Effects of Nandrolone in the Counteraction of Skeletal Muscle Atrophy in a Mouse Model of Muscle Disuse: Molecular Biology and Functional Evaluation

Abstract

Muscle disuse produces severe atrophy and a slow-to-fast phenotype transition in the postural Soleus (Sol) muscle of rodents. Antioxidants, amino-acids and growth factors were ineffective to ameliorate muscle atrophy. Here we evaluate the effects of nandrolone (ND), an anabolic steroid, on mouse skeletal muscle atrophy induced by hindlimb unloading (HU). Mice were pre-treated for 2-weeks before HU and during the 2-weeks of HU. Muscle weight and total protein content were reduced in HU mice and a restoration of these parameters was found in ND-treated HU mice. The analysis of gene expression by real-time PCR demonstrates an increase of MuRF-1 during HU but minor involvement of other catabolic pathways. However, ND did not affect MuRF-1 expression. The evaluation of anabolic pathways showed no change in mTOR and eIF2-kinase mRNA expression, but the protein expression of the eukaryotic initiation factor eIF2 was reduced during HU and restored by ND. Moreover we found an involvement of regenerative pathways, since the increase of MyoD observed after HU suggests the promotion of myogenic stem cell differentiation in response to atrophy. At the same time, Notch-1 expression was down-regulated. Interestingly, the ND treatment prevented changes in MyoD and Notch-1 expression. On the contrary, there was no evidence for an effect of ND on the change of muscle phenotype induced by HU, since no effect of treatment was observed on the resting gCl, restCa and contractile properties in Sol muscle. Accordingly, PGC1α and myosin heavy chain expression, indexes of the phenotype transition, were not restored in ND-treated HU mice. We hypothesize that ND is unable to directly affect the phenotype transition when the specialized motor unit firing pattern of stimulation is lacking. Nevertheless, through stimulation of protein synthesis, ND preserves protein content and muscle weight, which may result advantageous to the affected skeletal muscle for functional recovery.

Costamere protein expression and tissue composition of rotator cuff muscle after tendon release in sheep

“…3). It was shown previously that nandrolone reduces unloading‐induced loss of muscle protein content in mice 19. The present study confirmed this also occurs with RC tendon release in sheep.…”

“…To our knowledge, the action of anabolic steroids on the costamere is not yet described after tendon release. Nevertheless, nandrolone decreased cytosolic Ca 2+ in the mouse m. soleus after hindlimb unloading 19. This may result in lower Ca 2+ ‐activated protease activity and thereby decreased costamere cleavage, which potentially explains protection from muscle loss 10, 12, 20.…”

Growth hormone secretagogues prevent dysregulation of skeletal muscle calcium homeostasis in a rat model of cisplatin‐induced cachexia

“…Resting ionic conductances and muscle excitability are considered ex vivo functional outcomes in conditions of muscle calcium dysregulation . Thus, to verify the relevance of the changes in calcium homeostasis observed in cachectic skeletal muscle fibres, we determined these electrophysiological parameters by using the two intracellular microelectrodes technique.…”

“…Resting ionic conductances and muscle excitability are considered ex vivo functional outcomes in conditions of muscle calcium dysregulation. 50,51 Thus, to verify the relevance of the changes in calcium homeostasis observed in cachectic skeletal muscle fibres, we determined these electrophysiological parameters by using the two intracellular microelectrodes technique. Importantly, EDL muscle of cisplatin treated rats showed a significant 20% decrease of resting membrane conductance (gm) ( Figure 6A) and an increase of the latency of action potential (Lat) ( Figure 6B and 6C), thus indicating that the cachexia-induced alteration of calcium homeostasis influences ex vivo muscle function.…”

Androgen-mediated regulation of skeletal muscle protein balance

“…Similarly, an overnight fast led to a non-significant decrease in atrogene mRNA content within the TA of castrated mice relative to sham values, and this was accompanied by a non-significant increase in FoxO3a (Ser253) phosphorylation (Steiner et al, 2016). Lastly, supraphysiological concentrations of testosterone (100 nM) failed to alter the mRNA content of MuRF-1 and MAFbx in primary rat myotubes while nandrolone decanoate treatment failed to alter atrogene expression in the soleus of mice (Basualto-Alarcon et al, 2013, Camerino, Desaphy et al, 2015). The reason(s) for the discrepant findings between animal studies is unknown, but like many of the other processes highlighted herein, it may be due to the feeding parameters and metabolic state of the animal when muscles were isolated.…”