Menaquinone-4 enhances testosterone production in rats and testis-derived tumor cells

Lipids Health Dis. 2011 Sep 13;10:158. doi: 10.1186/1476-511X-10-158.

Abstract

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 K₂ vitamins 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 μM) 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 γ-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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carbon-Carbon Ligases / antagonists & inhibitors
  • Cell Line, Tumor
  • Cholesterol Side-Chain Cleavage Enzyme / metabolism
  • Cyclic AMP Response Element-Binding Protein / metabolism
  • Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors
  • Cyclic AMP-Dependent Protein Kinases / chemistry
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Leydig Cells / drug effects
  • Leydig Cells / metabolism*
  • Liver / drug effects
  • Liver / metabolism
  • Male
  • Mice
  • Phosphorylation / drug effects
  • Protein Kinase Inhibitors / pharmacology
  • Protein Processing, Post-Translational / drug effects
  • Rats
  • Rats, Wistar
  • Specific Pathogen-Free Organisms
  • Testis / drug effects
  • Testis / metabolism*
  • Testosterone / blood
  • Testosterone / metabolism*
  • Tissue Distribution
  • Up-Regulation / drug effects*
  • Vitamin K 1 / antagonists & inhibitors
  • Vitamin K 1 / metabolism
  • Vitamin K 2 / analogs & derivatives*
  • Vitamin K 2 / pharmacokinetics
  • Vitamin K 2 / pharmacology

Substances

  • Cyclic AMP Response Element-Binding Protein
  • Protein Kinase Inhibitors
  • Vitamin K 2
  • menatetrenone
  • Testosterone
  • Vitamin K 1
  • Cholesterol Side-Chain Cleavage Enzyme
  • Cyclic AMP-Dependent Protein Kinases
  • Carbon-Carbon Ligases
  • glutamyl carboxylase