The biosynthesis of sphingolipids with very-long-chain PUFA is enhanced by testoterone in spermatogenic cells

Abstract

Ceramide (Cer), sphingomyelin (SM), glucosylCer (GlcCer), and complex glycosphingolipid species with very-long-chain PUFA (VLCPUFA), in nonhydroxy (n-V) and 2-hydroxy (h-V) forms, characterize the spermatogenic cell lipidome in rodents. The h- V/n-V ratio increases with differentiation from pachytene spermatocytes (PtS) to round spermatids (RS) and further stages. We first established that PtS and RS in culture are able to synthesize de novo Cer, SM, and GlcCer autonomously, and then studied the influence on such synthesis of testosterone, alone and after adding the medium conditioned by Sertoli cells (SCM). Using [3H]16:0 as precursor, the formation of [3H]Cer and [3H]SM species with VLCPUFA was quite active, especially n-V SM. The label was mostly in the sphingoid base, 16:0, and a part was in [3H]VLCPUFA. De novo synthesis inhibition affected distinctly the [3H]SM/[3H]Cer ratios in PtS and RS. The genes CerS3, SMS1, SMS2, and GCS diverged in expression with differentiation. Testosterone stimulated the de novo biosynthesis of n-V [3H]SM in PtS and increased the [3H]Cer/[3H]SM labeling ratio in RS. Supplementation of testosterone-containing medium with the SCM robustly stimulated these reactions. Testosterone also stimulated the expression of two fatty acid elongases and fatty acid 2-hydroxylase. We speculate that germ cells must have a form of receptor to testosterone. The SCM effect is consistent with one of the known secretory products from Sertoli cells, most likely the androgen-binding protein, facilitating the availability of the hormone to germ cells, but we cannot rule out other molecules or even structures (e.g. exosomes) that might be present in the SCM.