Leptin and leptin receptor in pig spermatozoa: evidence of their involvement in sperm capacitation and survival

Abstract

Several studies have recently investigated the role of leptin, the adipocyte-secreted hormone, in the growth and reproduction of rodents, humans, and domestic animals. The present study was designed to explore the expression of leptin and its receptor in pig spermatozoa. Successful Western blot evidenced a 16 kDa band for leptin and six isoforms, ranging from 120 to 40 kDa, for the leptin receptor. Both leptin and leptin receptor were interestingly located at sperm acrosomal level, suggesting their involvement in the oocyte fertilization events. In fact, both capacitation indexes and acrosin activity were enhanced by leptin, and these effects were reduced by the anti-leptin receptor antibody. Afterwards, we investigated the main transduction pathways regulated by the hormone. Our results showed that, in pig sperm, leptin can trigger the signal transducer and activator of transcription 3, a classical component of cytokine signal transduction pathways, whose expression has not been previously reported in male gamete; in addition it was found constitutively activated. Besides, leptin was able to induce the activation of phosphatidylinositol phosphate kinase 3 and MAP kinase pathways as well as of BCL2, a known antiapoptotic protein. These data address to a role of leptin and its receptor on pig sperm survival. The presence of leptin and its receptor in pig sperm suggests that they, through an autocrine short loop, may induce signal transduction and molecular changes associated with sperm capacitation and survival. Reproduction (2008) 136 23-32

Leptin and Its Receptor Are Expressed in the Testis and in the Epididymis of Young and Adult Pigs

“…In fact, Lep is detected by the central nervous system and, by means of the neuroendocrine axis, regulates hypothalamic gonadotropin-releasing hormone (GnRH) release and subsequent luteinizing hormone (LH) secretion (Barb et al, 2005). However, our recent work demonstrated a role of leptin in pig sperm acquisition of fertilizing ability (Aquila et al, 2008) suggesting a possible peripheral effect of the hormone in porcine male reproduction. This study has identified leptin and its receptor in testis and epididymis of young and adult pigs demonstrating the presence of the two proteins at different levels: mRNA expression, protein expression, and immunolocalization.…”

“…However, our recent work detected leptin and Ob-R in pig sperm showing a role of the hormone on the male gamete biology (Aquila et al, 2008). Therefore, aim of this work was to provide some evidence of leptin involvement in the control of male reproductive structures by investigating Lep and Ob-R in testicular and epididymal cells of immature and mature pigs.…”

“…In fact, Lep and/or Ob-R were detected in rodent testes (Caprio et al, 2003;El-Hefnawy et al, 2000;Herrid et al, 2008), in human testes and seminal plasma (Glander et al, 2002;Soyupek et al, 2005;Ishikawa et al, 2007), in human sperm (Aquila et al, 2005), in boar sperm (De Ambrogi et al, 2007), and in pig sperm (Aquila et al, 2008). Furthermore, a recent paper reported the effects of leptin treatment, alone or in combination with dietary energy restriction, on different reproductive parameters of male rats (Sirotkin et al, 2008).…”

Leptin Receptor in Ram Epididymal Spermatozoa

“…However, to our knowledge, this is the first time that the presence of mRNA of Ob-R and Ob-Rb in ram epididymal spermatozoa has been demonstrated. A recent study in pig has suggested that leptin receptor may induce transduction and molecular changes associated with sperm capacitation and survival [18]. These findings suggest that leptin, through leptin receptor, may play an important role in both sperm function and male fertility.…”

Leptin and insulin in the seminal plasma of zebu bulls in peripuberty

“…It was also tested if animals with higher or lower percentage of major sperm defects have higher or lower values of insulin and leptin in seminal plasma, as the literature suggests that human patients with seminal plasma levels of insulin (Baccetti et al, 2002) and leptin (Aquila et al, 2008) below the physiologic standards have higher amount of sperm cells with major defects. Therefore, after statistical analysis (early and regular puberty), the animals were separated into groups of higher and lower percentage of major defects, according to CBRA (1998), for comparison of insulin and leptin values in the seminal plasma.…”