TY - JOUR
T1 - Menaquinone-4 enhances testosterone production in rats and testis-derived tumor cells
AU - Ito, Asagi
AU - Shirakawa, Hitoshi
AU - Takumi, Naofumi
AU - Minegishi, Yoshihiko
AU - Ohashi, Ai
AU - Howlader, Zakir H.
AU - Ohsaki, Yusuke
AU - Sato, Toshiro
AU - Goto, Tomoko
AU - Komai, Michio
N1 - Funding Information:
We thank P. E. Giriwono of Tohoku University for critical reading of manuscript. This work was partially supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science to HS (#20380071).
PY - 2011
Y1 - 2011
N2 - Background: Vitamin K is essential for the posttranslational modification of various Gla proteins. Although it is widespread in several organs, including the testis, the function of vitamin K in these organs is not well characterized. In this study, we investigated the function of vitamin K in the testis and analyzed its role in steroidogenesis. Methods. Eight-week-old male Wistar rats were fed a diet supplemented with menaquinone-4 (MK-4, 75 mg/kg diet), one of the predominant K2vitamins present in the testis, for 5 weeks. In vivo testosterone levels of the rats' plasma and testes were measured by enzyme-linked immunosorbent assay, and in vitro testosterone levels of testis-derived tumor cells (I-10 cells) maintained in Ham's F-10 medium with 10% fetal bovine serum were measured following treatment with MK-4 (0 to 100 M) at several time points. Testosterone and cellular protein levels were analyzed with respect to their effects on steroidogenesis. Results: Testosterone levels in the plasma and testes of MK-4-fed rats were significantly increased compared to those of control rats, with no obvious differences in plasma luteinizing hormone levels. Secreted testosterone levels from I-10 cells were elevated by MK-4, but not by vitamin K1, in a dose-dependent manner independent of cAMP treatment. Western blot analysis revealed that expression of CYP11A, the rate-limiting enzyme in steroidogenesis, and phosphorylation levels of protein kinase A (PKA) and the cAMP response element-binding protein were all stimulated by the presence of MK-4. Enhancement of testosterone production was inhibited by H89, a specific inhibitor of PKA, but not by warfarin, an inhibitor of -glutamylcarboxylation. Conclusions: MK-4 stimulates testosterone production in rats and testis-derived tumor cells via activation of PKA. MK-4 may be involved in steroidogenesis in the testis, and its supplementation could reverse the downregulation of testosterone production in elders.
AB - Background: Vitamin K is essential for the posttranslational modification of various Gla proteins. Although it is widespread in several organs, including the testis, the function of vitamin K in these organs is not well characterized. In this study, we investigated the function of vitamin K in the testis and analyzed its role in steroidogenesis. Methods. Eight-week-old male Wistar rats were fed a diet supplemented with menaquinone-4 (MK-4, 75 mg/kg diet), one of the predominant K2vitamins present in the testis, for 5 weeks. In vivo testosterone levels of the rats' plasma and testes were measured by enzyme-linked immunosorbent assay, and in vitro testosterone levels of testis-derived tumor cells (I-10 cells) maintained in Ham's F-10 medium with 10% fetal bovine serum were measured following treatment with MK-4 (0 to 100 M) at several time points. Testosterone and cellular protein levels were analyzed with respect to their effects on steroidogenesis. Results: Testosterone levels in the plasma and testes of MK-4-fed rats were significantly increased compared to those of control rats, with no obvious differences in plasma luteinizing hormone levels. Secreted testosterone levels from I-10 cells were elevated by MK-4, but not by vitamin K1, in a dose-dependent manner independent of cAMP treatment. Western blot analysis revealed that expression of CYP11A, the rate-limiting enzyme in steroidogenesis, and phosphorylation levels of protein kinase A (PKA) and the cAMP response element-binding protein were all stimulated by the presence of MK-4. Enhancement of testosterone production was inhibited by H89, a specific inhibitor of PKA, but not by warfarin, an inhibitor of -glutamylcarboxylation. Conclusions: MK-4 stimulates testosterone production in rats and testis-derived tumor cells via activation of PKA. MK-4 may be involved in steroidogenesis in the testis, and its supplementation could reverse the downregulation of testosterone production in elders.
KW - I-10 cells
KW - menaquinone-4
KW - protein kinase A
KW - testis
KW - testosterone
KW - vitamin K
UR - http://www.scopus.com/inward/record.url?scp=80052653037&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=80052653037&partnerID=8YFLogxK
U2 - 10.1186/1476-511X-10-158
DO - 10.1186/1476-511X-10-158
M3 - Article
C2 - 21914161
AN - SCOPUS:80052653037
SN - 1476-511X
VL - 10
JO - Lipids in Health and Disease
JF - Lipids in Health and Disease
M1 - 158
ER -
