 5) OA-sensitized and trained at 50 percent (OA+PT50 percent), 6) OA-sensitized and trained at 75 percent (OA+PT75 percent). There was no difference in muscle fiber cross-sectional area among groups and no difference in atrogin-1 and MuRF1 expression between C and OA groups. All exercised groups showed significantly decreased expression of atrogin-1 compared to C (1.01 ± 0.2-fold): PT50 percent = 0.71 ± 0.12-fold; OA+PT50 percent = 0.74 ± 0.03-fold; PT75 percent = 0.71 ± 0.09-fold; OA+PT75 percent = 0.74 ± 0.09-fold. Similarly significant results were obtained regarding MuRF1 gene expression compared to C (1.01 ± 0.23-fold): PT50 percent = 0.53 ± 0.20-fold; OA+PT50 percent = 0.55 ± 0.11-fold; PT75 percent = 0.35 ± 0.15-fold; OA+PT75 percent = 0.37 ± 0.08-fold. A short period of OA did not induce skeletal muscle atrophy in the mouse tibialis anterior muscle and aerobic training at low and moderate intensity negatively regulates the atrophy pathway in skeletal muscle of healthy mice or mice with allergic lung inflammation.

The effect of a low dose of clenbuterol on rat soleus muscle submitted to joint immobilization

The aim of the present study was to evaluate the effect of joint immobilization on morphometric parameters and glycogen content of soleus muscle treated with clenbuterol. Male Wistar (3-4 months old) rats were divided into 4 groups (N = 6 for each group): control, clenbuterol, immobilized, and immobilized treated with clenbuterol. Immobilization was performed with acrylic resin orthoses and 10 µg/kg body weight clenbuterol was administered subcutaneously for 7 days. The following parameters were measured the next day on soleus muscle: weight, glycogen content, cross-sectional area, and connective tissue content. The clenbuterol group showed an increase in glycogen (81.6 percent, 0.38 ± 0.09 vs 0.69 ± 0.06 mg/100 g; P < 0.05) without alteration in weight, cross-sectional area or connective tissue compared with the control group. The immobilized group showed a reduction in muscle weight (34.2 percent, 123.5 ± 5.3 vs 81.3 ± 4.6 mg; P < 0.05), glycogen content (31.6 percent, 0.38 ± 0.09 vs 0.26 ± 0.05 mg/100 mg; P < 0.05) and cross-sectional area (44.1 percent, 2574.9 ± 560.2 vs 1438.1 ± 352.2 µm²; P < 0.05) and an increase in connective tissue (216.5 percent, 8.82 ± 3.55 vs 27.92 ± 5.36 percent; P < 0.05). However, the immobilized + clenbuterol group showed an increase in weight (15.9 percent; 81.3 ± 4.6 vs 94.2 ± 4.3 mg; P < 0.05), glycogen content (92.3 percent, 0.26 ± 0.05 vs 0.50 ± 0.17 mg/100 mg; P < 0.05), and cross-sectional area (19.9 percent, 1438.1 ± 352.2 vs 1724.8 ± 365.5 µm²; P < 0.05) and a reduction in connective tissue (52.2 percent, 27.92 ± 5.36 vs 13.34 ± 6.86 percent; P < 0.05). Statistical analysis was performed using Kolmogorov-Smirnov and homoscedasticity tests. For the muscle weight and muscle glycogen content, two-way ANOVA and the Tukey test were used. For the cross-sectional area and connective tissue content, Kruskal-Wallis and Tukey tests were used. This study emphasizes the importance of anabolic pharmacological...

Curto período de imobilização provoca alterações morfométricas e mecânicas no músculo de rato / Short-term immobilization causes morphometric and mechanical alterations in rat muscles

OBJETIVO: Analisar as características morfométricas e mecânicas dos músculos sóleo e gastrocnêmio após imobilização na posição de encurtamento. MÉTODO: 20 ratos Wistar (250 ± 20g) foram distribuídos igualmente em grupos imobilizado e controle. A imobilização foi realizada no membro posterior esquerdo por meio de órtese de resina acrílica, com a articulação do tornozelo em flexão plantar máxima. Após 7 dias da imobilização, a massa muscular, número e comprimento de sarcômeros em série, área das fibras musculares, densidade de área de tecido conjuntivo intramuscular e força máxima de ruptura do tríceps sural foram avaliados. Os dados foram analisados pela ANOVA e teste de Tukey (p< 0,05). RESULTADOS: O músculo sóleo imobilizado apresentou alterações em todas as variáveis morfométricas analisadas, enquanto que, no músculo gastrocnêmio, algumas adaptações não foram observadas. Na análise do ensaio de tração, o grupo imobilizado apresentou redução de 20 por cento na força máxima de ruptura muscular. CONCLUSÃO: Os resultados deste estudo revelaram que curto período de imobilização promove alterações nos parâmetros morfométricos das fibras musculares, com repercussões na mecânica muscular. Tais resultados permitem sugerir a necessidade da reabilitação em músculos submetidos à imobilização, mesmo a curto prazo, para que a mesma possibilite o retorno precoce das características musculares normais.

OBJECTIVE: to analyze the morphometric and mechanical characteristics of the soleus and gastrocnemius muscles after immobilization in a shortened position. METHODS: 20 Wistar rats (250 ± 20g) were divided equally into immobilized and control groups. The left hind limb was immobilized by means of an acrylic resin orthosis, with the ankle joint at maximum plantar flexion. After seven days of immobilization, the muscle mass, number and length of sarcomeres in series, muscle fiber cross-sectional area, density of the intramuscular connective tissue area and tensile strength of the triceps surae muscle were evaluated. The data were analyzed by the ANOVA and Tukey tests (p< 0.05). RESULTS: The immobilized soleus muscle presented changes in all the morphometric variables analyzed, while some of these changes were not observed in the gastrocnemius muscle. Analysis of the traction test showed that the immobilized group presented a 20 percent decrease in the maximum tensile muscle strength. CONCLUSION: The results from this study showed that short-term immobilization causes changes to the morphometric parameters of the muscle fibers, with repercussions on muscle mechanics. These results suggest the need for rehabilitation of muscles subjected to immobilization, even if only for a short period, in order to achieve early recovery of normal muscle characteristics.

Efeitos da estimulação elétrica neuromuscular sobre o membro posterior imobilizado de ratos durante 15 dias: análises metabólicas e morfométricas / Effects of neuromuscular electrical stimulation on rat hind limbs immobilized for 15 days: metabolic and morphometric analyses

OBJETIVO: Avaliar o efeito da estimulação elétrica (EE) sobre o perfil metabólico e morfométrico dos músculos do membro posterior de ratos submetidos à imobilização durante 15 dias. MÉTODO: Ratos Wistar foram divididos em 3 grupos (n=5): controle, imobilizado por 15 dias e imobilizado associado à EE por 15 dias. Foram avaliados: reserva de glicogênio (RG) dos músculos sóleo (S), extensor longo dos dedos (ELD), gastrocnêmio branco (GB), gastrocnêmio vermelho (GV) e tibial anterior (TA), além do peso do sóleo, área das fibras e tecido conjuntivo do S. A análise estatística foi feita pelos testes ANOVA e Kruskal-Wallis (p<0,05). RESULTADOS: A imobilização promoveu alterações significativas (p<0,05) como: redução nas RG (S: 44,73 por cento, GB: 47,82 por cento, GV: 46,34 por cento, ELD: 41,66 por cento, TA: 48,38 por cento), no peso (7,2 por cento) e na área das fibras (35 por cento) do S, além do aumento da densidade do tecido conjuntivo (160 por cento). A EE promoveu aumento significativo (p<0,05) nas RG de todos os músculos imobilizados (S: 90,47 por cento, GB: 62,5 por cento, GV: 95,45 por cento, ELD: 76,19 por cento, TA: 56,25 por cento), no peso (20,94 por cento) e na área das fibras (19,65 por cento) do S e também promoveu redução significativa (15,38 por cento, p<0,05) na densidade do tecido conjuntivo. CONCLUSÕES: A EE minimizou a redução das RG, preveniu a redução da área das fibras e a proliferação do tecido conjuntivo nos músculos submetidos à imobilização.

OBJECTIVE: To evaluate the effect of electrical stimulation on the metabolic and morphometric profile of rat hind limb muscles subjected to immobilization for 15 days. METHOD: Wistar rats were divided into three groups (n=5): control; immobilized for 15 days; and immobilized for 15 days with electrical stimulation. The glycogen reserves of the soleus, extensor digitorum longus (EDL), white gastrocnemius (WG), red gastrocnemius (RG) and tibialis anterior (TA) muscles were evaluated, along with the weight, fibrous area and conjunctive tissue of the soleus. The statistical analysis was performed using the Anova and Kruskal-Wallis tests (p<0.05). RESULTS: Immobilization promoted significant alterations (p<0.05), such as: reductions in the glycogen reserves (soleus: 44.73 percent, WG: 47.82 percent, RG: 46.34 percent, EDL: 41.66 percent, TA: 48.38 percent) and in the weight (7.2 percent) and fibrous area (35 percent) of the soleus, and also increased connective tissue density (160 percent). Electrical stimulation promoted a significant increase (p<0.05) in the glycogen reserves of all the immobilized muscles: (soleus: 90.47 percent, WG: 62.5 percent, RG: 95.45 percent, EDL: 76.19 percent, TA: 56.25 percent) and in the weight (20.94 percent) and fibrous area (19.65 percent) of the soleus, and also promoted a significant reduction (15.38 percent, p<0.05) in connective tissue density. CONCLUSION: Electrical stimulation minimized the reduction in glycogen reserves and prevented the reduction in fibrous area and proliferation of connective tissue in the muscles subjected to immobilization.

Rat hindlimb joint immobilization with acrylic resin orthoses

The objective of the present study was to propose an orthosis of light material that would be functional for the animal and that would maintain only the ankle joint immobilized. Male Wistar rats (3 to 4 months old, 250-300 g) were divided into 2 groups (N = 6): control and immobilized for 7 days. Rats were anesthetized with sodium pentobarbital (40 mg/kg weight) and the left hindlimb was immobilized with the orthoses composed of acrylic resin model, abdominal belt and lateral supports. The following analyses were performed: glycogen content of the soleus, extensor digitorum longus, white gastrocnemius, red gastrocnemius, and tibialis anterior muscles by the phenol sulfuric method, and the weight, fiber area and intramuscular connective tissue of the soleus by the planimetric system. Data were analyzed statistically by the Kolmogorov-Smirnov, Student t and Wilcoxon tests. Immobilization decreased glycogen in all muscles (P < 0.05; soleus: 31.6 percent, white gastrocnemius: 56.6 percent, red gastrocnemius: 39 percent, extensor digitorum longus: 41.7 percent, tibialis anterior: 45.2 percent) in addition to reducing soleus weight by 34 percent (P < 0.05). Furthermore, immobilization promoted reduction of the fiber area (43 percent, P < 0.05) and increased the connective tissue (200 percent, P < 0.05). The orthosis model was efficient comparing with another alternative immobilization model, like plaster casts, in promoting skeletal muscle alterations, indicating that it could be used as a new model in other studies related to muscle disuse.