Kisspeptin and neurokinin B interactions in modulating gonadotropin secretion in women with polycystic ovary syndrome

Abstract

Study question: What is the role of the hypothalamic neuropeptide neurokinin B (NKB) and its interaction with kisspeptin on GnRH/LH secretion in women with polycystic ovary syndrome (PCOS)?

Summary answer: Administration of neurokinin 3 receptor antagonist (NK3Ra) for 7 days reduced LH and FSH secretion and LH pulse frequency in women with PCOS, whilst the stimulatory LH response to kisspeptin-10 was maintained.

What is known already: PCOS is characterized by abnormal GnRH/LH secretion. NKB and kisspeptin are master regulators of GnRH/LH secretion, but their role in PCOS is unclear.

Study design, size, duration: The NK3Ra MLE4901, 40 mg orally twice a day, was administered to women with PCOS for 7 days (n = 8) (vs no treatment, n = 7). On the last day of NK3Ra administration or the equivalent day in those not treated, women were randomized to 7-h kisspeptin-10 (4 µg/kg/h i.v.) or vehicle infusion. This was repeated with the alternate infusion in a subsequent cycle.

Participants/materials, setting, methods: Subjects were women with PCOS, studied in a Clinical Research Facility. Reproductive hormones were measured before and after NK3Ra administration. On the last day of NK3Ra administration (or the equivalent cycle day in untreated women), all women attended for an 8-h frequent blood sampling to allow analysis of the pulsatile LH secretion.

Main results and the role of chance: NK3Ra reduced LH secretion (4.0 ± 0.4 vs 6.5 ± 0.8 IU/l, P < 0.05) and pulse frequency (0.5 ± 0.1 vs 0.8 ± 0.1 pulses/h, P < 0.05); FSH secretion was also reduced (2.0 ± 0.3 vs 2.5 ± 0.4 IU/l, P < 0.05). Without NK3Ra pre-treatment, kisspeptin-10 increased LH secretion (5.2 ± 0.5 to 7.8 ± 1.0 IU/L, P < 0.05), with a positive relationship to oestradiol concentrations (r2 = 0.59, P < 0.05). After NK3Ra administration, the LH response to kisspeptin-10 was preserved (vehicle 3.5 ± 0.3 vs 9.0 ± 2.2 IU/l with kisspeptin-10, P < 0.05), but the positive correlation with oestradiol concentrations was abolished (r2 = 0.07, ns. after NK3Ra). FSH secretion was increased by kisspeptin-10 after NK3Ra treatment, but not without NK3Ra treatment.

Limitations, reasons for caution: The study did not explore the dose relationship of the effect of NK3R antagonism. The impact of obesity or other aspects of the variability of the PCOS phenotype was not studied due to the small number of subjects.

Wider implications of the findings: These data demonstrate the interactive regulation of GnRH/LH secretion by NKB and kisspeptin in PCOS, and that the NKB system mediates aspects of oestrogenic feedback.

Study funding/competing interest(s): Wellcome Trust through Scottish Translational Medicine and Therapeutics Initiative (102419/Z/13/A) and MRC grants (G0701682 to R.P.M. and R.A.A.) and MR/N022556/1 to the MRC Centre for Reproductive Health. This work was performed within the Edinburgh Clinical Research Facility. J.T.G. has undertaken consultancy work for AstraZeneca and Takeda Pharmaceuticals and is an employee of Boehringer Ingelheim. R.P.M. has consulted for Ogeda and was CEO of Peptocrine. R.A.A. has undertaken consultancy work for Merck, Ferring, NeRRe Therapeutics and Sojournix Inc. J.D.V. and K.S. have nothing to disclose.

Trial registration number: N/A.

Keywords: neurokinin B / kisspeptin / LH pulsatility / PCOS / GnRH.

Figure 1

Study protocol diagram. Following medroxyprogesterone withdrawal menstruation, in eight treatment cycles, women received neurokinin 3 receptor antagonist (NK3Ra; MLE4901) 40 mg oral twice daily starting from Cycle day 1–2 for 7 days, and in 7 cycles, women received no treatment. On Day 6 or 7 of NK3Ra dosing in the treatment group and the equivalent day in the no treatment group, women were randomized to 7 h kisspeptin-10 or vehicle infusion, returning for alternate infusion after subsequent medroxyprogesterone induced menstruation. Reproductive hormones were measured throughout the study and LH pulsatility was assessed during 10-min frequent blood sampling for 8 h on the infusion day.

Figure 2

Reproductive hormone response to administration of NK3Ra or no treatment followed by kisspeptin/vehicle infusion cycles in women with polycystic ovary syndrome. (A–C) Mean LH (A), FSH (B) and oestradiol (C) concentrations at the end of NK3Ra treatment comparted to pre-treatment day (n = 8). (D–F) Time course analysis of frequent blood sampling of LH (D), FSH (E) and oestradiol (F) levels before (Time 0) and during 7 h of vehicle or kisspeptin-10 infusion in the treatment (NK3Ra) group (n = 8) and no treatment group (n = 7). Kisspeptin-10 stimulated LH secretion in both vehicle and NK3Ra-treated women (P < 0.05) but did not affect FSH secretion. Serum oestradiol levels were higher after kisspeptin-10 administration compared to pre-treatment concentrations (P < 0.001), although were not different compared to that after infusion with vehicle. LH levels were lower in NK3Ra compared with vehicle-treated women (P < 0.0001), although Bonferroni’s post hoc multiple comparison test found no significant changes at specific time points. (G and H) Mean LH (G), FSH (H) and oestradiol (I) concentrations at the end of kisspeptin-10 treatment comparted to pre-treatment (n = 7). Data are presented as mean ± SEM. *P < 0.05; ***P < 0.001. Mean differences at specific time points for vehicle versus kisspeptin-10 infused in no NK3Ra-treated women: *P < 0.05, ***P < 0.001. For vehicle vs kisspeptin-10 in NK3Ra-treated women: ^ΨP < 0.05.

Figure 3

Correlation between oestradiol concentrations and LH response to kisspeptin-10 in with and without NK3Ra. Kisspeptin-10 response on LH secretion was positively related to oestradiol levels (r² = 0.59, P < 0.05), whilst this was not seen with NK3Ra treatment (r² = 0.07, ns).

Figure 4

Analysis of 8-h secretory patterns during vehicle and kisspeptin-10 infusion with and without NK3Ra. (A) Illustrative LH pulse profile from one subject undergoing vehicle (green diamonds), NK3Ra (purple squares), kisspeptin-10 (red triangles) and NK3Ra followed by kisspeptin-10 (blue circles) treatment visits. Mean LH pulse frequency (B), secretory mass of LH per pulse (C), basal (non-pulsatile) LH secretion (D), pulsatile LH secretion (E) and the relative orderliness/regularity of LH secretory pattern (F) during vehicle and kisspeptin-10 infusion with (n = 8) and without (n = 7) pre-treatment with NK3Ra. The NK3Ra significantly reduced LH pulse frequency. While Kp-10 alone did not affect LH pulse frequency, it did increase it in the presence of NK3Ra. Pulsatile LH secretion and LH secretory mass were increased by Kp-10, but not affected by NK3Ra. Basal LH secretion was reduced by NK3Ra, but was not stimulated by Kp-10 alone or with NK3Ra. Both NK3Ra and Kp-10 increased the relative orderliness/regularity of LH secretory pattern (i.e. reduced ApEn). Mean ± SEM. *P < 0.05.