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Ahima, R. S., Prabakaran, D., Mantzoros, C., Qu, D., Lowell, B., Maratos-Flier, E., Flier, J. S. (1996) Role of leptin in the neuroendocrine response to fasting. Nature (Lond.) 382 , 250

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Leptin (L) is recognised as an important regulator of puberty and a factor which controls reproduction. Whole pig ovarian follicles were incubated with different doses of leptin (2, 20 and 200 ng/ml) added alone or in combination with 100 ng/ml of GH or 50 ng/ml of IGF-I. The expression of the functional long form leptin receptor (Ob-Rb) mRNA was examined by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) in follicular cells cultured with GH or IGF-I. Both GH and IGF-I increased leptin receptor expression in prepubertal pig ovaries. In separate experiments, the action of leptin on ovarian follicular steroidogenesis and cell apoptosis was examined. After 24 h of incubation with leptin alone or in combination with GH or IGF-I, oestradiol (E2) levels were determined in the culture medium while follicular tissue was used for the estimation of caspase-3 activity. Leptin increased E2 secretion and significantly diminished caspase-3 activity at all doses used. Both GH and IGF-I stimulated oestradiol secretion and decreased caspase-3 activity. No differences were demonstrable in oestradiol secretion and caspase-3 activity between cells treated with GH plus leptin and GH alone or cells treated with IGF-I plus leptin as compared to cultures treated with GH or IGF-I alone. However, GH diminished leptin-stimulated oestradiol secretion while IGF-I was without effect on it. Both GH and IGF-I reversed the anti-apoptotic action of leptin. In conclusion, we infer that (1) leptin directly affects ovarian function in prepubertal animals by its action on oestradiol secretion and cell apoptosis, (2) GH and IGF-I modulate the action of leptin, and (3) at least in part, the direct effect of GH/IGF-I on leptin production is due to an action on leptin receptor expression.

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Alonso-Vale, M. I. C., Andreotti, S., Peres, S. B., Anhe, G. F., Borges-Silva, C. N., Neto, J. C., Lima, F. B. (2005) Melatonin enhances leptin expression by rat adipocytes in the presence of insulin. Am. J. Physiol. Endocrinol. Metab. 288 , E805–E

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Yanagihara, N., Utsunomiya, K., Cheah, T. B., Hirano, H., Kajiwara, K., Hara, K., Nakamura, E., Toyohira, Y., Uezono, Y., Ueno, S. and Izumi, F. (2000): Characterization and functional role of leptin receptor in

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Acta Veterinaria Hungarica
Authors: Linda Müller, Eszter Kollár, Lajos Balogh, Zita Pöstényi, Teréz Márián, Ildikó Garai, László Balkay, György Trencsényi and Julianna Thuróczy

Ceddia, R. B., Koistinen, H. A., Zierath, J. R. and Sweeney, G. (2002): Analysis of paradoxical observations on the association between leptin and insulin resistance. FASEB J. 16 , 1163–1176. Sweeney G

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Anim. Reprod. Sci. 41 119 129. Agarwal, S. K., Vogel, K., Weistman, S. R. and Magoffin, D. (1999): Leptin

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83 92 Shimizu H, Shimomura Y, Nakanishi Y, Futawatari T, Ohtani K, Sato N et al.: Estrogen increase in vivo leptin production in rats and human subjects. J. Endocrinol. 154

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a source of leptin. Nature 394 , 790–793. Lewin M. J. The stomach is a source of leptin Nature 1998

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Acta Veterinaria Hungarica
Authors: Margit Kulcsár, Gabriella Dankó, H. G. I. Magdy, J. Reiczigel, T. Forgach, Angella Proháczik, Carole Delavaud, K. Magyar, Y. Chilliard, L. Solti and Gy. Huszenicza

Bonnet, M., Delavaud, C., Laud, K., Gourdou, I., Leroux, C., Djiane, J. and Chilliard, Y. (2002 a ): Mammary leptin synthesis, milk leptin and their putative physiological roles. Reprod. Nutr. Dev. 42 , 399

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Tuominen JA, Ebeling P, Laquier FW, Heiman ML, Stephens T, Koivisto VA: Serum leptin concentrations and fuel homeostasis in healthy men. Eur. J. Clin. Invest. 27, 206-211 (1997) Serum

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