Endocrine Abstracts

Background and Objective: Information on the long-term effects of anabolic androgenic steroids (AAS) use on the myocellular properties of human skeletal muscle is scarce, despite being the primary target of AAS. Animal studies suggest persistence of upregulated myonuclei numbers following AAS discontinuation. Few human studies have investigated the effects of AAS on human skeletal muscle cell morphology and exclusively focused on current AAS users. No data exist elucidating the long-term effect on human skeletal myofiber properties in previous AAS users. The objective of this study was to investigate the effects of AAS use on myofiber morphology and myonuclei content in current and former AAS users.

Methods: Community-based cross-sectional study including men involved in recreational strength training. Biopsies were obtained from the quadriceps muscle (vastus lateralis). Immunofluorescence analysis was performed to quantify myofiber size (CSA) and myonuclei numbers. AAS usage was evaluated using standardized questionnaires.

Results: We included a total of 25 participants: 8 current and 7 previous AAS users and 10 controls with no prior AAS use. Mean (SD) age was 31 (7) years and did not differ between groups. Median (25^th-75^th percentiles) accumulated duration of AAS intake was 174 (101 – 206) and 140 (24 – 260) weeks in current and former AAS users, respectively (P=0.482). Mean (95% CI) elapsed duration since AAS cessation was 4.0 (1.2; 12.7) years among former AAS users. Type II muscle fibers in former AAS users displayed smaller myonuclear domains than controls (P=0.013), corresponding to a higher myonuclei-cytoplasma ratio. Further, the ratio of perimeter per myonuclei in type II fibers tended to be lower in former users than controls (P=0.060). Type I fibers in current AAS users exhibited increased amounts of satellite cells per myofiber (P=0.031) and more myonuclei per myofiber (P=0.043) compared with controls.

Conclusions: AAS use is associated with increases in satellite cell and myonuclei content. Elevated myonuclei content was observed in type II fibers obtained from previous AAS users with a mean of 4 years after AAS cessation. Thus, AAS usage may lead to superior re-training ability (‘muscle memory’) years after AAS cessation. The findings enhance our understanding of the long-term effects of supraphysiological AAS intake on human skeletal muscle mass.