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    • ISRIB br Materials and Methods br Results br

    2024-01-12


    Materials and Methods
    Results
    Discussion Voluminous literature is available describing the regulation of ISRIB homeostasis by central and peripheral mechanisms in poultry [35,36]. However, the neuroendocrine mechanism(s) of photoperiod induced hypothalamic regulation of food intake and energy homeostasis in quail of different photoperiodic phenotypes seems to be unelucidated still.Hence, in this study, we have monitored the expression of hypothalamic food-intake and energy balance regulatory neuropeptides, hormone receptors/proteins in PS SR, PR and SR quail. Significantly increased expression of NPY and AgRP along with the decreased CART and POMC in the hypothalamus of PS and SR quail hence, further supports the increased food intake and body weight, documented in these quail phenotypes. On the other hand, opposite findings in PR and SS quail clearly explains the decreased food intake and body weight. PS and SR quail hypothalamus showed significantly increased GnRH immunoreactivity which decreased significantly in the hypothalamus of PR and SS quail [21].It is well-documented that direct inputs from NPY and POMC neurons influence the GnRH neuron activity [37]. NPY also modulates the pituitary LH synthesis and release, possibly by affecting the sensitivity of the pituitary gland to LHRH [38]. Fraley and Kuenzel [39] reported that exogenous NPY injection can advance the sexual maturity in hens. In rodents, NPY (in median eminence) significantly stimulates the GnRH release [40], and intracerebroventricular (icv) injection with NPY into the 3rd ventricle induced precocious puberty accompanied with elevated LH levels in peripubertal female rats [41]. Tonic inhibition of hypothalamic GnRH secretion is mediated through β-endorphin action in domestic hens [13]. The significantly increased expression of hypothalamic IR in areas surrounding 3rd ventricle, IN and ME as well as serum testosterone levels [21] of photosensitive and scotorefractory quail further suggest the testosterone primed photo-sexual responses as increased testosterone stimulates the medial basal hypothalamus (MBH) IR expression and promotes/increases food intake and body weight [18,42]. The increased MBH IR expression may also stimulate the GnRH release [43] as well as the LH secretion from the pituitary gonadotrophs [44]. On the other hand, in photorefractory and scotosensitive quail, decreased/reduced hypothalamic IR and reduced testosterone support the reduced food intake and body weight. Adiponectin, through its receptors, acts on hypothalamic NPY and POMC neurons [33] as well as activates hypothalamic AMPK neurons by phosphorylation and increases food intake [27]. Expression of adiponectin receptors in the chicken hypothalamus, pituitary and gonads (testis and ovary) suggests that adiponectin may have potential role in regulating the hypothalamic GnRH-GnIH system, pituitary hormone secretion and gonadal functions [45]. Hypothalamic AMPK-pAMPK actively participates in avian energy homeostasis [46]. Proszkowiec-Weglarz et al. demonstrated the tissue specific expressional variations in AMPK subunits and showed the involvement of hypothalamic AMPK in regulating food intake and energy homeostasis. Their experimental findings also showed the existence of a functional AMPK pathway in the chicken similar in mammals [47]. Song et al. also demonstrated the potential role of AMPK in balancing the energy homeostasis in chickens [48,49]. Increased AMPK immunoreactivity was reported in the chicken arcuate/infundibular nucleus and parallel coupled increase in the AGRP mRNA and phosphorylated AMPKα was also documented in 48 h food deprived chickens [47,48]. Broiler chicks, food deprived for 24 h, showed increased expression of the different AMPK subunit mRNAs along with increased AGRP and decreased POMC mRNAs, respectively [50]. It is also documented that domestic broiler chicks fed with the AMPK inhibitor α-lipoic acid (α-LPA), showed decreased hypothalamic AMPKα1 mRNA along with decreased food intake [51]. It is interesting to note that in the hypothalamic areas of photosensitive and scotorefractory quail where we detected increased expression of phosphorylated AMPK, along with increased orexigenic peptides: NPY/AgRP and decreased anorexigenic peptides: CART/POMC which may stimulate the appetite regulation and energy expenditure. While photorefractory and scotosensitive quail showed opposite expression pattern for these peptides/kinases in the same hypothalamic areas. Hence, it can be concluded that food-intake regulatory neuropeptides, adiponectin and AMPK play potential role in energy homeostasis at hypothalamic level in quail. The expression of neuropeptides and the regulatory mechanisms of energy sensing at hypothalamic level showed similarity in avian and mammalian arcuate nucleus [49].