Analysis and Identification of In Vitro Metabolites of Exercise Mimetic SLU-PP-332 ERRα/β/γ Agonist for Doping-Control Purposes.
This study investigated the in vitro metabolic profile of SLU-PP-332, a synthetic agonist of estrogen-related receptors alpha, beta, and gamma (ERRα/β/γ), developed as an "exercise mimetic" — a compound designed to replicate some physiological benefits of physical exercise, such as increased fatty acid oxidation, oxidative muscle fiber development, and improved exercise endurance. Because the World Anti-Doping Agency (WADA) prohibits metabolic modulators in competitive sports, identifying the metabolites of SLU-PP-332 is an important step for anti-doping surveillance. The researchers incubated SLU-PP-332 with pooled human liver S9 fractions to simulate Phase I and Phase II hepatic metabolism, then analyzed the resulting products using liquid chromatography-high-resolution mass spectrometry (LC-MS/HRMS). They identified 22 metabolites in total: five monohydroxylated, three dihydroxylated, four reduced dihydroxylated, and several glucuronidated and sulfated conjugates. Eight metabolites (M1, M7, M9, M10, M13, M14, M19, and M20) were identified as the most abundant and were flagged as priority targets for doping-control testing. The authors note that full structural elucidation of all metabolites requires further investigation. No human or animal subjects were involved; all findings are limited to an in vitro cell-free system.
Why this grade: The study used only pooled human liver S9 fractions in a cell-free in vitro system, with no human participants or animal models, limiting all conclusions to metabolite identification rather than any clinical or physiological effect in living systems.
Exercise mimetics mimic physical activity and prevent development and progression of chronic metabolic diseases, including obesity and Type 2 diabetes. The World Anti-Doping Agency (WADA) prohibits the use of exercise mimetics and metabolic modulators in sports. SLU-PP-332 is a small, synthetic ERRα/β/γ agonist recently developed using a rational drug design approach. SLU-PP-332 has been shown to increase oxidative muscle fibers, fatty acid oxidation, and enhance exercise endurance. In mouse models of metabolic syndrome, it increased energy expenditure and insulin sensitivity and conferred cardiac protection against pressure overload-induced heart failure by transcriptionally activating a wide spectrum of metabolic genes involved in fatty acid metabolism and mitochondrial function. The identification of metabolites of this emerging therapeutic molecule is a critical step towards detecting its misuse. The aim of the study was identification of Phase I and II metabolites generated in vitro using pooled human liver S9 fractions. Metabolites were analyzed using liquid chromatography-high-resolution mass spectrometry (LC-MS/HRMS). Five monohydroxylated (M1-M5), three dihydroxylated (M6-M8), and four reduced dihydroxylated metabolites (M9-M12) were identified. Metabolites M13 and M19 showed direct glucuronidation and sulfation of the parent compound, respectively. Metabolites M14-M18 and M20-M22 showed glucuronidation and sulfation with hydroxylation of the naphthalene or phenolic rings, respectively. M1, M7, M9, M10, M13, M14, M19, and M20 were the most abundant of the 22 metabolites and potentially useful for doping-control purposes. Further studies are necessary to fully elucidate the structures of the metabolites.
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