title: Selenoprotein P in seminal fluid is a novel biomarker of sperm quality.
abstract: Hepatically-derived selenoprotein P (SePP) transports selenium (Se) via blood to other tissues including the testes. Male Sepp-knockout mice are infertile. SePP-mediated Se transport to Sertoli cells is needed for supporting biosynthesis of the selenoenzyme glutathione peroxidase-4 (GPX4) in spermatozoa. GPX4 becomes a structural component of sperm midpiece during sperm maturation, and its expression correlates to semen quality. We tested whether SePP is also present in seminal plasma, potentially correlating to fertility parameters. Semen quality was assessed by sperm density, morphology and motility. SePP was measured by an immunoluminometric assay, and trace elements were determined by X-ray fluorescence spectroscopy. SePP levels were considerably lower in seminal plasma as compared to serum (0.4±0.1 mg/l vs. 3.5±1.0 mg/l); Se concentrations showed a similar but less pronounced difference (48.9±20.7 μg/l vs. 106.7±17.3 μg/l). Se and Zn correlated positively in seminal fluid but not in serum. Seminal plasma SePP concentrations were independent of serum SePP concentrations, but correlated positively to sperm density and fraction of vital sperm. SePP concentrations in seminal plasma of vasectomized men were similar to controls indicating that accessory sex glands are a testes-independent source of SePP. This notion was corroborated by histochemical analyses localizing SePP in epithelial cells of seminal vesicles. We conclude that SePP is not only involved in Se transport to testes supporting GPX4 biosynthesis but it also becomes secreted into seminal plasma, likely important to protect sperm during storage, genital tract passage and final journey.
authors.affiliation: Institut für Experimentelle Endokrinologie, Charité - Universitätsmedizin Berlin, CVK, Südring 10, D-13353 Berlin, Germany; Institut für Fortpflanzungsbiologie, Leibniz-Institut für Nutztierbiologie, D-18196 Dummerstorf, Germany.
authors.forename: Marten
authors.initials: M
authors.lastname: Michaelis
authors.affiliation: Gemeinschaftspraxis für Urologie und Andrologie, Kaiser-Wilhelm-Ring 36, D-50672 Köln, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Gralla
authors.affiliation: Institut für Experimentelle Endokrinologie, Charité - Universitätsmedizin Berlin, CVK, Südring 10, D-13353 Berlin, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Behrends
authors.affiliation: Institut für Pathologie und Neuropathologie, Universitätsklinikum, D-72076 Tübingen, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Scharpf
authors.affiliation: Institut für Experimentelle Endokrinologie, Charité - Universitätsmedizin Berlin, CVK, Südring 10, D-13353 Berlin, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Endermann
authors.affiliation: Institut für Experimentelle Endokrinologie, Charité - Universitätsmedizin Berlin, CVK, Südring 10, D-13353 Berlin, Germany.
authors.forename: Eddy
authors.initials: E
authors.lastname: Rijntjes
authors.affiliation: Institut für Experimentelle Endokrinologie, Charité - Universitätsmedizin Berlin, CVK, Südring 10, D-13353 Berlin, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Pietschmann
authors.affiliation: Institut für Experimentelle Endokrinologie, Charité - Universitätsmedizin Berlin, CVK, Südring 10, D-13353 Berlin, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Hollenbach
authors.affiliation: Institut für Experimentelle Endokrinologie, Charité - Universitätsmedizin Berlin, CVK, Südring 10, D-13353 Berlin, Germany. Electronic address: lutz.schomburg@charite.de.
authors.forename: Lutz
authors.initials: L
authors.lastname: Schomburg
mesh_terms: D000328:Adult; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D005298:Fertility; D006801:Humans; D008297:Male; D051379:Mice; D012643:Selenium / Q000097:blood; D051149:Selenoprotein P / Q000097:blood / Q000378:metabolism*; D012661:Semen / Q000378:metabolism*; D012669:Seminal Vesicles / Q000166:cytology / Q000378:metabolism; D013094:Spermatozoa / Q000378:metabolism*; D015032:Zinc / Q000097:blood
chemical_list: D015415:Biomarkers; D051149:Selenoprotein P; D012643:Selenium; D015032:Zinc
keywords: GPX; Megalin; Micronutrient; Se; SePP; Seminal vesicle; Sperm; Trace element; glutathione peroxidase; selenium; selenoprotein P