The Role of Apelin in the Functioning of the Reproductive System

Abstract

Adipokine apelin through the apelin receptors activates a wide range of signaling cascades in the target cells and controls their growth, differentiation, apoptosis, and energy metabolism. In the recent years, the evidence has been obtained that all components of the hypothalamic-pituitary-gonad axis, in which apelin and its receptor are expressed, are targets of apelin. In the hypothalamus, apelin modulates the activity of the melanocortin and ghrelin systems and indirectly affects the production of gonadoliberin. In the ovaries, it controls the growth and maturation of the follicles, stimulates the angiogenesis, and affects the basal and stimulated by the other factors steroidogenic activity in follicular cells. The changes in the apelin signaling system are closely associated with dysfunctions of the female reproductive system, such as polycystic ovary syndrome, endometriosis, and cancer. Information on the regulation of the male reproductive system by apelin is limited to animal studies showing the effect of apelin on the hypothalamic components of the gonad axis. The participation of apelin in the regulation of the reproductive system opens up the broad opportunities for the development of new approaches for the correction of abnormalities in this system and for the treatment of infertility.