Karina Fontana

Adverse effect of the anabolic-androgenic steroid mesterolone on cardiac remodelling and lipoprotein profile is attenuated by aerobicz exercise training.

Abuse of anabolic–androgenic steroids (AAS) for improving physical performance is associated with serious, sometimes fatal, adverse effects. The aim of the present work was to investigate the effects of AAS on the cardiac structure and the plasma lipoprotein profile isolated and in combination with exercise. Transgenic mice with a human lipaemic phenotype (expressing cholesteryl ester transfer protein on the LDL receptor knockout background) were used in this study. Sedentary and exercised mice (treadmill running, five times per week for 6 weeks) were treated with mesterolone (2 μg/g body weight) or vehicle (control‐C) in the last 3 weeks. Four groups were compared: (i) exercise + mesterolone (Ex‐M), (ii) exercise + vehicle (Ex‐C), (iii) sedentary + mesterolone (Sed‐M) and (iv) sedentary + vehicle (Sed‐C). Arterial blood pressure and body mass increased in all groups along time, but Sed‐M reached the highest values and Ex‐C the lowest. Treatment with mesterolone increased total cholesterol, triglyceride, low‐density lipoprotein cholesterol (LDL‐c) and very LDL‐c (VLDL‐c) plasma levels. However, exercise blunted some of these deleterious effects by increasing high‐density lipoprotein cholesterol and decreasing LDL‐c, VLDL‐c and triglycerides. Exercise training induced beneficial effects, such as physiological cardiomyocyte hypertrophy, increase in myocardial circulation and decrease in cardiac interstitium. However, mesterolone impaired such physiological gains and in addition increased troponin T plasma levels both in sedentary and exercised mice. Thus, while mesterolone induced pro‐atherogenic lipoprotein profile and pathogenic cardiac hypertrophy, exercise counteracted these effects and modified favourably both the lipoprotein profile and the cardiac remodelling induced by mesterolone.

Inflammation and apoptosis induced by mastoparan Polybia-MPII on skeletal muscle

Mastoparan firstly described as an inducer of mast cell granules exocytosis has been also related to many essential mechanisms of cell function. In skeletal muscle tissue the best characterization of mastoparan effect was induction of myonecrosis. We examined the ability of mastoparan Polybia-MPII from Polybia paulista wasp venom to induce apoptosis and inflammation in mouse tibial anterior muscle. The activation of caspase 3 and 9, the expression of TNF-alpha, IFN-gamma, CD68 and CD163 proteins, specific of resident and migrant macrophages, respectively, were examined (3h to 21d). TUNEL-positive nuclei were found both in damaged and normal-looking muscle fibres, whereas the caspases, cytokines and macrophages proteins were only in damaged fibres. The caspase 3 and 9 expression and the immunolabelled areas of TNF-alpha and IFN-gamma were significantly higher compared to control. TUNEL-positive nuclei and TNF-alpha expression were also present in regenerating fibres. CD68 and CD163 signalize necrotic debris removal, release of chemo-attractants and cytokines which have been considered a pre-requisite for muscle regeneration. High levels of cytokines coincided with the intense muscle proteolysis by mastoparan (3-24h) and the climax of regeneration (3 d) whereas cytokines decline corresponded to periods of tissue remodeling and intense fibre protein synthesis (7-21 d). We conclude that the mastoparan Polybia-MPII causes myonecrosis and apoptosis, the latter probably involving caspases signalling, corroborated by mitochondrial damage, and cytokines activation.

Morphological changes in murine skeletal muscle in response to exercise and mesterolone

Light and electron microscopy and quantitative morphometry were used to determine the effects of exercise and mesterolone on the soleus muscles of mice. Both exercise and mesterolone caused a significant hypertrophy of extrafusal muscle fibres. The hypertrophy of Type I fibres was greater than that of Type II fibres. There was no hyperplasia. Mitochondria were more numerous and larger than in the muscles of sedentary animals. Capillarity increased and small centrally nucleated muscle fibres appeared, usually in small clusters and most often in the muscles of animals exposed to mesterolone. A small proportion of satellite cells exhibited signs of activation but there were more in the muscles of mesterolone-treated animals than after exercise. Muscles from animals that had been both exercised and treated with mesterolone exhibited the largest changes: muscle mass and muscle fibre hypertrophy was greater than in all other groups of animals, capillarity was higher and >30% of all recognized satellite cells exhibited signs of activation. Groups of small centrally nucleated muscle fibres were commonly seen in these muscles. They appeared to be the result of splits in the form of sprouts from existing muscle fibres. With both exercise and mesterolone, alone or in combination, there was an increase in the proportion of Type I muscle fibres and a decrease in the proportion of Type II.

Effects of anabolic steroids and high-intensity aerobic exercise on skeletal muscle of transgenic mice.

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.