Steroidogenesis in the skeletal muscle

性类固醇激素，如睾酮和雌二醇，在发展骨骼肌的力量和质量方面起着重要作用。循环脱氢表雄酮（DHEA）被外周吸收并通过3b -羟基类固醇脱氢酶（HSD）和17B-HSD转化为睾酮，而睾酮又通过芳香化酶细胞色素P450 （P450arom）不可逆地转化为雌激素。尽管性类固醇激素与骨骼肌的调节和适应有关，但目前尚不清楚骨骼肌是否具有能够代谢循环脱氢表雄酮的局部类固醇酶机制。首先，我们研究了骨骼肌中是否存在三种关键的类固醇生成酶，并能够产生性类固醇激素。这些发现新颖而重要，因为它们首次提供了证据，表明骨骼肌能够从循环中的脱氢表雄酮或睾丸激素中局部合成性类固醇激素。第二项研究，我们检查了休息和运动后骨骼肌中睾酮、雌二醇和类固醇生成相关酶（如3B-HSD、17B-HSD和P450arom）水平的性别差异。我们研究了休息大鼠（10周龄）和运动大鼠（10周龄，跑步机，30 m/min, 30 min）的腓肠肌。一次运动就能影响骨骼肌中的类固醇生成系统，而这些改变在性别之间是不同的。急性运动诱导的类固醇生成酶的改变可能增强两性骨骼肌局部类固醇生成。

Sex steroid hormones, such as testosterone and estradiol, play important roles in developing both strength and mass of skeletal muscle. Circulating dehydroepiandrosterone (DHEA)is peripherally taken up and converted to testosterone by 3B-hydroxysteroid dehydrogenase (HSD) and 17B-HSD, and testosterone, in turn, is irreversibly converted to estrogens by aromatase cytochrome P450 (P450arom). Although sex steroid hormones have been implicated in skeletal muscle regulation and adaptation, it is unclear whether skeletal muscles have a local steroidogenic enzymatic machinery capable of metabolizing circulating DHEA. First study, we investigate whether the three key steroidogenic enzymes are present in the skeletal muscle, and are capable of generating sex steroid hormones. These findings are novel and important in that they provide the first evidence showing that skeletal muscles are capable of locally synthesizing sex steroid hormones from circulating DHEA or testosterone. Second study, we examine sex differences in the levels of testosterone, estradiol, and steroidogenesis-related enzymes, such as 3B-HSD, 17B-HSD and P450arom, in the skeletal muscle at rest and after exercise. We studied the gastrocnemius muscles of resting rats(10 weeks old)and exercised rats(10 weeks old, treadmill running, 30 m/min, 30 min). A single bout of exercise can influence the steroidogenic system in skeletal muscle and these alterations differ between sexes. The acute exercise-induced alteration of steroidogenic enzymes may enhance the local steroidogenesis in the skeletal muscle in both sexes.