Former anabolic steroid users display greater myonuclei density (i.e., nuclei in skeletal muscle cells) years after reported use suggesting a long-term enhanced anabolic capacity as compared to non-users.
Overview
What did they test? Muscle biopsies were collected from the vastus lateralis muscles of males between the ages of 18-50 years. The subjects were classified as former AAS users, current AAS users, and non-users that served as controls. The researchers measured muscle fiber cross-sectional areas, myonuclei, and satellite cell counts in the muscle biopsy samples to explore differences between participants.
What did they find? Former AAS users tended to display higher myonuclei density than controls. Former AAS users that reported greater cumulative durations of use tended to display higher myonuclei densities. Type I muscle fibers in current AAS users also displayed more satellite cells than controls.
What does it mean for you? AAS use appears to result in a measurable increase in myonuclei density where greater cumulative time of AAS use was associated with higher myonuclei densities. The specific type, dose, frequency, and time course of AAS use resulting in these effects is not entirely clear from this cross-sectional study. However, this study's findings, in addition to prior research in rodents, appears to indicate AAS use promotes a persistent increase in myonuclei density for up to at least a few years after stopping use. This phenomenon suggests former AAS users might have an enhanced ability to recover from training and grow muscle for years after stopping use compared to non-users.
What’s the Problem?
It's evident that anabolic androgenic steroid (AAS) use can promote remarkable increases in muscle size and strength. However, when steroid use is stopped, less is known about the long-term effects. Research has reported chronic users may express increased anxiety and depression upon stopping, along with prolonged hypogonadism, smaller testicular volumes, lower serum testosterone, lower follicle stimulating hormone, and lower luteinizing hormone levels 1 2. Long-term, high-dose steroid use has been associated with cognitive deficits and, in particular, visuospatial memory 3. Evidence is lacking on recovery from these deficits after stopping use which warrants further research. During AAS use, increases in blood lipids, erythrocytosis, and masculinizing effects in female users have been documented. Yet, limited research is available on persistent effects after cessation. Limited research suggests that recovery from endogenous hormone production suppression may occur within one year of stopping AAS use if the period of use lasts for less than around one year 1. Additionally, blood lipid profiles have been documented to improve within one year of stopping use 2.
Interestingly, supraphysiologic levels of AAS have been found to promote increases in satellite cell number and myonuclei content in a dose-dependent manner in human skeletal muscle 5 6. Satellite cells are considered to be muscle "stem cells" that can differentiate to increase the myonuclei content of skeletal muscle and aid in muscle growth. Greater satellite cell and myonuclear counts prior to initiating a resistance training program have been associated with a more robust muscle growth response 7. While evidence is limited in humans, research in rodent models involving supraphysiological AAS treatment has reported that increases in myonuclear content appear to be largely retained after removal of AAS treatment 8. This phenomenon suggests a "muscle memory" effect of AAS use due to the elevated myonuclear content which could serve to improve retraining capacity and potentiate subsequent muscle growth 9. In other words, a period of AAS use could increase the number of nuclei in muscle cells thereby expanding the cell's transcriptional capacity. With this enhanced transcriptional capacity and eventual expression of more RNA from gene transcription, this could theoretically translate to enhanced protein synthesis and growth. Therefore, if the increases in myonuclei content from AAS use are long-lasting, this might provide an advantage in a former AAS user for future muscle growth and adaptation to training. However, no research was available regarding this potential phenomenon in human skeletal muscle—until recently. This new study from Nielsen and colleagues is the first, to my knowledge, to formally investigate if former AAS users exhibit higher myonuclei densities than matched controls.
