Feeding of phytosterols reduced testosterone production by modulating GnRH and GnIH expression in the brain and testes of male Japanese quail (Coturnix coturnix japonica)

Poult Sci. 2018 Mar 1;97(3):1066-1072. doi: 10.3382/ps/pex370.


Phytosterols (PS), or plant sterols used as cholesterol-lowering agents, have been shown to act as endocrine-disrupting chemicals in some laboratory animals. Moreover, dietary PS efficiently pass through the blood-brain barrier and accumulate in brain cell membranes. We asked whether the accumulation of PS affects reproduction through the hypothalamic-pituitary-gonadal axis. Thirty male quail chicks were randomly divided into 3 groups (control, 80 mg/kg BW, and 800 mg/kg BW), and daily single doses of PS or vehicle were gavaged into the crop sac from 15 to 100 d of age. At the end of the entire period, half of each group was injected intramuscularly with either 10 μg of chicken gonadotropin-releasing hormone 1 (cGnRH-1) or phosphate-buffered saline solution (PBS) as the vehicle. Blood was collected before and 30 min after cGnRH-1 challenge by jugular venipuncture and decapitation, respectively. The results indicated that testosterone concentrations were low (P < 0.05) before (800 mg/kg BW) and after GnRH challenge in PS-treated quails compared with controls (P < 0.001). However, luteinizing hormone (LH) levels were not different among the groups before cGnRH-1 challenge. In addition, PS-gavaged animals failed to manifest increased LH levels after cGnRH-1 injection (P < 0.01). The same trends were observed in pituitary LH levels at 800 mg/kg BW PS after cGnRH-1 injection (P < 0.05). Real-time PCR results revealed that PS (800 mg/kg BW) feeding reduced expression of GnRH-1 in the brain and testes compared to controls. However, gonadotropin-inhibitory hormone (GnIH) expression was significantly elevated before and after GnRH-1 challenges in the brain and testes. Collectively, these results suggest that brain-mediated effects of PS on gonadal function occurs via the induction of GnIH gene expression, and these indirect effects are less potent than direct effects.

MeSH terms

  • Animal Feed / analysis
  • Animals
  • Avian Proteins / genetics*
  • Avian Proteins / metabolism
  • Brain / metabolism
  • Coturnix / metabolism*
  • Diet / veterinary
  • Dose-Response Relationship, Drug
  • Endocrine Disruptors / pharmacology*
  • Gonadotropin-Releasing Hormone / genetics*
  • Gonadotropin-Releasing Hormone / metabolism
  • Hypothalamic Hormones / genetics*
  • Hypothalamic Hormones / metabolism
  • Male
  • Phytosterols / pharmacology*
  • Random Allocation
  • Testis / metabolism
  • Testosterone / biosynthesis*


  • Avian Proteins
  • Endocrine Disruptors
  • Hypothalamic Hormones
  • Phytosterols
  • gonadotropin-inhibitory hormone, Coturnix japonica
  • Gonadotropin-Releasing Hormone
  • Testosterone