Widmaier E P, Long J, Cadigan B, Gurgel S, Kunz T H
Department of Biology, Boston University, Boston, MA, USA.
Endocrine. 1997 Oct;7(2):145-50. doi: 10.1007/BF02778135.
Leptin, the product of the obese gene first identified in mice, restores fertility in obese mice, and accelerates puberty in mice. We hypothesized that leptin's putative role in reproduction may extend to pregnancy and lactation. Leptin levels were determined in Myotis lucifugus, the little brown bat, a free-ranging mammal with a seasonal breeding cycle. The present study shows that plasma levels of leptin progressively rise during pregnancy, supporting a potential role for leptin in the maintenancy of pregnancy. In contrast, leptin was significantly lower during lactation, a time when most mammals, including bats, demonstrate reduced fertility. In addition to its possible roles in reproduction, leptin appears important in regulation of energy balance. M. lucifugus spontaneously fasts for up to 16 h each day during the active season, which allowed us to test the hypothesis that acute fasting was associated with decreased leptin. Leptin was significantly lower in fasted (lactating) bats, compared to those that recently returned from nightly foraging. Although postprandial lactating bats had a significantly higher fat index than fasted bats, plasma leptin and body fat were not significantly correlated, and were only weakly correlated (r2 = 0.26) when both pregnant and lactating females were included in the analysis. Similar changes during pregnancy, lactation, and the daily feeding cycle were observed in the hypothalamic neuropeptide, corticotropin-releasing hormone (CRH), which is believed to play an important role in energy balance and reproduction. By contrast, neuropeptide Y (NPY) increased during pregnancy but did not change during fasting. These results suggest that leptin's putative role in reproduction may extend to pregnancy and lactation, and that spontaneous, acute fasting results in decreased circulating levels of leptin in M. lucifugus.
瘦素是最初在小鼠中发现的肥胖基因的产物，它能恢复肥胖小鼠的生育能力，并加速小鼠的青春期发育。我们推测瘦素在生殖方面的假定作用可能延伸至怀孕和哺乳过程。我们测定了棕蝠（一种具有季节性繁殖周期的自由放养哺乳动物）体内的瘦素水平。本研究表明，在怀孕过程中，瘦素的血浆水平逐渐升高，这支持了瘦素在维持妊娠方面可能发挥的作用。相比之下，在哺乳期间瘦素水平显著降低，而在这个时期，包括蝙蝠在内的大多数哺乳动物的生育能力都会下降。除了在生殖方面可能发挥的作用外，瘦素在能量平衡的调节中似乎也很重要。在活跃季节，棕蝠每天会自发禁食长达16小时，这使我们能够检验急性禁食与瘦素水平降低相关的假设。与那些刚结束夜间觅食归来的蝙蝠相比，禁食（哺乳）蝙蝠体内的瘦素水平显著更低。尽管餐后哺乳蝙蝠的脂肪指数明显高于禁食蝙蝠，但血浆瘦素与体脂之间并无显著相关性，当将怀孕和哺乳的雌性蝙蝠都纳入分析时，二者仅呈现出微弱的相关性（r2 = 0.26）。在下丘脑神经肽促肾上腺皮质激素释放激素（CRH）中也观察到了在怀孕、哺乳和每日进食周期中的类似变化，CRH被认为在能量平衡和生殖中发挥着重要作用。相比之下，神经肽Y（NPY）在怀孕期间增加，但在禁食期间没有变化。这些结果表明，瘦素在生殖方面的假定作用可能延伸至怀孕和哺乳过程，并且在棕蝠中，自发的急性禁食会导致循环中的瘦素水平下降。
