Selective Androgen Receptor Modulators (SARMs) are not FDA approved, and obtaining SARMs for personal use is illegal. Nevertheless, SARM use is increasingly popular amongst recreational athletes. Recent case reports of drug-induced liver injury (DILI) and tendon rupture raise serious concerns for the safety of recreational SARM users. On 10 November 2022 PubMed, Scopus, Web of Science, and ClinicalTrials.gov were searched for studies that reported safety data of SARMs. A multi-tiered screening approach was utilized, and any study or case report of generally healthy individuals exposed to any SARM was included. Thirty-three studies were included in the review with 15 case reports or case series and 18 clinical trials (total patients N = 2136 patients, exposed to SARM N = 1447). There were case reports of drug-induced liver injury (DILI) (N = 15), Achilles tendon rupture (N = 1), rhabdomyolysis (N = 1), and mild reversible liver enzyme elevation (N = 1). Elevated alanine aminotransferase (ALT) was commonly reported in clinical trials in patients exposed to SARM (mean 7.1% across trials). Two individuals exposed to GSK2881078 in a clinical trial were reported to have rhabdomyolysis. Recreational SARM use should be strongly discouraged, and the risks of DILI, rhabdomyolysis, and tendon rupture should be emphasized. However, despite warnings, if a patient refuses to discontinue SARM use, ALT monitoring or dose reduction may improve early detection and prevention of DILI.
It has been known that both estrogen (E2) and nitric oxide (NO) are critical for proper cardiovascular system (CVS) function. It has also been demonstrated that E2 acts as an upstream effector in the nitric oxide (NO) pathway. Results from this study indicate that the use of a nitric oxide synthase (NOS) inhibitor (NOSI) which targets specifically neuronal NOS (nNOS or NOS1), proadifen hydrochloride, caused a significant depression of fish heart rates (HR) accompanied by increased arrhythmic behavior. However, none of these phenotypes were evident with either the inhibition of endothelial NOS (eNOS) or inducible NOS (iNOS) isoforms. These cardiac arrhythmias could also be mimicked by inhibition of E2 synthesis with the aromatase inhibitor (AI), 4-OH-A, in a manner similar to that of nNOSI. In both scenarios, by using an NO donor (DETA-NO) in either NO + nNOSI or E2 + AI co-treatments, fish could be significantly rescued from decreased HR and increased arrhythmias. However, the addition of an NOS inhibitor (L-NAME) to the E2 + AI co-treatment fish prevented the rescue of low heart rates and arrhythmias, which strongly implicates the NO pathway as a downstream E2 targeted molecule for the maintenance of healthy cardiomyocyte contractile conditions in the developing zebrafish. Cardiac arrhythmias could be mimicked by the S-nitrosylation pathway inhibitor DTT (1,4-dithiothreitol) but not by ODQ (1H-[1–3]oxadiazolo[4,3-a]quinoxalin-1-one), the inhibitor of the NO receptor molecule sGC in the cGMP-dependent pathway. In both the nNOSI and AI-induced arrhythmic conditions, 100% of the fish expressed the phenotype, but could be rapidly rescued with maximum survival by a washout with dantrolene, a ryanodine Ca2+ channel receptor blocker, compared to the time it took for rescue using a control salt solution. In addition, of the three NOS isoforms, eNOS was the one most implicated in the maintenance of an intact developing fish vascular system. In conclusion, results from this study have shown that nNOS is the prominent isoform that is responsible, in part, for maintaining normal heart rates and prevention of arrhythmias in the developing zebrafish heart failure model. These phenomena are related to the upstream stimulatory regulation by E2. On the other hand, eNOS has a minimal effect and iNOS has little to no influence on this phenomenon. Data also suggests that nNOS acts on the zebrafish cardiomyocytes through the S-nitrosylation pathway to influence the SR ryanidine Ca2+ channels in the excitation-coupling phenomena. In contrast, eNOS is the prominent isoform that influences blood vessel development in this model.
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