Cell-type-specific regulation of genes involved in testicular lipid metabolism: fatty acid-binding proteins, diacylglycerol acyltransferases and perilipin 2

32 p.-6 fig.-1 tab.Male germ cell differentiation entails the synthesis and remodeling of membrane polar lipids and the formation of triacylglycerols (TAG). This requires fatty acid-binding proteins (FABP) for intracellular fatty acid traffic, a diacylglycerol acyltransferase (DGAT) to catalyze the final step of TAG biosynthesis, and a TAG storage mode. We examined the expression of genes encoding five members of the FABP family and two DGAT proteins, as well as the lipid droplet protein Perilipin 2 (PLIN2), during mouse testis development and in specific cells from seminiferous ephitelium. Fabp5 was distinctive of Sertoli cells and consequently was higher in prepubertal than in adult testis. Fabp3 expression increased in testis during postnatal development, associated to the functional differentiation of interstitial cells, but was low in germ cells. Fabp9, together with Fabp12, were prominently expressed in the latter. Their transcripts increased from spermatocytes to spermatids and, interestingly, were highest in spermatid-derived residual bodies. Sertoli and germ cells, which produce neutral lipids and store them in lipid droplets, expressed Plin2. Yet, while Dgat1 was detected in Sertoli cells, Dgat2 accumulated in germ cells with a similar pattern of expression as Fabp9. These results correlated with TAG levels also increasing with mouse germ cell differentiation to be highest in residual bodies, pointing to DGAT2 as the protein involved in the biosynthesis of such TAG. The age- and germ cell type-associated increases in Fabp9, Dgat2 and Plin2 levels are thus functionally related in the last stages of germ cell differentiation.Supported by grants from: The European Chemical Industry, Council-Long-range Research Initiative (CEFIC-LRi); MEDDTL (11-MRES-PNRPE-9-CVS-072) France, and CSIC (PIE 201020E016), Spain.Peer reviewe

Sequential depletion of rat testicular lipids with long-chain and very long-chain polyenoic fatty acids after X-ray-induced interruption of spermatogenesis[S]

When a single dose of X-rays is applied to the adult rat testis, stem spermatogonia are damaged, and spermatogenesis is interrupted. Supported by Sertoli cells, spermatogenic cells that endure irradiation complete their differentiation and gradually leave the testis as spermatozoa. In this study, the in vivo changes taking place a number of weeks after irradiation revealed cell-specific features of testicular lipid classes. A linear drop, taking about six weeks, in testis weight, nonlipid materials, free cholesterol, and 22:5n-6-rich glycerophospholipids took place with germ cell depletion. Sphingomyelins and ceramides with nonhydroxy very long-chain polyenoic fatty acids (n-VLCPUFA) disappeared in four weeks, together with the last spermatocytes, whereas species with 2-hydroxy VLCPUFA lasted for six weeks, disappearing with the last spermatids and spermatozoa. The amount per testis of 22:5n-6-rich triacylglycerols, unchanged for four weeks, fell between weeks 4 and 6, associating these lipids with spermatids and their residual bodies, detected as small, bright lipid droplets. In contrast, 22:5n-6-rich species of cholesterol esters and large lipid droplets increased in seminiferous tubules up to week 6, revealing they are Sertoli cell products. At week 30, the lipid and fatty acid profiles reflected the resulting permanent testicular involution. Our data highlight the importance of Sertoli cells in maintaining lipid homeostasis during normal spermatogenesis