Serum concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH) in KISS1 knockout gilts treated with neurokinin B, kisspeptin, and GnRH hormone analogs

Authors: Lents, Clay; AHERN, DANIEL - University Of Nebraska; Wilson, Kyle; ROSS, CAITLIN - University Of Nebraska; MILLS, GINGER - University Of Nebraska; ELSKEN, DOROTHY - University Of Nebraska; FLOREZ, JULIO - Acceligen Inc; MARTINS, KYRA - Acceligen Inc; BELTRAMO, MASSIMILIANO - Inrae; SONSTEGARD, TAD - Acceligen Inc; Cushman, Robert - Bob; WHITE, BRETT - University Of Nebraska

Submitted to: Society for the Study of Reproduction Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/17/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Kisspeptin knockout (KISS1-/-) pigs exhibit hypogonadotropic hypogonadism. Hormone analogs stimulate gonadotropin secretion and ovulation in mice and humans with induced or naturally occurring mutations in the KISS1 gene. It is unknown how such agonists affect gonadotropin secretion in KISS1-/- gilts. The goal was to characterize LH and FSH secretion in gilts treated with hormone analogs activating the hypothalamic-pituitary-gonadal axis. Gilts (254 d of age) were jugular catheterized for serial blood collection before and after treatments. Concentrations of LH and FSH were quantified with RIA. Data were analyzed as repeated measures with genotype and time as fixed effects. In Experiment 1, baseline hormone secretion was established for 6 h, then gilts were treated with a neurokinin 3 receptor (NK3R) agonist (senktide; 10 mg/kg, i.v.) to activate KISS1 neurons. In Experiment 2, gilts were estrus synchronized with altrenogest (18 mg/d, 14 d) and treated with PG600 (1000 IU hCG, 2000 IU PMSG, i.m.) 12 h after altrenogest withdrawal to synchronize follicular development. At 112 h after PG600, a kisspeptin receptor agonist (C6; 0.3 nMol/kg, i.m.) was administered to activate GnRH neurons. In Experiment 3, gilts were treated with GnRH (Cystorelin; 150 ng/kg, i.v.) to stimulate gonadotroph cells. In Experiment 4, gilts received an estradiol implant and GnRH with increasing frequency every 2 wk (1500 ng/kg, 1/d; 1000 ng/kg, 2/d; 500 ng/kg, 4/d, i.v.) followed with PMSG (1000 IU) and hCG (1000 IU) 78 h apart to induce follicular development and ovulation. LH and FSH pulse amplitude, but not pulse frequency, was greater in KISS1+/- and KISS1+/+ gilts compared with KISS1-/- gilts, which had reduced serum LH and FSH concentrations (P < 0.01). LH but not FSH concentrations in KISS1+/- and KISS1+/+ gilts were increased for 60 min following senktide (P < 0.001), which did not affect LH or FSH in KISS1-/- gilts. C6 treatment did not affect FSH but increased circulating LH in KISS1+/- and KISS1+/+ gilts for approximately 24 h (P < 0.05), but C6 did not affect LH in KISS1-/- gilts. The C6 treatment induced ovulation in all KISS1+/+ gilts but none of the KISS1-/- gilts. A single acute injection of GnRH increased LH in KISS1+/- and KISS1+/+ gilts but not in KISS1-/- gilts (P < 0.001). LH secretion in KISS1-/- gilts was increased modestly with a greater dose and frequency of GnRH (P < 0.05). One KISS1-/- gilt ovulated 2 follicles after hCG and one had luteinized follicles, but the rest failed to ovulate. A single functional KISS1 allele is sufficient to confer normal reproductive endocrine function in pigs. This is the first report to confirm NK3R regulates LH secretion in gilts. Lack of GnRH-induced LH secretion in KISS1-/- gilts may result from insufficient releasable pools of LH due to lack of sufficient GnRH priming. Optimization of treatments will be required to induce full ovulation in KISS1-/- gilts.