Endocrine Abstracts

The recent original data concerning interrelationships between ghrelin and feeding, action of ghrelin on ovarian functions (proliferation, apoptosis, secretory activity, response to gonadotropins, oocyte maturation) and intracellular mechanisms of its action in different species (rabbit, pig, human, chicken) are reviewed. It was shown, that ghrelin can control proliferation, apoptosis, suppress release of ovarian hormones and inhibit response of ovarian cells to gonadotropin, leptin and IGF1 treatment, but not oocyte maturation in vivo and in vitro. Comparison of different analogues and molecular fragments of ghrelin demonstrates the importance of 1–5 residues in biological activity of ghrelin. Action of pharmacological blockers of protein kinases and of cell transfection with gene constructs for transcription factors demonstrated, that ghrelin effects on ovarian cells are mediated by protein kinases A, MAP kinase, CDC2 kinase and transcription factors CREB, p53 and STAT-1. Malnutrition affects action of ghrelin on ovarian cells, whilst ghrelin administration can mimic and promote effect of food restriction on ovarian cells both in vivo and in vitro. The species-specific differences in ghrelin action are discussed.

The present data suggest that ghrelin plays an important role in control of ovarian functions in mammals and birds. It is proposed, that food restriction can control reproductive functions via stimulation of ghrelin production, which in turn, through protein kinases and transcription factors, can affect ovarian cell proliferation, apoptosis, secretory activity and response to gonadotropins and other hormonal stimulators.