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The use of growth hormone-releasing hormones (GHRHs) is prohibited in sports according to the regulations of the World Anti-Doping Agency (WADA). The aim of the present study was to develop a method for the simultaneous detection of four different GHRHs and respective metabolites from human plasma by means of immunoaffinity purification and subsequent nano-ultrahigh performance liquid chromatography-high resolution/high accuracy (tandem) mass spectrometry. The target analytes included Geref (Sermorelin), CJC-1293, CJC-1295, and Egrifta (Tesamorelin) as well as two metabolites of Geref and CJC-1293, which were captured from plasma samples using a polyclonal GHRH antibody in concert with protein A/G monolithic MSIA™ D.A.R.T.’S® (Disposable Automation Research Tips) prior to separation and detection. The method was fully validated and found to be fit for purpose considering the parameters specificity, linearity, recovery (19–37 %), lower limit of detection (<50 pg/mL), imprecision (<20 %), and ion suppression/enhancement effects. The analytes’ stability and metabolism were elucidated using in vitro and in vivo approaches. EDTA blood samples were collected from rats 2, 4, and 8 h after intravenous administration of GHRH (one compound per test animal). All intact substances were detected for at least 4 h but no anticipated metabolite was confirmed in laboratory rodents’ samples; conversely, a Geref metabolite (GHRH3-29) was found in a human plasma sample collected after subcutaneous injection of the drug to a healthy male volunteer. The obtained results demonstrate that GHRHs are successfully detected in plasma using an immunoaffinity-mass spectrometry-based method, which can be applied to sports drug testing samples. Further studies are however required and warranted to account for potential species-related differences in metabolism and elimination of the target analytesGraphical abstractGHRH immunoaffinity purification by means of anti-GHRH antibody coated protein A/G D.A.R.T.’S

ObjectiveTo examine acute (single-bout) and training effects of high-intensity interval training (HIIT) vs standard exercise therapy (moderate continuous training [MCT]) on plasma neurofilament light chain (pNfL) and kynurenine (KYN) pathway of tryptophan degradation metabolites in persons with multiple sclerosis (pwMS).MethodsSixty-nine pwMS (Expanded Disability Status Scale score 3.0–6.0) were randomly assigned to a HIIT or an MCT group. Changes in pNfL and KYN pathway metabolites measured in blood plasma were assessed before, after, and 3 hours after the first training session as well as after the 3-week training intervention.ResultsAcute exercise reduced pNfL and increased the KYN pathway flux toward the neuroprotective kynurenic acid (KA). Changes in pNfL correlated positively with changes in KA and negatively with the quinolinic acid-to-KA ratio. HIIT consistently led to greater effects than MCT. Following the 3-week training intervention, the KYN pathway was activated in HIIT compared with MCT.ConclusionFuture studies and clinical assessments of pNfL should consider acute exercise as confounding factor for measurement reliability. Moreover, exercise-induced KYN pathway rerouting might mediate neuroprotection, potentially underlying the benefits in rehabilitation for pwMS.Classification of EvidenceThis study provides Class II evidence that acute HIIT diminishes pNfL and increases KA levels, and 3 weeks of HIIT activate the KYN pathway in pwMS.Trial Registration InformationClinical trial registration number: NCT03652519.