Abstract
BackgroundIn mammals, leptin is an attractive candidate for mediating the metabolic signal and the reproductive function via the specific receptor in hypothalamus. However, till now, the role of leptin on reproduction in birds is less well established. This experiment was conducted to elucidate the role of leptin on the onset of reproduction in bird, as a first step, to detect the changes of peripheral leptin and leptin receptor mRNA expression in hypothalamus between mature and immature hens at the same age. 120 ISA brown pullets at D60 were allocated randomly into two groups, long light (LL) group being raised under artificial light regimes with incrementally increased light phase (from 8 L:16D to 14 L:12D) and short light (SL) group raised on consistent light (8 L:16D) for 12 wk.ResultsThe results showed that pullets in LL group reached sexual maturation 15 d earlier than those in SL group. Serum E2 showed a significant increase with age, but no difference was observed between two groups. Serum leptin concentration decreased significantly from D112 to D136 in LL, and was markedly higher in LL group than that in SL at D112, while there was no significant difference between two groups at D136. Leptin receptor and GnRH-I mRNA expression in hypothalamus were significantly increased with age, yet there was no significant difference between SL and LL chickens at the same age. The expression of FSH-β and LH-β mRNA in pituitary was increased with age but did not show significant difference between LL and SL group. GnRH-I mRNA expression was very rich in pineal gland, and decreased from D112 to D136 in LL but not in SL group, and there was no difference between two groups at the same age.ConclusionsThese results indicate that the earlier sexual maturation in hens induced by long-light regime is not accompanied with an increase in serum leptin or leptin receptor gene expression in hypothalamus, or genes expression in HPG axis.
Highlights
In mammals, leptin is an attractive candidate for mediating the metabolic signal and the reproductive function via the specific receptor in hypothalamus
These results indicate that the earlier sexual maturation in hens induced by long-light regime is not accompanied with an increase in serum leptin or leptin receptor gene expression in hypothalamus, or genes expression in HPG axis
Comparison of body weights, ovary weights, the ratio of ovary weight to body weight, E2 and leptin in serum between long light (LL) and short light (SL) hens As shown in Tables 2 and 3, there was no significant difference of body weight, ovary weight and the ratio of ovary weight to body weight at D112 between LL and SL hens (P>0.05, n = 20), at D136, these indexes were statistically higher in LL group than that in SL (P
Summary
Leptin is an attractive candidate for mediating the metabolic signal and the reproductive function via the specific receptor in hypothalamus. Till the role of leptin on reproduction in birds is less well established This experiment was conducted to elucidate the role of leptin on the onset of reproduction in bird, as a first step, to detect the changes of peripheral leptin and leptin receptor mRNA expression in hypothalamus between mature and immature hens at the same age. In order to answer this question, as the first step, the measurements of circulating leptin concentration and central leptin receptor mRNA expression, as well as GnRH-I gene expression in the hypothalamus and pineal gland between mature and immature birds at the same age was detected in this study
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