Abstract
The chemokine chemerin is a novel adipokine involved in the regulation of energy metabolism but also female reproductive functions in mammals. Its effects on male fertility are less studied. Here, we investigated the involvement of chemerin in chicken male reproduction. Indeed, the improvement of the sperm of roosters is a challenge for the breeders since the sperm quantity and quality have largely decreased for several years. By using specific chicken antibodies, here we show that chemerin and its main receptor CMKLR1 (chemokine-like receptor 1) are expressed within the chicken testis with the lowest expression in adults as compared to the embryo or postnatal stages. Chemerin and CMKLR1 are present in all testicular cells, including Leydig, Sertoli, and germinal cells. Using in vitro testis explants, we observed that recombinant chicken chemerin through CMKLR1 inhibits hCG (human chorionic gonadotropin) stimulated testosterone production and this was associated to lower 3βHSD (3beta-hydroxysteroid dehydrogenase) and StAR (steroidogenic acute regulatory protein) expression and MAPK ERK2 (Mitogen-Activated Protein Kinase Extracellular signal-regulated kinase 2) phosphorylation. Furthermore, we demonstrate that chemerin in seminal plasma is lower than in blood plasma, but it is negatively correlated with the percentage of motility and the spermatozoa concentration in vivo in roosters. In vitro, we show that recombinant chicken chemerin reduces sperm mass and individual motility in roosters, and this effect is abolished when sperm is pre-incubated with an anti-CMKLR1 antibody. Moreover, we demonstrate that fresh chicken sperm treated with chemerin and used for artificial insemination (AI) in hen presented a lower efficiency in terms of eggs fertility for the four first days after AI. Taken together, seminal chemerin levels are negatively associated with the rooster fertility, and chemerin produced locally by the testis or male tract could negatively affect in vivo sperm quality and testosterone production through CMKLR1.
Highlights
Some evidence indicates that dysregulation of the expression and/or secretion of hormones, mainly produced by adipose tissue called adipokines, is involved in the regulation of fertility [1,2,3].Among adipokines, the newly characterized chemokine chemerin is suggested to influence the male reproductive tract [2,4]
In the we showed that chicken chemerin inhibits not basal, hCG-stimulated agreement with those observed in rats testosterone production by testis explants, and this was associated with a reduction in 3β-hydroxysteroid dehydrogenase 1 (3βHSD) and steroidogenic acute regulatory (STAR)
The summary diagram shows the effects of chicken chemerin on the chicken testis and male fertility reported in this paper (Figure 10)
Summary
Some evidence indicates that dysregulation of the expression and/or secretion of hormones, mainly produced by adipose tissue called adipokines, is involved in the regulation of fertility [1,2,3].Among adipokines, the newly characterized chemokine chemerin is suggested to influence the male reproductive tract [2,4]. (TIG-2) or retinoic acid receptor responder 2 (RARRES2) that was identified by [5] It is secreted as an inactive precursor, pro-chemerin (18 kDa), and it is activated through post-translational carboxyl-terminal processing by a variety of proteinases [6]. Chemerin exerts its main biological functions through binding to its G protein-coupled receptor chemokine-like receptor 1 (CMKLR1), in humans termed as chemerin receptor 23 (ChemR23) [7,8]. Besides their expression in adipose tissue, chemerin and CMKLR1 are expressed in various other tissues and cell populations [7]. A sex dimorphic pattern of chemerin expression, with higher levels in males compared to females, has been reported [9]
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