Elsevier

Phytomedicine

Volume 15, Issue 9, 3 September 2008, Pages 691-698
Phytomedicine

20-Hydroxyecdysone increases fiber size in a muscle-specific fashion in rat

https://doi.org/10.1016/j.phymed.2008.04.015Get rights and content

Abstract

20-Hydroxyecdysone (20E) is an ecdysteroid hormone that regulates moulting in insects. Interestingly, 20E is also found most abundantly in plant species and has anabolic effects in vertebrates, i.e. increasing muscle size without androgen influence. The effect of 20E on slow and fast fiber types of skeletal muscle has not been reported yet. Here we present that 20E affects the size (cross-sectional area, CSA) of the different fiber types in a muscle-specific manner. The effect on fiber size was modified by the distance from the site of the treatment and the presence of a regenerating soleus muscle in the animal. Besides the fiber size, 20E also increased the myonuclear number in the fibers of normal and regenerating muscles, suggesting the activation of satellite cells. According to our results 20E may provide an alternative for substitution of anabolic–androgenic steroids in therapeutic treatments against muscle atrophy.

Introduction

Ecdysteroids represent a large family of polyhydroxylated steroid invertebrate hormones that regulate moulting, metamorphosis and reproduction of arthropods (Sehnal, 1989). These substances are also synthesized by 5–6% of the plant species (phytoecdysteroids) may be as a defence against phytophagus insects (Dinan, 1995, Dinan, 2001). Generally ecdysteroids are present in a higher concentration in plants than in arthropods and are easier to extract from plants in order to investigate their pharmacological effect in mammals. The acute toxicity of ecdysteroids is very low in mice: the LD50 of 20E is >9 g/kg BW when given orally and 6.4 g/kg BW if injected intraperitoneally (Ogawa et al., 1974; Matsuda et al., 1970). Ecdysteroids have no side effects in mammals, including humans (Sláma and Lafont, 1995). Moreover, some of the ecdysteroid-containing plants are included in the human diet and used in the traditional medicine as well (Spinacia oleracea (Báthori et al., 1982) or Rhaponticum carthamoides (Syrov and Kurmukov, 1976)). Although ecdysteroids do not bind to the vertebrate steroid receptors and their mechanism of action is still unknown, many beneficial pharmacological properties are attributed to them (reviewed by Sláma and Lafont, 1995; Dinan and Lafont, 2006; Báthori et al. 2008). Increased body, organ and muscle weight and protein synthesis have been reported in case of oral or intraperitoneal administration of ecdysteroids in several animal species: Japanese quails (Sláma et al., 1996), mice (Stopka et al., 1999), rats (Syrov, 2000) and pigs (Krátky et al., 1997). There is an important difference between the effect of ecdysteroids and anabolic steroids: castration in rats sharply decreases the protein synthesis stimulating property of ecdysteroids, while steranabols (androgen steroids) still remain effective under this condition (Syrov, 2000). The non-androgenic effect was suggested because the studied phytoecdysteroids did not produce any significant changes in the weight of ventral prostate and seminal vesicles in the tested animals (normal or castrated mature or immature rats, Syrov, 2000). Phytoecdysteroids also showed an anabolic effect in female rats (Syrov, 2000).

While in the previous reports the muscle and body weight or the rate of protein synthesis have been measured, a more sophisticated study has not been carried out yet. It is not known whether 20E acts preferentially on fast or slow fiber types like the anabolic steroids (Ustunel et al., 2003). Therefore, we examined the effect of 20E on the size of muscle fiber types and the number of myonuclei reflecting the accretion of myoblasts into the fibers. We chose the soleus, a predominantly slow and the extensor digitorum longus (EDL), a predominantly fast type muscle. We also investigated the effect of 20E on the regenerating fibers of the soleus. We found that 20E changes the size and the myonuclear number of the myosin fiber types in a muscle-specific manner in the normal and regenerating soleus and the normal EDL. This effect is influenced by the applied dose, the distance from the site of 20E injection and, in case of the normal muscles, by the presence of a regenerating soleus in the other hindlimb.

Section snippets

20-Hydroxyecdysone

20E was isolated from Silene viridiflora by Tóth and Báthori (2008) in the University of Szeged, Faculty of Pharmacy, Department of Pharmacognosy, and provided for the examination in a purity of 99%. The physical and spectroscopic data of the isolated compound are in accordance with those of the literature (Lafont et al., 2002). The chemical structure of 20E is shown in Fig. 1.

Animals and treatment

Animals were treated according to the regulations of the Ethical Committee of the University of Szeged.

Twenty male

Body and muscle mass

The body and muscle mass increased significantly in group N20E compared to group C. However these two parameters did not change in group R20E-1 and only the muscle mass of the right EDL increased in group R20E-2 compared to group RC (Table 1).

CSA of MyHC fiber types

The size of muscle fibers increased significantly in response to the 20E treatment in the left soleus of group N20E (5011±67.44 μm2) compared to group C (4261±49.68 μm2). The rat soleus muscle consists of slow-oxidative type I (90%) and fast-oxidative type

Discussion

Our study demonstrated that 20E affects the size of fiber types in a different manner in the soleus than in the EDL muscles. This suggests that this compound affects fiber type size in a muscle-specific fashion. A muscle-specific effect on fiber size has also been reported in case of anabolic–androgenic steroids (AAS). Treatment with a low (1.5 mg/kg BW/week) and a high (7.5 mg/kg BW/week) therapeutic dose of nandrolone decanoate over a 5 weeks period increased the dimension of type IIx and IIB

Acknowledgements

This work was partially supported by the ETT 168/2003 grant from the Hungarian Ministry of Health. Thanks to professor Mária Báthori for the 20-hydroxyecdysone. Thanks to Dr. Árpád Márki for technical assistance in the initial phase of this study.

References (31)

  • A. Eriksson et al.

    Skeletal muscle morphology in power-lifters with and without anabolic steroids

    Histochem. Cell. Biol.

    (2005)
  • M. Estrada et al.

    Testosterone stimulates intracellular calcium release and mitogen-activated protein kinases via a G protein-coupled receptor in skeletal muscle cells

    Endocrinology

    (2003)
  • A. Ferry et al.

    Effects of anabolic/androgen steroids on regenerating skeletal muscles in the rat

    Acta Physiol. Scand.

    (1999)
  • A. Holmang et al.

    Effect of testosterone on muscle insulin sensitivity and morphology in female rats

    Am. J. Physiol.

    (1990)
  • F. Kadi et al.

    Effects of anabolic steroids on the muscle cells of strength-trained athletes

    Med. Sci. Sports Exercise

    (1999)
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