Abstract
In an attempt to shorten recovery time and improve performance, strength and endurance athletes occasionally turn to the illicit use of anabolic-androgenic steroids (AAS). This study evaluated the effects of AAS treatment on the muscle mass and phenotypic characteristics of transgenic mice subjected to a high-intensity, aerobic training program (5d/wk for 6 weeks). The transgenic mice (CETP+/-LDLr-/+) were engineered to exhibit a lipid profile closer to humans. Animals were divided into groups of sedentary (Sed) and/or training (Ex) mice (each treated orally with AAS or gum arabic/vehicle: Sed-C, Sed-M, ex-C, ex-M). The effects of AAS (mesterolone: M) on specific phenotypic adaptations (muscle wet weight, cross-sectional area, and fiber type composition) in three hindlimb muscles (soleus:SOL, tibialis anterior:TA and gastrocnemius:GAS) were assessed. In order to detect subtle changes in fiber type profile, the entire range of fiber types (I, IC, IIAC, IIA, IIAD, IID, IIDB, IIB) was delineated using mATPase histochemistry. Body weight gain occurred throughout the study for all groups. However, the body weight gain was significantly minimized with exercise. This effect was blunted with mesterolone treatment. Both AAS treatment (Sed-M) and high-intensity, aerobic training (ex-C) increased the wet weights of all three muscles and induced differential hypertrophy of pure and hybrid fibers. Combination of AAS and training (ex-M) resulted in enhanced hypertrophy. In the SOL, mesterolone treatment (Sed-M and ex-M) caused dramatic increases in the percentages of fiber types IC, IIAC, IIAD, IID, with concomitant decrease in IIA, but had minimal impact on fiber type percentages in the predominantly fast muscles. Overall, the AAS-induced differential adaptive changes amounted to significant fiber type transformations in the fast-to-slow direction in SOL. AAS treatment had a significant effect on muscle weights and fiber type composition in SOL, TA and GAS which was even maximized in animals subjected to metabolically high-intensity aerobic exercise.
Highlights
Anabolic-androgenic steroids (AAS) are synthetic derivatives of testosterone which have been chemically modified to maximize anabolic effects and minimize undesirable androgenic effects [1]
There was a tendency for body weight (BW) to gradually increase throughout the trial period for all groups (Table 2)
Two-way analysis of variance (ANOVA) showed that there was no interaction between mesterolone and exercise for BW values
Summary
Anabolic-androgenic steroids (AAS) are synthetic derivatives of testosterone which have been chemically modified to maximize anabolic effects and minimize undesirable androgenic effects [1]. Banned from sports, the illicit use of AAS by professional and recreational athletes continues despite a long list of serious side effects [3] These athletes are interested in decreasing body fat while increasing muscle mass and strength in an effort to enhance physical performance [4]. The large diversity of myosin heavy chain (MHC) isoforms expressed in muscle helps to form the basis for this remarkable plasticity. It is the expression and co-expression of these various MHC isoforms within a given fiber that delineates the entire range of fiber types [6,7,8]. The prevalence of certain types of these fibers accounts for the functional and structural characteristics of a given muscle, and its phenotype
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