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Title: ATTENUATION BY LEPTIN OF THE EFFECTS OF FASTING ON OVARIAN FUNCTION IN HENS (GALLUS DOMESTICUS)

Author
item PACZOSKA-ELIASIEWICZ, H - U OF AGRIC, POLAND
item GERTLER, A - HEBREW U OF JERUSALEM
item PROSZKOWIEC, M - U OF AGRIC, POLAND
item Proudman, John
item HRABIA, A - U OF AGRIC, POLAND
item SECHMAN, A - U OF AGRIC, POLAND
item MIKA, M - U OF AGRIC, POLAND
item CASSY, S - INRA, FRANCE
item RAVER, N - HEBREW U OF JERUSALEM
item RZASA, J - U OF AGRIC, POLAND

Submitted to: Reproduction
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/3/2003
Publication Date: 12/12/2003
Citation: Paczoska-Eliasiewicz, H.E., Gertler, A., Proszkowiec, M., Proudman, J.A., Hrabia, A., Sechman, A., Mika, M., Cassy, S., Raver, N., Rzasa, J. 2003. Attenuation by leptin of the effects of fasting on ovarian function in hens (gallus domesticus). Reproduction. 126:739-751.

Interpretive Summary: An animal must have adequate nutrition in order to maintain reproduction. In commercial poultry production, withdrawal of feed is used to terminate the reproductive cycle and rejuvenate the hen in preparation for another reproductive season. A similar process often occurs in wild birds with cyclic changes in food supply. Leptin is a hormone that has been thought to function in obesity, but recent studies have suggested that it might also be a ¿starvation hormone¿ that functions when there is an energy deficit. This study was designed to determine whether the administration of leptin to laying chickens might influence the reproductive system during periods of undernutrition. The results showed that injection of leptin during fasting delayed the cessation of egg laying and attenuated the regression of follicles on the ovary. This effect was related to an alteration in steroid hormone production by the ovary and an inhibition of fasting-induced apoptosis, or programmed cell death. Leptin given during fasting also tended to aid in the early resumption of egg lay after fasting, but administration of leptin during refeeding delayed recovery of ovarian function. Leptin receptor messenger RNA was found in the hypothalamus, the pituitary, and in the stroma and follicles of the ovary. This work demonstrates that leptin mediates adaptation to starvation, perhaps by a direct peripheral effect on the ovary. These results will be used by scientists to better understand interrelationships between the nutritional state of the animal and reproduction.

Technical Abstract: To assess the role of leptin in avian ovarian function, recombinant chicken leptin was injected to fasted 34-week old laying hens. In the first experiment, the hens (n=60) were divided into 3 groups: fed ad libitum, fasted and fasted + leptin. Hens were fasted for five days, and those injected with leptin received (ip) 250 ug/kg b.wt. twice daily. In the second experiment, laying hens (n=72) were divided into 4 groups: fed ad libitum, fasted and fasted + leptin given only during fasting (5 days) or during both fasting and 5 days of refeeding (10 days). LH was measured in blood plasma and the ovarian steroids, progesterone and estradiol were measured in blood plasma and the ovary by RIA methods. Apoptosis was examined in the walls of the three largest yellow hierarchical follicles (F3-F1; F38-12 mm), and the granulosa layer of F3 follicle. The expression in the granulosa layer of F2 and F1 follicles was barely detectable. This was in contrast to a much higher level of expression maintained in the theca layer of F3-F1 follicles. The present results demonstrate that, in chickens, leptin mediates adaptation to starvation due to attenuation of follicular apoptosis. The presence of leptin receptors in the ovary suggests the possibility of a direct peripheral effect of the hormone.