The effect of the estrous cycle on the expression of prepro-orexin gene and protein and the levels of orexin A and B in the porcine pituitary

Abstract

Hypothalamic peptides orexin A (OXA) and orexin B (OXB) are derived from the proteolytic cleavage of a common precursor molecule, prepro-orexin (PPO). They act via two orexin receptors (OX1R and OX2R), which belong to the G-protein coupled receptor superfamily. Orexins are implicated in the regulation of arousal states, energy homeostasis and reproductive neuroendocrine function. The objective of this study was to investigate the presence and changes in orexin expression in the porcine pituitary during the estrous cycle. Adenohypophysis (AP) and neurohypophysis (NP) tissue samples were harvested on days 2 to 3, 10 to 12, 14 to 16, and 17 to 19 of the estrous cycle. The expression of the PPO gene increased in AP and NP during the estrous cycle. The highest PPO protein concentrations in AP were reported on days 2 to 3 (P < 0.05), and in NP -on days 10 to 12 and 17 to 19 ( P < 0.05). The expression of PPO mRNA was lower in AP than in NP, but PPO protein levels were higher in AP. In AP, OXA immunoreactivity was higher ( P < 0.05) on days 10 to 12 and 14 to 16. In NP, the highest ( P < 0.05) content of the analyzed protein was observed on days 10 to 12 and the lowest ( P < 0.05) -on days 14 to 16 and 17 to 19. OXB immunoreactivity in AP reached the highest level ( P < 0.05) on days 2 to 3, and the lowest level ( P < 0.05) was determined on days 10 to 12 and 17 to 19. OXB protein concentrations in NP peaked ( P < 0.05) on days 10 to 12 of the cycle. Our study was the first experiment to demonstrate the expression of the orexin gene and orexin proteins in the porcine pituitary and the correlations between expression levels and the phase of the estrous cycle. Keywords: prepro-orexin, orexin A and B, pituitary, estrous cycle, pig ImplicationsThe relationship between nutritional status and reproductive success in animals has been studied for many years. Considerable evidence has been accumulated to implicate the existence of a common endocrine system that controls metabolism and the reproductive system. It is suggested that orexins belong to the group of hormones, which regulate metabolic status and reproduction. In this study, we demonstrated differences in orexin gene and orexin proteins in the porcine pituitary during the estrous cycle. The results imply the impact of hormonal milieu on orexins' expression in the porcine pituitary. A sound knowledge of mechanisms that control energy homeostasis and reproduction is needed in animal breeding practice. IntroductionOrexin A and B (OXA, OXB), also known as hypocretin 1 and 2, are hypothalamic peptides with a 46% sequence homology. OXA is a 33-amino acid peptide with a molecular mass of~3.5 kDa, which has an N-terminal pyroglutamyl residue and C-terminal amidation. OXB is a 28-amino acid peptide with a molecular mass of~2.9 kDa and C-terminal amidation. Orexins are cleaved from a 130-amino acid common precursor molecule, prepro-orexin (PPO), which is synthesized mainly in neurons inside and in the area of the lateral and posterior hypothalamus. Orexin action is mediated ...

The in vitro effect of progesterone on the orexin system in porcine uterine tissues during early pregnancy

“…Current data suggest that orexins may influence reproductive function. Orexins were found to participate in the control of the hypothalamic–pituitary–ovarian axis [ 3 – 9 ]. The hormones and their receptors are also expressed locally in rat and porcine ovaries [ 3 , 7 , 10 ].…”

Expression Profile of Orexin System in Corpus Luteum of Buffalo during Estrous Cycle

“…Orexin expression has also been detected at higher level i.e. in hypothalamus (Silveyra et al, 2007) and pituitary (Smolinska et al, 2014).…”

​Localization of Orexin and its Receptor in Corpus Luteum and in vitro Effect of Orexin on Progesterone Production from Luteal Cells in Buffalo

“…Effect of orexin on P4 secretion from luteal cells of rats (Cataldi et al, 2012) and swine (Basini et al, 2018) has been recorded. However, Kaminski et al (2010) and Smolinska et al (2014) noted that the porcine ovary had the highest OXA immunoreactivity and higher OX1R expression during luteal phase, suggesting the stimulatory role of progesterone. In porcine species, OXA inhibits P 4 secretion from corpus luteum (Nitkiewicz et al, 2014) and similar effects have been observed in rat ovary (Su et al, 2008).…”