Discussion
In many countries, the attention towards performance‐enhancing drug use has focused on elite athletes and the illicit competitive advantage gained from these drugs (Pope et al.,
2014). However, performance‐enhancing drugs are also used by many non‐athletes not only for enhancing performance, but also their personal appearance. Moreover, there is widespread misperception on the safety of performance‐enhancing drug use or on the manageability of the adverse effects, when in fact these adverse effects still need to be better clarified (Pope et al.,
2012). AAS is a category of performance‐enhancing drugs widely used to enhance muscular mass, which are also used for the treatment of many clinical conditions (Pope et al.,
2014).
In this study, we investigated the effects of nandrolone on the main enzymes involved in testosterone biosynthesis in Leydig cells. Testosterone is mainly produced by the Leydig cells of the testes in males and by the theca cells of the ovaries in females, although smaller amounts are synthesized by the adrenal gland in both sexes (Kostic et al.,
2011). Testosterone plays a significant role in the growth and development of the male reproductive organs and it is generally accepted that AAS exert their effects via androgen receptor (Hyyppä et al.,
1997).
The present study demonstrates that nandrolone administration interferes with the biosynthesis of testosterone in a dose‐dependent fashion. The results showed a significant increase of testosterone levels in the culture medium of R2C cells treated with 3.9 µM of nandrolone, while the levels of this hormone did not change at higher doses (15.6 µM) of nandrolone, compared to basal condition. To the best of our knowledge, the present article is the first to describe the effects of nandrolone treatment on testosterone biosynthesis in Leydig cells, and our results reinforce the data available in the current literature on the deleterious effects of nandrolone on testis.
Recently, it was demonstrated that nandrolone decaonate, at the dose of 10 mg/kg/week for 8 weeks, induced a decrease of serum testosterone levels, a reduction of testicular weight, and an alteration of sperm characteristics in rats (Ahmed,
2015). Nandrolone administration in rats determines a number of morphological changes, such as reduction of the number and the size of Leydig cells, cytoplasmic vacuolization, and lipid droplet deposition. Moreover, from a biochemical point of view, it induces testicular damage by triggering oxidative stress, inflammatory cytokines, matrix metalloproteinases, cell‐adhesion molecules, apoptotic markers, and DNA damage (Nagata et al.,
1999; Noorafshan et al.,
2005; Naraghi et al.,
2010; Ahmed,
2015; Bjelic et al.,
2015).
In our experimental model, the most important data obtained show that testosterone increases when Leydig cells are stimulated with a lower concentration of nandrolone (3.9 μM),but this increment disappears when the cells are treated with higher concentrations (15.6 μM). These changes are accompanied by modification at either protein or gene level of some of the main factors involved in testosterone production, such as StAR and CYP17A1. The latter data suggests that nandrolone is able to interfere with testosterone biosynthesis. Interestingly, we reported some discrepancies between protein and gene levels in certain conditions. These differences could be due to a number of causes (including miRNA regulations, post‐translational modifications, protein degradation etc.) that are currently under investigation. However, the presence of these discrepancies could indicate that alternative (and probably unknown) routes for testosterone biosynthesis are stimulated by nandrolone, and should be further investigated in future studies.
In conclusion, our results support the hypothesis that nandrolone is able to modify testosterone production by interfering with StAR and CYP17A1 expression in Leydig cells. Further investigations are essential to better understand in vitro the molecular mechanisms responsible of these changes. Moreover, the data presented here also needs to be confirmed in in vivo models, in order to understand the relationship between AAS administration and testis impairment in human subjects.