Effects of Kiss2 on the Expression of Gonadotropin Genes in the Pituitary of Nile Tilapia (Oreochromis niloticus)

Kisspeptin Treatment Restores Ovarian Function in Rats with Hypothyroidism

Background: Hypothyroidism causes ovarian dysfunction and infertility in women, in addition to being associated with hyperprolactinemia and reduced hypothalamic expression of kisspeptin (Kp). However, it remains unknown whether and how Kp is able to reverse the ovarian dysfunction caused by hypothyroidism. Methods: Hypothyroidism was induced in adult female Wistar rats using 6-propyl-2-thiouracil for 3 months. In the last month, half of the animals received Kp10. Blood samples were collected for dosage of free thyroxine, thyrotropin (TSH), luteinizing hormone (LH), prolactin (PRL), progesterone (P₄), and estradiol (E₂), and uteruses and ovaries were collected for histomorphometry. Body and ovarian weight and the number of corpora lutea were also evaluated. Half of the brains were evaluated by immunohistochemistry to Kp, and the other half had the arcuate nucleus of hypothalamus (ARC) and preoptic area microdissected for gene evaluation of Kiss1, Nkb, Pdyn, and Gnrh1. The pituitary gland and corpora lutea were also dissected for gene evaluation. Results: Hypothyroidism kept the animals predominantly acyclic and promoted a reduction in ovarian weight, number of corpora lutea, endometrial thickness, number of endometrial glands, and plasma LH, in addition to increasing the luteal messenger RNA (mRNA) expression of Star and Cyp11a1 and reducing 20αHsd. An increase in plasma PRL and P₄ levels was also caused by hypothyroidism. Kp immunoreactivity and Kiss1 and Nkb mRNA levels in the ARC and Kiss1 in the anteroventral periventricular nucleus of hypothalamus were reduced in hypothyroid rats. Hypothyroid animals had lower pituitary gene expression of Gnrhr, Lhb, Prl, and Drd2, and an increase in Tshb. The treatment with Kp10 restored estrous cyclicality, plasma LH, ovarian and uterine morphology, and Cyp11a1, 3βHsd, and 20αHsd mRNA levels in the corpora lutea. Kp10 treatment did not alter gene expression for Kiss1 or Nkb in the ARC of hypothyroid rats. Nevertheless, Kp10 increased Lhb mRNA levels and reduced Tshb in the pituitary compared with the hypothyroid group. Conclusions: The present findings characterize the inhibitory effects of hypothyroidism on the hypothalamic-pituitary-gonadal axis in female rats and demonstrate that Kp10 is able to reverse the ovarian dysfunction caused by hypothyroidism, regardless of hyperprolactinemia.

Functioning gonadotroph adenomas in premenopausal women: clinical and molecular characterization and review of the literature

PURPOSE

To summary the clinical features of premenopausal women with functioning gonadotroph adenomas (FGAs) and preliminarily explore their molecular characterization.

METHODS

12 premenopausal females with FGAs in our center were retrospectively analyzed. Previously reported cases were also summarized. The patients were clinically divided into FSH- or LH-predominant types according to their preoperative serum FSH/LH ratio. The expressions of related genes in the tumor tissues of female FGAs, non-functioning gonadotroph adenomas (NFGAs), and silent corticotropin adenomas were evaluated by RT-qPCR.

RESULTS

Of all the 12 patients with FGAs from our center, 11 (91.7%) were diagnosed as FSH-predominant type, and they all had menstrual disorders, including 9 with spontaneous ovarian hyperstimulation syndrome (sOHSS). Their hormonal profiles showed non-suppressed FSH (12.45 ± 7.34 IU/L) with hyperestrogenemia [median estradiol level 1353.0 pg/mL (636.0, 3535.0)]. The other patient (8.3%) with LH-predominant type mainly manifested with infertility and sustained elevated serum LH without FSH or estradiol increasing. 65 premenopausal FGAs patients were systematic reviewed. 60 patients (92.3%) were FSH-predominant type, including 86.7% presented with menstrual disorders, 16.7% reported infertility, and 98.2% (55/56) showed sOHSS. No sOHSS or hyperestrogenemia were found in the 5 patients (7.7%) with LH-predominant type. Pituitary imaging data revealed macroadenomas and microadenomas accounted for 89.2% and 10.8%, respectively. Of 63 patients (96.9%) who underwent pituitary adenoma resection, 77.8% had complete tumor resection and no recurrence at the last follow-up. The relative expressions of KISS1 mRNA were significantly higher in FGA group than in NFGA group (p = 0.018), and significantly positively correlated with the preoperative serum estradiol levels (p = 0.004).

CONCLUSIONS

Different clinical features were observed in premenopausal women with FGAs of FSH- or LH-predominant types. The elevated KISS1 expression in tumor tissues might involve in the secretion function of FGAs.

Characterization of kiss2/kissr2 system in largemouth bass (Micropterus salmoides) and Kiss2-10 peptide regulation of the hypothalamic-pituitary-gonadal axis

The kisspeptin system, which lies upstream of the hypothalamic-pituitary-gonadal (HPG) axis, is believed to function as a regulator of reproduction in teleosts. In this study, we isolated and characterized kiss2 and its receptor kissr2 in largemouth bass (Micropterus salmoides). The complete coding sequences of kiss2 and kissr2 were 375 and 1134 bp long and encoded precursor proteins 124 and 377 amino acid long, respectively. Real-time PCR showed that kiss2 and kissr2 were primarily expressed in the HPG axis. The expression profile of kiss2 and kissr2 varied with gonadal development, with the highest and lowest expression levels being detected during the immature and final maturation stages, respectively. Intraperitoneal injection of exogenous Kiss2-10 peptide increased the transcript levels of gnrh3, kissr2, fshβ, lhβ, ar, and er2 within 24 h (p < 0.05), as well as plasma levels of 17β-estradiol and testosterone. Histological analysis indicated that chronic administration of exogenous Kiss2-10 peptide accelerated vitellogenesis in females and spermatogenesis in males. Further, in situ hybridization revealed that kiss2 is expressed in the ooplasm and vitelline envelope of oocytes and the spermatocytes of testes. In addition, experiments using gonad tissue primary cell cultures indicated that exogenous Kiss2-10 peptide stimulates the expression of reproduction-related genes. Collectively, our findings indicate that the kiss2/kissr2 system in largemouth bass is involved in regulating gonadal development through the HPG axis.