Effect of endurance training on oestrogen receptor alpha expression in different rat skeletal muscle type

Abstract

It is well known that oestrogens exert muscle anabolic and metabolic effects. Oestrogens act via specific oestrogen receptor (ER) proteins. The mainly represented oestrogen receptor alpha messenger ribonucleic acid subtype (ER(alpha) mRNA) was described in various tissues including the skeletal muscle. Moreover, it has been shown that endurance training significantly increases ER(alpha) mRNA levels in the female rat gastrocnemius muscle. The aim of this study was to determine if this training programme also modifies ER(alpha) mRNA levels in muscles with different typology, the soleus (slow twitch muscle), extensor digitorum longus (fast twitch muscle) and gastrocnemius (intermediate muscle). So far, two groups of Wistar female rats were set up: untrained (u) (n = 7), and trained (e) (n = 7). The endurance training programme was performed for 7 weeks, 5 days per week and consisted of 1 h of continuous running on an adapted motor-driven treadmill involving progressive intensity and gradient of the treadmill. Three different skeletal muscles, extensor digitorum longus (E), gastrocnemius (G) and soleus (S), were isolated and weighed in the untrained (Eu, Gu and Su) and trained group (Ee, Ge and Se). Semi-quantification of ER(alpha) mRNA levels was performed by the reverse transcriptase-polymerase chain reaction (RT-PCR) technique. In order to attest the efficiency of our endurance training programme, the citrate synthase activity (CS) of each muscle was measured by a fluorimetric method. The CS activity was significantly increased with training in the gastrocnemius [100.00 +/- 4.99% in Gu (n = 6) vs. 138.10 +/- 8.82% in Ge (n = 6), P < 0.01] and in the soleus [100.00 +/- 2.92% in Su (n = 7) vs. 115.90 +/- 3.71% in Se (n = 7), P < 0.01] but not in the extensor digitorum longus [100.00 +/- 1.87% in Eu (n = 7) vs. 96.90 +/- 1.55% in Ee (n = 7)]. Concerning the influence of muscle type on ER(alpha) mRNA level (1) in the untrained group, the ER(alpha) mRNA level was significantly higher in soleus muscle compared with gastrocnemius and extensor digitorum longus muscles [0.43 +/- 0.04 in Su (n = 7) compared with 0.31 +/- 0.03 in Gu (n = 6) and 0.21 +/- 0.03 in Eu (n = 7), P < 0.05; P < 0.05); 2] in the trained group, the ER(alpha) mRNA level was significantly higher insoleus and gastrocnemius muscles compared with extensor digitorum longus muscle [0.43 +/- 0.06 in Se (n = 7) and 0.49 +/- 0.05 in Ge (n = 6) vs. 0.12 +/- 0.01 in Ee (n = 7), P < 0.05; P < 0.05]. Indeed, after training, the ER(alpha) mRNA level significantly increased in gastrocnemius muscle [0.31 +/- 0.03 in Gu(n = 6) vs. 0.49 +/- 0.05 in Ge (n = 6), P < 0.01], significantly decreased in extensor digitorum longus [0.21 +/- 0.03 in Eu (n = 7) vs. 0.12 +/- 0.01 in Ee (n = 7), P < 0.01] and was not significantly modified in soleus [0.43 +/- 0.04 in Su (n = 7) vs. 0.43 +/- 0.06 in Se (n = 7)]. The differences in ER(alpha) mRNA level between trained and untrained animals indicate training-induced effects that are specific to the skeletal muscle type.

A rehabilitation exercise program to remediate skeletal muscle atrophy in an estrogen-deficient organism may be ineffective

“…One issue that may affect recovery and rehabilitation exercise effects on skeletal muscle is fiber type. Type I or slow fibers have been reported to have more estrogen receptors (which are E2 activated), which may indicate slow muscles are more E2 receptive (Ciocca and Vargas Roig 1995;Cooke et al 2003;Dahlberg 1982;Kalbe et al 2007;Knutsson et al 2002;Lemoine et al 2002Lemoine et al , 2003Wiik et al 2008). In addition, type I fibers have thicker z lines which suggests slow muscles are protected from damage compared to type II fiber dominated muscles (Clarkson and Hubal 2002).…”

Testosterone deficiency impairs glucose oxidation through defective insulin and its receptor gene expression in target tissues of adult male rats

“…Insulin target tissues have receptor for androgen (Lemoine et al, 2002;Mayes and Watson, 2004). The fact that testosterone replacement was able to increase insulin receptor number and its mRNA level suggests that testosterone may have a direct effect on insulin receptor gene transcription as well as translation of mRNA.…”

“…Testosterone, an anabolic steroid, plays an important role in this direction (Lemoine et al, 2002;Livingstone and Collison, 2002;Boyanov et al, 2003;Tsai et al, 2004;Mayes and Watson, 2004;Inaba et al, 2005;Lee et al, 2005). Therefore, metabolic activities of tissues are likely to change with experimental or pathological manipulation of hormones (Mainwaring and Mangan, 1973).…”

Effects of treadmill exercise training on liver fat accumulation and estrogen receptor alpha expression in intact and ovariectomized rats with or without estrogen replacement treatment

“…Endurance training has been reported to regulate ERalpha expression in several tissues such as liver, heart and skeletal muscle (Paquette et al 2007a;Lemoine et al 2002). Paquette et al (2007a) has put forward the conclusion that endurance training has different effects on ER transcripts levels in the liver according to the presence or the absence of ovaries.…”