A potential role for kisspeptin in puberty onset in sheep

Abstract

In peripubertal sheep, a decrease in inhibition by estradiol leads to an increase in gonadotropin releasing hormone (GnRH), and thus luteinizing hormone (LH), secretion, causing the onset of puberty. The neural mechanisms governing this process remain largely unknown. Kisspeptin is expressed in the arcuate nucleus of the hypothalamus of sheep and stimulates GnRH/LH secretion. We hypothesized that kisspeptin expression would be greater in postpubertal sheep and that its expression would be increased in the absence of steroid negative feedback. Four groups of females were used: prepubertal intact, prepubertal ovariectomized, postpubertal ewes in the early follicular phase, and postpubertal ovariectomized. LH was measured to confirm the endocrine state of each animal. Kisspeptin expression was greater in postpubertal ewes as compared to prepubertal ewes, and was increased by ovariectomy only in the prepubertal group. The increase in kisspeptin cell numbers in postpubertal females is consistent with a role for kisspeptin in puberty onset in the sheep. Further, the increase in kisspeptin expression with ovariectomy in prepubertal females indicates that decreased kisspeptin cell numbers in intact prepubertal females is due to the negative feedback effects of estradiol. NIH Grant 5P20RR016477 to the West Virginia IDeA Network for Biomedical Research Excellence