Interaction of Kisspeptin and the Somatotropic Axis

Abstract

Kisspeptin, a regulator of gonadotropin-releasing hormone, has been hypothesized as an integrator of nutrition and hormones critical to metabolism and the regulation of reproduction. Growth hormone (GH) is necessary for optimal reproduction and recent evidence suggests that its secretion may be influenced by kisspeptin. The objectives of this study were to determine whether the effect of kisspeptin to stimulate GH release is due to an interaction with growth hormone-releasing hormone (GHRH) or somatostatin (SS), or an effect at the hypothalamus. Intravenous injection and infusion of kisspeptin [500 pmol/kg BW (650 ng/kg)/h × 5 h] to cows (n = 5) increased serum concentrations of luteinizing hormone (LH) but not GH. Pretreatment with kisspeptin injection and infusion in cows (n = 5) reduced the stimulatory effect of GHRH (0.05 µg/kg BW) on GH secretion. However, the magnitude of the GH response to GHRH (assessed by incremental AUC) was not affected by kisspeptin. In these same cows, administration of kisspeptin prevented the increase in GH induced by SS infusion (0.5 µg/kg BW/ h × 1.5 h) withdrawal. Peripheral administration of kisspeptin [200 and 1,000 pmol/kg BW (260 and 1,300 ng/kg)] increased serum concentrations of LH but not GH in ewes (n = 8). However, concentrations of GH were stimulated by central kisspeptin treatment [100 and 200 pmol/kg BW (130 and 260 ng/kg)] in ewes. In addition to activating the gonadotropic axis, kisspeptin can activate the somatotropic axis in ruminants. Present data support the concept of a central site of action for this effect.

Kisspeptin as a master player in the central control of reproduction in mammals: An overview of kisspeptin research in domestic animals

“…Intravenous infusion of Kp‐10 over 5 h in OVX cows increased plasma LH concentrations for as long as 140 min following the start of infusion, but the stimulatory action of the peptide was not observed thereafter (Whitlock et al . ).…”

“…; Whitlock et al . ), whereas i.c.v. administration of Kp‐10 significantly increased GH secretion in OVX ewes (Whitlock et al .…”

“…Whitlock et al . (, ) investigated the effect of Kp‐10 administration on LH secretion in adult ovariectomized (OVX) cows. Bolus i.v.…”

“…) but had no effect without the concomitant steroid treatment (Whitlock et al . , ). Kadokawa et al .…”

Mystic Effects of Kisspeptin in Reproduction of Livestock

“…Central administration of Kp-10 augmented GnRH concentrations in the cerebrospinal fluid and increased LH concentrations in the plasma of sheep (Messager et al, 2005). Furthermore, Kisspeptin-10 (Kp-10) stimulated circulating concentrations of LH in Holstein cows and ovariectomized Jersey cows, and interestingly the sensitivity of LH to exogenous Kp-10 stimulation seems to be enhanced with lactation (Whitlock et al, 2010). Kisspeptin expression is structured by steroids as the quantity of Kp positive cells in the ARC increased in OVX ewes paralleled to intact ewes, the contradictory being found in the preoptic area (POA) Kp neurons (Smith et al2007).…”