Expression and regulation of glucose transporter 8 in rat Leydig cells

Abstract

Basal and LH/human chorionic gonadotropin (hCG)-stimulated testosterone formation by Leydig cells is dependent on ambient glucose levels. Inhibition of glucose uptake is associated with decreased testosterone formation. Recently, glucose transporter 8 (GLUT8) has been shown to be highly expressed in the testis. In the present study, we have investigated the expression and regulation of the GLUT8 gene in rat Leydig cells. Primers were designed by using sequences that are not conserved in GLUT1 to GLUT5 and that contain the glycosylation region of GLUT8. This yielded an amplicon of 186 bp. The tissue-specific expression experiments in adult rat (55-to 65-day-old) tissues revealed that GLUT8 is expressed predominantly in the testis, in smaller amounts in heart and kidney, and in negligible amounts in liver and spleen. Furthermore, GLUT8 mRNA was found to be highly expressed in crude interstitial cells, Leydig cells and testicular and epididymal germ cells. In prepubertal rat (20-day-old) tissues, GLUT8 expression was comparatively much lower than in the adult rat tissues. By comparative RT-PCR, hCG caused dose-and timedependent increases of GLUT8 mRNA levels. hCG and IGF-I had synergistic effects on GLUT8 mRNA and protein expression. GLUT1 and GLUT3 were also found to be expressed in Leydig cells. However, neither GLUT1 nor GLUT3 were affected by treatments with hCG, IGF-I or hCG and IGF-I combined. The addition of murine interleukin-1 (mIL-1 ; 10 ng/ml), murine tumor necrosis factor-(mTNF-; 10 ng/ml), murine interferon-(mIFN-; 500 U/ml) separately or in combination decreased hCG-induced GLUT8 mRNA levels significantly. In conclusion, GLUT8 mRNA in Leydig cells was positively regulated by hCG and IGF-I and downregulated by cytokines, mIL-1 , mTNF-and mIFN-. These results indicate that hCG, growth factors and cytokines affect Leydig cell steroidogenesis by modulating GLUT8 expression.

Paternal effect on embryo quality in diabetic mice is related to poor sperm quality and associated with decreased glucose transporter expression

“…We have also reported that SLC2A9 protein expression was significantly increased in the kidney and liver from STZinduced diabetic mice compared with non-diabetic mice (Keembiyehetty et al 2006). Although SLC2A8 (Ibberson et al 2002, Schurmann et al 2002, Chen et al 2003, Gomez et al 2006, Kim & Moley 2007) and SLC2A9 (Kim & Moley 2007) are expressed in the testis and sperm, it is not known whether their expression or localization is altered in the diabetic male reproductive system or not. The objective of this study was to determine whether sperm quality, fertilization capacity, and subsequent embryo development are altered in diabetic male mice and whether differences in facilitative glucose transporter (SLC2A) expression in the testis and sperm exist.…”

Differential expression of glucose transporter GLUT8 during mouse spermatogenesis

“…In spite of the fact that it is mainly expressed in testis, with a possible function of glucose and fructose transport, the precise localization of this protein in testicular cells remains unclear and controversial. It has been reported that GLUT8 expression is restricted to the type I spermatocytes in the rat (Ibberson et al 2002), in the innermost cells within the seminiferous tubules and spermatozoa in mice and man (Schü rmann et al 2002), and in rat Leydig cells (Chen et al 2003). It has also been reported that GLUT8 seems to be hormonally regulated in testis, since it is detected neither in testicular carcinoma nor under estrogen treatment (Doege et al 2000).…”

Effects of overexpression of CXCL10 (cytokine-responsive gene-2) on MA-10 mouse Leydig tumor cell steroidogenesis and proliferation

“…The proteins of the media were then concentrated by precipitation with cold acetone and dissolved in ice-cold lysis buffer. The CXCL10 protein in the concentrated cell medium was detected by Western blot analysis, as described previously (Chen et al 2003). Recombinant rat CXCL10 (Santa Cruz Biotechnology, Santa Cruz, CA, USA) was used as a positive control.…”