Biochemical and Biophysical Research Communications
Levels of the neuropeptide phoenixin-14 and its receptor GRP173 in the hypothalamus, ovary and periovarian adipose tissue in rat model of polycystic ovary syndrome
Introduction
Phoenixin (PNX) is a newly discovered peptide produced mainly in hypothalamus by proteolytic cleavage of a small integral membrane protein 20 (Smim20) [1]. This neuropeptide mainly exists in two active isoforms: phoenixin – 14 (PNX-14) and phoenixin – 20 (PNX-20) [1,2]. PNX-14 is a 14 residue peptide and was found in multiple species including humans, rats, mice, pigs and dogs [1,2]. PNX-20 is a 20 residue peptide, an N-terminal extended PNX-14 and differs in one amino acid between the coding region of human, canine or porcine sequences [1]. Moreover, PNX was detected in various tissues, including the hypothalamus, pituitary, heart, gastrointestinal and pancreatic islets [3]. PNX has been linked to metabolic syndrome, different behaviours, sensory perception, the cardiovascular system as well as food intake [3]. An in vitro study has shown that PNX increased preadipocytes proliferation and differentiation into mature adipocytes via cAMP/Epac – dependent pathways [4]. Moreover, PNX stimulated insulin secretion by cAMP/Epac signaling, while cell growth and insulin expression were mediated via extracellular signal-regulated kinase (ERK1/2)- and protein kinase B (Akt)-pathways, indicating that PNX may play a role in controlling glycaemia by interacting with pancreatic beta cells [5].
In recent years effect of PNX has been observed also in reproduction [1,6,7]. In vitro experiments on anterior pituitary cells showed that PNX stimulated gonadotropin secretion by increasing expression of GnRH receptors [1]. Interestingly, most of the reproductive functions of PNX including stimulation of mRNA expression in GnRH neurons, modulation of reproductive genes [8], delaying the onset of estrous [9] were mediated through the G protein-coupled receptor 173 (GRP173); inhibition of GRP173 by siRNA reduced these effects. A recent study showed that PNX is also an intraovarian factor, which stimulates ovarian follicular cells development via the receptor GRP173 and protein kinase A (PKA) by accelerating proliferation of human granulosa cells (Gc) and inducing estradiol (E2) secretion [10]. Moreover, only one study showed higher plasma levels of PNX-14 in reproductive pathology - polycystic ovarian syndrome (PCOS) patients [11].
PCOS is a very common endocrine disorder in women of reproductive age and characterized by ovulatory dysfunction, polycystic ovaries, increased luteinizing hormone (LH) concentrations, insulin resistance and hyperandrogenic symptoms such as hirsutism, acne and menstrual irregularity [12]. PCOS women are frequently overweight or obese with increased risk of type – 2 diabetes, endometrial cancer, impaired glucose tolerance and cardiovascular disease [13]. However, the exact pathophysiology of PCOS remains largely unclear, therefore novel insights into the mechanism of PCOS are imperative to identify potential diagnostic markers and therapeutic targets for this endocrine disease.
The aim of this study was to identify mRNA and protein expressions of Smim20/PNX-14 and GPR173 receptor in the hypothalamus, ovary and periovarian adipose tissue (PAT) as well as plasma PNX-14 levels in control and PCOS rats. Additionally, the phosphorylation of kinases ERK1/2, PKA, Akt were also examined. In our experiments, we used letrozole induced rat model of PCOS. Letrozole, a non-steroidal aromatase inhibitor, blocks conversion of testosterone (T) into E2 and leads to higher levels of androgen [14] thus reflecting reproductive disorders and metabolic abnormalities of clinical PCOS [15].
Section snippets
Animal and ethics statement
Six-week-old female Wistar rats (weighing 176.9 g ± 14.54 g) were purchased from the Faculty of Pharmacy JU Medical College and Mossakowski Medical Research Centre Polish Academy of Sciences (Poland). Animals were housed in controlled conditions of temperature, humidity and light (LD 12/12) with ad libitum availability of food and water. Rats were allowed to acclimatize for one week before treatment. All procedures performed in studies were approved by the 1st Local Ethical Commission on Animal
Results and discussion
PCOS is a very common endocrine disorder in women of reproductive age and it’s characterized by abnormal gonadotropin secretion and androgen production, resulting in chronic anovulation which leads to infertility. Its etiology and pathophysiology has not yet been fully understood, so in our study, we employed a letrozole induced rat model of PCOS, which exhibits hormonal, reproductive and metabolic signs similar to the women PCOS [14,15]. We observed in PCOS rats a significant increase in body
Funding
This work was supported by the Jagiellonian University, Poland (K/ZDS/00008) and 2017/25/N/NZ4/02760 from the National Science Centre of Poland.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
We sincerely appreciate Michel Khoury, PhD, for reviewing the English grammar.
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Expression and in vitro effect of phoenixin-14 on the porcine ovarian granulosa cells
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2023, General and Comparative EndocrinologyExpression of phoenixin-14 and nesfatin-1 in the hypothalamo–pituitary–gonadal axis in the phases of the estrous cycle
2023, NeuropeptidesCitation Excerpt :In this context, the role of NUCB2/nesfatin-1 in the regulation of energy homeostasis and ovarian steroidogenesis was revealed (Prinz et al., 2016). Kalamon et al. (2020) reported that the serum PNX-14 concentration was considerably higher in rats with PCOS when compared with the proestrus and diestrus groups. In addition, serum NUCB2/nesfatin-1 levels were significantly higher in patients with PCOS than in healthy individuals, and this situation was associated with the presence of PCOS (Ademoglu et al., 2014).
Levels of spexin and its receptors GALR2 and GALR3 in the hypothalamus and ovary of letrozole-induced polycystic ovary syndrome in rats
2022, Biochemical and Biophysical Research CommunicationsCitation Excerpt :The difference in mRNA and protein GALR3 levels can be explained by transcriptional, post-transcriptional and translational regulations, and discrepancies in mRNA and protein stability [32,33]. Similarly, our previous study showed that the Smim20 (PNX precursor) transcript concentration in the hypothalamus was not parallel with the PNX-14 protein abundance [19]. Interestingly, the previous study by Guler and Demir [26] suggests that SPX can be involved in the pathophysiology of PCOS via a negative correlation with increasing LH levels in PCOS women.
Canine cystic endometrial hyperplasia and pyometra may downregulate neuropeptide phoenixin and GPR173 receptor expression
2022, Animal Reproduction ScienceCitation Excerpt :Among the CEH, P-I and P-II groups, only in the P-I group did we observe a positive tendency of correlation (P ≤ 0.1); however, these data were not statistically significant (P > 0.05). Recently published results demonstrated that circulating levels of PNX may be affected by diseases of the reproductive system (Kalamon et al., 2020; Ullah et al., 2017). The modulatory effects of PNX on LH and GnRH secretion indicate that this peptide is involved in the HPG axis.