Postnatal Developmental Localization of Vaspin/GRP78 in the Mouse Pituitary and its Evidence in Gonadotrophin Secretion.

Adipokine, vaspin, and its receptor GRP78 play an important role in reproductive and metabolic functions. Both proteins are expressed in reproductive tissues like the testis, ovary, and also in the hypothalamus. Our recent study has reported its postnatal localization in the testis, suggesting its involvement in the local reproductive role in pubertal males. This study investigated the postnatal localization of vaspin and GRP78 at different developmental stages of the pituitary. The study includes in vivo 35-day exogenous vaspin treatment in adult male mice (0.1 µg/kg and 1 µg/kg) and whole pituitary explant cultured with vaspin, GnRH agonist, and HA15 (GRP78 inhibitor, 12 µM) in vitro. Both vaspin and GRP78 showed strong immunostaining at PND65, and both were shown to co-express within the anterior pituitary. The exogenous vaspin treatment significantly increases the circulating LH, FSH, GnRH, and testosterone levels at higher doses, along with increased AR expression. Also, the hypothalamic Gnrh1 expression increased in both doses of vaspin. In vitro vaspin treatment increased the basal secretion of LH and FSH from the whole pituitary. The study provides the first suggestive evidence on vaspin-mediated gonadotrophin secretion. Moreover, GRP78 inhibition using HA15 decreased mRNA expression of Lhβ and Fshβ in the pituitary. Their expression was increased after co-treatment with vaspin, suggesting the involvement of GRP78-mediated action in pituitary gonadotrophin secretion. Furthermore, the study has also reported the co-localization of LH and FSH with vaspin and GRP78.