NAMPT (visfatin) in the chicken testis: influence of sexual maturation on cellular localization, plasma levels and gene and protein expression

Abstract

Nicotinamide phosphoribosyltransferase (NAMPT) is a cytokine hormone and rate-limiting enzyme involved in production of NAD and therefore affects a variety of cellular functions requiring NAD. Spermatogenesis and testicular steroidogenesis are likely to depend on NAD-dependent reactions and may therefore be affected by changes in testicular NAMPT expression. The objectives of the present study are to investigate testicular NAMPT expression as well as plasma NAMPT levels in prepubertal and adult chickens. By RT-PCR, NAMPT cDNA expression was detected in prepubertal and adult chicken testes. Using immunohistochemistry, NAMPT was predominantly localized in the nucleus of myoid cells, Sertoli cells, and Leydig cells in the prepubertal chicken testis. In adult chickens, however, NAMPT-immunostaining was observed in the cytoplasm of Leydig cells, Sertoli cells, primary spermatocytes, secondary spermatocytes, round spermatids, and elongated spermatids, but not in the spermatogonial cells. Using real-time quantitative PCR, adult chicken testis was found to contain fourfold greater NAMPT mRNA quantity compared with prepubertal chickens. Testicular NAMPT protein quantities determined by western blotting were not significantly different between adult and prepubertal chicken testes. Using immunoblotting, NAMPT was detected in the seminal plasma and sperm protein extracts obtained from chicken semen. Plasma NAMPT levels, determined by enzyme immunoassay, were at least 28-fold higher in the adult chickens compared with prepubertal male chickens. Taken together, sexual maturation is associated with several changes in testicular NAMPT expression indicating that NAMPT is likely to play a significant role in testicular functions such as spermatogenesis and steroidogenesis.