Expression of myostatin, myostatin receptors and follistatin in diabetic rats submitted to exercise.

Myostatin (MSTN) has been implicated in metabolic adaptation to physiological stimuli, such as physical exercise, which is linked to improved glucose homeostasis. The aim of the present study was to evaluate the influence of exercise on the expression of MSTN, MSTN receptors (ActRIIB and ALK4) and follistatin (FS) in the muscle and fat of streptozotocin-induced diabetic rats. Control and diabetic rats were randomly assigned to a swimming training group (EC and ED, respectively) and a sedentary group (SC and SD, respectively). Exercising animals swam for 45 min at 0900 and 1700 hours, 5 day/week, for 4 weeks. The mRNA expression of MSTN, ActRIIB, ALK4 and FS mRNA was quantified by real-time reverse transcription-polymerase chain reaction. Expression of MSTN and FS mRNA increased in the muscle and subcutaneous fat of SD compared with SC rats. Expression of ActRIIB mRNA was increased in the muscle, mesenteric fat and brown adipose tissue (BAT) of SD compared with SC rats, whereas ALK4 mRNA expression was only increased in the BAT of SD compared with SC rats. After training, MSTN and ActRIIB expression was lower in the BAT of EC compared with SC rats. Expression of MSTN mRNA increased in the mesenteric fat of ED compared with SD rats, whereas FS mRNA expression decreased in the muscle, mesenteric and subcutaneous fat and BAT. Lower ALK4 mRNA expression was noted in the BAT of ED compared with SD rats. These results indicate that MSTN, its receptors and FS expression change in both the muscle and fat of diabetic rats and that the expression of these factors can be modulated by exercise in diabetes.

Endocytosis of pulchellin and its recombinant B-chain into K-562 cells: binding and uptake studies.

Most of the type 2 ribosome-inactivating proteins (RIPs) are toxins formed by an RNA-N-glycosidase A-chain polypeptide linked to a lectin B-chain by a single disulfide bond. Members of this protein class vary greatly in cytotoxity, correlating more with B-chain diversity rather than to A-chain differences. Pulchellin is a type 2 ribosome-inactivating protein toxin found in the seeds of Abrus pulchellus tenuiflorus. Recombinant pulchellin B-Chain (rPBC) has been previously produced as inclusion bodies in Escherichia coli and successfully refolded recovering biological activity. New approaches for using this kind of protein as a biotechnological tool require a better understanding of cell targeting, binding, uptake, intracellular routing and delivery. In this work, cell adhesion experiments were used to determine the interaction of rPBC with mammalian cells. Fluorescence and confocal microscopy revealed the intracellular localization and trafficking. Subcellular sorting of the native pulchellin could also be determined. The results support that the endosomal internalization pathway and the retrograde transport through the Golgi apparatus might be used by both native protein and rPBC.

[Nandrolone administration does not promote hypertrophy of soleus muscle in rats]. / A administração de nandrolona não promove hipertrofia do músculo sóleo em ratos.

Anabolic androgenic steroids (AAS) are compounds formed from testosterone or one of its derivatives, which are largely used by amateur e professional athletes to improve the athletic performance. However, the scientific information about the relation between the use of AAS and muscle hypertrophy is controversial. The aim of this study was to evaluate the effects of testosterone and physical training on muscle hypertrophy. Male Wistar rats received i.m. injections of Deca-Durabolin or vehicle during 6 weeks. Trained rats were submitted to a resistance physical training, by jumping up and down in water carrying an overload. Sedentary and trained animals were anesthetized and sacrificed. Soleus muscle was removed for the quantification of total protein and DNA concentration. In the end of the treatment, body weight of trained animals treated with vehicle or AAS was lower than the body weight of respective sedentary. Total protein concentration and the ratio muscle weight/body weight of all experimental groups were not altered. Trained group treated with AAS presented lower DNA concentration than trained group treated with vehicle. The administration of nandrolone decanoate did not promote hypertrophy on soleus muscle, not even when the use of AAS was associated to resistance physical training.

A administração de nandrolona não promove hipertrofia do músculo sóleo em ratos / Nandrolone administration does not promote hypertrophy of soleus muscle in rats

Os esteróides anabólicos androgênicos (EAA) são compostos formados a partir da testosterona ou um de seus derivados, sendo amplamente utilizados por desportistas amadores e profissionais com o objetivo de melhorar a performance atlética. Entretanto, a literatura a respeito da relação entre EAA e hipertrofia muscular é controversa. O objetivo deste estudo foi avaliar os efeitos da nandrolona e do treinamento físico sobre a hipertrofia muscular. Ratos Wistar machos receberam injeção i.m. de Deca-Durabolin® ou veículo durante 6 semanas. Os animais dos grupos treinados foram submetidos a treinamento físico resistido, através de sessões de saltos em meio líquido. Os animais sedentários e treinados foram sacrificados após anestesia e o músculo sóleo retirado para quantificação de proteínas totais e DNA. Ao final do tratamento, os animais treinados tratados com veículo ou EAA apresentaram menor peso corporal do que os respectivos grupos sedentários. Não foram observadas diferenças estatísticas na concentração de proteínas totais e na razão peso muscular/peso corporal entre os grupos experimentais. O grupo treinado tratado com EAA apresentou concentração de DNA significativamente menor do que o grupo treinado veículo. A administração de decanoato de nandrolona não promoveu hipertrofia do músculo sóleo, nem mesmo quando associada ao treinamento físico resistido.