Molecular genetic and biochemical evaluation of ghrelin hormone as a novel signal of gonadal function in adult male rats

ABSTRACT

It is well known that reproductive function is regulated by the interplay of the hypothalamus, pituitary and gonads, which form the so called reproductive axis. A number of factors primarily involved in the control of energy balance and metabolism have been proven as putative modulators of the gonadal axis, thus providing the basis for the link between energy homeostasis and fertility. Ghrelin is a 28 amino acid peptide. It is predominantly produced by the endocrine X/ A- like cells of the stomach submucosa and mobilized by food deprivation. Ghrelin concentrations were observed to change with fasting and refeeding in mammals. The potential reproductive role of ghrelin has received attention recently. The Objective of this work is to study the effect of chronic food restriction on ghrelin level in adult male rats and it's relation to reproductive hormones. The present study was carried out on 32 adult male Sprague Dawley rats divided into 4 groups Group I [control group] comprised 8 rats fed ad libitum for 30 days, Group II, III and IV [food-restricted groups for 10, 20 and 30 days respectively] each consisted of 8 rats fed 50% of ad libitum intake determined by the amount of food consumed by the control group. Mean body weight of food restricted rats was observed to decrease during the period of the experiment. Food restriction produced significant increase of serum ghrelin with significant decrease of both gastric and hypothalamic ghrelin accompanied with significant increase in its gene expression in stomach and hypothalamus. Testosterone, follicle- stimulating hormone [FSH] and luteinizing hormone [LH] levels showed significant decrease correlated with down- regulation of gonadotropins, aromatase and kisspeptin [Kissl] genes in food restricted rats compared with control group. Ghrelin could be one of the hormones responsible for the suppression of male reproductive axis in case of negative energy balance. Thus, ghrelin could provide a link between energy homeostasis and reproductive capacity in adult male rats