Food deprivation stimulates the luteolytic capacity in the gilt.

The aims of this study were to study the effects of fasting on progesterone (P4) production in the pig and to verify whether fasting influences luteal expression of PGF(2alpha) receptor (FPr) and prostaglandin secretion. Superovulated prepubertal gilts were used; half of them were fasted for 72h starting on day 2 (F2) or 9 (F9) of the induced estrous cycle, respectively, while two groups (C2 and C9) served as respective controls. Plasma P4 and PGFM concentrations were determined by RIA while FPr mRNA expression in CLs collected at the end of fasting period was measured by real-time PCR. In experiment 1, plasma P4 concentrations in fasted gilts were significantly (P<0.01) higher than in controls starting from day 3 (F2; n=6) and 10 (F9; n=6). FPr mRNA expression was similar in F2 and C2 (n=6) CLs while it was significantly (P<0.05) higher in F9 than in C9 (n=6) CLs. In experiment 2, cloprostenol administered on day 12 significantly (P<0.05) increased FPr mRNA expression in CLs from both F9 (n=6) and C9 (n=6) gilts. At the time of cloprostenol injection PGFM levels were significantly higher (P<0.05) in the fasted group and cloprostenol-induced luteolysis in fasted but not in normally fed gilts. Results from this study indicate that fasting in prepubertal gilts induced to ovulate stimulates luteal P4 and PGFM production as well as FPr mRNA expression, thus increasing luteolytic susceptibility.

Ghrelin: central and peripheral effects of a novel peptydil hormone.

Ghrelin is a peptydil hormone that has recently been discovered through an unusual reverse pharmacology pathway. Ghrelin is produced mainly in the stomach, but its expression has also been demonstrated in many other organs such as pituitary, hypothalamus, bowel, kidney, heart, pancreas, testis. It is active on the central nervous system, where it is involved in the regulation of GH secretion, mainly through a GHRH-independent mechanism and directly at the pituitary level. Furthermore, ghrelin controls energy balance, enhancing fat mass deposition and food intake through the activation of the hypothalamic nuclei and the promotion of NPY (neuropeptide Y) and AGRP (Agouti related protein) expression; since it stimulates weight gain, ghrelin is considered a possible important factor in the etiology of obesity. Besides these main actions, ghrelin is active in the cardiovascular, reproductive and endocrine systems, and displays antineoplastic activity. Even though most studies have been conducted in humans and rats, there is increasing interest in the role of ghrelin in domestic species. We have integrated the first studies on ghrelin action with recent data on its involvement in modulating several central and peripheral activities.