REDUCING COST OF EFFICIENT BEEF PRODUCTION
Location: Range and Livestock Research
Title: Fasting lowers gastrin-releasing peptide and Fsh mRNA in the ovine anterior pituitary gland
Submitted to: Western Section of Animal Science Proceedings
Publication Type: Proceedings
Publication Acceptance Date: April 8, 2009
Publication Date: June 15, 2009
Citation: Fuller, A.M., Austin, K.J., Roberts, A.J., Moss, G.E., Alexander, B.M. Fasting lowers gastrin-releasing peptide and Fsh mRNA in the ovine anterior pituitary gland. Western Section of Animal Science Proceedings 60:277-279.
Interpretive Summary: Limited nutrition can have adverse effects on reproduction. However, the mechanisms mediating these effects are not well established. The objective of this study was to determine effects of fasting during the luteal phase of the estrous cycle on gene expression in the anterior pituitary gland during the subsequent periovulatory period. Two genes (GRP and FSH) were determined to be down regulated due to fasting. While previous research has shown that nutritional restriction influences FSH, a major gene involved in regulating reproduction, this is the first study that has shown a connection between expression of GRP in the anterior pituitary and nutrition. This novel observation provides the ground work for additional studies on how GRP may be mediating nutritional influences on reproduction. A greater understanding of the mechanisms regulating nutritional influences on reproduction will facilitate the ability to more efficiently manage nutritional recourses without adversely affecting reproduction.
Estrogen receptor beta (ER-ß), LH, and FSH are important mediators of reproduction. FSH stimulates follicle recruitment and development. During anorexia, serum concentrations of FSH and LH decrease. Gastrin-releasing peptide (GRP), neuromedin B (NMB), peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1a), and thyroid-stimulating hormone (TSH) are important metabolic regulators expressed in the anterior pituitary gland. GRP stimulates release of ACTH, is associated with melanocortin in regulating food intake, and is a regulatory peptide in the female reproductive tract. In cattle, pituitary GRP expression was markedly up-regulated after resumption of estrus following parturition, indicating a connection between gene expression of GRP and reproductive function. The objective of this study was to determine effects of fasting during the luteal phase of the estrous cycle on gene expression in the anterior pituitary gland during the subsequent periovulatory period. Estrus was synchronized in mature (>3yr old) western white-faced ewes with prostaglandin F2a (PGF2a). Randomly selected ewes were fed grass hay ad libitum (control = 10) or were withheld from feed on days 7 – 11 of their estrous cycle (d1 = estrus; fasted = 10). On d12, fasted ewes were returned to feed and all ewes were treated with PGF2a (0 hrs). Pituitaries were collected 72 h after PGF. Ovaries were observed for presence of pre-ovulatory follicle or newly formed CL. Pituitaries were analyzed (n = 5 each group) from ewes that had ovulated. Fasting decreased (P < 0.05) gene expression of GRP and FSH. Differences in gene expression were not noted (P = 0.26) in mRNA levels of PGC-1a, TSH, NMB, ER-ß, or LH were detected. Mediation of metabolic effects on reproductive function may be regulated by GRP affecting expression of FSH.